Investigating the influence of fabrication process and crystal orientation on shear strength of silicon microcomponents

摘要

A summary of the influence of microfabrication processes (wet and dry etching) and crystal orientation on the effective shear strength of microridges is addressed in this paper. Test results indicate that both crystal orientation and geometry plays an important role in determining the strength. The largest shear strengths obtained were for triangular and rectangular ridges fabricated with wet etching and deep RIE respectively. Both of these structures had similar crystal orientations. These strength values were approximately 3.5 times larger than the lowest strengths measured for wet etching structures. Using Chlorine RIE, we were able to demonstrate the influence of crystal orientation on strength, with microridges of {110} sidewall made on a (100) wafer the largest. For wet etching, we found that the strength was concentration dependent. For example, a 45% KOH fabricated structure produced strength values 65% higher than 30% KOH fabricated ones (note crystal orientation the same). This was attributed to a geometric effect, that is the 45% KOH solution had a "V" shaped bottom while the 30% KOH had a flat bottom. EDP and TMAH values had similar strengths to the 30% KOH solution (note similar crystal orientation). Therefore, microcomponent strength is strongly dependent upon fabrication process as well as crystal orientation.