This paper reports on the strengthening effect of hydrogen anneal on torsional fracture strength of single crystal silicon (SCS). Moving-magnet-type MEMS mirrors were prepared by fabricating SCS and silicon on insulator (SOI) wafers via deep reactive ion etching (DRIE) as fracture test specimens. As a result of the fracture test of the torsion bar on the mirrors, the torsion bar fabricated using a SCS wafer could be strengthened to about 4 times in average by hydrogen anneal. By contrast, that using a SOI wafer was weaken to half. This mechanical strengthening effect has the potential ability to provide highly-reliable and tough SCS-based MEMS devices.
This paper reports on the use of hydrogen anneal to enhance the torsional fracture strength of dry-etched single crystal silicon (SCS) microstructures. Moving-magnet-type scanning mirrors with torsion bars were employed as fracture test specimens. Two types of device were fabricated using SCS and silicon-on-insulator (SOI) wafers by deep reactive ion etching (DRIE). For the SCS-wafer-based device, scalloping on DRIE sidewalls were smoothed out and the fracture strength of the torsion bar was improved by a factor of three by 120 min hydrogen anneal. For the SOI-wafer-based device, hydrogen anneal introduced surface irregularity onto the Si sidewalls by hydrogen-induced etching with the existence of SiO 2 . As a result, the fracture strength of the torsion bar was degraded contrarily. Therefore, hydrogen anneal is effective in improving the mechanical reliability of SCS microstructures without SiO 2 .
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