CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U. S. Non-Provisional Patent Application Serial No. 15/220,307, filed July 26, 2016, entitled "Multi-Electrode Molecular Sensing Devices and Methods of Making the Same," the disclosure of which is incorporated herein by reference in its entirety.

FIELD

[0002] The present disclosure relates to nanofabrication and nanoelectronics. More particularly, the present disclosure relates to structures such as device stacks, and the fabrication of structures usable in devices for sensing and analyzing molecules, including genome sequencing and DNA sequencing.

BACKGROUND

[0003] Molecular analysis has received an increasing amount of attention in various fields such as precision medicine or nanotechnology. One example includes the analysis of molecules for sequencing genomes. The seminal work of Avery in 1946 demonstrated that DNA was the material that determined traits of an organism. The molecular structure of DNA was then first described by Watson and Crick in 1953, for which they received the 1962 Nobel Prize in Medicine. This work made it clear that the sequence of chemical letters (bases) of the DNA molecules encode the fundamental biological information. Since this discovery, there has been a concerted effort to develop means to actually experimentally measure this sequence. The first method for systematically sequencing DNA was introduced by Sanger in 1978, for which he received the 1980 Nobel Prize in Chemistry. [0004] A basic method for sequencing a genome was automated in a commercial instrument platform in the late 1980's, which ultimately enabled the sequencing of the first human genome in 2001. This was the result of a massive public and private effort taking over a decade, at a cost of billions of dollars, and relying on the output of thousands of dedicated DNA sequencing instruments. The success of this effort motivated the development of a number of "massively parallel" sequencing platforms with the goal of dramatically reducing the cost and time required to sequence a human genome. Such massively parallel sequencing platforms generally rely on processing millions to billions of sequencing reactions at the same time in highly miniaturized microfluidic formats. The first of these was invented and commercialized by Rothberg in 2005 as the 454 platform, which achieved thousand fold reductions in cost and instrument time. However, the 454 platform still required approximately a million dollars and took over a month to sequence a genome.

[0005] Further improvements in quality and accuracy of sequencing, as well as reductions in cost and time are still needed. This is especially true to make genome sequencing practical for widespread use in precision medicine, where it is desirable to sequence the genomes of millions of individuals with a clinical grade of quality.

[0006] While many DNA sequencing techniques utilize optical means with fluorescence reporters, such methods can be cumbersome, slow in detection speed, and difficult to mass produce to further reduce costs. Label-free DNA or genome sequencing approaches provide advantages of not having to use fluorescent type labeling processes and associated optical systems, especially when combined with electronic signal detection that can be achieved rapidly and in an inexpensive way.

[0007] In this regard, certain types of molecular electronic devices can detect single molecule, biomolecular analytes such as DNAs, RNAs, proteins, and nucleotides by measuring electronic signal changes when the analyte molecule is attached to a circuit. Such methods are label-free and thus avoid using complicated, bulky and expensive fluorescent type labeling apparatus.

[0008] While current molecular electronic devices can electronically measure molecules for various applications, they lack the scalability and manufacturability needed for rapidly sensing many analytes at a scale of up to millions in a practical manner. Such highly scalable methods are particularly important for DNA sequencing applications, which often need to analyze millions to billions of independent DNA molecules. In addition, the manufacture of current molecular electronic devices is generally costly due to the high level of precision needed.

SUMMARY OF THE INVENTION

[0009] In various embodiments of the present disclosure, a method of manufacturing a structure usable in a molecular sensor device is described. The method comprises: providing a substrate defining a substrate plane with a protrusion protruding from the substrate at an angle to the substrate plane; depositing a first electrode layer in an orientation along a side of the protrusion to form a first electrode sheet at the angle to the substrate plane; depositing an inner dielectric layer on the first electrode layer to form an inner dielectric sheet at the angle to the substrate plane; depositing a second electrode layer on the inner dielectric layer to form a second electrode sheet at the angle to the substrate plane, wherein the first electrode sheet and the second electrode sheet form a pair of electrode sheets spaced apart by the inner dielectric sheet between the first electrode sheet and the second electrode sheet; depositing an outer dielectric layer on the second electrode layer to form an outer dielectric sheet at an angle to the substrate plane; repeating the depositing of the first electrode layer, the inner dielectric layer, the second electrode layer, and the outer dielectric layer at least once to form spaced apart pairs of electrode sheets with an inner dielectric sheet between each electrode sheet in the pair of electrode sheets and an outer dielectric sheet between each pair of electrode sheets; planarizing the pairs of electrode sheets, the inner dielectric sheets, and the outer dielectric sheets; and removing an exposed end portion of each inner dielectric sheet to form grooves in each inner dielectric sheet descending from the planarized edge toward the substrate.

[0010] In certain examples, each inner dielectric layer is deposited with a first thickness, each outer dielectric sheet is deposited with a second thickness, and the second thickness is at least one order of magnitude greater than the first thickness.

[0011] In some aspects, the method may further comprise attaching a mechanically supportive block material adjacent a stack formed by the deposited first electrode layers, inner dielectric layers, second electrode layers, and outer dielectric layers, prior to the step of planarizing. The block material can lend support to the structure during planarization.

[0012] In various examples, the inner dielectric sheets and the outer dielectric sheets comprise different dielectric materials. In some instances, differing materials allows for selective etching of the exposed edges of the inner dielectric sheets in the presence of the exposed outer edges of the outer dielectric sheets, such as to form the grooves.

[0013] In various embodiments, the forming of the groove in each inner dielectric sheet comprises: removing portions of the inner dielectric sheet; and stopping further removal of the inner dielectric sheet based on an electrical, capacitance, or optical measurement between the pair of electrode sheets.

[0014] In some aspects, the method of manufacturing may further comprise depositing a dielectric cover layer at an angle or perpendicular to the plurality of pairs of electrode sheets opposite the substrate to define a gap exposing a portion of the spaced apart pairs of electrode sheets. Further, the method may comprise roughening an exposed edge of each electrode sheet, such as to facilitate attachment of metals or molecules onto the exposed edges.

[0015] In adapting structures for use in sensor devices, the method may further comprise connecting a plurality of lead conductors to the spaced apart pairs of electrode sheets with each lead conductor connected to a respective electrode sheet, wherein each lead conductor diverges in width as the lead conductor extends away from an edge of the electrode sheet. In certain examples, the method may further comprise depositing a gate electrode parallel to the substrate plane and perpendicular to an electrode plane defined by an electrode sheet in the spaced apart pairs of electrode sheets. Also in certain embodiments, the method may further comprise forming a plurality of channels, each channel arranged to introduce a fluid to exposed portions of at least two pairs of electrode sheets.

[0016] In other embodiments of the present disclosure, a method of manufacturing a device stack usable in a molecular sensor is disclosed. The method comprises: providing a first outer dielectric layer; depositing a first electrode layer on the first outer dielectric layer; depositing an inner dielectric layer on the first electrode layer; depositing a second electrode layer on the inner dielectric layer; and depositing a second outer dielectric layer on the second electrode layer; slicing through the stack at least once at an angle to the layers in the stack to form at least two chips from the sliced portions of the stack; and attaching the chips to a substrate so that the sliced portions of the first electrode layer and the second electrode layer form a plurality of pairs of electrode sheets at an angle to a substrate plane defined by the substrate, and so that the sliced portions of the inner dielectric layer forms a plurality of inner dielectric sheets with each inner dielectric sheet between each electrode sheet in each pair of electrode sheets. In certain aspects, forming the device stack further includes repeating the deposition of the first electrode layer, the inner dielectric layer, the second electrode layer, and the second outer dielectric layer at least once so that each chip of the plurality of chips includes multiple pairs of electrode sheets.

[0017] In various examples, the inner dielectric layer has a first thickness and the second outer dielectric layer has a second thickness at least one order of magnitude greater than the first thickness. Further, the inner dielectric layers and the outer dielectric layers may comprise different dielectric materials.

[0018] In various embodiments, the method may further comprise forming a groove located on an exposed end portion of each inner dielectric sheet. Additionally, the method may further comprise depositing a dielectric cover layer at an angle or perpendicular to the plurality of pairs of electrode sheets opposite the substrate to define a gap exposing a portion of the plurality of pairs of electrode sheets. In some examples, the method comprises roughening an exposed edge of each electrode sheet.

[0019] In various aspects, the method further comprises depositing a gate electrode parallel to the substrate plane and perpendicular to an electrode plane defined by an electrode sheet in the plurality of pairs of electrode sheets. In some examples, the method may further comprise forming a plurality of channels, each channel arranged to introduce a fluid to exposed portions of at least two pairs of electrode sheets of the plurality of pairs of electrode sheets.

[0020] In various embodiments of the present disclosure, a structure usable in a molecular sensor device is described. Such structures can be fabricated with the methods of manufacturing described herein. In various examples, a structure usable in a molecular sensor device comprises, a substrate defining a substrate plane; spaced apart pairs of electrode sheets attached on an edge of the electrode sheet to the substrate at an angle to the substrate plane; an inner dielectric sheet disposed between the electrode sheets in each pair of electrode sheets; and an outer dielectric sheet disposed between spaced apart pairs of electrode sheets, wherein an edge of each electrode sheet, inner dielectric sheet and outer dielectric sheet opposite the substrate are coplanar and substantially parallel to the substrate plane.

[0021] In various examples, each inner dielectric sheet has a first thickness, and wherein each outer dielectric sheet has a second thickness at least one order of magnitude greater than the first thickness.

[0022] In various examples, the structure comprises a groove located on an exposed end portion of each inner dielectric sheet opposite the substrate. Further in some examples, the inner dielectric sheets and the outer dielectric sheets comprise different dielectric material. For example, inner dielectric sheets comprising S1O2 may be selectively etched in the presence of outer dielectric sheets comprising AI2O ₃ , such as to form grooves in exposed end portions of the inner dielectric sheets.

[0023] In some examples, the structure may further comprise dielectric cover layers covering portions of the edges of the spaced apart pairs of electrodes opposite the substrate, the dielectric cover layers spaced apart by a gap in which a portion of the spaced apart pairs of electrodes are exposed. The gap in certain aspects may be between about 2 nm to about 40 nm in width.

[0024] In certain aspects, an exposed edge of each electrode sheet opposite the substrate may been roughened, such as to improve bonding of other metal deposits or molecules onto the exposed edges of the electrode sheets.

[0025] In various embodiments, the structure may further comprise: a plurality of lead conductors, each lead conductor of the plurality of lead conductors extending from an electrode sheet of the plurality of pairs; and a plurality of contacts, each contact of the plurality of contacts in electrical communication with a lead conductor of the plurality of lead conductors, wherein each lead conductor of the plurality of lead conductors diverges in width from an edge of the electrode sheet to the contact. The structure may also comprise a gate electrode parallel to the substrate plane and perpendicular to an electrode plane defined by an electrode sheet in the spaced apart pairs.

[0026] In various examples, the structure further comprises a plurality of channels, each channel of the plurality of channels arranged to introduce a fluid to exposed portions of at least two pairs of electrode sheets of the plurality of pairs. In some examples, the structure comprises a portion of a molecular sensor used to detect at least one of a DNA molecule, a nucleotide, an antibody molecule, and a protein molecule by measuring an electronic signal in the molecular sensor. Such a molecular sensor may be used for genome sequencing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The features and advantages of the embodiments of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the disclosure and not to limit the scope of what is claimed.

[0028] FIG. 1A is a cross section view showing fabrication of a molecular sensor by sequentially depositing tri-layer thin film device stacks using a low deposition angle and a sacrificial top layer according to an embodiment.

[0029] FIG. IB is a cross section view showing further fabrication of the molecular sensor of FIG. 1A.

[0030] FIG. 1C is a cross section view of the molecular sensor of FIGS. 1A and IB after fabrication. [0031] FIG. 2A is a cross section view showing fabrication of a molecular sensor by sequentially depositing tri-layer thin film device stacks using a low deposition angle and detachable shades according to an embodiment.

[0032] FIG. 2B is a cross section view showing further fabrication of the molecular sensor of FIG. 2A.

[0033] FIG. 2C is a cross section view of the molecular sensor of FIGS. 2A and 2B after fabrication.

[0034] FIG. 3 is a flowchart for a manufacturing process of the molecular sensor of FIG. 1C or FIG. 2C according to an embodiment utilizing low incident angle oblique deposition.

[0035] FIG. 4A is a cross section view showing fabrication of a molecular sensor by sequentially depositing tri-layer thin film device stacks using a high deposition angle according to an embodiment.

[0036] FIG. 4B is a cross section view of the molecular sensor of FIG. 4A after fabrication.

[0037] FIG. 5 is a flowchart for a manufacturing process of the molecular sensor of FIG. 4B according to an embodiment utilizing high incident angle oblique deposition.

[0038] FIG. 6 is a flowchart for an additional manufacturing process according to an embodiment.

[0039] FIG. 7A is a cross section of a molecular sensor showing the deposition of a mask line during the manufacturing process of FIG. 6.

[0040] FIG. 7B is a cross section of the molecular sensor of FIG. 7A after depositing a dielectric cover layer and removing the mask line of FIG. 7A.

[0041] FIG. 8 is a cross section of the molecular sensor of FIG. 7B illustrating the roughening of an exposed portion of electrode sheets according to an embodiment. [0042] FIG. 9 is a top view of a molecular sensor with diverging lead conductors according to an embodiment.

[0043] FIG. 10 is a top view of the molecular sensor of FIG. 9 with a gate electrode according to an embodiment.

[0044] FIG. 11 is a top view of a molecular sensor with channels for introducing a fluid to pairs of electrode sheets according to an embodiment.

[0045] FIG. 12 depicts a molecular sensor manufactured by forming a stack of layers and slicing through the stack according to an embodiment.

[0046] FIG. 13 is a flowchart for a manufacturing process of the molecular sensor of FIG. 12 according to an embodiment.

[0047] FIG. 14A is a cross section of a stack of layers during the manufacturing process of FIG. 13.

[0048] FIG. 14B illustrates the slicing of the stack of FIG. 14A to form chips during the manufacturing process of FIG. 13.

[0049] FIG. 14C is a cross section view showing the placement of a chip from FIG. 14B on a substrate during the manufacturing process of FIG. 13.

[0050] FIG. 15 illustrates the placement of multiple chips on a substrate according to an embodiment.

[0051] FIG. 16 illustrates the placement of a dielectric cover layer on the multiple chips of FIG. 15 according to an embodiment.

[0052] FIG. 17 is a top view of a molecular sensor with diverging lead conductors according to an embodiment.

[0053] FIG. 18 is a top view of a molecular sensor with channels for introducing a fluid to pairs of electrode sheets according to an embodiment. [0054] FIGS. 19A-19C illustrate embodiments of structures available by OAD and planarization steps.

[0055] FIGS. 20A and 20B provide TEM and STEM images of a structure in accordance with the present disclosure.

DETAILED DESCRIPTION

[0056] In the following detailed description, numerous specific details are set forth to provide a full understanding of the present disclosure. It will be apparent, however, to one of ordinary skill in the art that the various embodiments disclosed may be practiced without some of these specific details. In other instances, well-known structures and techniques have not been shown in detail to avoid unnecessarily obscuring the various embodiments.

[0057] As used herein, the term "structure" refers generally to physical constructs comprising at least one of a substrate layer, an electrode layer, or a dielectric layer, in any combination, such as formed by depositing metal and/or dielectric layers onto a substrate. A "structure" herein may be a part of a molecular sensor or part of a molecular electronics component or any other device. In some instances, a "structure" herein can be converted into a working molecular sensor by disposing a biomolecule or other molecule across a pair of electrodes in a structure, amongst other processes. In some instances, a structure, e.g. comprising alternating electrode and dielectric layers on a substrate, may also be referred to as a structure usable in, or usable for, a molecular sensor.

[0058] As used herein, the term "device stack" is an embodiment of a "structure," and generally refers to a structure having multiple layers of material comprising metal and dielectric layers. In a non-limiting example, a device stack comprises a three-layer (or tri- layer) arrangement further comprising a dielectric layer sandwiched between two electrode layers. [0059] As used herein, oblique angle deposition, or "OAD," refers to the process of depositing material such as a metal at an incident angle less than 90° relative to a planar substrate receiving the deposition. Normal deposition generally refers to deposition of materials orthogonal (90°) to a substrate plane, which necessarily creates layers that are co-planar with a top surface of the substrate. OAD, on the other hand, comprises deposition onto a substrate at an angle less than 90°, (including at 0° or "horizontally"), such that vertical surfaces protruding from a substrate plane can also receive deposition of materials. The definition of OAD is extended herein to include 0° (also referred to as "horizontal" or "sideways") deposition, which can result in no material being deposited onto the top plane of a substrate sheet, but rather only deposition on the edge of the substrate facing the deposition stream, and on the surfaces of any protrusions emanating from the substrate that face the deposition stream

[0060] Low angle deposition

[0061] The cross-sectional views of FIGS. 1A to 1C illustrate embodiments of intermediate structures 100 obtained by executing various steps of the fabrication process of the present disclosure, such as by using low angle (from about 0° to about 20°) or 0° (horizontal) incident film deposition of alternating thin films and thick films, relative to a substrate plane 103. As illustrated for example in FIG. 1 A, a tri-layer thin film structure or device stack 111 may be formed by sequential deposition of a first electrode sheet 107, an inner dielectric sheet 108, and a second electrode sheet 115. The structure 100 in FIG. 1A is fabricated by deposition of a thicker outer dielectric sheet 112 and then by a repetition of the deposition of the three layers first electrode sheet 107, inner dielectric sheet 108 and second electrode sheet 115, to form multiple adjacent tri-layer device stacks 111 with thicker outer dielectric sheets 112 as separators, in accordance to a non-limiting embodiment. [0062] As shown in FIGS. 1A to 1C, structure 100 includes a supporting substrate 102 with a protrusion 104 protruding from the substrate 102 at an angle to a substrate plane

103 defined by the substrate 102. The protrusion 104 may be disposed substantially perpendicular to the substrate plane 103, or at another angle to the substrate plane 103 such as from about 90° to about 45°. In various embodiments, the protrusion 104 may appear as a block of material on the substrate 102. The supporting substrate 102 may comprise, for example, S1O2 or Si having a S1O2 coating. In the example of FIG. 1A-1 C, the protrusion

104 comprises a block that extends from the substrate 102 perpendicular to the substrate plane 103. In other implementations, the protrusion 104 may protrude from the substrate 102 at a different angle, such as for example, a 45° or 60° angle relative to the substrate plane 103.

[0063] The protrusion 104 may comprise, for example, a dielectric material such as S1O2, AI2O ₃ , or MgO. In various examples, the combination of substrate 102 and protrusion 104 can be formed by removing (e.g., ablating) a portion of a larger block of substrate material to create the step-like feature, or by attaching the protrusion 104 (e.g., a block of dielectric material) onto the substrate 102. The protrusion 104 can provide structural support for the depositing of dielectric and/or electrode layers at an angle to the substrate plane 103.

[0064] FIG. 1A illustrates an embodiment of a structure 100 resulting from thin film and thick film deposition process steps. The deposits are made onto the step-like combination of protrusion 104 and substrate 102. In this embodiment, sacrificial top and side layers 1 19 are included to enable sideways deposition of multiple tri-layer device stacks 1 11. In the example of FIG. 1 A, the deposition angle can be horizontal as shown by the large arrows on the right side of FIG. 1A, or may be within about plus or minus 20° from the horizontal plane 103. A first conductive electrode sheet 107 deposited by the OAD process comprises a thin film deposited at a sideways or low deposition angle. The process is continued by deposition of an inner dielectric sheet 108, and then a second electrode sheet 115. This process can be repeated to form many device stacks 1 11 , each including a pairs of electrode sheets 106 with an inner dielectric sheet 108 between the pair of electrode sheets 106, with each device stack 1 11 separated by a thicker outer dielectric sheet 112 deposited between repeating cycles of deposition of the device stack layers.

[0065] A thicker dielectric sheet 1 12 is deposited between each tri-layer device stack. FIGS. 1A-1 C, along with all other drawing figures herein depicting structures, should not be interpreted literally as to the sizes of the various elements. For example, the relative size shown for the tri-layer device stacks 11 1 and separator outer dielectric sheets 1 12 may be somewhat exaggerated to better illustrate the features of the tri-layer device stacks 1 1 1. In this regard, the cross sectional width of the tri-layer device stacks in some embodiments may be less than about 50 nm.

[0066] FIG. IB illustrates an embodiment of a structure 100 further comprising a mechanically supportive block material 123 added to facilitate polishing of the material from the top and planarizing the structure along plane 117. Block material 123 can comprise, for example, an oxide or a precursor of an oxide (e.g., hydrogen silsesquioxane, or "HSQ").

[0067] FIG. 1C shows a cross-section of an embodiment of a structure 100. Such a structure 100 may be obtained by planarizing the structure in FIG. IB across plane 1 17. The planarization across plane 1 17 in FIG. B may be at a level higher or lower than the intersection of the protrusion 104 and the sacrificial material 1 19. In various examples, the planarization across plane 117 removes sacrificial material 119 in its entirety. [0068] FIG. 2A demonstrates use of detachable top and side shades 121 to help enable sideways or low angle deposition of multiple tri-layer thin film device stacks 111. These shades 121 act as barriers or shields to the incident deposition stream, and are layered on their ends by the successive depositions as illustrated. In various examples, a shade 121 replaces the need for a sacrificial material 119 (see FIGS. 1A and IB). As shown in FIG. 2B, a portion of the protrusion 104 is effectively blocked from low angle or horizontal OAD by the shade 121. The structure 100 is produced by layering a first conductive electrode sheet 107 as a thin film by low deposition angle OAD, followed by deposition of an inner dielectric thin film sheet 108, and then a second electrode sheet 115. This process is repeated to form multiple device stacks 111, with a thicker dielectric separator sheet 112 deposited between adjacent tri-layer stacks 111.

[0069] FIG. 2B illustrates an embodiment of a structure 100 after the addition of a mechanically supportive block material 123, which can comprise an oxide or precursor of an oxide (e.g., HSQ), to the structure of FIG. 2A after removal of the shades 121. As illustrated, the supportive block material 123 may be attached to the substrate 102 and may occupy the regions above the substrate that were previously shielded from deposition of the various layers. In some examples, the supportive block material 123 may be disposed in the region under the multiple device stacks and the region adjacent to the last deposited layer. The supportive block material 123 can facilitate planarization and polishing of the structure from the top, across plane 117. FIG. 2C illustrates a cross-sectional view of a structure 100 obtained by planarizing the structure of FIG. 2B along plane 117.

[0070] The structures 100 usable in molecular sensors, such as shown in the examples of FIGS. 1C and 2C, utilize a unique geometry of electrodes in a vertically aligned or near vertically aligned tri-layer sheet configuration. One notable difference between the structure of FIG. 1C and the structure of FIG. 2C is that in the structure of FIG. 1C, the electrode layers and inner and outer dielectric layers extend all the way to the substrate 102. In structure 100 of FIG. 2C, they do not because of the intervening block material 123.

[0071] When used in various sensors, the sheet geometry of the electrically conductive electrodes as shown in these structures ordinarily allows for a low electrical resistance of the sensor electrodes, enabling high signal-to-noise ratios, with accurate dimensional control and ease of scale-up fabrication at a relatively low cost. This configuration can facilitate the packing of high-density device arrays into relatively small device surface areas, allowing the manufacture of a compact multiple device assembly. The sequential deposition of a first conductor layer, an inner dielectric layer, and a second conductor layer can be repeated many times, depositing the outer dielectric layer onto each second conductor layer prior to the next repeat of the device stack layers. In this regard, this sequence of depositions may be repeated from 2 to 10,000 times or more to produce an array of at least 2 to tens of thousands of parallel devices.

[0072] A tri -layer device stack 1 11 in various embodiments of the structures herein can include highly electrically conductive metallic electrode sheets in a vertical or near- vertical configuration. Other implementations can include a tilted angle orientation of the layers of a device stack of up to about 60° from vertical. In some examples, layers of a device stack are tilted from vertical at no more than about 20°. Each pair of electrode sheets 106 is separated in the device stack 11 1 by a dielectric sheet layer material 108 that can be selected from oxides (e.g., SiC , AI2O3, MgO, CaO, refractory oxide, rare earth oxide, or a mixture of oxides), nitrides (e.g., A1N, S1 ₃ N4, refractory nitride, rare earth nitride or a mixture of nitrides), fluoride, oxyfluoride, or oxynitride.

[0073] The material for the electrode sheets 107 and 115 in each device stack 11 1 may be selected from high-conductivity metals or alloys, including, but not limited to, Au, Pt, Pd, Ag, Os, Ir, Rh, Ru and their alloys. The dimensions of the exposed electrode sheet edges on the structure top surface after planarization can have a thickness (or width) of, for example, from about 1 to about 100 nm. In various embodiments, the electrode sheets 107 and 115 (e.g. in FIGS. 1A and 2A) can be deposited to a thickness of from about 1 to about 40 nm, or from about 5 to about 15 nm, with the height of a vertical or near-vertical electrode sheet being at least about 100 μηι tall (as measured from the substrate 102 top surface up to the level of planarization). In other examples, the height of the electrode sheets are at least about 1 ,000 μηι tall, or at least about 10,000 μηι tall. Accordingly, the aspect ratio for an electrode sheet, (in terms of height to thickness), is at least about 10,000 or at least about 100,000. With this aspect ratio, an electrode sheet herein, standing vertically or nearly vertical with respect to the substrate plane 103, will necessarily have a top edge that is opposite the substrate 102. When a vertically disposed electrode sheet is planarized across a plane substantially parallel to the substrate plane 103, the top edge of the electrode sheet will necessarily be substantially parallel to the substrate plane 103. After planarization, exposed top edges of the electrode sheets, the inner dielectric sheets, and the outer dielectric sheet, appear as parallel strips on the planarized top surface of the structure.

[0074] In other embodiments, a thin adhesion promoting layer may be deposited at the interface between the electrode sheets and the inner dielectric sheet to improve the adhesion at the interface. For example, an about 1 to about 5 nm thick film may be deposited at the interface, wherein the film may comprise a material such as Ti, Cr, Al, Zr, Mo, Nb, Ta, or Hf

[0075] The thickness of the exposed end portion of an inner dielectric sheet 108 deposited between the two electrode sheets on the structure's top surface after planarization may be from about 1 to about 40 nm. In some examples, the thickness of the exposed end portion of the inner dielectric layer after planarization may be from about 5 to about 15 nm. In some embodiments, the thickness of the inner dielectric sheets 108 may be less than about 10 nm. The height of a vertical or near-vertical dielectric sheet 108 may be at least about 100 μηι tall. In other examples, the height is at least about 1 ,000 μηι tall or at least about 10,000 μηι tall. Accordingly, the aspect ratio of the inner dielectric layer sheet, (in terms of height to thickness), is at least about 10,000 or at least about 100,000.

[0076] The dimension of each outer dielectric layer 1 12 separating neighboring tri- layer device stacks 11 1, may have a width of at least about 500 to at least about 20,000 nm, or about one order of magnitude thicker than the thickness of any one inner dielectric sheet separating first and second electrodes in a device stack. In various examples, a thickness for an outer dielectric layer 1 12 can be, for example, in the range of from about 500 to about 5,000 nm. A separation between adjacent tri-layer device stacks 1 11 of about 500 to about 5,000 nm reduces electrical, inductive, capacitive, or other interferences.

[0077] Various embodiments of the structure 100 can be fabricated using a low incident angle OAD of layers, such as at a deposition angle of 0° to less than about 20° from the substrate plane (see substrate plane 103 in FIG. 1A for example). In the example process of FIG. 3, a low incident angle OAD is used with one or more sacrificial layers (e.g., sacrificial layers 119 in FIG. 1A) and/or detachable shades (e.g., detachable shades 121 in FIG. 2A) to help prevent deposition of the electrode and dielectric layers on certain surfaces. The sacrificial layers and/or detachable shades are later removed after the electrode and dielectric sheets have been formed at the desired angle to the substrate plane 103.

[0078] In the example of FIG. 1A, a series of film depositions are performed at a deposition angle of 0° to less than about 20° from the substrate plane 103. The sacrificial layer 119 on a surface of the protrusion 104 opposite the substrate 102 is disposable upon planarization. In some examples, the sacrificial layer 1 19 can include a slight extension off an edge of the protrusion 104 to help prevent deposition above the top surface of the protrusion 104.

[0079] FIG. 5, discussed below, provides an alternative embodiment of a process that includes performing the multilayer deposition at a higher oblique incident angle prior to planarization. The higher oblique incident angle for multilayer OAD can be performed, for example, at any angle in the range of about 20° to about 70° from the substrate plane 103, such as between about 30° and about 60°. Utilizing OAD without a sacrificial layer as in the process of FIG. 5, the surface of the protrusion 104 opposite the substrate 102 is also covered with multilayer thin films, (e.g., as illustrated in FIG. 4A). Nonetheless, a planarization polishing process removes these film depositions on the surface of the protrusion 104 so as to achieve a structure as in FIG. 4B. In some instances, the very top layer of the protrusion 104 is sacrificed in the planarization that removes all of the layers previously deposited on the protrusion 104.

[0080] FIG. 3 illustrates a flowchart of an exemplary fabrication process according to the present disclosure. As illustrated in the flowchart of FIG. 3, step 302 comprises providing a substrate (such as the substrate 102 depicted throughout the various embodiments). As discussed, a substrate 102 further comprises a major surface that defines substrate plane 103. The substrate plane can be defined by being parallel with a major surface of the substrate, such as a top or bottom surface used for supporting dielectric and/or electrode layers.

[0081] In step 304, a protrusion (e.g., a protrusion 104 depicted throughout the various embodiments) is attached to the substrate 102, or in alternative embodiments, the protrusion is formed by removing one or more portions of a larger substrate, generating a cut-out "step" in an initially thicker supporting substrate. In various examples, a dielectric material in a block or other shape may be attached to the substrate to form the protrusion at the desired angle to the substrate plane. As noted above, the protrusion (regardless if attached material or formed by cutting out a step in a thicker substrate) protrudes from the substrate plane at an angle, such as about 90°.

[0082] With continued reference to FIG. 3, step 305 comprises the placement of one or more sacrificial layers and/or detachable shades on a side of a structure targeted for OAD, (e.g., detachable shades 121 in FIG. 2A) and/or on a surface of the protrusion opposite the substrate (e.g., the top sacrificial layer 119 in FIG. 1A). As noted above, the sacrificial layer may extend beyond an edge of the protrusion 104. The sacrificial layer can include, for example, a physically removable plate, or a dissolvable polymer layer, such as acetone- dissolvable (poly)methyl methacrylate (PMMA), common in lift-off processing in semiconductor fabrication. The detachable shade can include, for example, a detachable metallic, ceramic, or polymer material.

[0083] In step 306, a first electrode layer is deposited on the substrate. In various embodiments, at least a portion of the first electrode layer is deposited against an exposed side of a protrusion from the substrate, thereby resulting in a first electrode sheet (e.g., first electrode sheet 107 in FIG. 1 A or in FIG. 2A) at an angle to the substrate plane equaling the angle between the protrusion and the substrate. In other implementations, a dielectric layer, (e.g., an outer dielectric layer as described herein) may be deposited against the protrusion first, before deposition of the first electrode layer and subsequent layers.

[0084] In the embodiment depicted in the flowchart of FIG. 3, an inner dielectric layer is deposited in step 308 on the first electrode layer previously deposited in step 306. As shown in the examples of FIGS. 1A and 2A, at least a portion of the inner dielectric layer is deposited against the protrusion 104 to form the inner dielectric sheet 108 at the same orientation of the protrusion to the substrate plane 103. As with the first electrode layer deposited in step 306, OAD can be used to deposit the inner dielectric layer at an angle to the substrate plane. Complementary metal-oxide semiconductor (CMOS) processes, such as OAD, can ordinarily allow for the inner dielectric layer to be deposited with an accurate and repeatable thickness.

[0085] In some implementations, a thin adhesion enhancing layer may be deposited on the first electrode layer before and/or after depositing the inner dielectric layer to improve adhesion of the layers. In various examples, an about 1 to about 5 nm thick film material is deposited at the interface using a material. Such film material may comprise, for example, Ti, Cr, Al, Zr. Mo, Nb, Ta, or Hf.

[0086] In step 310 of the process depicted in FIG. 3, a second electrode layer is deposited on the inner dielectric layer to form a second electrode sheet (e.g., second electrode sheet 115 in FIGS. 1A and 2A) at the same angle to the substrate plane as the prior layers, using, for example, OAD. Upon completion of step 310, a device stack is formed, which comprises a first electrode sheet and a second electrode sheet arranged as a pair of electrode sheets, with the inner dielectric sheet disposed between the pair of electrode sheets.

[0087] In step 312, an outer dielectric layer is deposited on the second electrode layer to form an outer dielectric sheet at an angle to the substrate plane. With reference to the examples in FIGS. 1A and 2A, the outer dielectric layer is deposited on the second electrode layer to form the outer dielectric sheet 1 12 at the same angle to the substrate plane 103 as per the previous layers. In some implementations, the outer dielectric layer may have a different thickness than other previously deposited outer dielectric layers if, for example, it comprises the final outer dielectric layer. Such a thicker terminal outer dielectric layer facilitates packaging of the structure within a larger array of device stacks, and/or to provide a greater exterior insulation to an overall array. [0088] In step 314, it is determined whether a final number of pairs of electrode sheets has been reached. In some implementations, the final number of pairs of electrode sheets may be as few as one pair of electrode sheets (i.e., one device stack). For two or more pairs of electrode sheets, the sub-process comprising steps 306 to 312 is repeated at least once to provide for at least two pairs of electrode sheets. In some implementations, the final number of pairs of electrode sheets may be as large as several thousand pairs of electrode sheets for example. The final number of pairs of electrode sheets desired may depend on the design considerations for a sensor being manufactured from the fabricated structures, such as a desired testing speed, a type of molecule to be analyzed, or a desired footprint for the sensor, and other considerations.

[0089] If the final number of pairs of electrode sheets has not been reached in step 314, the process returns to step 306 to deposit another first electrode layer against a side of the protrusion to form another first electrode sheet at an angle to the substrate plane. On the other hand, if the final number of pairs of electrode sheets has been reached in step 314, then the process proceeds to step 315 that comprises the removal of sacrificial layers or detachable shades that were added in step 305, discussed above. The sacrificial layer can, for example, be physically removed or removed by dissolution. The detachable shade can be physically removed. In one example, the sacrificial layer is dissolved using a liquid, as in lift-off processing.

[0090] At least one mechanically supportive block material is also added in step 315, such as with a gap-filling curable polymer. A mechanically supportive block material may be attached adjacent to the deposited multilayer stack (e.g., block 123 added to the right of the deposited layers shown in FIGS. IB and 2B). In some implementations, this is accomplished by attaching a block of ceramic material or polymer material, or by depositing a polymer material and subsequently curing the polymer. The space between the added supporting block and the previously deposited multilayers can be filled with a UV-curable, electron beam curable, or thermally curable polymer such as PMMA or hydrogen silsesquioxane (HSQ) resist. The HSQ resist layer deposited can be hardened by additional thermal curing to be close to the hardness of S1O2 type material. The mechanically supportive block material can be added to facilitate subsequent planarization, as in optional step 316, or to provide support for handling, such as during a subsequent packaging process of the structure 100.

[0091] Optional step 316 includes planarizing the pairs of electrode sheets, the inner dielectric sheets, and the one or more outer dielectric sheets formed from the previous repetitive steps, as necessary, of sub-process steps 306 to 312. The step of planarizing may comprise, for example, chemical-mechanical planarization (CMP) polishing, focused ion beam (FIB) etching, or (poly )methylmethacry late (PMMA) or HSQ filling and subsequent "etching back" by reactive ion etch (RIE). After the repeated deposition of thin film and thick film electrodes and dielectric layers, the mechanically supportive block material added and cured in step 315, such as a S1O2 material or a precursor of S1O2 (e.g., HSQ), can provide mechanical support of the structure during planarization. The location of the planarization on the structure may be, for example, along plane 117 shown in FIGS. IB or 2B, below the top surface of the protrusion 104. In other implementations, such as when deposition onto the top of the protrusion is shielded, planarization can take place just below the top surface of the protrusion 104 so as to remove the top surface of the protrusion, the electrode sheets, and the various inner and outer dielectric sheets, to expose the edges of the layers and level all of them substantially planar with a top surface of the protrusion 104. In various embodiments, planarization results in a structure having a top surface substantially parallel to the substrate plane 103. [0092] In certain examples, step 316 in FIG. 3 may be omitted when a shade extends far enough over an edge of the protrusion to prevent unwanted deposition on the top of the protrusion. In such an example, removal of the shade in step 315 may result in the exposed top surfaces of the pairs of electrode sheets substantially parallel without the need for planaraization.

[0093] High angle deposition

[0094] With reference now to FIG. 4A, a cross-sectional view of a structure 100 formed by various embodiments of the fabrication method is illustrated. The structure 100 comprises device stacks further comprising electrode pair sheets 107 and 115 separated by inner dielectric layer 108. In this embodiment, the structure 100 is fabricated by sequentially depositing tri-layer thin film device stacks using a high angle OAD. The high angle of deposition results in deposition of each thin film layer on both the substrate surface (or on the previous layer deposited on the substrate surface) and also on the surfaces of the protrusion 104 (or onto the layers previously deposited on the protrusion 104). The vertical or near vertical deposits are labeled as a first electrode sheet 107, an inner dielectric layer 108, a second electrode sheet 115, and an outer dielectric layer 112, whereas the horizontal or near horizontal deposits are labeled as a first electrode sheet 105, an inner dielectric layer 109, a second electrode sheet 113, and an outer dielectric layer 118. The vertical or near vertical portion and the horizontal or near horizontal portion of each layer necessarily connect since each layer was deposited onto both the protrusion surface and the substrate surface in each OAD step.

[0095] The horizontal or near horizontal dielectric layers in FIG. 4A include the inner dielectric layers 109 and the outer dielectric layers 115. As with the protrusion 104, the inner dielectric layers 109 and the outer dielectric layers 115 may comprise, for example, a dielectric material such as S1O2, AI2O ₃ , or MgO. As shown in FIG. 4A, a first portion of the inner dielectric layer 109 and the outer dielectric layer 115 are deposited in an orientation along the substrate plane 103 (i.e., horizontally in the example of FIG. 4A). A second portion of the inner dielectric layer 109 and the outer dielectric layer 115 are deposited in an orientation along the protrusion 104 (e.g., vertically onto the right side of the protrusion 104 in the example of FIG. 4A) to form the inner dielectric sheets 108 and the outer dielectric sheets 112, respectively. The inner dielectric sheets 108 and the outer dielectric sheets 112 are formed at an angle to the substrate plane 103.

[0096] The horizontal or near horizontal electrode layers in FIG. 4A include the first electrode layers 105 and the second electrode layers 113. The electrode layers may comprise, for example, a conductive metal such as Au, Pt, Pd, Ag, or Rh.

[0097] As shown in FIG. 4A, a first portion of the first electrode layers 105 and the second electrode layers 113 are deposited in an orientation along the substrate plane 103 (i.e., horizontally or near horizontally, as in the example of FIGS. 1A-1C). A second portion of the first electrode layers 105 and the second electrode layers 113 are deposited against the protrusion 104 (e.g., vertically or near vertically onto the right side of the protrusion 104 in the examples of FIGS. 1A-1C) to form the first electrode sheets 107 and the second electrode sheets 115, respectively. The first electrode sheets 107 and the second electrode sheets 115 are formed at an angle to the substrate plane 103, such as the angle at which the protrusion is oriented to the substrate.

[0098] Depositing the electrode layers and the dielectric layers at an angle to the substrate plane 103 can allow for exposing multiple pairs of electrode sheets. This can allow for scalability in fabricating a large number of electrode pairs by depositing many electrode and dielectric layers.

[0099] For example, a sequence of film depositions may comprise depositing a first conductor layer 105, followed by an inner dielectric layer 109, then followed by a deposition of a second conductor layer 113 to be paired with the first conductor layer 105, with the inner dielectric layer 109 being sandwiched by the first conductor layer 105 and second conductor layer 113. An outer dielectric layer 118 is then deposited with a sufficient thickness to separate the earlier-deposited conductor pair from a subsequent conductor pair. The deposition of conductor layer, dielectric layer, and second conductor layer can be repeated many times.

[00100] In addition to scalability, the thickness of the inner dielectric sheets 108/109 can be accurately controlled using CMOS type thin film deposition fabrication processes, as per the examples of FIGS. 1C and 2C discussed above. This can allow for a fixed and accurately controlled spacing between the two electrode sheets to facilitate a reliable and reproducible attachment of particular molecules across the electrodes in a pair of electrodes, such as certain proteins, DNAs, nucleotides, lipids, antibodies, hormones, carbohydrates, metabolites, pharmaceuticals, vitamins, neurotransmitters, enzymes, or another molecule to be analyzed. The use of standard CMOS processes to produce structures usable in multi-electrode molecule sensing devices also reduces the costs typically associated with manufacturing a molecule sensor.

[00101] FIG. 4B illustrates a cross-section view of the structure 100 of FIG. 4 A after planarization along 117 and removal of a portion of each of the inner dielectric sheets (as discussed below). Note that in this embodiment, planarization also removes thin layer film deposits that were deposited on the top surface of the protrusion 104 that resulted from the high incidence angle OAD process.

[00102] Each electrode sheet in FIG. 4B can have a thickness, for example, of from about 1 to about 100 nm. Depending on design considerations, such as the molecule to be analyzed, the electrode sheets and layers 107/105 and 115/113 can be deposited with a thickness of from about 1 to about 40 nm, or from about 5 to about 15 nm. In such implementations, the inner dielectric sheets and layers 108/109 can be deposited with a similar thickness of from about 1 to about 40 nm, or from about 2 to about 15 nm. The outer dielectric sheets and layers 1 12/118 may be deposited with a thickness of between about 50 to about 2,000 nm, or at least about one order of magnitude greater than the thickness of the inner dielectric sheets and layers 108/109.

[00103] With continued reference to the planarized structure 100 in FIG. 4B, the exposed first electrode sheet 107 and the exposed second electrode sheet 115 form pairs of electrode sheets 106, each electrode in the pair separated by an inner dielectric sheet. In this embodiment of structure 100, exposed end portions of each inner dielectric sheet are shown as having been removed to form a recess 1 10 in the inner dielectric sheet extending down from the planarized surface. This recess is also referred to herein as a groove 110 in each inner dielectric sheet extending below the planarized surface. The free space within the groove 110 between the two electrode sheets and absent dielectric material can allow bridge molecules 10 to be more conveniently attached to each electrode pair, as shown in FIG. 4B. The molecules 10 may comprise, for example, a protein, DNA, nucleotide, lipid, antibody, hormone, carbohydrate, metabolite, pharmaceutical, vitamin, neurotransmitter, enzyme, or another type of molecule to be analyzed or identified.

[00104] In a molecular sensor utilizing an embodiment of structure 100, one electrode sheet in a pair of electrode sheets 106 can serve as a source electrode and the other electrode sheet in the pair can serve as a drain electrode. In operation, a molecule 10 is attached to each electrode sheet in the pair of electrode sheets as shown in FIG. 4B to form a molecular bridge between the first and second electrode sheets in each pair. The molecule 10 may comprise, for example, a protein, DNA, antibody, nucleotide, lipid, hormone, carbohydrate, metabolite, pharmaceutical, vitamin, neurotransmitter, enzyme, or another type of molecule to be identified or analyzed. The molecule 10 can then be detected or analyzed by measuring an electronic signal, or used to detect analytes that interact with the molecule 10. In some implementations, a current is passed through the molecule 10, in a circuit including the first electrode sheet 107, the second electrode sheet 115, and the molecule 10. Based on the measured current through this circuit, the molecule 10 can be identified, quantified, and/or analyzed, or various analytes capable of interacting with the molecule 10 can be identified, quantified, or analyzed. Such an implementation can allow a molecular sensor comprising an embodiment of structure 100 to be used for genome sequencing.

[00105] In some implementations, a single structure 100, configured for inclusion in a molecular sensor device, can include up to one thousand pairs of electrode sheets 106 or more. Such a structure provides for scalability in sensor fabrication, wherein multiple structures 100 are combined in a sensor device to obtain an even greater number of pairs of electrode sheets. The resulting sensor device is capable of simultaneously testing more molecules in a shorter time.

[00106] With continued reference to FIG. 4B, each pair of electrode sheets 106 is separated by an outer dielectric sheet 112. An inner dielectric sheet 108 separates the first electrode sheet 107 and the second electrode sheet 115 in a pair of electrode sheets 106. In some implementations, the inner dielectric sheets 108 can all have approximately a first thickness (e.g., within a 5% tolerance or so), while all the outer dielectric sheets 112 can have approximately a second thickness (e.g., also within a 5% tolerance or so), wherein the second thickness is at least one order of magnitude greater than the first thickness. The thicker outer dielectric sheet 112 provides separation between adjacent pairs of electrode sheets 106 to reduce electrical or capacitance interference between adjacent pairs of electrodes, and minimize the possibility that bridging molecules bridge between adjacent pairs of electrodes (over an outer dielectric layer) rather than across the two electrodes in each pair (over an inner dielectric layer), amongst other advantages.

[00107] For example, a desired thickness of the outer dielectric sheets 112 can be at least about 1 μιη or at least about 10 μιτι, while a desired thickness for the inner dielectric sheets 112 can be at most about 50 nm or at most about 20 nm. In some implementations, the thickness of the inner dielectric sheets 112 can be at most about 10 nm. Having an accurately controlled inner dielectric layer thickness can improve the the chances for reliable and reproducible attachment of certain molecules to the pairs of electrode sheets 106, which results in more accurate readings from a molecular sensor constructed out of structure 100, since it is less likely that other types of molecules inadvertently attach to the electrode sheets given the relatively precise spacing to coordinate with the size of the molecules.

[00108] A groove 110 created in the inner dielectric sheet 108 can facilitate the attachment of a molecule 10 in construction of a molecular sensor and improve the operation of the finished sensor. In some implementations, removal of a portion of inner dielectric material to create each groove can be accomplished by localized etching or by deposition of the inner dielectric sheet with local masking. In these ways, a groove 110 is formed in each of the inner dielectric sheets 108. In various embodiments, each groove in the inner dielectric sheets measure from about 5 to about 15 nm in depth from the planarization surface. In other words, the extent of removal of inner dielectric sheet material is from about 5 to about 15 nm from the exposed end portion of the inner dielectric sheet 108 created by the panarization. Removal of the exposed end portions of each of the inner dielectric sheets provides free space for accommodating the movement and attachment of certain biomolecules across electrodes in a pair of electrodes, bridging over these grooves etched in the dielectric material. [00109] Depending on the method used to remove the exposed end portions of each inner dielectric sheet, the groove thus created may have a shape other than rectangular cuboid. For example, portions of the inner dielectric sheet adjacent each electrode may remain after partial removal such that a cross-sectional view of the groove may appear parabolic, (e.g., see shape of the groove 210 in the embodiment of FIG. 12). Grooves need not be fully cleaned out of all dielectric material to provide the air space that aids attachment and movement of each bridge molecule across each pair of electrodes.

[00110] FIG. 5 illustrates a flowchart summarizing an exemplary manufacturing process to fabricate the structure of FIG. 4B. As discussed, the fabrication process comprises relatively high incident angle OAD. Further as discussed herein, the higher incident angle OAD, higher than the angle of OAD used in the example process of FIG. 3 to produce the structures of FIGS. 1A-1C, electrode and dielectric thin film layers are also deposited on the surface of the protrusion 104 opposite the substrate 102 (i.e., the top surface of the protrusion 104 in FIG. 4A). The layers deposited on the top surface of the protrusion are sacrificed in the subsequent planarization step to expose the edges of the electrode sheets and dielectric sheets that were formed at an angle to the substrate plane 103.

[00111] In comparison to the process of FIG. 3, the process of FIG. 5 generally does not include the placement of sacrificial layers or detachable shades as in step 305 of FIG. 3, or the removal of such sacrificial layers or detachable shades as in step 315 of FIG. 3. The higher deposition angle of the OAD can usually prevent the unwanted deposition of layers without using sacrificial layers or detachable shades.

[00112] In step 502 of FIG. 5, a substrate such as the substrate 102 is provided. The substrate may be planar and thus defines a substrate plane. The substrate plane is defined as being parallel with a major surface of the substrate, such as a top or bottom surface, that will support the various dielectric and electrode layers. [00113] In step 504, a protrusion (e.g., protrusion 104) is attached to the substrate, or in alternative embodiments, the protrusion may be formed by removing one or more portions of a larger substrate. As noted above, the protrusion extends or protrudes from the substrate plane at an angle, such as 90°. In one example, the protrusion can be a step- shaped cut-out of an initially thicker supporting substrate. In other examples, a dielectric block of material or other shape of dielectric material may be attached to a supporting substrate at any angle to form the protrusion on the substrate plane.

[00114] In step 506, a first electrode layer is deposited on the substrate using a relatively high angle OAD, such as between about 20° and 70° from the substrate plane. At least a portion of the first electrode layer is deposited in an orientation along a side of the protrusion to form a first electrode sheet (e.g., first electrode sheet 107 in FIG. 4A) at an angle to the substrate plane. In other implementations, an initial dielectric layer may be deposited before the first electrode layer is deposited in step 506.

[00115] In step 508 of the example process of FIG. 5, an inner dielectric layer is then deposited on the first electrode layer that was previously deposited in step 506. As shown in the example of FIG. 4A, at least a portion of the inner dielectric layer is deposited in the orientation along the protrusion 104 to form the inner dielectric sheet 108 at an angle to the substrate plane 103. As with the first electrode layer deposited in step 506, OAD can be used to deposit the inner dielectric layer at an angle to the substrate plane. Standard CMOS processes such as OAD can ordinarily allow for the inner dielectric layer to be deposited with an accurate and repeatable thickness.

[00116] In some implementations, a thin adhesion enhancing layer may be deposited on the first electrode layer before and/or after depositing the inner dielectric layer to improve adhesion of the layers. In one example, an approximately 1 to approximately 5 nm thick film material is deposited at the interface using a material such as Ti, Cr, Al, Zr. Mo, Nb, Ta, or Hf.

[00117] In step 510, a second electrode layer is then deposited on the inner dielectric layer to form a second electrode sheet (e.g., second electrode sheet 115 in FIG. 4A) at an angle to the substrate plane, using, for example, OAD. The first electrode sheet and the second electrode sheet form a pair of electrode sheets with the inner dielectric sheet between and separating the first and second electrode sheets.

[00118] In step 512, an outer dielectric layer is then deposited on the second electrode layer to form an outer dielectric sheet at an angle to the substrate plane. With reference to the example in FIG. 4B, the outer dielectric layer is deposited on the second electrode layer to form the outer dielectric sheet 1 12 at an angle to the substrate plane 103. In some implementations, an outer dielectric layer may be deposited at a different thickness than any previous outer dielectric layers if it comprises a final outer dielectric layer. A thicker final outer dielectric layer can, for example, facilitate packaging of multiple structures in a sensor device, whereby the thicker final outer dielectric layer of one structure is packaged against a first electrode sheet layer in an adjacent structure. In certain embodiments, structures with thicker final outer dielectric layers can be packaged into sensor devices such that the thicker final outer dielectric layers form an exterior periphery to the sensor device, such as to provide a greater exterior insulation for the sensor.

[00119] In step 514, a determination is made whether a final number of pairs of electrode sheets have been reached. In some implementations, the final number of pairs of electrode sheets may be as few as two pairs of electrode sheets. In this regard, the sub- process of steps 506 to 512 is repeated at least once to provide for at least two pairs of electrode sheets. In various examples, the final number of pairs of electrode sheets may be as large as several thousand pairs of electrode sheets. The final number of pairs of electrode sheets for a device stack may depend on the design considerations for a sensor comprising the device stack. Design considerations include, but are not limited to, a desired testing speed for a sensor, a type of molecule to be analyzed by the sensor, and a desired footprint for the sensor.

[00120] If the final number of pairs of electrode sheets has not been reached in step 514, the process returns to step 506 to deposit another first electrode layer in an orientation along a side of the protrusion to form another first electrode sheet at an angle to the substrate plane.

[00121] On the other hand, if the final number of pairs of electrode sheets has been reached in step 514, the process proceeds to step 515 to add at least one mechanically supportive block material with a gap-filling curable polymer. A mechanically supportive block material may be attached adjacent the deposited multilayer stack (e.g., block 123 added to the right of the deposited layers shown in FIG. 4A). In some implementations, this is accomplished by attaching a block of ceramic or polymer material, or by depositing a polymer material and curing. The gap between the added supporting block and the previously deposited multilayers can be filled with a UV-curable, electron beam curable, or thermally curable polymer such as PMMA or HSQ resist. The HSQ resist layer deposited can be hardened by additional thermal curing to be close in hardness to a S1O2 type or harder material. The mechanically supportive block material is added for subsequent planarization, as in step 516, or to provide support for handling, such as during a subsequent packaging process of a sensor comprising the structure 100.

[00122] Step 516 further comprises planarizing the pairs of electrode sheets, the inner dielectric sheets, and the one or more outer dielectric sheets, formed by repeating the sub- process of steps 506 to 512. The planarizing may comprise, for example, CMP polishing, FIB etching, or PMMA or HSQ filling and etching back by RIE. After the repeated deposition of thin film and thick film electrodes and dielectric layers, the mechanically supportive block material added and cured in step 515, such as a S1O ₂ material or a precursor of S1O ₂ (e.g., HSQ), can provide support during planarization.

[00123] With reference to FIG. 4A, planarization can take place along the planarization line 117, which is along the top surface of the protrusion 104 so that an exposed top surface of the electrode sheets and dielectric sheets is substantially planar with a top surface of the protrusion 104 or parallel to the substrate plane 103. In other implementations, the planarization can take place below the top surface of the protrusion 104 to expose the pairs of electrode sheets, such as along the planarization line 117' .

[00124] Additional fabrication methods

[00125] FIG. 6 illustrates a flowchart for an embodiment of a manufacturing process that can follow the manufacturing process of either FIG. 3 or FIG. 5. In step 602, a groove is formed on an exposed end portion of each inner dielectric sheet by removal of dielectric material. As noted above, the groove can be formed by etching the inner dielectric sheet using an etching process such as RIE, sputter etching, or chemical etching, such as with HF. In various implementations, an electrical, capacitance, or optical measurement, such as a voltage, electrical resistance, or optical penetration or interference, can be measured between a first and second electrode sheet while forming the groove into the exposed end portion of the dielectric sheet between the electrodes, as an indicator of the depth of the groove thus formed. For example, etching can be performed until a measurement reaches a threshold value corresponding to a desired depth of the groove in the dielectric sheet between electrodes. Removal of dielectric material from the inner dielectric sheet is then stopped based on the measurement (voltage, electrical, optical, interference, etc.) reaching the threshold value. [00126] In step 604, a dielectric cover layer is optionally deposited to define a gap exposing a portion of the plurality of pairs of electrode sheets. In some implementations, a mask line is deposited across an end portion of the pairs of electrode sheets and the dielectric cover layer is deposited on at least one side of the mask line to cover a remaining exposed portion of the pairs of electrode sheets not covered by the mask line. The mask line is then removed so that the dielectric cover layer defines a gap exposing the end portion of the pairs of electrode sheets. In certain examples, two dielectric cover layers are deposited adjacent to one another and across the exposed end portions of the electrode sheets to define a gap between the two dielectric portions in which the electrode edges remain exposed. In other embodiments, step 604 may be omitted such that the deposition of one or more dielectric cover layers and optional mask line is not performed.

[00127] By limiting the exposed area of the pairs of electrode sheets to only a gap between dielectric cover layers, it is ordinarily possible to prevent more than one molecule from attaching to the exposed edges of the electrode sheets in each pair of electrode sheets. When more than one molecule attaches to an electrode pair, the readings for the pair of electrode sheets are affected. In the case where a current is measured between the electrodes in a pair of electrodes through the bridging molecule in a circuit, the attachment of multiple molecules between the electrodes can lower the current measured across the electrodes and lead to undiscernible current measurements. Having only a single molecule per electrode pair improves the accuracy of a sensor device based on these structures.

[00128] In some implementations, the gap defined by the dielectric cover layer is between about 2 to about 40 nanometers depending on the type of molecule to be attached. In some implementations, the width of the gap can be between about 5 and about 15 nm wide. [00129] FIG. 7A shows placement of a mask line 114 across exposed edges of pairs of electrode sheets 106 and inner and outer dielectric layers. As shown, the mask line 114 may be deposited on the planarized top surface of the structure, perpendicular to the exposed edges of electrodes and dielectric layers appearing as strips on the planarized surface. The mask line 1 14 can be deposited on the top surface of the structure using, for example, an HSQ resist. As shown in FIG. 7B, two portions of dielectric cover layer 1 16 are deposited on both sides of the mask line 1 14. The dielectric cover layers 1 16 may comprise, for example, S1O2 layers. After removal of the mask line 1 14, only the end portion of the electrode sheet pairs in the gap 1 18 between dielectric layer portions are exposed for attaching a single bridging molecule 10 to each exposed pair of electrode sheets. In other implementations, the gap 118 may be formed by using a patterning process such as e-beam lithography or nano-imprinting, and etching an unmasked region to form the gap 118. In some examples, the gap 118 can have a width between about 2 to about 40 nm, or from about 5 to about 15 nm, such as to facilitate the attachment of a single molecule at each pair of electrode sheets 106.

[00130] Returning to the manufacturing process of FIG. 6, an exposed edge of each electrode sheet can be roughened in step 606 to improve the attachment of a molecule to the edge of the electrode sheet. FIG. 8 illustrates the roughening of an exposed portion of the first electrode sheets 107 and the second electrode sheets 115 according to various embodiments. The exposed portions of the electrode sheets in gap 118 may be roughened by, for example, dealloying of a base alloy (e.g., dealloying an Au-Ag alloy), mechanical sand blasting, ion bombardment, electron bombardment, ion implantation, chemical etching, or electrochemical etching. The surface roughening may include a feature size of about 0.5 to about 20 nm. In some examples, the surface roughening feature size can be between about 1 to about 10 nm, or between about 1 to about 5 nm. [00131] The roughening of the exposed edges of the electrode sheets ordinarily provides for easier and more secure molecular attachment due to the higher surface area of the roughened surface. Other processes may be performed on the exposed edges of the electrode sheets to improve attachment of an analyte molecule. Examples of such processes include, but are not limited to, the nano-tip or nano-pillar conductive islands disclosed in PCT Application No. PCT/US 17/15437, the entire contents of which are hereby incorporated by reference. Other examples of improving the attachment of an analyte molecule to the exposed edges of the electrode sheets include using conductive islands with reduced contact resistance disclosed in PCT Application No. PCT/US 17/17231, the entire contents of which are hereby incorporated by reference.

[00132] Returning to the process of FIG. 6, a plurality of lead conductors are connected to the plurality of electrode sheets in step 608, with each lead conductor connected to a respective electrode sheet. As shown in the example of FIG. 9, the lead conductors 120 diverge in width as the lead conductor extends away from an edge of the electrode sheet toward the contact 122. The lead conductors can be made of a conductive material such as gold for carrying a test signal from the electrode sheets. In some implementations, the thickness of the electrode sheets can be as small as about 10 nm. The lead conductors may then fan out from a width of approximately 10 nm to a scale of micrometers to allow for soldering at the contacts 122. The contacts 122 can include a contact pad array for circuit packaging, solder bonding, or wire bonding.

[00133] As shown in FIG. 9, a dielectric cover layer 124 (the borders of which are represented by dashed lines) may also be applied so that only a portion of the pairs of electrode sheets 106 are exposed. The dielectric cover layer 124 may also cover a portion of the lead conductors 120 as shown. In some implementations, the dielectric cover layer 124 can have a thickness of about 1 to about 20 nm or from about 1 to about 10 nm, and comprise a dielectric material such as S1O2, AI2O ₃ , MgO, PMMA, or polydimethylsiloxane (PDMS). Similar to the dielectric cover layers discussed above for step 604, the dielectric cover layer 124 in FIG. 9 can facilitate attachment of only one molecule 10 per pair of electrode sheets 106, as shown for each pair of electrode sheets in FIG. 9. A sensor device comprising the structure of FIG. 9 may have more accurate readings by having only one molecule 10 per electrode pair. The triangular shapes in FIG. 9 are generic representations of analyte molecules interacting with bridge molecules 10 in the structure. One bridge molecule 10 per electrode pair also ensures that analyte molecules only interact with one circuit comprising an electrode pair and single bridge molecule 10.

[00134] In some implementations, multiple structures such as the block shown in FIG. 9 may be joined together for scalability of molecular sensors. For example, 1 to 1 ,000 blocks may be joined together, with each block including 100 to 5,000 pairs of electrode sheets 106. The joined blocks may then be planarized to the same height using, for example, CMP polishing, FIB etching, PMMA or HSQ filling and etching back by RIE. This can also allow for the placement of electrical circuits or components on the joined blocks.

[00135] In step 610 of FIG. 6, a gate electrode is optionally deposited parallel to the substrate plane and perpendicular to an electrode plane defined by an electrode sheet. The gate electrode can include, for example, a Si or metallic electrode placed on a side of the substrate opposite the electrode sheets or near a front portion of the electrode sheets on the same side of the substrate as the electrode sheets. FIG. 10, discussed below, provides examples showing the placement of electrode gates in these locations.

[00136] As shown in FIG. 10, an electrode gate 126 is located near the front portion of the electrode sheets and extends along a length of the electrode sheets in a direction perpendicular to the electrode sheet plane 125 defined by one of the electrode sheets. Another electrode gate 127 is located on the backside of the substrate 102 extending across the substrate 102 in a direction perpendicular to the electrode sheet plane 125.

[00137] The addition of an electrode gate can ordinarily improve the accuracy of readings from the pairs of electrode sheets by imposing an electric field to regulate the charge carriers between the first electrode sheet and the second electrode sheet serving as source and drain electrodes in a pair of electrodes. An electrode gate can be especially useful in implementations where the electrode sheets include a semiconductor. On the other hand, some implementations may not include an electrode gate, in which case step 608 may be omitted from the process of FIG. 6.

[00138] In some implementations, the structure of FIG. 10 may further comprise one or more dielectric cover layers similar to the dielectric cover layer 124 in FIG. 9 discussed above. The dielectric cover layer or layers can be deposited at an angle to or perpendicular to the electrode sheets on the surface of the planarized structure to expose only a narrow gap portion of the electrode sheets for molecular sensing.

[00139] In step 612 of FIG. 6, a plurality of channels is optionally formed with each channel arranged to introduce a fluid to the exposed portions of the electrode sheets. Each channel includes at least two pairs of electrode sheets. As shown in the example of FIG. 11 , each channel can be formed by adding a wall 128 between groups of pairs of electrode sheets. A fluid such as a gas or liquid containing the molecules to be tested can then be introduced into the channel so that multiple pairs of electrodes can be used to test the molecules in the fluid. In the example of FIG. 11 , each channel is loaded with a fluid containing a different DNA nucleobase for detection via the pairs of electrode sheets 106 in the channel.

[00140] The arrangement shown in FIG. 1 1 can ordinarily allow for error correction or compensation by loading the same fluid to be tested (e.g., a fluid with molecules 10, 12, 14, or 16 in FIG. 1 1) across multiple pairs of electrode sheets 106 and using the different measurements for the different pairs of electrode sheets to average out any error and/or eliminate a measurement that deviates by more than a threshold. Although three pairs of electrode sheets are shown per channel in the example of FIG. 1 1, a different number of pairs can be used in other implementations, such as ten or twenty pairs or more of electrode sheets per channel.

[00141] In some implementations, the arrangement shown in FIG. 11 may further comprise one or more dielectric cover layers similar to the dielectric cover layer 124 in FIG. 9 discussed above. The dielectric cover layer or layers can be deposited at an angle to or perpendicular to the electrode sheets on the surface of the planarized structure to expose only a narrow portion of the electrode sheets for molecular sensing.

[00142] FIG. 12 provides a side view of a structure 200 usable in a molecular sensor according to an embodiment where the structure for the sensor is manufactured by forming a stack of electrode and dielectric layers and slicing through the stack. As shown in FIG. 12, structure 200 comprises a supporting substrate 202 that may comprise, for example, S1O2 or Si with a S1O2 coating. In the example of FIG. 12, the pairs of electrode sheets 206, inner dielectric sheets 208, and outer dielectric sheets 212 are at a perpendicular angle to the substrate 202 so that the electrode sheets are in a vertical or near-vertical configuration. Other implementations can include a tilted angle orientation of up to about a 60° tilting of the electrode sheets from a vertical alignment, but preferably with less than about 20° tilt. In such implementations, the sheets may extend from the substrate 202 at an angle, such as about a 45° or about a 60° angle.

[00143] The inner dielectric sheets 208 and the outer dielectric sheets 212 may comprise, for example, a dielectric such as S1O2, AI2O ₃ , or MgO. In various embodiments, the inner dielectric sheets 208 comprise a different material than the outer dielectric sheets 212. For example, inner dielectric sheets may comprise S1O2 whereas outer dielectric sheets 212 may comprise AI2O ₃ or MgO. In such embodiments, S1O2 inner dielectric sheets may be selectively etched (e.g., by CF ₄ plasma etching) to form the grooves 210, without concomitant etching of the AI2O ₃ or MgO outer dielectric sheets. The electrode sheets 207 and 215 may comprise, for example, a conductive metal such as Au, Pt, Pd, Ag, or Rh.

[00144] As discussed in more detail below with reference to FIGS. 14A-14C, the structure 200 usable in a molecular sensor may be formed by slicing a stack of dielectric and electrode layers into a plurality of chips, and attaching the plurality of chips to a substrate, such as substrate 202, so that a desirably aligned structure of electrode pairs and dielectric spacers is obtained. This can ordinarily allow for fabricating a large number of electrode sheet pairs 206 by attaching multiple chips and/or using multiple layers in forming the stack.

[00145] The alignment of layers at an angle to the substrate 202, as opposed to parallel to the substrate 202, improves control of the degree of etching of the inner dielectric sheets 208 to form the grooves. This can allow for a more accurate and reproducible cavity structure or grooves 210 to provide for easier attachment of a single molecule for analysis when DNA, a nucleotide, or other analyte is attached. In addition, and as with the structure 100 discussed above, the thickness of the inner dielectric layers 208 can be accurately controlled using standard CMOS fabrication processes to facilitate the attachment of particular molecules such as proteins, DNAs, enzymes, nucleotides, or other molecules to be analyzed. The use of standard CMOS processes to produce multi- electrode molecule sensing devices also reduces the costs typically associated with manufacturing a molecule sensor.

[00146] The exposed first electrode sheets 207 and the exposed second electrode sheets 215 form pairs of electrode sheets 206 for attaching molecules 10. One electrode sheet in the pair of electrode sheets 206 can serve as a source electrode and the other electrode sheet can serve as a drain electrode. A molecule 10 is attached to each electrode sheet in the pair of electrode sheets as shown in FIG. 12 to form a molecular bridge. The molecule 10 may comprise, for example, a protein, DNA, antibody, nucleotide, lipid, hormone, carbohydrate, metabolite, pharmaceutical, vitamin, neurotransmitter, enzyme, or another type of molecule to be identified or analyzed. The molecule 10 can then be detected or analyzed by measuring an electronic signal in the completed molecular sensor incorporating the structures herein. In some implementations, a current can be passed through the molecule 10 by forming a circuit including the first electrode sheet 207, the second electrode sheet 215, and the molecule 10. Based on the measured current, the molecule 10 can be identified or analyzed. Such an implementation can allow the molecular sensor incorporating structures such as structure 100 to be used for genome sequencing.

[00147] In some implementations, structure 200 can include up to one thousand pairs of electrode sheets 206. Structure 200 can also provide for scalability in a completed sensor by combining multiple structures such as structure 200 together to obtain an even greater number of pairs of electrodes to simultaneously test more molecules. This scalability can ordinarily reduce the time for analyzing a large number of molecules at the same time.

[00148] As shown in FIG. 12, each pair of electrode sheets 206 is separated by an outer dielectric sheet 212. An inner dielectric sheet 208 separates the first electrode sheet 207 and the second electrode sheet 215 in a pair of electrode sheets 206. In some implementations, the inner dielectric sheets 208 can all have approximately a first thickness (e.g., within a tolerance of about 5%), while all the outer dielectric sheets 212 can have approximately a second thickness (e.g., within a tolerance of about 5%) that is at least one order of magnitude greater than the first thickness. The thicker outer dielectric sheet 212 provides separation between adjacent pairs of electrode sheets 206 to reduce electrical, inductive, or capacitance interference.

[00149] In some implementations, a desired thickness of the outer dielectric sheets is at least about 0.5 μιτι, and in some instances at least about 1 μιη or at least about 10 μιτι, while the inner dielectric sheets are at most about 50 nm, about 20 nm, or about 10 nm thick. As noted above, an accurately controlled inner dielectric sheet thickness can ordinarily improve the reliable and reproducible attachment of certain molecules to the pairs of electrode sheets 206. This in turn can result in more accurate readings from the sensor comprising structure 200 since it is less likely that other types of molecules inadvertently attach to the electrode sheets.

[00150] A groove 210 in the inner dielectric sheet 208 can facilitate the attachment of a molecule 10 for analysis during operation. In some implementations, a groove 210 in the dielectric material can be introduced by localized etching of the end portion of each inner dielectric sheet or by deposition with local masking to form a groove 210 in the inner dielectric sheet 208. For example, a space with depth of about 5 to about 15 nm can be etched to facilitate the attachment of certain biomolecules. As shown herein, the grooves 210 may appear as parabolas when cross-sectioned rather than as squares or rectangles. The processes used to form the grooves 210 need not remove all of the dielectric material adjacent to the electrode sheets down to the desired depth for the groove.

[00151] FIG. 13 is a flowchart for a manufacturing process of the molecular sensor 200 of FIG. 12 according to another embodiment. As shown in FIG. 13, steps 1302 to 1312 are collectively performed to form a device stack that is later sliced in step 1314 to form multiple chips that are attached to a substrate in step 1316.

[00152] In step 1302, a first outer dielectric layer is provided, and a first electrode layer is deposited on the first outer dielectric layer in step 1304. The first electrode layer can be deposited using a standard CMOS deposition technique. In some implementations, the outer dielectric layer may have a different thickness than other outer dielectric layers, for example, facilitate packaging of a sensor incorporating such structures in a larger array of sensors or to provide a greater exterior insulation. In other implementations, the thickness of the first outer dielectric layer may be the same as other outer dielectric layers located between electrode sheets in the pairs of electrode sheets.

[00153] In step 1306, an inner dielectric layer is deposited on the first electrode layer. A second electrode layer is deposited on the inner dielectric layer in step 1308 to form a pair of electrode layers with the inner dielectric layer between the first and second electrode layers. In step 1310, a second outer dielectric layer is deposited on the second electrode layer that was deposited in step 1308. The thickness of the second outer dielectric layer may be the same or may differ from the thickness of the first outer dielectric layer provided in step 1302.

[00154] In step 1312, it is determined whether a final number of pairs of electrode layers have been reached for the stack. If so, the process proceeds to step 1314 wherein the stack is sliced through at least once, at an angle to the layers in the stack, to form a plurality of chips from the sliced portions of the stack. The plane of slicing may be substantially perpendicular to the layers in the stack, meaning that the slicing is at an angle of about 90° to the layers in the stack. If it is determined that the final number of electrode pairs have not been reached in step 1312, the process returns to step 1304 to deposit another first electrode layer on the second outer dielectric layer deposited in step 1310. The depositing of the first electrode layer, the inner dielectric layer, the second electrode layer, and the second outer dielectric layer in steps 1304 to 1310 repeats until a final number of pairs of electrode layers has been reached in step 1312. [00155] FIG. 14A provides an example of a stack 230 formed by performing steps 1302 to 1312 in the manufacturing process of FIG. 13. As shown in FIG. 14A, a first electrode layer 205 is deposited on the first outer dielectric layer 227. An inner dielectric layer 209 is deposited on the first electrode layer 205 and a second electrode layer 219 is deposited on the inner dielectric layer 209. A second outer dielectric layer 223 is deposited on the second electrode layer 219. This pattern of depositing a first electrode layer 205, an inner dielectric layer 209, a second electrode layer 219, and a second dielectric layer 223 is repeated two more times in the example of FIG. 14A to result in a stack 230 comprising three pairs of electrode layers.

[00156] In some implementations, a thin adhesion enhancing layer may be deposited at the interfaces between the electrode layers and the inner dielectric layers to improve the adhesion of the layers. In one example, an about 1 to about 5 nm thick film material is deposited at the interface using a material such as Ti, Cr, Al, Zr. Mo, Nb, Ta, or Hf.

[00157] In some implementations, the electrode layers 205 and 219 are deposited with a thickness of about 1 to about 40 nm, or in some embodiments, from about 5 to about 15 nm. In such implementations, the inner dielectric layers 209 can be deposited with a similar thickness of about 1 to about 40 nm or about 2 to about 15 nm. The outer dielectric layers 223 are deposited with a thickness between about 50 to about 2,000 nm, or at least about one order of magnitude greater than the thickness of the inner dielectric layers 209.

[00158] Returning to the process of FIG. 13, the stack formed in steps 1302 to 1312 is sliced through at least once in step 1314 to form a plurality of chips from the sliced portions of the stack. The stack is sliced at an angle to the layers in the stack to expose a cross section of the layers previously deposited in the stack. In some implementations, the stack is sliced at a 90° angle to the layers in the stack. In other implementations, the stack may be sliced at a different angle to the layers in the stack. To better understand the angle of slicing with respect to the layers in a stack, the planes 225 in FIG. 14B represents what are essentially slices at an angle of about 90° to the layers in the stack, which produces the individual chips 232 as shown.

[00159] FIG. 14B illustrates the slicing of the stack 230 of FIG. 14A to form a plurality of chips 232 including at least one pair of electrode sheets. As shown in FIG. 14B, the stack 230 is sliced along planes 225 to form three chips 232, which may have the same thickness/height or different thicknesses/heights.

[00160] In step 1316 of FIG. 13, the plurality of chips are attached to a substrate so that the sliced portions of the first electrode layer or layers and the second electrode layer or layers form a plurality of pairs of electrode sheets at an angle to a substrate plane defined by the substrate. In addition, the sliced portions of the inner dielectric layer or layers form a plurality of inner dielectric sheets with each inner dielectric sheet between each electrode sheet in each pair of electrode sheets.

[00161] The manufacturing process of FIG. 13 may be followed by one or more additional processes, such as any of the steps in FIG. 6 discussed above. Such additional processes can include, for example, forming a groove on an exposed end portion of each inner dielectric sheet (e.g., step 602 in FIG. 6), defining a gap in a cover layer (e.g., step 604), roughening an exposed edge of each electrode sheet (e.g., step 606), depositing a gate electrode (e.g., step 608), forming a plurality of channels (e.g., step 610), and connecting lead conductors (e.g., step 612).

[00162] FIG. 14C is a cross sectional view showing the placement of a chip 232 from FIG. 14B on a substrate 202 during the manufacturing process of FIG. 13. As shown in FIG. 14C, a chip 232 has been rotated 90° and attached to substrate 202 to reveal multiple exposed electrode sheet pairs 206. Each pair of electrode sheets 206 includes a first electrode sheet 207 and a second electrode sheet 215, with an inner dielectric sheet 208 sandwiched between the electrode sheets. Outer dielectric sheets 212 are provided between each pair of electrode sheets 206 and on the ends of the chip 232. In some implementations, the first or the last outer dielectric sheets 212 may have a different thickness than other outer dielectric sheets.

[00163] FIG. 15 illustrates the placement of multiple chips 232 on a substrate 202 according to an embodiment. Adding more chips 232 to the substrate 202 increases the number of pairs of electrode sheets, which in turn, provides more sites for attaching molecules to the exposed ends of the electrode sheets. In the example of FIG. 15, the chips 232 are mounted on the substrate 202 with space between the chips 232. The spaces between the chips 232 in some implementations can be filled with a material such as S1O2 paste or a precursor to S1O2, such as HSQ resist, which may be later planarized to reveal the top edges of the electrode sheets. Planarization may comprise, for example, CMP polishing, FIB etching, or PMMA or HSQ filling and etching back by RIE.

[00164] Although the example of FIG. 15 shows chips each having three pairs of electrode sheets 206, other implementations may include a different number of pairs of electrode sheets, such as chips having 2 to 2,000 pairs or more of electrode sheets. Each electrode sheet can have a thickness of about 2 to about 100 nm. In this regard, some implementations may include electrode sheets having a thickness of about 1 to about 40 nm, or about 5 to about 15 nm, depending on design considerations such as the molecule to be analyzed by the completed sensor.

[00165] FIG. 16 illustrates the placement of a dielectric cover layer 216 on the multiple chips 232 of FIG. 15 according to an embodiment. As shown in FIG. 16, the dielectric cover layer 216 can facilitate the attachment of only a single molecule to the exposed portions of the electrode sheets in an electrode sheet pair 206 in the gap 218. As discussed above with reference to the example of FIGS. 7A and 7B, a mask line can be deposited and then removed after the dielectric cover layer has been deposited to form the gap 218. In other implementations, the gap 218 may be formed by using a patterning process such as e-beam lithography or nano-imprinting, and etching an unmasked region to form the gap 218. In some examples, the gap can have a width between about 2 to about 40 nm or from about 5 to about 15 nm to facilitate the attachment of a single molecule at each pair of electrode sheets 206.

[00166] In addition, and as discussed above with reference to step 602 in FIG. 6 and to grooves 210 in FIG. 12, an unmasked region of the inner dielectric sheets 208 can be, for example, etched by RIE, sputter etching, or chemical etching, such as with HF, to form grooves 210 between the electrode sheets in the electrode sheet pairs 206.

[00167] FIG. 17 is a top view of an embodiment of a structure for use in a molecular sensor, wherein the stack comprises multiple chips 232 and diverging lead conductors 220. As shown in FIG. 17, each lead conductor 220 diverges in width as the lead conductor extends away from an edge of the electrode sheet toward the contact 222. The lead conductors can be made of a conductive material such as gold for carrying a test signal from the electrode sheets. In some implementations, the thickness of the electrode sheets can be as small as only about 10 nm.

[00168] The lead conductors may then fan out from a width of approximately 10 nm to a scale of micrometers to allow for soldering at the contacts 222. The contacts 222 can include a contact pad array for circuit packaging, solder bonding, or wire bonding. In addition, a dielectric cover layer 224 is deposited so that only an end portion of the electrode sheets are exposed for attaching a single molecule to each pair of electrode sheets 206.

[00169] In some implementations, a gate electrode, such as the gate electrodes 126 or 127 shown in FIG. 10 discussed above may also be applied to the structure to improve the accuracy of readings from the pairs of electrode sheets 206 in a sensor by imposing an electric field to regulate the charge carriers between the first electrode sheet 207 and the second electrode sheet 215, which serve as source and drain electrodes.

[00170] FIG. 18 is a top view of a structure usable in a molecular sensor, wherein channels are provided for introducing a fluid to pairs of electrode sheets according to an embodiment. In the example of FIG. 18, each chip 232 provides a separate channel with a group of pairs of electrode sheets 206, separated by a wall 228. A fluid such as a gas or liquid containing the molecules to be tested can then be introduced into the channel so that multiple pairs of electrode sheets can be used to test the molecules in the fluid. In FIG. 18, each channel is loaded with a fluid containing a different DNA nucleobase for detection via the pairs of electrode sheets 206 in the channel.

[00171] The arrangement shown in FIG. 18 can ordinarily allow for error correction or compensation by loading the same fluid to be tested (e.g., a fluid with molecules 10, 12, 14, or 16 in FIG. 18) across multiple pairs of electrode sheets 206 and using the different measurements for the different pairs of electrode sheets to average out any error and/or eliminate a measurement that deviates by more than a threshold. Although three pairs of electrode sheets are shown per channel in the example of FIG. 18, a different number of pairs can be used in different implementations, such as ten or twenty pairs of electrode sheets per channel.

[00172] In some implementations, the arrangement shown in FIG. 18 may further comprise one or more dielectric cover layers similar to the dielectric cover layer 124 in FIG. 17 discussed above. The dielectric cover layer or layers can be deposited at an angle to or perpendicular to the electrode sheets on the surface of the chips 232 to expose only a narrow gap portion of the electrode sheets for molecular sensing. [00173] The structures usable for molecular sensor devices and fabrication methods discussed above for these structures provide numerous advantages that are not provided by the structures within previous molecular sensors and the fabrication methods used to make them. For example, the structures disclosed above do not require nano-fabrication, positioning, and adhesion of conductive islands. Conventional molecular sensors typically include structures comprising a pair of thin film electrodes facing each other in a horizontally linear configuration, with a conductive island (e.g., a gold island of 3 to 10 nm) that is transported and placed at a specific location on each electrode, or nano-pattern fabricated on each electrode. The size, adhesion strength, and positioning of such conductive islands can critically affect the performance, reliability, and yield of such conventional molecular sensors, especially in the case of genome sequencing. In some cases, the conductive islands may even fall off of the electrodes.

[00174] In contrast, the structures disclosed herein do not require nano-fabrication, adhesion, or precise positioning of conductive islands. As a result, the problems associated with the variability of conductive island size, positioning, and adhesion strength are generally avoided.

[00175] As another advantage, the arrangement of electrode sheets discussed above ordinarily allows for a much higher electrical conductance as compared to previous thin film sensor devices. This higher electrical conductance can provide an improved signal- to-noise ratio.

[00176] As yet another advantage, the disclosed processes and resulting structures for sensors provide better control of the size of the exposed area for attachment of a molecule on the electrodes themselves. As discussed above, the use of cover layers can accurately control the size of the location for molecule attachment, which can help ensure that only a single molecule attaches to the exposed area. The foregoing processes also provide a more accurate control of the dielectric layer thickness between the electrodes, which can facilitate a higher device yield.

[00177] Further, the fabrication processes disclosed herein provide simplicity and lower cost over conventional fabrication processes for structures in molecular sensors. The multilayer deposition and planarization processes discussed above can also allow for fabrication of thousands or more massively parallel device arrays.

[00178] EXAMPLES

[00179] FIGS. 19A-19C and FIGS. 20A and 20B illustrate structures produced by a fabrication process in accordance to the present disclosure. The fabrication process is used to make one embodiment of a layered electrode structure. Electron microscope images are provided of the initial substrate and final planarized structure to show the viability of the methods herein.

[00180] The upper portion of FIG. 19A provides a schematic illustration of a structure comprising parallel Si ridges on a flat substrate. The ridges in this illustration are equivalent to the "protrusions" 104, illustrated in, for example, FIGS. 1A-1C and FIGS. 2A-2C, amongst other figures. As discussed herein, a fabrication process for producing a structure usable in a molecular sensor begins with a nano-scale flat substrate, such as a Si wafer optionally coated with a S1O2 layer. The structure with ridges illustrated in the upper portion of FIG. 19A was prepared by using nanoimprint lithography. PMMA resist was patterned by spin-coat with a nanoimprint mold, such that a parallel series of rows were protected by resist. Reactive Ion Etching (RIE) was then used to etch down approximately 300 nm of material not protected by the resist, leaving a series of raised Si ridges measuring approximately 100 nm wide and spaced apart at a pitch of about 100 nm. Confirmation of the structure thus formed is provided by the SEM image of the finished Si substrate in the lower portion of FIG. 19A. [00181] Using the structure of FIG. 19A as a substrate, OAD was performed at an angle of 45° as illustrated in FIG. 19B, alternating layers of S1O2 and gold (Au), with the first S1O2 layer measuring about 50 nm thick and the subsequent layers about 10 nm thick. There were 20 alternating layers of 10 nm S1O2 and Au deposited.

[00182] The resulting multilayer structure of FIG. 19B was then planarized to yield the structure illustrated schematically in the upper portion of FIG 19C. Planarization was accomplished by finely polishing the upper surface, using polishing compound for TEM microscopy, to expose on the top surface alternating strips measuring about 10 nm-wide. The structure resulting from planarization comprises gold (Au) electrodes separated by 10 nm-wide S1O2 insulating spacers. Confirmation of the structure thus formed is provided by the SEM image of the planarized structure in the lower portion of FIG. 19C.

[00183] FIG. 20A sets forth an SEM image obtained by imaging down onto a step edge of the structure from FIG. 20C. Transmission Electron Microscopy (TEM) and Scanning Transmission Electron Microscopy (STEM) images looking down on this top surface are provided in FIG. 20B, clearly showing the alternating surface-exposed strips of Au and S1O2 in this resulting layered electrode structure.

[00184] The foregoing description of the disclosed example embodiments is provided to enable any person of ordinary skill in the art to make or use the embodiments in the present disclosure. Various modifications to these examples will be readily apparent to those of ordinary skill in the art, and the principles disclosed herein may be applied to other examples without departing from the present disclosure. The described embodiments are to be considered in all respects only as illustrative and not restrictive, and the scope of the disclosure is therefore indicated by the following claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.