Wafer integration method for improving gallium nitride and diamond bonding strength

Abstract

The application discloses a wafer integration method for improving bonding strength of gallium nitride and diamond, and belongs to the field of semiconductors. The method comprises the following steps: providing a gallium nitride epitaxial wafer and a temporary substrate, wherein the gallium nitride epitaxial wafer comprises a substrate layer and a gallium nitride epitaxial layer; stacking the gallium nitride epitaxial wafer, a bonding material layer and the temporary substrate in sequence and performing first bonding to form a first bonded wafer; removing the substrate layer in the first bonded wafer to obtain a first sample; etching the gallium nitride epitaxial layer to form a groove; providing a diamond substrate, etching the diamond substrate to form a protrusion; clamping the protrusion on the surface of the diamond substrate and the groove on the surface of the gallium nitride epitaxial layer, and performing second bonding on the diamond substrate and the gallium nitride epitaxial layer to obtain a second bonded wafer; and removing the temporary substrate and the bonding material layer in the second bonded wafer to obtain a diamond-based gallium nitride wafer, so that the bonding strength between the gallium nitride and the diamond substrate can be improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductors, and particularly relates to a wafer integration method for improving the bonding strength of gallium nitride and diamond. BACKGROUND

[0002] Gallium nitride (GaN) semiconductor material has excellent characteristics such as large band gap, high breakdown field strength, high carrier mobility, and easy formation of heterostructures, and is very suitable for developing high-power electronic devices and high-frequency microwave devices, and has an important position in the fields of national defense technology, aerospace, 5G communication applications, etc.

[0003] Since diamond has high thermal conductivity, when diamond is used to replace the traditional substrate (sapphire, silicon carbide, silicon, etc.) of the gallium nitride epitaxial film, the heat dissipation performance of the gallium nitride device can be improved, and thus the service life and reliability of the gallium nitride device can be improved.

[0004] At present, a common method for preparing a gallium nitride and diamond substrate is to first peel the gallium nitride material from the original substrate, and then bond the gallium nitride material to the surface of the diamond substrate by wafer bonding technology, so that a diamond-based gallium nitride wafer can be obtained. However, when this method is used, the bonding strength between the gallium nitride material and the diamond substrate is poor, which causes the gallium nitride material on the diamond substrate to easily fall off. SUMMARY

[0005] In order to solve the above problems in the prior art, the application provides a wafer integration method for improving the bonding strength of gallium nitride and diamond. The technical problem to be solved by the application is solved by the following technical scheme:

[0006] In a first aspect, the application provides a wafer integration method for improving the bonding strength of gallium nitride and diamond, comprising:

[0007] Step 1: providing a gallium nitride epitaxial wafer and a temporary substrate, the gallium nitride epitaxial wafer comprising a substrate layer and a gallium nitride epitaxial layer;

[0008] Step 2: preparing a bonding material layer, stacking the gallium nitride epitaxial wafer, the bonding material layer and the temporary substrate in sequence and performing first bonding to form a first bonded wafer, the gallium nitride epitaxial layer and the bonding material layer being in contact;

[0009] Step 3: removing the substrate layer in the first bonded wafer to obtain a first sample;

[0010] Step 4: etching the gallium nitride epitaxial layer in the first sample to form a groove on the surface of the gallium nitride epitaxial layer;

[0011] Step 5: providing a diamond substrate, etching the diamond substrate to form a protrusion on the surface of the diamond substrate, the protrusion and the groove being matched.

[0012] Step six: the protrusions of the diamond substrate surface and the grooves of the gallium nitride epitaxial layer surface are clamped, the diamond substrate and the gallium nitride epitaxial layer are bonded for the second time, and a second bonded wafer is obtained;

[0013] Step seven: the temporary substrate and the bonding material layer in the second bonded wafer are removed, and a diamond-based gallium nitride wafer is obtained.

[0014] In an embodiment of the present application, after step one and before step two, the method further comprises:

[0015] cleaning the gallium nitride epitaxial wafer and the temporary substrate;

[0016] In the method, the gallium nitride epitaxial wafer and the temporary substrate are first cleaned with 10% hydrochloric acid for 1 minute, then rinsed with deionized water for 9 minutes, and finally subjected to spin-drying treatment.

[0017] In an embodiment of the present application, step two specifically comprises:

[0018] Step 201: an adhesion layer and a bonding layer are sequentially deposited on the surface of the gallium nitride epitaxial wafer and the surface of the temporary substrate by an electron beam evaporation process, wherein the thickness of the adhesion layer is 40 nm, and the material is Ti, and the thickness of the bonding layer is 400 nm, and the material is Au;

[0019] Step 202: the bonding layer on the surface of the gallium nitride epitaxial wafer and the bonding layer on the surface of the temporary substrate are attached, the gallium nitride epitaxial wafer and the temporary substrate are clamped by a clamp and placed in a wafer bonding machine for hot-press bonding, wherein the bonding temperature is 450℃, and the pressure application time is 60 minutes.

[0020] In an embodiment of the present application, step three specifically comprises:

[0021] Step 301: the bottom surface of the temporary substrate in the first bonded wafer is attached to a UV film;

[0022] Step 302: the first bonded wafer is placed in a wafer thinning machine, and the substrate layer in the first bonded wafer is subjected to a thinning treatment by the wafer thinning machine, so that the thickness of the substrate layer is thinned to 100μm;

[0023] Step 303: the first bonded wafer is placed in a deep silicon etching device, and the substrate layer in the first bonded wafer is subjected to an etching treatment by the deep silicon etching device, so as to remove the substrate layer in the first bonded wafer;

[0024] Step 304: the surface of the gallium nitride epitaxial layer in the first bonded wafer is subjected to a polishing treatment, so that the roughness of the surface of the gallium nitride epitaxial layer is less than 1nm, and a first sample is obtained.

[0025] In one embodiment of the present invention, step four specifically includes:

[0026] Step 401: Place the first sample on the sample tray of the spin coater, drop photoresist at the center of the gallium nitride epitaxial layer surface of the first sample, set the spin coater speed to 4000 r / min and the motion time to 30 seconds, so that the photoresist is evenly distributed on the surface of the gallium nitride epitaxial layer.

[0027] Step 402: Place the first sample on a hot plate at 100°C and dry for 90 seconds;

[0028] Step 403: Place the first sample in the photolithography machine, expose the first sample for 2.3 seconds and develop it for 45 seconds based on the first preset mask, so as to copy the pattern of the first preset mask onto the photoresist of the first sample;

[0029] Step 404: Place the first sample on a hot plate at 100°C and dry for 120 seconds to cure the photoresist on the first sample;

[0030] Step 405: Etch the surface of the gallium nitride epitaxial layer in the first sample using ICP process;

[0031] Step 406: Clean the first sample sequentially with acetone, anhydrous ethanol and deionized water to remove the remaining photoresist on the first sample, and then dry the first sample.

[0032] In one embodiment of the present invention, step five specifically includes:

[0033] Step 501: Provide a diamond substrate, place the diamond substrate on the sample tray of the spin coater, drop photoresist at the center of the diamond substrate surface, set the spin coater speed to 3000 r / min and the motion time to 30 seconds, so that the photoresist is evenly distributed on the diamond substrate surface.

[0034] Step 502: Place the diamond substrate on a hot plate at 110°C and dry for 70 seconds;

[0035] Step 503: Place the diamond substrate in the photolithography machine, expose the diamond substrate for 45 seconds and develop it for 60 seconds based on the second preset mask, so as to copy the pattern of the second preset mask onto the photoresist of the diamond substrate.

[0036] Step 504: Etch the surface of the diamond substrate using ICP process;

[0037] Step 505: Clean the diamond substrate sequentially with acetone, anhydrous ethanol and deionized water to remove the remaining photoresist on the diamond substrate, and then dry the diamond substrate.

[0038] In one embodiment of the present application, the first preset mask and the second preset mask are the same mask, and one of the fourth step and the fifth step uses positive photoresist and the other uses negative photoresist.

[0039] In one embodiment of the present application, the sixth step specifically comprises:

[0040] Step 601: growing SiO2 on the surface of the first sample after photolithography and the surface of the diamond substrate, respectively;

[0041] Step 602: performing oxygen plasma treatment on the surface of the first sample and the surface of the diamond substrate, respectively;

[0042] Step 603: rinsing the first sample and the diamond substrate with RCA1 solution and deionized water in sequence and spin-drying, so that the surface of the first sample and the surface of the diamond substrate have hydrophilicity;

[0043] Step 604: placing the first sample and the diamond substrate into a bonding alignment module of a photolithography machine, and aligning and clamping the recess on the surface of the gallium nitride epitaxial layer and the protrusion on the surface of the diamond substrate through a microscope;

[0044] Step 605: placing the first sample and the diamond substrate into a wafer bonding device for bonding, setting the bonding temperature of the wafer bonding device to 30°C, the bonding pressure to 12000N, and the pressurizing time to 5 hours;

[0045] Step 606: annealing the bonded first sample and the diamond substrate at 400°C for 1 hour to obtain a second bonded wafer.

[0046] In one embodiment of the present application, the sixth step comprises:

[0047] Step 601: performing hydrophilic treatment on the surface of the first sample after photolithography and the surface of the diamond substrate;

[0048] Step 602: placing the diamond substrate into an NH4OH / H2O2 mixed solution and soaking at a temperature of 70°C for 10-15 minutes, and placing the first sample into an HCl solution and soaking at a temperature of 70°C for 10-15 minutes, so that the surface of the diamond substrate and the surface of the gallium nitride epitaxial layer of the first sample both generate OH ends;

[0049] Step 603: placing the first sample and the diamond substrate into a bonding alignment module of a photolithography machine, and aligning and clamping the recess on the surface of the gallium nitride epitaxial layer and the protrusion on the surface of the diamond substrate through a microscope;

[0050] Step 604: Put the first sample and the diamond substrate into a wafer bonding device for bonding, set the bonding temperature of the wafer bonding device to 200 DEG C, the bonding pressure to 12000N, and the pressurizing time to 2 hours, to obtain a second bonded wafer.

[0051] In one embodiment of the present application, step seven comprises:

[0052] Step 701: Attach the bottom surface of the diamond substrate in the second bonded wafer to a UV film.

[0053] Step 702: Put the second bonded wafer into a wafer thinning machine to perform thinning processing on the temporary substrate in the second bonded wafer, so that the thickness of the temporary substrate is thinned to 100 mu m.

[0054] Step 703: Corrode the remaining temporary substrate on the second bonded wafer by using a solution composed of acetic acid, nitric acid and hydrofluoric acid.

[0055] Step 704: Remove the bonding material layer by using a potassium iodide and hydrofluoric acid solution, to obtain a diamond-based gallium nitride wafer.

[0056] In one embodiment of the present application, the surface of the gallium nitride epitaxial layer is formed with a plurality of grooves, and the plurality of grooves are sequentially arranged along the length direction of the gallium nitride epitaxial layer.

[0057] The surface of the diamond substrate is formed with a plurality of protrusions, and the plurality of protrusions are sequentially arranged along the length direction of the diamond substrate, and the plurality of protrusions and the plurality of grooves correspond one by one.

[0058] Compared with the prior art, the present application has the following beneficial effects:

[0059] In the above scheme, first, a gallium nitride epitaxial wafer and a temporary substrate are provided, the gallium nitride epitaxial wafer includes a substrate layer and a gallium nitride epitaxial layer, so that the gallium nitride epitaxial layer can be formed by growing a gallium nitride thin film on the substrate layer. Second, a bonding material layer is prepared, the gallium nitride epitaxial wafer, the bonding material layer and the temporary substrate are stacked in sequence and subjected to first bonding to form a first bonded wafer, the gallium nitride epitaxial layer and the bonding material layer are in contact, so that the surface of the gallium nitride epitaxial wafer can be bonded with the temporary substrate, and the temporary substrate is convenient for removing the substrate layer. Then, the substrate layer in the first bonded wafer is removed to obtain a first sample, so that the substrate layer is separated from the gallium nitride epitaxial wafer. Then, the gallium nitride epitaxial layer in the first sample is etched to form a groove on the surface of the gallium nitride epitaxial layer, a diamond substrate is provided, the diamond substrate is etched to form a protrusion on the surface of the diamond substrate, the protrusion on the surface of the diamond substrate is matched with the groove on the surface of the gallium nitride epitaxial layer, the protrusion on the surface of the diamond substrate is clamped into the groove on the surface of the gallium nitride epitaxial layer, and the diamond substrate and the gallium nitride epitaxial layer are subjected to second bonding to obtain a second bonded wafer. Finally, the temporary substrate and the bonding material layer in the second bonded wafer are removed to obtain a gallium nitride-on-diamond wafer. By etching the groove on the surface of the gallium nitride epitaxial layer and etching the protrusion on the surface of the diamond substrate, the contact area between the gallium nitride epitaxial layer and the diamond substrate can be increased, more chemical bonds can be formed between the gallium nitride epitaxial layer and the diamond substrate, and the bonding strength between the gallium nitride epitaxial layer and the diamond substrate is enhanced. Moreover, when the protrusion on the diamond substrate is clamped into the groove on the gallium nitride epitaxial layer, the locking structure between the protrusion and the groove can make the bonding between the gallium nitride epitaxial layer and the diamond substrate more firm and reliable, and the stability of the bonding between the gallium nitride epitaxial layer and the diamond substrate is improved.

[0060] The application will be further described in detail below with reference to the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0061] Figure 1 is a wafer integration method for improving the bonding strength of gallium nitride and diamond provided by an embodiment of the application;

[0062] Figure 2 is a schematic diagram of a gallium nitride epitaxial wafer in an embodiment of the application;

[0063] Figure 3 is a schematic diagram of a temporary substrate in an embodiment of the application;

[0064] Figure 4 is a schematic diagram of a first bonded wafer in an embodiment of the application;

[0065] Figure 5 is a schematic diagram of the position of the first bonded wafer in a wafer thinning machine in an embodiment of the application;

[0066] Figure 6 is a schematic diagram of the substrate layer being thinned to 100 μm in the embodiment of the present application;

[0067] Figure 7 is a schematic diagram of the first sample in the embodiment of the present application;

[0068] Figure 8 is a schematic diagram of the surface etching groove of the gallium nitride epitaxial layer in the embodiment of the present application;

[0069] Figure 9 is a schematic diagram of the surface etching protrusion of the diamond substrate in the embodiment of the present application;

[0070] Figure 10 is a schematic diagram of the gallium nitride epitaxial layer and the gallium nitride epitaxial layer corresponding to the embodiment of the present application;

[0071] Figure 11 is a schematic diagram of the second bonding wafer provided with silicon dioxide in the embodiment of the present application;

[0072] Figure 12 is a schematic diagram of the position of the second bonding wafer provided with silicon dioxide in the wafer thinning machine in the embodiment of the present application;

[0073] Figure 13 is a schematic diagram of the diamond-based gallium nitride wafer provided with silicon dioxide in the embodiment of the present application;

[0074] Figure 14 is a schematic diagram of the second bonding wafer not provided with silicon dioxide in the embodiment of the present application;

[0075] Figure 15 is a schematic diagram of the position of the second bonding wafer not provided with silicon dioxide in the wafer thinning machine in the embodiment of the present application;

[0076] Figure 16 is a schematic diagram of the diamond-based gallium nitride wafer not provided with silicon dioxide in the embodiment of the present application. DETAILED DESCRIPTION

[0077] The present application will be further described in detail below with specific embodiments, but the embodiments of the present application are not limited thereto.

[0078] Please refer to Figures 1 to 16 The embodiment of the present application provides a wafer integration method for improving the bonding strength of gallium nitride and diamond, which comprises the following steps:

[0079] Step 1: providing a gallium nitride epitaxial wafer and a temporary substrate, the gallium nitride epitaxial wafer comprising a substrate layer and a gallium nitride epitaxial layer;

[0080] Step two: a bonding material layer is prepared, the gallium nitride epitaxial wafer, the bonding material layer and the temporary substrate are stacked in sequence and subjected to first bonding to form a first bonded wafer, and the gallium nitride epitaxial layer and the bonding material layer are in contact;

[0081] Step three: the substrate layer in the first bonded wafer is removed to obtain a first sample;

[0082] Step four: the gallium nitride epitaxial layer in the first sample is etched to form a groove on the surface of the gallium nitride epitaxial layer;

[0083] Step five: a diamond substrate is provided, and the diamond substrate is etched to form a protrusion on the surface of the diamond substrate, the protrusion and the groove are matched;

[0084] Step six: the protrusion on the surface of the diamond substrate and the groove on the surface of the gallium nitride epitaxial layer are clamped, and the diamond substrate and the gallium nitride epitaxial layer are subjected to second bonding to obtain a second bonded wafer;

[0085] Step seven: the temporary substrate and the bonding material layer in the second bonded wafer are removed to obtain a diamond-based gallium nitride wafer.

[0086] In some embodiments of the present application, the gallium nitride epitaxial wafer includes but is not limited to a silicon-based gallium nitride epitaxial wafer, a sapphire-based gallium nitride epitaxial wafer and a silicon carbide-based gallium nitride epitaxial wafer, etc.

[0087] In some embodiments of the present application, the substrate layer is a silicon substrate.

[0088] In some embodiments of the present application, the temporary substrate includes but is not limited to a silicon wafer, a sapphire wafer and a silicon carbide wafer, etc. The temporary substrate in the present embodiment is a silicon substrate.

[0089] In some embodiments of the present application, the temporary bonding layer material can be a medium, a metal layer or a bonding glue.

[0090] In some embodiments of the present application, the method for removing the substrate layer on the gallium nitride epitaxial wafer can be selected from mechanical grinding, dry etching or laser removal, etc.

[0091] In some embodiments of the present application, the size of the gallium nitride epitaxial wafer is equal to the size of the temporary substrate.

[0092] In some embodiments of the present application, the groove can be a rectangular slot with an opening facing the diamond substrate, and the protrusion can be a rectangular protrusion arranged outwardly and protruding towards the gallium nitride epitaxial layer.

[0093] In the above scheme, first, a gallium nitride epitaxial wafer and a temporary substrate are provided, the gallium nitride epitaxial wafer includes a substrate layer and a gallium nitride epitaxial layer, so that the gallium nitride epitaxial layer can be formed by growing a gallium nitride thin film on the substrate layer. Second, a bonding material layer is prepared, the gallium nitride epitaxial wafer, the bonding material layer and the temporary substrate are stacked in sequence and subjected to first bonding to form a first bonded wafer, the gallium nitride epitaxial layer and the bonding material layer are in contact, so that the surface of the gallium nitride epitaxial wafer can be bonded with the temporary substrate, and the temporary substrate is convenient for removing the substrate layer. Then, the substrate layer in the first bonded wafer is removed to obtain a first sample, so that the substrate layer is separated from the gallium nitride epitaxial wafer. Then, the gallium nitride epitaxial layer in the first sample is etched to form a groove on the surface of the gallium nitride epitaxial layer, a diamond substrate is provided, the diamond substrate is etched to form a protrusion on the surface of the diamond substrate, the protrusion on the surface of the diamond substrate is matched with the groove on the surface of the gallium nitride epitaxial layer, the protrusion on the surface of the diamond substrate is clamped into the groove on the surface of the gallium nitride epitaxial layer, and the diamond substrate and the gallium nitride epitaxial layer are subjected to second bonding to obtain a second bonded wafer. Finally, the temporary substrate and the bonding material layer in the second bonded wafer are removed to obtain a gallium nitride-on-diamond wafer. By etching the groove on the surface of the gallium nitride epitaxial layer and the protrusion on the surface of the diamond substrate, the contact area between the gallium nitride epitaxial layer and the diamond substrate can be increased, more chemical bonds can be formed between the gallium nitride epitaxial layer and the diamond substrate, and the bonding strength between the gallium nitride epitaxial layer and the diamond substrate is enhanced. Moreover, when the protrusion on the diamond substrate is clamped into the groove on the gallium nitride epitaxial layer, the locking structure between the protrusion and the groove can make the bonding between the gallium nitride epitaxial layer and the diamond substrate more firm and reliable, and the stability of the bonding between the gallium nitride epitaxial layer and the diamond substrate is improved. The corresponding patterns of the concave-convex formed on the surfaces of the gallium nitride and the diamond substrate after lithography are similar to the mortise-tenon structure in buildings, that is, the convex part is the tenon and the concave part is the mortise. When the wafer is bonded, the tenon and the mortise are mutually inserted, engaged, extruded and rubbed, so that the gallium nitride and the diamond substrate are tightly connected together, the surfaces of the two are tightly attached, the intermolecular force is enhanced, a strong binding force is generated, firm connection is achieved, and the gallium nitride and the diamond substrate are difficult to separate, so that the bonding between the gallium nitride and the diamond substrate is more firm and reliable and has higher stability.

[0094] In some embodiments of the present application, after step one and before step two, the method further includes:

[0095] cleaning the gallium nitride epitaxial wafer and the temporary substrate;

[0096] The gallium nitride epitaxial wafer and the temporary substrate are cleaned by 10% hydrochloric acid for 1 minute, then rinsed by deionized water for 9 minutes, and finally subjected to spin-drying treatment. In this way, the gallium nitride epitaxial wafer and the temporary substrate can be fully cleaned before being bonded, so that the cleanliness of the gallium nitride epitaxial wafer and the temporary substrate during bonding is improved, thereby achieving better bonding effect of the gallium nitride epitaxial wafer and the temporary substrate.

[0097] In some embodiments of the present application, the gallium nitride epitaxial wafer and the temporary substrate can be placed in a spin-dryer for spin-drying treatment, and the spin-drying treatment time can be 13 minutes to ensure the dryness of the gallium nitride epitaxial wafer and the temporary substrate.

[0098] In some embodiments of the present application, as shown in Figure 2 、 Figure 3 and Figure 4 , step two specifically includes:

[0099] Step 201: An adhesion layer and a bonding layer are sequentially deposited on the surface of the gallium nitride epitaxial wafer and the surface of the temporary substrate by an electron beam evaporation process, wherein the thickness of the adhesion layer is 40 nm, and the material is Ti (titanium), and the thickness of the bonding layer is 400 nm, and the material is Au (gold);

[0100] Step 202: The bonding layer on the surface of the gallium nitride epitaxial wafer and the bonding layer on the surface of the temporary substrate are attached, the gallium nitride epitaxial wafer and the temporary substrate are clamped by a clamp and placed in a wafer bonder for thermal pressure bonding, wherein the bonding temperature is 450°C, and the pressure application time is 60 minutes. In this way, the reliability of the bonding between the gallium nitride epitaxial layer and the temporary substrate can be improved.

[0101] In some embodiments of the present application, after the gallium nitride epitaxial wafer and the temporary substrate are clamped by the clamp and placed in the wafer bonder for thermal pressure bonding for 60 minutes, the pressure is removed and the temperature is lowered, and the first bonded wafer is taken out after the temperature slowly decreases to room temperature.

[0102] In some embodiments of the present application, as shown in Figure 5 、 Figure 6 and Figure 7 , step three specifically includes:

[0103] Step 301: The bottom surface of the temporary substrate in the first bonded wafer is attached to a UV film;

[0104] Step 302: The first bonded wafer is placed in a wafer thinning machine, and the substrate layer in the first bonded wafer is thinned by the wafer thinning machine, so that the thickness of the substrate layer is thinned to 100 μm;

[0105] Step 303: placing the first bonded wafer into a deep silicon etching device, and etching the substrate layer in the first bonded wafer by the deep silicon etching device to remove the substrate layer in the first bonded wafer;

[0106] Step 304: polishing the surface of the gallium nitride epitaxial layer in the first bonded wafer to make the roughness of the surface of the gallium nitride epitaxial layer less than 1 nm and obtain a first sample. By this method, the substrate layer in the gallium nitride epitaxial wafer can be fully removed by first thinning the substrate layer, then etching to remove the substrate layer, and finally polishing the surface of the gallium nitride epitaxial layer in the first bonded wafer, which improves the effect of subsequent bonding and makes it more convenient to remove the substrate layer.

[0107] In some embodiments of the present application, as shown in Figure 8 Step four specifically includes:

[0108] Step 401: placing the first sample on a sample disc of a spin coating device, dropping photoresist at the center of the surface of the gallium nitride epitaxial layer of the first sample, setting the rotation speed of the spin coating device to 4000 r / min, and setting the motion time to 30 seconds to make the photoresist uniformly distributed on the surface of the gallium nitride epitaxial layer;

[0109] Step 402: placing the first sample on a hot plate at 100°C and drying for 90 seconds;

[0110] Step 403: placing the first sample in a photoetching machine, exposing the first sample based on the first preset mask for 2.3 seconds and developing for 45 seconds to copy the pattern of the first preset mask to the photoresist on the first sample;

[0111] Step 404: placing the first sample on a hot plate at 100°C and drying for 120 seconds to solidify the photoresist on the first sample;

[0112] Step 405: etching the surface of the gallium nitride epitaxial layer in the first sample by ICP process;

[0113] Step 406: sequentially cleaning the first sample with acetone, anhydrous ethanol and deionized water to remove the remaining photoresist on the first sample, and then drying the first sample. By this method, a groove can be etched on the surface of the gallium nitride epitaxial layer of the first sample by photoetching process.

[0114] In some embodiments of the present application, the type of photoresist can be AZ6130.

[0115] In some embodiments of the present application, when developing the first sample, the first sample can be placed in a developing solution for development.

[0116] In some embodiments of the present application, the ICP process (Inductively Coupled Plasma) is mainly used in integrated circuit packaging and semiconductor manufacturing. The main purpose of the ICP process is to protect the chip, provide electrical connection and heat dissipation, etc., to ensure the reliability, stability and performance of the chip. The ICP etching technology is an inductively coupled plasma etching, whose working principle is to ionize the working gas by high-frequency electromagnetic field to form plasma. These plasmas induce current under the action of magnetic field, generate heat and reach high temperature state. Under the condition of vacuum low pressure, these plasmas bombard the surface of the substrate, break the chemical bonds of the substrate material, generate volatile substances and are pumped away. The ICP etching technology has the advantages of fast etching rate, high selectivity, high anisotropy and small etching damage, and is widely used in the etching of silicon, silicon dioxide, III-V compounds, metals and other materials.

[0117] In some embodiments of the present application, as shown in Figure 9 Step five specifically includes:

[0118] Step 501: providing a diamond substrate, placing the diamond substrate on the sample disc of the glue uniformizing device, dropping photoresist at the center of the surface of the diamond substrate, setting the rotation speed of the glue uniformizing device to 3000 r / min, and setting the motion time to 30 seconds, so that the photoresist is uniformly distributed on the surface of the diamond substrate;

[0119] Step 502: placing the diamond substrate on a hot plate at 110°C for drying for 70 seconds;

[0120] Step 503: placing the diamond substrate in a photoetching machine, exposing the diamond substrate based on a second preset mask for 45 seconds and developing for 60 seconds, so as to copy the pattern of the second preset mask to the photoresist on the diamond substrate;

[0121] Step 504: etching the surface of the diamond substrate by ICP process;

[0122] Step 505: sequentially cleaning the diamond substrate with acetone, anhydrous ethanol and deionized water to remove the remaining photoresist on the diamond substrate, and then drying the diamond substrate. By this method, the photoetching process can be used to etch a convex on the surface of the diamond substrate.

[0123] In some embodiments of the present application, the model of the photoresist can be AZ6130.

[0124] In some embodiments of the present application, when developing the diamond substrate, the diamond substrate can be placed in a developing solution for development.

[0125] In some embodiments of the present application, the first and second preset masks are the same mask, and one of steps four and five uses positive photoresist and the other uses negative photoresist. In this way, the size of the groove on the surface of the gallium nitride epitaxial layer and the size of the protrusion on the surface of the diamond substrate are equal and correspond to each other, facilitating the clamping of the protrusion and the groove, improving the stability and fit of the clamping of the protrusion and the groove, and further improving the bonding effect between the gallium nitride epitaxial layer and the diamond substrate.

[0126] In an alternative way, as shown in Figure 10 、 Figure 11 、 Figure 12 and Figure 13 , step six specifically includes:

[0127] Step 601: growing SiO2 on the surface of the first sample after lithography and the surface of the diamond substrate;

[0128] Step 602: performing oxygen plasma treatment on the surface of the first sample and the surface of the diamond substrate, respectively;

[0129] Step 603: rinsing the first sample and the diamond substrate with RCA1 solution and deionized water in sequence and spin-drying to make the surface of the first sample and the surface of the diamond substrate hydrophilic;

[0130] Step 604: placing the first sample and the diamond substrate into the bonding alignment module of the MA6 lithography machine, and aligning and clamping the groove on the surface of the gallium nitride epitaxial layer and the protrusion on the surface of the diamond substrate through a microscope;

[0131] Step 605: placing the first sample and the diamond substrate into a wafer bonding device for bonding, setting the bonding temperature of the wafer bonding device to 30℃, the bonding pressure to 12000N, and the pressurization time to 5 hours;

[0132] Step 606: annealing the bonded first sample and the diamond substrate at 400℃ for 1 hour to obtain a second bonded wafer. In this way, the strength and reliability of the bonding between the gallium nitride epitaxial layer and the diamond substrate can be improved, and the gallium nitride epitaxial layer can be prevented from falling off the diamond substrate.

[0133] In some embodiments of the present application, the first sample and the diamond substrate after lithography can be placed in a PECVD device to grow SiO2(dioxygen). The PECVD device (Plasma Enhanced Chemical Vapor Deposition) is a device that uses plasma technology to promote chemical reactions, mainly used for depositing high-quality thin film materials on the surface of the substrate. The PECVD device has the characteristics of high deposition rate, high uniformity and high adhesion, and can prepare high-quality and high-performance thin film materials.

[0134] In some embodiments of the present application, the first sample and the diamond substrate after growing SiO2 can be subjected to oxygen plasma treatment by RIE equipment. The RIE (Reactive Ion Etching) equipment is a dry etching equipment. Its working principle is to generate plasma between electrodes by using radio frequency power in a vacuum environment. The active ions in the plasma accelerate and bombard the surface of the sample under the action of the electric field, and at the same time, the chemical reaction with the sample material generates volatile products which are pumped away by the vacuum pump, thereby achieving material etching.

[0135] In some embodiments of the present application, the RCA1 solution is a cleaning solution used in semiconductor manufacturing, mainly used for removing organic contaminants and particles on silicon wafers. The RCA1 solution is composed of three chemicals: ammonium hydroxide, hydrogen peroxide and deionized water, with a ratio of 1:1:51.

[0136] In another alternative way, as shown in Figure 10 、 Figure 14 、 Figure 15 and Figure 16 , step six includes:

[0137] Step 601: hydrophilic treatment is performed on the surface of the first sample after lithography and the surface of the diamond substrate;

[0138] Step 602: the diamond substrate is placed in an NH4OH / H2O2 mixed solution and soaked at a temperature of 70°C for 10-15 minutes, and the first sample is placed in an HCl solution and soaked at a temperature of 70°C for 10-15 minutes, so that the surface of the diamond substrate and the surface of the gallium nitride epitaxial layer of the first sample are both generated OH end;

[0139] Step 603: the first sample and the diamond substrate are placed in the bonding alignment module of the lithography machine, and the groove on the surface of the gallium nitride epitaxial layer and the protrusion on the surface of the diamond substrate are aligned and clamped by a microscope;

[0140] Step 604: Put the first sample and the diamond substrate into a wafer bonding device for bonding, set the bonding temperature of the wafer bonding device to 200 DEG C, the bonding pressure to 12000N, and the pressurizing time to 2 hours, to obtain a second bonded wafer. By this method, the strength and reliability of the bonding between the gallium nitride epitaxial layer and the diamond substrate can be improved, and the gallium nitride epitaxial layer can be prevented from falling off the diamond substrate.

[0141] In some embodiments of the present application, as shown in Figure 12 、 Figure 13 、 Figure 15 and Figure 16 , step seven comprises:

[0142] Step 701: Attach the bottom surface of the diamond substrate in the second bonded wafer to a UV film;

[0143] Step 702: Put the second bonded wafer into a wafer thinning machine, and perform a thinning process on the temporary substrate in the second bonded wafer, so that the thickness of the temporary substrate is thinned to 100 μm;

[0144] Step 703: Corrode the remaining temporary substrate on the second bonded wafer by using a solution composed of acetic acid, nitric acid and hydrofluoric acid;

[0145] Step 704: Remove the bonding material layer by using a potassium iodide and hydrofluoric acid solution, to obtain a diamond-based gallium nitride wafer. By this method, the temporary substrate and the bonding material layer on the second bonded wafer can be removed, and the desired diamond-based gallium nitride wafer can be obtained.

[0146] In some embodiments of the present application, when the bonding material layer is removed by using the potassium iodide and hydrofluoric acid solution, Au (gold) and Ti (titanium) in the bonding material layer can be removed.

[0147] In addition, the terms "first", "second", "third", etc. are used only for descriptive purposes and should not be construed as indicating or implying relative importance or an indicated number of technical features. Therefore, the features defined as "first", "second", etc. can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0148] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate different embodiments or examples described in the specification.

[0149] The above is a further detailed description of the present application in combination with specific preferred embodiments, and cannot be considered as limiting the specific implementation of the present application to these descriptions. For those skilled in the art, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, which should be considered as falling within the protection scope of the present application.

Claims

1. A wafer integration method for improving bonding strength of gallium nitride and diamond, characterized by, The method comprises the following steps: Step 1: providing a gallium nitride epitaxial wafer and a temporary substrate, wherein the gallium nitride epitaxial wafer comprises a substrate layer and a gallium nitride epitaxial layer; Step 2: preparing a bonding material layer, stacking the gallium nitride epitaxial wafer, the bonding material layer and the temporary substrate in sequence and performing first bonding to form a first bonded wafer, wherein the gallium nitride epitaxial layer is in contact with the bonding material layer; Step 3: removing the substrate layer in the first bonded wafer to obtain a first sample; Step 4: etching the gallium nitride epitaxial layer in the first sample to form a groove on the surface of the gallium nitride epitaxial layer; Step 5: providing a diamond substrate, etching the diamond substrate to form a protrusion on the surface of the diamond substrate, wherein the protrusion is matched with the groove; Step 6: clamping the protrusion on the surface of the diamond substrate and the groove on the surface of the gallium nitride epitaxial layer, and performing second bonding on the diamond substrate and the gallium nitride epitaxial layer to obtain a second bonded wafer; Step 7: removing the temporary substrate and the bonding material layer in the second bonded wafer to obtain a diamond-based gallium nitride wafer; In the step 6, the method comprises the following steps: Step 601: growing SiO2 on the surface of the first sample after photolithography and the surface of the diamond substrate; Step 602: performing oxygen ion plasma treatment on the surface of the first sample and the surface of the diamond substrate respectively; Step 603: sequentially rinsing the first sample and the diamond substrate with RCA1 solution and deionized water and spin-drying to make the surface of the first sample and the surface of the diamond substrate hydrophilic; Step 604: placing the first sample and the diamond substrate into a bonding alignment module of a photolithography machine, aligning and clamping the groove on the surface of the gallium nitride epitaxial layer and the protrusion on the surface of the diamond substrate through a microscope; Step 605: placing the first sample and the diamond substrate into a wafer bonding device for bonding, setting the bonding temperature of the wafer bonding device to 30 DEG C, the bonding pressure to 12000 N and the pressurizing time to 5 hours; Step 606: annealing the bonded first sample and the diamond substrate at 400 DEG C for 1 hour to obtain a second bonded wafer.

2. The wafer integration method for improving bonding strength of gallium nitride and diamond according to claim 1, wherein After the step 1 and before the step 2, the method further comprises the following steps: cleaning the gallium nitride epitaxial wafer and the temporary substrate; wherein the gallium nitride epitaxial wafer and the temporary substrate are cleaned with 10% hydrochloric acid for 1 minute, then rinsed with deionized water for 9 minutes, and finally spin-dried.

3. The wafer integration method for improving bonding strength of gallium nitride and diamond according to claim 1, wherein The step 2 comprises the following step: Step 201: using an electron beam evaporation process to deposit an adhesion layer and a bonding layer on the surface of the gallium nitride epitaxial wafer and the surface of the temporary substrate in sequence, wherein the thickness of the adhesion layer is 40 nm and the material is Ti, and the thickness of the bonding layer is 400 nm and the material is Au; Step 202: The bonding layer on the surface of the gallium nitride epitaxial wafer and the bonding layer on the surface of the temporary substrate are attached, the gallium nitride epitaxial wafer and the temporary substrate are clamped by a clamp and placed in a wafer bonding machine for thermal pressure bonding, wherein the bonding temperature is 450°C, and the pressure time is 60 minutes.

4. The wafer integration method for improving bonding strength of gallium nitride and diamond according to claim 1, wherein, The step three specifically includes: Step 301: The bottom surface of the temporary substrate in the first bonded wafer is attached to a UV film; Step 302: The first bonded wafer is placed in a wafer thinning machine, and the substrate layer in the first bonded wafer is thinned by the wafer thinning machine to reduce the thickness of the substrate layer to 100μm; Step 303: The first bonded wafer is placed in a deep silicon etching device, and the substrate layer in the first bonded wafer is etched by the deep silicon etching device to remove the substrate layer in the first bonded wafer; Step 304: The surface of the gallium nitride epitaxial layer in the first bonded wafer is polished to make the roughness of the surface of the gallium nitride epitaxial layer less than 1nm and obtain a first sample.

5. The wafer integration method for improving bonding strength of gallium nitride and diamond according to claim 1, wherein, The step four specifically includes: Step 401: The first sample is placed on a sample disc of a spin coating device, photoresist is dropped at the center of the surface of the gallium nitride epitaxial layer of the first sample, the rotation speed of the spin coating device is set to 4000r / min, and the motion time is set to 30 seconds, so that the photoresist is uniformly distributed on the surface of the gallium nitride epitaxial layer; Step 402: The first sample is placed on a hot plate at 100°C and dried for 90 seconds; Step 403: The first sample is placed in a photoetching machine, and the first sample is exposed based on a first preset mask for 2.3 seconds and developed for 45 seconds, so that the pattern of the first preset mask is copied to the photoresist on the first sample; Step 404: The first sample is placed on a hot plate at 100°C and dried for 120 seconds to solidify the photoresist on the first sample; Step 405: The surface of the gallium nitride epitaxial layer in the first sample is etched by ICP process; Step 406: The first sample is sequentially cleaned with acetone, anhydrous ethanol and deionized water to remove the remaining photoresist on the first sample, and then the first sample is dried.

6. The wafer integration method for improving bonding strength of gallium nitride and diamond according to claim 5, wherein, The step five specifically includes: Step 501: A diamond substrate is provided, the diamond substrate is placed on a sample disc of a spin coating device, photoresist is dropped at the center of the surface of the diamond substrate, the rotation speed of the spin coating device is set to 3000r / min, and the motion time is set to 30 seconds, so that the photoresist is uniformly distributed on the surface of the diamond substrate; Step 502: The diamond substrate is placed on a hot plate at 110°C and dried for 70 seconds; Step 503: The diamond substrate is placed in a photoetching machine, and the diamond substrate is exposed based on a second preset mask for 45 seconds and developed for 60 seconds, so that the pattern of the second preset mask is copied to the photoresist on the diamond substrate; Step 504: The surface of the diamond substrate is etched by ICP process; Step 505: sequentially clean the diamond substrate with acetone, anhydrous ethanol and deionized water to remove the photoresist remaining on the diamond substrate, and then dry the diamond substrate.

7. The wafer integration method for improving bonding strength of gallium nitride and diamond according to claim 6, wherein The first preset mask and the second preset mask are the same mask, and one of the step four and the step five uses positive photoresist and the other uses negative photoresist.

8. The wafer integration method for improving bonding strength of gallium nitride and diamond according to claim 1, wherein, The step six comprises: Step 601: performing hydrophilic treatment on the surface of the first sample after photoetching and the surface of the diamond substrate; Step 602: placing the diamond substrate into an NH4OH / H2O2 mixed solution and soaking at a temperature of 70℃ for 10-15 minutes, and placing the first sample into an HCl solution and soaking at a temperature of 70℃ for 10-15 minutes, so as to generate OH ends on the surface of the diamond substrate and the surface of the gallium nitride epitaxial layer of the first sample; Step 603: placing the first sample and the diamond substrate into a bonding alignment module of a photoetching machine, and aligning and clamping the recess on the surface of the gallium nitride epitaxial layer and the protrusion on the surface of the diamond substrate through a microscope; Step 604: placing the first sample and the diamond substrate into a wafer bonding device for bonding, setting the bonding temperature of the wafer bonding device to 200℃, the bonding pressure to 12000N, and the pressurizing time to 2 hours, to obtain a second bonded wafer.

9. The wafer integration method for improving bonding strength of gallium nitride and diamond according to claim 1, wherein, The step seven comprises: Step 701: attaching the bottom surface of the diamond substrate in the second bonded wafer to a UV film; Step 702: placing the second bonded wafer into a wafer thinning machine to perform thinning treatment on the temporary substrate in the second bonded wafer, so as to thin the thickness of the temporary substrate to 100μm; Step 703: corroding the remaining temporary substrate on the second bonded wafer with a solution composed of acetic acid, nitric acid and hydrofluoric acid; Step 704: removing the bonding material layer with a potassium iodide and hydrofluoric acid solution, to obtain a diamond-based gallium nitride wafer.

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