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CN-120382425-B - Hard and brittle semiconductor substrate double-sided thinning process based on ultrafast laser

CN120382425BCN 120382425 BCN120382425 BCN 120382425BCN-120382425-B

Abstract

The invention discloses a hard and brittle semiconductor substrate double-sided thinning process based on ultrafast laser. The process comprises the steps of firstly carrying out activation treatment on the two sides of a wafer through ion implantation or chemical solution at high temperature to soften surface materials so as to reduce processing difficulty, then fixing the wafer in a laser modification chamber, synchronously updating the solution in the chamber and removing laser byproducts through dynamic circulating corrosive liquid, then synchronously scanning the upper surface and the lower surface of the wafer by utilizing two beams of ultrafast lasers respectively, adopting a nonlinear path to realize double-sided efficient thinning in the first stage, switching to a linear parallel path in the second stage, adjusting the direction of the wafer, completing morphology regulation of a microstructure and double-sided precise finishing, and finally removing allowance through double-sided Chemical Mechanical Polishing (CMP) to obtain target thinning amount and an atomic level flat surface. The process has the advantages of high efficiency, low damage and high precision through double-sided cooperative processing and dynamic corrosive liquid control, and is suitable for large-scale thinning manufacture of hard and brittle semiconductor materials such as silicon carbide, gallium nitride and the like.

Inventors

  • GUAN YINGCHUN
  • MA YI

Assignees

  • 北京航空航天大学

Dates

Publication Date
20260512
Application Date
20250423

Claims (6)

  1. 1. The double-sided thinning process of the hard and brittle semiconductor substrate based on the ultrafast laser is characterized by comprising the following steps of: (1) Carrying out double-sided activation treatment on the hard and brittle semiconductor cutting sheet, and softening a double-sided surface layer material by ion implantation technology or chemical solution soaking under the high temperature condition, wherein the high temperature range is 50-100 ℃, the ion implantation activation treatment adopts argon-oxygen mixed gas plasma with the volume ratio of 3:1, the implantation energy is 20-200 keV, the treatment time is 5-20 min, and the chemical activation adopts hydrofluoric acid and hydrogen peroxide mixed solution with the volume ratio of 1:4-1:8, and the soaking time is 5-10 min; (2) The activated wafer is fixed in a positioning device of a laser modification chamber, a liquid feeding device and a suction filtration device are arranged in the chamber, etching liquid is dynamically and circularly updated to maintain concentration stability, and the etching liquid is mixed solution of hydrofluoric acid, nitric acid, sulfuric acid and deionized water, wherein the volume ratio of the hydrofluoric acid, the nitric acid, the sulfuric acid and the deionized water is 15-20 vol%, 30-40 vol%, 0-10 vol% and 30-55 vol% respectively; (3) The method comprises the steps of starting ultra-fast laser 1 and ultra-fast laser 2 to synchronously scan the upper surface and the lower surface of a wafer respectively, performing first-stage thinning, namely scanning the upper surface by the ultra-fast laser 1 through a nonlinear path, synchronously scanning the lower surface by the ultra-fast laser 2 through the nonlinear path until the depth of double-sided thinning reaches 40+/-0.5 mu m, performing second-stage thinning, namely adjusting the energy density of laser, rotating the wafer by 90 degrees through a positioning device, and switching the ultra-fast laser 1 and the ultra-fast laser 2 into linear parallel path scanning until the depth of double-sided thinning reaches 4+/-0.5 mu m; (4) And (3) carrying out double-sided Chemical Mechanical Polishing (CMP) on the thinned wafer to finally realize the atomic-level flat surface with the total thinning amount of 100+/-0.5 mu m and the surface roughness Ra <1 nm.
  2. 2. The process of claim 1 wherein in step (1) the hard and brittle semiconductor wafer is one of single crystal silicon carbide, single crystal gallium nitride or single crystal diamond.
  3. 3. The process of claim 1, wherein the positioning device in the step (2) comprises a vacuum adsorption fixture, the positioning accuracy is +/-0.1 mm, the rotation angle error is less than or equal to 0.5 degrees, the flow rate of the liquid conveying device is 50-200 mL/min, and the negative pressure of the suction filtration device is maintained at 0.1-0.5 MPa.
  4. 4. The process of claim 1, wherein in the first stage scanning of step (3), the nonlinear scanning path is one or a combination of spiral progressive path or staggered grid type path, the laser pulse width is 100 fs-50 ps, the wavelength is 343-1064 nm, the energy density is 3-15J/cm 2, and the scanning speed is 50-1000 mm/s.
  5. 5. The process according to claim 1, wherein in the second stage scanning in the step (3), the scanning distance of the linear parallel path is 20-90% of the diameter of the light spot, the laser energy density is adjusted to 1-3J/cm 2, and the scanning speed is 500-1000 mm/s.
  6. 6. The process according to claim 1, wherein the CMP in the step (4) is performed using an alkaline polishing liquid having a pH of 10 to 12, a double-sided polishing pressure of 400 to 500 g cm-2, and a polishing temperature of 20 to 25 ℃.

Description

Hard and brittle semiconductor substrate double-sided thinning process based on ultrafast laser Technical Field The invention belongs to the technical field of laser-assisted processing, and particularly relates to a hard and brittle semiconductor substrate double-sided thinning process based on ultrafast laser. Background With the continuous development of miniaturization and high integration of semiconductor devices, wafer thinning technology has become a key element for advanced packaging and device manufacturing. For hard and brittle semiconductor materials such as silicon carbide (SiC), gallium nitride (GaN) and the like, a cutting piece formed by cutting an ingot has subsurface defects, the thickness is difficult to meet the requirements of subsequent processes such as photoetching and the like, and the cutting piece needs to be thinned by a thinning process by 50-100 mu m. However, the traditional thinning technology faces significant challenges in processing such high-hardness materials, namely mechanical grinding can realize rapid thinning, severe friction between a grinding wheel and a sharp corner region is easy to cause subsurface damage and microcracks, and grinding wheel loss is serious, while single-sided laser thinning technology can reduce the introduction of damage, but has low processing efficiency, deposition byproducts generated by laser action are difficult to remove in real time, and subsequent laser processing is easy to interfere, so that the process stability is reduced. In the prior art, single-sided laser thinning is required to rely on multi-pass cleaning and parameter adjustment to maintain processing precision, the overall efficiency is limited, and the two sides of a wafer cannot be processed synchronously, so that uneven stress distribution and warping risks are caused. In addition, the surface residues (such as amorphous layer) after laser processing need to be removed by an additional chemical etching or polishing step, further increasing the process complexity and cost. Aiming at the problems, the invention provides a hard and brittle semiconductor substrate double-sided thinning process based on ultrafast laser, which realizes the aims of high-efficiency and low-damage thinning through the collaborative design of double-sided synchronous scanning, dynamic corrosive liquid circulation and staged path optimization. The process comprises the steps of softening the surface layer of a wafer through ion implantation or chemical activation, reducing the energy requirement of subsequent laser processing, then synchronously implementing nonlinear path rough processing and linear path finishing on the double sides by using ultra-fast laser, removing laser byproducts in real time by combining with a dynamically updated corrosive liquid, avoiding surface pollution, and finally realizing an atomic-level flat surface through double-side Chemical Mechanical Polishing (CMP). Compared with the traditional process, the method can effectively improve the thinning efficiency and provide a reliable solution for high-precision manufacturing of the hard and brittle semiconductor material. Disclosure of Invention Object of the invention Aiming at the defects of the prior art, the invention aims to provide a hard and brittle semiconductor substrate double-sided thinning process based on ultrafast laser, which aims to improve the efficiency and quality in the wafer thinning process. (II) technical scheme The invention is realized by the following technical scheme. (1) Double-sided activation treatment is carried out on the hard and brittle semiconductor cutting sheet, and under the high-temperature condition, the double-sided surface layer material is softened by the ion implantation technology or the chemical solution soaking; (2) The activated wafer is fixed in a positioning device of a laser modification chamber, a liquid feeding device and a suction filtration device are arranged in the chamber, and etching liquid is updated through dynamic circulation to maintain concentration stability; (3) The method comprises the steps of starting ultra-fast laser 1 and ultra-fast laser 2 to synchronously scan the upper surface and the lower surface of a wafer respectively, performing first-stage thinning, namely scanning the upper surface by the ultra-fast laser 1 through a nonlinear path, synchronously scanning the lower surface by the ultra-fast laser 2 through the nonlinear path until the depth of double-sided thinning reaches 40+/-0.5 mu m, performing second-stage thinning, namely adjusting the energy density of laser, rotating the wafer by 90 degrees through a positioning device, and switching the ultra-fast laser 1 and the ultra-fast laser 2 into linear parallel path scanning until the depth of double-sided thinning reaches 4+/-0.5 mu m; (4) And (3) carrying out double-sided Chemical Mechanical Polishing (CMP) on the thinned wafer to finally realize the atomic-level flat surface with the total thin