Inventors:

Ramanujapuram A. Srinivas

Michael Greenberg

David Gaudiosi

Michael Mielke

Tim Booth

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This non-provisional patent application claims the priority benefit of US provisional patent application number 61/383,691, filed on September 16, 2010 and titled "Semiconductor Processing using Lasers" - which is hereby incorporated by reference in its entirety.

BACKGROUND

[0002] Field of the Invention

[0003] The present technology relates generally to laser processing. More

specifically, the present technology relates to systems and method for ablating materials utilizing a laser.

1 PA5392US SUMMARY

[0004] According to some embodiments, the present technology may be directed to methods for selectively ablating one or more layers of a layered material. The methods may comprise: (a) selectively adjusting ultrafast laser output of an ultrafast laser device based upon one or more physical attributes of a layer of the layered material; (b) applying the ultrafast laser output of the ultrafast laser device to the layer of the layered material along a tool path to ablate the layer along the tool path; (c) re-executing steps (a) and (b) to ablate one or more additional layers, the re-execution of steps (a) and (b) occurring for each distinct layer of the layered material that is to be ablated; and (d) wherein the selective ablation of the layered material prepares the layered material for subsequent processing.

[0005] According to other embodiments, the present technology may be directed to systems for selectively ablating one or more layers of a layered material. The systems may include (a) an ultrafast laser device comprising: (i) a laser generating assembly for generating selectively adjustable ultrafast laser output; (ii) a beam delivery assembly for delivering the selectively adjustable ultrafast laser output to the one or more layers of the layered material; (iii) wherein the ultrafast laser device is communicatively coupled with a processor, the processor executing instructions selectively adjusting the ultrafast laser output, the instructions comprising: (1) a control module that: (A) selectively adjusts the ultrafast laser output of the ultrafast laser device by selectively adjusting at least one of the laser generating assembly and the beam delivery assembly, based upon one or more physical attributes of a layer of the layered material received from an analysis module; (B) applies the ultrafast laser output of the ultrafast laser device to the layer of the layered material along a tool path to ablate the layer along the tool path; and (C) wherein the selective ablation of the layered material prepares the layered material for subsequent processing.

2 PA5392US [0006] According to additional embodiments, the present technology may be directed to methods for preparing a layered material for subsequent processing, the layered material including a getter layer disposed on an outer surface of the layer material. Methods may include (a) selectively adjusting ultrafast laser output of an ultrafast laser device based upon the physical attributes of the getter layer; and (b) applying the ultrafast laser output of the ultrafast laser device to the getter layer according to a pattern to ablate the getter layer and expose a device layer positioned below the getter layer.

[0007] According to some embodiments, the present technology may be directed to methods for processing a semiconductor wafer, the wafer having a base layer, one or more device layers, and a getter layer. These methods may include (a) applying ultrafast laser output of an ultrafast laser to remove at least a portion of the getter layer from the semiconductor wafer; and (b) selectively applying ultrafast laser output of the ultrafast laser to at least one of the one or more device layers to ablate at least a portion of the at least one device layer to create a device structure therein.

3 PA5392US BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Certain embodiments of the present technology are illustrated by the accompanying figures. It will be understood that the figures are not necessarily to scale and that details not necessary for an understanding of the technology or that render other details difficult to perceive may be omitted. It will be understood that the technology is not necessarily limited to the particular embodiments illustrated herein.

[0009] FIG. 1 A is a block diagram of an exemplary ultrafast laser for use in accordance with the present technology.

[0010] FIG. IB is a cross sectional representation of a processed layered material.

[0011] FIG. 2 is a block diagram of an exemplary control system for an exemplary ultrafast laser device.

[0012] FIG. 3 is a flowchart of an exemplary method for selectively ablating one or more layers of a layered material.

[0013] FIG. 4 illustrates an exemplary computing system that may be used to implement embodiments according to the present technology.

4 PA5392US DETAILED DESCRIPTION

[0014] While this technology is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail several specific embodiments with the understanding that the present disclosure is to be considered as an exemplification of the principles of the technology and is not intended to limit the technology to the embodiments illustrated.

[0015] It will be understood that like or analogous elements and/or components, referred to herein, may be identified throughout the drawings with like reference characters. It will be further understood that several of the figures are merely schematic representations of the present technology. As such, some of the components may have been distorted from their actual scale for pictorial clarity.

[0016] The present technology relates generally to laser processing of layered materials, and more specifically, but not by way of limitation, to systems and methods that utilize selectively adjustable ultrafast laser output for ablating individual layers of the layered materials, based upon the physical attributes of each layer. The present technology may also selectively ablate portions of layers in preparation for subsequent processing steps that may include any of laser, chemical, or mechanical processes.

[0017] Generally speaking, the present technology may perform substrate plasma dicing, wafer scribing, Shockwave induced cleaving, and generate coating features to enhance light source ability during processing. Also, the present technology is broadly directed to systems and methods that process (e.g., singulate, etch, mill, ablate, and so forth) layered materials by selectively ablating individual layers with ultrafast laser output that may be tailored to ablate individual layers based upon their physical attributes (e.g., physical properties such as density, opacity, crystalline structure, molecular components, and so forth).

5 PA5392US [0018] Additionally, the present technology may also utilize one or more ultrafast laser devices that generate ultrafast laser output that may be selectively adjusted based upon the physical attributes of the layer currently being processed.

[0019] Embodiments according to the present technology may include an ultrafast laser performing ablation on a target component, such as a layered material. FIG. 1A is a block diagram of an exemplary ultrafast laser for use in accordance with the present technology. FIG. 1A includes a laser device 110, a target component 130, and a platform 140. Laser device 110 may direct ultrafast laser light 120 at target component 130 (e.g., layered material) which rests on platform 140. In some embodiments, parameters of the laser may be adjusted as the laser light is directed at target component 130. It will be understood that laser parameters may include, but are not limited to, pattern, pulse width, pulse energy level, focal point, frequency, laser repetition rate, fill spacing, number of passes, and combinations thereof.

[0020] According to some embodiments, the target component 130 may include a layered material (FIG. IB) that comprises, for example, a base layer 145, one or more device layers (shown herein with a first device layer 150A and a second device layer 150B), and one or more getter layers 155 disposed on the uppermost device layer. The base layer 145 may include any organic and/or inorganic material. Common non- limiting examples of base layers include silicon wafers, metals, alloys, hard biological tissues, and so forth. Device layers may include, but are not limited to, glass, ceramics, semiconducting materials, plastics (e.g., polymers, bioplastics, resins, and so forth). Getter layers may be comprised of polymers, metals, and so forth. The term "getter" may also include sacrificial and resist. One of ordinary skill in the art will appreciate that the above description of the target component 130 is intended to be non-limiting and non exhaustive. That is, the exact numbers, types, and positioning of the various layers may vary greatly depending upon the product.

6 PA5392US [0021] Generally speaking, the laser device 110 may include any laser emitting device that is configured to deliver energy in ultrashort pulses to ablate material. It is noteworthy to mention that the strength of the electric field generated by the beam of the ultrafast laser may increase significantly (above the ablation point of the material) such that the target molecules of the material begin to be ionized and create plasma, in a process known as optical breakdown. Ultimately, these molecules are removed from the material surface, or "ablated," without collateral damage to the remaining material. In contrast to the femtosecond and picosecond ultrafast lasers provided herein, long pulse devices utilize energy waves for ablating material that cause a mix of optical breakdown and traditional thermal processes. Unfortunately, these long pulse systems may cause significant heat transfers to the material and may thermally damage collateral areas surrounding the focal point of the beam.

[0022] It will be understood that ultrafast lasers produce pulses of light that may be less than a picosecond long in duration. The shortness of the pulses ensures that the ablation process is substantially caused by optical breakdown, while minimizing or eliminating thermal breakdown or degradation. Therefore, precise features may be machined into a variety of materials without introducing heat or thermal irregularities to the materials.

[0023] In some applications, the laser device 110 may utilize shock wave inducing ultrafast laser output to cause effects such as cleaving, ablating, dividing, separating, milling, cracking, weakening, splitting and so forth, within any layer of a layered material. The ultrafast laser output may create features such as device structures within a layer. Common examples of device structures may include, but are not limited to, apertures, grooves, channels, or voids having any desired three-dimensional

geometrical configuration, size, or volume.

[0024] The laser device 110 may include both a laser emitting assembly 160 and a beam delivery assembly 165. The laser emitting assembly 160 may include any type of

7 PA5392US ultrafast laser generating device that can generate laser light output having pulse widths selected from any of femtosecond, sub-picosecond, and low range picosecond ranges.

[0025] As discussed in greater detail herein, the ultrafast laser light output generated by the laser emitting assembly 160 may be selectively varied by selectively varying any of pulse width, pulse energy level, frequency, laser repetition rate, or combinations thereof. Additionally, the selectively varying of the operational parameters of the beam delivery assembly 165 may affect parameters such as beam width, fill spacing, scan speed, focal point, and so forth. The beam delivery assembly 165 may be generally described as comprising optical and/or structural components that are utilized to focus and/or direct the ultrafast laser output generated by the laser emitting assembly 160. The construction and operation of beam delivery assemblies would be well known to one of ordinary skill in the art with the present disclosure before them. Therefore, a detailed discussion of the beam delivery assembly 165 will be omitted for the purpose of brevity.

[0026] As mention herein, these ultrafast laser light outputs generated by the laser device 110 may induce shock waves in layers of a layered material with minimal-to-no heating. The present technology may use these shock waves in a controlled fashion to introduce defects or cracks that can be propagated along a desired direction through subsequent processing (e.g., laser guided, thermal gradients, and/or mechanical stress). The present technology harnesses the high incident energy and athermal nature of ultrafast laser output to provide mechanisms for creating features such as device structures within the bulk of crystalline, poly /multi-crystalline and sintered substrates (e.g., layered materials).

[0027] These layered materials may be comprised of individual layers of different materials such as silicone (Si), Gallium Arsenide (GaAs), Sapphire, Silicon Carbide (SiC), glass formulations, ceramics, and so forth. By way of non-limiting example, the o PA5392US present technology may process a silicon, glass, or sapphire substrate, by creating a shallow trench (also known as a pilot trench) that may be further processed to create device structures and/or define a zone of cleaving (e.g., an outline or section of the substrate that is to be removed via ultrafast laser output) prior to final ablation or separation of the substrate to create the device structure.

[0028] In embodiments according to the present technology, the pilot trench may be created either using the same laser or by another process/system that may include chemical, laser, or mechanical processes. The high energy ultra-short pulses can then be applied along a path to create a pattern of device structures within the layer. In some embodiments, trenching may generate defects or cracks in the defined zone that can be propagated through via subsequent processing. Subsequent processing may include, but is not limited to, dry etching, wet etching, plasma etching and combinations thereof.

[0029] It is noteworthy that material may or may not be removed from the substrate during the creation of these defects or cracks. The defects may be designed to induce cracks that are substantially perpendicular or orthogonal to the direction of the trench (e.g., a tool path that is defined by the movement of the laser device 110 relative to the target component 130). In other embodiments, such as with the cutting of sapphire wafers (e.g., electrical devices), the present technology may be utilized to process the substrate without a predefined trench.

[0030] Additionally, the present technology may utilize several crack propagation techniques for creating device structures within individual layers of layered material. With regard to lasers, laser output typically uses complex architectures to create and propagate cracks. In glass cutting, a water jet nozzle may produce a concentrated jet of water that trails a carbon dioxide (C02) laser beam to actively cool the heated substrate and maintain its temperature within the glass transition regime and induce local softening and crack propagation. In some cases, the cracks are initiated mechanically. For example, when cutting silicon wafers, nanosecond or picosecond lasers may

Q PA5392US generate localized heated zones that create defects that may be propagated during subsequent processing. These zones can be subsurface or on the surface of the substrate (or other layer).

[0031] It will be understood that traditional approaches may utilize lasers to ablate through the stacked materials and the substrate utilizing a single beam of laser output. The laser output may have a single wavelength and a constant operating profile (e.g pulse duration, pulse width, fill spacing, and so forth). These traditional approaches often create processed products with defects such as cracking (both internal and external surface irregularities).

[0032] Advantageously, the present technology may leverage the inherent athermal interaction of the ultrafast laser output of the laser device 110 with layers of layered material by combining these athermal interactions with other subsequent processes or manufacturing techniques to create high through-put manufacturing processes that enable the proliferation the present technology (such as laser device 110) into high volume manufacturing environments.

[0033] The present technology limits the thermal exposure and extent of machining of layered materials to enhance processing yields and reduce overall manufacturing costs. Again, the present technology may be used for cutting, cleaving, slotting, or otherwise processing materials such as crystalline, poly/multi- crystalline, sintered materials, and so forth.

[0034] The present technology may be used for creating device structures in layered materials, even those requiring device structures having tight tolerances. Suitable products created by the present technology may be utilized to create semiconductors, light emitting diode (LED) and other display substrates, disk drive heads, and so forth. In some exemplary use cases, the present technology may be used to process materials that absorb wavelengths of approximately 1552 nanometers or various harmonics thereof, to create features within the materials at the correct precision (physical

1 n PA5392US tolerances), fidelity and productivity, or combinations thereof. It will be understood that the present technology may not be limited to only the use of ultrafast laser output of approximately 1552 nanometers, but may be tailored to the physical attributes of the layers of the layered material.

[0035] FIG. 2 illustrates a block diagram of an exemplary control system 200 for operating an exemplary ultrafast laser device, such as laser device 110 described with reference to FIG. 1A. Generally speaking, the control system 200 may include a computing system 205 that includes a laser controller application (hereinafter application 210) that, when executed by a processor, controls the operation of the laser device 110. General operations of the computing system 205 may be described in greater detail with reference to the computing system 400 of FIG. 4. The application 200 may cause the computing system 205 to function as a particular purpose computing system that allows the laser device 110 to process the layers of a layered material (such as target component 130).

[0036] The computing system 205 may include a standalone computing system that communicatively couples with the laser device 110, or may be integrated into the computational components of the laser device 110.

[0037] In some embodiments, the computing system 205 may be communicatively coupled with one or more sensing devices 215 that measure the physical attributes of the layers of the layered material. Because of the virtually unlimited variety of sensors or measurement devices which may be utilized in accordance with the present technology, a discussion of these devices has been omitted for the purposes of brevity. One of ordinary skill in the art would readily appreciate the use of such suitable sensors that may measure any one of a number of physical attributes of the layers of the layered material. In general, these physical attributes may include physical attributes that affect the manner with which ultrafast laser output interacts with the layers of the layered material, for example, density and opacity. In some embodiments, rather than sensing

1 1 PA5392US the physical attributes of the layers, the physical attributes may be known quantities that may be input into the application 200.

[0038] The application 200 may be generally described as including a control module 220 and an analysis module 225. 1 1 is noteworthy that the application 200 may include additional modules, engines, or components, and still fall within the scope of the present technology. As used herein, the term "module" may also refer to any of an application-specific integrated circuit ("ASIC"), an electronic circuit, a processor (shared, dedicated, or group) that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.

[0039] The control module 220 may selectively adjust the operation of both the laser emitting assembly 160 and the beam delivery assembly 165 to vary the operating parameters of the laser device 110 (see FIG. 1 A). Advantageously, the selective adjustment of these operating parameters allows for the ultrafast laser output of the laser device 110 to be fine tuned for each layer of the target component 130.

[0040] The fine tuning may be based upon the determination of the physical attributes of a particular layer as determined by the analysis module 225. In order for the control module 220 to fine tune (e.g., selectively vary) the ultrafast laser output, the analysis module 225 may receive layer information from the one or more sensing devices 215 that determine or approximate the physical attributes of a layer (or a plurality of layers in a multilayered device). Again, these physical attributes may not need to be measured, but may be known quantities that are input into the application 200 via a user interface (not shown).

[0041] Returning to FIG. IB, a layered material (target component 130) may include a getter layer 155 disposed on top of a first and second device layers, 150A and 150B, respectively. The material may also include a base layer (substrate) 145. In this example, the first device layer 150A is comprised of a first material, and the second

1 PA5392US device layer 150B is comprised of a second material. For the purposes of explicating the fine tuning of the laser device 110, the getter layer 155 is understood to have different physical attributes relative to the first and second device layers 150A and 150B. To process this layered material, it will be assumed that the physical attributes of each layer have been input into the system, or determined via the one or more sensing devices.

[0042] The control module 220 selectively varies the operating parameters of the laser device 110 (by selectively varying the configuration of at least one of the laser emitting assembly 160 and the beam delivery assembly 165) to ablate the getter layer 155. Next, the control module 220 causes the laser device 110 to apply ultrafast laser output to the getter layer to ablate the getter layer along a particular pattern (e.g., tool path). In some embodiments, the entire getter layer 155 may be ablated or removed. The ablated portion of the getter layer 155 is shown as void 170.

[0043] Ablation of the getter layer exposes a portion of first device layer 150A that is under void 170. Again, based upon the physical attributes of the first device layer 150A, the control module 220 selectively varies the operating parameters of the laser device 110 to ablate at least a portion of the first device layer to create features therein, such as void 175. These features may include through vias, device structures (e.g., grooves, channels, voids, spaces, and so forth), and the like. It will be understood that these features may have any one of a number of regular or irregular three dimensional geometrical or polygonal configurations.

[0044] Next, the based upon the physical attributes of the second device layer 150B, the control module 220 selectively varies the operating parameters of the laser device 110 to ablate at least a portion of the second device layer 150B to create features therein, such as void 180. It will be understood that the features formed in the second layer 150B may be created by focusing the ultrafast laser output of the laser device 110 to a particular depth within the second device layer 150B. That is, it may not be necessary

1 Q PA5392US to expose the second layer 150B by ablating the first layer 150A, before features may be created in the second device layer 150B. In this way, device structures of different layers may overlap one another. Additionally, the laser device 110 may create apertures (such as aperture 185) that extend between device structures of different device layers. These apertures may receive conductive material that electrically couples electrical devices disposed in different device layers.

[0045] FIG. 3 is a flowchart of an exemplary method 300 for selectively ablating one or more layers of a layered material. It will be understood that in some embodiments, the layered material may include a layered device such as a semiconductor wafer. As such, the method may be utilized to create features within the wafer such as device structures that are created to receive electrical devices therein. Electrical devices may include objects such as sensors, processors, storage media, segments of electrically conducting materials for interconnecting electrical devices, and the like.

[0046] Also, the method 300 may be utilized to prepare the wafer for subsequent processing steps such as dry /wet etching, deposition, implantation, ion bombardment, texturing, and/or polishing - just to name a few.

[0047] The method may begin with an optional step 305 of determining the physical attributes of a layer that is to be ablated. This step 305 may be executed by receiving the output of one or more sensing devices that measure the physical attributes of the layer.

[0048] Upon receiving the physical attributes of the layer, the method moves to step 310 that includes selectively adjusting ultrafast laser output of an ultrafast laser device based upon the physical attributes of the layer. This step 310 may be executed by a control module that selectively varies the operating parameters of the laser device, as described in greater detail above.

[0049] Next, the method 300 may include the step 315 of applying the ultrafast laser output of the ultrafast laser device to the layer along a tool path to ablate the layer along the tool path.

1 PA5392US [0050] After ablation of the layer, the method 300 may include return to step 305 of determining the physical attributes of an additional layer before executing steps 310 and 315 to ablate the additional layer and create features therein. The method 300 may return to step 305 for each layer that is to be ablated.

[0051] As mention above, if the physical properties of each of the layers are known, step 305 may be omitted. Therefore, the method 300 may comprise recurrently or successively executing steps 310 and 315 to process the wafer.

[0052] It will be understood that method 300 may be utilized to prepare the layered material for subsequent processing, which may include singulation or dicing of the wafer from a larger wafer. These subsequent processes may utilize processes such as wet/dry etching, plasma etching, laser modification in combination with laser fracturing, mechanical cleaving, and so forth.

[0053] FIG. 4 illustrates an exemplary computing system 400 that may be used to implement an embodiment of the present technology. The computing system 400 of FIG. 4 may be implemented in the contexts of the likes of computing systems, networks, servers, or combinations thereof. The computing system 400 of FIG. 4 includes one or more processors 410 and main memory 420. Main memory 420 stores, in part, instructions and data for execution by processor 410. Main memory 420 may store the executable code when in operation. The system 400 of FIG. 4 further includes a mass storage device 430, portable storage medium drive(s) 440, output devices 450, user input devices 460, a graphics display 470, and peripheral devices 480.

[0054] The components shown in FIG. 4 are depicted as being connected via a single bus 490. The components may be connected through one or more data transport means. Processor unit 410 and main memory 420 may be connected via a local microprocessor bus, and the mass storage device 430, peripheral device(s) 480, portable storage device 440, and display system 470 may be connected via one or more input/output (I/O) buses.

15 PA5392US [0055] Mass storage device 430, which may be implemented with a magnetic disk drive or an optical disk drive, is a non-volatile storage device for storing data and instructions for use by processor unit 410. Mass storage device 430 may store the system software for implementing embodiments of the present technology for purposes of loading that software into main memory 420.

[0056] Portable storage device 440 operates in conjunction with a portable nonvolatile storage medium, such as a floppy disk, compact disk, digital video disc, or USB storage device, to input and output data and code to and from the computing system 400 of FIG. 4. The system software for implementing embodiments of the present technology may be stored on such a portable medium and input to the computing system 400 via the portable storage device 440.

[0057] Input devices 460 provide a portion of a user interface. Input devices 460 may include an alphanumeric keypad, such as a keyboard, for inputting alpha-numeric and other information, or a pointing device, such as a mouse, a trackball, stylus, or cursor direction keys. Additionally, the system 400 as shown in FIG. 4 includes output devices 450. Suitable output devices include speakers, printers, network interfaces, and monitors.

[0058] Display system 470 may include a liquid crystal display (LCD) or other suitable display device. Display system 470 receives textual and graphical information, and processes the information for output to the display device.

[0059] Peripherals 480 may include any type of computer support device to add additional functionality to the computing system. Peripheral device(s) 480 may include a modem or a router.

[0060] The components provided in the computing system 400 of FIG. 4 are those typically found in computing systems that may be suitable for use with embodiments of the present technology and are intended to represent a broad category of such computer components that are well known in the art. Thus, the computing system 400

1 f. PA5392US of FIG. 4 may be a personal computer, hand held computing system, telephone, mobile computing system, workstation, server, minicomputer, mainframe computer, or any other computing system. The computer may also include different bus configurations, networked platforms, multi-processor platforms, etc. Various operating systems may be used including Unix, Linux, Windows, Macintosh OS, Palm OS, Android, iPhone OS and other suitable operating systems.

[0061] It is noteworthy that any hardware platform suitable for performing the processing described herein is suitable for use with the technology. Computer-readable storage media refer to any medium or media that participate in providing instructions to a central processing unit (CPU), a processor, a microcontroller, or the like. Such media may take forms including, but not limited to, non-volatile and volatile media such as optical or magnetic disks and dynamic memory, respectively. Common forms of computer-readable storage media include a floppy disk, a flexible disk, a hard disk, magnetic tape, any other magnetic storage medium, a CD-ROM disk, digital video disk (DVD), any other optical storage medium, RAM, PROM, EPROM, a FLASHEPROM, any other memory chip or cartridge.

[0062] While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. The descriptions are not intended to limit the scope of the technology to the particular forms set forth herein. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments. It should be understood that the above description is illustrative and not restrictive. To the contrary, the present descriptions are intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the technology as defined by the appended claims and otherwise appreciated by one of ordinary skill in the art. The scope of the technology should, therefore, be determined not with reference to the

17 PA5392US above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.

18 PA5392US