Abstract
The double-patterning lithography technology for next generation semiconductor manufacturing requires ultra high positioning stability such as under 0.5nm position drift between wafers. Conventional laser interferometers or optical grating encoders will not be adequate for that system. In the beginning of this study we quantify the requirements of the double-patterning lithography with Allan variance. This variance was developed for frequency oscillator stability tests. It can show the performance of stabilities related with operation time ranges in a quite understandable form. We evaluated the stability of our new concept scanning optical encoder using this variance.This new sensor is quite robust against electric and optical drift because of phase synchronous detection technology in a FPGA chip and a compensation grating in the optics. The compensation grating cancels most of outer disturbances such as laser wavelength changes or incident angle fluctuations of laser beams. Finally we conclude this new method improves low frequency drift performance of optical grating encoders. It will be adequate for next generation semiconductor manufacturing.
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