Abstract
We have investigated 3D profiling of the objects by low coherence optical interferometer using MEMS grating. This system, constructed with optical fibers and MEMS devices, is Fourier domain interferometer, which can discriminate distance to the object by wavelength analysis of the interference spectra. A MEMS mirror gives the object 2D optical scanning, and a MEMS grating makes spectroscopy of interference spectra. The MEMS grating can tilt to dual-axis with electromagnetic force induced by planer coils and a permanent magnet. One axis tilting works as near infrared spectroscopy, and another axis tilting works as optical axis alignment in an interferometer. Fabricated MEMS grating could tilt ±3.5° (mech.) / less than ±10mA in both direction at low frequency, which were equivalent to approximately 1400-1700nm in wavelength. This interferometer, whose S/N was 50dB and vertical standard deviation was 0.6µm, could scan full wavelength width (1400-1700nm) in 25ms. Finally, we could realize 3D profiling which was not only surface reflection profiling of 1µm step, but also transparent profiling of IC process layer from backside of the wafer.
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