A method for solving wafer annealing boat mark

Abstract

This invention discloses a method for solving silicon wafer annealing boat imprinting, comprising the following steps: 1. Starting the annealing furnace, introducing a protective gas, and heating to 680~720℃; 2. Using a wafer shaker, shaking the reference surface of the cleaned silicon wafer to the top, using an automatic wafer pusher to pour the silicon wafer from the wafer cassette into a quartz boat, placing the quartz boat in the constant temperature zone of the annealing furnace at 680~720℃ for heat preservation, and allowing the silicon wafer to cool naturally after being removed from the furnace, completing the first annealing of the silicon wafer, and then using an automatic wafer pusher... The process involves four steps: 1. Transferring the silicon wafer from the quartz boat back into the wafer cassette; 2. Cleaning and drying the silicon wafer using a wafer cleaning machine; 3. Rotating the silicon wafer 20-40° relative to the initial annealing temperature using a wafer shaker, then transferring the rotated wafer to the slot in the quartz boat using an automatic wafer pusher. The quartz boat is then placed in the constant temperature zone of the annealing furnace at 630-670°C for holding. After removal from the furnace and natural cooling, the silicon wafer undergoes secondary annealing. Finally, the silicon wafer is transferred from the quartz boat back into the wafer cassette using the automatic wafer pusher. This invention effectively reduces the occurrence of annealing boat marking defects.

Description

Technical Field

[0001] This invention belongs to the field of single-crystal silicon wafer technology, specifically a method for solving the problem of boat printing during silicon wafer annealing. Background Technology

[0002] With the development of the semiconductor industry, the rapid Moore's Law-like growth in the application of large-scale integrated circuits has driven the widespread use of single-crystal wafers as epitaxial substrate materials. The wafer processing and production of silicon wafers typically involves cutting, grinding, chemical etching, annealing, and polishing in sequence to obtain the finished product. Silicon wafer annealing is a crucial process in silicon wafer manufacturing. Its purpose is to eliminate the influence of oxygen donors within the silicon wafer, or to remove concentric surface defects formed during single-crystal growth. Quartz boats are widely used in the annealing process. During the annealing process, the quartz boat grooves come into contact with the silicon wafer surface, inevitably forming annealing boat marks. Annealing boat marks are a type of wafer appearance defect, difficult to observe after annealing, but become prominent during the subsequent back-sealing (AP) process, and are very difficult to eliminate. Current technologies result in a high rate and significant loss due to annealing boat marks, and there is currently no effective method to resolve this issue. Summary of the Invention

[0003] To address the aforementioned problems, this invention proposes a method for resolving annealing boat imprints on silicon wafers, which can effectively reduce the occurrence of annealing boat imprint defects.

[0004] This invention is achieved through the following technical solution: A method for solving the problem of wafer annealing boat imprints specifically includes the following steps: Step 1: Start the annealing furnace, introduce protective gas, raise the temperature to 680~720℃, and maintain a stable temperature; Step 2: Use a wafer shaker to shake the reference surface of the cleaned silicon wafer to the top. Use an automatic wafer pusher to pour the silicon wafer from the wafer cassette into the slot of the quartz boat. Place the quartz boat in the constant temperature zone of the annealing furnace at 680~720℃ for 10~20 minutes. After the silicon wafer is removed from the furnace, let it cool naturally for 10~20 minutes to complete the first annealing of the silicon wafer. Then use the automatic wafer pusher to pour the silicon wafer back from the quartz boat into the wafer cassette. Step 3: After one annealing, the silicon wafers are cleaned using a silicon wafer cleaning machine and then spun dry. Step 4: After the silicon wafer has undergone one annealing and cleaning, use a wafer shaker to rotate the silicon wafer 20-40° relative to the angle during the first annealing. Then, use an automatic wafer pusher to transfer the rotated silicon wafer to the slot of the quartz boat. Place the quartz boat in the constant temperature zone of the annealing furnace at 630-670°C and hold for 10-20 minutes. Remove from the furnace and allow to cool naturally to complete the second annealing of the silicon wafer. Finally, use the automatic wafer pusher to transfer the silicon wafer from the quartz boat back into the wafer cassette.

[0005] Furthermore, the protective gas introduced in step one is nitrogen.

[0006] Furthermore, the annealing conditions in step two are to maintain the temperature at 700°C in the constant temperature zone of the annealing furnace for 10 minutes.

[0007] Furthermore, the cleaning method in step three is as follows: the silicon wafer is sequentially cleaned in the cleaning machine by passing through QDR-cleaning solution-QDR.

[0008] Furthermore, the cleaning solution is an acidic cleaning solution with a solution temperature of 23~28℃. The solution components are HF, HCl, H2O2, and DIW, and their ratio is HF:HCl:H2O2:DIW=1:1:1.5:16~1:1.5:3:16.

[0009] Furthermore, the annealing conditions in step four are to maintain the temperature at 650°C for 10 minutes in the constant temperature zone of the annealing furnace.

[0010] The beneficial effects of this invention are as follows: (1) Compared with conventional annealing, the present invention uses a wafer shaker to rotate the silicon wafer after one annealing and cleaning by 20~40° relative to the angle during the first annealing. The relative rotation of the silicon wafer can eliminate the influence of the quartz boat tooth groove on the silicon wafer during the first annealing, reduce the risk of quartz boat imprint defects, and significantly improve the yield of silicon wafers. (2) The present invention adopts a two-stage annealing process and cleans between the two annealing stages, which can ensure the cleanliness of the silicon wafer and reduce the risk of introducing impurities into the silicon wafer. Attached Figure Description

[0011] Figure 1 This is a flowchart illustrating the overall process flow of the present invention. Figure 2 This is a defect diagram for quartz boat printing using existing processes. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0013] Example 1 1. Start the annealing furnace, introduce inert gas, raise the temperature to 700℃, and maintain a stable temperature; 2. After cleaning, the silicon wafers are shaken to the top by a wafer shaker. The wafers are then poured from the wafer cassette into the slot of the quartz boat using an automatic wafer pusher. The quartz boat is placed in the annealing furnace at a constant temperature of 700°C for 10 minutes. After the wafers are removed from the furnace, they are allowed to cool naturally for 15 minutes to complete the first annealing of the silicon wafers. The wafers are then poured back from the quartz boat into the wafer cassette using an automatic wafer pusher. The wafer shaker and automatic wafer pusher used are existing devices. 3. After one annealing, the silicon wafers are cleaned in a silicon wafer cleaning machine using QDR-cleaning fluid-QDR cleaning. 4. After the first annealing and cleaning, the silicon wafer is rotated 30° relative to the first annealing using a wafer shaker. The rotated silicon wafer is then transferred to a quartz boat using an automatic wafer pusher. The quartz boat is placed in the constant temperature zone of the annealing furnace at 650°C for 10 minutes, then removed from the furnace and allowed to cool naturally.

[0014] Example 2 1. Start the annealing furnace, introduce inert gas, raise the temperature to 700℃, and maintain a stable temperature; 2. After cleaning, the silicon wafers are shaken to the top by a wafer shaker. The wafers are then poured from the wafer cassette into a quartz boat using an automatic wafer pusher. The quartz boat is placed in the annealing furnace at a constant temperature of 700°C for 20 minutes. After the wafers are removed from the furnace, they are allowed to cool naturally for 15 minutes. Then, the wafers are poured back from the quartz boat into the wafer cassette using an automatic wafer pusher. 3. After one annealing, the silicon wafers are cleaned in a silicon wafer cleaning machine using QDR-cleaning fluid-QDR cleaning. 4. After the first annealing and cleaning, the silicon wafer is rotated 30° relative to the first annealing using a wafer shaker. The rotated silicon wafer is then transferred to a quartz boat using an automatic wafer pusher. The quartz boat is placed in the constant temperature zone of the annealing furnace at 650°C for 20 minutes, then removed from the furnace and allowed to cool naturally.

[0015] Comparative Example 1 1. Start the annealing furnace, introduce inert gas, and raise the temperature.

[0016] 2. After cleaning, the silicon wafers are shaken to the top by a wafer shaker. The wafers are then poured from the wafer cassette into a quartz boat using an automatic wafer pusher. The quartz boat is placed in the annealing furnace and kept at a constant temperature of 700°C for 20 minutes. After the wafers are removed from the furnace, they are allowed to cool naturally for 15 minutes.

[0017] In Examples 1-2 and Comparative Example 1, 1000 silicon wafers were processed. After back-sealing AP processing, the wafers were manually inspected, and the proportion of silicon wafers with quartz boat printing defects was calculated. The results are shown in the table below.

[0018] Table 1. Defect Ratio of Quartz Boat Printing As can be seen from the table, compared with conventional annealing (Comparative Example 1), the proportion of quartz boat imprint defects in Examples 1 and 2 is significantly reduced, proving that the relative rotation between the two annealing processes of the silicon wafer in this invention can eliminate the influence of the quartz boat tooth groove on the silicon wafer during the first annealing, and significantly reduce the risk of quartz boat imprint defects.

[0019] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope. All such changes and modifications fall within the scope of the present invention as claimed, which is defined by the appended claims and their equivalents.

Claims

1. A method for solving the problem of boat markings during silicon wafer annealing, characterized in that: Specifically, the steps include: Step 1: Start the annealing furnace, introduce protective gas, raise the temperature to 680~720℃, and maintain a stable temperature; Step 2: Use a wafer shaker to shake the reference surface of the cleaned silicon wafer to the top. Use an automatic wafer pusher to pour the silicon wafer from the wafer cassette into the slot of the quartz boat. Place the quartz boat in the constant temperature zone of the annealing furnace at 680~720℃ for 10~20 minutes. After the silicon wafer is removed from the furnace, let it cool naturally for 10~20 minutes to complete the first annealing of the silicon wafer. Then use the automatic wafer pusher to pour the silicon wafer back from the quartz boat into the wafer cassette. Step 3: After one annealing, the silicon wafers are cleaned using a silicon wafer cleaning machine and then spun dry. Step 4: After the silicon wafer has undergone one annealing and cleaning, use a wafer shaker to rotate the silicon wafer 20-40° relative to the angle during the first annealing. Then, use an automatic wafer pusher to transfer the rotated silicon wafer to the slot of the quartz boat. Place the quartz boat in the constant temperature zone of the annealing furnace at 630-670°C and hold for 10-20 minutes. Remove from the furnace and allow to cool naturally to complete the second annealing of the silicon wafer. Finally, use the automatic wafer pusher to transfer the silicon wafer from the quartz boat back into the wafer cassette.

2. The method for solving the problem of wafer annealing markings according to claim 1, characterized in that: The protective gas introduced in step one is nitrogen.

3. The method for solving the problem of wafer annealing markings according to claim 1, characterized in that: The annealing conditions in step two are to hold the annealing furnace at a constant temperature of 700°C for 10 minutes.

4. The method for solving the problem of wafer annealing markings according to claim 1, characterized in that: The cleaning method in step three is as follows: the silicon wafer is sequentially cleaned in the cleaning machine by passing through QDR-cleaning fluid-QDR.

5. The method for solving the problem of wafer annealing markings according to claim 4, characterized in that: The cleaning solution is an acidic cleaning solution with a solution temperature of 23~28℃. The solution components are HF, HCl, H2O2, and DIW, and their ratio is HF:HCl:H2O2:DIW=1:1:1.5:16~1:1.5:3:

16.

6. The method for solving the problem of wafer annealing markings according to claim 1, characterized in that: The annealing conditions in step four are: holding at 650°C for 10 minutes in the constant temperature zone of the annealing furnace.

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