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CN-121156853-B - Processing method for thinning silicon carbide wafer by using laser modification and silicon carbide wafer thinning sheet

CN121156853BCN 121156853 BCN121156853 BCN 121156853BCN-121156853-B

Abstract

The invention provides a processing method for thinning a silicon carbide wafer by using laser modification and a silicon carbide wafer thinning sheet, and relates to the technical field of crystal laser processing. The method comprises the steps of S1, carrying out first laser scanning on the whole surface of a silicon carbide wafer to be thinned, forming a modified layer in the silicon carbide wafer, S2, carrying out second laser scanning on the circumferential edge part of the surface to be thinned after the first laser scanning, enabling the modified layer formed on the circumferential edge part to extend towards the surface to be thinned, S3, separating and grinding the silicon carbide wafer subjected to the second laser scanning in sequence, and obtaining a silicon carbide wafer thinned sheet, wherein the thickness of the modified layer after the second laser scanning is larger than that of the modified layer after the first laser scanning. By means of twice laser scanning, the modification method is optimized, the separation difficulty and the warping problem after the wafer is thinned can be greatly reduced, and abrasion of the grinding wheel and the cracking risk of the wafer are reduced.

Inventors

  • SUI XIAOMING
  • ZONG YANMIN
  • MA LIXING
  • LIU SHUO

Assignees

  • 上海天岳半导体材料有限公司

Dates

Publication Date
20260512
Application Date
20250829

Claims (9)

  1. 1. A method of processing a thinned silicon carbide wafer using laser modification, the method comprising the steps of: s1, carrying out first laser scanning on the whole surface of a silicon carbide wafer to be thinned, and forming a modified layer inside the silicon carbide wafer; s2, carrying out second laser scanning on the circumferential edge part of the surface to be thinned after the first laser scanning, so that the modified layer formed on the circumferential edge part extends towards the surface to be thinned; s3, separating and grinding wheel thinning the silicon carbide wafer scanned by the second laser in sequence to obtain a silicon carbide wafer thinned sheet; Wherein, the thickness of the modified layer after the second laser scanning is larger than that after the first laser scanning; The thickness of the modified layer of the second laser scanning is 3-7 μm higher than that of the modified layer of the first laser scanning.
  2. 2. The method of claim 1, wherein the modified layer thickness of the second laser scan is increased by 3-5 μm from the modified layer thickness of the first laser scan.
  3. 3. The process of claim 1 wherein the inner diameter of the peripheral edge portion is 0.6-0.8 times the entire radius of the silicon carbide wafer centered at the center of the wafer.
  4. 4. The process of claim 1, wherein the laser modified reduced thickness is >80 μm.
  5. 5. The method of claim 1, wherein the first laser scan and the second laser scan each employ a picosecond laser device, and further wherein the laser has a wavelength of 532-1064nm and a pulse width of 45-500ps.
  6. 6. The method of claim 1, wherein the first laser scan and the second laser scan each have a laser power of 2-22W and a scan rate of 300-800mm/s.
  7. 7. The method of claim 1, wherein the scan paths of the first and second laser scans are laterally shifted along the <11-20> crystal plane at intervals to form a plurality of single scan paths, and the interval between adjacent single scan paths is 120-350um.
  8. 8. The method of claim 5, wherein step S3 further comprises the steps of: S31, firstly, pasting a film on a surface to be thinned of the silicon carbide wafer scanned by the laser for the second time, fixing the surface to be thinned on a pasting ring, absorbing the surface to be thinned on the pasting ring by adopting a ring-mounted absorption clamp, and separating the silicon carbide wafer along the modified layer by applying a tensile force to obtain a silicon carbide sub-wafer; and S32, grinding wheel thinning is carried out on the separation surface of the silicon carbide sub-wafer, so that the silicon carbide wafer thinned sheet is obtained.
  9. 9. The method according to claim 8, wherein the ring-shaped suction jig comprises suction nozzles and connecting rods which are annularly distributed at certain intervals, wherein openings at the upper ends of the suction nozzles are connected with the vacuum generator, one ends of the connecting rods are connected with the suction nozzles, and the other ends of the connecting rods are connected with the pressure sensor.

Description

Processing method for thinning silicon carbide wafer by using laser modification and silicon carbide wafer thinning sheet Technical Field The invention relates to the technical field of crystal laser processing, in particular to a processing method for thinning a silicon carbide wafer by using laser modification and a silicon carbide wafer thinning sheet. Background Silicon carbide (SiC) is a semiconductor material with excellent properties and is widely used in the field of high power, high frequency and high temperature electronics. Along with the development of the SiC technology, the application of the SiC is continuously expanded in aspects of power electronics, photoelectric devices, high-temperature devices and the like, and particularly the application prospect of MOSFET devices in the aspect of power management application is wide. The MOSFET is a vertical device, the thinner the total thickness of the device, the lower the on-resistance, and the lower the power consumption, and the drain of the device is generally on the back of the wafer, so after the front-side process of the wafer is completed, the thickness of the SiC wafer needs to be thinned to reduce the on-resistance of the device. The existing SiC wafer thinning method has a plurality of defects, and the low production efficiency and the high production cost restrict the application and popularization of the process. The existing SiC wafer thinning processing method is mainly based on the grinding wheel thinning process of the IN-Feed principle. The wafer is adsorbed on the vacuum carrier, and the thinning treatment of the wafer is realized through the rotation of the carrier and the longitudinal feeding movement of the grinding wheel. On one hand, the process has high consumption rate and low efficiency because of high silicon carbide hardness. In the thinning process, due to the adoption of a hard-touch hard grinding mode, mechanical stress can be introduced at a contact point due to the direct contact of grinding wheel abrasive particles and a wafer, so that defects such as cracks and broken edges are easily caused, and the wafer yield is affected. On the other hand, the thinner the wafer thickness is, the larger the warpage is, the larger the TTV of the thinned substrate is, the more difficult the process is to accurately control the thickness, and the processing difficulty is improved. In order to solve the above problems, on the basis of the conventional grinding wheel thinning, a "Taiko process" method has been proposed, that is, when the back of the wafer is thinned, the peripheral edge portion (about 3 mm) of the wafer is remained, and only the inside of the wafer is thinned and removed. By introducing the technology, the problems of reducing the carrying risk of the thin wafer and reducing the warpage can be realized, meanwhile, on the basis, a thinning processing method aiming at the inner area of the wafer is developed, after the inner area of the wafer is separated by adopting laser, the annular cutting process treatment is carried out on the edge of the wafer, and the processing cost can be further reduced on the basis of ensuring the warpage of the wafer. The existing silicon carbide wafer thinning method is mainly carried out in a grinding wheel thinning mode. And mechanical friction is formed between diamond particles bonded on the grinding wheel and silicon carbide in the process of mutual movement between the grinding wheel and the wafer, and the silicon carbide wafer is removed through the hardness difference of the diamond and the silicon carbide. Although diamond is the material with the largest hardness in nature, because the Mohs hardness of the silicon carbide material reaches 9.2-9.5, the silicon carbide material is the material with the high hardness which is inferior to that of diamond (10) in nature, and the process mode of thinning the grinding wheel is determined to be realized by grinding of hard collision. The process is very low in efficiency, high consumption of the diamond grinding wheel is formed, and mechanical stress is easily introduced in the process, so that the wafer yield is affected. In summary, the process has the defects of low processing efficiency, high processing cost, easiness in introducing mechanical stress damage and the like, and the other scheme adopts a circular cutting process scheme that laser or a grinding wheel is firstly used for processing the inside of a wafer and then cutting the outer edge is performed, so that the technical complexity is high, meanwhile, the risk of cutting splinters exists due to the circular cutting steps which are introduced, the wafer yield is reduced, and the production cost is increased. Disclosure of Invention In order to solve the above problems, a first aspect of the present invention provides a processing method for thinning a silicon carbide wafer using laser modification, the processing method comprising the steps of: s1, carrying out first las