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CN-117381549-B - Method for grinding wafer and polished wafer

CN117381549BCN 117381549 BCN117381549 BCN 117381549BCN-117381549-B

Abstract

The invention discloses a grinding method of a wafer and the ground wafer, wherein the grinding method sequentially comprises a first grinding, a second grinding, a third grinding, a fourth grinding and a fifth grinding, wherein the first grinding, the second grinding, the third grinding and the fourth grinding are used for grinding metal films on the surface of the wafer, the metal films on the surface of the wafer are all ground after the fourth grinding is finished, the grinding thickness is T 0 ＝2×T 1 -T 2 -0.2;T 1 ＝0.7×T 0 -0.2;T 2 ＝4×T 3 -0.4, wherein T 0 is the initial thickness of the metal films on the surface of the wafer, T 1 is the thickness of the metal films remained after the first grinding, T 2 is the thickness of the metal films remained after the second grinding, and T 3 is the thickness of the metal films remained after the third grinding. The invention adopts five steps of grinding, wherein the first four steps of grinding grind the metal film with specific thickness on the surface of the wafer, finally improve the grinding efficiency and improve the surface defect of the wafer.

Inventors

  • LI XUNXUN
  • SHAO HUI
  • NIU XIAOHAO

Assignees

  • 北京晶亦精微科技股份有限公司

Dates

Publication Date
20260505
Application Date
20231127

Claims (5)

  1. 1. The polishing method of the wafer is characterized by sequentially comprising a first polishing, a second polishing, a third polishing, a fourth polishing and a fifth polishing, wherein the first polishing, the second polishing, the third polishing and the fourth polishing are used for polishing a metal film on the surface of the wafer, and the metal film on the surface of the wafer is completely polished after the fourth polishing is finished; the thickness of the grinding is as follows: T 0 =2×T 1 -T 2 -0.2; T 1 =0.7×T 0 -0.2; T 2 =4×T 3 -0.4; Wherein, T 0 is the initial thickness of the metal film on the surface of the wafer, T 1 is the thickness of the metal film left after the first grinding, T 2 is the thickness of the metal film left after the second grinding, and T 3 is the thickness of the metal film left after the third grinding; the initial thickness of the metal film on the surface of the wafer is 3.5-5 mu m; During the first grinding, the grinding disc applies pressure to the surface of the wafer to be 2.2-2.6 psi, and the metal polishing solution with the flow rate of 250-350 mL/min is injected; during the second grinding, the grinding disc applies pressure to the surface of the wafer to be 2.2-2.5 psi, and the metal polishing solution with the flow rate of 250-350 mL/min is injected; during the third grinding, the grinding disc applies pressure to the surface of the wafer to be 2.2-2.5 psi, and the metal polishing solution with the flow rate of 250-350 mL/min is injected; during the fourth grinding, the grinding disc applies pressure to the surface of the wafer to be 1.4psi-1.8psi, and the metal polishing solution with the flow rate of 250mL/min-350mL/min is injected; In the fifth polishing, the blocking layer on the surface of the wafer is removed and the dielectric is polished, wherein the polishing thickness of the dielectric is 1-1.5 mu m; after finishing the fifth grinding, cleaning the wafer to realize the wafer dry in and dry out; The third grinding and the fourth grinding are performed in the same grinding disc, and the first grinding, the second grinding and the fifth grinding are performed in different grinding discs independently.
  2. 2. The method according to claim 1, wherein the fifth polishing is performed by applying a pressure of 1.2-1.8 psi to the wafer surface by the polishing platen, and injecting a barrier polishing liquid at a flow rate of 250-350 mL/min.
  3. 3. The method of polishing a wafer according to claim 1, wherein the metal film is copper.
  4. 4. The method according to claim 1 or 2, wherein the rotation speed of the polishing disk is 83rpm to 103rpm and the rotation speed of the polishing head is in the range of 77rpm to 97rpm during polishing.
  5. 5. A wafer polished by the polishing method according to any one of claims 1 to 4.

Description

Method for grinding wafer and polished wafer Technical Field The invention relates to the field of wafer manufacturing, in particular to a wafer grinding method and a ground wafer. Background In integrated circuit fabrication, deposition of Ultra-thick metal (Ultra THICK METAL, UTM) is often encountered, depending on device design requirements. In general, when forming copper interconnection, metal copper needs to be deposited in the trench, and after the deposition is completed, the thickness of the metal copper layer outside the trench and on the dielectric layer reaches 4 micrometers or more, and the metal copper needs to be removed by chemical mechanical polishing. For the chemical mechanical polishing of super-thick metal, the metal removal amount is large, the polishing time is long, the temperature rise in the polishing process is fast, byproducts in the polishing process are not easy to clean up, the polishing rate is reduced, the uniformity of the wafer surface morphology is changed, scratch defects are easily caused, and finally the yield and the reliability of products are reduced. In the prior art, a two-step polishing method is often employed. Taking the removal of the metal copper layer and the diffusion barrier layer outside the trench as an example, firstly, removing part of the metal copper layer by a first step of grinding, and then removing the rest of the metal copper layer, the diffusion barrier layer and part of the interlayer dielectric layer by a second step of grinding. The first polishing step is sequentially performed with high-pressure polishing of the first polishing disc P1, high-pressure polishing of the second polishing disc P2 and cleaning in the cleaning tank, and the second polishing step is sequentially performed with high-pressure polishing of the first polishing disc P1, low-pressure polishing of the second polishing disc P2, and cleaning in the cleaning tank, wherein the third polishing disc P3 is sequentially performed with high-pressure polishing of the first polishing disc P1. Because the wafer needs to be placed into the first grinding disc, the second grinding disc and the cleaning tank for cleaning, the circulation time of the wafer between each grinding disc and the cleaning tank is increased, thereby reducing the productivity and improving the cost. Later, the technology is improved, the first step of integration is completed on the first grinding disc, after the grinding pad is washed by high-pressure water, the second step of operation is continuously performed on the first grinding disc, so that the processing time is shortened although secondary washing is avoided, the processing time of wafers on the first grinding disc is too long, the productivity is also influenced, and the difference between the first actual use time and the second actual use time of the grinding disc is larger and larger along with the increase of the number of wafers, the consumable waste is caused, and the cost is also higher. The existing ultra-thick metal chemical mechanical polishing process flow has the defects of low machine yield, poor uniformity in a wafer, high cost and the like. Disclosure of Invention Therefore, the invention aims to solve the technical problems of low productivity, poor uniformity in a wafer and high cost of the conventional grinding method, thereby providing a grinding method of a wafer and the ground wafer. Therefore, the invention adopts the following technical scheme: The invention provides a polishing method of a wafer, which is characterized by sequentially comprising a first polishing, a second polishing, a third polishing, a fourth polishing and a fifth polishing, wherein the first polishing, the second polishing, the third polishing and the fourth polishing are used for polishing a metal film on the surface of the wafer, and the metal film on the surface of the wafer is completely polished after the fourth polishing is finished; the thickness of the grinding is as follows: T0＝2×T1-T2-0.2; T1＝0.7×T0-0.2; T2＝4×T3-0.4 Wherein T 0 is the initial thickness of the metal film on the wafer surface, T 1 is the thickness of the metal film left after the first grinding, T 2 is the thickness of the metal film left after the second grinding, and T 3 is the thickness of the metal film left after the third grinding, which is generally 0.2-0.5 μm. The initial thickness of the metal film on the surface of the wafer is 3.5-5 mu m. During the first grinding, the grinding disc applies pressure to the surface of the wafer to be 2.2-2.6psi, and the metal polishing solution with the flow rate of 250-350ml/min is injected; during the second grinding, the grinding disc applies pressure to the surface of the wafer to be 2.2-2.5psi, and the metal polishing solution with the flow rate of 250-350ml/min is injected; During the third grinding, the grinding disc applies pressure to the surface of the wafer to be 2.2-2.5psi, and the metal polishing solution with the flow rate of