A silicon wafer back surface sandblasting device and process

Abstract

This invention discloses a sandblasting device and process for the back surface of a silicon wafer. The sandblasting device includes a cover-type spray gun upper support, a housing disposed below the spray gun upper support, and multiple ceramic carriers, an inner gear ring, and an outer gear ring assembled in the housing. The inner gear ring is cylindrical, with internal drive teeth on its outer circumferential surface. The outer gear ring is annular, with a smooth outer circumferential surface and external drive teeth on its inner circumferential surface. Multiple ceramic carriers are evenly distributed between the inner and outer gear rings. The outer circumference of each ceramic carrier meshes with the internal drive teeth on the outer circumferential surface of the inner gear ring and the external drive teeth on the inner circumferential surface of the outer gear ring, respectively. The internal and external drive teeth drive each ceramic carrier to rotate. During sandblasting, the silicon wafer is placed in the silicon wafer bearing hole of the ceramic carrier. The rotation direction of the inner gear ring is set to positive, and the rotation speed is 30-65 rpm; the rotation direction of the outer gear ring is set to negative, and the rotation speed is 25-60 rpm; the sandblasting processing time is 30s-120s; the rotation speed and rotation direction of the inner and outer gear rings are adjusted so that the running trajectory of the silicon wafer within the sandblasting operation range is planetary motion.

Description

Technical Field

[0001] This invention relates to a sandblasting device and process for the back surface of a silicon wafer, belonging to the field of semiconductor silicon wafer processing technology. Background Technology

[0002] Back surface blasting is a crucial step in silicon wafer manufacturing. Its primary function is to create mechanical damage on the wafer surface, forming metal gettering centers. When the silicon wafer undergoes heat treatment, metal atoms introduced during manufacturing move within the wafer and are captured by the damage points created by blasting, thus reducing metal contamination on the front side of the wafer. Traditional blasting equipment performs the blasting process as follows: Figure 1 As shown, a silicon wafer 1 is placed flat on a conveyor belt 2 and enters the sandblasting chamber along direction C under the drive of the conveyor belt. A mixture of high-pressure air and slurry is sprayed onto the back surface of the silicon wafer using a slurry nozzle. The slurry nozzle reciprocates in the transverse directions A and B relative to the silicon wafer surface. Patent document CN211220297U discloses a silicon wafer back scratch treatment device, which also uses a method similar to the above-mentioned conventional sandblasting equipment for treating silicon wafer back scratches. However, this method results in poor uniformity of damage density at different locations on the back surface of the silicon wafer, and may even leave strip-shaped or hazy marks on the back surface.

[0003] Therefore, existing sandblasting equipment and processes need to be improved. Summary of the Invention

[0004] The purpose of this invention is to provide a silicon wafer back surface sandblasting device, which aims to improve the uniformity of damage density on the silicon wafer back surface.

[0005] Another object of the present invention is to provide a process for sandblasting the back surface of a silicon wafer using the above-described apparatus.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A silicon wafer back surface sandblasting device includes a cover-type spray gun upper support, a housing disposed below the spray gun upper support, and multiple ceramic carriers, an inner gear ring, and an outer gear ring assembled in the housing. The inner gear ring is cylindrical with internal drive teeth on its outer circumferential surface. The outer gear ring is annular with a smooth outer circumferential surface and external drive teeth on its inner circumferential surface. Multiple ceramic carriers are evenly distributed between the inner and outer gear rings. The outer circumference of each ceramic carrier meshes with the internal drive teeth on the outer circumferential surface of the inner gear ring and the external drive teeth on the inner circumferential surface of the outer gear ring, respectively. The internal and external drive teeth drive each ceramic carrier to rotate.

[0008] Furthermore, multiple nozzles are fixed on the bracket of the cover-type spray gun. Each nozzle is simultaneously connected to a liquid supply pipe and a high-pressure air pipe, spraying slurry and high-pressure air from the nozzle toward the upper surface of the ceramic carrier. The liquid supply pipe is connected to the slurry tank.

[0009] Furthermore, the upper support of the cover-type spray gun is disc-shaped, with a through hole at the center corresponding to the internal gear ring. The internal gear ring passes through the through hole and rotates freely relative to the through hole.

[0010] Furthermore, the housing is disposed on the outer periphery of the outer gear ring, and the bottom of the housing is connected to the slurry tank via a return pipe.

[0011] Furthermore, the upper surface of the ceramic carrier is provided with a plurality of silicon wafer carrying holes. The ceramic carrier for processing 5-inch silicon wafers has 9 silicon wafer carrying holes; the ceramic carrier for processing 6-inch silicon wafers has 5 silicon wafer carrying holes; the ceramic carrier for processing 8-inch silicon wafers has 4 silicon wafer carrying holes; and the ceramic carrier for processing 12-inch silicon wafers has 1 silicon wafer carrying hole.

[0012] A process for sandblasting the back surface of a silicon wafer using the aforementioned device involves placing the silicon wafer in the wafer support hole of a ceramic carrier, setting the rotation direction of the inner gear ring to positive and the rotation speed to 30-65 rpm; setting the rotation direction of the outer gear ring to negative and the rotation speed to 25-60 rpm; by adjusting the rotation speed and rotation direction of the inner and outer gear rings, the trajectory of the silicon wafer within the sandblasting operation range is made into planetary motion; the sandblasting processing time is 30s-120s.

[0013] Furthermore, when processing 6-inch silicon wafers, the high-pressure air pipe pressure is 0.1-0.3 kPa, the internal gear ring speed is 30-40 rpm, the external gear ring speed is 25-35 rpm, and the sandblasting time is 40-60 s; when processing 8-inch silicon wafers, the high-pressure air pipe pressure is 0.15-0.35 kPa, the internal gear ring speed is 35-45 rpm, the external gear ring speed is 30-40 rpm, and the sandblasting time is 45-65 s; when processing 12-inch silicon wafers, the high-pressure air pipe pressure is 0.2-0.4 kPa, the internal gear ring speed is 40-50 rpm, the external gear ring speed is 35-45 rpm, and the sandblasting time is 50-70 s.

[0014] The beneficial effects of this invention are as follows:

[0015] According to the silicon wafer back surface sandblasting device and process of the present invention, by adjusting the rotation speed and direction of the inner gear ring, the silicon wafer can be made to move in a planetary motion in the device, and the sand slurry can be uniformly sprayed onto the back surface of the silicon wafer, thereby improving the uniformity of the damage density of the back surface of the silicon wafer.

[0016] This invention enables batch sandblasting of multiple silicon wafers, which improves the uniformity of damage density on the back surface of the silicon wafers, while greatly increasing work efficiency and consistency of the back surface quality of silicon wafers in the same batch. Attached Figure Description

[0017] Figure 1This is a schematic diagram showing the direction of silicon wafer movement and the reciprocating motion of the spray gun during the sandblasting process in traditional sandblasting equipment.

[0018] Figure 2 This is a three-dimensional structural diagram of the main components of the sandblasting device in one embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram of the assembly of the cover plate type spray gun support and nozzle in one embodiment of the present invention.

[0020] Figure 4 This is a schematic diagram of the assembly of the internal gear ring, the external gear ring, and the ceramic carrier in one embodiment of the present invention.

[0021] Figure 5 This is a front view of a sandblasting device according to one embodiment of the present invention.

[0022] Figure 6 This is a schematic diagram illustrating the operation of the internal gear ring, external gear ring, ceramic carrier, and silicon wafer of the present invention.

[0023] Figure 7 This is a schematic diagram of the trajectory of a silicon wafer undergoing planetary motion in this invention.

[0024] Figure 8 This is a schematic diagram of the trajectory of a silicon wafer moving in a regular pattern in this invention. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but this does not imply a limitation on the scope of protection of the present invention.

[0026] The silicon wafer back surface sandblasting device of the present invention is used to generate mechanical damage on the back surface of the silicon wafer, forming metal getter centers. For example... Figure 2 As shown, the sandblasting device includes a cover-type spray gun upper support 11, a housing 12 disposed below the spray gun upper support 11, and multiple ceramic carriers 13, an inner gear ring 14, and an outer gear ring 15 assembled in the housing. The inner gear ring is cylindrical with transmission teeth on its outer circumferential surface, serving as the inner transmission teeth of the sandblasting device; the outer gear ring is annular with a smooth outer circumferential surface and transmission teeth on its inner circumferential surface, serving as the outer transmission teeth of the sandblasting device; multiple ceramic carriers are evenly distributed between the inner and outer gear rings, and the outer circumference of each ceramic carrier meshes with the inner transmission teeth on the outer circumferential surface of the inner gear ring and the outer transmission teeth on the inner circumferential surface of the outer gear ring, respectively, and the inner and outer transmission teeth drive each ceramic carrier to rotate.

[0027] like Figure 3As shown, multiple nozzles 16 are fixed on the upper support of the cover-type spray gun, for example, 24 nozzles arranged in 8 groups on the upper support. The nozzles are connected to both the liquid supply system and the high-pressure air pipe, with the nozzles facing the upper surface of the ceramic carrier. The upper support of the cover-type spray gun is disc-shaped, with a through hole at its center corresponding to the internal gear ring. The internal gear ring 14 passes through this through hole and rotates freely relative to it.

[0028] like Figure 4 As shown, in one embodiment of the present invention, four ceramic carriers 13 are evenly arranged between the inner gear ring 14 and the outer gear ring 15, and each ceramic carrier is provided with multiple silicon wafer carrying holes 17. The multiple ceramic carriers do not contact each other. Alternatively, two or three ceramic carriers can be symmetrically arranged. The outer periphery of each ceramic carrier meshes with the inner drive teeth on the outer circumferential surface of the inner gear ring and the outer drive teeth on the inner circumferential surface of the outer gear ring, respectively.

[0029] like Figure 6 As shown in the diagram, the arrows indicate the rotation direction of each part. r1 is the speed of the outer gear ring, and r2 is the speed of the inner gear ring. Under the combined action of r1 and r2, the speed of the ceramic carrier is r3, and the speed of the silicon wafer on the carrier is r4. Simultaneously, the silicon wafer also revolves around the inner gear ring. By controlling the rotational speed and direction of the outer and inner gear rings, the rotational speed of the silicon wafer on the ceramic carrier can be controlled. Figure 7 The figure shows the trajectory of the silicon wafer obtained by theoretical calculation, where r1 is 30 and r2 is 26. This indicates that the trajectory of the silicon wafer carried by the ceramic carrier within the sandblasting operation range is planetary motion.

[0030] like Figure 5 As shown, the housing 12 is located on the outer periphery of the outer toothed ring 15, and the bottom of the housing 12 is connected to the slurry tank 19 via the return pipe 18 for recycling and reusing the slurry. Each nozzle 16 is connected to a high-pressure air pipe 20 and a liquid supply pipe 21, respectively; the liquid supply pipe 21 is connected to the slurry tank 19.

[0031] In this invention, the number of silicon wafer carrying holes on the upper surface of multiple ceramic carriers can be adjusted according to the size of the silicon wafer being processed. When processing 5-inch silicon wafers, a 9-hole ceramic carrier can be used, meaning the ceramic carrier has 9 silicon wafer carrying holes; when processing 6-inch silicon wafers, a 5-hole ceramic carrier can be used, meaning the ceramic carrier has 5 silicon wafer carrying holes; when processing 8-inch silicon wafers, a 4-hole ceramic carrier can be used, meaning the ceramic carrier has 4 silicon wafer carrying holes; and when processing 12-inch silicon wafers, a single-hole ceramic carrier can be used, meaning the ceramic carrier has 1 silicon wafer carrying hole.

[0032] When the aforementioned sandblasting device is in operation, the slurry enters the nozzle 16 from the slurry tank 19 through the supply pipe 21, and is ejected from the nozzle of the nozzle 16 simultaneously with high-pressure air, thereby causing damage to the back surface of the silicon wafer. By adjusting the rotation speed and direction of the inner gear ring 14 and the outer gear ring 15, the silicon wafer is made to move in a planetary motion within the sandblasting coverage area, ensuring the uniformity of the sandblasting density. The slurry ejected from the nozzle of the nozzle 16 is recovered through the housing 12 and then returned to the slurry tank 19 through the return pipe 18, achieving the purpose of slurry recycling.

[0033] Specifically, in the process of sandblasting the back surface of silicon wafers using the aforementioned sandblasting device, the silicon wafer is placed in the silicon wafer bearing hole of the ceramic carrier, the rotation direction of the inner gear ring is set to positive and the rotation speed is 30-65 rpm; the rotation direction of the outer gear ring is set to negative and the rotation speed is 25-60 rpm; the sandblasting processing time is 30s-120s.

[0034] Furthermore, when processing 6-inch silicon wafers, the high-pressure air pipe pressure is 0.1-0.3 kPa, the internal gear ring speed is 30-40 rpm, the external gear ring speed is 25-35 rpm, and the sandblasting time is 40-60 s; when processing 8-inch silicon wafers, the high-pressure air pipe pressure is 0.15-0.35 kPa, the internal gear ring speed is 35-45 rpm, the external gear ring speed is 30-40 rpm, and the sandblasting time is 45-65 s; when processing 12-inch silicon wafers, the high-pressure air pipe pressure is 0.2-0.4 kPa, the internal gear ring speed is 40-50 rpm, the external gear ring speed is 35-45 rpm, and the sandblasting time is 50-70 s.

[0035] Traditional sandblasting methods

[0036] like Figure 1 As shown, using a traditional sandblasting method, silicon wafer 1 is placed flat on a conveyor belt 2. Driven by the conveyor belt, it moves at a speed of 0.02 m / s along the C direction. The speed of the nozzle reciprocating in the A and B directions relative to the silicon wafer surface is 0.8 m / s. The slurry concentration is 1.5 mg / mL, and the nozzle pressure is 0.32 kPa. One silicon wafer, numbered 1, was randomly selected and sandblasted using this process. The back surface damage density is shown in Table 1.

[0037] Example 1

[0038] The sandblasting device of the present invention (structure as follows) is used. Figures 2-5(As shown) 5-inch silicon wafers were processed using a 9-hole ceramic carrier. Five carriers were evenly distributed on the inner gear ring (without contact between the carriers). The teeth of the carriers meshed with the inner and outer gear rings, and the silicon wafer was placed in the wafer support holes. The high-pressure air pipe pressure was 0.10 kPa, the slurry concentration was 1.20 mg / mL, the rotation speed of the inner gear ring was 30 rpm (positive direction), the rotation speed of the outer gear ring was 25 rpm (negative direction), and the sandblasting time was 45 s. One silicon wafer, numbered 2, was randomly selected for sandblasting using this process. The back surface damage density is shown in Table 1.

[0039] Example 2

[0040] The sandblasting apparatus of this invention is used to process 6-inch silicon wafers, using a 5-hole ceramic carrier. Five carriers are evenly distributed on the inner gear ring (without contact between carriers), and the teeth of the carriers mesh with the inner and outer gear rings. The silicon wafer is placed in the wafer support hole. The high-pressure air pipe pressure is 0.15 kPa, the slurry concentration is 1.20 mg / mL, the inner gear ring speed is 35 rpm (positive direction), the outer gear ring speed is 30 rpm (negative direction), and the sandblasting time is 50 s. One silicon wafer, numbered 3, was randomly selected and sandblasted using this process; the back surface damage density is shown in Table 1.

[0041] Example 3

[0042] The sandblasting apparatus of this invention is used to process 8-inch silicon wafers, using a 4-hole ceramic carrier. Five carriers are evenly distributed on the inner gear ring (without contact between the carriers), and the teeth of the carriers mesh with the inner and outer gear rings. The silicon wafer is placed in the silicon wafer support hole. The pressure of the high-pressure air pipe is 0.20 kPa, the slurry concentration is 1.20 mg / mL, the rotation speed of the inner gear ring is 40 rpm (positive direction), the rotation speed of the outer gear ring is 35 rpm (negative direction), and the sandblasting time is 50 s. One silicon wafer sandblasted using this process is randomly selected and numbered 4. The back surface damage density is shown in Table 1.

[0043] Example 4

[0044] The sandblasting apparatus of this invention was used to process 12-inch silicon wafers, using single-hole ceramic carriers. Five carriers were evenly distributed on the inner gear ring (without contact between the carriers), and the teeth of the carriers meshed with the inner and outer gear rings. The silicon wafer was placed in the silicon wafer bearing hole. The pressure of the high-pressure air pipe was 0.30 kPa, the slurry concentration was 1.20 mg / mL, the rotation speed of the inner gear ring was 45 rpm (positive direction), the rotation speed of the outer gear ring was 40 rpm (negative direction), and the sandblasting time was 55 s. One silicon wafer, numbered 5, was randomly selected and sandblasted using this process. The back surface damage density is shown in Table 1.

[0045] Comparative example (regular movement of silicon wafer)

[0046] The sandblasting apparatus of this invention is used to process 6-inch silicon wafers, employing a 5-hole ceramic carrier. Five carriers are evenly distributed within the inner gear ring (without contact between carriers). The teeth of the carriers mesh with the inner and outer gear rings, placing the silicon wafer into the wafer support holes. The high-pressure air hose pressure is 0.15 kPa, the slurry concentration is 1.20 mg / mL, the inner gear ring rotates at 21 rpm in positive direction, and the outer gear ring rotates at 21 rpm in positive direction. The trajectory of the silicon wafer within the sandblasting operating range is as follows: Figure 8 As shown, the sandblasting time is 50 seconds. One silicon wafer, numbered 6, was randomly selected after sandblasting using this process. The back surface damage density is shown in Table 1.

[0047] Table 1. Comparison of damage density on the back surface of silicon wafers after sandblasting in Examples 1-4, traditional sandblasting methods, and comparative examples.

[0048]

[0049] As shown in Table 1, the mean sandblasting density (AVE) of silicon wafers using traditional sandblasting methods, Examples 1-4, and the comparative example is similar. The standard deviation (STD) of the sandblasting density in Examples 1-4 is smaller, indicating less data dispersion. This demonstrates that using the present invention to sandblast silicon wafers can ensure the uniformity of damage density on the back surface of the silicon wafer. Furthermore, the maximum and minimum sandblasting densities (MAX and MIN) in Examples 1-4 are close, further demonstrating the excellent performance of the present invention. In addition, the return system effectively avoids slurry waste and maintains a clean and tidy working environment.

Claims

1. A process for sandblasting the back surface of a silicon wafer using a sandblasting device, characterized in that, The sandblasting device includes a cover plate type spray gun upper support, a housing located below the spray gun upper support, and multiple ceramic carriers, an internal gear ring, and an external gear ring assembled in the housing; The inner gear ring is cylindrical with internal drive teeth on its outer circumference; the outer gear ring is annular with a smooth outer circumference and external drive teeth on its inner circumference; multiple ceramic carriers are evenly distributed between the inner and outer gear rings, and the outer circumference of each ceramic carrier meshes with the internal drive teeth on the outer circumference of the inner gear ring and the external drive teeth on the inner circumference of the outer gear ring, respectively. The internal and external drive teeth drive each ceramic carrier to rotate. Multiple nozzles are fixed on the bracket of the cover-type spray gun. Each nozzle is connected to a liquid supply pipe and a high-pressure air pipe at the same time. The slurry and high-pressure air are sprayed from the nozzle toward the upper surface of the ceramic carrier at the same time. The liquid supply pipe is connected to the slurry tank. The silicon wafer is placed in the silicon wafer bearing hole of the ceramic carrier. The direction of rotation of the inner gear ring is set to positive, and the speed is 30-65 rpm; the direction of rotation of the outer gear ring is set to negative, and the speed is 25-60 rpm. By adjusting the speed and direction of rotation of the inner and outer gear rings, the running trajectory of the silicon wafer within the sandblasting operation range is planetary motion. When processing 6-inch silicon wafers, the high-pressure air pipe pressure is 0.1-0.3 kPa, the internal gear ring speed is 30-40 rpm, the external gear ring speed is 25-35 rpm, and the sandblasting time is 40-60 s. When processing 8-inch silicon wafers, the high-pressure air pipe pressure is 0.15-0.35 kPa, the internal gear ring speed is 35-45 rpm, the external gear ring speed is 30-40 rpm, and the sandblasting time is 45-65 s. When processing 12-inch silicon wafers, the high-pressure air pipe pressure is 0.2-0.4 kPa, the internal gear ring speed is 40-50 rpm, the external gear ring speed is 35-45 rpm, and the sandblasting time is 50-70 s.

2. The process according to claim 1, characterized in that, The upper support of the cover-type spray gun is disc-shaped, with a through hole at the center corresponding to the inner gear ring. The inner gear ring passes through the through hole and rotates freely relative to the through hole.

3. The process according to claim 1, characterized in that, The housing is located on the outer periphery of the outer gear ring, and the bottom of the housing is connected to the slurry tank via a return pipe.

4. The process according to claim 1, characterized in that, The ceramic carrier has multiple silicon wafer carrying holes on its upper surface. The ceramic carrier for processing 5-inch silicon wafers has 9 silicon wafer carrying holes, and the ceramic carrier for processing 6-inch silicon wafers has 5 silicon wafer carrying holes. The ceramic carrier used for processing 8-inch silicon wafers has 4 wafer carrier holes; The ceramic carrier used for processing 12-inch silicon wafers has one wafer carrier hole.

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