Development of slurry-less electrochemical mechanical polishing machine for wide-gap semiconductor substrates applying ultrasonic vibration

2022 Fiscal Year Final Research Report

• Project/Area Number: 21K18677
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 18:Mechanics of materials, production engineering, design engineering, and related fields
• Research Institution: Osaka University
• Principal Investigator: Yamamura Kazuya 大阪大学, 大学院工学研究科, 教授 (60240074)
• Project Period (FY): 2021-07-09 – 2023-03-31
• Keywords: ワイドギャップ半導体 / 電気化学機械研磨 / 陽極酸化 / SiC / 超音波振動 / スラリーレス

Outline of Final Research Achievements

Chemical mechanical polishing is currently the mainstream method for polishing wide-gap semiconductor substrates, but it has many problems such as low processing efficiency, high cost of the slurry to be used, and high environmental load. In order to solve these problems, we developed a new slurry-less ultrasonic/anodization-assisted electrochemical mechanical polishing process that softens the surface by anodization and removes the modified layer using fixed abrasive grains with lower hardness than the base material. As a result, in the polishing of 4H-SiC (0001) substrates, the polishing rate of 3.2 μm/h, which is 64 times higher than the polishing rate of 0.05 μm/h in mechanical polishing, was obtained by applying anodization. Furthermore, by applying ultrasonic vibration to the wafer in addition to anodizing, we achieved a polishing rate of 14.6 μm/h, which is 288 times higher than mechanical polishing.

Free Research Field

超精密加工

Academic Significance and Societal Importance of the Research Achievements

難加工材料であるSiCウエハを陽極酸化により軟質化させ、軟質固定砥粒を用いて改質層を除去することでダメージフリーかつ高能率な研磨を実現し、また、超音波振動をウエハ表面に印加することで酸化を促進することでさらに研磨レートを向上することに成功した。本成果は、従来の化学機械研磨（CMP）における研磨レートを２桁以上凌駕するものであり、研磨技術を革新する点において工学的に大きな意義がある。またCMPでは、薬液を含むために環境負荷が大きなスラリーを研磨液として用いていたが、開発した手法ではスラリーを用いないため環境負荷を低減できる研磨法として社会的な意義を有する。