Process method for improving surface roughness of silicon wafer

Abstract

The invention relates to a process method for improving the surface roughness of a silicon wafer, which belongs to the technical field of silicon wafer production and comprises the following operation steps of: 1, roughly grinding two surfaces of a sliced silicon wafer; 2, cleaning the silicon wafer by adopting an SC1 solution and pure water, and meanwhile, carrying out ultrasonic treatment; and 3, carrying out chemical corrosion by soaking the silicon wafer in an acid solution or an alkaline solution. And 4, carrying out chemical corrosion, and cleaning in a QDR tank. And 5, carrying out fine grinding. And 6, carrying out chemical vapor deposition treatment, and growing an oxide layer or a polycrystalline silicon film with a certain thickness on the back surface of the silicon wafer. The method has the advantages of convenient operation and good operation stability. And the surface roughness of the silicon wafer and the capability of adsorbing and sputtering metal are improved. The surface roughness is improved, and the silicon wafer with relatively good flatness is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon wafer production, and particularly relates to a process method for improving the surface roughness of silicon wafers. Background Art

[0002] With the development trend of semiconductor technology towards high integration and high performance, higher requirements are put forward for the surface flatness of silicon wafers. Micro-roughness seriously affects the electrical properties of the gate oxide layer of MOS devices, such as the dielectric breakdown field strength of the gate oxide layer, breakdown charge density, channel carrier mobility, etc., and has gradually attracted the attention of chip manufacturers.

[0003] Polishing haze is a light scattering phenomenon caused by the irregularity of the micro-surface profile, which can reflect the overall micro-roughness of the silicon wafer surface and has become one of the key parameters for characterizing the micro-roughness of the silicon wafer surface. After slicing the silicon wafer, it needs to go through two thinning steps of mechanical grinding and chemical etching in sequence to remove the damaged layer and achieve the purpose of the specified back surface state. For single-sided polished silicon wafers, the roughness after mechanical grinding and the roughness after chemical etching determine the final back surface state of the silicon wafer. In silicon wafer processing, surface unevenness is a common and difficult problem, which directly affects the spin coating effect and the final quality of the chip.

[0004] Chinese Patent "A Polishing Process for Improving the Surface Roughness of Silicon Wafers", application number: CN202111389663.3, discloses that after the finish polishing, the surface of the silicon wafer is quickly treated with a surface treatment liquid; the surface treatment liquid includes: 1-3 parts by volume of zwitterionic surfactant, 2-3 parts by volume of ethylene glycol, 0.5-2 parts of anionic surfactant containing hydroxyl groups, and 100 parts by volume of ultrapure water.

[0005] The surface treatment liquid is used to quickly treat the silicon wafer after the finish polishing, and it mainly reduces the Haze value of the silicon wafer from three aspects: (1) quickly reducing the temperature of the silicon wafer surface after the finish polishing to relieve chemical etching; (2) isolating the polishing liquid to slow down and finally stop the chemical etching effect between the polishing liquid and the silicon wafer surface; (3) making the particles generated during the polishing process detach from the silicon wafer surface, thereby removing surface particles and achieving the reduction of scratches on the silicon wafer surface.

[0006] The improvement direction of the Haze value mainly focuses on improving auxiliary materials such as polishing cloth and polishing liquid. The existing technology performs surface chemical treatment after the finish polishing. This method only improves the surface roughness of the silicon wafer, but cannot improve the ability of the silicon wafer surface to adsorb sputtered metal. Summary of the Invention

[0007] The present invention mainly solves the deficiencies existing in the prior art, and provides a process method for improving the surface roughness of silicon wafers, which has the advantages of convenient operation and good running stability. It improves the surface roughness of silicon wafers and the ability to adsorb sputtered metal. The surface roughness is improved, and silicon wafers with better flatness are obtained.

[0008] The above technical problems of the present invention are mainly solved by the following technical solutions:

[0009] A process method for improving the surface roughness of silicon wafers includes the following operating steps:

[0010] The first step: Rough grinding is carried out on both sides of the sliced silicon wafers. The particle size of the grinding powder in the rough grinding liquid is 1000 mesh, and the ratio density is 1.30 ± 0.1 g / cm 3 ; The upper platen is fixed, the lower platen rotates at 30 ± 5 rpm / min, the carrier revolves at 15 ± 2.5 rpm / min, and the grinding pressure is 900 ± 50 kg.

[0011] The second step: Before chemical etching of the silicon wafers after rough grinding, the silicon wafers are cleaned with SC1 solution and pure water, and ultrasonic is used as an auxiliary. SC1 (Standard Clean-1) solution is a cleaning solution used in semiconductor manufacturing, mainly composed of ammonia water, hydrogen peroxide and water. Its ratio is ammonia water: hydrogen peroxide: ultrapure water = 1:1:6. The SC1 solution can effectively remove organic pollutants and almost all particulate matters on the wafer surface.

[0012] The third step: Chemical etching is carried out by immersing the silicon wafers in an acidic solution or an alkaline solution to remove organic pollutants and metal impurities on the surface, making the surface smoother and more uniform.

[0013] The fourth step: After chemical etching, it enters the QDR tank for cleaning.

[0014] The fifth step: Fine grinding is carried out. The particle size of the grinding powder in the fine grinding liquid is 1200 mesh, and the ratio density is 1.30 ± 0.1 g / cm 3 ; The upper platen is fixed, the lower platen rotates at 20 ± 5 rpm / min, the carrier revolves at 10 ± 2.5 rpm / min, and the grinding pressure is 400 ± 50 kg.

[0015] The sixth step: Chemical vapor deposition treatment is carried out to grow an oxide layer or a polysilicon film with a certain thickness on the back surface of the silicon wafer to prevent self-doping phenomenon and achieve the "internal gettering" effect.

[0016] Silicon wafer grinding powder is an important material in the semiconductor industry, mainly used to remove defects on the surface of silicon wafers and improve surface quality. Silicon wafer grinding powder can remove the oxide layer and mechanical scratches on the surface of silicon wafers, making the surface of silicon wafers smoother and flatter. At the same time, silicon wafer grinding powder can also improve the optical and electrical properties of the silicon wafer surface, enhancing the performance and stability of the silicon wafer.

[0017] The particle size of silicon wafer grinding powder has a very important influence on the grinding effect. Generally, the smaller the particle size of the grinding powder, the better the effect of removing defects on the surface of the silicon wafer and improving surface quality. However, too small a particle size will also cause damage to the silicon wafer surface, affecting the performance and stability of the silicon wafer. Therefore, when selecting silicon wafer grinding powder, it is necessary to select an appropriate particle size according to specific processing requirements.

[0018] Preferably, 3 - 7L of suspension dispersant and 0.2 ± 0.05L of defoaming agent are added during both rough grinding and fine grinding, and the temperature of the fixed disk cooling water is 23 ± 3°C; 25 silicon wafers are processed in one batch, the removal amount during rough grinding is 60 ± 5μm, and the removal amount during fine grinding is 5 ± 2μm.

[0019] Preferably, chemical etching uses a KOH solution with a concentration of 45 - 55wt.%, a temperature of 75 - 95°C, the etching removal amount is 25 - 35μm, and the surface roughness of the silicon wafer is adjusted according to the removal amount of alkali etching.

[0020] Preferably, during chemical etching, NH40H solution and Na0H solution are used to replace the KOH solution for alkali washing to remove impurities, removing organic pollutants and metal impurities on the surface, making the surface smoother and more uniform.

[0021] Preferably, during chemical etching, HF, HCl, HNO3 or H2S04 is used for pickling to remove impurities, removing impurities and oxide layers on the surface of the silicon wafer, improving surface cleanliness and reactivity.

[0022] Preferably, the pure water flow rate for QDR tank cleaning is 20 - 30L / min, and the cleaning time is 80 - 100s.

[0023] Preferably, before chemical vapor deposition treatment, sand grains are evenly sprayed onto the back surface of the silicon wafer through high-pressure air flow to create a surface with a microscopic combing effect, improving the cleanliness of the back surface and reducing defects.

[0024] The present invention can achieve the following effects:

[0025] The present invention provides a process method for improving the surface roughness of silicon wafers. Compared with the prior art, it has the advantages of convenient operation and good operation stability. It improves the surface roughness of the silicon wafer and the ability to adsorb sputtered metal. It improves the surface roughness and obtains silicon wafers with better flatness. Detailed embodiments

[0026] The technical solution of the invention will be further specifically described below through embodiments.

[0027] Embodiment: A process method for improving the surface roughness of silicon wafers, including the following operating steps:

[0028] First step: Roughly grind both sides of the sliced silicon wafers. The particle size of the abrasive powder in the rough grinding abrasive is 1000 mesh, and the ratio density is 1.30 ± 0.1 g / cm 3 ; The upper platen is fixed, the lower platen rotates at 30 ± 5 rpm / min, the carrier rotates around the axis at 15 ± 2.5 rpm / min, and the grinding pressure is 900 ± 50 kg. At the same time, add 3 - 7 L of suspension dispersant and 0.2 ± 0.05 L of defoamer, and the temperature of the cooling water for the platen is 23 ± 3 °C. 25 silicon wafers are processed in one batch, and the removal amount is 60 ± 5 μm.

[0029] Second step: Before chemical etching of the silicon wafers after rough grinding, the silicon wafers are cleaned with SC1 solution and pure water, and ultrasonic is used as an auxiliary.

[0030] Third step: Chemically etch by immersing the silicon wafers in an acidic solution or an alkaline solution to remove organic pollutants and metal impurities on the surface, making the surface smoother and more uniform.

[0031] The chemical etching uses a 45 - 55 wt.% KOH solution, the temperature is 75 - 95 °C, the etching removal amount is 25 - 35 μm, and the surface roughness of the silicon wafer is adjusted according to the removal amount of the alkaline etching. When performing chemical etching, NH40H solution or Na0H solution is used to replace the KOH solution for alkali washing to remove impurities, removing organic pollutants and metal impurities on the surface, making the surface smoother and more uniform.

[0032] When performing chemical etching, HF, HCl, HN03 or H2S04 are used for pickling to remove impurities, removing impurities and oxide layers on the surface of the silicon wafer, and improving the surface cleanliness and reaction activity.

[0033] Fourth step: After chemical etching, enter the QDR tank for cleaning. The flow rate of pure water for cleaning in the QDR tank is 20 - 30 L / min, and the cleaning time is 80 - 100 s.

[0034] Fifth step: Perform fine grinding. The particle size of the abrasive powder in the fine grinding abrasive is 1200 mesh, and the ratio density is 1.30 ± 0.1 g / cm 3 ; The upper platen is fixed, the lower platen rotates at 20 ± 5 rpm / min, the carrier rotates around the axis at 10 ± 2.5 rpm / min, and the grinding pressure is 400 ± 50 kg. At the same time, add 3 - 7 L of suspension dispersant and 0.2 ± 0.05 L of defoamer, and the temperature of the cooling water for the platen is 23 ± 3 °C. 25 silicon wafers are processed in one batch, and the removal amount is 5 ± 2 μm.

[0035] Before the chemical vapor deposition treatment, sand grains are evenly sprayed onto the back surface of the silicon wafer through a high-pressure gas stream to create a surface with a microscopic combing effect, improving the cleanliness of the back surface and reducing defects.

[0036] Step 6: Conduct chemical vapor deposition treatment to grow an oxide layer or a polysilicon film with a certain thickness on the back surface of the silicon wafer, prevent the phenomenon of self-doping, and achieve the "internal gettering" effect.

[0037] By combining the mechanical grinding method of coarse grinding plus fine grinding, the chemical etching method of alkali etching, and the back surface enhanced gettering treatment method, the surface roughness of the silicon wafer is significantly improved. The removal amount of coarse grinding is 60 μm, the removal amount of fine grinding is 5 μm, the removal amount of alkali etching is 30 μm, and the roughness Sa can be reduced to 245.4 nm.

[0038] In summary, the process method for improving the surface roughness of the silicon wafer has the advantages of convenient operation and good running stability. It improves the surface roughness of the silicon wafer and the ability to adsorb sputtered metal. The surface roughness is improved, and a silicon wafer with better flatness is obtained.

[0039] The above are only specific embodiments of the present invention, but the structural features of the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. A process for improving the surface roughness of a silicon wafer, characterized in that The steps are as follows: Step 1: Roughly grind both sides of the sliced ​​silicon wafer. The particle size of the grinding powder in the rough grinding liquid is 1000 mesh and the density is 1.30±0.1g / cm 3 ; The upper platen is fixed, the lower platen speed is 30±5rpm / min, the carrier revolution is 15±2.5rpm / min, and the grinding pressure is 900±50kg; Step 2: Before chemical etching, the roughly ground silicon wafer is cleaned with SC1 solution and pure water, assisted by ultrasound; Step 3: Soak the silicon wafer in an acidic or alkaline solution for chemical etching to remove organic pollutants and metal impurities on the surface, making the surface smoother and more uniform; Step 4: After chemical etching, enter the QDR tank for cleaning; Step 5: Fine grinding. The particle size of the grinding powder in the fine grinding liquid is 1200 mesh and the density is 1.30±0.1g / cm 3 ; The upper platen is fixed, the lower platen speed is 20±5rpm / min, the carrier revolution is 10±2.5rpm / min, and the grinding pressure is 400±50kg; Step 6: Perform chemical vapor deposition to grow an oxide layer or polysilicon film of a certain thickness on the back surface of the silicon wafer to prevent self-doping and achieve the "internal doping" effect.

2. The process for improving the surface roughness of a silicon wafer according to claim 1, characterized in that: 3-7L of suspending dispersant and 0.2±0.05L of defoaming agent were added during rough grinding and fine grinding, and the cooling water temperature of the fixed plate was 23±3℃; 25 silicon wafers were processed on one plate, the rough grinding removal amount was 60±5μm, and the fine grinding removal amount was 5±2μm.

3. The process for improving the surface roughness of a silicon wafer according to claim 1, characterized in that: Chemical etching uses 45-55wt.% KOH solution, temperature 75-95°C, etching removal amount 25-35μm, and the surface roughness of the silicon wafer is adjusted according to the removal amount of alkali etching.

4. The process for improving the surface roughness of a silicon wafer according to claim 3, characterized in that: During chemical etching, NH40H solution and NaOH solution are used to replace KOH solution for alkaline washing to remove organic pollutants and metal impurities on the surface, making the surface smoother and more uniform.

5. The process for improving the surface roughness of a silicon wafer according to claim 1, characterized in that: During chemical etching, HF, HCl, HN03 or H2S04 is used for pickling and decontamination to remove impurities and oxide layers on the surface of the silicon wafer, thereby improving surface cleanliness and reaction activity.

6. The process for improving the surface roughness of a silicon wafer according to claim 1, characterized in that: The pure water flow rate for QDR tank cleaning is 20-30L / min, and the cleaning time is 80-100s.

7. The process for improving the surface roughness of a silicon wafer according to claim 1, characterized in that: Before chemical vapor deposition, sand is evenly sprayed onto the back of the silicon wafer through a high-pressure airflow to create a surface with a microscopic combing effect, improve the cleanliness of the back surface and reduce defects.