Process method for optimizing back sealing of silicon wafer

Abstract

The invention relates to a process method for optimizing back sealing of a silicon wafer, which belongs to the technical field of silicon wafer processing and comprises the following operation steps of: 1, controlling the temperature in a cleaning process before a film is formed on the silicon wafer; 2, when the silicon wafer enters the quartz boat to be subjected to LPCVD film forming, the film forming temperature of the LPCVD process is adjusted to 665 DEG C from 650 DEG C; 3, after the temperature is increased, the thermal decomposition reaction of the silane is complete, the film thickness and the uniformity can change, and the air inlet flow of the silane and the nitrogen needs to be adjusted. By improving the control of the film forming temperature, the silane decomposition is more complete, the polycrystal growth is more complete, the existence of the internal stress of the film is reduced, and the effect of optimizing the back sealing of the silicon wafer is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of silicon wafer processing, and in particular to a process method for optimizing silicon wafer back sealing. Background Art

[0002] Back-sealing technology is an important means to reduce the self-doping effect of silicon wafers. In the back-sealing process, POLY (inside) + SiO2 (outside), POLY is grown first, and the film quality of POLY has a great influence on the subsequent silicon wafer deformation.

[0003] Taking POLY (8000A) + SiO2 (3500A) as an example, the conventional film forming process is 650°C. After the double-layer back seal is completed, the front side is polished and the flatness data is measured after polishing. 1408 300mm silicon wafers were selected for testing. The average value before the CVD process was 13.5874um. After the CVD (POLY + SiO2) process, the Warp increased to an average of 51.3707um. The increase was 37.7833um, which was a significant deterioration.

[0004] Analysis of the cause of the deterioration showed that 650°C was not suitable for the growth of POLY with this film thickness, resulting in incomplete growth of POLY crystals and large internal stress caused by lattice mismatch. Summary of the invention

[0005] The present invention mainly solves the deficiencies in the prior art and provides a process method for optimizing silicon wafer back sealing, which achieves the effect of optimizing silicon wafer back sealing by improving the control of film forming temperature, making silane decomposition more complete, polycrystalline growth more complete, reducing the existence of stress in the film.

[0006] The above technical problems of the present invention are mainly solved by the following technical solutions: A process for optimizing silicon wafer back sealing includes the following steps: Step 1: Temperature control of the cleaning process before film formation on silicon wafers.

[0007] Step 2: When the silicon wafer enters the quartz boat for LPCVD film formation, the LPCVD process film forming temperature is adjusted from 650°C to 665°C.

[0008] Step 3: After the temperature is raised, the thermal decomposition reaction of silane is complete, the film thickness and uniformity will change, and the intake flow rate of silane and nitrogen needs to be adjusted.

[0009] Preferably, within the main reaction chamber, gallium arsenide is formed on the wafer surface in two stages: arsenic trichloride is bubbled into the initial portion of the reaction furnace where it reacts with solid gallium placed in a boat.

[0010] Preferably, AsCI3 reacts with H2 in the initial part to form As: 4AsCI3+6H2→12HCI+As4. Arsenic is deposited on gallium to form a hard shell.

[0011] Preferably, the flow rate of silane is within the range of standard cubic centimeters per minute, while the flow rate of nitrogen is relatively large; nitrogen is the main carrier gas, and the flow rate of silane is small, with a ratio of 10:1 to 100:1.

[0012] Preferably, for the PECVD process, the purity of the gas is very important, as impurities will affect the quality and performance of the film; the purity of silane is above 99.999%, and the purity of nitrogen is above 99.9999%.

[0013] Preferably, in the PECVD process, N2O is introduced to provide oxygen atoms to improve the chemical properties and stability of the film; when nitrous oxide is used, its flow rate is usually smaller than that of silane and nitrogen, with a ratio of 1:10 to 1:100.

[0014] Preferably, during chemical cleaning, the ionic adsorbed impurities are first removed, and then the remaining ionic impurities and atomic impurities are removed; finally, the silicon wafer is rinsed clean with high-purity deionized water, and then heated, dried or spun dry to obtain a silicon wafer with a clean surface.

[0015] Preferably, the silicon wafer is first cleaned with an acidic solution having a composition ratio of H2SO4:H2O2=5:1 or 4:1; the strong oxidizing property of the cleaning solution decomposes and removes the organic matter.

[0016] Preferably, after rinsing with ultrapure water, it is then cleaned with an alkaline cleaning solution with a component ratio of H2O:H2O2:NH4OH=5:2:1 or 5:1:1 or 7:2:1. Due to the oxidation effect of H2O2 and the complexation effect of NH4OH, many metal ions form stable soluble complexes and dissolve in water.

[0017] Preferably, an acidic cleaning solution with a composition ratio of H2O:H2O2:HCL=7:2:1 or 5:2:1 is used. Due to the oxidation of H2O2, the dissolution of hydrochloric acid, and the complexing property of chloride ions, many metals generate complex ions soluble in water, thereby achieving the purpose of cleaning.

[0018] The present invention can achieve the following effects: The present invention provides a process method for optimizing silicon wafer back sealing. Compared with the prior art, by improving the control of film forming temperature, silane decomposition is more complete, polycrystalline growth is more complete, and the existence of stress in the film is reduced, thereby achieving the effect of optimizing silicon wafer back sealing. DETAILED DESCRIPTION

[0019] The technical solution of the invention is further specifically described below through embodiments.

[0020] Embodiment: A process method for optimizing silicon wafer back sealing includes the following steps: Step 1: Temperature control of the cleaning process before film formation on silicon wafers.

[0021] During chemical cleaning, the ionic adsorbed impurities are removed first, and then the remaining ionic impurities and atomic impurities are removed; finally, the silicon wafer is rinsed clean with high-purity deionized water, and then heated, dried or spun dry to obtain a silicon wafer with a clean surface.

[0022] The silicon wafer is first cleaned with an acidic solution with a composition ratio of H2SO4:H2O2=5:1 or 4:1; the strong oxidizing property of the cleaning solution decomposes and removes organic matter. After rinsing with ultrapure water, it is then cleaned with an alkaline cleaning solution with a composition ratio of H2O:H2O2:NH4OH=5:2:1 or 5:1:1 or 7:2:1. Due to the oxidation of H2O2 and the complexation of NH4OH, many metal ions form stable soluble complexes and dissolve in water. Using an acidic cleaning solution with a composition ratio of H2O:H2O2:HCL=7:2:1 or 5:2:1, due to the oxidation of H2O2 and the dissolution of hydrochloric acid, as well as the complexation of chloride ions, many metals generate complex ions soluble in water, thereby achieving the purpose of cleaning.

[0023] Step 2: When the silicon wafer enters the quartz boat for LPCVD film formation, the LPCVD process film forming temperature is adjusted from 650°C to 665°C.

[0024] In the main reaction chamber, the formation of GaAs on the wafer surface goes through two stages: Arsenic trichloride is bubbled into the starting part of the reactor, where it reacts with solid gallium placed in the boat. AsCI3 reacts with H2 in the starting part to form As: 4AsCI3+6H2→12HCI+As4, and arsenic is deposited on the gallium to form a hard shell.

[0025] Step 3: After the temperature is raised, the thermal decomposition reaction of silane is complete, the film thickness and uniformity will change, and the intake flow rate of silane and nitrogen needs to be adjusted.

[0026] The flow rate of silane is in the range of standard cubic centimeters per minute, while the flow rate of nitrogen is relatively large; nitrogen is the main carrier gas, and the flow rate of silane is small, with a ratio of 10:1 to 100:1. For the PECVD process, the purity of the gas is very important, and impurities will affect the quality and performance of the film; the purity of silane is above 99.999%, and the purity of nitrogen is above 99.9999%.

[0027] In the PECVD process, N2O is introduced to provide oxygen atoms to improve the chemical properties and stability of the film; when nitrous oxide is used, its flow rate is usually smaller than that of silane and nitrogen, with a ratio of 1:10 to 1:100.

[0028] In summary, the process method for optimizing the silicon wafer back seal improves the control of the film forming temperature, makes the silane decomposition more complete, the polycrystalline growth more complete, reduces the existence of stress in the film, and achieves the effect of optimizing the silicon wafer back seal.

[0029] The above description is only a specific embodiment of the present invention, but the structural features of the present invention are not limited thereto. Any changes or modifications made by any technician in the field of the present invention are included in the patent scope of the present invention.

Claims

1. A process for optimizing silicon wafer back sealing, characterized in that The steps are as follows: Step 1: Temperature control of the cleaning process before film formation on silicon wafers; Step 2: When the silicon wafer enters the quartz boat for LPCVD film formation, the LPCVD process film forming temperature is adjusted from 650°C to 665°C; Step 3: After the temperature is raised, the thermal decomposition reaction of silane is complete, the film thickness and uniformity will change, and the intake flow rate of silane and nitrogen needs to be adjusted.

2. The process for optimizing silicon wafer back sealing according to claim 1, characterized in that: In the main reaction chamber, GaAs is formed on the wafer surface in two stages: Arsenic trichloride is bubbled into the initial part of the reaction furnace, where it reacts with solid gallium placed in a boat.

3. The process for optimizing silicon wafer back sealing according to claim 2, characterized in that: AsCI3 reacts with H2 in the initial part to form As: 4AsCI3+6H2→12HCI+As4. Arsenic is deposited on gallium to form a hard shell.

4. The process for optimizing silicon wafer back sealing according to claim 1, characterized in that: The flow rate of silane is in the range of standard cubic centimeters per minute, while the flow rate of nitrogen is relatively large; nitrogen is the main carrier gas, and the flow rate of silane is small, with a ratio of 10:1 to 100:

1.

5. The process for optimizing silicon wafer back sealing according to claim 4, characterized in that: For the PECVD process, gas purity is very important, as impurities can affect the quality and performance of the film; the purity of silane is above 99.999%, and the purity of nitrogen is above 99.9999%.

6. The process for optimizing silicon wafer back sealing according to claim 1, characterized in that: In the PECVD process, N2O is introduced to provide oxygen atoms to improve the chemical properties and stability of the film; when nitrous oxide is used, its flow rate is usually smaller than that of silane and nitrogen, with a ratio of 1:10 to 1:

100.

7. The process for optimizing silicon wafer back sealing according to claim 1, characterized in that: During chemical cleaning, the ionic adsorbed impurities are removed first, and then the remaining ionic impurities and atomic impurities are removed; finally, the silicon wafer is rinsed clean with high-purity deionized water, and then heated, dried or spun dry to obtain a silicon wafer with a clean surface.

8. The process for optimizing silicon wafer back sealing according to claim 7, characterized in that: The silicon wafer is first cleaned with an acidic solution with a composition ratio of H2SO4:H2O2=5:1 or 4:1; the strong oxidizing property of the cleaning solution decomposes and removes the organic matter.

9. The process for optimizing silicon wafer back sealing according to claim 8, characterized in that: After rinsing with ultrapure water, clean it with an alkaline cleaning solution with a composition ratio of H2O:H2O2:NH4OH=5:2:1 or 5:1:1 or 7:2:

1. Due to the oxidation effect of H2O2 and the complexation effect of NH4OH, many metal ions form stable soluble complexes and dissolve in water.

10. The process for optimizing silicon wafer back sealing according to claim 9, characterized in that: Use an acidic cleaning solution with a composition ratio of H2O:H2O2:HCL=7:2:1 or 5:2:

1. Due to the oxidation of H2O2, the dissolution of hydrochloric acid, and the complexing property of chloride ions, many metals generate complex ions soluble in water, thereby achieving the purpose of cleaning.