A cleaning and drying process for silicon wafer packaging cassettes

Abstract

The application provides a silicon wafer packaging tray cleaning and drying process, which comprises the following steps: loading a packaging tray on a pure water tank and immersing the packaging tray in the pure water tank, transferring the packaging tray to a pre-cleaning tank for pre-cleaning, and then transferring the packaging tray to a cleaning tank for cleaning; moving the cleaned packaging tray to a first treatment position for drying treatment; transferring the dried packaging tray to a second treatment position for first stationary storage, then immersing the packaging tray in a constant-temperature nitrogen tank for second stationary treatment, taking out the packaging tray, and then moving the packaging tray to the second treatment position for third stationary treatment; and the treatment is completed. The application has the beneficial effect that the drying and stationary treatment of the packaging tray comprises three parts, namely, hot air drying and heat dissipation and flow guide, first environment stationary and cooling, and N2 tank drying, so that the packaging tray cleaned by the method is fully dried.

Description

Technical Field

[0001] This invention belongs to the field of finished storage and packaging of silicon single crystal polished wafers, and in particular relates to a cleaning and drying process for silicon wafer packaging boxes. Background Technology

[0002] Monocrystalline silicon wafers are crucial substrate materials in integrated circuit (IC) manufacturing. The surface quality of polished wafers has a significant impact on the device performance of integrated circuits, including factors such as surface flatness, particle size, roughness, metallic impurities, and product appearance. Parameters directly related to polished wafer quality during semiconductor material processing are the focus of research and control in process technology and quality management. However, research on indirect factors affecting polished wafer quality, such as production plant environment, tooling, packaging, and transportation, is relatively limited. In recent years, the industry has discovered that factors such as particulate levels in the plant environment, metal ions in the workshop atmosphere, vacuum packaging processes, wafer cassettes, and packaging materials also significantly influence wafer quality.

[0003] As the industry develops, the linewidth of integrated circuit processes is getting smaller and smaller. Currently, 28nm, 14nm, and 7nm process technologies have begun mass production, which places higher demands on the processing technology of polished wafers. In addition to higher requirements for the polishing technology, maintaining product quality at the small particle size level also places stricter requirements on product packaging and transportation processes. Clean packaging of products also places higher demands on the silicon wafer holding device - the silicon wafer cassette. Therefore, how to ensure the cleanliness of the polished wafer cassette and effectively control the increase of small-sized particles is the focus of this invention patent.

[0004] In large-scale production processes, the tablets and cassettes are not used immediately after cleaning. One reason is that the tablets and cassettes are not truly dry after cleaning (generally, only the surface is free of water droplets, but moisture may remain inside the tablets and cassettes, or the cooling process during the drying process may be inappropriate, leading to a so-called "dampness" phenomenon after packaging). Another reason is that in large-scale production, due to factors such as the capacity, process, and material preparation of equipment in upstream and downstream processes, it is difficult to achieve seamless connection between related materials in the preparation stage. Therefore, the impact of cleaning, drying, and post-drying resting methods on product quality of the tablets and cassettes is given due attention. Summary of the Invention

[0005] The problem to be solved by the present invention is to provide a cleaning and drying process for silicon wafer packaging boxes, which effectively solves the problem in the prior art that the wafer boxes are not truly dried after cleaning, and that packaging cannot be carried out directly due to factors such as the capacity, process and material preparation of upstream and downstream equipment in large-scale production, and that impurities will adhere during the waiting period.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a cleaning and drying process for silicon wafer packaging boxes, comprising:

[0007] The packaging film box is loaded and placed in a pure water tank for immersion, then transferred to a pre-cleaning tank for pre-cleaning, and then into a cleaning tank for cleaning.

[0008] After cleaning, the packaged tablets are moved to the first processing area for drying.

[0009] After drying, the packaged tablets are transferred to the second processing area for initial static storage, and then placed in a constant temperature nitrogen cabinet for a second static treatment. After being removed, they are subjected to a third static treatment at the second processing area, and the processing is completed.

[0010] Furthermore, the pre-cleaning tank is equipped with spray holes to spray and clean the packaging box, and the cleaning time is 10-15 minutes.

[0011] Furthermore, the cleaning tank is an ultrasonic cleaning tank with an ultrasonic power of 25-30KHz, used for ultrasonic cleaning of the packaging cassette.

[0012] Furthermore, the cleaning tank is also equipped with a heating function to maintain the temperature of the cleaning water at 40-60℃ when cleaning the packaging box.

[0013] Furthermore, the drying process involves blowing the packaging box with air at 45°C-65°C from different angles.

[0014] Furthermore, the second treatment area is a primary microenvironment, and the packaging tablets are left to stand in the second treatment area for 30-60 minutes at a time.

[0015] Furthermore, the lid and body of the packaging box are not tightly sealed when the box is left to stand for one time at the second processing point.

[0016] Furthermore, the packaging box is left to stand for 6-10 hours in the constant temperature nitrogen cabinet.

[0017] Furthermore, the second treatment involves three settling periods of 30-240 minutes.

[0018] Furthermore, the pure water in the pure water tank, the pre-cleaning tank, and the cleaning tank is all filtered ultrapure water.

[0019] By adopting the above technical solution, the packaging box for silicon wafers cleaned with ultrapure water, through the rational design of the cleaning and drying processes, effectively controls small particles smaller than 28nm on the surface of the packaged polished wafers.

[0020] Using the above technical solution, traditional drying methods include infrared baking and centrifugal rotary drying. The drying and settling of the packaging boxes used in this invention includes three parts: first, hot air drying and heat dissipation; second, primary environmental settling and cooling; and third, N2 cabinet drying. The packaging boxes cleaned in this way ensure that the extremely small droplets on the surface are fully dried. Attached Figure Description

[0021] Figure 1 This is an embodiment of the cleaning and drying process for silicon wafer packaging boxes according to an invention. Example 1 shows the increase in particle size.

[0022] Figure 2 This is an embodiment of the cleaning and drying process for silicon wafer packaging boxes according to an embodiment of the present invention. (Example 2: Particle increase) Detailed Implementation

[0023] The present invention will be further described below with reference to embodiments and accompanying drawings:

[0024] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments and comparative examples only and are not intended to limit the scope of protection of this invention. It should be specifically noted that the same organic structure may have multiple names, and all such structures fall within the scope of this patent.

[0025] Unless otherwise defined, the raw materials, reagents, etc. in the following examples and comparative examples can be obtained commercially or prepared according to reported methods.

[0026] Current tablet / carton cleaning processes can generally control relatively large-diameter particles, such as those with diameters of 0.5µm, 0.3µm, and 0.2µm, with an increase of no more than two particles before and after packaging. However, they cannot meet the requirements for controlling the size of small-diameter particles, such as those with diameters of 0.12µm, 0.09µm, 0.065µm, 0.055µm, 0.0045µm, 0.037µm, 0.028µm, and 0.019µm. The increase in large particles may be due to factors such as adsorption and cleanliness, but the increase in small particles involves factors beyond adsorption, vibration, and static electricity, including surface micro-adsorption, temperature, and humidity. Therefore, the requirements for packaged tablets / cartons are becoming increasingly stringent.

[0027] A cleaning and drying process for silicon wafer packaging cassettes includes:

[0028] S1: The packaged tablets are loaded and immersed in a pure water tank, then transferred to a pre-cleaning tank for pre-cleaning, and finally into a cleaning tank for cleaning; among these steps...

[0029] The water in the pure water tank is filtered ultrapure water. The ultrapure water supplied by the system (with a resistivity greater than 18.2 MΩ·cm) is further filtered and purified by installing a pure water filter element capable of filtering 0.1 μm particles onto the ultrapure water inlet pipe.

[0030] The cleaning water in the pre-cleaning tank is also filtered ultrapure water, and spray holes are opened in the pre-cleaning tank. The spray holes are located on the left and right sides inside the pre-cleaning tank. The number of spray holes is unlimited, but they are generally set in two rows to evenly spray the inner and outer surfaces of the packaged tablets for pre-cleaning. After being sprayed onto the surface of the tablets, the water is quickly discharged. In some feasible embodiments, ultrapure water at room temperature is used to pre-clean the inner and outer surfaces of the tablets from all directions through the spray holes.

[0031] In some feasible embodiments, the packaging tablets are cleaned in the pre-cleaning tank for 10-15 minutes to remove large particles and floating dust from the inner and outer surfaces of the tablets. Preferably, the cleaning time is 12-14 minutes.

[0032] After pre-cleaning, the packaging box is moved to the cleaning tank, which is an ultrasonic cleaning tank. Generally, the ultrasonic power is set to 25-30KHz, preferably 27, 28, or 29KHz, to perform ultrasonic cleaning on the packaging box.

[0033] In some feasible embodiments, the cleaning tank is equipped with a heating function, and the temperature of the ultrapure water is controlled between 40-60°C, preferably between 45-55°C, and more preferably between 48, 49, 50, 51, and 52°C.

[0034] S2: The cleaned packaging tablets are moved to the first processing station for drying. The first processing station should be equipped with an FFU high-efficiency filter and should meet the requirements of slight positive pressure. During the drying process, the air used in drying the packaging tablets needs to be filtered and purified. Specifically, a gas filter element with a 0.1um particle filtration capability can be installed at the front end of each drying station to further control the quality of the compressed air used for drying.

[0035] Hot air is blown onto the tablets from different angles through vents to achieve drying. The heat dissipation method and flow direction of the hot air have a certain impact on the cleaning effect and dryness of the tablets. Support rods can be used to support the packaged tablets and control the airflow direction through the support rods, which can effectively control the impact of turbulent heat radiation flow on the drying and cleaning effects.

[0036] S3: After drying, the packaged tablets are transferred to the second processing area for initial static storage, then placed in a constant-temperature nitrogen chamber for a second static treatment. After being removed, they undergo a third static treatment at the second processing area, completing the process.

[0037] The second treatment area is a Class I microenvironment, which in actual use is a Class I cleanroom with a high-efficiency FFU microenvironment. The packaging tablets are left to stand in the second treatment area for 30-60 minutes, preferably 30-40 minutes, and even more preferably 30 minutes.

[0038] When the packaging box is left to stand for the first time in the second processing stage, the lid and the box body are not tightly sealed. Generally, the lid is placed loosely on the box body, not tightly sealed. The part of the top of the box body that is not covered is about 1 / 5 to 1 / 10. The preferred method is to place it at an angle to the edge of the box body to maintain the stability of the box body and the lid.

[0039] Subsequently, the packaging boxes are placed in a constant temperature nitrogen cabinet at 35±5℃ for a second settling time of no more than 6-10 hours. If the settling time exceeds 12 hours, they need to be cleaned again.

[0040] Finally, the packaging boxes are removed from the constant temperature nitrogen cabinet at 35±5℃ and placed in the second treatment area for at least 30 minutes before being packaged and used within 4 hours.

[0041] In some feasible embodiments, the pure water filter element is installed at the rear end of the ultrapure water return line and before the inlet line of the cleaning tank of the tablet washing machine, so that the level of impurity particles in the ultrapure water can be further controlled.

[0042] The following are some specific examples:

[0043] Example 1

[0044] Select 8 disc boxes, containing 100 polishing discs.

[0045] S1: The packaged tablets are loaded and immersed in a pure water tank, then transferred to a pre-cleaning tank for pre-cleaning, and finally into a cleaning tank for cleaning; among these steps...

[0046] The water in the pure water tank is filtered ultrapure water. The ultrapure water supplied by the system (with a resistivity greater than 18.2 MΩ·cm) is further filtered and purified by installing a pure water filter element capable of filtering 0.1 μm particles onto the ultrapure water inlet pipe.

[0047] The cleaning water in the pre-cleaning tank is also filtered ultrapure water, the same as that in the pure water tank, but it is not the filtered ultrapure water that has already soaked the tablets. Spray holes are provided in the pre-cleaning tank, and the spray holes are located on the left and right sides inside the pre-cleaning tank. The ultrapure water at room temperature is used to pre-clean the inner and outer surfaces of the tablets from all directions through the spray holes.

[0048] The tablet boxes are cleaned in the pre-cleaning tank for 13 minutes to remove large particles and dust from the inner and outer surfaces of the boxes.

[0049] After pre-cleaning, the packaged tablets are moved into the cleaning tank, which is an ultrasonic cleaning tank with an ultrasonic power set to 25 kHz.

[0050] The cleaning tank is equipped with a heating function, and the temperature of the ultrapure water is controlled at 50℃ during use.

[0051] S2: The cleaned packaging tablets are moved to the first processing station for drying. The environment of the first processing station is a normal environment and no special settings are required. During the drying process, the air used in the packaging process needs to be filtered and purified. Specifically, a gas filter element with 0.1um particle filtering capability is installed at the front end of each drying station to further control the quality of the compressed air used for drying.

[0052] Hot air is blown onto the tablets from different angles through vents to achieve drying. The heat dissipation method and flow direction of the hot air have a certain impact on the cleaning effect and dryness of the tablets. Support rods can be used to support the packaged tablets and control the airflow direction through the support rods, which can effectively control the impact of turbulent heat radiation flow on the drying and cleaning effects.

[0053] S3: After drying, the packaged tablets are transferred to a constant temperature nitrogen cabinet for static treatment. The treatment is now complete.

[0054] in,

[0055] The packaging tablets were placed in a nitrogen chamber at 35±5℃ for 8 hours.

[0056] Finally, the packaged tablets were removed from the nitrogen chamber at 35±5℃ for testing.

[0057] Generally, when measuring dryness, the first step is to check for water droplets. If no water droplets remain on the surface, a humidity indicator card is placed inside the wafer cassette for further confirmation. However, extensive practical experience shows that the drying effect of the wafer cassette and the methods for measuring it are not easy to quantify. More often, packaging experiments are required for confirmation. A qualified wafer cassette must not increase the number of large particles or small particles on the silicon wafer surface, must not increase "time haze" (TDH) on the silicon wafer surface, and must not increase the number of metal ions on the silicon wafer surface.

[0058] according to Figure 1 As shown, the amount of small and large particles on the surface of the packaging box has increased significantly.

[0059] Example 2

[0060] S1: The packaged tablets are loaded and immersed in a pure water tank, then transferred to a pre-cleaning tank for pre-cleaning, and finally into a cleaning tank for cleaning; among these steps...

[0061] The water in the pure water tank is filtered ultrapure water. The ultrapure water supplied by the system (with a resistivity greater than 18.2 MΩ·cm) is further filtered and purified by installing a pure water filter element capable of filtering 0.1 μm particles onto the ultrapure water inlet pipe.

[0062] The cleaning water in the pre-cleaning tank is also filtered ultrapure water, the same as that in the pure water tank, but it is not the filtered ultrapure water that has already soaked the tablets. Spray holes are provided in the pre-cleaning tank, and the spray holes are located on the left and right sides inside the pre-cleaning tank. The ultrapure water at room temperature is used to pre-clean the inner and outer surfaces of the tablets from all directions through the spray holes.

[0063] The tablet boxes are cleaned in the pre-cleaning tank for 13 minutes to remove large particles and dust from the inner and outer surfaces of the boxes.

[0064] After pre-cleaning, the packaged tablets are moved into the cleaning tank, which is an ultrasonic cleaning tank with an ultrasonic power set to 25 kHz.

[0065] The cleaning tank is equipped with a heating function, and the temperature of the ultrapure water is controlled at 50℃ during use.

[0066] S2: The cleaned packaging tablets are moved to the first processing station for drying. The environment of the first processing station is a normal environment and no special settings are required. During the drying process, the air used in the packaging process needs to be filtered and purified. Specifically, a gas filter element with 0.1um particle filtering capability is installed at the front end of each drying station to further control the quality of the compressed air used for drying.

[0067] Hot air is blown onto the tablets from different angles through vents to achieve drying. The heat dissipation method and flow direction of the hot air have a certain impact on the cleaning effect and dryness of the tablets. Support rods can be used to support the packaged tablets and control the airflow direction through the support rods, which can effectively control the impact of turbulent heat radiation flow on the drying and cleaning effects.

[0068] S3: After drying, the packaged tablets are transferred to the second processing area for initial static storage, then placed in a constant-temperature nitrogen chamber for a second static treatment. After being removed, they undergo a third static treatment at the second processing area, completing the process.

[0069] The second treatment area is a Class I microenvironment, which in actual use is a Class I cleanroom with a high-efficiency FFU microenvironment. The packaging tablets are left to stand for 30 minutes at the second treatment area.

[0070] When the packaging box is left to stand in the second processing stage, the lid and the box body are not tightly sealed. The lid is placed loosely on the box body, not tightly sealed. About 1 / 5 of the top of the box body is not covered and is slightly offset from the edge of the box body. This natural placement method maintains the stability of the box body and the lid.

[0071] Subsequently, the packaging boxes were placed in a nitrogen cabinet at 35±5℃ for a second settling period of 8 hours.

[0072] Finally, the packaged tablets were removed from the nitrogen chamber at 35±5℃ and left to stand in the second treatment area for 120 minutes before testing.

[0073] Generally, when measuring dryness, the first step is to check for water droplets. If no water droplets remain on the surface, a humidity indicator card is placed inside the wafer cassette for further confirmation. However, extensive practical experience shows that the drying effect of the wafer cassette and the methods for measuring it are not easy to quantify. More often, packaging experiments are required for confirmation. A qualified wafer cassette must not increase the number of large particles or small particles on the silicon wafer surface, must not increase "time haze" (TDH) on the silicon wafer surface, and must not increase the number of metal ions on the silicon wafer surface.

[0074] according to Figure 2 As shown, the increase in both small and large particles on the surface of the packaging box is compared to... Figure 1 Significantly reduced.

[0075] The packaging box drying and settling process used in this invention consists of three parts: first, hot air drying and heat dissipation; second, primary environmental settling and cooling; and third, constant temperature nitrogen cabinet drying. This method of cleaning packaging boxes not only ensures the thorough drying of extremely small droplets on the surface, but also controls the disturbance of hot air during the heat dissipation process, effectively protecting the clean environment and ensuring the cleanliness of the box surface.

[0076] It should be noted that the above content is merely an embodiment of the present invention. Any modifications and alterations made by those skilled in the art based on the main ideas and related content of the present invention should also fall within the scope of protection of the claims of the present invention. Furthermore, the technical terms and other materials involved in the present invention are only for clearly illustrating the advantages and effects of the present invention and should not be considered as limitations on the innovativeness of the present invention. The above embodiments are a partial description of the practical application effects of the present invention, and these embodiments are not intended to limit the patent scope of the present invention. All improvements and substitutions made by those skilled in the art based on the present invention fall within the scope of protection of the present invention.

Claims

1. A cleaning and drying process for silicon wafer packaging cassettes, comprising: The packaging film box is loaded and placed in a pure water tank for immersion, then transferred to a pre-cleaning tank for pre-cleaning, and then into a cleaning tank for cleaning. After cleaning, the packaged tablets are moved to the first processing area for drying. After drying, the packaged tablets are transferred to the second processing area for initial static storage, and then placed in a constant temperature nitrogen cabinet for a second static treatment. After being taken out, they are subjected to a third static treatment at the second processing area, and the processing is completed. The second treatment area is a primary microenvironment, and the packaging tablets are left to stand in the second treatment area for 30-60 minutes at a time. The lid and body of the packaging box are staggered during the first static placement at the second processing point.

2. The cleaning and drying process for a silicon wafer packaging cassette according to claim 1, comprising: The pre-cleaning tank is equipped with spray holes to spray and clean the packaging boxes for 10-15 minutes.

3. A cleaning and drying process for a silicon wafer packaging cassette according to claim 1 or 2, comprising: The cleaning tank is an ultrasonic cleaning tank with an ultrasonic power of 25-30KHz, used for ultrasonic cleaning of the packaging boxes.

4. The cleaning and drying process for a silicon wafer packaging cassette according to claim 3, comprising: The cleaning tank is also equipped with a heating function to maintain the temperature of the cleaning water at 40-60℃ when cleaning the packaging box.

5. The cleaning and drying process for a silicon wafer packaging cassette according to claim 1, comprising: The drying process involves blowing hot air at 45°C-65°C onto the packaging box from different angles.

6. The cleaning and drying process for a silicon wafer packaging cassette according to claim 1, comprising: The packaging tablets were left to stand for 6-10 hours in the constant temperature nitrogen cabinet.

7. The cleaning and drying process for a silicon wafer packaging cassette according to claim 1, comprising: The second treatment involves three settling periods of 30-150 minutes each.

8. The cleaning and drying process for a silicon wafer packaging cassette according to claim 1, comprising: The pure water in the pure water tank, pre-cleaning tank, and cleaning tank is all filtered ultrapure water.

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