In situ monitoring of silicon membrane thickness during wet etching using a surface acoustic wave sensor

Chi Yuan Lee, Ying Chou Cheng, Yung Yu Chen, Pei Zen Chang, Tsung Tsong Wu, Ping Hei Chen, Wen Jong Chen, Shih Yung Pao

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2 Citations (Scopus)


In this paper, we propose a novel method using the surface acoustic wave (SAW) sensor for monitoring in situ the thickness of a silicon membrane during wet etching. Similar to pressure sensors and accelerometers, some micro-electro-mechanical systems (MEMS) devices require the thickness of silicon membranes to be precisely known. Precisely controlling the thickness of a silicon membrane during wet etching is important, because it strongly influences post-processing and device performance. Furthermore, the proposed surface acoustic wave sensor enables the thickness of a silicon membrane, from 50 μm to 80 μm, to be monitored in situ. In summary, the proposed method for measuring the thickness of a silicon membrane in real time from 50 μm to 80 μm, is highly accurate, is simple to implement and can be used for mass production. The principles of the method, detailed process flows, the set up for measuring thickness and simulation and experimental results are all discussed. The theoretical and measured values differ by an error of less than 2 μm; thus the experimental and theoretical values correlate well with each other.

Original languageEnglish
Pages (from-to)3611-3617
Number of pages7
JournalJapanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers
Issue number6 A
Publication statusPublished - 2004 Jun


All Science Journal Classification (ASJC) codes

  • Engineering(all)
  • Physics and Astronomy(all)

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