Processing method of ultrathin wafer tray

Abstract

The invention provides a processing method of a wafer tray, and belongs to the technical field of wafer manufacturing. Comprising the following steps that S1, double-face LAP grinding is conducted on a wafer tray blank material, and the wafer tray blank material is made of a monocrystalline silicon material homologous with a wafer material; s2, outer diameter machining and outer diameter chamfering are carried out on the wafer tray blank; s3, the reverse side of the wafer tray blank material is polished, and a wafer groove face and a reserved groove are machined in the wafer tray blank material; s4, performing sand blasting on the upper surface of the wafer tray blank material; s5, mixed acid is adopted to etch the wafer tray blank material after sand blasting; and S6, polishing the wafer groove surface of the etched wafer tray blank material by using a polishing machine. By setting specific process steps and equipment parameters and adding sand blasting and polishing, the roughness, parallelism and planeness of the surface of the wafer tray are reduced, and no warping phenomenon is generated after the wafer tray is processed.

Description

Technical Field

[0001] The invention relates to the technical field of wafer manufacturing, and in particular to a processing method for an ultra-thin wafer tray. Background Art

[0002] In semiconductor processing, physical vapor deposition is a commonly used method for coating the surface of wafers. It uses particles to bombard the surface of the target material, so that the atoms or molecules on the surface of the target material escape from the surface of the target material and are coated on the wafer. During the coating process, the wafer is usually fixed on a wafer tray. If the surface of the wafer tray is rough or uneven, it is easy to cause the wafer to tilt, resulting in uneven coating on the surface of the wafer, thereby reducing the quality of the wafer and affecting the use of the wafer.

[0003] In the prior art, for example, the Chinese invention with application number CN201711460079.6 specifically discloses a wafer tray processing method, which uses an aluminum alloy turning tool to rough-process the tray surface, which can improve the processing efficiency of the tray; uses a boron nitride turning tool to semi-finish the tray surface, which can make the tray have a relatively good processing accuracy; uses a diamond turning tool to finish the tray surface, which can make the tray surface smoother and have better surface roughness, thereby obtaining a very flat surface. However, the wafer tray of this patent is made of titanium or titanium alloy, which is a material that is not derived from silicon wafers, and is prone to causing problems such as contamination of the wafer. Single-crystal silicon wafers, which are derived from the same material as silicon wafers, have become a better choice for making wafer trays, but single-crystal silicon materials are brittle, and are prone to fragmentation and warping during the mechanical processing and circulation of wafer trays with a thickness of less than 1.5 mm. Summary of the invention

[0004] In view of this, the present invention provides a method for processing an ultra-thin wafer tray to solve the technical problem that silicon wafer trays with a thickness of less than 1.5 mm are prone to cracking and warping during mechanical processing and circulation.

[0005] The technical solution adopted by the present invention to solve its technical problem is: A method for processing an ultra-thin wafer tray comprises the following steps: S1. Performing double-sided LAP grinding on a wafer tray blank, wherein the wafer tray blank is made of a single crystal silicon material having the same origin as the wafer material; S2, performing outer diameter processing and outer diameter chamfering on the wafer tray blank; S3, polishing the back surface of the wafer tray blank, and processing the wafer groove surface and the reserved groove on the wafer tray blank; S4, sandblasting the upper surface of the wafer tray blank; S5, etching the wafer tray blank after sandblasting by using mixed acid; S6. Polishing the wafer groove surface of the etched wafer tray blank using a polishing machine.

[0006] Preferably, in step S1, the flat-ground blank is ground using double-sided grinding equipment and 1000-mesh LAP powder.

[0007] Preferably, in step S2, the outer diameter processing and outer diameter chamfering of the wafer tray blank are performed by the following steps: S21, bonding on the machine: Bond the wafer tray blank to the quartz plate, place the quartz plate on the machine tool working platform and use a dial indicator to level it, ensuring that the parallelism between the quartz plate surface and the machine tool working table is within 0.05mm; S22, outer diameter chamfering: use a diamond grinding milling tool with a metal base of 30-60mm in diameter, use horizontal arc feed, feed angle of 10-20°, feed arc size of R15-30mm, feed speed of 300-500mm / min, step distance of 0.01-0.02mm, speed of 4500-6500 rpm; after feed is completed, other parameters remain unchanged during chamfering, and feed speed is increased to 1000-1500mm / min; S23, outer diameter processing: When processing the outer diameter after chamfering, other parameters remain unchanged, and the step down distance is increased to 0.03mm-0.06mm.

[0008] Preferably, in step S3, when polishing the back side of the wafer tray blank, first use a 200-300 mesh metal-based diamond tool to perform a rough polishing of 0.8-0.9 mm, and then use a 450-550 mesh resin-based diamond tool to perform a fine polishing of 0.04-0.05 mm, leaving a 0.05 mm margin for subsequent sandblasting and etching.

[0009] Preferably, in step S3, the following steps are used to process the wafer groove surface and the reserved groove on the wafer tray blank: a. Rough machining of the wafer groove surface: Use a 100-200 mesh diamond tool with a metal base of less than 30mm in diameter to roughen the wafer groove surface. The tool feed adopts vertical arc feed, the feed angle is 3-5°, the feed speed is 50-100mm / min, and the feed arc is R10-15mm; the tool speed is 6500-7500mm / min, the feed step is 0.01-0.02mm, and the feed speed is 100-300mm / b. Processing the reserved groove: Use a 2-4mm metal matrix diamond 250-350 mesh tool to process the reserved groove. The tool feed adopts horizontal arc feed, the feed angle is 10-15°, the feed speed is 50-100mm / min, the feed arc is R2-5mm, the tool speed is 8500-9500mm / min, the feed step is 0.01-0.02mm, and the feed speed is 100-200mm / min; c. Finishing the wafer groove surface: Use a resin-based diamond tool with a mesh size of 1000 or above to finish the wafer groove surface. The tool diameter is 1-2mm smaller than the diameter of the wafer groove surface. The tool feed adopts vertical arc feed, the feed angle is 3-5°, the feed speed is 50-100mm / min, the feed arc is R10-15mm, the tool speed is 6500-7500mm / min, the feed step is 0.005-0.01mm, and the feed speed is 100-200mm / min.

[0010] Preferably, in step S4, a sandblasting machine is used to firstly perform rough sandblasting on the wafer tray blank using 150-250 mesh pomegranate sand, and then perform fine sandblasting on the wafer tray blank using 450-550 mesh pomegranate sand, and the sandblasting amount is 0.03-0.04 mm.

[0011] Preferably, in step S5, for a single crystal with a resistance of 0.005-0.02, the mixed acid is composed of HF 49%: HNO3 70%: CH3COOH 99%, with a ratio of 1-2: 8-10: 3-5, the etching time for a single product is 15-20s, the etching temperature is 20°C, and the etching amount of the upper and lower surfaces is 0.01mm per side.

[0012] Preferably, in step S5, for a single crystal with a resistance of 1-4, the mixed acid is composed of HF 49%: HNO3 70%: CH3COOH 99%, with a ratio of 3-5: 8-10: 3-5, the etching time for a single product is 15-20s, the etching temperature is 20°C, and the etching amount of the upper and lower surfaces is 0.01mm per side.

[0013] Preferably, in step S6, the polishing pad of the polishing machine performs X-axis reciprocating movement to polish the wafer groove surface of the wafer tray blank after the etching.

[0014] Preferably, in step S6, the silicon wafer is bonded to the wafer tray blank, and the silicon wafer is clamped by negative pressure suction, so as to clamp the wafer tray blank on the polishing machine.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses a single crystal silicon material homologous to the wafer material to make a wafer tray blank, thereby avoiding the problem of metal contamination caused by the wafer tray to the wafer; at the same time, the corresponding processing technology is matched, firstly, the mechanical damage layer and knife marks caused by the flat grinding process are removed by double-sided LAP grinding, and the roughness of the surface of the wafer tray blank is reduced, and then the wafer groove surface and the reserved groove of the wafer tray are processed, and the mechanical processing damage layer of the wafer tray is removed by using a special sandblasting process and an etching process, and finally the wafer tray is polished by a polishing machine to further reduce the roughness and flatness of the wafer tray. The wafer tray obtained by the present invention has a bottom surface and a wafer surface roughness of less than Ra0.4 and Ra0.1 respectively, the parallelism of the wafer surface and the bottom surface is within 0.05mm, the flatness of the wafer surface is within 0.03mm, and no warping phenomenon occurs after the wafer tray is processed. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a flowchart of a method for processing an ultra-thin wafer tray.

[0017] Figure 2 The figure is a schematic diagram of the structure of an ultra-thin wafer tray.

[0018] Figure 3 A schematic diagram of the structure of another ultra-thin wafer tray.

[0019] Figure 4 It is a schematic diagram of the structure of the groove stopper.

[0020] Figure 5 Process roadmap for ultra-thin wafer trays.

[0021] In the figure: an ultra-thin wafer tray 10 , an upper surface 11 , a wafer groove surface 12 , and a reserved groove 13 . DETAILED DESCRIPTION

[0022] The technical solutions and technical effects of the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings of the present invention.

[0023] Please see Figure 1 , a method for processing an ultra-thin wafer tray, comprising the following steps: S1. Performing double-sided LAP grinding on a wafer tray blank, wherein the wafer tray blank is made of a single crystal silicon material having the same origin as the wafer material; S2, performing outer diameter processing and outer diameter chamfering on the wafer tray blank; S3, polishing the back surface of the wafer tray blank, and processing the wafer groove surface and the reserved groove on the wafer tray blank; S4, sandblasting the upper surface of the wafer tray blank; S5, etching the wafer tray blank after sandblasting by using mixed acid; S6. Polishing the wafer groove surface of the etched wafer tray blank using a polishing machine.

[0024] The present invention adopts a single crystal silicon material homologous to the wafer material to make a wafer tray blank, thereby avoiding the problem of metal contamination caused by the wafer tray to the wafer; at the same time, the corresponding processing technology is matched, firstly, the mechanical damage layer and knife marks caused by the flat grinding process are removed by double-sided LAP grinding, and the roughness of the surface of the wafer tray blank is reduced, and then the wafer groove surface and the reserved groove of the wafer tray are processed, and the mechanical processing damage layer of the wafer tray is removed by using a special sandblasting process and an etching process, and finally the wafer tray is polished by a polishing machine to further reduce the roughness and flatness of the wafer tray. The present invention sets specific process steps, equipment parameters and increases mechanical chemical polishing to ensure that the wafer tray has a very low probability of non-human factors during processing. The roughness of the bottom surface and the wafer surface of the wafer tray is respectively below Ra0.4 and Ra0.1, the parallelism of the wafer surface and the bottom surface is within 0.05mm, the flatness of the wafer surface is within 0.03mm, and no warping phenomenon occurs after the wafer tray is processed.

[0025] Among them, the structure of the ultra-thin wafer tray made by the present invention is as follows Figure 2 , Figure 3 As shown, its thickness is 1mm, the distance from the wafer surface to the upper surface 11 (i.e., the depth of the wafer groove surface 12) is 0.4mm, and the depth of the reserved groove 13 next to the wafer surface for grabbing the wafer is 0.65mm. Therefore, the thinnest part of the wafer tray is only 0.35mm, wherein the reserved groove 13 includes an annular groove surrounding the wafer groove surface, and a semicircular groove connected to the annular groove.

[0026] In some embodiments, a wafer tray blank is first made of single crystal silicon material. Specifically, in the single crystal pulling process, the slip defect and resistivity parameters are controlled by designing the thermal field structure and widening the crystal growth process window, so as to pull a single crystal without slip dislocation. The silicon crystal rod is then mechanically processed by truncation, rolling, and multi-wire cutting to be processed into the disc shape required by the wafer tray, and then the surface cutting marks caused by wire cutting are removed by plane grinding and the surface mechanical damage and microcracks are reduced, so that the wafer tray blank thickness is ground to 2.2mm by plane grinding, the parallelism is processed to 0.09-0.15mm, and the flatness is processed to 0.05-0.11mm. At this point, the wafer tray blank is completed and the binocular LAP grinding process begins.

[0027] In the specific implementation process, double-sided grinding equipment is used to grind the blank after flat grinding with 1000 mesh LAP powder. The parallelism and flatness of the double-sided grinding equipment are better than those of the single-sided flat grinding equipment. The mechanical damage layer and knife marks caused by the flat grinding process can be removed by double-sided LAP grinding. The surface appearance after grinding is good and there is no color difference. The surface roughness of the wafer tray blank after LAP powder grinding can reach below Ra0.4. After double-sided LAP grinding, the flatness of the wafer tray blank is within 0.03mm, and the parallelism is within 0.06mm. Among them, double-sided LAP grinding removes 0.1mm on one side. This is because if the wafer tray blank is ground to less than 2mm using double-sided grinding equipment, it is easy to break during the grinding process.

[0028] In the specific implementation process, the following steps are used to process the outer diameter and chamfer the outer diameter of the wafer tray blank: S21, bonding on the machine: Bond the wafer tray blank to the quartz plate, place the quartz plate on the machine tool work platform and use a dial indicator to level it, ensuring that the parallelism between the quartz plate surface and the machine tool work table is within 0.05mm; specifically, select a quartz plate fixture with a flatness within 0.03mm, heat the wafer tray blank and the quartz plate fixture on a heating platform, heat to 120°C, and bond them after the yellow wax melts. After bonding, press the surface of the wafer tray blank and rotate it clockwise to squeeze out the bubbles between the bonding surface of the wafer tray blank and the quartz plate to ensure that the two are tightly bonded. Place the quartz plate on the machine tool work platform and use a dial indicator to level it, ensuring that the parallelism between the quartz plate surface and the machine tool work table is within 0.05mm. If the parallelism is poor, use padding paper to level the quartz plate around and then clamp it. Finally, a dial indicator is used to round the wafer tray blank to determine the machining origin, and the tool height parameters are confirmed using the tool setting block.

[0029] The upper and lower surfaces of the wafer tray blank have been double-sided LAP grinding, so when processing the outer diameter, you need to pay attention to the cutting method and step distance, otherwise broken layers and broken edges will appear on the chamfered edge.

[0030] S22, outer diameter chamfering: use a diamond grinding milling tool with a metal base of 30-60mm in diameter, use horizontal arc feed, feed angle of 10-20°, feed arc size of R15-30mm, feed speed of 300-500mm / min, step distance of 0.01-0.02mm, speed of 4500-6500 rpm; after feed is completed, other parameters remain unchanged during chamfering, and feed speed is increased to 1000-1500mm / min; S23, machining outer diameter: When machining the outer diameter after chamfering, other parameters remain unchanged, and the step down distance is increased to 0.03mm-0.06mm. The tool retraction method adopts horizontal arc retraction to prevent the tool vibration from leaving marks on the outer diameter surface during retraction. After the outer diameter machining is completed, the wafer tray and quartz plate are removed from the machine, and the wafer tray and quartz plate are heated and dewaxed using a heating platform.

[0031] Furthermore, after the outer diameter processing is completed, the wafer tray blank is turned over, and the features of the front side of the wafer tray used to support the wafer are processed, that is, the wafer groove surface and the reserved groove are processed. First, a quartz plate tooling with a flatness of less than 0.03mm is selected, and the back of the wafer tray blank and the quartz plate tooling are heated using a heating platform to 120°C, and the yellow wax is melted and bonded. After the product is bonded, the surface of the product is pressed and rotated clockwise to squeeze out the bubbles between the bonding surface of the wafer tray blank and the quartz plate to ensure that the two are tightly bonded. Place the quartz plate on the working platform of the machine tool and use a dial indicator to level it to ensure that the parallelism between the surface of the quartz plate and the working table of the machine tool is within 0.05mm. If the parallelism is poor, it is necessary to use padding paper to level the quartz plate around, and then clamp it. Finally, use a dial indicator to find the circle of the wafer tray blank to determine the processing work origin, and use the tool setting block to confirm the tool height parameters. After the wafer tray blank is clamped on the machine, the front surface of the wafer tray blank is polished.

[0032] In the specific implementation process, when the wafer tray blank is turned over and polished, it is first rough-polished by a 200-300 mesh metal-based diamond tool to a thickness of 0.8-0.9 mm, and then fine-polished by a 450-550 mesh resin-based diamond tool to a thickness of 0.04-0.05 mm, leaving a 0.05 mm margin for subsequent sandblasting and etching.

[0033] In the specific implementation process, the following steps are used to process the wafer groove surface and the reserved groove on the wafer tray blank: a. Rough machining of the wafer groove surface: Since the wafer tray blank is thin, if a larger tool is used, the cutting travel distance is short, and the tool displacement space is small, which can easily lead to excessive product temperature, difficult chip removal, excessive pressure, and ultimately cause the wafer tray to break and warp. Therefore, a 100-200 mesh diamond tool with a metal base of less than 30mm in diameter is used to roughen the wafer groove surface. The roughing is carried out in the order from the outer circle to the center. The first cut is a full cut, and the outer circle is processed first. The outer circle tool has a large rotation space, and the tool linear speed can meet the cutting requirements. The tool feed adopts vertical arc feed, the feed angle is 3-5°, the feed speed is 50-100mm / min, and the feed arc is R10-15mm; the tool speed is 6500-7500mm / min, the feed step is 0.01-0.02mm, and the feed speed is 100-300mm / min. The tool retraction adopts a spiral ascending retraction method to avoid leaving obvious marks on the workpiece, thereby ensuring the surface processing quality of the workpiece. b. Processing the reserved groove: The reserved groove of the wafer tray is to facilitate the mechanical claw to take the wafer. The width of the groove is generally about 2-5mm, so a 2-4mm metal matrix diamond 250-350 mesh tool is used to process this feature. The tool feed adopts horizontal arc feed, the feed angle is 10-15°, the feed speed is 50-100mm / min, the feed arc is R2-5mm, the tool speed is 8500-9500mm / min, the feed step is 0.01-0.02mm, and the feed speed is 100-200mm / min. The tool retracts in a spiral ascending manner.

[0034] c. Finishing the wafer groove surface: Since the wafer groove surface of the wafer tray directly contacts and carries the wafer, there are high requirements for the parallelism and flatness of this surface. The parallelism has been verified with a dial indicator when the wafer tray is clamped, which can ensure that the parallelism between the back of the wafer tray and the machine tool worktable is kept within 0.05mm, and the Z-axis error of the machine tool is adjusted to 0.004mm. Flatness requires one tool to process the wafer groove surface in one circle. If multiple tools or multiple tools are used, there will be bulges or tool marks at the joint. Therefore, the wafer groove surface is customized with a special smooth tool according to the diameter of the groove surface. The tool uses a resin-based diamond tool with a mesh size of more than 1000, and the tool diameter is less than 1-2mm of the groove circle diameter. The tool feed adopts vertical arc feed, the feed angle is 3-5°, the feed speed is 50-100mm / min, and the feed arc is R10-15mm. The tool speed is 6500-7500mm / min, the cutting step is 0.005-0.01mm, and the feed speed is 100-200mm / min. The tool retracts in a spiral ascending manner.

[0035] Furthermore, after the wafer groove surface and reserved groove of the wafer tray are processed, the outer diameter chamfering needs to be performed. Specifically, the outer diameter is processed using a diamond grinding milling tool with a metal base of 30-60mm in diameter, and the feed adopts a horizontal arc feed, the feed angle is 10-20°, the feed arc size is R15-30mm, the feed speed is 300-500mm / min, the step distance is 0.01-0.02mm, and the rotation speed is 4500-6500 rpm. After the feed is completed, the other parameters remain unchanged during the chamfering process, and the feed speed is increased to 1000-1500mm / min. The retraction method still uses a horizontal arc retraction to prevent the vibration of the tool during retraction from leaving marks on the outer diameter surface.

[0036] Furthermore, after the outer diameter chamfering process is completed, the wafer tray is removed from the machine tool work platform. After being removed from the machine, without dewaxing, a groove stopper is placed in the groove on the surface of the wafer tray to protect the groove surface in the subsequent sandblasting process to avoid damage to the processed groove plane during the sandblasting process. In some embodiments, if there are fewer grooves on the tray (for example, Figure 3 The wafer tray shown in the figure) can be made of yellow wax as a groove stopper and poured into the groove on the surface of the wafer tray. Specifically, the yellow wax can be melted and poured into the groove. After the yellow wax cools, it can act as a groove stopper to protect the wafer groove surface and the reserved groove of the wafer tray. In some embodiments, if there are many grooves on the tray (for example Figure 2 The wafer tray shown in the figure) can be made according to the groove size as shown in the figure. Figure 4 The multiple matching groove stoppers shown are heated by a heating platform and placed in the grooves on the surface of the wafer tray in sequence, thereby protecting the groove surface.

[0037] Furthermore, the present invention adds a sandblasting and etching process for ultra-thin sheets of special single crystal silicon materials, and uses a special sandblasting protective tooling and an etching acid solution ratio scheme to remove the mechanical processing damage layer of the wafer tray.

[0038] In the specific implementation process, in order to eliminate the knife marks on the upper surface and the damaged layer after machining, the wafer tray blank is first coarsely sandblasted with 150-250 mesh pomegranate sand using a sandblasting machine, and then finely sandblasted with 450-550 mesh pomegranate sand, with a sandblasting volume of 0.03-0.04mm. Due to the high intensity of sandblasting, the wafer tray and the quartz plate need to be bonded to prevent the wafer tray from breaking during the sandblasting process.

[0039] Furthermore, after sandblasting, the wafer tray is heated and dewaxed, and the yellow wax and dirt on the wafer tray are removed by boiling and ultrasonic cleaning, and then it is transferred to the etching process for etching. Since the wafer tray is thin, the etching process cannot be carried out using the usual process ratio for etching silicon rings, so a special etching process is set up for thin silicon sheets.

[0040] In the specific implementation process, for single crystals with a resistance of 0.005-0.02, the mixed acid is composed of HF 49%: HNO3 70%: CH3COOH 99%, with a ratio of 1-2: 8-10: 3-5. The etching time for a single product is 15-20s, the etching temperature is 20°C, and the etching amount of the upper and lower surfaces is 0.01mm per side.

[0041] In the specific implementation process, for single crystals with a resistance of 1-4, the mixed acid is composed of HF 49%: HNO3 70%: CH3COOH 99%, with a ratio of 3-5: 8-10: 3-5. The etching time for a single product is 15-20s, the etching temperature is 20°C, and the etching amount on the upper and lower surfaces is 0.01mm per side.

[0042] The wafer groove surface of the etched wafer tray carrying the wafer is mechanically and chemically polished to further reduce the roughness and flatness. Since the wafer tray is thin, it cannot be clamped by side clamping and negative pressure suction. Therefore, a 10mm silicon wafer with good parallelism and flatness is used as a tooling, the wafer tray blank and the silicon wafer are bonded with yellow wax, and then the silicon wafer is clamped by negative pressure suction. Among them, the diameter of the polishing pad to be used is slightly larger than half of the diameter of the groove circle on the wafer groove surface, so that the polishing pad can perform X-axis reciprocating polishing. If the polishing pad is consistent with the groove circle diameter, the center line speed and edge of the polishing pad will be greatly different during the fixed-point polishing process, resulting in poor quality after polishing and bulges in the middle.

[0043] During the specific implementation process, when polishing the wafer groove surface of the etched wafer tray blank, the polishing pad of the polishing machine moves back and forth on the X-axis, the polishing spindle angle is set to 1.5-1.9°, the polishing head pressure is set to 4-8KG, the polishing head speed is 1500-2000 rpm, the reciprocating polishing feed is set to 5-10mm / min, the turntable speed is set to 100-120 rpm, and the polishing time is set to 0.5-0.8H.

[0044] In some embodiments, see Figure 5Polishing and etching need to be processed in a Class 1,000 operating room. After processing, the wafer tray is boiled and cleaned, and then the size is inspected in a Class 100 clearance room. After the inspection is completed, vacuum suction packaging is carried out. When packaging, attention should be paid to the suction pressure to prevent the product from being squeezed and broken during the suction process. Finally, it is transferred to the warehouse for packaging.

[0045] What is disclosed above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. A person skilled in the art can understand that all or part of the processes of the above embodiments and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for processing an ultra-thin wafer tray, characterized in that: The following steps are involved: S1. Performing double-sided LAP grinding on a wafer tray blank, wherein the wafer tray blank is made of a single crystal silicon material having the same origin as the wafer material; S2, performing outer diameter processing and outer diameter chamfering on the wafer tray blank; S3, turning over and polishing the wafer tray blank, and processing the wafer groove surface and the reserved groove on the wafer tray blank; S4, sandblasting the upper surface of the wafer tray blank; S5, etching the wafer tray blank after sandblasting by using mixed acid; S6. Polishing the wafer groove surface of the etched wafer tray blank using a polishing machine.

2. The method for processing an ultra-thin wafer tray according to claim 1, characterized in that: In step S1, the flat-ground blank is ground using double-sided grinding equipment with 1000-mesh LAP powder.

3. The method for processing an ultra-thin wafer tray according to claim 1, characterized in that: In step S2, the wafer tray blank is subjected to outer diameter processing and outer diameter chamfering by the following steps: S21, bonding on the machine: Bond the wafer tray blank to the quartz plate, place the quartz plate on the machine tool working platform and use a dial indicator to level it, ensuring that the parallelism between the quartz plate surface and the machine tool working table is within 0.05mm; S22, outer diameter chamfering: use a diamond grinding milling tool with a metal base of 30-60mm in diameter, use horizontal arc feed, feed angle of 10-20°, feed arc size of R15-30mm, feed speed of 300-500mm / min, step distance of 0.01-0.02mm, speed of 4500-6500 rpm; after feed is completed, other parameters remain unchanged during chamfering, and feed speed is increased to 1000-1500mm / min; S23, outer diameter processing: When processing the outer diameter after chamfering, other parameters remain unchanged, and the step down distance is increased to 0.03mm-0.06mm.

4. The method for processing an ultra-thin wafer tray according to claim 1, characterized in that: In step S3, when the wafer tray blank is turned over and polished, it is first rough-polished by a 200-300 mesh metal-based diamond tool to a thickness of 0.8-0.9 mm, and then fine-polished by a 450-550 mesh resin-based diamond tool to a thickness of 0.04-0.05 mm, leaving a 0.05 mm margin for subsequent sandblasting and etching.

5. The method for processing an ultra-thin wafer tray according to claim 4, characterized in that: In step S3, the following steps are used to process the wafer groove surface and the reserved groove on the wafer tray blank: a. Rough machining of the wafer groove surface: Use a 100-200 mesh diamond tool with a metal base of less than 30mm in diameter to roughen the wafer groove surface. The tool feed adopts vertical arc feed, the feed angle is 3-5°, the feed speed is 50-100mm / min, and the feed arc is R10-15mm; the tool speed is 6500-7500mm / min, the feed step is 0.01-0.02mm, and the feed speed is 100-300mm / min; b. Processing the reserved groove: Use a 2-4mm metal matrix diamond 250-350 mesh tool to process the reserved groove. The tool feed adopts horizontal arc feed, the feed angle is 10-15°, the feed speed is 50-100mm / min, the feed arc is R2-5mm, the tool speed is 8500-9500mm / min, the feed step is 0.01-0.02mm, and the feed speed is 100-200mm / min; c. Finishing the wafer groove surface: Use a resin-based diamond tool with a mesh size of 1000 or above to finish the wafer groove surface. The tool diameter is 1-2mm smaller than the diameter of the wafer groove surface. The tool feed adopts vertical arc feed, the feed angle is 3-5°, the feed speed is 50-100mm / min, the feed arc is R10-15mm, the tool speed is 6500-7500mm / min, the feed step is 0.005-0.01mm, and the feed speed is 100-200mm / min.

6. The method for processing an ultra-thin wafer tray according to claim 1, characterized in that: In step S4, a sandblasting machine is used to perform rough sandblasting on the wafer tray blank using 150-250 mesh pomegranate sand, and then fine sandblasting on the wafer tray blank using 450-550 mesh pomegranate sand, with a sandblasting amount of 0.03-0.04 mm.

7. The method for processing an ultra-thin wafer tray according to claim 1, characterized in that: In step S5, for a single crystal with a resistance of 0.005-0.02, the mixed acid is composed of HF 49%: HNO3 70%: CH3COOH 99%, with a ratio of 1-2: 8-10: 3-5. The etching time for a single product is 15-20s, the etching temperature is 20°C, and the etching amount of the upper and lower surfaces is 0.01mm per side.

8. The method for processing an ultra-thin wafer tray according to claim 1, characterized in that: In step S5, for single crystals with a resistance of 1-4, the mixed acid is composed of HF 49%: HNO3 70%: CH3COOH 99%, with a ratio of 3-5: 8-10: 3-5. The etching time for a single product is 15-20s, the etching temperature is 20°C, and the etching amount of the upper and lower surfaces is 0.01mm per side.

9. The method for processing an ultra-thin wafer tray according to claim 1, characterized in that: In step S6, the polishing pad of the polishing machine performs X-axis reciprocating movement to polish the wafer groove surface of the wafer tray blank after the etching.

10. The method for processing an ultra-thin wafer tray according to claim 9, characterized in that: In step S6, the silicon wafer is bonded to the wafer tray blank, and the silicon wafer is clamped by negative pressure suction to clamp the wafer tray blank on the polishing machine.

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