A silicon carbide wafer RTA rapid alloying process

Abstract

The present application relates to the technical field of silicon carbide wafer processing, in particular to a silicon carbide wafer RTA rapid alloying process, which comprises the following steps: S1, bonding a glass carrier plate on the back surface of the silicon carbide wafer, then making a transistor and an ILD layer on the front surface of the silicon carbide wafer, then bonding a glass carrier plate on the front surface of the silicon carbide wafer, then turning over the wafer and the glass carrier plate, then debonding the glass carrier plate on the back surface of the silicon carbide wafer and removing the adhesive; through the process of the present application, the titanium metal layer and the nickel metal layer can be first made on the silicon carbide wafer, which is carried by the glass carrier plate, thereby assisting the processing and transfer of the silicon carbide wafer; when the RTA process is performed, the whole wafer can be heated in a high-temperature environment, so that the RTA alloying process effect is better, the ohmic contact effect is better, and finally the aluminum metal layer is deposited to complete the RTA rapid alloying of the silicon carbide wafer, thereby avoiding the melting of the aluminum metal layer caused by the high temperature of the RTA process.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide wafer processing, in particular to a silicon carbide wafer RTA rapid alloying process. Background Art

[0002] Silicon carbide wafers, also known as silicon carbide single crystal sheets, are sheet-shaped single crystal materials obtained by cutting, grinding, and polishing silicon carbide crystals along a specific crystal direction.

[0003] For the processing of silicon carbide wafers, ohmic contact can be formed on the silicon carbide wafer through the RTA alloy process, so that the internal structure of the metal reaches or is close to a balanced state, obtaining good process performance and usage performance, and making the contact surface resistance between the silicon carbide wafer and the metal smaller, which is conducive to current and input and output.

[0004] The existing technology for the RTA alloying process of silicon carbide wafers is as follows: after completing the front-side process, an aluminum metal layer is deposited on the front of the silicon carbide wafer, and then the wafer is flipped over for the back-side process, and then the titanium and nickel metal layers are processed at high temperature. Since the aluminum metal layer will melt in a high-temperature environment exceeding 660°C, the existing technology uses a laser to perform local heat treatment on the back of the silicon carbide wafer. However, the alloying process made by local heat treatment is not effective, and the ohmic contact effect formed is not good. Summary of the Invention

[0005] The object of the present invention is to provide a silicon carbide wafer RTA rapid alloying process to solve the problems raised in the above background technology.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A silicon carbide wafer RTA rapid alloying process comprises the following steps:

[0008] S1. Bond a glass carrier to the back of the silicon carbide wafer, then fabricate transistors and ILD layers on the front of the silicon carbide wafer, then bond a glass carrier to the front of the silicon carbide wafer, flip the wafer and glass carrier, debond the glass carrier on the back of the silicon carbide wafer, and remove the adhesive;

[0009] S2. For the silicon carbide wafer obtained in step S1, first deposit a titanium metal layer on the back side of the silicon carbide wafer, then deposit a nickel metal layer on the surface of the titanium metal layer, then take a glass carrier with a small hole at the bottom, flip the silicon carbide wafer, and bond the back side of the silicon carbide wafer to the glass carrier with the small hole at the bottom, and finally debond the glass carrier on the front side of the silicon carbide wafer;

[0010] S3. For the silicon carbide wafer obtained in step S2, flip the silicon carbide wafer, attach the front side of the silicon carbide wafer to a glass carrier, remove the glass carrier on the back side, perform an RTA rapid alloying process on the metal layer on the back side of the silicon carbide wafer to form an ohmic contact on the back side of the silicon carbide wafer, and finally deposit a silver metal layer on the back side of the silicon carbide wafer;

[0011] S4. For the silicon carbide wafer obtained in step S3, flip the wafer, attach the back side of the silicon carbide wafer to the glass carrier, remove the glass carrier on the front side of the silicon carbide wafer, and finally deposit an aluminum metal layer on the front side of the silicon carbide wafer;

[0012] S5. For the silicon carbide wafer obtained in step S4, the aluminum metal layer deposited on the front side of the silicon carbide wafer is made into aluminum contact points, and then polyimide is coated on the front side of the silicon carbide wafer. Finally, a chemical plating process is performed to make metal connection points on the surface of the aluminum contact points on the front side of the silicon carbide wafer.

[0013] Preferably, in step S1, after debonding the glass carrier on the back side of the silicon carbide wafer and removing the adhesive, the back side of the silicon carbide wafer is ground and polished.

[0014] Preferably, in steps S2 and S3, the deposition of the titanium metal layer, the nickel metal layer and the silver metal layer are all performed by a sputtering process.

[0015] Preferably, in step S2, air is extracted from under the glass carrier with air holes by an exhaust device to vacuum adsorb the silicon carbide wafer. In step S3, when removing the glass carrier on the back, the exhaust of the exhaust device is stopped first, and the glass carrier can be removed at this time.

[0016] Preferably, in step S3, when performing the RTA rapid alloying process on the silicon carbide wafer, the silicon carbide wafer is heated at a constant temperature, the heating temperature is controlled in the range of 600°C-800°C, the constant temperature heating time is controlled in the range of 10s-30s, and rapid automatic cooling is performed after heating.

[0017] Preferably, in step S4, when depositing the metal aluminum, a sputtering process is used for deposition, and the temperature during the deposition of the metal aluminum needs to be greater than 400°C.

[0018] Preferably, in step S5, when the aluminum contact point is produced, the process steps are sequentially coating the surface of the aluminum metal layer with photoresist, exposing and developing, etching, and finally removing the photoresist to obtain the aluminum contact point.

[0019] Preferably, in step S5, the metal connection points are sequentially formed from bottom to top by a nickel layer, a palladium layer and a gold layer, and the nickel layer is located on the surface of the aluminum contact point.

[0020] Preferably, in steps S1-S5, adhesive is used to bond the glass carrier or glass carrier when bonding the glass carrier or glass carrier, and solvent is used to remove the adhesive each time the glass carrier or glass carrier is debonded.

[0021] Beneficial effects of the present invention:

[0022] Through the process of the present invention, a titanium metal layer and a nickel metal layer can be first produced on a silicon carbide wafer, which is carried by a glass carrier, and can assist in the processing and transfer of the silicon carbide wafer, so that when the RTA process is carried out, the entire wafer can be placed in a high-temperature environment and heated as a whole, so that the RTA alloying process effect is better and the ohmic contact effect is better. Finally, an aluminum metal layer is deposited to complete the RTA rapid alloying of the silicon carbide wafer, thereby avoiding the melting of the aluminum metal layer due to the high temperature of the RTA process. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0024] Figure 1 It is a schematic flow chart of step S1 of the present invention;

[0025] Figure 2 It is a schematic flow chart of step S2 of the present invention;

[0026] Figure 3 It is a schematic flow chart of step S3 of the present invention;

[0027] Figure 4 It is a schematic flow chart of step S4 of the present invention;

[0028] Figure 5 It is a schematic flow chart of step S5 of the present invention;

[0029] Figure 6 yes Figure 5 Schematic diagram of the structure of the metal connection point part. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0031] A silicon carbide wafer RTA rapid alloying process, comprising the following steps:

[0032] S1, bonding a glass carrier plate on the back surface of a silicon carbide wafer, then making a transistor and an ILD layer on the front surface of the silicon carbide wafer, then bonding a glass carrier plate on the front surface of the silicon carbide wafer, then turning over the wafer and the glass carrier plate, then debonding the glass carrier plate on the back surface of the silicon carbide wafer and removing the adhesive;

[0033] S2, for the silicon carbide wafer obtained in step S1, first depositing a layer of titanium metal on the back surface of the silicon carbide wafer, then depositing a layer of nickel metal on the surface of the titanium metal layer, then taking a glass carrier plate with a small hole at the bottom, turning over the silicon carbide wafer, and bonding the back surface of the silicon carbide wafer to the glass carrier plate with a small hole at the bottom, and finally debonding the glass carrier plate on the front surface of the silicon carbide wafer;

[0034] S3, for the silicon carbide wafer obtained in step S2, turning over the silicon carbide wafer, bonding the front surface of the silicon carbide wafer to the glass carrier plate, removing the glass carrier plate on the back surface, and then performing an RTA rapid alloying process on the metal layer on the back surface of the silicon carbide wafer to form an ohmic contact on the back surface of the silicon carbide wafer, and finally depositing a layer of silver metal on the back surface of the silicon carbide wafer;

[0035] S4, for the silicon carbide wafer obtained in step S3, turning over the wafer, bonding the back surface of the silicon carbide wafer to the glass carrier plate, removing the glass carrier plate on the front surface of the silicon carbide wafer, and finally depositing an aluminum metal layer on the front surface of the silicon carbide wafer;

[0036] S5, for the silicon carbide wafer obtained in step S4, making the aluminum metal layer deposited on the front surface of the silicon carbide wafer into an aluminum contact point, then coating polyimide on the front surface of the silicon carbide wafer, and finally performing a chemical plating process to make a metal connection point on the surface of the aluminum contact point on the front surface of the silicon carbide wafer.

[0037] The silicon carbide wafer used in step S1 is a sliced silicon carbide wafer, and the transistor and ILD layer are made by existing technology, which will not be described in detail here.

[0038] In the step S1, after the debonding and removal of the adhesive of the glass carrier plate on the back surface of the silicon carbide wafer, the back surface of the silicon carbide wafer is polished.

[0039] Through the polishing of the back surface of the silicon carbide wafer, the smoothness of the back surface of the silicon carbide wafer can be improved, which is convenient for subsequent processing.

[0040] In steps S2 and S3, the deposition of the titanium metal layer, the nickel metal layer and the silver metal layer is carried out by sputtering process.

[0041] In step S2, air is extracted from under the glass carrier with air holes by an exhaust device to vacuum adsorb the silicon carbide wafer. In step S3, when removing the glass carrier on the back, the exhaust of the exhaust device is stopped first, and the glass carrier can be removed at this time.

[0042] By using vacuum equipment to vacuum-adsorb the silicon carbide wafer onto the glass carrier, there is no need to use adhesives for bonding, which reduces processing costs.

[0043] In step S3, when performing the RTA rapid alloying process on the silicon carbide wafer, the silicon carbide wafer is heated at a constant temperature, the heating temperature is controlled in the range of 600°C-800°C, the constant temperature heating time is controlled in the range of 10s-30s, and rapid automatic cooling is performed after heating.

[0044] In step S4, when depositing the metal aluminum, a sputtering process is used for deposition, and the temperature during the deposition of the metal aluminum needs to be greater than 400°C.

[0045] In step S5, when the aluminum contact point is produced, the process steps are sequentially coating the surface of the aluminum metal layer with photoresist, exposing and developing, etching, and finally removing the photoresist to obtain the aluminum contact point.

[0046] In step S5, the metal connection points are sequentially formed from bottom to top by a nickel layer, a palladium layer and a gold layer, and the nickel layer is located on the surface of the aluminum contact point.

[0047] In the steps S1 to S5 , adhesive is used to bond the glass carrier or glass carrier when bonding the glass carrier or glass carrier. After debonding the glass carrier or glass carrier each time, solvent is used to remove the adhesive.

[0048] The adhesive may be UV glue. After debonding and UV irradiation, the adhesive loses its stickiness. The bonded glass carrier can be removed from the silicon carbide wafer, and then the adhesive can be removed with a solvent to facilitate processing of the silicon carbide wafer.

[0049] Compared with related technologies, the RTA rapid alloying process for silicon carbide wafers provided by the present invention has the following beneficial effects:

[0050] Through the process of the present invention, a titanium metal layer and a nickel metal layer can be first produced on a silicon carbide wafer, which is carried by a glass carrier, and can assist in the processing and transfer of the silicon carbide wafer, so that when the RTA process is carried out, the entire wafer can be placed in a high-temperature environment and heated as a whole, so that the RTA alloying process effect is better and the ohmic contact effect is better. Finally, an aluminum metal layer is deposited to complete the RTA rapid alloying of the silicon carbide wafer, thereby avoiding the melting of the aluminum metal layer due to the high temperature of the RTA process.

[0051] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A silicon carbide wafer RTA rapid alloying process, characterized in that: The following steps are involved: S1. Bond a glass carrier to the back of the silicon carbide wafer, then fabricate transistors and ILD layers on the front of the silicon carbide wafer, then bond a glass carrier to the front of the silicon carbide wafer, flip the wafer and glass carrier, debond the glass carrier on the back of the silicon carbide wafer, and remove the adhesive; S2. For the silicon carbide wafer obtained in step S1, first deposit a titanium metal layer on the back side of the silicon carbide wafer, then deposit a nickel metal layer on the surface of the titanium metal layer, then take a glass carrier with a small hole at the bottom, flip the silicon carbide wafer, and bond the back side of the silicon carbide wafer to the glass carrier with the small hole at the bottom, and finally debond the glass carrier on the front side of the silicon carbide wafer; S3. For the silicon carbide wafer obtained in step S2, flip the silicon carbide wafer, attach the front side of the silicon carbide wafer to a glass carrier, remove the glass carrier on the back side, perform an RTA rapid alloying process on the metal layer on the back side of the silicon carbide wafer to form an ohmic contact on the back side of the silicon carbide wafer, and finally deposit a silver metal layer on the back side of the silicon carbide wafer; S4. For the silicon carbide wafer obtained in step S3, flip the wafer, attach the back side of the silicon carbide wafer to the glass carrier, remove the glass carrier on the front side of the silicon carbide wafer, and finally deposit an aluminum metal layer on the front side of the silicon carbide wafer; S5. For the silicon carbide wafer obtained in step S4, the aluminum metal layer deposited on the front side of the silicon carbide wafer is made into aluminum contact points, and then polyimide is coated on the front side of the silicon carbide wafer. Finally, a chemical plating process is performed to make metal connection points on the surface of the aluminum contact points on the front side of the silicon carbide wafer.

2. The RTA rapid alloying process for silicon carbide wafers according to claim 1, characterized in that: In step S1 , after debonding the glass carrier on the back side of the silicon carbide wafer and removing the adhesive, the back side of the silicon carbide wafer is ground and polished.

3. The RTA rapid alloying process for silicon carbide wafers according to claim 1, characterized in that: In steps S2 and S3 , the deposition of the titanium metal layer, the nickel metal layer, and the silver metal layer are all performed by a sputtering process.

4. The RTA rapid alloying process for silicon carbide wafers according to claim 1, characterized in that: In step S2, air is extracted from under the glass carrier with air holes by an exhaust device to vacuum adsorb the silicon carbide wafer. In step S3, when removing the glass carrier on the back, the exhaust of the exhaust device is stopped first, and the glass carrier can be removed at this time.

5. The RTA rapid alloying process for silicon carbide wafers according to claim 1, characterized in that: In step S3, when performing the RTA rapid alloying process on the silicon carbide wafer, the silicon carbide wafer is heated at a constant temperature, the heating temperature is controlled in the range of 600°C-800°C, the constant temperature heating time is controlled in the range of 10s-30s, and rapid automatic cooling is performed after heating.

6. The RTA rapid alloying process for silicon carbide wafers according to claim 5, characterized in that: In step S4, when depositing the metal aluminum, a sputtering process is used for deposition, and the temperature during the deposition of the metal aluminum needs to be greater than 400°C.

7. The RTA rapid alloying process for silicon carbide wafers according to claim 6, characterized in that: In step S5, when the aluminum contact point is produced, the process steps are sequentially coating the surface of the aluminum metal layer with photoresist, exposing and developing, etching, and finally removing the photoresist to obtain the aluminum contact point.

8. The RTA rapid alloying process for silicon carbide wafers according to claim 7, characterized in that: In step S5, the metal connection points are sequentially formed from bottom to top by a nickel layer, a palladium layer and a gold layer, and the nickel layer is located on the surface of the aluminum contact point.

9. The RTA rapid alloying process for silicon carbide wafers according to claim 1, characterized in that: When bonding the glass carrier, an adhesive is used to bond the glass carrier. After debonding the glass carrier, a solvent is used to remove the adhesive.

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