A silicon carbide wafer backside processing technology
By depositing a double-layer silicon oxide structure on the back of the silicon carbide wafer and on the glass carrier plate, combining the air extraction equipment and subsequent processing steps, the problems of poor heat resistance and poor fixation effect of the glass carrier plate are solved, and silicon carbide crystal is realized The stable fixation of the circle during high temperature process and grinding and thinning process.
Patent Information
- Application Number
- CN202211108358.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-09-13
- Publication Date
- 2025-01-03
- Estimated Expiration
- 2042-09-13
AI Technical Summary
In the existing back processing technology of silicon carbide wafers, the glass carrier plate has poor heat resistance during high-temperature tempering process, and the SOG fixing effect cannot effectively fix the silicon carbide wafer during grinding and thinning, resulting in displacement and fixation instability.
The first silicon dioxide layer is deposited on the back and edges of the silicon carbide wafer by LPCVD process, and the second silicon dioxide layer is deposited in the pores of the glass carrier plate to form a double-layer silicon oxide structure, and the carbonization is fixed through vacuum adsorption by the exhaust device. Silicon wafers and are subjected to grinding, ion implantation, metal deposition and rapid tempering in subsequent steps.
The positioning and fixing without adhesive is achieved, the high-temperature stability and fixing ability of the silicon carbide wafer are enhanced, the problems of insufficient displacement and fixing force are avoided, and the stability in the high-temperature process and grinding and thinning process is ensured.
Smart Images
Figure CN115472550B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of silicon carbide wafer processing, and specifically to a silicon carbide wafer back side processing technology. Background Art
[0002] Silicon carbide wafer, also known as silicon carbide single crystal sheet, is a sheet-like single crystal material obtained by cutting, grinding and polishing silicon carbide crystals along a specific crystal direction.
[0003] After the silicon carbide wafer completes the front-side process, it is necessary to flip the silicon carbide wafer over for the back-side process and carry it on a glass carrier to facilitate the loading and transfer of the silicon carbide wafer during processing.
[0004] In the prior art, silicon carbide wafers and glass carriers are usually fixed by SOG coating. However, when performing a high-temperature annealing process on the back side, the glass carrier has poor high-temperature resistance and is not convenient for directly carrying silicon carbide crystals for high-temperature processes. Also, when thinning the silicon carbide wafer, the fixing effect of the coated SOG is poor and the fixing ability cannot withstand the force from the grinding equipment during grinding and thinning. Summary of the invention
[0005] The purpose of the present invention is to provide a silicon carbide wafer back side processing technology 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 backside processing process comprises the following steps:
[0008] S1. Take a silicon carbide wafer that has completed the first half of the process, attach the front side of the silicon carbide wafer to a glass carrier with air holes, use a vacuum device to evacuate air under the glass carrier, vacuum-absorb the silicon carbide wafer on the glass carrier, and then use the LPCVD process to deposit a first silicon dioxide layer on the back and edge of the silicon carbide wafer, then remove the vacuum device, and finally perform the LPCVD process again to deposit a second silicon dioxide layer to cover the silicon carbide wafer and the glass carrier;
[0009] S2, for the silicon carbide wafer obtained in step S1, then start grinding from the back side of the silicon carbide wafer, first grind off the first silicon dioxide layer and the second silicon dioxide layer on the back side of the silicon carbide wafer, then grind and thin the back side of the silicon carbide wafer, and after thinning, perform ion implantation and metal deposition on the back side of the silicon carbide wafer to form a metal deposition layer on the back side of the silicon carbide wafer;
[0010] S3, the silicon carbide wafer obtained in step S2 is rapidly annealed by RTA process to activate the ions implanted on the back side to form ohmic contact, and then a glass carrier with air holes is taken, the back side of the silicon carbide wafer is attached to the glass carrier, and the gas is exhausted from the bottom of the glass carrier by using an exhaust device to vacuum the silicon carbide wafer onto the glass carrier;
[0011] S4. For the silicon carbide wafer obtained in step S2, the first silicon dioxide layer and the second silicon dioxide layer are etched away by a solvent, and then the glass carrier attached to the front side of the silicon carbide wafer is removed, and then the vacuuming of the vacuum equipment is stopped and the vacuum equipment is removed, and finally the glass carrier attached to the back side of the silicon carbide wafer is removed to obtain a glass carrier that has completed the back side process.
[0012] Preferably, in step S1, the front side process of the silicon carbide wafer includes transistor manufacturing, ion implantation, high temperature annealing and ILD layer manufacturing.
[0013] Preferably, in step S1, the deposited first silicon dioxide layer will cover the back side and edge of the silicon carbide wafer, as well as the side where the glass carrier contacts the silicon carbide wafer, and the deposited second silicon dioxide layer will cover the outside of the glass carrier of the silicon carbide wafer, and be deposited into the pores of the glass carrier to fix the silicon carbide wafer.
[0014] Preferably, in step S3, the RTP process can also be used for the rapid annealing of the silicon carbide wafer.
[0015] Preferably, in step S3, when the back side of the silicon carbide wafer is attached to the glass carrier, the metal deposition layer on the back side of the silicon carbide wafer is the contact surface between the silicon carbide wafer and the glass carrier.
[0016] Preferably, in step S4, the solvent used to etch the first silicon dioxide layer and the second silicon dioxide layer is hydrofluoric acid.
[0017] Beneficial effects of the present invention:
[0018] By depositing the first silicon dioxide layer, the silicon carbide wafer and the glass carrier can be positioned without using adhesive to ensure that the silicon carbide wafer will not be displaced on the glass carrier when the vacuum equipment is removed. In addition, silicon dioxide has strong high temperature resistance, which makes it convenient to fix the silicon carbide wafer to the glass carrier for subsequent high-temperature processes.
[0019] The silicon carbide wafer and the outer surface of the glass carrier are then coated together with a second silicon dioxide layer to increase the thickness of the silicon dioxide on the outside of the silicon carbide wafer, and then the bottom of the silicon carbide wafer is fixed with the second silicon dioxide layer inside the pores, which provides a stronger fixing ability and avoids the situation where the silicon carbide wafer is fixed only by the first silicon dioxide layer, and the fixing ability cannot withstand the force from the grinding equipment during grinding and thinning. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] 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, for those skilled in the art, other drawings can be obtained based on these drawings without creative work.
[0021] Figure 1 is a schematic flow chart of step S1 of the present invention;
[0022] Figure 2 is a schematic flow chart of step S2 of the present invention;
[0023] Figure 3 It is a schematic diagram of the process of step S3 of the present invention;
[0024] Figure 4 It is a schematic flow chart of step S4 of the present invention.
[0025] The reference numerals in the figures are as follows:
[0026] 1. Silicon carbide wafer, 2. ILD layer, 3. Glass carrier, 4. Air holes, 5. Exhaust equipment, 6. First silicon dioxide layer, 7. Second silicon dioxide layer, 8. Metal deposition layer, 9. Ohmic contact. DETAILED DESCRIPTION
[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.
[0028] A silicon carbide wafer backside processing process comprises the following steps:
[0029] S1. Take a silicon carbide wafer that has completed the first half of the process, attach the front side of the silicon carbide wafer to a glass carrier with air holes, use a vacuum device to evacuate air under the glass carrier, vacuum-absorb the silicon carbide wafer on the glass carrier, and then use the LPCVD process to deposit a first silicon dioxide layer on the back and edge of the silicon carbide wafer, then remove the vacuum device, and finally perform the LPCVD process again to deposit a second silicon dioxide layer to cover the silicon carbide wafer and the glass carrier;
[0030] S2, for the silicon carbide wafer obtained in step S1, then start grinding from the back side of the silicon carbide wafer, first grind off the first silicon dioxide layer and the second silicon dioxide layer on the back side of the silicon carbide wafer, then grind and thin the back side of the silicon carbide wafer, and after thinning, perform ion implantation and metal deposition on the back side of the silicon carbide wafer to form a metal deposition layer on the back side of the silicon carbide wafer;
[0031] S3, the silicon carbide wafer obtained in step S2 is rapidly annealed by RTA process to activate the ions implanted on the back side to form ohmic contact, and then a glass carrier with air holes is taken, the back side of the silicon carbide wafer is attached to the glass carrier, and the gas is exhausted from the bottom of the glass carrier by using an exhaust device to vacuum the silicon carbide wafer onto the glass carrier;
[0032] S4. For the silicon carbide wafer obtained in step S2, the first silicon dioxide layer and the second silicon dioxide layer are etched away by a solvent, and then the glass carrier attached to the front side of the silicon carbide wafer is removed, and then the vacuuming of the vacuum equipment is stopped and the vacuum equipment is removed, and finally the glass carrier attached to the back side of the silicon carbide wafer is removed to obtain a glass carrier that has completed the back side process.
[0033] The LPCVD process is a low-pressure chemical vapor deposition method widely used for the deposition of silicon oxide, nitride, and polysilicon.
[0034] In step S1 , the front side process of the silicon carbide wafer includes transistor manufacturing, ion implantation, high temperature annealing and ILD layer manufacturing.
[0035] In step S1, the deposited first silicon dioxide layer will cover the back side and edge of the silicon carbide wafer, as well as the side where the glass carrier contacts the silicon carbide wafer, and the deposited second silicon dioxide layer will cover the outside of the glass carrier of the silicon carbide wafer, and be deposited into the pores of the glass carrier to fix the silicon carbide wafer.
[0036] By depositing a second silicon dioxide layer into the pores of the glass carrier, the silicon carbide wafer is better secured.
[0037] In step S3, the RTP process can also be used for the rapid annealing of the silicon carbide wafer.
[0038] RTA is to heat the silicon carbide wafer to a higher temperature, use different holding times according to the material and workpiece size, and then quickly cool it. The RTP process is a heat treatment method with a very fast heating speed and a very short holding time, both of which can quickly temper the silicon carbide wafer.
[0039] In step S3, when the back side of the silicon carbide wafer is attached to the glass carrier, the metal deposition layer on the back side of the silicon carbide wafer serves as the contact surface between the silicon carbide wafer and the glass carrier.
[0040] In the step S4, the solvent used for etching the first silicon dioxide layer and the second silicon dioxide layer is hydrofluoric acid.
[0041] Compared with the related art, the silicon carbide wafer backside processing technology provided by the present invention has the following beneficial effects:
[0042] By depositing the first silicon dioxide layer, the silicon carbide wafer and the glass carrier can be positioned without using adhesive to ensure that the silicon carbide wafer will not be displaced on the glass carrier when the vacuum equipment is removed. In addition, silicon dioxide has strong high temperature resistance, which makes it convenient to fix the silicon carbide wafer to the glass carrier for subsequent high-temperature processes.
[0043] The silicon carbide wafer and the outer surface of the glass carrier are then coated together with a second silicon dioxide layer to increase the thickness of the silicon dioxide on the outside of the silicon carbide wafer, and then the bottom of the silicon carbide wafer is fixed with the second silicon dioxide layer inside the pores, which provides a stronger fixing ability and avoids the situation where the silicon carbide wafer is fixed only by the first silicon dioxide layer, and the fixing ability cannot withstand the force from the grinding equipment during grinding and thinning.
[0044] 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 to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.
Claims
1. A silicon carbide wafer backside processing process, characterized in that: The following steps are involved: S1. Take a silicon carbide wafer that has completed the first half of the process, attach the front side of the silicon carbide wafer to a glass carrier with air holes, use a vacuum device to evacuate air under the glass carrier, vacuum-absorb the silicon carbide wafer on the glass carrier, and then use the LPCVD process to deposit a first silicon dioxide layer on the back and edge of the silicon carbide wafer, then remove the vacuum device, and finally perform the LPCVD process again to deposit a second silicon dioxide layer to cover the silicon carbide wafer and the glass carrier; S2, for the silicon carbide wafer obtained in step S1, then start grinding from the back side of the silicon carbide wafer, first grind off the first silicon dioxide layer and the second silicon dioxide layer on the back side of the silicon carbide wafer, then grind and thin the back side of the silicon carbide wafer, and after thinning, perform ion implantation and metal deposition on the back side of the silicon carbide wafer to form a metal deposition layer on the back side of the silicon carbide wafer; S3, the silicon carbide wafer obtained in step S2 is rapidly annealed by RTA process to activate the ions implanted on the back side to form ohmic contact, and then a glass carrier with air holes is taken, the back side of the silicon carbide wafer is attached to the glass carrier, and the gas is exhausted from the bottom of the glass carrier by using an exhaust device to vacuum the silicon carbide wafer onto the glass carrier; S4. For the silicon carbide wafer obtained in step S2, the first silicon dioxide layer and the second silicon dioxide layer are etched away by a solvent, and then the glass carrier attached to the front side of the silicon carbide wafer is removed, and then the vacuuming of the vacuum equipment is stopped and the vacuum equipment is removed, and finally the glass carrier attached to the back side of the silicon carbide wafer is removed to obtain a glass carrier that has completed the back side process.
2. A silicon carbide wafer backside processing process according to claim 1, characterized in that: In step S1 , the front side process of the silicon carbide wafer includes transistor manufacturing, ion implantation, high temperature annealing and ILD layer manufacturing.
3. A silicon carbide wafer back side processing process according to claim 1, characterized in that: In step S1, the deposited first silicon dioxide layer will cover the back side and edge of the silicon carbide wafer, as well as the side where the glass carrier contacts the silicon carbide wafer, and the deposited second silicon dioxide layer will cover the outside of the glass carrier of the silicon carbide wafer, and be deposited into the pores of the glass carrier to fix the silicon carbide wafer.
4. The back side processing process of a silicon carbide wafer according to claim 1, characterized in that: In step S3, the RTP process can also be used for the rapid annealing of the silicon carbide wafer.
5. The back side processing process of a silicon carbide wafer according to claim 1, characterized in that: In step S3, when the back side of the silicon carbide wafer is attached to the glass carrier, the metal deposition layer on the back side of the silicon carbide wafer serves as the contact surface between the silicon carbide wafer and the glass carrier.
6. The silicon carbide wafer back side processing process according to claim 1, characterized in that: In the step S4, the solvent used for etching the first silicon dioxide layer and the second silicon dioxide layer is hydrofluoric acid.