光熱変換効果による不透明多層膜厚計測技術(第1報) : 単層膜を用いた共振波計測と粗面の高周波非接触振動計測技術

概要

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We propose the non-contact film thickness measurement method for various materials based on photothermal effect. We illuminate nanosecond pulse laser to the film surface. The various kinds of elastic waves whose maximum frequency is several hundred MHz are excited by photothermal effect. And then, only elastic wave which depends on the film thickness remains selectively, because the resonance phenomena occur between boundary surfaces of the acoustic impedance. The film thickness can be calculated from this detected resonance frequency. In this report, we verified the generation mechanism of resonance wave by photothermal effect. We propose the collector optics type Twyman-green interferometer as the non-contact measurement method for high-frequency vibration of rough surface. In this interferometer, we introduce the objective lens to collect diffused light from rough surface and detect changes of light intensity by high-frequency response photodiode. Using the single layer film whose thickness is 1mm±0.05mm, we can detect the resonance frequency that is 3.1MHz, and the calculated film thickness is 1.035mm.
社団法人精密工学会の論文
2005-12-05