| Summary: | 碩士 === 國立清華大學 === 動力機械工程學系 === 89 === This thesis presents the study of a tunable phase grating using CMOS processes. Grating is an important and popular element in optical systems such as spectrometer. Due to the requirement of high precision, grating devices are expensive based on traditional manufacturing techniques. Using micromachining technique, we can fabricate high-precision, high-performance, but low-cost grating devices.
Grating pitch is an important parameter in grating devices. It not only governs the diffractive angle but also affects the dispersion performance. The narrower grating pitch is, the better dispersion efficiency and resolution power will be in general. With CMOS processes, sub-micron structure can be easily approached. In our grating devices, using UMC 0.5μm CMOS processes, we have 0.7μm ribbon-width and 0.65μm spacing between ribbons. This means our tunable grating has a grating pitch of 1.34μm. We used aluminum as ribbon material and SiO2 as sacrificial layer in our design. The ribbons were released via RIE to remove the SiO2 sacrificial layer. In our devices, we have successfully released the ribbons with the width from 0.7μm up to 2μm. The dry etching processes, which we developed to release ribbons in our devices, can avoid problems of sticking and structure destruction. For electrostatic actuator, we used partial electrode design to obtain wider flat-reflection sections, and larger steady tuning distance. In this thesis, we describe design, modeling, simulation early, measurements and result discussion of our tunable grating devices.
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