Silicon wafer ultrafine particle cleaning optimization method

Abstract

The invention discloses a silicon wafer ultrafine particle cleaning optimization method, and particularly relates to the field of semiconductor cleaning processing, and the method comprises the following steps: S1, optimizing a cleaning process; s2, improving equipment and an operation mode; and S3, improving environmental conditions. According to the silicon wafer superfine particle cleaning optimization method, through the synergistic effect of optimizing the cleaning process, improving the equipment and the operation mode, improving the environmental condition and the like, the cleaning capacity of small particles smaller than 0.16 micron on the surface of the silicon wafer can be effectively improved, the silicon wafer cleaning effect and quality are improved, and the silicon wafer cleaning quality is improved. The high-precision requirement of the semiconductor manufacturing process is met, the product cleaning capacity is precisely improved by adopting proper cleaning liquid and proportion and controlling the cleaning time and temperature, and the expected high standard specification is achieved by using advanced cleaning equipment and optimizing and standardizing the operation process. A high-standard production environment is achieved by improving environmental conditions and combining with parameters such as the environment control temperature, humidity and pressure of a clean room.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor cleaning processing, and in particular to a method for optimizing the cleaning of ultrafine particles on silicon wafers. Background Art

[0002] At present, the semiconductor industry is booming. As the core basic material for integrated circuit manufacturing, the quality and performance of semiconductor silicon wafers directly determine the quality of the final chip products. In the complex process of semiconductor silicon wafer manufacturing, the cleaning process is like a lifeline that runs through the entire process, playing a key role in connecting the upper and lower levels. It is the core link to ensure the high-quality processing of silicon wafers. From the initial processing of silicon wafer raw materials to a series of high-precision processing steps such as cutting, grinding, polishing, etc., each step will inevitably introduce various pollutants on the surface of the silicon wafer, among which ultrafine particle pollution is particularly prominent. These ultrafine particles are extremely small, usually less than 0.16um. They are like "killers" hidden in the dark, posing a serious threat to the performance and reliability of silicon wafers. In the field of silicon manufacturing, with the rapid development of technology, process precision and requirements are constantly improving at an unprecedented rate. The integration of chips is getting higher and higher, and the feature size is getting smaller and smaller. This makes the requirements for the cleanliness of the silicon wafer surface reach an almost harsh level. Any tiny particle contamination may cause defects such as short circuit, open circuit, and leakage in the chip, thereby affecting the chip yield and performance stability. However, the silicon wafer cleaning process in the existing technology has exposed an obvious problem of insufficient cleaning ability when dealing with these ultrafine particles. Traditional cleaning methods, such as chemical cleaning and physical cleaning, have achieved certain results in dealing with larger particles, but they are unable to cope with ultrafine particles smaller than 0.16um and are difficult to meet the increasingly stringent process requirements. Summary of the Invention

[0003] The main purpose of the present invention is to provide an optimized method for cleaning ultrafine particles on silicon wafers, which can effectively solve the problem of insufficient cleaning ability when cleaning small particles less than 0.16um on the surface of silicon wafers.

[0004] To achieve the above object, the technical solution adopted by the present invention is:

[0005] A method for optimizing the cleaning of ultrafine particles from a silicon wafer comprises the following steps:

[0006] S1. Optimize the cleaning process: Use a cleaning solution with a specific ratio and control the cleaning time and temperature. The cleaning solution includes SC-1 cleaning solution, SC-2 cleaning solution and diluted hydrofluoric acid. The SC-1 cleaning solution is composed of NH4OH, H2O2 and DI-Water in a volume ratio of 1:1:5, the temperature is controlled at 70-80°C, and the cleaning time is about 10 minutes. The SC-2 cleaning solution is composed of HCl, H2O2 and DIW in a volume ratio of 1:1:6, the temperature is 70-80°C, and the cleaning time is about 10 minutes. The diluted hydrofluoric acid is a 0.5% to 1% HF solution, and the cleaning time is 1 to 2 minutes. After SC-1 cleaning, an ethanol aqueous solution is introduced, and the volume ratio of ethanol to pure water is 1:0.5 to 3;

[0007] S2. Improved equipment and operating methods: Use ultrasonic and megasonic cleaning equipment, optimize the design of the wafer box, and standardize the operating procedures. The wafer box has two sets of symmetrical avoidance openings at the fence positions on opposite sides, leaving only the frame that supports the silicon wafers. Specialized tools are used to remove and place the silicon wafers during operation. After cleaning, rinse with high-purity deionized water multiple times and dry by spin drying and nitrogen blowing.

[0008] S3. Improve environmental conditions: Control parameters such as temperature, humidity and pressure in the clean room to reduce particle sources in the environment. The cleanliness of the clean room reaches ISO1-3 level, the temperature is controlled at 20-25℃, the humidity is 40% to 60%, and the pressure is slightly higher than atmospheric pressure.

[0009] Preferably, the cleaning process is pre-water washing, SC-1 ultrasonic cleaning, ethanol dispersion treatment, DHF immersion, SC-2 cleaning, pure water overflow and nitrogen drying; wherein the SC-1 ultrasonic cleaning temperature is 68°C and is performed 3 times, and the DHF immersion is performed at room temperature for 10 minutes.

[0010] Preferably, in the step S3 of improving environmental conditions, the clean room needs to be cleaned and disinfected regularly, including but not limited to the floor, walls, ceiling and equipment surfaces.

[0011] Preferably, the equipment configuration includes a rotating holding net, an automatic cleaning filter and a PLC-controlled multi-parameter linkage device, and the rotating speed of the rotating holding net is 4 seconds per revolution.

[0012] Preferably, air purification equipment is installed in the clean room.

[0013] Preferably, the air purification equipment includes but is not limited to an air purifier and a fresh air system.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. The present invention can effectively improve the cleaning ability of small particles less than 0.16μm on the surface of silicon wafers through the synergistic effect of optimizing cleaning processes, improving equipment and operating methods, and improving environmental conditions, thereby improving the effect and quality of silicon wafer cleaning and meeting the high-precision requirements of semiconductor manufacturing processes.

[0016] 2. In the specific implementation process of the present invention, suitable cleaning liquids and proportions are used and the cleaning time and temperature are controlled to accurately improve the product cleaning ability. Advanced cleaning equipment is used and standardized operating procedures are optimized to achieve the expected high standards. By improving environmental conditions and combining the clean room environment to control parameters such as temperature, humidity and pressure, a high-standard production environment is achieved. These methods are coordinated and synergistic with each other to help improve the effect and quality of silicon wafer cleaning. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the overall flow chart of the present invention. DETAILED DESCRIPTION

[0018] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0019] like Figure 1 As shown, a method for optimizing the cleaning of ultrafine particles from a silicon wafer comprises the following steps:

[0020] S1. Optimize the cleaning process: Use appropriate cleaning fluids and proportions, and precisely improve the product's cleaning ability by controlling cleaning time and temperature;

[0021] SC-1 cleaning solution is composed of NH4OH, H2O2 and DI-Water in a certain ratio. NH4OH has oxidizing properties and can oxidize and decompose organic matter on the surface of silicon wafers into soluble small molecules. The strong oxidizing property of H2O2 can further enhance the removal ability of organic matter. At the same time, it oxidizes some metal impurities and forms complexes with the chelating agent, which facilitates subsequent cleaning and removal. The commonly used volume ratio is NH4OH:H2O2:DIW=1:1:5. The temperature is controlled at 70-80℃ and the cleaning time is about 10 minutes.

[0022] SC-2 cleaning solution is composed of HCl, H2O2 and DI-Water. HCl can adjust the pH value of the solution to make it acidic, which is beneficial for removing alkaline metal impurities on the surface of silicon wafers. H2O2 can react with metal impurities under acidic conditions, oxidizing them and dissolving them in the solution. A common ratio is HCl:H2O2:DI-Water = 1:1:6, the temperature is 70-80°C, and the cleaning time is about 10 minutes.

[0023] Diluted hydrofluoric acid (DHF) is used to remove the natural oxide layer on the surface of the silicon wafer, making the silicon wafer surface hydrogen-passivated, reducing the surface chemical reaction activity, and preventing particles from re-adsorbing. The HF in the DHF solution reacts with the oxide layer to form soluble fluoride, thereby removing the oxide layer. However, the concentration used must be strictly controlled, generally 0.5% to 1% HF solution, and the cleaning time should not be too long, usually about 1 to 2 minutes. After the SC-1 cleaning, an ethanol-water solution (ethanol to pure water volume ratio of 1:0.5 to 3) is introduced to utilize its low polarity to reduce the adsorption force between particles and the silicon wafer surface and improve dispersion. The cleaning time should be sufficient to ensure that the cleaning solution fully contacts the silicon wafer surface and works, but it should not be too long to avoid damaging the silicon wafer surface or causing new particle adsorption. For example, in SC-1 and SC-2 cleaning, a cleaning time of about 10 minutes is generally appropriate.

[0024] Secondly, temperature also has a significant impact on the cleaning effect. Appropriate temperature can increase the activity and diffusion rate of the cleaning solution and enhance the cleaning effect. However, too high a temperature may accelerate the volatilization and decomposition of the cleaning solution, affecting its stability. It may also cause the chemical reaction on the surface of the silicon wafer to be too intense, resulting in new particles or defects. Therefore, it is necessary to select a suitable temperature range according to different cleaning solutions and cleaning requirements. For example, the temperature of SC-1 cleaning solution is generally 70-80°C, and the temperature of SC-2 cleaning solution is 70-80°C.

[0025] S2. Improve equipment and operation methods: First, use advanced cleaning equipment, such as ultrasonic cleaning equipment and megasonic cleaning equipment. Ultrasonic cleaning equipment uses the impact force generated by the cavitation effect of ultrasonic waves in liquid to effectively remove particles on the surface of silicon wafers. The frequency and power of ultrasonic waves should be adjusted according to the specific conditions of the silicon wafers. Generally speaking, the higher the frequency, the better the removal effect of small particles, but too high a frequency may cause damage to the silicon wafers. For example, for smaller silicon wafers, higher frequency ultrasonic cleaning can be used, while for larger silicon wafers, the frequency needs to be appropriately reduced to avoid damage. Megasonic cleaning equipment has a higher frequency and a shorter wavelength, which can more effectively remove tiny particles without damaging the surface of the silicon wafer. Compared with traditional ultrasonic cleaning, megasonic cleaning can more accurately control the transfer of energy, reduce the potential risk of damage to silicon wafers, and can better penetrate narrow gaps and holes to remove particles in them;

[0026] Secondly, optimize the design of the wafer cassette. Traditional wafer cassettes may have some structural factors that are not conducive to cleaning. For example, the fence-like side frames will block the propagation of water flow and ultrasonic waves, affecting the cleaning effect. The wafer cassette can be improved. For example, two sets of avoidance openings can be symmetrically opened at the fence positions on the opposite sides of the wafer cassette, leaving only the frame that carries the wafers. This can reduce the wafer cassette's obstruction to water flow and ultrasonic waves, and improve the particle removal rate on the wafer surface.

[0027] Finally, standardize the operating procedures. When taking and placing silicon wafers, special tools should be used to avoid direct contact with the silicon wafer surface with hands, and prevent pollutants such as oil and sweat on human skin from adhering to the silicon wafer. Operators should operate in a clean environment and wear clean clothes, gloves and other protective equipment that meet the requirements. After cleaning, rinse with high-purity deionized water multiple times to remove residual cleaning fluid. When rinsing, pay attention to the direction and speed of the water flow to avoid water flow causing impact and damage to the silicon wafer surface. Use appropriate drying methods, such as spin drying, nitrogen drying, etc., to remove moisture from the silicon wafer surface as soon as possible to prevent water stains and particles from evaporating.

[0028] S3. Improve environmental conditions. First, the clean room environment needs to be controlled. The silicon wafer cleaning process needs to be carried out in an environment with a high cleanliness level, generally requiring the ISO1-3 cleanliness level standard to be met. The air in the clean room needs to be filtered through a high-efficiency filter to remove dust, microorganisms and other particulate matter in the air. At the same time, the temperature, humidity and pressure parameters in the clean room must be controlled. The temperature is generally controlled at 20-25°C, the humidity at 40% to 60%, and the pressure is kept slightly higher than atmospheric pressure to prevent backflow and contamination of external air.

[0029] Secondly, reduce the source of particles in the environment and regularly clean and disinfect the clean room, including the floor, walls, ceiling, equipment surface, etc., to reduce the breeding of dust and microorganisms. People and items entering the clean room must be strictly cleaned and purified, such as people changing clean clothes and shoes, wiping the surface of items or irradiating them with ultraviolet rays, etc. In addition, air purification equipment such as air purifiers and fresh air systems can be installed in the clean room to further improve the air quality.

[0030] Example 1: The practical application of the method for optimizing the cleaning of ultrafine particles from silicon wafers provided by the present invention is as follows:

[0031] S1. Optimize the cleaning process: first pre-wash with water to remove large particles on the surface of the silicon wafer, SC-1 ultrasonic cleaning, use SC-1 cleaning solution (NH4OH:H2O2:DIW=1:1:5), control the temperature at 70℃, perform 3 cleanings, each cleaning time is 10 minutes, ethanol dispersion treatment, introduce ethanol aqueous solution (ethanol to pure water volume ratio 1:1), treatment time is 5 minutes, DHF soaking, use 0.5% HF solution, soak at room temperature for 1 minute, SC-2 cleaning, use SC-2 cleaning solution (HCl:H2O2:DI-Water=1:1:6), control the temperature at 70℃, cleaning time is 10 minutes, pure water overflow, use high-purity deionized water for multiple overflow rinses, nitrogen spin drying, use nitrogen drying method to remove moisture from the surface of the silicon wafer.

[0032] S2. Improve equipment and operation methods: Use ultrasonic cleaning equipment with a frequency of 40kHz, adjust the power according to the size of the silicon wafer, optimize the silicon wafer box, open two sets of avoidance openings symmetrically at the fence positions on the opposite sides, the rotation speed of the rotating holding net is 4 seconds / revolution, and an automatic filter cleaning device and a PLC-controlled multi-parameter linkage device are installed.

[0033] S3. Improve environmental conditions: The cleanliness of the clean room reaches ISO level 1, the temperature is controlled at 22°C, the humidity is 50%, and the pressure is slightly higher than atmospheric pressure. The clean room is cleaned and disinfected regularly, and people and items entering the clean room are cleaned and purified in strict accordance with regulations.

[0034] Example 2: Based on Example 1, this example modifies some data in the steps of a method for optimizing the cleaning of ultrafine particles from a silicon wafer. The operation is as follows:

[0035] S1. Optimize the cleaning process: first pre-wash with water to remove large particles on the surface of the silicon wafer, SC-1 ultrasonic cleaning, use SC-1 cleaning solution (NOH:H2O2:DIW=1:1:5), control the temperature at 80°C, perform 3 cleanings, each cleaning time is 10 minutes, ethanol dispersion treatment, introduce ethanol aqueous solution (ethanol to pure water volume ratio 1:0.5), treatment time is 5 minutes, DHF soaking, use 1% HF solution, soak at room temperature for 2 minutes, SC-2 cleaning, use SC-2 cleaning solution (HCl:H2O2:DI-Water=1:1:6), control the temperature at 80°C, cleaning time is 10 minutes, pure water overflow, use high-purity deionized water for multiple overflow rinses, spin drying: use spin drying method to remove moisture from the surface of the silicon wafer, the speed is 1000 rpm.

[0036] S2. Improve equipment and operation methods: Use megasonic cleaning equipment with a frequency of 1MHz, adjust the power according to the size of the silicon wafer, optimize the silicon wafer box, open two sets of avoidance openings symmetrically at the fence positions on the opposite sides, the rotation speed of the rotating holding net is 4 seconds / revolution, and an automatic filter cleaning device and a PLC-controlled multi-parameter linkage device are installed.

[0037] S3. Improve environmental conditions: The cleanliness of the clean room reaches ISO level 2, the temperature is controlled at 25°C, the humidity is at 60%, and the pressure is slightly higher than atmospheric pressure. The clean room is cleaned and disinfected regularly, and people and items entering the clean room are cleaned and purified in strict accordance with regulations.

[0038] Example 3: Based on Example 1, this example modifies some data in the steps of a method for optimizing the cleaning of ultrafine particles from a silicon wafer. The operation is as follows:

[0039] S1. Optimize the cleaning process: first pre-wash with water to remove large particles on the surface of the silicon wafer, SC-1 ultrasonic cleaning, use SC-1 cleaning solution (NOH:H2O2:DIW=1:1:5), control the temperature at 75°C, perform 3 cleanings, each cleaning time is 10 minutes, ethanol dispersion treatment, introduce ethanol aqueous solution (ethanol to pure water volume ratio 1:3), treatment time is 5 minutes, DHF soaking, use 0.8% HF solution, soak at room temperature for 1.5 minutes, SC-2 cleaning, use SC-2 cleaning solution (HCl:H2O2:DI-Water=1:1:6), control the temperature at 75°C, cleaning time is 10 minutes, pure water overflow, use high-purity deionized water for multiple overflow rinses, nitrogen spin drying, use nitrogen drying method to remove moisture from the surface of the silicon wafer.

[0040] S2. Improve equipment and operation methods: Use ultrasonic cleaning equipment with a frequency of 60kHz, adjust the power according to the size of the silicon wafer, optimize the silicon wafer box, open two sets of avoidance openings symmetrically at the fence positions on the opposite sides, the rotation speed of the rotating holding net is 4 seconds / revolution, and an automatic filter cleaning device and a PLC-controlled multi-parameter linkage device are installed.

[0041] S3. Improve environmental conditions: The cleanliness of the clean room reaches ISO3 level, the temperature is controlled at 20℃, the humidity is at 40%, and the pressure is slightly higher than atmospheric pressure. The clean room is cleaned and disinfected regularly, and people and items entering the clean room are cleaned and purified in strict accordance with regulations.

[0042] The above examples demonstrate that the present invention's optimized method for cleaning ultrafine particles from silicon wafers effectively improves the removal of particles smaller than 0.16 μm from silicon wafer surfaces, significantly reducing the amount of residual particles on the wafer surface after cleaning, thus meeting the high-precision requirements of semiconductor manufacturing processes. In practical applications, the cleaning process parameters, equipment configuration, and environmental conditions can be appropriately adjusted based on factors such as the specific silicon wafer size and cleaning requirements to achieve optimal cleaning results.

[0043] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for optimizing the cleaning of ultrafine particles from silicon wafers, characterized in that: The following steps are involved: S1. Optimize the cleaning process: Use a cleaning solution with a specific ratio and control the cleaning time and temperature. The cleaning solution includes SC-1 cleaning solution, SC-2 cleaning solution and diluted hydrofluoric acid. The SC-1 cleaning solution is composed of NH4OH, H2O2 and DI-Water in a volume ratio of 1:1:5, the temperature is controlled at 70-80°C, and the cleaning time is about 10 minutes. The SC-2 cleaning solution is composed of HCl, H2O2 and DIW in a volume ratio of 1:1:6, the temperature is 70-80°C, and the cleaning time is about 10 minutes. The diluted hydrofluoric acid is a 0.5% to 1% HF solution, and the cleaning time is 1 to 2 minutes. After SC-1 cleaning, an ethanol aqueous solution is introduced, and the volume ratio of ethanol to pure water is 1:0.5 to 3; S2. Improved equipment and operating methods: Use ultrasonic and megasonic cleaning equipment, optimize the design of the wafer box, and standardize the operating procedures. The wafer box has two sets of symmetrical avoidance openings at the fence positions on opposite sides, leaving only the frame that supports the silicon wafers. Specialized tools are used to remove and place the silicon wafers during operation. After cleaning, rinse with high-purity deionized water multiple times and dry by spin drying and nitrogen blowing. S3. Improve environmental conditions: Control the temperature, humidity and pressure parameters of the clean room to reduce the particle sources in the environment. The cleanliness of the clean room reaches ISO1-3 level, the temperature is controlled at 20-25℃, the humidity is 40% to 60%, and the pressure is slightly higher than atmospheric pressure.

2. The method for optimizing cleaning of ultrafine particles from silicon wafers according to claim 1, wherein: The cleaning process includes pre-water washing, SC-1 ultrasonic cleaning, ethanol dispersion treatment, DHF immersion, SC-2 cleaning, pure water overflow and nitrogen drying; the SC-1 ultrasonic cleaning temperature is 68°C and is performed 3 times, and the DHF immersion is performed at room temperature for 10 minutes.

3. The method for optimizing cleaning of ultrafine particles from silicon wafers according to claim 1, wherein: In the step S3 of improving environmental conditions, the clean room needs to be cleaned and disinfected regularly, including but not limited to the floor, walls, ceiling and equipment surfaces.

4. The method for optimizing cleaning of ultrafine particles from silicon wafers according to claim 1, wherein: The equipment configuration includes a rotating holding net, an automatic cleaning filter and a PLC-controlled multi-parameter linkage device, and the rotating speed of the rotating holding net is 4 seconds per revolution.

5. The method for optimizing cleaning of ultrafine particles from silicon wafers according to claim 1, wherein: Air purification equipment is installed in the clean room.

6. The method for optimizing cleaning of ultrafine particles from silicon wafers according to claim 5, characterized in that: The air purification equipment includes but is not limited to an air purifier and a fresh air system.

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