A scribing protective layer structure of a gallium oxide single crystal substrate polishing wafer and a scribing method thereof

Abstract

The application provides a scribing protective layer structure of a gallium oxide single crystal substrate polishing wafer and a scribing method thereof, and belongs to the technical field of gallium oxide single crystal substrate polishing wafer processing. The scribing protective layer structure comprises, from bottom to top, a slope clamp, a carrier, a second soft protective layer, a gallium oxide wafer, a first soft protective layer and a hard protective layer which are arranged in layers, and the slope clamp ensures that a cutting path along a (010) crystal surface direction of the gallium oxide wafer is cut at a slope angle. In the application, the first soft protective layer and the second soft protective layer prevent the surface of the polished wafer from being scratched by a hard object and polluted by a cooling medium, and the hard protective layer offsets a part of the normal force of a grinding wheel on the (100) cleavage crystal surface during scribing; the slope clamp further decomposes the normal force of the grinding wheel on the (100) crystal surface, thereby reducing the generation of defects such as cleavage, chipping and micro-cracks of the wafer around the cutting path. The scribing method of the application has a high cutting speed, can realize direct scribing of the polished wafer, and does not generate defects such as scratches and pollution on the surface of the wafer.

Description

Technical Field

[0001] This invention relates to the field of gallium oxide single crystal substrate polishing technology, and in particular to a dicing protective layer structure and dicing method for gallium oxide single crystal substrate polishing. Background Technology

[0002] Gallium oxide (β-G) a2 Gallium oxide (GaO) is a new generation of ultra-wide bandgap semiconductor material, following silicon carbide (SiC) and gallium nitride (GaN), capable of manufacturing high-power, high-frequency, high-efficiency microelectronic devices and deep-ultraviolet optoelectronic devices. With a bandgap of 4.7 eV, compared to third-generation semiconductor materials represented by SiC and GaN, it boasts advantages such as a wider bandgap, higher breakdown strength, a larger Baliga quality factor, a shorter absorption cutoff edge, and lower growth cost. In recent years, with continuous breakthroughs in fundamental research on GaO single-crystal growth processes and downstream related devices, its industrialization process is accelerating.

[0003] Dicing is a crucial step in chip packaging, involving cutting a patterned wafer along dicing lines into individual chips. Gallium oxide (GaO), as a chip substrate material, also requires dicing to cut wafers into different sizes due to limitations in current GaO growth technology and the need for epitaxial growth of small wafers. Currently, abrasive wheel dicing is the most widely used dicing method. It uses a blade composed of binder and diamond particles, rotated at high speed in conjunction with a spindle, and grinding against the workpiece to cut the wafer into individual wafers of the required size at a specific feed rate.

[0004] The (100) crystal plane of gallium oxide is its easy cleavage plane. During the grinding or cutting of the wafer, the (100) crystal plane is prone to cleavage defects. When the (100) crystal plane is cut with a grinding wheel, the high-speed rotating grinding wheel will generate a certain contact force in the direction perpendicular to the (100) crystal plane, which will force the crystal to undergo a certain plastic deformation near the crystal plane, resulting in defects such as cleavage, chipping, and microcracks at the cutting position. These defects are more serious around the cutting path along the (010) crystal plane, which will directly affect the quality and performance of the product. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a dicing protective layer structure and a dicing method for polished gallium oxide single crystal substrate wafers. The dicing protective layer structure of this invention can prevent the wafer surface from being scratched by hard objects and contaminated by cooling media, while reducing the generation of defects such as wafer cleavage, chipping, and microcracks around the dicing track.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a dicing protective layer structure for a gallium oxide single crystal substrate polishing wafer, comprising, from bottom to top, a sloping fixture, a stage, a second soft protective layer, a gallium oxide wafer, a first soft protective layer, and a hard protective layer stacked together. The sloping fixture ensures that the dicing path along the crystal plane direction of the gallium oxide wafer (010) is cut at a sloping angle. The stage, the second soft protective layer, the gallium oxide wafer, the first soft protective layer, and the hard protective layer are parallel to the upper surface of the sloping fixture.

[0008] Preferably, the angle between the upper surface of the ramp clamp and the horizontal plane is 30° to 60°.

[0009] Preferably, the hard protective layer and the platform are made of ceramic or glass independently.

[0010] Preferably, the thickness of the hard protective layer is 1 to 1.5 mm.

[0011] Preferably, the thickness of the stage is 2 to 5 mm.

[0012] Preferably, the first and second soft protective layers are made of polytetrafluoroethylene or polyethylene terephthalate independently.

[0013] Preferably, the thickness of the first soft protective layer and the second soft protective layer is independently 10 to 30 μm.

[0014] This invention also provides a dicing method for a gallium oxide single-crystal substrate polished wafer, utilizing the dicing protective layer structure described above, comprising the following steps:

[0015] The gallium oxide wafer, after being cleaned and pretreated, serves as the dicing protective layer structure. The dicing protective layer structure is then placed on a UV film for cutting, and the lower surface of the ramp fixture is bonded to the UV film.

[0016] Preferably, the cutting is abrasive wheel cutting, the abrasive wheel cutting speed is 0.5-1 mm / s, the abrasive wheel rotation speed is 20000-25000 rpm, the Z-axis feed rate is 300-500 μm per pass, and the cooling water discharge rate is 1-3 L / min.

[0017] Preferably, the grinding wheel used for the grinding wheel cutting is a resin-bonded diamond grinding wheel, and the mesh size of the grinding wheel is 200 to 400.

[0018] This invention provides a dicing protective layer structure for a gallium oxide single crystal substrate polishing wafer, comprising, from bottom to top, a sloping fixture, a stage, a second soft protective layer, a gallium oxide wafer, a first soft protective layer, and a hard protective layer stacked together. The sloping fixture ensures that the dicing path along the crystal plane direction of the gallium oxide wafer (010) is cut at a sloping angle. The stage, the second soft protective layer, the gallium oxide wafer, the first soft protective layer, and the hard protective layer are parallel to the upper surface of the sloping fixture.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] This invention provides two innovative methods to address the easy cleavage of the (100) crystal orientation of gallium oxide single crystal substrates: First, a first soft protective layer and a second soft protective layer are respectively set on the upper and lower surfaces of the gallium oxide wafer. The function of the first and second soft protective layers is to prevent the surface of the polished wafer from being scratched by hard objects and contaminated by the cooling medium. The function of the hard protective layer is to offset part of the normal force exerted by the grinding wheel on the (100) easy-to-cleave crystal surface during the dicing process. Second, a ramp fixture with a certain tilt angle is placed between the stage and the UV film, and the cutting path along the (010) crystal surface is cut at a ramp angle. This will further decompose the normal force exerted by the grinding wheel on the (100) crystal surface, thereby reducing the generation of defects such as wafer cleavage, chipping and microcracks around the cutting path, and solving the problem of easy cleavage near the cutting path and easy contamination and scratching of the wafer surface during gallium oxide wafer dicing.

[0021] This invention also provides a dicing method for polished gallium oxide single crystal substrates. The method uses a grinding wheel to dic the polished gallium oxide single crystal substrate, with a cutting speed of up to 1 mm / s, which greatly improves production efficiency. The first and second soft protective layers on the surface of the gallium oxide wafer allow for direct dicing of the polished wafer without further surface processing, and do not produce defects such as scratches and contamination on the wafer surface. Normal cleaning after dicing is sufficient to achieve product-grade quality. The use of a hard protective layer and a ramp fixture can effectively avoid defects such as cleavage, chipping, and microcracks around the dicing path along the (010) crystal plane, solving the problem of difficult dicing of polished gallium oxide single crystal (100) crystal plane wafers. Attached Figure Description

[0022] Figure 1 A schematic diagram of the dicing protective layer structure for a gallium oxide single-crystal substrate polishing wafer;

[0023] Figure 2 A schematic diagram of the dicing path along the (010) crystal plane after dicing a (100) wafer;

[0024] Figure 3A physical image (50x optical microscope) of the dicing path along the (010) crystal plane after dicing of a (100) wafer without the application of the technical solution of the present invention;

[0025] Figure 4 A physical image (200x optical microscope) of the dicing path along the (010) crystal plane after dicing of a (100) wafer without the application of the technical solution of the present invention;

[0026] Figure 5 A physical image (50x optical microscope) of the dicing path along the (010) crystal plane after the (100) wafer of the present invention has been diced to apply the technical solution of the present invention;

[0027] Figure 6 A physical image (200x optical microscope) of the dicing path along the (010) crystal plane after the (100) wafer of the present invention has been diced to apply the technical solution of the present invention;

[0028] In the figure: 1 is the hard protective layer, 2 is the gallium oxide wafer, 3-1 is the second soft protective layer, 3-2 is the first soft protective layer, 4 is the stage, 5 is the ramp clamp, 6 is the UV film, 7 is the ceramic chuck, 8 is the (010) crystal plane, and 9 is the (100) crystal plane. Detailed Implementation

[0029] This invention provides a dicing protective layer structure for a gallium oxide single crystal substrate polishing wafer, comprising, from bottom to top, a sloping fixture, a stage, a second soft protective layer, a gallium oxide wafer, a first soft protective layer, and a hard protective layer stacked together. The sloping fixture ensures that the dicing path along the crystal plane direction of the gallium oxide wafer (010) is cut at a sloping angle. The stage, the second soft protective layer, the gallium oxide wafer, the first soft protective layer, and the hard protective layer are parallel to the upper surface of the sloping fixture.

[0030] Figure 1 This is a schematic diagram of the protective layer structure for a dicing process on a gallium oxide single-crystal substrate polishing wafer. In the diagram: 1 is the hard protective layer, 2 is the gallium oxide wafer, 3-1 is the second soft protective layer, 3-2 is the first soft protective layer, 4 is the stage, 5 is the ramp fixture, 6 is the UV film, 7 is the ceramic chuck, 8 is the (010) crystal plane, and 9 is the (100) crystal plane. The following is a combination of... Figure 1 The protective layer structure of the present invention will be described.

[0031] The dicing protective layer structure of the present invention includes a ramp clamp 5.

[0032] In this invention, the angle between the upper surface of the ramp clamp and the horizontal plane is preferably 30 to 60°.

[0033] In this invention, the inclined clamp 5 is preferably made of ceramic or resin.

[0034] The dicing protective layer structure of the present invention includes a stage 4.

[0035] In this invention, the stage 4 is preferably made of ceramic or glass, and the hardness of the stage 4 is similar to that of gallium oxide single crystal.

[0036] In this invention, the thickness of the stage 4 is preferably 2 to 5 mm.

[0037] The dicing protective layer structure of the present invention includes a second soft protective layer 3-1.

[0038] In this invention, the material of the second soft protective layer 3-1 is preferably polytetrafluoroethylene (Teflon) or polyethylene terephthalate (PET), and the second soft protective layer 3-1 is a high-temperature resistant material.

[0039] In this invention, the thickness of the second soft protective layer 3-1 is preferably 10 to 30 μm.

[0040] The dicing protective layer structure of the present invention includes a gallium oxide wafer 2.

[0041] In this invention, the gallium oxide wafer 2 is a polished gallium oxide single crystal substrate to be processed.

[0042] The dicing protective layer structure of the present invention includes a first soft protective layer 3-2.

[0043] In this invention, the first soft protective layer 3-2 is preferably made of polytetrafluoroethylene (Teflon) or polyethylene terephthalate (PET), and the first soft protective layer 3-2 is a high-temperature resistant material.

[0044] In this invention, the thickness of the first soft protective layer 3-2 is preferably 10 to 30 μm.

[0045] The dicing protective layer structure of the present invention includes a rigid protective layer 1.

[0046] In this invention, the material of the hard protective layer 1 is preferably ceramic or glass, and the hardness of the hard protective layer 1 is similar to that of a gallium oxide single crystal substrate polished wafer.

[0047] In this invention, the thickness of the hard protective layer 1 is preferably 1 to 1.5 mm.

[0048] In this invention, the stage 4 and the second soft protective layer 3-1, the second soft protective layer 3-1 and the gallium oxide wafer 2, the gallium oxide wafer 2 and the first soft protective layer 3-2, and the first soft protective layer 3-2 and the hard protective layer 4 are preferably bonded by an adhesive. The adhesive is preferably paraffin wax, which melts when heated and solidifies when cooled, thereby playing an adhesive role. The paraffin wax is easy to remove and will not cause cleavage on the wafer surface.

[0049] The present invention does not impose any particular limitation on the specific preparation method of the dicing protective layer structure, and any method known to those skilled in the art can be used. In a specific embodiment of the present invention, it is preferable to attach the protective layer structure on a heating stage. The temperature of the heating stage is preferably set to 80-130°C. After the stage 4 is placed on the heating stage and heated to the preset temperature, the following steps are performed in sequence: applying paraffin wax, attaching the second soft protective layer 3-1, applying paraffin wax again, placing the gallium oxide wafer 2, applying paraffin wax again, attaching the first soft protective layer 3-2, applying paraffin wax again, and attaching the hard protective layer 1. After applying paraffin wax, it is necessary to ensure that the paraffin wax is completely melted; after attaching the second soft protective layer 3-1 and the first soft protective layer 3-2, it is necessary to ensure that the surface is flat and free of air bubbles; after placing the gallium oxide wafer 2 and the hard protective layer 1, it is necessary to ensure that the fit is tight and free of air bubbles. The resulting uncooled assembly is placed on a tablet press and held under a pressure of 0.1-0.2 MPa / 2-inch wafer for 5-10 minutes, and then bonded to the ramp clamp 5 (preferably using AB glue) to obtain the dicing protective layer structure.

[0050] The dicing protective layer structure of the present invention preferably further includes a UV film 6.

[0051] In this invention, the thickness of the UV film is preferably 0.1 to 0.3 mm.

[0052] The dicing protective layer structure of the present invention preferably further includes a ceramic suction cup 7.

[0053] The present invention does not have any special limitation on the ceramic suction cup 7. In a specific embodiment of the present invention, the ceramic suction cup 7 is preferably a ceramic suction cup in a grinding wheel scribing machine.

[0054] This invention also provides a dicing method for polishing gallium oxide single-crystal substrates, utilizing the protective layer structure described above, comprising the following steps:

[0055] The gallium oxide wafer, after being cleaned and pretreated, serves as the dicing protective layer structure. The dicing protective layer structure is then placed on a UV film for cutting, and the lower surface of the ramp fixture is bonded to the UV film.

[0056] In this invention, the thickness of the pretreated gallium oxide single crystal substrate polishing sheet is preferably 300-800 μm.

[0057] In this invention, the cleaning preferably includes washing with detergent, washing with pure water, and washing with alcohol in sequence. The purpose of the cleaning is to ensure that there are no impurity particles and obvious dirt on the surface of the gallium oxide single crystal.

[0058] In this invention, the cleaning is preferably performed under ultrasonic conditions, and the washing time for detergent, pure water and alcohol is preferably 5 minutes.

[0059] In this invention, the dicing protective layer structure is preferably bonded to the UV film and then placed on the ceramic suction cup of the grinding wheel dicing machine.

[0060] In this invention, the cutting is preferably done with a grinding wheel, the cutting speed of which is preferably 0.5 to 1 mm / s, the grinding wheel speed is preferably 20,000 to 25,000 rpm, the Z-axis feed rate is preferably 300 to 500 μm per pass, and the cooling water discharge rate is preferably 1 to 3 L / min. During the cutting process, the dicing protective layer structure ensures that the cutting path along the (010) crystal plane of the gallium oxide wafer is cut at a slope angle.

[0061] In this invention, the grinding wheel used for grinding is a resin-bonded diamond grinding wheel, and the preferred mesh size of the grinding wheel is 200 to 400 mesh.

[0062] After the cutting is completed, the present invention preferably places the resulting cut assembly on a heating stage for wafer unloading. The temperature of the heating stage is preferably 110-130°C. After the paraffin wax is completely melted, the second soft protective layer 3-1 is dragged to unload the wafer, so as to avoid direct contact between the wafer and the stage 4 and cause scratches.

[0063] After the wafers are removed from the wafer, the present invention preferably places the obtained wafers into detergent, pure water, acid and alcohol in sequence for ultrasonic cleaning, and the wafer dicing is completed.

[0064] The present invention does not impose any special limitations on the specific parameters of the ultrasonic cleaning; any method known to those skilled in the art can be used.

[0065] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0066] Example 1

[0067] Step 1: Clean the gallium oxide single crystal substrate polished wafer (thickness 300μm) by sonicating it in detergent, pure water and alcohol for 5 minutes respectively, and observe it under a 50x optical microscope to ensure that there are no impurity particles and obvious dirt on the surface.

[0068] Step 2: Attach the protective layer structure to the heating stage. Set the heating stage temperature to 80℃. Place the stage 4 (made of glass, 5mm thick) on the heating stage and heat it to the preset temperature. Then, attach the protective layer in the following order: apply paraffin wax, attach the second soft protective layer 3-1 (made of PET, 10μm thick), apply paraffin wax, place the gallium oxide wafer 2, apply paraffin wax, attach the first soft protective layer 3-2 (made of PET, 10μm thick), apply paraffin wax, and attach the hard protective layer 1 (made of glass, 1mm thick). After applying paraffin wax, ensure it is completely melted. After attaching the first soft protective layer 3-2 and the second soft protective layer 3-1, ensure it is flat and free of air bubbles. After placing the gallium oxide wafer 2 and the hard protective layer 1, ensure they are tightly bonded and free of air bubbles.

[0069] Step 3: Place the uncooled assembly on a tablet press and press it for 10 minutes at a pressure of 0.1 MPa / 2-inch wafer to compact it.

[0070] Step 4: Bond the compacted assembly to the ramp clamp 5 using AB glue. The ramp clamp 5 is made of ceramic. The angle between the upper surface of the ramp clamp 5 and the horizontal plane is 30°, ensuring that the cutting path along the (010) crystal plane is cut at a ramp angle (e.g., Figure 2 As shown), the normal force applied to the (100) crystal plane by the decomposition grinding wheel is reduced, thereby reducing defects such as wafer cleavage around the cutting path.

[0071] Step 5: After bonding the assembly from step 4 to the UV film (0.1mm thick), place it on the ceramic suction cup 7 of the grinding wheel scribing machine.

[0072] Step 6: Perform abrasive wheel cutting, with a cutting speed of 1mm / s, a wheel speed of 25000rpm, a Z-axis feed rate of 300μm per pass, a cutting coolant flow rate of 3L / min, and a resin-bonded diamond wheel with a grit of 200#.

[0073] Step 7: Place the cut assembly on the heating stage for wafer unloading. Set the heating stage temperature to 130℃. After the paraffin wax has completely melted, drag the second soft protective layer 3-1 at the bottom of the wafer to unload it, avoiding direct contact between the wafer and the stage to prevent scratches.

[0074] Step 8: Place the cut wafers into detergent, pure water, acid, and alcohol respectively for ultrasonic cleaning. The dicing process is now complete.

[0075] Figure 3 The image shows the cutting path along the (010) crystal plane after dicing of a (100) wafer without the application of the technical solution of this invention (using the traditional grinding wheel dicing method, directly attaching the wafer to the UV film for dicing). (50x optical microscope) Figure 4 The image shows the cutting path along the (010) crystal plane after dicing of a (100) wafer without the application of the technical solution of this invention (using the traditional grinding wheel dicing method, directly attaching the wafer to the UV film for dicing). (200x optical microscope) Figure 5 A physical image (50x optical microscope) of the dicing path along the (010) crystal plane after dicing of the (100) wafer to which the technical solution of the present invention is applied. Figure 6 The actual image (200x optical microscope) of the dicing path along the (010) crystal plane after the (100) wafer of the present invention is obtained by applying the technical solution of the present invention. It can be seen that the first soft protective layer 3-2 and the second soft protective layer 3-1 on the surface of the gallium oxide wafer can directly dic the polished wafer without further surface processing, and without generating defects such as scratches and contamination on the wafer surface. Normal cleaning after dicing can achieve product-grade quality. The use of the hard protective layer 1 and the ramp fixture 5 can effectively avoid defects such as cleavage, chipping and microcracks around the dicing path along the (010) crystal plane, and solve the problem of difficult dicing of gallium oxide single crystal (100) crystal plane polished wafers.

[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A dicing protective layer structure for a gallium oxide single-crystal substrate polished wafer, characterized in that, From bottom to top, it includes a sloping fixture, a stage, a second soft protective layer, a gallium oxide wafer, a first soft protective layer, and a hard protective layer stacked together. The sloping fixture ensures that the cutting path along the crystal plane direction of the gallium oxide wafer (010) is cut at a sloping angle. The stage, the second soft protective layer, the gallium oxide wafer, the first soft protective layer, and the hard protective layer are parallel to the upper surface of the sloping fixture. The angle between the upper surface of the ramp clamp and the horizontal plane is 30~60°; The thickness of the hard protective layer is 1~1.5mm; The first and second soft protective layers are independently made of polytetrafluoroethylene or polyethylene terephthalate, and the thickness of the first and second soft protective layers is independently 10~30μm. The gallium oxide wafer is a pre-treated gallium oxide single crystal substrate polished wafer that is cleaned and then used as the dicing protective layer structure. The thickness of the pre-treated gallium oxide single crystal substrate polished wafer is 300~800μm.

2. The dicing protective layer structure according to claim 1, characterized in that, The hard protective layer and the platform are made of either ceramic or glass.

3. The dicing protective layer structure according to claim 1 or 2, characterized in that, The thickness of the stage is 2~5mm.

4. A dicing method for polished gallium oxide single crystal substrates, characterized in that, The method of using the dicing protective layer structure according to any one of claims 1 to 3 includes the following steps: The gallium oxide wafer, after being cleaned and pretreated, serves as the dicing protective layer structure. The dicing protective layer structure is then placed on a UV film for cutting, and the lower surface of the ramp fixture is bonded to the UV film.

5. The dicing method according to claim 4, characterized in that, The cutting is performed by a grinding wheel, with a cutting speed of 0.5~1mm / s, a grinding wheel rotation speed of 20000~25000rpm, a Z-axis feed rate of 300~500μm per pass, and a cooling water discharge rate of 1~3L / min.

6. The dicing method according to claim 5, characterized in that, The grinding wheel used for cutting is a resin-bonded diamond grinding wheel, and the mesh size of the grinding wheel is 200-400 mesh.

Images