Method and device for processing polycrystalline silicon grating groove

Abstract

The invention relates to a machining method and device for a polycrystalline silicon grating groove, and belongs to the technical field of precise material machining. The machining method comprises the following steps that S1, a polycrystalline silicon workpiece is prepared and fixed; the polycrystalline silicon workpiece is provided with a first processing surface and a second processing surface; the first machining face is located on the back face of the second machining face, and the second machining face is a working face of a to-be-machined grating groove. S2, pre-plane grinding is conducted on the first machining face; and S3, grid groove machining is conducted on the second machining face, then allowance machining is conducted on the first machining face obtained after pre-plane grinding, and a polycrystalline silicon grid groove workpiece is obtained. According to the machining method, the production efficiency is improved by optimizing the machining process, rework and waste materials are reduced, high reliability and consistency of products can be ensured, and economical efficiency and sustainability of polycrystalline silicon precision machining are improved.

Description

Technical Field

[0001] This application belongs to the field of precision material processing technology, specifically relating to a processing method and apparatus for polycrystalline silicon grid grooves. Background Technology

[0002] In the manufacturing process of polycrystalline silicon semiconductor devices, grid groove processing is one of the key steps to ensure the electrical performance and structural stability of the product. Currently, the traditional processing methods commonly used in the industry mainly include sequential processing from the first surface to the second surface and integrated roughing and finishing milling. While these methods have long been used in the precision machining of polycrystalline silicon materials, they have significant limitations. Uneven stress distribution occurs in polycrystalline silicon materials during grid groove forming, especially when the bottom thickness is processed to a relatively thin stage, making it highly susceptible to perforation defects on the back side. These defects severely reduce the product yield and have long been difficult to eradicate using existing technologies, becoming a major bottleneck restricting the reliability of high-precision devices.

[0003] Traditional roughing and finishing milling relies on continuous cutting with a specific-sized grinding rod. The tool is subjected to continuous load during machining, resulting in rapid wear. The limited number of products that can be processed with a single grinding rod leads to high tool costs. In actual production, tool costs account for a very high proportion of the total product cost, severely limiting cost control optimization. Simultaneously, the surface roughness of polycrystalline silicon grid trenches fluctuates significantly under existing machining methods, affecting the performance consistency of high-precision devices. Fluctuations in surface quality affect product appearance, impair electrical reliability, and may lead to performance degradation over long-term use. Therefore, the shortcomings of existing technologies in meeting the requirements of high efficiency, low cost, and high stability urgently necessitate optimization through innovative methods to improve overall manufacturing capabilities. Summary of the Invention

[0004] In view of this, this application provides a method and apparatus for processing polycrystalline silicon grid channels. By optimizing the reverse processing sequence and process breakdown, combined with a dedicated grinding rod and tooling design, the processing quality of polycrystalline silicon grid channels is significantly improved, eliminating back-side perforation defects and improving surface roughness stability. Simultaneously, it extends the service life of the grinding rod, reduces tooling costs, optimizes the processing flow to improve production efficiency, reduces rework and waste, ensures high product reliability and consistency, and enhances the economy and sustainability of polycrystalline silicon precision machining.

[0005] In a first aspect, this application provides a method for processing a polycrystalline silicon grid groove, comprising the following steps: S1: preparing and fixing a polycrystalline silicon workpiece; the polycrystalline silicon workpiece has a first processing surface and a second processing surface; the first processing surface is located on the back side of the second processing surface, and the second processing surface is the working surface of the grid groove to be processed; S2: performing pre-surface grinding on the first processing surface; S3: first processing the grid groove on the second processing surface, and then performing allowance processing on the first processing surface after pre-surface grinding to obtain a polycrystalline silicon grid groove workpiece; wherein, the grid groove processing includes roughing and finishing; the roughing includes pre-drilling and straight groove drawing to form a rough grid groove; the finishing is processing the sidewalls and bottom of the rough grid groove.

[0006] This application employs a reverse processing sequence, where the second processing surface (the working surface of the grid channel) is processed first, and the grid channel is formed under stable support on the first processing surface (the back side). This effectively avoids the back-side perforation defect caused by stress concentration in traditional processing sequences. Simultaneously, the grid channel processing is divided into two stages: roughing and finishing. Roughing removes most of the excess material quickly through pre-drilling and straight-line grooving, significantly reducing the instantaneous load on the tool. Finishing precisely trims the sidewalls and bottom of the rough grid channel to ensure dimensional accuracy and surface consistency. This optimized division of labor not only disperses processing stress but also improves process stability through refined control, completely resolving the back-side perforation problem in polycrystalline silicon grid channel processing. This substantially improves the product yield and significantly enhances the surface roughness stability, preventing micro-cracks caused by processing vibration and ensuring the electrical performance and structural reliability of semiconductor devices.

[0007] In some implementations, preparing the polycrystalline silicon workpiece includes inspecting and surface grinding the polycrystalline silicon blank. This preparation process provides a stable support foundation for subsequent precision machining, avoiding uneven clamping or machining deviations caused by initial defects or non-planarity of the blank. It lays a reliable foundation for optimizing the reverse machining sequence and process breakdown, significantly improving the stability of the machining process, reducing vibration or abnormal tool wear caused by blank unevenness, indirectly supporting the improvement of overall yield and surface quality consistency, and providing a fundamental guarantee for the high-precision machining of polycrystalline silicon grid channels.

[0008] In some embodiments, surface grinding includes using a vertical grinding machine with a rotational speed of 800-1000 rpm, a rotary table speed of 10-20 rpm, and a depth of cut of 0.002-0.006 mm per revolution. By adjusting the cutting parameters of surface grinding within the above-mentioned preferred range, controllable low-speed cutting reduces machining vibration and stress concentration, laying a smooth foundation for subsequent precision machining of the grid grooves, effectively improving workpiece clamping stability, preventing back-side perforation defects, and ensuring dimensional accuracy consistency.

[0009] In some embodiments, pre-surface grinding includes: using a four-axis CNC milling machine with a rotational speed of 6000~8000 rpm, a rotary table speed of 10~20 rpm, and a cutting depth of 0.01~0.05 mm / cut. By adjusting the cutting parameters of pre-surface grinding within the above-mentioned preferred range, precise planarization of the first machined surface of the polycrystalline silicon workpiece can be achieved, ensuring the parallelism and flatness of the workpiece and laying a stable reference for subsequent grid groove machining.

[0010] In some embodiments, the cutting parameters for roughing are as follows: the machine tool is a three-axis CNC milling machine, the rotational speed is 10,000~18,000 rpm, the feed rate is 80~200 mm / min, and the depth of cut is 0.5~2 mm / cut. By adjusting the cutting parameters for roughing within the above-mentioned preferred range, cutting efficiency and stress distribution can be balanced, the risk of back-side perforation caused by local overload can be avoided, the stability of the machining process can be improved, and the dimensional accuracy and surface quality consistency of the polycrystalline silicon grid groove can be guaranteed.

[0011] In some embodiments, the cutting parameters for finishing are as follows: the machine tool is a three-axis CNC milling machine, the rotational speed is 10,000~18,000 rpm, the feed rate is 1,000~1,600 mm / min, and the depth of cut is 0.1~0.5 mm / cut. By adjusting the cutting parameters for finishing within the above-mentioned preferred range, precise finishing of the sidewalls and bottom of the grid channel can be achieved, reducing processing vibration and stress concentration, and ensuring the dimensional accuracy and surface quality consistency of the polycrystalline silicon grid channel.

[0012] In some embodiments, the cutting parameters for the allowance machining are as follows: the machine tool is a four-axis CNC milling machine with a rotational speed of 5000~8000 rpm, a rotary table speed of 10~20 rpm, and a cutting depth of 0.02~0.05 mm / cut per revolution. By adjusting the cutting parameters for allowance machining within the above-mentioned preferred range, stress concentration during machining can be reduced, damage or deformation of the formed grid groove can be avoided, and the dimensional accuracy and structural integrity of the workpiece can be guaranteed, thereby indirectly supporting the improvement of the yield rate.

[0013] Secondly, this application also provides an apparatus for performing the above-mentioned processing method, including a grinding rod and a vacuum chuck fixture for polycrystalline silicon; wherein, the grinding rod has a specification of D1.8; the grinding rod is used for roughing; and the vacuum chuck fixture for polycrystalline silicon is used to fix the polycrystalline silicon workpiece. By using a dedicated grinding rod to enhance wear resistance and perform efficient roughing, combined with the use of a vacuum chuck fixture to achieve stable workpiece fixation, this apparatus provides reliable support for the processing method. This apparatus can extend tool life, reduce production costs, and improve the stability of the processing, effectively preventing workpiece breakage or dimensional deviations caused by vibration, and ensuring the processing accuracy and yield of the polycrystalline silicon grid groove.

[0014] In some embodiments, the grinding rod's material composition by weight percentage includes 40% silver, 25.4% indium, 23.27% copper, 11.23% titanium, and 0.103% nickel. Utilizing the synergistic effect of multi-element alloys optimizes the tool's hardness and wear resistance, significantly extending the grinding rod's lifespan, reducing tool replacement frequency and production costs, while ensuring machining process stability and minimizing dimensional deviations caused by wear, thereby supporting high-precision and high-quality machining of polycrystalline silicon grid channels.

[0015] In some implementations, the vacuum chuck fixture for polycrystalline silicon includes a positioning groove. This helps improve processing stability, prevents workpiece cracking or damage caused by vibration, ensures the dimensional accuracy and structural integrity of the polycrystalline silicon grid, and improves product yield and quality consistency. Attached Figure Description

[0016] Figure 1 A schematic diagram of a grinding rod structure for performing the processing method of this application is provided for this application. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0018] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0019] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, every point or individual value between the endpoints of the range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value or with other lower or upper limits to form a range not explicitly stated.

[0020] Traditional methods employ a sequential approach from the first machining surface to the second machining surface and a roughing and finishing milling method, which leads to uneven material stress distribution, easily causing perforation defects on the back side, high tool wear increasing costs, and surface roughness fluctuations affecting device performance consistency and long-term reliability.

[0021] To address the aforementioned technical problems, this application provides a method for processing polycrystalline silicon grid trenches, comprising the following steps:

[0022] S1: Prepare and fix the polycrystalline silicon workpiece; the polycrystalline silicon workpiece has a first processing surface and a second processing surface; the first processing surface is located on the back of the second processing surface, and the second processing surface is the working surface of the grid groove to be processed; S2: Perform pre-surface grinding on the first machining surface; S3: First, perform grid groove processing on the second processing surface, and then perform allowance processing on the first processing surface after pre-surface grinding to obtain a polycrystalline silicon grid groove workpiece. The processing of the grid channel includes roughing and finishing; roughing includes pre-drilling and straight grooving to form a rough grid channel; finishing involves processing the side walls and bottom of the rough grid channel.

[0023] In some embodiments, the pre-holes are two holes pre-machined at both ends of a waist groove for straight groove cutting; the holes include, but are not limited to, elliptical holes.

[0024] In some embodiments, the straight groove is a groove operation performed by passing through a straight path from the first hole to the second hole of the pre-drilled hole.

[0025] In some embodiments, the width of the straight groove is 2mm.

[0026] In some embodiments, the allowance is the difference between the size of the workpiece to be processed and the size of the final finished product.

[0027] In addition, this application also provides an apparatus for performing the above-described processing method, including a grinding rod and a vacuum chuck fixture for polycrystalline silicon; wherein, the grinding rod has a specification of D1.8; the grinding rod is used for roughing; and the vacuum chuck fixture for polycrystalline silicon is used to fix the polycrystalline silicon workpiece.

[0028] In some embodiments, D1.8 refers to the diameter of the grinding rod being 1.8 mm.

[0029] Example 1) Perform performance testing on polycrystalline silicon blanks.

[0030] 2) Fix the polycrystalline silicon blank that has passed the performance test with a polycrystalline silicon vacuum chuck fixture, and use a vertical grinder to perform surface grinding on the first and second surfaces of the polycrystalline silicon blank to remove the surface oxide layer. The processing parameters are: rotation speed 900 rpm, turntable speed 20 rpm, and cutting depth per revolution 0.005 mm / time.

[0031] 3) Perform pre-surface grinding on the first machining surface. The machining machine is a four-axis CNC milling machine with a D80 grinding wheel. The machining parameters are: rotation speed 6000 rpm, rotary table speed 20 rpm, and cutting depth 0.05 mm / cut.

[0032] 4) Rough machining is performed on the second machining surface using a D1.8 specification grinding bar. Pre-holeing and straight grooving are used to form a rough grid groove. The machining machine is a three-axis CNC milling machine with the following machining parameters: speed 15000rpm, feed rate 100mm / min, and cutting depth 1mm / cut.

[0033] 5) The sidewalls and bottom of the formed coarse grid groove are finished. The machining parameters are: the machine tool is a three-axis CNC milling machine, the machining parameters are: speed 15000rpm, feed rate 1400mm / min, and cutting depth 0.3mm / cut.

[0034] 6) Then, perform the remaining machining on the first working surface after pre-surface grinding. The machining machine tool is a four-axis CNC milling machine, and a D80 grinding wheel is selected to complete the workpiece manufacturing and obtain the polycrystalline silicon grid groove workpiece. The machining parameters are: rotation speed 6000rpm, turntable speed 10rpm, and cutting depth per revolution 0.02mm / time.

[0035] For roughing, one D1.8 specification grinding rod is used to process 320 polycrystalline silicon grid slots; for finishing, two D1.7 specification traditional grinding rods are used to process 160 polycrystalline silicon grid slots in each group.

[0036] Comparative Example The traditional machining method is adopted, with the machining sequence from the first machining surface to the second machining surface and the rough and finish integrated milling method. Six traditional grinding rods with a specification of D1.7 are selected, and 60 polycrystalline silicon grid grooves are machined in each group.

[0037] Test methods A four-probe resistance meter is used to measure the electrical performance parameters of polycrystalline silicon materials to ensure that the workpiece meets the performance requirements of semiconductor devices.

[0038] A coordinate measuring machine is used to inspect the dimensional accuracy of the grid channel; a surface roughness meter is used to measure the roughness Ra value of the grid channel (ensuring it is ≤1.546); a profilometer is used to measure the sidewall and bottom profile of the grid channel to ensure the accuracy of the finished product profile; and an image sensor is used to visually inspect the finished product for defects such as chipping.

[0039] Grinding rod wear: The wear of the grinding rod after the completed machining is measured at 80°C. A test groove was prepared at the 80° edge, and the groove was cut along the centerline. The roughness of the sidewall of the grinding rod was evaluated using a two-dimensional image measuring instrument.

[0040] Test Results 1. By using the method and apparatus of this invention, and employing the grinding rod of specification D1.8 of this invention for rough machining, the surface roughness of the polycrystalline silicon grid groove workpiece is significantly improved: The first group processed 160 pieces, with a maximum Ra value of 1.212, no back perforations, and a pass rate of 100%. The second group processed 160 pieces, with a maximum Ra value of 1.546, no back perforations, and a pass rate of 100%.

[0041] 2. In comparison, traditional grinding rods are processed in groups of 60, with a maximum Ra value of 2.248 and a back defect rate of 15%.

[0042] 3. The wear of the grinding rod is reduced by 50% compared to traditional grinding rods, and it can still be used.

[0043] The beneficial effects of this invention are as follows: 1. This invention can solve the problem of back-side perforation in polycrystalline silicon grid channel processing, and resolve the defects caused by uneven stress distribution due to traditional processing sequence. By adopting a reverse processing path and separating roughing and finishing processes, the risk of damage caused by insufficient back-side thickness during processing is avoided, ensuring the product qualification rate and surface quality stability.

[0044] 2. This invention significantly reduces tool wear and production costs through specialized tool design and optimized machining parameters, avoids the rapid wear problem in traditional rough and finish milling, and ensures extended grinding rod life and optimized unit product cost.

[0045] 3. This invention improves processing efficiency while ensuring quality. By optimizing the processing sequence and cutting parameters, the overall processing cycle is improved, the product qualification rate is increased, rework and waste disposal are reduced, and production efficiency is indirectly improved.

[0046] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for processing polycrystalline silicon grid channels, characterized in that, Includes the following steps: S1: Prepare and fix the polycrystalline silicon workpiece; the polycrystalline silicon workpiece has a first processing surface and a second processing surface; the first processing surface is located on the back side of the second processing surface, and the second processing surface is the working surface of the grid groove to be processed; S2: Perform pre-surface grinding on the first machining surface; S3: First, perform grid groove processing on the second processing surface, and then perform allowance processing on the first processing surface after pre-plane grinding to obtain a polycrystalline silicon grid groove workpiece. The processing of the grid channel includes roughing and finishing; the roughing includes pre-drilling and straight groove drawing to form a rough grid channel; the finishing is the processing of the sidewalls and bottom of the rough grid channel.

2. The processing method according to claim 1, characterized in that, The preparation of the polycrystalline silicon workpiece includes: inspecting the polycrystalline silicon blank and performing surface grinding.

3. The processing method according to claim 2, characterized in that, The surface grinding process includes: using a vertical grinding machine with a rotation speed of 800~1000 rpm, a turntable speed of 10~20 rpm, and a cutting depth of 0.002~0.006 mm / cycle per revolution.

4. The processing method according to claim 1, characterized in that, The pre-surface grinding includes: the machine tool is a four-axis CNC milling machine with a rotation speed of 6000~8000rpm, a rotary table speed of 10~20rpm, and a cutting depth of 0.01~0.05mm / time.

5. The processing method according to claim 1, characterized in that, The cutting parameters for roughing are as follows: the machine tool is a three-axis CNC milling machine, the rotation speed is 10000~18000rpm, the feed rate is 80~200mm / min, and the cutting depth is 0.5~2mm / cut.

6. The processing method according to claim 1, characterized in that, The cutting parameters for the finishing process are as follows: the machine tool is a three-axis CNC milling machine with a rotation speed of 10,000~18,000 rpm, a feed rate of 1,000~1,600 mm / min, and a cutting depth of 0.1~0.5 mm / cut.

7. The processing method according to claim 1, characterized in that, The cutting parameters for the machining of the allowance are as follows: the machining machine is a four-axis CNC milling machine with a rotation speed of 5000~8000rpm, a turntable rotation speed of 10~20rpm, and a cutting depth of 0.02~0.05mm / time per revolution.

8. An apparatus for performing the processing method according to any one of claims 1 to 7, characterized in that, Including vacuum chuck fixtures for grinding rods and polysilicon; The grinding rod has a specification of D1.8; the grinding rod is used for roughing; the polycrystalline silicon vacuum chuck fixture is used to fix the polycrystalline silicon workpiece.

9. The apparatus according to claim 8, characterized in that, The material composition of the grinding rod, by weight percentage, includes 40% silver, 25.4% indium, 23.27% copper, 11.23% titanium, and 0.103% nickel.

10. The apparatus according to claim 8, characterized in that, The vacuum chuck fixture for polycrystalline silicon includes a positioning groove.

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