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首页> 外文会议>ICO20: Optical Devices and Instruments >Vibration insensitive interferometer using sinusoidal phase-modulation and feedback control
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Vibration insensitive interferometer using sinusoidal phase-modulation and feedback control

机译：使用正弦相位调制和反馈控制的振动不敏感干涉仪

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It is easy to extract a signal proportional to a phase fluctuation from a sinusoidally phase-modulated interference signal. This fluctuation is caused by mechanical vibration or air turbulence. In a sinusoidal phase-modulating interferometer using a laser diode (LD) the phase fluctuation is reduced by changing the injection current of the LD with a feedback control system. This control is very useful to a Fizeau type interferometer for surface profile measurement of a large size object. IC wafers of 100 mm diameter are measured with an interferometer insensitive to mechanical vibration and air turbulence. The phase fluctuation with nearly constant amplitude which corresponds to 30nm in surface height is reduced by about 10%. However the reduction in the phase fluctuation is not performed well for an instantaneous and large phase fluctuation. In order to be insensitive to all kinds of phase fluctuations the feedback signal is always observed, so that the interference signal is captured when the amplitude of the feedback signal is less than a specified level during the capturing time of 0.53 s. Thus surface profiles of the IC wafers can be measured with a high repeatability of a few nm even when any kind of vibration exists.
机译：从正弦相位调制的干扰信号中提取与相位波动成比例的信号很容易。这种波动是由机械振动或空气湍流引起的。在使用激光二极管（LD）的正弦相位调制干涉仪中，通过使用反馈控制系统改变LD的注入电流来减小相位波动。此控件对于用于大型物体表面轮廓测量的Fizeau型干涉仪非常有用。使用对机械振动和空气湍流不敏感的干涉仪测量100毫米直径的IC晶圆。幅度近似恒定的相位波动（对应于表面高度30nm）减少了约10％。但是，对于瞬时且大的相位波动，不能很好地减小相位波动。为了对各种相位波动不敏感，始终会观察到反馈信号，以便在0.53 s的捕获时间内，如果反馈信号的幅度小于指定的水平，则捕获干扰信号。因此，即使存在任何种类的振动，也可以以几nm的高重复性来测量IC晶片的表面轮廓。

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