CN111900200A - Diamond-based gallium nitride composite wafer and bonding preparation method thereof - Google Patents

Abstract

A diamond-based gallium nitride composite wafer and a bonding preparation method thereof, the wafer has gallium nitride/nucleation layer/silicon carbide/metal intermediate layer/diamond substrate, gallium nitride/metal intermediate layer/diamond substrate, For structures such as gallium nitride/ceramic film layer/metal intermediate layer/diamond substrate, the main preparation steps are: thinning the silicon carbide substrate of gallium nitride, or completely peeling off the silicon carbide substrate and thinning the gallium nitride layer; Polish and argon plasma treatment on the surface to be bonded of silicon carbide substrate or gallium nitride layer and diamond; deposit metal buffer layer and gold film on the to-be-bonded surface of silicon carbide substrate, or on the gallium nitride layer to be bonded Deposit metal buffer layer and gold film or deposit ceramic film, metal buffer layer and gold film on the bonding surface, deposit metal buffer layer and gold film on the diamond surface to be bonded; first perform pre-bonding of gallium nitride and diamond, and then carry out Secondary bonding; annealing GaN-on-diamond composite wafers. The present invention can improve the bond strength.

Description

A kind of diamond-based gallium nitride composite wafer and bonding preparation method thereof

technical field

The invention belongs to the technical field of semiconductors and integrated circuits, in particular to a diamond-based gallium nitride composite wafer and a bonding preparation method thereof, which can be applied to the manufacture of microwave radio frequency devices and power electronic devices.

Background technique

As a third-generation semiconductor material, gallium nitride has the characteristics of large band gap, high breakdown field strength, high saturation electron velocity, high temperature resistance and radiation resistance compared with silicon and gallium arsenide materials. It is very suitable for The production of high-temperature and high-power devices, high-frequency microwave devices, and ultraviolet and nuclear radiation detection devices has extremely high application value in technical fields such as communications and power electronics. However, the severe self-heating effect and low thermal conductivity limit the full play of the inherent advantages of GaN devices, and become the technical bottleneck restricting the further development of GaN devices in the direction of high frequency and high power.

Diamond has a high thermal conductivity, which is nearly five times that of silicon carbide (one of the commonly used substrate materials for gallium nitride devices). Using diamond as a substrate material can effectively reduce the thermal resistance of gallium nitride devices. Lower AlGaN/GaN junction temperature. In recent years, international research has shown that gallium nitride devices using diamond substrates (GaN-on-diamond composite devices) and GaN devices using silicon carbide as substrates (GaN-on-SiC composite devices) In contrast, due to the solution of the heat dissipation problem, the output power density, power added efficiency and reliability of the device have been significantly improved, and the size of the module has been further reduced. Therefore, the use of diamond substrates is an effective method to solve the thermal management problem of GaN devices. GaN-on-diamond composite devices are developing into a mainstream technology for high-frequency and high-power semiconductor devices.

At present, there are three main methods for preparing GaN-on-diamond composite devices, namely, epitaxial growth of diamond on the surface of gallium nitride, epitaxial growth of gallium nitride on the surface of diamond, and bonding of gallium nitride and diamond. For the first two methods, due to the large mismatch between the thermal expansion coefficients of gallium nitride and diamond, the epitaxial growth of diamond or gallium nitride at a higher temperature will cause a large stress in the epitaxial layer, which is easy to cause the wafer to warp. In addition, the lattice constants of gallium nitride and diamond are also quite different, making it difficult to grow high-quality gallium nitride or diamond epitaxial layers. Different from the first two methods to prepare GaN-on-diamond composite devices by epitaxial growth of diamond or gallium nitride, the third method uses the bonding technology of gallium nitride and diamond. The optimal process can produce high-quality gallium nitride and diamond, and the bonding can be carried out at lower temperature or even room temperature, avoiding the problems caused by the mismatch of thermal expansion coefficient and lattice constant between the two materials. Using the bonding method to fabricate GaN-on-diamond composite devices, reducing the interface thermal resistance, reducing the bonding void ratio and improving the bonding strength are the keys to obtain high bonding quality.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the problems existing in the preparation of gallium nitride devices, to provide a diamond-based gallium nitride composite wafer and a bonding preparation method thereof, which can effectively reduce the interface thermal resistance between gallium nitride and diamond, and reduce the bonding void ratio. And improve the bonding strength, so as to prepare high-performance GaN-on-diamond composite wafers, and improve the play of the advantages of GaN devices.

In order to achieve the above object, the present invention adopts the following technical scheme:

A gallium nitride-on-diamond composite wafer having any one of the following a), b) and c) structures:

a) a multilayer structure formed by gallium nitride, nucleation layer, silicon carbide, metal intermediate layer, and diamond substrate in sequence;

b) a multilayer structure formed by gallium nitride, a metal intermediate layer, and a diamond substrate in sequence;

c) a multi-layer structure formed by gallium nitride, a ceramic film layer, a metal intermediate layer, and a diamond substrate in sequence, and the material of the ceramic film layer is aluminum nitride or silicon carbide;

The metal intermediate layer has a three-layer structure of a metal buffer layer, a gold film layer and a metal buffer layer arranged in sequence; the material of the metal buffer layer is tungsten, molybdenum or aluminum.

As a preferred solution of the diamond-based gallium nitride composite wafer of the present invention, the thickness of the diamond substrate in the structures a), b) and c) is 100-2000 microns; the thickness of the metal buffer layer is 1-20 nanometers The thickness of the gold film layer is 5-200 nanometers; the layer thickness of silicon carbide in the described structure a) is 5-80 micrometers; the layer thickness of gallium nitride in the described structure b) is 1-3 micrometers; In the aforementioned structure c), the thickness of the gallium nitride layer is 1-3 micrometers, and the thickness of the ceramic film layer is 1-15 nanometers.

The present invention also provides a bonding preparation method of a diamond-based gallium nitride composite wafer, comprising the following steps:

1) bonding the surface of the gallium nitride epitaxial layer on the silicon carbide substrate gallium nitride with the temporary carrier with an adhesive;

2) thinning the silicon carbide substrate; or completely peeling off the silicon carbide substrate, removing the nucleation layer, and thinning the gallium nitride epitaxial layer;

3) Polish the surface of the thinned silicon carbide substrate or the surface of the thinned gallium nitride epitaxial layer, and polish the diamond surface, so that the silicon carbide substrate or the gallium nitride epitaxial layer and the diamond polished surface are polished. The roughness is lower than the required value;

4) ultrasonically clean gallium nitride and diamond with acetone, ethanol and deionized water successively;

5) The polishing surface of the silicon carbide substrate or the gallium nitride epitaxial layer is the surface to be bonded of gallium nitride, the polished surface of diamond is the surface to be bonded of diamond, and the surface to be bonded of gallium nitride and diamond is Argon plasma treatment;

6) successively deposit a metal buffer layer and a gold film layer on the surface to be bonded of gallium nitride of the thinned silicon carbide substrate, or successively deposit metal on the surface to be bonded of gallium nitride of the thinned epitaxial layer of gallium nitride Buffer layer and gold film layer or successively deposit ceramic film layer, metal buffer layer and gold film layer; successively deposit metal buffer layer and gold film layer on the surface to be bonded of diamond;

7) Place the surface to be bonded of gallium nitride and the surface to be bonded of diamond relative to each other and make them contact each other, and apply pressure to carry out the first bonding of gallium nitride and diamond, that is, pre-bonding;

8) applying pressure to bond the pre-bonded gallium nitride and diamond for the second time;

9) removing the adhesive and the temporary carrier on the gallium nitride surface of the diamond substrate to prepare a gallium nitride-on-diamond composite wafer;

10) annealing the diamond-based gallium nitride composite wafer to complete the preparation.

As a preferred solution of the bonding preparation method of the present invention, the adhesive described in step 1) is photoresist, benzocyclobutene or 502 glue; the material of the temporary carrier is silicon, alumina, carbonized Silicon, quartz or diamond, the surface roughness of the temporary slide is not higher than 10 nm.

As a preferred solution of the bonding preparation method of the present invention, step 2) using mechanical grinding to thin the silicon carbide substrate to 5-80 microns; or continuing to use inductively coupled plasma etching to etch away the remaining silicon carbide Substrate, remove the nucleation layer, and thin the GaN epitaxial layer to 1-3 microns;

Step 3) The required value of the roughness is 2 nanometers;

Step 6) The thickness of the metal buffer layer deposited on the surfaces to be bonded of gallium nitride and diamond is 1-20 nanometers, respectively, and the thickness of the gold film layer deposited on the surfaces to be bonded of gallium nitride and diamond is 2.5-100 nanometers, respectively , the thickness of the ceramic film layer deposited on the surface to be bonded of the gallium nitride is 1-15 nanometers.

As a preferred solution of the bonding preparation method of the present invention, the argon plasma used in the argon plasma treatment described in step 5) is generated by gas discharge, the discharge power is 30-200W, and the treatment time of the argon plasma is 0.5-200W. 20 minutes.

As a preferred solution of the bonding preparation method of the present invention, in step 7) after each film layer is deposited on the surface to be bonded of gallium nitride and diamond, the gallium nitride is subjected to mechanical pressure without exposing to the atmosphere. The first bonding with diamond, or taking out gallium nitride and diamond from the coating cavity, the first bonding of gallium nitride and diamond is carried out quickly by manual pressure or heavy object pressure at room temperature and atmospheric conditions. For secondary bonding, the applied pressure is 0.2-2MPa, and the pressing time is 1-3 minutes.

As a preferred solution of the bonding preparation method of the present invention, in step 8) when gallium nitride and diamond are bonded for the second time, the temperature of gallium nitride and diamond is lower than 150 ° C, and the applied pressure is 0.5-10 MPa, Pressurization time is 1-20 minutes.

As a preferred solution of the bonding preparation method of the present invention, the method of removing the adhesive and the temporary carrier sheet in step 9) is: put it into an acetone solution, and use ultrasonic vibration to accelerate the dissolution of the adhesive.

As a preferred solution of the bonding preparation method of the present invention, the annealing treatment in step 10) is performed in a vacuum environment or in a high-purity nitrogen atmosphere, the annealing temperature is 100-200° C., and the annealing time is 10-60 minutes.

Compared with the prior art, the present invention has the following beneficial effects:

In the prior art, titanium and chromium films are usually used as the buffer layer of the gold film bonding layer, and the titanium or chromium films have strong bonding force with silicon carbide, gallium nitride, diamond, gold films and other materials to improve the gold film. The bonding strength of the film to silicon carbide, gallium nitride, and diamond. However, the thermal conductivity of titanium and chromium is very low, about 21.9W/m·K and 93.7W/m·K, respectively, and using them as buffer layers will increase the thermal resistance between gallium nitride and diamond. The composite wafer of the present invention adopts tungsten, molybdenum and aluminum as buffer layers. These metal film layers not only have good bonding force with silicon carbide, gallium nitride and diamond, but also have high thermal conductivity (about 174W respectively). /m·K, 138W/m·K, 237W/m·K), using them as a buffer layer can reduce the thermal resistance between gallium nitride and diamond, which is beneficial to reduce the temperature of the hot spot area of the gallium nitride device. In addition, for the scheme of bonding the gallium nitride epitaxial layer with diamond after thinning, in order to prevent the metal atoms in the metal nano-bonding layer from diffusing into the gallium nitride and reducing the device performance, the thinned nitrogen A thin layer of aluminum nitride or silicon carbide ceramic film with high thermal conductivity is first deposited on the surface to be bonded of the gallium nitride epitaxial layer, and then a metal buffer layer and a gold film are deposited, and the ceramic film layer is used to block metal atoms from entering nitrogen gallium nitride can avoid the adverse effect of the presence of the metal bonding layer on the performance of the gallium nitride device.

The present invention adopts two technical solutions to prepare a diamond-based gallium nitride composite wafer. The first solution is to retain a silicon carbide substrate with a thickness of 5-80 microns of gallium nitride, and use the surface of the silicon carbide substrate as a bonding surface to bond with diamond. The advantage of this scheme is that the preparation process is relatively simple and the bonding power is high, but the disadvantage is that the thermal resistance of the prepared GaN-on-diamond composite device is high due to the existence of the silicon carbide substrate and the thick gallium nitride epitaxial layer. The second solution is to completely peel off the silicon carbide substrate and the nucleation layer, thin the gallium nitride to 1-3 microns, and use the surface of the thinned gallium nitride as the bonding surface to bond with the diamond. The distance between the hot spot area and the diamond substrate of the GaN-on-diamond composite device prepared by this scheme is relatively close, which is beneficial to the heat dissipation of the device. Therefore, these two technical solutions have their own advantages and disadvantages, and different technical solutions can be selected according to different actual needs.

Compared with the prior art, the bonding preparation method of the diamond-based gallium nitride composite wafer of the present invention has the following beneficial effects: The wafer is taken out from the coating machine and put into the bonding equipment for pressure bonding. Since it usually takes a long time to remove the wafer from the coating machine and put the wafer into the bonding equipment, during this period, the surface of the metal bonding layer will absorb more gas (such as water vapor) and even be contaminated with some dust particles, which will affect the gallium nitride. The interdiffusion of gold atoms on both sides of the bonding interface with diamond and the formation of metal bonds reduce the bonding quality. In the present invention, the bonding of gallium nitride and diamond is carried out in two steps, that is, after each film layer is deposited on the surfaces to be bonded of gallium nitride and diamond, pressure is applied to carry out gallium nitride and diamond without exposing to the atmosphere. pre-bonding, or take out gallium nitride and diamond from the cavity of the sputter coater, quickly apply pressure to pre-bond gallium nitride and diamond, and then pre-bond gallium nitride and diamond together The diamond is put into the bonding equipment for the second bonding of gallium nitride and diamond. Using the pre-bonding method can avoid the surface of the metal nano-bonding layer from being exposed to the air or minimize the exposure time to the air, and reduce the pollution caused by the adsorption of gas and dust particles on the surface of the metal nano-bonding layer, so as to ensure that the gallium nitride and the The two fresh gold film surfaces on the to-be-bonded surface of the diamond can sufficiently contact each other. After that, in order to increase the bonding strength, the pre-bonded samples are put into the bonding equipment for secondary bonding. Since the surfaces of the two gold films in contact with each other are very clean, the secondary bonding only needs to apply lower pressure. That is, bonding with low void ratio and high bonding strength can be realized. In the present invention, the surfaces to be bonded are treated with argon plasma before the metal nano-bonding layer is deposited, so that the surfaces to be bonded of gallium nitride and diamond can be cleaned thoroughly, and the silicon carbide substrate or the epitaxial layer of gallium nitride and the diamond can be strengthened. The bonding force between the substrate and the metal nanobond layer. In order to enhance the bonding strength between gallium nitride and diamond based on the metal nano-bonding layer, the present invention performs annealing treatment on the bonded diamond-based gallium nitride composite wafer, thereby enhancing the gold atoms on both sides of the gold/gold bonding interface. The interdiffusion of gallium nitride and diamond improves the bonding strength.

The invention improves the technological process and structural features, and can realize the preparation of high-performance diamond-based gallium nitride devices by using the diamond-based gallium nitride composite wafer and the corresponding bonding preparation method of the present invention.

Description of drawings

Fig. 1 is the process flow chart of the bonding method of gallium nitride and diamond based on metal nanolayer of the present invention;

Figure 2 Example 1 A structure of a GaN-on-diamond composite wafer prepared by the bonding method of the present invention (gallium nitride/nucleation layer/silicon carbide (5-80 microns)/metal buffer layer/gold film/ Metal buffer layer/diamond) schematic diagram;

Figure 3 Example 2 A structure of a GaN-on-diamond composite wafer prepared by the bonding method of the present invention (ie, gallium nitride (1-3 microns)/metal buffer layer/gold film/metal buffer layer/diamond) schematic diagram;

Figure 4 Example 3 A structure of a GaN-on-diamond composite wafer prepared by the bonding method of the present invention (ie, gallium nitride (1-3 microns)/ceramic film layer/metal buffer layer/gold film/metal buffer layer/diamond) schematic diagram;

Fig. 5 is the atomic force microscope image of the diamond substrate through surface polishing;

Fig. 6 AFM image of molybdenum buffer layer and gold thin film deposited on diamond substrate;

Figure 7 is an atomic force microscope image of a surface-polished gallium nitride layer;

Fig. 8 AFM image of the molybdenum buffer layer and the gold thin film deposited on the gallium nitride layer;

Fig. 9 Morphology of GaN-on-diamond composite wafer prepared by bonding method of the present invention/nucleation layer/silicon carbide (5-80 microns)/metal buffer layer/gold film/metal buffer layer/diamond multilayer structure picture;

Figure 10 is a topography of a GaN-on-diamond composite wafer with a gallium nitride (1-3 micron)/metal buffer layer/gold film/metal buffer layer/diamond multilayer structure prepared by the bonding method of the present invention;

Fig. 11 is an ultrasonic scanning microscope image of the GaN-on-diamond composite wafer prepared by the bonding method of the present invention.

In the drawings: 1—gallium nitride epitaxial layer, 2—nucleation layer, 3—silicon carbide substrate, 4—diamond substrate, 11—metal buffer layer, 12—gold film, 13—ceramic film layer.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

In order to solve the heat dissipation problem of high-frequency and high-power gallium nitride devices, the gallium nitride device is combined with a diamond substrate with high thermal conductivity, and the present invention adopts a bonding method based on metal nanolayers to prepare diamond substrates Gallium nitride composite wafer with gallium nitride/nucleation layer/silicon carbide/metal interlayer/diamond substrate, gallium nitride/metal interlayer/diamond substrate, gallium nitride/ceramic film layer/metal interlayer layer/diamond substrate, etc. The preparation method proposed by the present invention performs the bonding of gallium nitride and diamond in two steps, that is, after each film layer is deposited on the surfaces to be bonded of gallium nitride and diamond, and under the condition of not exposing to the atmosphere, a mechanical pressing method is adopted. Carry out pre-bonding of gallium nitride and diamond, or take out gallium nitride and diamond from the coating cavity, and use manual pressure or heavy object pressure to quickly carry out gallium nitride and diamond at room temperature and atmospheric conditions. Pre-bonding, and then secondary bonding of gallium nitride and diamond with bonding equipment. Using the pre-bonding method can avoid the surface of the metal nano-adhesive layer from being exposed to the air or minimize the exposure time to the air, and reduce the contamination of the surface of the metal nano-adhesion layer by the adsorption of gas and dust particles, so as to ensure two fresh gold The membrane surfaces are in contact with each other. In order to increase the bonding strength, the pre-bonded samples are put into the bonding equipment for secondary bonding. Since the surfaces of the two gold films in contact with each other are very clean, the secondary bonding only needs to apply a lower pressure. Obtain low bond voids and high bond strength. Before depositing the metal buffer layer, the surface to be bonded is treated with argon plasma, which can clean the surface to be bonded and enhance the bonding force between the silicon carbide substrate or the gallium nitride epitaxial layer and the diamond and the metal buffer layer to improve the bond combined quality. Tungsten, molybdenum and aluminum are used as buffer layers. These metal films not only have good bonding force with silicon carbide, gallium nitride, diamond and gold films, but also have high thermal conductivity. Use them as buffer layers. The layer is beneficial to reduce the temperature of the hot spot region of the gallium nitride device. In addition, for the scheme of thinning the gallium nitride epitaxial layer and then bonding it with diamond, in order to prevent the metal atoms in the metal nanolayer from diffusing into the gallium nitride and reducing the device performance, the thinned gallium nitride is used in the thinned gallium nitride. A thin aluminum nitride or silicon carbide ceramic film layer is deposited on the surface to be bonded of the epitaxial layer, and then a metal buffer layer and a gold film are deposited, and the ceramic film layer is used to block the metal atoms from entering the gallium nitride. In order to further increase the bonding strength between gallium nitride and diamond, the bonded diamond substrate gallium nitride is annealed to enhance the mutual diffusion of gold atoms on both sides of the gold/gold bonding interface.

Therefore, the diamond-based gallium nitride composite wafer and the bonding preparation method of the present invention can prepare a diamond-based gallium nitride composite wafer with low void ratio and high bonding strength, and can effectively solve the problem of high-frequency and high-power gallium nitride devices. cooling problem.

Example 1

1 and 2, the GaN-on-diamond composite wafer prepared by the present invention has the structure of gallium nitride/nucleation layer/silicon carbide (5-80 microns)/metal buffer layer/gold film/metal buffer layer/diamond , the specific preparation method comprises the following steps:

1) The surface of the gallium nitride epitaxial layer of the silicon carbide substrate gallium nitride and the silicon wafer (temporary carrier) are bonded together with photoresist;

2) Using mechanical grinding to thin the silicon carbide substrate to 40 microns;

3) Surface polishing is performed on the silicon carbide substrate and the diamond, so that the roughness of the polished surface of the silicon carbide substrate and the diamond is less than 2 nanometers;

4) ultrasonically clean gallium nitride and diamond with acetone, ethanol and deionized water successively;

5) Put the gallium nitride and diamond into the sputtering coater, use the polished surface of the silicon carbide substrate and the diamond as the surface to be bonded, and carry out argon plasma treatment on the surface to be bonded, and the plasma discharge power is 50W. The time is 5 minutes;

6) adopt sputtering deposition method, successively deposit 2 nanometer thick tungsten buffer layer and 10 nanometer thick gold film on the surface to be bonded of silicon carbide substrate and diamond;

7) After the tungsten buffer layer and the gold thin film are deposited on the surfaces to be bonded of the silicon carbide substrate and the diamond, the surface to be bonded of the silicon carbide substrate and the surface to be bonded of the diamond substrate are not exposed to the atmosphere. Place them relative to each other and make them in contact with each other, use mechanical pressure to pre-bond gallium nitride and diamond, apply a pressure of 0.3MPa and keep it for 3 minutes;

8) Put the pre-bonded gallium nitride and diamond into the bonding equipment, apply a pressure of 5 MPa to the gallium nitride and diamond and keep it for 5 minutes, carry out the second bonding, and bond the gallium nitride and the diamond substrate combine together;

9) Put the diamond substrate gallium nitride bonded on the temporary carrier into a container filled with acetone solution, and use ultrasonic vibration to accelerate the dissolution of the adhesive to remove the adhesive on the surface of the diamond substrate gallium nitride and a temporary slide to prepare a GaN-on-diamond composite wafer;

10) The gallium nitride-on-diamond composite wafer is annealed in a vacuum environment, the annealing temperature is 150° C., and the annealing time is 40 minutes.

Example 2

Referring to FIG. 1 and FIG. 3 , the GaN-on-diamond composite wafer prepared by the present invention has the structure of gallium nitride (1-3 microns)/metal buffer layer/gold film/metal buffer layer/diamond, and the specific preparation method includes the following steps :

1) Using benzocyclobutene (BCB) to bond the surface of the gallium nitride epitaxial layer of the silicon carbide substrate gallium nitride to the silicon carbide wafer (temporary carrier);

2) The silicon carbide substrate is thinned to 30 microns by mechanical grinding, and then the remaining silicon carbide substrate is etched by inductively coupled plasma etching, the nucleation layer is removed, and the gallium nitride epitaxial layer is thinned to 2 microns;

3) Surface polishing of the gallium nitride epitaxial layer and diamond, so that the roughness of the polished surface of gallium nitride and diamond is less than 2 nanometers;

4) ultrasonically clean gallium nitride and diamond with acetone, ethanol and deionized water successively;

5) Put gallium nitride and diamond into a sputtering coater, use the polished surface of gallium nitride and diamond as the surface to be bonded, and perform argon plasma treatment on the surface to be bonded, the plasma discharge power is 100W, and the treatment time for 2 minutes;

6) adopt the sputtering deposition method to successively deposit a 3-nanometer thick molybdenum buffer layer and a 15-nanometer thick gold film on the surfaces to be bonded of gallium nitride and diamond;

7) Take out gallium nitride and diamond from the sputtering coater, quickly place the to-be-bonded surface of gallium nitride and the to-be-bonded surface of the diamond substrate relative to each other within 1 minute and make them contact each other, using heavy objects The pressure method applies 0.5MPa pressure to the gallium nitride and diamond and keeps it for 2 minutes for the first bonding, that is, pre-bonding;

8) Put the pre-bonded gallium nitride and diamond into the bonding equipment, apply a pressure of 10 MPa to the gallium nitride and diamond and keep it for 3 minutes, carry out the second bonding, and bond the gallium nitride and the diamond substrate combine together;

9) Put the diamond substrate gallium nitride bonded on the temporary carrier into a container filled with acetone solution, and use ultrasonic vibration to accelerate the dissolution of the adhesive to remove the adhesive on the surface of the diamond substrate gallium nitride and a temporary slide to prepare a GaN-on-diamond composite wafer;

10) The gallium nitride-on-diamond composite wafer is annealed in a high-purity nitrogen environment, the annealing temperature is 180° C., and the annealing time is 20 minutes.

Example 3

Referring to FIG. 1 and FIG. 4 , the GaN-on-diamond composite wafer prepared by the present invention has the structure of gallium nitride (1-3 microns)/ceramic film layer/metal buffer layer/gold film/metal buffer layer/diamond. The method includes the following steps:

1) Use 502 glue to bond the surface of the gallium nitride epitaxial layer of the silicon carbide substrate gallium nitride to the quartz wafer (temporary carrier);

2) The silicon carbide substrate is thinned to 50 microns by mechanical grinding, and then the remaining silicon carbide substrate is etched by inductively coupled plasma etching, the nucleation layer is removed, and the gallium nitride epitaxial layer is thinned to 3 microns;

3) Surface polishing of the gallium nitride epitaxial layer and diamond, so that the roughness of the polished surface of gallium nitride and diamond is less than 2 nanometers;

4) ultrasonically clean gallium nitride and diamond with acetone, ethanol and deionized water successively;

5) Put gallium nitride and diamond into a sputtering coater, use the polished surface of gallium nitride and diamond as the surface to be bonded, and perform argon plasma treatment on the surface to be bonded, the plasma discharge power is 150W, and the treatment time is 1 minute;

6) Using the sputtering deposition method, successively deposit a 2-nanometer-thick aluminum nitride film, a 4-nanometer-thick aluminum buffer layer and a 50-nanometer-thick gold film on the surface to be bonded of gallium nitride, and successively deposit on the surface to be bonded of diamond 4nm thick aluminum buffer layer and 50nm thick gold film;

7) Take out the gallium nitride and diamond from the sputtering coater, quickly place the surface to be bonded of the gallium nitride and the surface to be bonded of the diamond substrate relative to each other and make them contact each other within 1 minute. Apply 1MPa pressure to gallium nitride and diamond and hold for 1 minute for the first bonding, that is, pre-bonding;

8) Put the pre-bonded gallium nitride and diamond into the bonding equipment, apply a pressure of 8 MPa to the gallium nitride and diamond and keep it for 4 minutes, carry out the second bonding, and bond the gallium nitride and the diamond substrate combine together;

9) Put the diamond substrate gallium nitride bonded on the temporary carrier into a container filled with acetone solution, and use ultrasonic vibration to accelerate the dissolution of the adhesive to remove the adhesive on the surface of the diamond substrate gallium nitride and a temporary slide to prepare a GaN-on-diamond composite wafer;

10) The gallium nitride-on-diamond composite wafer is annealed in a high-purity nitrogen environment, the annealing temperature is 120° C., and the annealing time is 60 minutes.

Example 4

Referring to FIG. 1 and FIG. 4 , the GaN-on-diamond composite wafer prepared by the present invention has the structure of gallium nitride (1-3 microns)/ceramic film layer/metal buffer layer/gold film/metal buffer layer/diamond. The method includes the following steps:

1) The surface of the gallium nitride epitaxial layer of the silicon carbide substrate gallium nitride and the diamond crystal (temporary carrier) sheet are bonded together with photoresist;

2) The silicon carbide substrate is thinned to 10 microns by mechanical grinding, and then the remaining silicon carbide substrate is etched by inductively coupled plasma etching, the nucleation layer is removed, and the gallium nitride epitaxial layer is thinned to 1.5 microns;

3) Surface polishing of gallium nitride and diamond, so that the roughness of the polished surface of gallium nitride and diamond is less than 2 nanometers;

4) ultrasonically clean gallium nitride and diamond with acetone, ethanol and deionized water successively;

5) Put gallium nitride and diamond into a sputtering coater, use the polished surface of gallium nitride and diamond as the surface to be bonded, and perform argon plasma treatment on the surface to be bonded, the plasma discharge power is 80W, and the treatment time for 3 minutes;

6) Using the sputtering deposition method, successively deposit a 3-nanometer-thick silicon carbide film, a 5-nanometer-thick tungsten buffer layer and an 8-nanometer-thick gold film on the surface to be bonded of gallium nitride, and successively deposit on the surface to be bonded of diamond 5nm thick tungsten buffer layer and 8nm thick gold film;

7) Take out the gallium nitride and diamond from the sputtering coater, quickly place the surface to be bonded of the gallium nitride and the surface to be bonded of the diamond substrate relative to each other within 1 minute and make them contact each other, using a heavy object The pressure method applies 1.5MPa pressure to the gallium nitride and diamond and keeps it for 1 minute for the first bonding, that is, pre-bonding;

8) Put the pre-bonded gallium nitride and diamond into the bonding equipment, apply a pressure of 3 MPa to the gallium nitride and diamond and keep it for 10 minutes, carry out the second bonding, and bond the gallium nitride and the diamond substrate combine together;

9) Put the diamond substrate gallium nitride bonded on the temporary carrier into a container filled with acetone solution, and use ultrasonic vibration to accelerate the dissolution of the adhesive to remove the adhesive on the surface of the diamond substrate gallium nitride and a temporary slide to prepare a GaN-on-diamond composite wafer;

10) Perform annealing treatment on the GaN-on-diamond composite wafer in a vacuum environment, the annealing temperature is 200° C., and the annealing time is 10 minutes.

Referring to Fig. 5, Fig. 6, Fig. 7 and Fig. 8, it can be seen that both the polished diamond substrate and the gallium nitride layer have very low surface roughness, 0.509 nm and 0.265 nm, respectively, even at their After depositing a molybdenum buffer layer and a gold thin film on the bonding surface, the surface roughness is still very low, 0.685 nm and 0.438 nm, respectively, which is conducive to the realization of high-quality bonding of gallium nitride and diamond.

Figures 9 and 10 are the structures with gallium nitride/nucleation layer/silicon carbide (5-80 microns)/metal buffer layer/gold film/metal buffer layer/diamond structure and gallium nitride (1- 3 μm)/metal buffer layer/gold film/metal buffer layer/diamond structure of the GaN-on-diamond composite wafer morphology, both samples achieved a bonding strength of more than 10MPa.

Fig. 11 is an ultrasonic scanning microscope photograph of a GaN-on-diamond composite wafer prepared by bonding method. It can be clearly seen that there is no void in the bonding interface between GaN and diamond.

The invention realizes a diamond-based gallium nitride composite wafer structure based on a metal nano-intermediate layer, adopts a two-step bonding method of gallium nitride and diamond bonding, can reduce the bonding void rate, increase the bonding strength, and reduce the The thermal resistance between gallium nitride and diamond can improve the bonding quality of gallium nitride and diamond, and can prepare high-performance GaN-on-diamond devices.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the technical solutions of the present invention. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solutions also Several simple modifications and substitutions can be made, and these modifications and substitutions will also fall within the protection scope covered by the claims.

Claims (10)

1. a diamond-based gallium nitride composite wafer, is characterized in that, has any one structure in following a), b) and c): a) a multilayer structure formed by gallium nitride, nucleation layer, silicon carbide, metal intermediate layer, and diamond substrate in sequence; b) a multilayer structure formed by gallium nitride, a metal intermediate layer, and a diamond substrate in sequence; c) a multi-layer structure formed by gallium nitride, a ceramic film layer, a metal intermediate layer, and a diamond substrate in sequence, and the material of the ceramic film layer is aluminum nitride or silicon carbide; The metal intermediate layer has a three-layer structure of a metal buffer layer, a gold film layer and a metal buffer layer arranged in sequence; the material of the metal buffer layer is tungsten, molybdenum or aluminum. 2. The diamond-based gallium nitride composite wafer according to claim 1, wherein the thickness of the diamond substrate in the structures a), b) and c) is 100-2000 microns; The thickness is 1-20 nanometers; the thickness of the gold film layer is 5-200 nanometers; the thickness of the silicon carbide layer in the structure a) is 5-80 micrometers; the layer thickness of the gallium nitride in the structure b) is 1-3 micrometers; the thickness of the gallium nitride layer in the structure c) is 1-3 micrometers, and the thickness of the ceramic film layer is 1-15 nanometers. 3. a bonding preparation method of diamond-based gallium nitride composite wafer, is characterized in that, comprises the following steps: 1) bonding the surface of the gallium nitride epitaxial layer on the silicon carbide substrate gallium nitride with the temporary carrier with an adhesive; 2) thinning the silicon carbide substrate; or completely peeling off the silicon carbide substrate, removing the nucleation layer, and thinning the gallium nitride epitaxial layer; 3) Polish the surface of the thinned silicon carbide substrate or the surface of the thinned gallium nitride epitaxial layer, and polish the diamond surface, so that the silicon carbide substrate or the gallium nitride epitaxial layer and the diamond polished surface are polished. The roughness is lower than the required value; 4) ultrasonically clean gallium nitride and diamond with acetone, ethanol and deionized water successively; 5) The polishing surface of the silicon carbide substrate or the gallium nitride epitaxial layer is the surface to be bonded of gallium nitride, the polished surface of diamond is the surface to be bonded of diamond, and the surface to be bonded of gallium nitride and diamond is Argon plasma treatment; 6) successively deposit a metal buffer layer and a gold film layer on the surface to be bonded of gallium nitride of the thinned silicon carbide substrate, or successively deposit metal on the surface to be bonded of gallium nitride of the thinned epitaxial layer of gallium nitride Buffer layer and gold film layer or successively deposit ceramic film layer, metal buffer layer and gold film layer; successively deposit metal buffer layer and gold film layer on the surface to be bonded of diamond; 7) Place the surface to be bonded of gallium nitride and the surface to be bonded of diamond relative to each other and make them contact each other, and apply pressure to carry out the first bonding of gallium nitride and diamond, that is, pre-bonding; 8) applying pressure to bond the pre-bonded gallium nitride and diamond for the second time; 9) removing the adhesive and the temporary carrier on the gallium nitride surface of the diamond substrate to prepare a gallium nitride-on-diamond composite wafer; 10) annealing the GaN-on-diamond composite wafer to complete the preparation. 4. The bonding preparation method of the GaN-on-Diamond composite wafer according to claim 3, characterized in that: the adhesive described in step 1) is photoresist, benzocyclobutene or 502 glue; The material of the temporary carrier is silicon, aluminum oxide, silicon carbide, quartz or diamond, and the surface roughness of the temporary carrier is not higher than 10 nanometers. 5. the bonding preparation method of the gallium nitride-on-diamond composite wafer according to claim 3, is characterized in that: step 2) adopts the method of mechanical grinding to thin the silicon carbide substrate to 5-80 microns; or continue to use induction Coupled plasma etching is used to etch the remaining silicon carbide substrate, remove the nucleation layer, and thin the gallium nitride epitaxial layer to 1-3 microns; Step 3) The required value of the roughness is 2 nanometers; Step 6) The thickness of the metal buffer layer deposited on the surfaces to be bonded of gallium nitride and diamond is 1-20 nanometers, respectively, and the thickness of the gold film layer deposited on the surfaces to be bonded of gallium nitride and diamond is 2.5-100 nanometers, respectively , the thickness of the ceramic film layer deposited on the surface to be bonded of the gallium nitride is 1-15 nanometers. 6. The bonding preparation method of the gallium nitride-on-diamond composite wafer according to claim 3, wherein the argon plasma used in the argon plasma treatment described in step 5) is generated by gas discharge, and the discharge power is 30 -200W, Argon plasma treatment time is 0.5-20 minutes. 7. The bonding preparation method of the gallium nitride-on-diamond composite wafer according to claim 3, characterized in that: in step 7) after each film layer is deposited on the surfaces to be bonded of gallium nitride and diamond, without exposing the atmosphere Under the condition of mechanical pressure, the first bonding of gallium nitride and diamond is carried out, or the gallium nitride and diamond are taken out from the coating cavity, and manual pressure or heavy objects are used at room temperature and atmospheric environment. The first bonding of gallium nitride and diamond is carried out quickly by pressing method, the applied pressure is 0.2-2MPa, and the pressing time is 1-3 minutes. 8. the bonding preparation method of diamond-based gallium nitride composite wafer according to claim 3, is characterized in that: when step 8) carries out the second bonding to gallium nitride and diamond, the temperature of gallium nitride and diamond is low At 150°C, the applied pressure is 0.5-10 MPa, and the pressing time is 1-20 minutes. 9. the bonding preparation method of diamond-based gallium nitride composite wafer according to claim 3, is characterized in that, the mode of step 9) removing adhesive and temporary carrier is: put into acetone solution, adopt ultrasonic vibration to accelerate Dissolution of the adhesive. 10. The bonding preparation method of the GaN-on-diamond composite wafer according to claim 3, wherein the annealing treatment in step 10) is carried out in a vacuum environment or in a nitrogen atmosphere, and the annealing temperature is 100-200 °C ℃, the annealing time is 10-60 minutes.

Images