Development of simultaneous measurement method for geometrical thickness and refractive index of transparent plate by tandem low-coherence double-sided interferometer

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K05321
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 30020:Optical engineering and photon science-related
• Research Institution: National Institute of Advanced Industrial Science and Technology
• Principal Investigator: Hirai Akiko 国立研究開発法人産業技術総合研究所, 計量標準総合センター, 研究グループ長 (00357849)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 干渉計測 / 低コヒーレンス干渉 / 厚さ計測 / 屈折率

Outline of Final Research Achievements

The purpose of this research is to establish a technique to measure the geometric thickness of transparent substrates with high reliability. Addition to that, to establish a technique to simultaneously measure the refractive index dispersion of the sample is subsidiary purpose. For these purposes, a tandem low-coherence double-sided interferometer was developed. To confirm the principle, the geometric thickness of a silicon wafer was measured using low-coherence light in the visible region. The obtained thickness distribution was in good agreement with the results obtained with an existing double-sided interferometer using laser light in its shape and range, however, the difference in the absolute value of the thickness was greater than the target uncertainty. In the future, we will improve the measurement accuracy of the absolute thickness and work on the precise measurement of the thickness distribution of the transparent substrate.

Free Research Field

光計測

Academic Significance and Societal Importance of the Research Achievements

本技術開発により、国際単位系にトレーサブルに透明試料の絶対幾何学的厚さの測定が達成できる。また、同一の系で同じ箇所の屈折率分散も測定できる。試料内部の屈折率分布は、不純物濃度分布や歪み分布が反映されているので、加工条件との相関を調べれば、より高品質な半導体用基板製造技術への波及効果が期待される。