发明名称 |
Method and apparatus for increasing signal to noise ratio in a photoacoustic film thickness measurement system |
摘要 |
An apparatus for improving the signal to noise ratio of measurements of the thickness of layers in a thin film stack uses a photoacoustic measurement system that includes a time differentiation system for inducing a delay in pump beam pulses. The time differentiation system uses, among other things, a birefringent element and other elements to control the polarization of pump beam pulses. Use of the apparatus involves applying a time varying voltage to an electro-optic modulator driver and setting a time differentiation step; or, in another embodiment, applying a time varying voltage to an electro-optic modulator to induce a fixed time delay delta-t between a vertically polarized pulse and a horizontally polarized pulse. The high frequency operation of the system provides for improved determinations of film thickness.
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申请公布号 |
US2003020929(A1) |
申请公布日期 |
2003.01.30 |
申请号 |
US20020194169 |
申请日期 |
2002.07.12 |
申请人 |
MORATH CHRISTOPHER;STONER ROBERT J. |
发明人 |
MORATH CHRISTOPHER;STONER ROBERT J. |
分类号 |
G01B11/06;G01B11/28;(IPC1-7):G01N21/00 |
主分类号 |
G01B11/06 |
代理机构 |
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地址 |
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