CROSS-REFERENCE and REFERENCE TO RELATED APPLICATIONS

[0001] This PCT International Patent Application claims priority to U.S. Provisional Patent Application Serial No. 62/732,472 filed September 17, 2018, the contents of which is incorporated by reference herein in its entirety.

TECHNICAL FIELD OF THE INVENTION

[0002] The present invention relates to methods of making a high efficiency compact slotted antenna with an ground plane from one or two photodefmable glass substrate wafers.

BACKGROUND OF THE INVENTION

[0003] Without limiting the scope of the invention, its background is described in connection with high efficiency compact slotted antenna.

[0004] A slot antenna consists of a metal surface, usually a flat plate, with one or more holes or slots cut out of a metal substrate/ground plane. In general, these slots are about are about l/4 long with a centers to center spacing of l/2 separation. The emitter or source is generally placed l/4 from the first slot and the center of the last slot is l/4 from the end or reflector of the waveguide. The reflector or end of waveguide requires a precision of ~ l/10. A one- centimeter wavelength requires a reflector placement precision of one millimeter. The widths of the slots are much less than the wavelength of the emission. The shape and size of the slot, as well as the driving frequency, determine the radiation pattern. Slot antennas are widely used in radar antennas in marine radar, cell phone base stations, and desktop microwave sources for research and calibration purposes. Figure 4 shows two commercial versions of a slot antenna. A slot antenna's main advantages are its design simplicity and convenient adaptation to mass production for frequencies between 1 GHz and 25 GHz. The most common slotted waveguide resembles that shown in Figure 1. Figure 1 shows the center-to-center spacing of slots is l/2, the termination of the waveguide is l/4 from the center of the last slot with a precision of l/10, the width of the slots are « l. The width of the waveguide is approximately the free space wavelength (l) of the emission and the height of the waveguide is l/10. You can see that at 1 GHz or wavelength of 29.9 cm up to a frequency of 25 GHz or wavelength of 1.19 cm classic computer numerical control (CNC) tools have sufficient precision to create slotted. However at 100 GHz or wavelength of 0.299 cm requires a transverse slot dimension « l on the order of 0.003 cm (1.1 mil). A modem CNC tool has a precision of 0.01 cm +/- 0.01 cm or ~3.9 mil +/- 0.4 mil. Clearly at higher frequencies or shorter wavelengths the ability to use classical CNC machining becomes unrealizable.

SUMMARY OF THE INVENTION

[0005] Slotted antenna are consider simple to fabricate using classic machining techniques at frequencies between 600 MHz and 25 GHz. Above 30 GHz the precision and feature size for making the slots, waveguides, and frequency launching elements. As an example, the center-to-center spacing at a frequency of 100 GHz is l/2 or 1.5 mm, the termination of the waveguide is l/4 or 750pm from the center of the last slot with a precision of l/10 or 150 pm, the width of the slots are « l or 150pm, the width of the waveguide is approximately the free space wavelength (l or 3mm) of the emission and the height of the waveguide is l/10 or 150 pm. The level of precision required for slot antenna exceeds classic CNC machining capability to produce low cost high quality slotted antenna. However printed circuit board (PCB) and/or semiconductor processing technology the ability to produce feature sizes much less than a micrometer. The materials used in PCB and semiconductor technology are electronically lossy i.e; they have a high loss tangent and not support the creation or production of an efficient low cost slot antenna. DuPont has shown the use of a LTCC (low temperature co-fired ceramic) multilayer slotted antenna. The LTCC antenna was prototyped by etching pattern green (unfired/sintered) ceramic and then filling the pattern with a refractory metal. The cavity of the antenna consisted of the ceramic material. The individual layers of the green LTCC were then hand assembled much like a deck of cards and then sintered/fired to form a slotted antenna. The green ceramic shrinks about 8.5% in the plane direction of the ceramic when fired/sintered. The shrinkage causes stress and misalignment of the individual elements of the slotted antenna. This LTCC slotted antenna had reasonable performance but was determined not to be cost effective. The RF properties for LTCC include a loss tangent of 0.0012 and a dielectric constant of 7.1 +/-0.2. Several of the devices were prototyped and tested. These values for the loss tangent and dielectric constant are good compared to other efforts to make a miniature slotted antenna but they fall into the poor category when compared to large slotted antennas that have air as the dielectric media. Air has a loss tangent of 0.00 and a dielectric constant of 1.00059. Unfortunately, the yield and performance of the ceramic prevented the LTCC slotted antenna technology form being viable. Classic MEMS based processing is not able to produce a viable technical approach due to the inherent stress from the thick deposition in the materials that are added or subtracted. Thin films have stress building up from the deposition process that is sufficient to cause a delamination in thicker device structures. The present invention is a photodefmable glass based slotted antenna that uses air as its dielectric media using semiconductor/printed circuit board (PCB) processing in a photodefmable glass and low stress electroplating metallization technology.

[0006] In one embodiment, the present invention includes a method of making a slotted waveguide antenna structure with matched ground plane comprising: forming in a photosensitive glass substrate a coaxial-to-coplanar waveguide (CPW) section connected to a power divider that is connected to an emission cavity area for the slotted antenna and one or more vias; depositing a metal ground plane to a first surface of the photosensitive glass substrate; depositing a copper layer on the photosensitive glass substrate with a pattern of slots that form a slot antenna above the emission cavity; forming one or more copper pillars in the emission cavity under the slot antenna; etching away the photosensitive glass in the emission cavity while retaining the one or more copper pillars; connecting a micro coaxial connector to the coaxial-to-coplanar waveguide (CPW) section; and one or more solder bumps at the vias that connect to the ground plane, to form a slotted antenna. In one aspect, the photodefmable glass substrate is a glass substrate comprising a composition of: 60 - 76 weight % silica; at least 3 weight % K ₂ 0 with 6 weight %- 16 weight % of a combination of K ₂ 0 and Na ₂ 0; 0.003-1 weight % of at least one oxide selected from the group consisting of Ag ₂ 0 and Au ₂ 0; 0.003-2 weight % Cu ₂ 0; 0.75 weight % - 7 weight %B ₂ 0 ₃ . and 6 - 7 weight % A1 ₂ 0 ₃ : with the combination of B ₂ 0 ₃ ; and Al ₂ 0 ₃ not exceeding 13 weight %; 8-15 weight % Li ₂ 0; and 0.001 - 0.1 weight % Ce0 ₂ . In another aspect, the photodefmable glass substrate is a glass substrate comprising a composition of: 35 - 76 weight % silica, 3- 16 weight % K ₂ 0, 0.003-1 weight % Ag ₂ 0, 8-15 weight % Li ₂ 0, and 0.001 - 0.1 weight % Ce0 ₂ . In another aspect, the photodefmable glass substrate is at least one of: a photo- definable glass substrate comprises at least 0.1 weight % Sb ₂ 0 ₃ or As ₂ 0 ₃ ; a photo- definable glass substrate comprises 0.003-1 weight % Au20; a photo-definable glass substrate comprises 1-18 weight % of an oxide selected from the group consisting of CaO, ZnO, PbO, MgO, SrO and BaO; and optionally has an anisotropic-etch ratio of exposed portion to said unexposed portion is at least one of 10-20:1; 21-29: 1; 30-45: 1; 20-40: 1; 41-45:1; and 30-50:1. In another aspect, the photodefmable glass substrate is a photosensitive glass ceramic composite substrate comprising at least one of silica, lithium oxide, aluminum oxide, or cerium oxide. In another aspect, the method further comprises dicing one or more of the slotted antennas from the photodefmable glass substrate into individual sloted antennas. In another aspect, the sloted antenna comprises one or more slot openings above a cavity, wherein the sloted portion of the antenna is supported with one or more glass or copper pillars in the cavity.

[0007] In another embodiment, the present invention includes a two-wafer method of making a sloted antenna comprising: forming on a first surface of a first photodefmable glass substrate wafer: one or more copper support pillars in a cavity, one or more outside walls for the cavity, and a copper via for connecting a micro axial connector, and on a second surface of a first photodefmable glass substrate wafer a copper layer that comprises one or more antenna slots; forming on a first surface of a second photodefmable glass substrate wafer: a micro axial connector and power divider section, a resonator cavity, side walls, and one or more support structures in the resonator cavity; and placing solder balls along a metal surface of an emission cavity sloted antenna section, the support structures in the cavity, a power divider section, and a coaxial-to-coplanar waveguide (CPW) of at least one of the first or second photodefmable glass substrate wafers; aligning the first and second photodefmable glass substrate wafers at the sloted antenna; and compressing the first or second photodefmable glass substrate wafers at a temperature sufficient to flow the solder balls to connect the support structures in the cavity, a power divider section, and a coaxial- to-coplanar waveguide of the first and second photodefmable glass substrate wafers; and forming a sloted antenna on a surface of the second photodefmable glass substrate wafer opposite the cavity in the first photodefmable glass substrate wafer. In one aspect, the photodefmable glass substrate is a glass substrate comprising a composition of: 60 - 76 weight % silica; at least 3 weight % K ₂ 0 with 6 weight %- 16 weight % of a combination of K ₂ 0 and Na ₂ 0; 0.003-1 weight % of at least one oxide selected from the group consisting of Ag ₂ 0 and Au ₂ 0; 0.003-2 weight % Cu ₂ 0; 0.75 weight % - 7 weight %B ₂ 0 ₃ , and 6 - 7 weight % Al ₂ 0 ₃ ; with the combination of B ₂ 0 ₃ ; and Al ₂ 0 ₃ not exceeding 13 weight %; 8-15 weight % Li ₂ 0; and 0.001 - 0.1 weight % Ce0 ₂ . In another aspect, the photodefmable glass substrate is a glass substrate comprising a composition of: 35 - 76 weight % silica, 3- 16 weight % K ₂ 0, 0.003-1 weight % Ag ₂ 0, 8-15 weight % Li ₂ 0, and 0.001 - 0.1 weight % Ce0 ₂ . In another aspect, the photodefmable glass substrate is at least one of: a photo defmable glass substrate comprises at least 0.1 weight % Sb ₂ 0 ₃ or As ₂ 0 ₃ ; a photo- definable glass substrate comprises 0.003-1 weight % Au20; a photo-definable glass substrate comprises 1-18 weight % of an oxide selected from the group consisting of CaO, ZnO, PbO, MgO, SrO and BaO; and optionally has an anisotropic-etch ratio of exposed portion to said unexposed portion is at least one of 10-20: 1; 21-29: 1; 30-45: 1; 20-40: 1; 41-45: 1; and SO SO: !. In another aspect, the photodefmable glass substrate is a photosensitive glass ceramic composite substrate comprising at least one of silica, lithium oxide, aluminum oxide, or cerium oxide. In another aspect, the method further comprises dicing one or more of the slotted antennas from the photodefmable glass substrate into individual slotted antennas. In another aspect, the slotted antenna comprises one or more slot openings above a cavity, wherein the slotted portion of the antenna is supported with one or more glass or copper pillars in the cavity.

[0008] In yet another embodiment, the present invention includes a method of making a slotted waveguide antenna structure with matched ground plane comprising: (1) masking a design layout comprising one or more structures to form one or more electrical conduction paths on a photodefmable glass substrate; (2) exposing at least one portion of the photosensitive glass substrate to an activating energy source to expose one or more sidewalls and one or more support elements of an antenna structure; (3) processing the photosensitive glass substrate to a heating phase above its glass transition temperature to convert a portion of the photodefmable glass substrate exposed the activating energy source into a ceramic, wherein the portion of the photodefmable glass formed into a ceramic comprises an outside, inside walls, and at least one via of the antenna structure; (4) depositing a layer of tantalum and a layer of copper on a first side of the photodefmable glass substrate; (5) coating the photodefmable glass substrate with a photoresist to form an interior of a coaxial-to-coplanar waveguide (CPW) connected to a power divider that is connected to an emission cavity for the slotted antenna; (6) etching one or more sidewalls and one or more support vias in the substrate; (7) depositing a photoresist the protects the coaxial-to- coplanar waveguide (CPW) and the power divider; (8) exposing the photosensitive glass substrate to an activating energy source to expose the emission cavity for a time sufficient to form the cavity without crossing the wafer; (9) removing the photoresist and processing the photosensitive glass substrate to a heating phase above its glass transition temperature to convert the photodefmable glass substrate exposed to the activating energy source into a ceramic; (10) coating and exposing a photoresist on a second side of the photodefmable glass substrate with a pattern of slots that form a slot antenna; (11) depositing a layer of tantalum and a layer of copper on the second side of the photodefmable glass substrate; (12) removing the photoresist and electroplating with copper the photodefmable glass substrate; (13) coating the photodefmable glass substrate with a photoresist except for the portion of the emission cavity, and exposing the power divider and coaxial to CPW sections; (14) etching a portion of the photodefmable glass substrate formed into a ceramic for a time sufficient to form the emission cavity, without traversing the photodefmable glass substrate; (15) rinsing the wafer with water or a solvent; (16) using a projection aligner exposing a region with a pattern to form one or more glass pillars or glass pillar regions in the emission cavity; (17) coating the photodefmable glass substrate to silver nitrate and reducing the silver nitrate to metallic silver on the photodefmable glass substrate with an infrared source on the power divider and coaxial to CPW sections; (18) electroless plating copper on the metallic silver; (19) heating the photodefmable glass substrate to at least 250°C in argon to adhere the copper to the silver; (20) etching with a spin on glass Si0 ₂ with a plasma etching process to expose the copper sidewalls around the power divider and coaxial to CPW sections; (21) plasma etching down to one or more copper sidewalls; (22) coating the photodefmable glass substrate with photoresist and open the region over the spin on glass over where a contact tab for the power divider and coaxial to CPW sections and plasma etching down to a copper tab; (23) removing the photoresist using a standard stripper the rinse with water; (24) coating the photodefmable glass substrate with a photoresist clearing a pattern over the power divider;

(25) sputtering coating the photodefmable glass substrate with tantalum and then copper;

(26) electroless plating copper on the sputtered copper; (27) removing the photoresist and rinsing the photodefmable glass substrate with water; (28) depositing a solder bump with an ink jet printer to form an electrical contact with a center electrode of a micro coaxial connector of the coaxial to CPW element; (29) heating the photodefmable glass substrate to allow the solder bump to flow making a solid electrical and mechanical connection from the electrical contact of the coaxial to CPW element; (30) rinsing the wafer in 10% HF, to remove all of the remain ceramic material and spin on glass from the antenna cavity; (31) rinsing the wafer with water and alcohol; and (32) depositing a solder bump bond with an inkjet deposition process at a perimeter of the slotted antenna to make contact with a ground plane and to attach the micro coaxial connector to the photodefmable glass substrate; and at the center electrode of the micro coaxial connector to the coax to CPW element; (33) attaching a surface mount micro coaxial connector to the solder bumps, to provide a coaxial connector to the slotted antenna. In one aspect, the activating energy source is a UV light. In another aspect, the photodefmable glass substrate is a glass substrate comprising a composition of: 60 - 76 weight % silica; at least 3 weight % K ₂ 0 with 6 weight %- 16 weight % of a combination of K ₂ 0 and Na ₂ 0; 0.003-1 weight % of at least one oxide selected from the group consisting of Ag ₂ 0 and Au ₂ 0; 0.003-2 weight % Cu ₂ 0; 0.75 weight % - 7 weight %B ₂ 0 ₃ , and 6 - 7 weight % Al ₂ 0 ₃ ; with the combination of B ₂ 0 ₃ ; and Al ₂ 0 ₃ not exceeding 13 weight %; 8-15 weight % Li ₂ 0; and 0.001 - 0.1 weight % Ce0 ₂ . In another aspect, the photodefmable glass substrate is a glass substrate comprising a composition of: 35 - 76 weight % silica, 3- 16 weight % K ₂ 0, 0.003-1 weight % Ag ₂ 0, 8-15 weight % Li ₂ 0, and 0.001 - 0.1 weight % Ce0 ₂ . In another aspect, the photodefmable glass substrate is at least one of: a photo-definable glass substrate comprises at least 0.1 weight % Sb ₂ 0 ₃ or As ₂ 0 ₃ ; a photo- definable glass substrate comprises 0.003-1 weight % Au20; a photo-definable glass substrate comprises 1-18 weight % of an oxide selected from the group consisting of CaO, ZnO, PbO, MgO, SrO and BaO; and optionally has an anisotropic-etch ratio of exposed portion to said unexposed portion is at least one of 10-20:1; 21-29: 1; 30-45: 1; 20-40: 1; 41- 45:1; and 30-50: 1. In another aspect, the photodefmable glass substrate wafer is a photosensitive glass ceramic composite substrate comprising at least one of silica, lithium oxide, aluminum oxide, or cerium oxide. In another aspect, the method further comprises dicing one or more of the slotted antennas from the first and second photodefmable glass substrate wafers into individual slotted antennas. In another aspect, the slotted antenna comprises one or more slot openings above a cavity, wherein the slotted portion of the antenna is supported with one or more glass or copper pillars in the cavity formed between the first and second photodefmable glass substrate wafers.

[0009] In yet another embodiment, the present invention includes a two-wafer method of making a slotted antenna comprising: (1) processing a first photodefmable glass substrate wafer by: depositing a photoresist or wax on a first surface of a first photodefmable glass substrate wafer; exposing a pattern on the first photodefmable glass substrate wafer to expose one or more sides of an emission cavity, one or more vias, and one or more support structures of an antenna structure; thermally cycling the first photodefmable glass substrate wafer to convert the exposed material to a ceramic; coating, exposing and developing a photoresist on the first side of the first photodefmable glass substrate wafer into slots for RF emissions; depositing tantalum and copper on the photoresist by sputtering on the first surface of the first photodefmable glass substrate wafer; electroplating copper on the first photodefmable glass substrate wafer; coating the first surface of the first photodefmable glass substrate wafer with a wax, a photoresist or other protective coating; etching the one or more vias and the one or more support structures; electroplating the one or more vias and the one or more support structures and the one or more sidewalls of the antenna; performing chemical-mechanical polishing of a second surface of the first photodefmable glass substrate wafer opposite the first surface of the first photodefmable glass substrate wafer; exposing the emission cavity to an activating energy to expose the emission cavity, a power divider and a coaxial-to-coplanar waveguide (CPW) section; thermally cycling the first photodefmable glass substrate wafer to convert the exposed material to a ceramic phase; (2) processing a second photodefmable glass substrate wafer by: forming on a first surface of the second photodefmable glass substrate wafer a micro coaxial connector and power divider section with a photo mask; exposing one or more sidewalls of an emission cavity, and one or more support structures; thermally cycle the second photodefmable glass substrate wafer to convert the exposed material to a ceramic phase; coating, exposing and developing a photoresist on a second surface of the second photodefmable glass substrate wafer substrate with a pattern for an external copper slotted antenna; depositing tantalum and copper on the photoresist by sputtering on the first surface of the second photodefmable glass substrate wafer; removing the photoresist using a standard stripper and electroplating copper on the second photodefmable glass substrate wafer; coating a second surface of the second photodefmable glass substrate wafer with a wax, a photoresist or other protective coating; etching the one or more sidewalls and one or more support pillars; electroplating the one or more pillars and one or more sidewalls from the copper on the first surface of the second photodefmable glass substrate wafer; rinsing with water and drying the second photodefmable glass substrate wafer; flattening a second surface of the second photodefmable glass substrate wafer my chemical-mechanical polishing; coating, exposing and developing a photoresist on the first surface of the second photodefmable glass substrate wafer to shield the micro coaxial connector power divider section; exposing the second photodefmable glass substrate wafer to an activating energy; thermally cycling the second photodefmable glass substrate wafer to convert the exposed material to a ceramic phase; depositing tantalum and copper on the photoresist by sputtering on the first surface of the second photodefmable glass substrate wafer; removing the photoresist using a standard stripper and electroplating copper on the second photodefmable glass substrate wafer to expose the openings; and (3) connecting the first and second photodefmable glass substrate wafers, by: placing solder balls on the copper elements of the front surface of the first photodefmable glass substrate wafer; using alignment fiducials and etched keyed structure to align the first and second photodefmable glass substrate wafers; compressing the first and second photodefmable glass substrate wafers to keep the alignment; heating the aligned first and second photodefmable glass substrate wafers to flow the solder into a solid electrical and mechanical connection at the coax to CPW element; coating the joined first and second photodefinable glass substrate wafers with photoresist to expose the slot patterns; coating a second side of the first and second photodefinable glass substrate wafers with wax, photoresist or other material to protect the first and second photodefinable glass substrate wafers; etching the joined first and second photodefinable glass substrate wafers to remove the ceramic phase from the resonator, power divider and coax to CPW sections; removing the photoresist; exposing the one or more slot patterns on the joined first and second photodefinable glass substrate wafers; and etching the joined first and second photodefinable glass substrate wafers to open the one or more slot patterns. In one aspect, at least one of the first and second photodefinable glass wafers is a glass substrate comprising a composition of: 60 - 76 weight % silica; at least 3 weight % K ₂ 0 with 6 weight %- 16 weight % of a combination of K ₂ 0 and Na ₂ 0; 0.003-1 weight % of at least one oxide selected from the group consisting of Ag ₂ 0 and Au ₂ 0; 0.003-2 weight % Cu ₂ 0; 0.75 weight % - 7 weight %B ₂ 0 ₃ , and 6 - 7 weight % Al ₂ 0 ₃ ; with the combination of B ₂ 0 ₃ ; and Al ₂ 0 ₃ not exceeding 13 weight %; 8-15 weight % Li ₂ 0; and 0.001 - 0.1 weight % Ce0 ₂ . In another aspect, at least one of the first and second photodefinable glass wafers is a glass substrate comprising a composition of: 35 - 76 weight % silica, 3- 16 weight % K ₂ 0, 0.003-1 weight % Ag ₂ 0, 8-15 weight % Li ₂ 0, and 0.001 - 0.1 weight % Ce0 ₂ . In another aspect, at least one of the first and second photodefinable glass wafers is at least one of: a photo-definable glass substrate comprises at least 0.1 weight % Sb ₂ 0 ₃ or As ₂ 0 ₃ ; a photo- definable glass substrate comprises 0.003-1 weight % Au20; a photo-definable glass substrate comprises 1-18 weight % of an oxide selected from the group consisting of CaO, ZnO, PbO, MgO, SrO and BaO; and optionally has an anisotropic-etch ratio of exposed portion to said unexposed portion is at least one of 10-20: 1; 21-29: 1; 30-45: 1; 20-40: 1; 41-45: 1; and 30-50: 1.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] For a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures and in which:

[0011] FIG. 1 shows a typical layout for a slotted antenna.

[0012] FIG. 2 shows a miniature air cavity slotted antenna.

[0013] FIG. 3 shows a cross section miniature air cavity slotted antenna.

[0014] FIG. 4A shows a moderate size CNC machined metal air cavity slotted antenna. [0015] FIG. 4B shows a small CNC machined metal air cavity slotted antenna.

[0016] FIGS. 5A to 5L show an example of a method for making a single wafer slotted waveguide antenna structure with matched ground plane and/or RF isolation structure, and FIG. 6L shows a cross-sectional view of the final matched ground plane and/or RF isolation structure.

[0017] FIGS. 6A to 61 show an example of a method for making a two wafer slotted waveguide antenna structure with matched ground plane and/or RF isolation structure, and FIG. 6J shows a cross-sectional view of the final, two wafer matched ground plane and/or RF isolation structure.

[0018] FIG. 7 is a flow chart of another method of the present invention for making a slotted waveguide antenna structure with matched ground plane and/or RF isolation structure.

DETAILED DESCRIPTION OF THE INVENTION

[0019] While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention.

[0020] To facilitate the understanding of this invention, a number of terms are defined below. Terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention. Terms such as“a”,“an” and “the” are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terminology herein is used to describe specific embodiments of the invention, but their usage does not limit the invention, except as outlined in the claims.

[0021] The present invention relates to creating a compact air cavity slotted antenna with a 50 Ohm launch and mini coaxial cable connector. Compact low loss air cavity slotted antennae are critical elements for high efficiency RF communication systems. Compact air cavity slotted antenna is a cornerstone technological requirement for future RF systems for portable systems, base station, test equipment and point-to-point communication.

[0022] Photosensitive glass structures have been suggested for a number of micromachining and microfabrication processes such as integrated electronic elements in conjunction with other elements systems or subsystems. Semiconductor microfabrication using thin film additive and subtractive processes on semiconductor, insulating or conductive substrates is expensive with low yield and a high variability in performance. This invention provides a cost effective glass ceramic air cavity slotted antenna device or as an array of air cavity slotted antenna for RF frequencies with low loss.

[0023] FIG. 1 shows a typical layout for a slotted antenna. FIG 2 shows a miniature air cavity slotted antenna. FIG 3 shows a cross section miniature air cavity slotted antenna. FIG 4A shows a moderate size CNC machined metal air cavity slotted antenna. FIG 4B shows a small CNC machined metal air cavity slotted antenna. FIGS. 4A and 4B show a classic air cavity slotted antenna that could made using classic CNC machining. FIG. 2 shows the top view of a theoretical structure for a compact air cavity slotted antenna. FIGS. 3 shows the cross section view of a theoretical structure for a compact air cavity slotted antenna a theoretical structure of a compact air cavity slotted antenna. The external dimensions of the compact air cavity slotted antenna are: 8 (1) x 5.0 (w) x 0.4 (h) mm ³ . FIGS. 4A and 4B shows images of commercial slotted air cavity slotted antennas.

[0024] Traditional slotted air cavity slotted antenna use traditional machining and finishing techniques because of the relatively large spacing slotted air cavity antenna. Traditional slotted air cavity slotted antenna used precision machining metal and electropolished for surface finish easily produce and are self-supporting antenna due to the thickness of the metal structures. Thin film or additive/subtractive manufacturing technology produce resonate elements that are not mechanically or dimensionally stable. This mechanical or dimensional instability forced the use of a solid dielectric substrate/cavities creating large losses. This large amount of loss has precluded the development and production of a slotted air cavity antenna for commercial markets.

[0025] The width is a multiple of the free space wavelength of the emission frequency. The center-to-center spacing between the slots of l/2.

[0026] The present invention includes a method to fabricate to compact slotted air cavity antenna photodefinable glass ceramic substrate. To produce the present invention the inventors developed a glass ceramic (APEX ^® Glass ceramic) as a novel packaging and substrate material for semiconductors, RF electronics, microwave electronics, and optical imaging. APEX ^® Glass ceramic is processed using first generation semiconductor equipment in a simple three step process and the final material can be fashioned into either glass, ceramic, or contain regions of both glass and ceramic. Photo-etchable glasses have several advantages for the fabrication of a wide variety of microsystems components. Although the current embodiment has been demonstrated in APEX glass due to it superior processing attributes but could be practice on other forms of photodefmable glass or by additive and subtractive thin film processes. The APEX glass approach has the lowest cost highest preforming slotted antennas.

[0027] Microstructures have been produced relatively inexpensively with these glasses using conventional semiconductor processing equipment. In general, glasses have high temperature stability, good mechanical an d electrically properties, and have better chemical resistance than plastics and many metals. Photoetchable glass is comprised of lithium-aluminum-silicate glass containing traces of silver ions. When exposed to UV-light within the absorption band of ceriumoxide, the ceriumoxide acts as sensitizers, absorbing a photon and losing an electron that reduces neighboring silver oxide to form silver atoms, e.g.,

3+ + 4+ 0

Ce +Ag = Ce +Ag

[0028] The silver atoms coalesce into silver nanoclusters during the baking process and induce nucleation sites for crystallization of the surrounding glass. If exposed to UV light through a mask, only the exposed regions of the glass will crystallize during subsequent heat treatment.

[0029] This heat treatment must be performed at a temperature near the glass transformation temperature (e.g., greater than 465°C. in air). The crystalline phase is more soluble in etchants, such as hydrofluoric acid (HF), than the unexposed dvitreous, amorphous regions. The crystalline regions etched greater than 20 times faster than the amorphous regions in l0%HF, enabling microstructures with wall slopes ratios of about 20: 1 when the exposed regions are removed. See T.R.Dietrichetal., "Fabrication Technologies for Microsystems utilizing Photoetchable Glass”, Microelectronic Engineering 30,497 (1996), which is incorporated herein by reference.

[0030] In general, photoetchable glass and is composed of silicon oxide (Si0 ₂ ) of 75-85% by weight, lithium oxide (Li ₂ 0) of 7-11% by weight, aluminum oxide (ATO,) of 3-6% by weight, sodium oxide (Na ₂ 0) of 1-2% by weight, 0.2-0.5% by weight antimonium trioxide (Sb ₂ 0 ₃ ) or arsenic oxide (As ₂ Cf). silver oxide (Ag ₂ 0) of 0.05-0.15% by weight, and cerium oxide (Ce0 ₂ ) of 0.01- 0.04% by weight. As used herein the terms“APEX® Glass ceramic”, “APEX glass” or simply“APEX” is used to denote one embodiment of the glass ceramic composition of the present invention.

[0031] The APEX composition provides three main mechanisms for its enhanced performance: (1) The higher amount of silver leads to the formation of smaller ceramic crystals which are etched faster at the grain boundaries, (2) the decrease in silica content (the main constituent etched by the HF acid) decreases the undesired etching of unexposed material, and (3) the higher total weight percent of the alkali metals and boronoxide produces a much more homogeneous glass during manufacturing.

[0032] The present invention includes a method for fabricating a low loss RF Filter structure in APEX Glass structure for use in forming interdigitated structures with mechanical stabilization and electrical isolation in a glass ceramic material used. The present invention includes metal structures to create in multiple planes of a glass-ceramic substrate, such process employing the (a) exposure to excitation energy such that the exposure occurs at various angles by either altering the orientation of the substrate or of the energy source, (b) a bake step and (c) an etch step. The slotted structures can be either symmetric or asymmetric. The mechanically stabilized structures are difficult, if not infeasible to create in most glass, ceramic, silicon substrates or other substrates. The present invention has created the capability to create such structures in both the vertical as well as horizontal plane for glass- ceramic substrates.

[0033] Ceramicization of the glass is accomplished by exposing a region of the APEX Glass substrate to approximately 20J/cm ² of 3l0nm light. In one embodiment, the present invention provides a quartz/chrome mask containing a variety of concentric circles with different diameters.

[0034] The present invention includes a method for fabricating a compact efficient RF filters using mechanically stabilized interdigitated resonate structures connect different electronic devices fabricated in or attached to the photosensitive glass. The photosensitive glass substrate can have a wide number of compositional variations including but not limited to: 60 - 76 weight % silica; at least 3 weight % K ₂ 0 with 6 weight % - 16 weight % of a combination of K ₂ 0 and Na ₂ 0; 0.003-1 weight % of at least one oxide selected from the group consisting of Ag ₂ 0 and Au ₂ 0; 0.003-2 weight % Cu ₂ 0; 0.75 weight % - 7 weight % B ₂ 0„ and 6 - 7 weight % A1 ₂ 0 ₃ : with the combination of B ₂ 0 ₃ ; and Al ₂ 0 ₃ not exceeding 13 weight %; 8-15 weight % Li ₂ 0; and 0.001 - 0.1 weight % Ce0 ₂ . This and other varied compositions are generally referred to as the APEX glass. [0035] The exposed portion may be transformed into a crystalline material by heating the glass substrate to a temperature near the glass transformation temperature. When etching the glass substrate in an etchant such as hydrofluoric (HF) acid, the anisotropic-etch ratio of the exposed portion to the unexposed portion is at least 30: 1 when the glass is exposed to a broad spectrum mid-ultraviolet (about 308-3 l2nm) flood lamp to provide a shaped glass structure that have an aspect ratio of at least 30: 1, and to provide a lens shaped glass structure. The exposed glass is then baked typically in a two-step process. Temperature range heated between of 420°C-520°C for between 10 minutes to 2 hours, for the coalescing of silver ions into silver nanoparticles and temperature range heated between 520°C-620°C for between 10 minutes and 2 hours allowing the lithiumoxide to form around the silver nanoparticles. The glass plate is then etched. The glass substrate is etched in an etchant, of HF solution, typically 5% to 10% by volume, where in the etch ratio of exposed portion to that of the unexposed portion is at least 30: 1. Create the mechanically and thermally stabilized slot antenna resonate structure through thin film additive and subtractive processes requires the general processing approach.

[0036] There are multiple methods considered by the inventors to achieve a slotted antenna in photodefinable glass. One such embodiment uses a single wafer to create the slotted antenna. A second embodiment considered by the inventors uses a dual wafer structure to create the slotted antenna.

[0037] The present inventors used a photo-definable glass ceramic (APEX®) Glass Ceramic or other photo definable glass as a novel substrate material for semiconductors, RF electronics, microwave electronics, electronic components and/or optical elements. In general, a photo definable glass is processed using first generation semiconductor equipment in a simple three step process and the final material can be fashioned into either glass, ceramic, or contain regions of both glass and ceramic to create a slotted waveguide antenna structure with a matched ground plane comprising: forming in a photosensitive glass substrate a coaxial-to-coplanar waveguide (CPW) section connected to a power divider, an emission cavity while retaining one or more solder bumps at the vias that connect to the integrated ground plane,.

[0038] Single Wafer.

[0039] A single wafer method of making the slotted antenna section of a compact slotted air cavity antenna (CSACA) starts with a lap and polished photodefinable glass substrate is shown in FIGS. 5A to 5L. Where the substrate between 150 and 300 pm thick with a surface roughness less than or equal to 50nm and surface to surface parallel less than or equal to 10% with an RMS roughness < IOqA.

[0040] On a backside of the lapped and polished photodefmable glass wafer from, use a photomask to image at 310 nm light at a at least an intensity of 2 J/cm ² to expose the sidewalls of the slotted antenna and support elements of the emission section of the slotted antenna.

[0041] The bottom of the substrate that has been coated with Ta and Copper. Where Ta is deposited by sputter deposition at a thickness between 5qA and 750A preferably 250A. Where the copper is deposited by electroplating deposition at a thickness between lpm and 100 pm but preferably 30 pm. There are many RF CSACA die on a single 6” wafer. The specific number of die per wafer is a function of the wafer diameter and CSACA device design.

[0042] The wafer is then coated with a photoresist and the via and ground plane sidewall pattern for the CSACA is exposed and developed. The substrate is 6” in diameter is exposed with approximately 20 J/cm ² of 3l0nm light with a photo mask has a pattern of through hole via and ground plane sidewalls of the emission section CSACA device. The through hole via are between 30 pm and l20p preferably 80 pm in diameter with a center-to-center spacing between 2,000 pm and 100 pm preferably at a 500 pm center-to-center spacing. Where the ground plane sidewalls are between 500 pm and 5 pm preferably at a 50 pm thick. The photoresist is then removed using a standard photoresist stripper.

[0043] The wafer is then annealed at temperature range heated between of 420°C-520°C for between 10 minutes to 2 hours, for the coalescing of silver ions into silver nanoparticles and temperature range heated between 520°C-620°C for between 10 minutes and 2 hours allowing the lithium oxide to form around the silver nanoparticles. The wafer is then cooled and placed into an HF bath to etch the ceramic portion of the wafer.

[0044] Then the via and ground plane sidewalls are filled using a copper electroplating process. The copper electroplating process grows the via and ground plane sidewalls from the backside copper rough the substrate.

[0045] The contact area between via and bottom ground plane is about 5% of the surface area contact to the final metal CSACA structure. The greater the number of stabilization structures, the higher the RF losses. As such we elect not to make the stabilization structure greater than 50% of the contact area of the CSACA structure and preferably less than 5%. The front of the wafer is then planarized using a CMP process to remove any excess copper.

[0046] The top of the is flood exposed with approximately 20J/cm ² of 3l0nm light,, The wafer is then annealed at temperature range heated between of 420°C-520°C in argon for between 10 minutes to 2 hours, for the coalescing of silver ions into silver nanoparticles and temperature range heated between 520°C-620°C in argon for between 10 minutes and 2 hours allowing the lithium oxide to form around the silver nanoparticles. This enables the formation of the ceramic phase of the photodefmable glass.

[0047] The wafer is then cooled and covered with a photoresist where it is exposed with the desired slot pattern for the CSACA using a standard photoresist process. This leaves a photoresist pattern where the slots will be in the CSACA. The wafer is placed in a sputtering chamber where a thin layer of Ta between 5qA and 75qA preferably 25qA and a seed layer of copper between 0.5 pm and 5 pm preferably 2 pm of copper. The substrate is the placed into a photoresist stripper to leave the pattern of slots surrounded and outlined by a thin film of copper. The wafer is placed into a copper electroplating/electroless plating bath where an addition 15 pm to 50 pm preferably 25 pm is deposited on copper thin film. The wafer is then placed in a 10% HF solution where the ceramic portion is removed from the emission sections cavity. The wafer is then placed in a DI water rinse to neutralize/ dilute the HF fluid. Then the wafer is placed into, e.g., a Isopropyl Alcohol (IP A) rinse to do a fluid exchange with any water. The wafer is then placed into a vacuum bake oven to remove any residual IP A. The bake oven is at 40°C to 70°C at a preferably 50°C pressure ranging between 1 mtorr and 750 mtorr preferable 400 mtorr.

[0048] Processing the micro-coaxial cable to coplanar waveguide and power divider section are accomplished in a similar manner the emission section of the slotted antenna. The first processing step is to expose the interior of microcoaxial cable and power divider sections of the CSACA with a photo mask has a pattern of through hole via and ground plane sidewalls CSACA device.

[0049] The wafer is then placed into a copper electroplating bath where cooper is deposited at a thickness between 0.5 pm and 10 pm.

[0050] The ceramic portion of the exposed/converted glass is then etched away using 10% HF solution leaving the interdigitated, ground plane and input and output structures. The wafer is then rinsed and dried using DI water and IP A. [0051] The wafer is then annealed at temperature range heated between of 420°C-520°C for between 10 minutes to 2 hours, for the coalescing of silver ions into silver nanoparticles and temperature range heated between 520°C-620°C for between 10 minutes and 2 hours allowing the lithiumoxide to form around the silver nanoparticles. The wafer is then cooled and placed into a 10% HF bath to etch the ceramic portion of the wafer. The wafer is then placed into a CVD deposition system for a deposition between 200 A and 10,000 A thick of titanium. The wafer is then coated with a photoresist and the via pattern is exposed and developed. The wafer is then placed into a copper-electroplating bath where between 25 pm and 35 pm of copper are deposited. The photoresist is then removed lifting off the majority of the cooper and leaving the cooper filled via. The wafer is then lapped and polished to remove any excess copper and planarize the surface of the glass and cooper filled via.

[0052] The wafer is then exposed with approximately 20J/cm ² of 3l0nm light to a photo mask consisting of a rectangular pattern of ~5.3 mm by ~2.2 mm. As can be seen in FIG 7. The wafer is then annealed, in Argon at temperature range heated between of 420°C-520°C for between 10 minutes to 2 hours, for the coalescing of silver ions into silver nanoparticles and temperature range heated between 520°C-620°C for between 10 minutes and 2 hours allowing the lithium oxide to form around the silver nanoparticles. The wafer is then cooled. A photoresist is then coated on the front of the wafer and the lid pattern is exposed and developed. The remaining photoresist covers the exposed and converted ceramic. Both sides of the wafer are coated with 200 A and 10,000 A thick of titanium using CVD process. The wafer is then placed into a copper-electroplating bath where cooper is deposited at a thickness between 0.5 pm and 20 pm. The photoresist is then removed lifting off the majority of the cooper and leaving the converted ceramic exposed and any unwanted remaining seed layer is removed using any number of well-established techniques. The ceramic portion of the exposed/converted glass is then etched away using 10% HF solution leaving the ground plane structures. The wafer is then rinsed and dried using DI water and IP A. Table 1 is a detailed step-by-step example of a protocol for manufacturing the slotted antenna using in a single wafer.

[0053] Table 1. A single wafer slotted waveguide antenna structure with matched ground plane and/or RF isolation structure is created creating by:

[0054] Two Wafer method.

[0055] A two wafer method of making the slotted antenna section of a compact slotted air cavity antenna (CSACA) starts with a lap and polished photodefmable glass substrate is shown in FIGS. 6A to 6J. Where the substrate between 150 and 300 pm thick with a surface roughness less than or equal to 50nm and surface to surface parallel less than or equal to 10% with an RMS roughness < 100 A. Table 2 is one example of a two wafer transmission structure with matched ground plane and/or RF isolation structure.

[0056] Table 2. In an example of Step-by-step method of making a slotted antenna of the present invention.

_

[0057] FIG. 7 shows a flowchart 100 of the method of the present invention, in which Step 102 includes make a ceramic for outside and inside via in the cavity section. Next, in step 104, bake the vias. In step 106, etch the vias. In step 108, Pattern cavity at 100% intensity and pattern CPW area at 50%, bake, no etch at this time. In step 110, pattern the backside metal for the ground plane. In step 112, plate though glass and polish topside to remove overburden. In step 114, pattern topside metal and plate thick conductive metal (e.g., copper) with slots. And in step 116, etching out the cavity to form the slotted antenna in a single wafer.

[0058] It is contemplated that any embodiment discussed in this specification can be implemented with respect to any method, kit, reagent, or composition of the invention, and vice versa. Furthermore, compositions of the invention can be used to achieve methods of the invention.

[0059] It will be understood that particular embodiments described herein are shown by way of illustration and not as limitations of the invention. The principal features of this invention can be employed in various embodiments without departing from the scope of the invention. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, numerous equivalents to the specific procedures described herein. Such equivalents are considered to be within the scope of this invention and are covered by the claims.

[0060] All publications and patent applications mentioned in the specification are indicative of the level of skill of those skilled in the art to which this invention pertains. All publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.

[0061] The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean“one,” but it is also consistent with the meaning of“one or more,”“at least one,” and“one or more than one.” The use of the term“or” in the claims is used to mean“and/or” unless explicitly indicated to refer to alternatives only or the alternatives are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and“and/or.” Throughout this application, the term“about” is used to indicate that a value includes the inherent variation of error for the device, the method being employed to determine the value, or the variation that exists among the study subjects.

[0062] As used in this specification and claim(s), the words“comprising” (and any form of comprising, such as“comprise” and“comprises”),“having” (and any form of having, such as“have” and“has”), “including” (and any form of including, such as“includes” and “include”) or“containing” (and any form of containing, such as“contains” and“contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps. In embodiments of any of the compositions and methods provided herein, “comprising” may be replaced with“consisting essentially of’ or“consisting of’. As used herein, the phrase“consisting essentially of’ requires the specified integer(s) or steps as well as those that do not materially affect the character or function of the claimed invention. As used herein, the term“consisting” is used to indicate the presence of the recited integer (e.g., a feature, an element, a characteristic, a property, a method/process step or a limitation) or group of integers (e.g., feature(s), element(s), characteristic(s), property(ies), method/process steps or limitation(s)) only.

[0063] The term“or combinations thereof’ as used herein refers to all permutations and combinations of the listed items preceding the term. For example,“A, B, C, or combinations thereof’ is intended to include at least one of: A, B, C, AB, AC, BC, or ABC, and if order is important in a particular context, also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB. Continuing with this example, expressly included are combinations that contain repeats of one or more item or term, such as BB, AAA, AB, BBC, AAABCCCC, CBBAAA, CABABB, and so forth. The skilled artisan will understand that typically there is no limit on the number of items or terms in any combination, unless otherwise apparent from the context.

[0064] As used herein, words of approximation such as, without limitation, “about”, "substantial" or "substantially" refers to a condition that when so modified is understood to not necessarily be absolute or perfect but would be considered close enough to those of ordinary skill in the art to warrant designating the condition as being present. The extent to which the description may vary will depend on how great a change can be instituted and still have one of ordinary skill in the art recognize the modified feature as still having the required characteristics and capabilities of the unmodified feature. In general, but subject to the preceding discussion, a numerical value herein that is modified by a word of approximation such as“about” may vary from the stated value by at least ±1, 2, 3, 4, 5, 6, 7, 10, 12 or 15%.

[0065] All of the compositions and/or methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the compositions and methods of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the compositions and/or methods and in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit and scope of the invention. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined by the appended claims.

[0066] To aid the Patent Office, and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims to invoke paragraph 6 of 35 U.S.C. § 112, U.S.C. § 112 paragraph (f), or equivalent, as it exists on the date of filing hereof unless the words“means for” or “step for” are explicitly used in the particular claim.

[0067] For each of the claims, each dependent claim can depend both from the independent claim and from each of the prior dependent claims for each and every claim so long as the prior claim provides a proper antecedent basis for a claim term or element.