9 January 2008 Fabrication of smooth 45° micromirror using TMAH low concentration solution with NCW-601A surfactant on <100> silicon
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Abstract
Paper reports improved results in the fabrication of 45° micromirrors using low concentration of TMAH with NCW-601A surfactant. 45° micro mirror is an essential component for obtaining 90° out-of-plane reflection of the optical beam. TMAH anisotropic wet etching on (100) silicon wafer with features aligned to the flat so that 45° slope is formed on (110) plane. This requires the etch rate of <110> planes to be lower than <100> planes. Etching rate selectivity depends on: temperature, concentration, and additives. Substantial undercutting of mask needs to be taken into consideration during the design. TMAH concentrations ranging from 2.5% to 10% with different concentrations of surfactant have been studied to achieve improved smoothness of the micromirror surface and better selectivity. SEM/AFM measurement show the roughness of mirror is less than 1nm. Results also show that the surface roughness varies along the 45° slope with the roughest portion at the top of the mirror. This paper will describe the techniques to reduce the size of the rough portion of the mirror.
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Yi Wei Xu, Aron Michael, Chee Yee Kwok, "Fabrication of smooth 45° micromirror using TMAH low concentration solution with NCW-601A surfactant on <100> silicon", Proc. SPIE 6800, Device and Process Technologies for Microelectronics, MEMS, Photonics, and Nanotechnology IV, 68001W (9 January 2008); doi: 10.1117/12.759343; https://doi.org/10.1117/12.759343
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