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CN-121989121-A - Metal composite sheet, preparation method thereof and grinding wheel for thinning wafer

CN121989121ACN 121989121 ACN121989121 ACN 121989121ACN-121989121-A

Abstract

The invention provides a metal composite sheet, a preparation method thereof and a grinding wheel for thinning a wafer. The metal composite sheet is formed by alternately laminating a first metal material layer and a second metal material layer, the total number of layers of the first metal material layer and the second metal material layer is odd, the adjacent first metal material layer and the adjacent second metal material layer are connected in a metallurgical bonding mode, the top surface and the bottom surface which are oppositely arranged in the metal composite sheet are used as the top surface and the bottom surface of a grinding wheel matrix, the first metal material layer is made of an alloy material or a metal material with CTE not exceeding 10 ppm/DEG C and heat conduction coefficient not lower than 130W/m.K, and the second metal material layer is made of an iron-nickel base alloy material with CTE not exceeding 6.0 ppm/DEG C. The wafer thinning equipment can improve the thermal expansion matching property of the grinding wheel matrix and the silicon wafer and the structural stability of the thinned TSV in the wafer thinning process, and realize high precision and low damage of 3D IC thinning.

Inventors

  • ZHANG LIFEI
  • LU XINCHUN
  • ZHAO YING
  • ZHAO DEWEN

Assignees

  • 清华大学

Dates

Publication Date
20260508
Application Date
20251028

Claims (15)

  1. 1. A metal composite sheet for manufacturing a grinding wheel for thinning a wafer is characterized in that, The metal composite sheet is formed by alternately laminating a first metal material layer and a second metal material layer, wherein the sum of the layers of the first metal material layer and the second metal material layer is odd, the adjacent first metal material layer and the second metal material layer are connected in a metallurgical bonding mode, the first metal material layer is made of an alloy material or a metal material with the coefficient of thermal expansion CTE not exceeding 10 ppm/DEG C and the coefficient of thermal conductivity not lower than 130W/m.K, and the second metal material layer is made of an iron-nickel base alloy material with the coefficient of thermal expansion CTE not exceeding 6.0 ppm/DEG C; and taking the top and bottom surfaces, which are oppositely arranged in the metal composite sheet and parallel to the first metal material layer, as the top and bottom surfaces of the grinding wheel matrix.
  2. 2. The metal composite sheet according to claim 1, wherein, The first metal material layer is made of a Cu-W alloy material, a Mo-Cu alloy material or a molybdenum metal simple substance material; The second metal material layer is made of Invar Alloy material, kovar Alloy material or Alloy 42 Alloy material.
  3. 3. The metal composite sheet according to claim 2, wherein the first metal material layer is a Cu-W alloy material and the second metal material layer is an Invar alloy material: Based on 100% of the total mass of the Cu-W alloy, the Cu-W alloy contains 20% -15% of Cu and 80% -85% of W by mass and/or, The thickness ratio of the first metal material layer to the second metal material layer is (1-2): 1.
  4. 4. The metal composite sheet according to claim 1, wherein the thickness of the second metal material layer is 0.1-0.5 mm, the thickness of the first metal material layer is 0.1-0.5 mm, and/or, The sum of the layers of the first metal material layer and the second metal material layer is more than or equal to 5 and less than 10.
  5. 5. The metal composite sheet according to claim 1, wherein the metal composite sheet comprises a first small layer, a second small layer, and an nth small layer in this order from bottom to top, the ith small layer and the (n+1) th small layer being symmetrical with respect to the (n+1) th/2 nd small layer, wherein i is a natural number not less than 1 and not more than N.
  6. 6. The metal composite sheet according to claim 1, wherein the interlayer bonding strength of the adjacent first metal material layer and second metal material layer is not less than 200 Mpa, and/or, Adjacent first and second metal material layers are connected by forming a composite interface layer between the first and second metal material layers.
  7. 7. The metal composite sheet according to claim 1, wherein the first metal material layer is made of a Cu-W alloy material and the second metal material layer is made of an Invar alloy material, and wherein adjacent first metal material layers and second metal material layers are connected by forming a Cu3W2 and gamma-FeNi composite interface layer between the first metal material layer and the second metal material layers.
  8. 8. The metal composite sheet of claim 7, wherein the Cu3W2 and gamma-FeNi composite interface layer comprises, in order, a Cu3W2 and Cu solid solution mixed layer, a gamma-FeNi and Cu3W2 mixed layer, and a gamma-FeNi and FeNi3 mixed layer, wherein the Cu3W2 and Cu solid solution mixed layer is immediately adjacent to the first metal material layer, and the gamma-FeNi and FeNi3 mixed layer is immediately adjacent to the second metal material layer.
  9. 9. The metal composite sheet according to claim 8, wherein the thickness of the Cu3W2 and Cu solid solution mixed layer is 1 to 3 μm, the thickness of the γ -FeNi and Cu3W2 mixed layer is 1 to 1.5 μm, and the thickness of the γ -FeNi and FeNi3 mixed layer is 1 to 2 μm.
  10. 10. The method of producing a metal composite sheet according to any one of claims 1 to 9, comprising the steps of: 1) Acquiring a first metal material layer and a second metal material layer; 2) Alternately stacking the first metal material layers and the second metal material layers; 3) And carrying out diffusion welding treatment on the alternately stacked first metal material layers and second metal material layers to obtain the metal composite sheet.
  11. 11. The method for producing a metal composite sheet according to claim 10, wherein, The diffusion welding of the alternately stacked first and second metal material layers includes: The metallurgical bonding step is that the first metal material layers and the second metal material layers which are alternately stacked are subjected to heat preservation and pressure maintaining treatment in a vacuum environment, so that interface atoms between layers are diffused to form metallurgical bonding; And a cooling treatment step, namely cooling the product obtained in the metallurgical bonding step to obtain the metal composite sheet.
  12. 12. The method for producing a metal composite sheet according to claim 11, wherein, The first metal material layer is made of Cu-W alloy material, and when the second metal material layer is made of Invar alloy material, heat and pressure preservation treatment is carried out at 900-950 ℃ and under 30-50 MPa axial pressure.
  13. 13. The method for producing a metal composite sheet according to claim 11, wherein, And carrying out surface polishing treatment before alternately stacking the first metal material layers and the second metal material layers, so that the surface roughness of the first metal material layers and the second metal material layers is less than or equal to 0.8 mu m.
  14. 14. The method of producing a metal composite sheet according to claim 11, further comprising the steps of: 4) And 3) performing end face fine grinding on the metal composite sheet obtained after the diffusion welding treatment in the step 3) until the absolute value of the thickness tolerance is not more than 0.005 mm and the flatness is less than or equal to 3 mu m.
  15. 15. Grinding wheel for thinning wafers, characterized by comprising a grinding wheel base body composed of the metal composite sheet according to any one of claims 1 to 9 or a grinding wheel base body composed of the metal composite sheet prepared by the preparation method according to any one of claims 10 to 14.

Description

Metal composite sheet, preparation method thereof and grinding wheel for thinning wafer The application is a divisional application of an application patent application with the application number 202511550953X, which is filed on the day of 2025, 10 and 28. Technical Field The invention belongs to the technical field of wafer grinding, and particularly relates to a metal composite sheet, a preparation method and a grinding wheel for wafer thinning. Background Three-dimensional integrated circuits (3D ICs) are an important technological path for the semiconductor industry to continue moore's law, improving chip performance and integration. The core idea is to stack a plurality of chips or functional layers in a vertical direction, and realize interlayer electrical connection Through-Silicon Via (TSV) and other interconnection technologies, so as to realize higher functional density in a limited space. Wafer thinning is a critical support process in 3D IC fabrication, the main purpose of which is to thin the wafer from the original thickness to an ultra-thin state suitable for vertical integration. Ultra-thin wafers are the physical basis for achieving 3D stacking and are critical to optimizing electrical performance and thermal management. As the number of stacked layers of 3D ICs increases, the demand for thickness reduction of individual wafers is becoming increasingly stringent. Meanwhile, 3D IC technology places extremely high demands on the surface quality of thinned wafers, including excellent total thickness bias (Total Thickness Variation, TTV) and extremely low surface roughness (Roughness Average, ra), to ensure accuracy, uniformity and stability of subsequent bonding processes. To achieve the above-mentioned thinning objective, the wafer thinning apparatus generally processes an ultrathin wafer by using a physical grinding action of a grinding wheel. The equipment has to precisely design and control the grinding structure and the grinding process, and can meet the processing requirements (such as thickness is less than or equal to 10 mu m, TTV is less than or equal to 1.5 mu m and Ra is less than or equal to 5 nm) of ultrathin wafers, and simultaneously, the manufacturing cost and the production efficiency are both considered. The thermal expansion Coefficient (CTE) mismatch of the grinding wheel matrix and the silicon wafer causes non-uniform thermal deformation of the wafer in a temperature change range (20-200 ℃) in the grinding process, wherein the thermal deformation of the end face generates periodic jump on a macroscopic scale, the thickness of the wafer is reduced unevenly and the edge stress is concentrated, further the risk of alignment deviation and the probability of cracking in the subsequent stacking bonding process are increased, the high-frequency vibration in the grinding process is induced by the thermal deformation on a microscopic scale, the local grinding force is suddenly increased, the interface separation (pull-out) of a copper column and the silicon matrix in a Through Silicon Via (TSV) is caused, and subsurface cracks with the damaged layer depth of about 2 mu m are generated in the silicon matrix. Meanwhile, in the thinning process of the 3D IC stacked wafer, a copper interconnection layer (the hardness approximately equal to 2.5 GPa) in a Through Silicon Via (TSV) of a chip and a silicon substrate (the hardness approximately equal to 12 GPa) have obvious hardness mismatch, and when dissimilar materials are alternately ground, grinding wheel abrasive particles bear severe stress fluctuation, so that grinding precision is reduced and surface quality is deteriorated. In short, in the semiconductor wafer thinning process, how to realize high precision and low damage of 3D IC thinning has been an industrial problem. At present, some new technologies are developed in the industry in order to realize high-precision and low-damage 3D IC thinning. For example, CN104114666a discloses an abrasive article and method of forming the same, focusing on developing a bonded abrasive article with a low delta CTE, reducing the risk of fracture due to thermal stress by controlling the CTE difference between the bond material and the abrasive particles, as well as the high porosity design. Developing a combination of a vitrified inorganic binder and diamond abrasive particles, and controlling delta CTE (the CTE difference between the binder and the abrasive particles) to be less than or equal to 5.5 ppm/DEGC, and the porosity to be more than or equal to 50%. Is suitable for grinding semiconductor wafers, and the thermal deformation rate is reduced by 40%. As another example, CN102470505A discloses an abrasive tool and method of manufacture having a flat and consistent planar topography for conditioning a CMP pad. The CTE mismatch problem is controlled by using a low CTE substrate in a CMP conditioner with a metal bond to join the abrasive particles. The method comprises the steps of adopting