An investigation of the mechanical strengthening effect of hydrogen anneal for silicon torsion bar

Abstract

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 .

Effect of crystallographic orientation on tensile fractures of (100) and (110) silicon microstructures fabricated from silicon‐on‐insulator wafers

“…The sidewall surfaces are damaged as isotropic plasma etching and passivation steps are alternately repeated when creating a structure, and critical locations where surfaces meet may be unevenly etched, such as at the boundaries between the silicon substrate and mask patterns or buried oxide layers. Since these defacements act as fracture origins, the effect of surface damage upon fracture properties [9,10] and postprocessing treatment techniques [11][12][13] have been investigated, in order to improve the reliability of silicon structures.…”

Fracture behavior of single-crystal silicon microstructure coated with stepwise bias-graded a-C:H film

“…Two-parameter Weibull analysis was conducted in our analysis since it is appropriate for evaluating the strength deviation of brittle materials, whose measured data is widely scattered [34]. Fig.…”

Silicon migration seal wafer‐level vacuum encapsulation

“…This section discusses the influence exerted on internal MEMS structures by H 2 annealing process to close vent holes in cap wafer. For example, it was proposed to utilize silicon migration effect in order to suppress socalled scallops (ripples left on sidewalls after Deep RIE processing) 11,12 ; depending on the setting of SMS packaging conditions, favorable results can be also obtained for internal MEMS structures. On the other hand, in the experiments, vent holes with nominal diameter (dn) of 0.7 μm were not closed, but the surface diameter shrank about -0.3 μm on one side (Figure 3).…”