A Rapid Thermal Annealing (RTA) Process for Silicon Carbide Wafers

Abstract

The present invention relates to the technical field of silicon carbide wafers, and specifically to a rapid thermal annealing (RTA) rapid alloying process for silicon carbide wafers. The present invention includes the following steps: S1. Bond a glass carrier plate to the back surface of the silicon carbide wafer, then fabricate transistors and an interlayer dielectric (ILD) layer on the front surface of the silicon carbide wafer, then bond a glass carrier plate to the front surface of the silicon carbide wafer, then flip the wafer and the glass carrier plate, and then debond the glass carrier plate on the back surface of the silicon carbide wafer and remove the adhesive; by directly depositing a silver metal layer on the surface of the titanium metal layer after the sputtering of the nickel metal layer and the titanium metal layer is completed before the RTA rapid alloying process of the silicon carbide wafer, the silver metal layer can undergo the RTA rapid alloying process together with the silicon carbide wafer, without having to flip the silicon carbide wafer multiple times after the RTA rapid alloying process to cooperate with the glass carrier plate for silver metal layer deposition, simplifying the steps of the RTA rapid alloying, effectively reducing the processing cost, and improving the processing speed.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide wafers, and specifically to a rapid thermal annealing (RTA) alloying process for silicon carbide wafers. Background Art

[0002] A silicon carbide wafer, also known as a silicon carbide single crystal wafer, is a sheet-like single crystal material obtained by cutting, grinding, and polishing a silicon carbide crystal along a specific crystal direction.

[0003] For the processing of silicon carbide wafers, an RTA alloying process is required to make the contact resistance value between the silicon carbide wafer and the metal smaller, which is beneficial to the input and output of current. To avoid local heating caused by the melting of aluminum during the RTA rapid alloying process, and since the alloying process effect of local heat treatment is not good and the formed ohmic contact effect is not good, the prior art will deposit the aluminum metal layer after the RTA alloying process.

[0004] In the process of depositing the aluminum metal layer after the RTA rapid alloying process, since the process of making the silver metal layer is also after the RTA rapid alloying step, it is necessary to bond and debond the glass carrier plate multiple times to flip the silicon carbide wafer, and its process steps are complex, the processing cost is high, and it is not convenient to quickly complete the processing of the silicon carbide wafer. Summary of the Invention

[0005] The purpose of the present invention is to provide a rapid thermal annealing (RTA) alloying process for silicon carbide wafers to solve the problems raised in the above background art.

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

[0007] A rapid thermal annealing (RTA) alloying process for silicon carbide wafers includes the following steps:

[0008] S1. Bond a glass carrier plate to the back of the silicon carbide wafer, then fabricate transistors and an interlayer dielectric (ILD) layer on the front of the silicon carbide wafer, then bond a glass carrier plate to the front of the silicon carbide wafer, then flip the wafer and the glass carrier plate, and then debond the glass carrier plate 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 of the silicon carbide wafer by sputtering, then deposit a nickel metal layer on the surface of the titanium metal layer by sputtering, and finally deposit a silver metal layer on the surface of the nickel metal layer by sputtering;

[0010] S3. For the silicon carbide wafer obtained in step S2, take a glass carrier disk, then flip the silicon carbide wafer, and attach the silver metal layer on the back of the silicon carbide wafer to the glass carrier disk;

[0011] S4. For the silicon carbide wafer obtained in step S3, perform an RTA rapid alloying process on the metal layer on the back of the silicon carbide wafer to form an ohmic contact on the back of the silicon carbide wafer, and finally deposit a layer of aluminum metal on the surface of the silicon carbide wafer that has undergone the RTA rapid alloying process;

[0012] S5. For the silicon carbide wafer obtained in step S4, fabricate aluminum contact points on the aluminum metal layer deposited on the surface of the silicon carbide wafer, then coat polyimide on the front of the silicon carbide wafer, and finally perform a chemical plating process to fabricate metal connection points on the surface of the aluminum contact points on the front of the silicon carbide wafer.

[0013] Preferably, in step S1, when bonding the glass carrier plate, bond the glass carrier plate to the front of the silicon carbide wafer using a UV adhesive. When debonding the glass carrier plate, perform UV light irradiation to make the UV adhesive lose its viscosity and complete the debonding of the glass carrier plate.

[0014] Preferably, in step S1, after completing the debonding of the glass carrier plate, remove the glass carrier plate and clean the silicon carbide wafer with an organic solvent to remove the adhesive on the front of the silicon carbide wafer.

[0015] Preferably, in step S4, the aluminum metal layer deposited on the surface of the silicon carbide wafer that has undergone the RTA rapid alloying process is located on the front of the silicon carbide wafer.

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

[0017] Preferably, in step S2, the melting point of the deposited silver metal layer is 961.93°C to ensure that the state of the silver metal layer does not change when the silicon carbide wafer undergoes the RTA rapid alloying process.

[0018] Preferably, in step S5, when fabricating the aluminum contact points, the process steps are sequentially coating photoresist on the surface of the aluminum metal layer, exposure and development, etching, and finally removing the photoresist to obtain the aluminum contact points.

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

[0020] Preferably, in step S4, when depositing aluminum metal, use a sputtering process for deposition, and control the temperature during the deposition of aluminum metal above 400°C.

[0021] Advantages of the present invention:

[0022] Before the RTA rapid alloy process on the silicon carbide wafer, after the sputtering of the nickel metal layer and the titanium metal layer is completed, a silver metal layer is directly deposited on the surface of the titanium metal layer, so that the silver metal layer can undergo the RTA rapid alloy process together with the silicon carbide wafer, without the need to flip the silicon carbide wafer multiple times after the RTA rapid alloy process to cooperate with the glass carrier for the deposition of the silver metal layer, simplifying the steps of the RTA rapid alloy, effectively reducing the processing cost, and improving the processing speed. Brief Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings;

[0024] Figure 1 It is a flowchart of step S1 of the present invention;

[0025] Figure 2 It is a flowchart of step S2 of the present invention;

[0026] Figure 3 It is a flowchart of step S3 of the present invention;

[0027] Figure 4 It is a flowchart of step S4 of the present invention;

[0028] Figure 5 It is a flowchart of step S5 of the present invention;

[0029] Figure 6 is Figure 5 a schematic structural diagram of the metal connection point part. Detailed Embodiments

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0031] A silicon carbide wafer RTA rapid alloy process includes the following steps:

[0032] S1. Bond a glass carrier on the back of the silicon carbide wafer, then fabricate transistors and an ILD layer on the front of the silicon carbide wafer, then bond a glass carrier on the front of the silicon carbide wafer, then flip the wafer and the glass carrier, and then debond the glass carrier on the back of the silicon carbide wafer and remove the adhesive;

[0033] S2. For the silicon carbide wafer obtained in step S1, first deposit a titanium metal layer on the back surface of the silicon carbide wafer by sputtering, then deposit a nickel metal layer on the surface of the titanium metal layer by sputtering, and finally deposit a silver metal layer on the surface of the nickel metal layer by sputtering;

[0034] S3. For the silicon carbide wafer obtained in step S2, take a glass carrier plate, then flip the silicon carbide wafer, and attach the silver metal layer on the back surface of the silicon carbide wafer to the glass carrier plate;

[0035] S4. For the silicon carbide wafer obtained in step S3, perform 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 deposit an aluminum metal layer on the surface of the silicon carbide wafer that has undergone the RTA rapid alloying process;

[0036] S5. For the silicon carbide wafer obtained in step S4, fabricate the aluminum metal layer deposited on the surface of the silicon carbide wafer into aluminum contact points, then coat polyimide on the front surface of the silicon carbide wafer, and finally perform an electroless plating process to fabricate metal connection points on the surface of the aluminum contact points on the front surface of the silicon carbide wafer.

[0037] In step S1, when bonding the glass carrier plate, bond the glass carrier plate to the front surface of the silicon carbide wafer with UV glue as an adhesive. When debonding the glass carrier plate, perform UV illumination to make the UV glue lose its viscosity and complete the debonding of the glass carrier plate.

[0038] In step S1, after completing the debonding of the glass carrier plate, remove the glass carrier plate, and clean the silicon carbide wafer with an organic solvent to remove the adhesive on the front surface of the silicon carbide wafer.

[0039] By bonding the glass carrier plate and the silicon carbide wafer with UV glue, it is convenient to debond the glass carrier plate.

[0040] In step S4, the aluminum metal layer deposited on the surface of the silicon carbide wafer that has undergone the RTA rapid alloying process is located on the front surface of the silicon carbide wafer.

[0041] In step S3, when performing the RTA rapid alloying process on the silicon carbide wafer, perform constant-temperature heating on the silicon carbide wafer, control the heating temperature range at 600°C - 800°C, control the constant-temperature heating time range at 10s - 30s, and perform rapid automatic cooling after heating.

[0042] When performing rapid automatic cooling, it can be achieved by contacting with a refrigerant to rapidly cool the silicon carbide wafer after heating.

[0043] In the step S2, the melting point of the deposited silver metal layer is 961.93 °C to ensure that the state of the silver metal layer does not change when the silicon carbide wafer undergoes the RTA rapid alloying process.

[0044] In the step S5, when fabricating the aluminum contact points, the process steps are successively coating photoresist on the surface of the aluminum metal layer, exposure and development, etching, and finally removing the photoresist to obtain the aluminum contact points.

[0045] In the step S5, the fabricated metal connection points are successively a nickel layer, a palladium layer, and a gold layer from bottom to top, and the nickel layer is located on the surface of the aluminum contact points.

[0046] The nickel layer is located on the surface of the aluminum contact points, the palladium layer is located on the surface of the nickel layer, and the gold layer is located on the surface of the palladium layer.

[0047] In the step S4, when depositing metallic aluminum, the sputtering process is used for deposition, and the temperature during the deposition of metallic aluminum is controlled above 400 °C.

[0048] Compared with the related technology, a silicon carbide wafer RTA rapid alloying process provided by the present invention has the following beneficial effects:

[0049] By directly depositing a silver metal layer on the surface of the titanium metal layer after the sputtering of the nickel metal layer and the titanium metal layer is completed before the silicon carbide wafer undergoes the RTA rapid alloying process, the silver metal layer can undergo the RTA rapid alloying process together with the silicon carbide wafer, without repeatedly flipping the silicon carbide wafer to cooperate with the glass carrier for silver metal layer deposition after the RTA rapid alloying process is completed, simplifying the steps of the RTA rapid alloying, effectively reducing the processing cost, and improving the processing speed.

[0050] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A rapid thermal annealing (RTA) process for silicon carbide wafers, characterized in that, Including the following steps: S1. Bond a glass carrier on the back side of the silicon carbide wafer, then fabricate transistors and the ILD layer on the front side of the silicon carbide wafer, then bond a glass carrier on the front side of the silicon carbide wafer, then flip the wafer and the glass carrier, and then debond the glass carrier on the back side 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 by sputtering, then deposit a nickel metal layer on the surface of the titanium metal layer by sputtering, and finally deposit a silver metal layer on the surface of the nickel metal layer by sputtering; S3. For the silicon carbide wafer obtained in step S2, take a glass carrier plate, then flip the silicon carbide wafer, and attach the silver metal layer on the back side of the silicon carbide wafer to the glass carrier plate; S4. For the silicon carbide wafer obtained in step S3, 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 an aluminum metal layer on the surface of the silicon carbide wafer that has undergone the RTA rapid alloying process; S5. For the silicon carbide wafer obtained in step S4, fabricate aluminum contact points from the aluminum metal layer deposited on the surface of the silicon carbide wafer, then coat polyimide on the front side of the silicon carbide wafer, and finally perform a chemical plating process to fabricate metal connection points on the surface of the aluminum contact points on the front side of the silicon carbide wafer.

2. The rapid thermal alloying process for silicon carbide wafers according to claim 1, characterized in that In step S1, when bonding the glass carrier, the glass carrier is bonded to the front side of the silicon carbide wafer with a UV adhesive as the adhesive. When debonding the glass carrier, UV light is irradiated to make the UV adhesive lose its viscosity, and the debonding of the glass carrier is completed.

3. The rapid thermal alloying process of silicon carbide wafers according to claim 2, characterized in that, In step S1, after completing the debonding of the glass carrier, the glass carrier is removed, and the silicon carbide wafer is cleaned with an organic solvent to remove the adhesive on the front side of the silicon carbide wafer.

4. A rapid thermal annealing alloying process for silicon carbide wafers according to claim 3, characterized in that, In step S4, the aluminum metal layer deposited on the surface of the silicon carbide wafer that has undergone the RTA rapid alloying process is located on the front side of the silicon carbide wafer.

5. A rapid thermal annealing 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 range is controlled at 600°C - 800°C, the constant temperature heating time range is controlled at 10s - 30s, and rapid automatic cooling is performed after heating.

6. A rapid thermal annealing (RTA) alloying process for silicon carbide wafers according to claim 5, characterized in that, In step S2, the melting point of the deposited silver metal layer is 961.93°C to ensure that the state of the silver metal layer does not change when the silicon carbide wafer undergoes the RTA rapid alloying process.

7. A rapid thermal annealing (RTA) alloying process for silicon carbide wafers according to claim 5, characterized in that, In step S5, when fabricating the aluminum contact points, the process steps are successively coating photoresist on the surface of the aluminum metal layer, exposure and development, etching, and finally removing the photoresist to obtain the aluminum contact points.

8. A rapid thermal annealing (RTA) alloying process for silicon carbide wafers according to claim 7, characterized in that, In step S5, the fabricated metal connection points are, from bottom to top, a nickel layer, a palladium layer, and a gold layer, and the nickel layer is located on the surface of the aluminum contact points.

9. A rapid thermal annealing (RTA) process for silicon carbide wafers according to claim 1, characterized in that, In step S4, when depositing aluminum metal, sputtering is used for deposition, and the temperature during the deposition of aluminum metal is controlled above 400°C.

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