Chip manufacturing is hailed as the jewel in the crown of modern industry and is also a key high-end industry that China is currently focusing on conquering. Although the applications of polyurethane are mainly concentrated in industries such as building insulation, furniture and home appliances, automobiles, footwear, and clothing, there is no shortage of the presence of polyurethane materials in chip manufacturing - for example, in CMP polishing pads.
Chemical Mechanical Polishing (CMP) is a popular polishing technique that combines the mechanical grinding and polishing action of abrasive particles with the chemical erosion of polishing slurry. It has evolved from the foundation of chemical polishing and mechanical polishing, while overcoming their respective shortcomings. CMP equipment consists of three main modules: polishing, cleaning, and transportation. During the operation, the polishing head presses the wafer surface to be polished against a rough polishing pad. Through the coupling of chemical erosion from the polishing slurry, friction from abrasive particles and the polishing pad, global planarization is achieved.
The seven major steps in front-end wafer fabrication are diffusion, lithography, etching, ion implantation, film growth, CMP, and metallization. As a necessary process in wafer fabrication, CMP is crucial for the production of high-precision and high-performance wafers. The integrated circuit (IC) industry chain can be divided into four major areas: silicon wafer manufacturing, IC design, IC manufacturing, and IC packaging & testing. Except for the field of IC design, CMP is used in the other three areas.
Wafer manufacturers typically must improve the polishing processes to meet the requirements for wafer flatness, and the greatest advantage of CMP polishing is its ability to achieve nanometer-level global planarization of the processed surface, meeting the requirements for ultra-precision and non-damaging surface processing of integrated circuits with feature sizes below 0.35μm. CMP is a critical process in achieving wafer surface planarization in the integrated circuit (chip) manufacturing process and is an important step in promoting process technology upgrades in IC manufacturing.
The equipment and consumables used in CMP include: polishing machines, polishing slurries, polishing pads, post-CMP cleaning equipment, polishing endpoint detection and process control equipment, waste treatment and monitoring equipment, etc. Polishing machines, polishing slurries, and polishing pads are the three key elements of CMP, and their performance and mutual compatibility determine the level of surface flatness achievable by CMP. The two most important materials for polishing are the polishing slurry and the polishing pad.
CMP polishing pads require excellent corrosion resistance, hydrophilicity, and mechanical properties. The most common material used is rigid, porous polyurethane foam with narrow, high aspect ratio groove patterns. Polyurethane exhibits high elasticity and abrasion resistance, allowing it to maintain relatively stable performance under continuous abrasion. During the polishing process, the micro-pores on the surface of the rigid foam polyurethane polishing pad (mechanical and porous water absorption properties) can soften and roughen the pad surface, as well as retain abrasive particles within the polishing slurry.
These micro-pores can also serve the purpose of collecting removed materials, transporting polishing slurry, and ensuring chemical erosion, which helps improve polishing uniformity and efficiency.
The global polishing pad market is concentrated, with Dow Chemical alone accounting for over 70% of the market share. In the past, China imported almost all CMP polishing pads for polishing processes. In recent years, with the acceleration of chip localization, many related companies have shown great interest in the field of CMP polishing pads. For example, Wanhua Chemical plans to build a CMP Pad facility with an annual capacity of 600,000 pieces. In the future, China’s localization degree of CMP polishing pads, a high-end application of polyurethane, will continue to grow.
