LPCVD (Low Pressure Chemical Vapor Deposition) film forming process method for improving super back sealing quality

Abstract

The invention relates to an LPCVD (Low Pressure Chemical Vapor Deposition) film forming process method for improving super back sealing quality, which belongs to the technical field of silicon wafer processing and comprises the following operation steps of: 1, placing a silicon wafer needing super back sealing LPCVD film forming on a quartz boat; 2, feeding the quartz boat loaded with the silicon wafer into a reaction furnace, sealing the reaction furnace, and vacuumizing; and thirdly, deposition is carried out in a low-pressure hot wall type reactor, and multi-section type processing and film covering are carried out at the temperature of 615-645 DEG C in chemical vapor deposition. And 4, after the deposition film forming process is completed, stopping the passing of the film forming gas, then vacuumizing the reaction chamber, and then backflushing N2 to restore the reaction chamber to normal pressure. And 5, polishing after the super back sealing LPCVD film formation of the silicon wafer is completed, and removing the defects of bending and warping through polishing. The problem that the bending degree value and the warping degree value are high during super back sealing chemical vapor deposition is solved. The bow / warp flatness yield is effectively improved, and the rework cost of defective products is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon wafer processing, and in particular to a LPCVD film forming process method for improving the quality of super back seal. Background Art

[0002] LPCVD polysilicon film is prepared by low-pressure chemical vapor deposition. When silicon wafers are undergoing LPCVD chemical vapor deposition of polysilicon film, since LPCVD is a double-sided film formation and stress is balanced, after single-sided processing through the polishing process, a certain amount of stress will be released, causing the silicon wafer to have a certain amount of warping, affecting the values ​​of the curvature and warp. The bow / warp value is the value of the curvature and warp.

[0003] The LPCVD film forming temperature of super back-sealing chemical vapor deposition is 640-650℃, and the bow / warp values ​​of the processed products are 20-22μm / 22-24μm, and some of the values ​​are too large. For the card control standard of a certain product on the production line, the values ​​that are too large (>21μm and>23μm) are defective products, and the cost increases if rework is required, which has obvious disadvantages, so it is necessary to optimize the parameters to reduce bow / warp.

[0004] The current LPCVD film-forming temperature process parameters of super back-sealing chemical vapor deposition are not sufficient to meet the 100% bow / warp flatness yield requirement, and good bow / warp warpage has an important impact on the subsequent processing yield and final product performance. Summary of the invention

[0005] The present invention mainly solves the deficiencies in the prior art and provides an LPCVD film forming process method for improving the quality of super back seal, which has the advantages of convenient operation and good quality stability. It solves the problem of high curvature and warp values ​​during chemical vapor deposition of super back seal, effectively improves the bow / warp flatness yield and reduces the rework cost of defective products.

[0006] The above technical problems of the present invention are mainly solved by the following technical solutions: A LPCVD film forming process method for improving the quality of super back seal includes the following steps: Step 1: Place the silicon wafer that needs to undergo super back-sealing LPCVD film formation on a quartz boat.

[0007] Step 2: Place the quartz boat carrying the silicon wafers into the reaction furnace, seal the reaction furnace and evacuate it.

[0008] Step 3: Deposition is carried out in a low-pressure hot wall reactor, and chemical vapor deposition uses a temperature of 615 to 645°C for multi-stage processing and coating.

[0009] Step 4: After the deposition process is completed, the flow of the film-forming gas is closed, and then the reaction chamber is evacuated, and then N2 is back-flushed to restore the reaction chamber to normal pressure.

[0010] Step 5: After the super back-sealing LPCVD film formation of the silicon wafer is completed, polishing is performed to remove defects such as curvature and warping.

[0011] The silicon wafer after super back-sealing LPCVD film formation is subjected to mechanical chemical polishing, and the polishing liquid is a weakly alkaline colloidal SiO2 (particle size 10nm) aqueous solution. The polishing cloth uses a soft foamed polyurethane artificial leather with a fine surface structure. Under high-speed and high-pressure polishing conditions, a closed polishing agent layer is formed between the polishing cloth and the silicon wafer. At the same time, a soft hydrated film is formed on the surface of the silicon wafer, and the polishing disc polishes the silicon wafer by continuously removing the hydrated film.

[0012] One mechanical chemical polishing cannot obtain a surface without a processed deteriorated layer. In order to improve the polishing efficiency, polishing should be performed twice.

[0013] In the first polishing, the hydration film on the surface of the silicon wafer is destroyed by the mechanical action of the abrasive and the polishing cloth for efficient polishing. Therefore, large-sized abrasive and polishing cloth with good air permeability must be used to form a thinner hydration film, the purpose of which is to obtain the thickness and flatness of the silicon wafer. The removal amount of one polishing is about 1.5μm. The polishing liquid used in the first polishing is to add alkaline additives such as NaOH and KOH to the SiO2 suspension to make the pH of the polishing liquid = 11. The polishing cloth used for the first polishing is a non-woven fabric permeated with polyurethane.

[0014] The polishing cloth used for secondary polishing is made of foamed polyurethane leather. Secondary polishing is fine polishing, which is a non-damaging polishing by continuously removing the hydration film. The polishing liquid used for secondary polishing is added with alkali or ammonia, pH=9. The processing amount of secondary polishing is generally less than 1μm.

[0015] Preferably, the first LPCVD film forming temperature is 620-640°C, the processing time is 20-30 minutes, and the processed film thickness is 3000-5000 angstroms; the second LPCVD film forming temperature is 620-640°C, the processing time is 30-40 minutes, and the processed film thickness is 5000-7000 angstroms; the third LPCVD film forming temperature is 620-640°C, the processing time is 50-60 minutes, and the processed film thickness is 7000-9000 angstroms.

[0016] Preferably, silane is used for deposition in a low-pressure hot wall reactor. After being adsorbed on the substrate, the silane decomposes to generate silicon, which migrates and arranges on the substrate to form a polycrystalline silicon film.

[0017] Preferably, after evacuation, SiH4 and N2 are introduced to form a film by deposition.

[0018] Preferably, during film formation, the flow rate of SiH4 introduced is 0.3-0.9 SLM, and the flow rate of N2 introduced is 0.9-3.8 SLM.

[0019] Preferably, the pressure inside the core tube of the deposition film forming furnace is controlled at 10-30Pa.

[0020] The present invention can achieve the following effects: The present invention provides an LPCVD film forming process method for improving the quality of super back seal, which has the advantages of convenient operation and good quality stability compared with the prior art. It solves the problem of high curvature and warp values ​​during super back seal chemical vapor deposition, effectively improves the bow / warp flatness yield, and reduces the rework cost of defective products. DETAILED DESCRIPTION

[0021] The technical solution of the invention is further specifically described below through embodiments.

[0022] Embodiment 1: A LPCVD film forming process method for improving the quality of super back seal, comprising the following steps: Step 1: Place the silicon wafer that needs to undergo super back-sealing LPCVD film formation on a quartz boat.

[0023] Step 2: Place the quartz boat carrying the silicon wafers into the reaction furnace, seal the reaction furnace and evacuate it.

[0024] The third step: Deposition is carried out in a low-pressure hot wall reactor. Chemical vapor deposition uses a temperature of 615-645°C for multi-stage processing and coating. The pressure in the film deposition furnace core tube is controlled at 10-30 Pa. Silane is used for deposition in a low-pressure hot wall reactor. After silane is adsorbed on the substrate, it decomposes to generate silicon, which migrates and arranges on the substrate to form a polycrystalline silicon film.

[0025] The first LPCVD film forming temperature is 620-640°C, the processing time is 20-30 minutes, and the processed film thickness is 3000-5000 angstroms; the second LPCVD film forming temperature is 620-640°C, the processing time is 30-40 minutes, and the processed film thickness is 5000-7000 angstroms; the third LPCVD film forming temperature is 620-640°C, the processing time is 50-60 minutes, and the processed film thickness is 7000-9000 angstroms.

[0026] Step 4: After the deposition process is completed, the flow of the film-forming gas is closed, and then the reaction chamber is evacuated, and then N2 is back-flushed to restore the reaction chamber to normal pressure.

[0027] Step 5: After the super back-sealing LPCVD film formation of the silicon wafer is completed, polishing is performed to remove defects such as curvature and warping.

[0028] Embodiment 2: A LPCVD film forming process method for improving the quality of super back seal, comprising the following steps: Step 1: Place the silicon wafer that needs to undergo super back-sealing LPCVD film formation on a quartz boat.

[0029] Step 2: Place the quartz boat carrying the silicon wafers into the reaction furnace, seal the reaction furnace and evacuate it.

[0030] Step 3: After vacuuming, SiH4 and N2 are introduced for deposition and film formation. During film formation, the flow rate of SiH4 is 0.3-0.9SLM, and the flow rate of N2 is 0.9-3.8SLM. Deposition is carried out in a low-pressure hot wall reactor, and chemical vapor deposition uses a temperature of 615-645°C for multi-stage processing and film coating. The pressure in the deposition film furnace core tube is controlled at 10-30Pa.

[0031] The first LPCVD film forming temperature is 620-640°C, the processing time is 20-30 minutes, and the processed film thickness is 3000-5000 angstroms; the second LPCVD film forming temperature is 620-640°C, the processing time is 30-40 minutes, and the processed film thickness is 5000-7000 angstroms; the third LPCVD film forming temperature is 620-640°C, the processing time is 50-60 minutes, and the processed film thickness is 7000-9000 angstroms.

[0032] Step 4: After the deposition process is completed, the flow of the film-forming gas is closed, and then the reaction chamber is evacuated, and then N2 is back-flushed to restore the reaction chamber to normal pressure.

[0033] Step 5: After the super back-sealing LPCVD film formation of the silicon wafer is completed, polishing is performed to remove defects such as curvature and warping.

[0034] After the LPCVD film forming temperature dropped from 640-650℃ to 620-640℃, the bow / warp average value in the super back-sealing chemical vapor deposition quality decreased from 20-22μm / 22-24μm to 16-18μm / 18-20μm.

[0035] In summary, the LPCVD film forming process method for improving the quality of super back seal has the advantages of convenient operation and good quality stability. It solves the problem of high curvature and warp values ​​during chemical vapor deposition of super back seal. It effectively improves the bow / warp flatness yield and reduces the rework cost of defective products.

[0036] 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 LPCVD film forming process for improving the quality of super back seal, characterized in that The steps are as follows: Step 1: Place the silicon wafer that needs to be super back-sealed LPCVD film-forming on the quartz boat; Step 2: Place the quartz boat carrying the silicon wafer into the reaction furnace, seal the reaction furnace and evacuate it; Step 3: Deposition is carried out in a low-pressure hot wall reactor, and chemical vapor deposition uses a temperature of 615-645°C for multi-stage processing and coating; Step 4: After the deposition process is completed, the flow of the film-forming gas is closed, and then the reaction chamber is evacuated, and then N2 is back-flushed to restore the reaction chamber to normal pressure; Step 5: After the super back-sealing LPCVD film formation of the silicon wafer is completed, polishing is performed to remove defects such as curvature and warping.

2. The LPCVD film forming process for improving the quality of super back seal according to claim 1, characterized in that: The first LPCVD film forming temperature is 620-640°C, the processing time is 20-30 minutes, and the processed film thickness is 3000-5000 angstroms; the second LPCVD film forming temperature is 620-640°C, the processing time is 30-40 minutes, and the processed film thickness is 5000-7000 angstroms; the third LPCVD film forming temperature is 620-640°C, the processing time is 50-60 minutes, and the processed film thickness is 7000-9000 angstroms.

3. The LPCVD film forming process for improving the quality of super back seal according to claim 2, characterized in that: Silane is used for deposition in a low-pressure hot wall reactor. After being adsorbed on the substrate, the silane decomposes to generate silicon, which migrates and arranges on the substrate to form a polycrystalline silicon film.

4. The LPCVD film forming process for improving the quality of super back seal according to claim 2, characterized in that: After evacuation, SiH4 and N2 are introduced to deposit and form a film.

5. The LPCVD film forming process for improving the quality of super back seal according to claim 4, characterized in that: During film formation, the flow rate of SiH4 is 0.3~0.9SLM, and the flow rate of N2 is 0.9~3.8SLM.

6. The LPCVD film forming process for improving the quality of super back seal according to claim 1, characterized in that: The pressure inside the core tube of the deposition film forming furnace is controlled at 10~30Pa.