Non-contact processing method for semiconductor workpiece solt groove

Abstract

The application belongs to the technical field of semiconductor material processing, and particularly relates to a non-contact processing method for solt grooves of a semiconductor workpiece, which comprises workpiece pretreatment, placing the pretreated semiconductor workpiece on a vacuum adsorption clamp, fixing the workpiece through vacuum negative pressure adsorption to avoid mechanical clamping stress, immersing the semiconductor workpiece in electric spark processing oil, controlling a composite electrode to feed along the Z axis and cooperating with a shaking motion to perform non-contact electric spark processing on the solt groove of the workpiece, sequentially executing three stages of rough processing, semi-finishing and finishing, using a cooling medium to perform circulating cooling on the processing area during the processing, real-time measuring of the processed groove depth, groove length and groove width, dynamic adjustment of the Z-axis feeding depth and the electrode shaking amount according to the real-time measured processed groove depth, groove length and groove width, and final size detection by using a three-coordinate measuring machine or an image measuring instrument after the processing is completed, and compensation processing is performed if the size is out of tolerance.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor material processing technology, and specifically relates to a non-contact processing method for slots in semiconductor workpieces. Background Technology

[0002] In the semiconductor equipment manufacturing industry, precision parts such as exhaust fan components need to be machined with a large number of micron-level solder grooves (groove width < 0.1 mm, quantity > 200) to achieve efficient heat dissipation, gas flow guidance and structural fixation functions.

[0003] Semiconductor materials (such as silicon, silicon carbide, and gallium arsenide) have the physical properties of high brittleness and low fracture toughness. Traditional mechanical grinding removes material through rigid contact between the tool and the workpiece. This leads to the following problems: the impact force generated when the tool enters the groove causes microcracks to propagate at the groove edge, especially at micrometer-wide grooves (<0.1mm), where the chipped edge width can reach 20%-30% of the groove width, severely exceeding tolerance requirements; the mechanical stress generated during grinding forms a plastic deformation layer with a depth of 2-5μm on the groove sidewall, and subsequent chemical etching processes can only remove about 1μm of damage. This residual layer causes a 15%-20% decrease in the device's insulation performance, directly affecting product lifespan; traditional processes use a sequential, groove-by-groove machining mode, with a single-piece machining cycle of 50-60 hours for 250 grooves.

[0004] Therefore, traditional mechanical grinding methods result in poor product quality, short product life, and low production efficiency. Summary of the Invention

[0005] In view of this, the present invention provides a non-contact processing method for the slot of a semiconductor workpiece to solve the technical problems of poor product quality, low lifespan and low production efficiency caused by traditional mechanical grinding methods in the prior art.

[0006] To achieve the above objectives, this application adopts the following approach:

[0007] A non-contact processing method for a semiconductor workpiece slot includes the following steps:

[0008] S10. Workpiece pretreatment: The semiconductor workpiece blank with resistivity meeting the requirements is processed to a preset thickness, and the outer diameter, inner diameter and solt groove steps of the semiconductor workpiece are rough processed, and a processing reference surface is set to obtain the pretreated semiconductor workpiece.

[0009] S20. Workpiece clamping: The pre-treated semiconductor workpiece is clamped and fixed by a vacuum adsorption fixture to avoid mechanical clamping stress, and the vacuum adsorption fixture is adjusted to keep the processing surface of the pre-treated semiconductor workpiece parallel to the horizontal plane;

[0010] S30. Processing environment setup: Immerse the vacuum adsorption fixture with the pretreated semiconductor workpiece in electrical discharge machining oil;

[0011] S40. Multi-stage electrical discharge machining: The composite electrode is clamped on the spindle of the electrical discharge machine tool, and the composite electrode is controlled to feed along the Z-axis and cooperate with the rocking motion. According to the set machining reference face, non-contact electrical discharge machining is performed on the solt groove of the pre-treated semiconductor workpiece immersed in electrical discharge machining oil. The non-contact electrical discharge machining includes three stages of roughing, semi-finishing and finishing of the solt groove in sequence. During the machining process, the pre-treated semiconductor workpiece is continuously flushed with oil and the machining area is circulated and cooled.

[0012] S50. Online detection and compensation: The depth, length and width of the groove processed during the multi-stage electrical discharge machining process are measured in real time. The Z-axis feed depth and electrode oscillation are dynamically adjusted based on the real-time measured depth, length and width of the groove. After the machining is completed, the final dimension is detected. If the dimension exceeds the tolerance, the process returns to step S40 for compensation. If the dimension does not exceed the tolerance, the processed semiconductor workpiece is obtained.

[0013] Preferably, the semiconductor workpiece to be processed is a P-type polycrystalline silicon semiconductor material with a resistivity ≤ 4Ω·cm.

[0014] Preferably, in step S40, the specific parameters for the three stages of roughing, semi-finishing, and finishing are as follows:

[0015] Rough machining stage: Use parameters with a pulse width of 100μs, a peak current of 10A, and positive polarity, with a discharge time of 500ms, and machine to a depth of 0.2mm.

[0016] Semi-finishing stage: Using parameters such as pulse width of 80μs, peak current of 8A, and positive polarity, the discharge time is 300ms, and the machining taper is controlled to be less than 0.01°;

[0017] In the finishing stage, a high-frequency pulse parameter of 15μs pulse width and 2A peak current is used, with a discharge time of 200ms, to achieve a surface roughness Ra≤1.6μm and a groove width tolerance of ±0.01mm.

[0018] Preferably, in step S40, at least six rinsing nozzles are used to continuously rinsing the pre-treated semiconductor workpiece with oil, and the arrangement of the rinsing nozzles ensures that the rinsing path completely covers the solt area of ​​the pre-treated semiconductor workpiece.

[0019] Preferably, in step S30, the level of the electrical discharge machining oil exceeds the processing surface of the pretreated semiconductor workpiece by at least 30 mm.

[0020] Preferably, when the semiconductor workpiece blank is processed to a preset thickness, the tolerance is controlled within ±0.05mm.

[0021] Preferably, the vacuum adsorption fixture includes a frame, a mounting plate, an adsorption ring, a suction component, and several support columns. One end of each support column is connected to the frame, and the other end of each support column passes through the mounting plate and is connected to the adsorption ring. The several support columns are evenly distributed along the circumference of the adsorption ring. The adsorption ring has a hollow structure. The suction component is located on the outer wall of the adsorption ring and can draw air into the hollow part of the adsorption ring. Several adsorption holes are opened on the inner wall of the adsorption ring. The mounting plate is connected to the adsorption ring. An annular boss is provided on the side of the mounting plate connected to the adsorption ring. An adsorption groove is provided between the annular boss and the inner wall of the adsorption ring. The semiconductor workpiece to be processed can be placed on the adsorption groove. A connector is also provided at the bottom of the frame for connecting to an EDM machine.

[0022] Preferably, a plurality of lifting mechanisms are further provided between the frame and the adsorption ring. One end of the lifting mechanism is connected to the frame, and the other end of the lifting mechanism is connected to the adsorption ring, for adjusting the height of the adsorption ring so that the processing surface of the semiconductor workpiece to be processed remains parallel to the horizontal plane.

[0023] Preferably, the composite electrode includes an ER chuck, a stainless steel reinforcing plate, a graphite bending-resistant portion, a graphite forming feature portion, a positioning post, and several drainage holes. The upper end of the ER chuck is connected to the spindle of the EDM machine tool, the lower end of the ER chuck is connected to the graphite bending-resistant portion, the graphite bending-resistant portion is connected to one side of the stainless steel reinforcing plate, the graphite forming feature portion is disposed on the other side of the stainless steel reinforcing plate, and its shape is consistent with the negative shape of the slot to be processed. The drainage holes are opened through the stainless steel reinforcing plate, and the positioning post is disposed on the stainless steel reinforcing plate.

[0024] Preferably, after the cumulative processing time of the composite electrode reaches 72 hours, a smooth surface rework is required. During the rework, a milling cutter with no less than four cutting edges and a diameter slightly larger than the groove width is used to cut along the length direction of the graphite forming feature. The depth of cut in a single cut is controlled within 0.1 mm, and the feed rate is controlled within 1000 mm / min.

[0025] In the aforementioned non-contact processing method for semiconductor workpiece slots, vacuum adsorption clamping and electrical discharge machining (EDM) are employed to avoid damage to the workpiece caused by mechanical contact, thus improving the quality of the semiconductor workpiece. The processing environment setup and circulating cooling ensure the stability of the processing, reducing processing errors caused by environmental factors and heat accumulation. In multi-stage EDM, an electrical discharge is generated between the composite electrode and the semiconductor workpiece; the instantaneous high temperature causes localized melting and vaporization of the workpiece material, thereby achieving material removal and improving processing efficiency. This application integrates processing, measurement, and compensation, significantly improving product quality and consistency in mass production, and preventing semiconductor workpiece scrap due to process instability. As demonstrated by the following examples, compared with traditional machining methods, the method provided in this application reduces the surface roughness of semiconductor workpieces from less than Ra3.2μm to less than Ra1.6μm, and there are no obvious tool marks on the surface of the semiconductor workpiece. The damage layer in the groove is reduced from 20μm-50μm to 1μm-5μm, which is a significant reduction. The quality is higher, the service life is improved, and the processing efficiency is increased from 52H / piece to 12H / piece, which greatly shortens the processing time and improves the production efficiency. Attached Figure Description

[0026] Figure 1 This is an isometric view of the vacuum adsorption fixture in this invention.

[0027] Figure 2 This is a top view of the vacuum adsorption fixture in this invention.

[0028] Figure 3 This is a bottom view of the vacuum adsorption fixture in this invention.

[0029] Figure 4 This is a schematic diagram of the vacuum adsorption fixture from another angle in this invention.

[0030] Figure 5 This is a left view of the vacuum adsorption fixture in this invention.

[0031] Figure 6 This is a top view of the composite electrode in this invention.

[0032] Figure 7 This is a bottom view of the composite electrode in this invention.

[0033] Figure 8 This is a left view of the composite electrode in this invention.

[0034] Figure 9 This is an isometric view of the composite electrode in this invention.

[0035] In the figure, there are vacuum adsorption fixture 100, frame 110, mounting plate 120, adsorption ring 130, boss 131, adsorption tank 132, suction component 140, support column 150, connector 111, lifting mechanism 160, composite electrode 200, ER chuck 210, stainless steel reinforcing plate 220, graphite anti-bending part 230, graphite forming feature part 240, positioning column 250, and drain hole 260. Detailed Implementation

[0036] To facilitate understanding of this application, a more comprehensive description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are also given. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to enable a more thorough and complete understanding of the disclosure of this application.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0038] Please refer to Figures 1 to 9 In one specific embodiment, a non-contact processing method for a semiconductor workpiece slot includes the following steps:

[0039] S10. Workpiece pretreatment: The semiconductor workpiece blank with resistivity meeting the requirements is processed to a preset thickness, and the outer diameter, inner diameter and solt groove steps of the semiconductor workpiece are rough processed, and a processing reference surface is set to obtain the pretreated semiconductor workpiece.

[0040] S20. Workpiece clamping: The pre-treated semiconductor workpiece is clamped and fixed by a vacuum adsorption fixture 100 to avoid mechanical clamping stress, and the vacuum adsorption fixture 100 is adjusted to keep the processing surface of the pre-treated semiconductor workpiece parallel to the horizontal plane;

[0041] S30. Processing environment setup: Immerse the vacuum adsorption fixture 100, which adsorbs the pretreated semiconductor workpiece, in electrical discharge machining oil;

[0042] S40. Multi-stage electrical discharge machining: The composite electrode 200 is clamped on the spindle of the electrical discharge machine tool, and the composite electrode 200 is controlled to feed along the Z-axis and cooperate with the rocking motion. According to the set machining reference face, non-contact electrical discharge machining is performed on the solt groove of the pre-treated semiconductor workpiece immersed in electrical discharge machining oil. The non-contact electrical discharge machining includes three stages of roughing, semi-finishing and finishing of the solt groove in sequence. During the machining process, the pre-treated semiconductor workpiece is continuously flushed with oil and the machining area is circulated and cooled.

[0043] S50. Online detection and compensation: The depth, length and width of the groove processed during the multi-stage electrical discharge machining process are measured in real time. The Z-axis feed depth and electrode oscillation are dynamically adjusted based on the real-time measured depth, length and width of the groove. After the machining is completed, the final dimension is detected. If the dimension exceeds the tolerance, the process returns to step S40 for compensation. If the dimension does not exceed the tolerance, the processed semiconductor workpiece is obtained.

[0044] The specific steps of the method provided in this embodiment are as follows:

[0045] First, the semiconductor workpiece (P-type polycrystalline silicon semiconductor material) blank is pre-shaped using processes such as grinding or laser cutting to achieve the preset final thickness, ensuring that the semiconductor workpiece blank meets the adsorption requirements of the vacuum adsorption fixture 100. Simultaneously, its outer diameter, inner diameter, and the stepped areas where the Solt groove needs to be machined are rough-machined to allow for subsequent EDM finishing, and a machining reference surface is set to provide a unified dimensional and positional reference for all subsequent machining. Then, the pre-treated semiconductor workpiece is placed on the specially designed vacuum adsorption fixture 100, and the negative pressure generated by the vacuum adsorption fixture firmly adsorbs the pre-treated semiconductor workpiece onto it. Traditional mechanical clamping (such as vises and clamping plates) generates concentrated stress, which can easily lead to microcracks or even breakage in brittle semiconductor materials (such as silicon, silicon carbide, and special ceramics). Vacuum adsorption achieves a large-area, uniform clamping force, avoiding mechanical stress and ensuring the stability and integrity of the semiconductor workpiece during processing. Finally, the entire vacuum adsorption fixture 100 is completely immersed in EDM oil. Electrical discharge machining (EDM) oil is an insulating medium. A pulse voltage breaks down the oil, creating a discharge channel. After the discharge, the oil rapidly cools and washes away the molten metal (achieved through flushing). Examples include high flash point EDM oils. "High flash point" means the oil is not easily flammable, ensuring safety during the machining process. The pre-manufactured composite electrode 200 is then installed and secured to the spindle chuck of the EDM machine tool. The composite electrode 200 on the spindle is fed towards the workpiece (Z-axis direction), while simultaneously performing a small planar rocking motion (i.e., the electrode moves in a circular or square trajectory within the XY plane). The machining process is divided into three stages: roughing, which uses a large discharge energy and a large amount of agitation to quickly remove most of the material, obtaining the approximate shape of the groove, but with a rough surface and dimensional allowance; semi-finishing, which reduces the discharge energy and agitation to refine the shape and size of the groove, leaving a uniform and minimal allowance for finishing; and finishing, which uses very small discharge energy and minimal agitation (or even no agitation) to finally smooth the sidewalls and bottom surface, achieving the dimensional accuracy and surface finish required by the drawing. The composite electrode 200 does not directly contact the semiconductor workpiece; it relies on the thermal effect of pulsed discharge to erode the material, thus there is no cutting force, and it will not cause stress or chipping on the brittle semiconductor workpiece. The agitation of the composite electrode 200 effectively expands the machining area, and the shape of the composite electrode 200 itself and its agitation trajectory jointly determine the final cavity shape of the semiconductor workpiece. During machining, the semiconductor workpiece is continuously flushed with oil, ensuring that the EDM oil flows continuously and evenly through the discharge gap between the composite electrode 200 and the semiconductor workpiece. Then, the EDM oil is continuously extracted from the machining groove. The EDM oil can be filtered using a filtration system to remove electro-erosion products. Then, it is cooled by a constant temperature device to precisely control its temperature at 25±0.5℃ before being returned to the machining tank for continued use.After each machining operation, the machine tool automatically replaces a 1mm diameter conductive standard centering ball. This ball makes electrical contact with the machined groove walls and bottom (a slight contact activates the circuit and generates a signal), allowing the machine to "sense" and measure the current groove depth, length, and width in real time, much like a coordinate measuring machine (CMM). The real-time measurement data can be compared with theoretical data (the target machining dimensions). If deviations exist, the CNC system can automatically and dynamically adjust the feed depth along the electrode's Z-axis and the electrode's wiggle motion for compensation. After all machining is complete, a more precise CMM or image measuring instrument is used for final inspection. If dimensional deviations are found, compensation values ​​can be precisely set based on the inspection data, and compensation machining can be performed until the dimensions are completely acceptable.

[0046] In the aforementioned non-contact processing method for semiconductor workpiece slots, vacuum adsorption clamping and electrical discharge machining (EDM) are employed to avoid damage to the workpiece caused by mechanical contact, thus improving the quality of the semiconductor workpiece. The processing environment setup and circulating cooling ensure the stability of the processing, reducing processing errors caused by environmental factors and heat accumulation. In multi-stage EDM, an electrical discharge is generated between the composite electrode and the semiconductor workpiece; the instantaneous high temperature causes localized melting and vaporization of the workpiece material, thereby achieving material removal and improving processing efficiency. This application integrates processing, measurement, and compensation, significantly improving product quality and consistency in mass production, and preventing semiconductor workpiece scrap due to process instability. As demonstrated by the following examples, compared with traditional machining methods, the method provided in this application reduces the surface roughness of semiconductor workpieces from less than Ra3.2μm to less than Ra1.6μm, and there are no obvious tool marks on the surface of the semiconductor workpiece. The damage layer in the groove is reduced from 20μm-50μm to 1μm-5μm, which is a significant reduction. The quality is higher, the service life is improved, and the processing efficiency is increased from 52H / piece to 12H / piece, which greatly shortens the processing time and improves the production efficiency.

[0047] The semiconductor workpiece is a P-type polycrystalline silicon semiconductor material with a resistivity of ≤4Ω·cm. If the resistivity is greater than 4Ω·cm, the conductivity is poor. Therefore, the conductivity of the semiconductor workpiece cannot exceed 4Ω·cm.

[0048] In a specific embodiment, the specific parameters for the three stages of roughing, semi-finishing, and finishing in step S40 above are as follows:

[0049] Roughing stage: Using parameters of 100μs pulse width, 10A peak current, and positive polarity, the discharge time is 500ms, leaving a 0.2mm margin for the groove depth. Under these parameters, the single discharge energy is large, which can remove a large amount of workpiece material and quickly form the basic outline and depth of the solder groove, laying the foundation for subsequent processing. Processing stops when there is still 0.2mm left to the final depth. This margin is to ensure that there is enough material for semi-finishing and finishing to repair the rough surface and defect layer generated by roughing.

[0050] During pulsed discharge, the positive electrode receives more energy than the negative electrode (approximately 1 / 3 of the energy is in the negative electrode and 2 / 3 in the positive electrode). The positive polarity (the workpiece is the positive electrode and the electrode is the negative electrode) results in a higher material removal rate for the semiconductor workpiece (positive electrode), thereby improving processing efficiency.

[0051] Semi-finishing stage: Using parameters such as pulse width of 80μs, peak current of 8A, and positive polarity, the discharge time is 300ms. The machining taper is controlled to be less than 0.01°. The rough surface and dimensional errors left by roughing are repaired, and the allowance is gradually reduced to create a more uniform substrate that is closer to the final shape for finishing. Compared with roughing, the discharge energy is reduced, the single discharge pit is smaller, and the surface quality is improved.

[0052] In the finishing stage, a high-frequency pulse parameter of 15μs pulse width and 2A peak current is used, with a discharge time of 200ms. This results in a surface roughness Ra≤1.6μm and a groove width tolerance of ±0.01mm. The extremely short pulse width and low current in this stage ensure that a single discharge produces only a very small pit. The short pulse interval also greatly increases the number of discharges (frequency) per unit time. Countless tiny, high-frequency discharge pits overlap, which is equivalent to a kind of "micro-polishing" on the workpiece surface, resulting in a very smooth surface.

[0053] In a specific embodiment, in step S40 above, at least six rinsing nozzles are used to continuously rinsing the pre-treated semiconductor workpiece with oil. The arrangement of the rinsing nozzles can ensure that the rinsing path completely covers the solt area of ​​the pre-treated semiconductor workpiece. The number of rinsing nozzles is six. The rinsing nozzles can be provided with the EDM machine or provided separately.

[0054] In one specific embodiment, in step S30 above, the level of the electrical discharge machining oil is at least 30 mm above the processing surface of the pretreated semiconductor workpiece, so as to ensure that the electrical discharge machining oil can completely cover the surface of the semiconductor workpiece during the subsequent rinsing process.

[0055] In a preferred embodiment, the tolerance for machining the semiconductor workpiece blank to a preset thickness is controlled within ±0.05mm. Assuming a P-type polycrystalline silicon semiconductor workpiece is to be machined with a final required thickness of 10mm, at this stage, its two surfaces will be ground to 10.05mm (leaving a 0.05mm allowance).

[0056] In one specific embodiment, the vacuum adsorption fixture 100 includes a frame 110, a mounting plate 120, an adsorption ring 130, a suction component 140, and a plurality of support columns 150. One end of each support column 150 is connected to the frame 110, and the other end of each support column 150 passes through the mounting plate 120 and is connected to the adsorption ring 130. The plurality of support columns 150 are evenly distributed along the circumference of the adsorption ring 130. The adsorption ring 130 has a hollow structure. The suction component 140 is disposed on the outer wall of the adsorption ring 130 and can suction air into the center of the adsorption ring 130. The air intake section is equipped with several adsorption holes on the inner wall of the adsorption ring 130. The mounting plate 120 is connected to the adsorption ring 130. An annular boss 131 is provided on the side of the mounting plate 120 connected to the adsorption ring 130. An adsorption groove 132 is provided between the annular boss 131 and the inner wall of the adsorption ring 130. The semiconductor workpiece to be processed can be placed on the adsorption groove 132. A connector 111 is also provided at the bottom of the frame 110 for connecting to the EDM machine. Holes are provided in the middle area of ​​both the frame 110 and the mounting plate 120 to reduce weight and fix them as a whole to the worktable of the EDM machine.

[0057] In this embodiment, the vacuum adsorption fixture 100 is installed onto the worktable of the EDM machine via the connector 111 at the bottom of the frame 110, ensuring a stable connection. The connector 111 can be a T-shaped slider, and the worktable of the EDM machine generally has a T-shaped groove, thus achieving the connection between the two. The semiconductor workpiece to be processed is placed in the adsorption groove 132 formed by the mounting plate 120 and the adsorption ring 130. The suction device 140 (such as a vacuum pump or negative pressure generator) is turned on, and air is drawn from the hollow cavity of the adsorption ring 130 through the suction port on the outer wall of the adsorption ring 130, forming a negative pressure. The negative pressure is transmitted to the bottom edge of the workpiece through multiple adsorption holes on the inner wall of the adsorption ring 130, generating a uniform adsorption force and stably fixing the pre-treated semiconductor workpiece.

[0058] By replacing mechanical clamping with vacuum adsorption, cracks, stress, or surface scratches caused by clamping force are avoided, making it especially suitable for brittle semiconductor materials (such as silicon wafers and silicon carbide).

[0059] Furthermore, a plurality of lifting mechanisms 160 are provided between the frame 110 and the adsorption ring 130. One end of each lifting mechanism 160 is connected to the frame 110, and the other end is connected to the adsorption ring 130. These mechanisms are used to adjust the height of the adsorption ring 130 to keep the processing surface of the semiconductor workpiece parallel. The surface of the semiconductor workpiece may not be smooth enough, affecting processing accuracy. In this embodiment, by specifically adjusting the local height of the adsorption ring 130, the processing surface of the semiconductor workpiece is kept parallel to the horizontal plane.

[0060] In one specific embodiment, the composite electrode 200 includes an ER chuck 210, a stainless steel reinforcing plate 220, a graphite bending-resistant portion 230, a graphite forming feature portion 240, a positioning post 250, and a plurality of drainage holes 260. The upper end of the ER chuck 210 is connected to the spindle of an EDM machine tool, and the lower end of the ER chuck 210 is connected to the graphite bending-resistant portion 230. The graphite bending-resistant portion 230 is connected to one side of the stainless steel reinforcing plate 220. The graphite forming feature portion 240 is disposed on the other side of the stainless steel reinforcing plate 220, and its shape (ring-shaped) is consistent with the negative shape of the slot to be processed. The drainage holes 260 are formed through the stainless steel reinforcing plate 220, and the positioning post 250 is disposed on the stainless steel reinforcing plate 220. When the graphite forming feature portion 240 is ring-shaped, the positioning post 250 is disposed at the center of the graphite forming feature portion 240.

[0061] Since the annular graphite forming feature 240 requires a large amount of graphite, the cost is too high, and the discharge area is too large, which will result in poor effect and slow processing speed. In a preferred embodiment, the graphite forming feature 240 can be set as a semi-annular shape to reduce cost and improve efficiency. When processing one half of the semiconductor workpiece, the graphite forming feature 240 can be flipped over to process the other side of the semiconductor workpiece. When the graphite forming feature 240 is semi-annular, the positioning post 250 is set at the midpoint between the two ends of the graphite forming feature 240.

[0062] The upper end of the ER chuck 210 is securely clamped in the spindle sleeve of the EDM machine. The positioning system of the EDM machine aligns the positioning pin 250 with the predetermined reference surface on the semiconductor workpiece to be processed, ensuring that the graphite forming feature 240 on the composite electrode 200 is precisely aligned with the position to be processed on the semiconductor workpiece. During operation, the machine spindle drives the entire composite electrode 200 downward to gradually approach the surface of the semiconductor workpiece. Pulse discharge is generated in the environment filled with high EDM oil between the two. The high temperature generated by the discharge instantly erodes the material of the semiconductor workpiece. Its shape is determined by the shape of the graphite forming feature 240 (i.e., the negative shape of the solt groove), thereby machining the required solt groove structure on the semiconductor workpiece.

[0063] The ER chuck 210 provides a rigid base for connection to the machine tool. The high strength and rigidity of the stainless steel reinforcing plate 220 effectively resist various forces generated during the discharge process, greatly reducing electrode vibration and deformation. If the electrode does not have sufficient rigidity, it will vibrate during processing, resulting in an increased solt width and distorted shape. Graphite material has good mechanical strength and resistance to electrical corrosion. The graphite anti-bending part 230 connects the stainless steel plate and the ER chuck 210, further enhancing the overall bending resistance of the electrode and ensuring that it will not bend due to lateral forces during deep groove processing. The graphite forming feature part 240 is manufactured as a mirror image (negative shape) of the target solt groove and is directly responsible for forming. It can form the entire solt groove in one go, instead of using a single small electrode to scan back and forth multiple times, resulting in extremely high processing efficiency. The drain hole 260 solves the problem of difficult chip removal during deep groove processing, avoiding problems such as processing instability, arc burns, and reduced efficiency caused by poor chip removal, significantly improving processing speed, surface quality, and electrode life.

[0064] During prolonged electrical discharge machining (EDM), the composite electrode 200 itself undergoes electro-erosion wear, resulting in a slight decrease in size. Continued use of this worn-out electrode 200 can lead to quality issues in the machined solder groove, such as smaller dimensions, rounded groove openings, and unclear corners. In a preferred embodiment, after the cumulative machining time of the composite electrode 200 reaches 72 hours, a surface rework is required. During rework, a milling cutter with at least four cutting edges and a diameter slightly larger than the groove width is used, cutting along the length of the graphite forming feature 240. The depth of cut is controlled to within 0.1 mm, and the feed rate is controlled to within 1000 mm / min. By periodically (every 72 hours) performing mandatory rework on the composite electrode 200, the original geometry and dimensions of the composite electrode 200 are restored, thereby ensuring the machining accuracy of the solder groove on each semiconductor workpiece and avoiding batch quality deviations caused by electrode wear.

[0065] Because the electro-corrosion process generates toxic and harmful organic compounds such as carbon monoxide and alkanes at high temperatures, further safety and environmental protection measures are included: the semiconductor workpiece is processed in a fully enclosed protective cover, with a fume treatment device connected to the outside of the cover, and a carbon monoxide gas detection alarm device is installed.

[0066] The following specific experimental examples further illustrate the technical solution and effects of the present invention. It should be noted that the following experimental examples are only for further explanation of the present invention and do not limit the technical solution of the present invention. Example

[0067] A P-type polycrystalline silicon semiconductor material with a resistivity of 0.014 Ω·cm is used as the semiconductor workpiece to be processed. The dimensions of the processed solt groove are: length 52mm × width 2.5mm × depth 8mm. The blank is processed to a preset thickness with a tolerance controlled within ±0.05mm. The outer diameter, inner diameter, and solt groove steps of the semiconductor workpiece are rough-machined, and a machining reference surface is set. The pre-processed semiconductor workpiece is placed on the adsorption groove 132 of the vacuum adsorption fixture 100, and the suction is controlled. Air is drawn out, creating negative pressure in the cavity within the adsorption ring 130, which adsorbs the semiconductor workpiece to be processed onto the adsorption tank 132. The semiconductor workpiece is then immersed in electrical discharge machining (EDM) oil, with the oil level exceeding the processing surface by 30mm. Six oil spray nozzles are activated to ensure the oil covers the entire processing area. The composite electrode 200 (graphite forming feature 240 is a semi-ring) is clamped onto the EDM machine spindle via the ER chuck 210. The composite electrode 200 is controlled to feed along the Z-axis and engages in a rocking motion to perform non-contact EDM machining on the workpiece's slot, sequentially performing roughing and semi-finishing. The machining process consists of three stages: roughing, semi-finishing, and finishing. The roughing stage uses a pulse width of 100μs, a peak current of 10A, and positive polarity, with a discharge time of 500ms, leaving a 0.2mm allowance for the groove depth. The semi-finishing stage uses a pulse width of 80μs, a peak current of 8A, and positive polarity, with a discharge time of 300ms, controlling the machining taper to less than 0.01°. The finishing stage uses a high-frequency pulse parameter of 15μs pulse width and a peak current of 2A, with a discharge time of 200ms. Ultimately, the surface roughness Ra of the groove is ≤1.6μm, and the groove width tolerance reaches ±0.01mm. During the process, electrical discharge machining (EDM) oil is used to circulate and cool the machining area, with the oil temperature controlled at 25±0.5℃. A 1mm diameter standard centering ball made of conductive material is used to measure the depth, length, and width of the machined groove in real time using a conductive path feedback mechanism. Based on the real-time measurements of the groove depth, length, and width, the Z-axis feed depth and electrode yaw are dynamically adjusted by the CNC system. After machining, the final dimensions are automatically measured by a coordinate measuring system and an image measuring system. If the dimensions exceed the tolerance, compensation machining is performed to obtain the machined semiconductor workpiece. The various indicators are shown in Table 1. It should be noted that in this embodiment, after the composite electrode 200 has been machined for 72 hours, a smooth surface rework is performed. During rework, a four-flute or higher milling cutter slightly larger than the groove width is used to feed along the groove length, ensuring that the cutting depth per cut is less than 0.1mm and the feed rate is less than 1000mm / min.

[0068] Comparative Example

[0069] P-type polycrystalline silicon semiconductor material with a resistivity of 0.014 Ω·cm was processed using traditional machining methods, such as grinding. The dimensions of the processed slot were 52 mm long × 2.5 mm wide × 8 mm deep. The various parameters are shown in Table 1.

[0070] Table 1. Comparison of various indicators of the processed semiconductor workpieces in the Examples and Comparative Examples

[0071]

[0072] The data in Table 1 show that, compared with the comparative example, the surface roughness of the workpiece in the embodiment is reduced from less than Ra3.2μm to less than Ra1.6μm, and there are no obvious tool marks on the workpiece surface. The damage layer in the groove is reduced from 20μm-50μm to 1μm-5μm, which is a significant reduction. It can be seen that the product quality in the embodiment is high and the service life is improved. On the other hand, the processing efficiency is increased from 52H / piece to 12H / piece, which greatly shortens the processing time and improves the production efficiency.

[0073] In addition, compared with the comparative example, the tool wear in the embodiment was reduced from 2,000 yuan / piece to 800 yuan / piece, which reduced production costs and improved dimensional stability.

[0074] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A non-contact processing method for a semiconductor workpiece slot, characterized in that, Includes the following steps: S10. Workpiece pretreatment: The semiconductor workpiece blank with resistivity meeting the requirements is processed to a preset thickness, and the outer diameter, inner diameter and solt groove steps of the semiconductor workpiece are rough processed, and a processing reference surface is set to obtain the pretreated semiconductor workpiece. S20. Workpiece clamping: The pre-treated semiconductor workpiece is clamped and fixed by a vacuum adsorption fixture to avoid mechanical clamping stress, and the vacuum adsorption fixture is adjusted to keep the processing surface of the pre-treated semiconductor workpiece parallel to the horizontal plane; S30. Processing environment setup: Immerse the vacuum adsorption fixture with the pretreated semiconductor workpiece in electrical discharge machining oil; S40. Multi-stage electrical discharge machining: The composite electrode is clamped on the spindle of the electrical discharge machine tool, and the composite electrode is controlled to feed along the Z-axis and cooperate with the rocking motion. According to the set machining reference face, non-contact electrical discharge machining is performed on the solt groove of the pre-treated semiconductor workpiece immersed in electrical discharge machining oil. The non-contact electrical discharge machining includes three stages of roughing, semi-finishing and finishing of the solt groove in sequence. During the machining process, the pre-treated semiconductor workpiece is continuously flushed with oil and the machining area is circulated and cooled. S50. Online detection and compensation: The depth, length and width of the groove processed during the multi-stage electrical discharge machining process are measured in real time. The Z-axis feed depth and electrode oscillation are dynamically adjusted based on the real-time measured depth, length and width of the groove. After the machining is completed, the final dimension is detected. If the dimension exceeds the tolerance, the process returns to step S40 for compensation. If the dimension does not exceed the tolerance, the processed semiconductor workpiece is obtained.

2. The non-contact processing method for semiconductor workpiece slots according to claim 1, characterized in that, The semiconductor workpiece to be processed is a P-type polycrystalline silicon semiconductor material with a resistivity ≤ 4Ω·cm.

3. The non-contact processing method for semiconductor workpiece slots according to claim 1, characterized in that, In step S40, the specific parameters for the three stages of roughing, semi-finishing, and finishing are as follows: Rough machining stage: Use parameters with a pulse width of 100μs, a peak current of 10A, and positive polarity, with a discharge time of 500ms, and machine to a depth of 0.2mm. Semi-finishing stage: Using parameters such as pulse width of 80μs, peak current of 8A, and positive polarity, the discharge time is 300ms, and the machining taper is controlled to be less than 0.01°; In the finishing stage, a high-frequency pulse parameter of 15μs pulse width and 2A peak current is used, with a discharge time of 200ms, to achieve a surface roughness Ra≤1.6μm and a groove width tolerance of ±0.01mm.

4. The non-contact processing method for semiconductor workpiece slots according to claim 1, characterized in that, In step S40, at least six rinsing nozzles are used to continuously rinsing the pre-treated semiconductor workpiece with oil. The arrangement of the rinsing nozzles ensures that the rinsing path completely covers the solt area of ​​the pre-treated semiconductor workpiece.

5. The non-contact processing method for semiconductor workpiece slots according to claim 1, characterized in that, In step S30, the level of the electrical discharge machining oil is at least 30 mm above the processing surface of the pretreated semiconductor workpiece.

6. The non-contact processing method for semiconductor workpiece slots according to claim 1, characterized in that, When the semiconductor workpiece blank is processed to a preset thickness, the tolerance is controlled within ±0.05mm.

7. The non-contact processing method for semiconductor workpiece slots according to claim 2, characterized in that, The vacuum adsorption fixture includes a frame, a mounting plate, an adsorption ring, a suction component, and several support columns. One end of each support column is connected to the frame, and the other end passes through the mounting plate and connects to the adsorption ring. The support columns are evenly distributed around the circumference of the adsorption ring. The adsorption ring is a hollow structure. The suction component is located on the outer wall of the adsorption ring and can draw air into the hollow part of the adsorption ring. Several adsorption holes are formed on the inner wall of the adsorption ring. The mounting plate is connected to the adsorption ring. An annular boss is provided on the side of the mounting plate connected to the adsorption ring. An adsorption groove is formed between the annular boss and the inner wall of the adsorption ring. The semiconductor workpiece to be processed can be placed in the adsorption groove. A connector is also provided at the bottom of the frame for connecting to an EDM machine.

8. The non-contact processing method for semiconductor workpiece slots according to claim 7, characterized in that, Several lifting mechanisms are also provided between the frame and the adsorption ring. One end of the lifting mechanism is connected to the frame, and the other end of the lifting mechanism is connected to the adsorption ring. These mechanisms are used to adjust the height of the adsorption ring so that the processing surface of the semiconductor workpiece to be processed remains parallel to the horizontal plane.

9. The non-contact processing method for semiconductor workpiece slots according to claim 2, characterized in that, The composite electrode includes an ER chuck, a stainless steel reinforcing plate, a graphite bending section, a graphite forming feature section, a positioning post, and several drainage holes. The upper end of the ER chuck is connected to the spindle of the EDM machine tool, and the lower end of the ER chuck is connected to the graphite bending section. The graphite bending section is connected to one side of the stainless steel reinforcing plate, and the graphite forming feature section is located on the other side of the stainless steel reinforcing plate. Its shape is consistent with the negative shape of the slot to be processed. The drainage holes are opened through the stainless steel reinforcing plate, and the positioning post is located on the stainless steel reinforcing plate.

10. The non-contact processing method for semiconductor workpiece slots according to claim 9, characterized in that, After the cumulative processing time of the composite electrode reaches 72 hours, a smooth surface rework is required. During the rework, a milling cutter with no less than four cutting edges and a diameter slightly larger than the groove width is used to cut along the length direction of the graphite forming feature. The depth of cut in a single cut is controlled within 0.1 mm, and the feed rate is controlled within 1000 mm / min.

Images