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

Abstract

This paper investigates the effect of crystallographic orientation on tensile fractures of silicon microstructures. Specimens 5 μm wide and 5 μm thick were fabricated on (100) and (110) wafers with <100>, <110>, and <111> tensile axes. To explore the effects of different surface orientations and morphologies, these specimens were patterned from (100) and (110) silicon-on-insulator (SOI) wafers using the Bosch process under identical fabrication conditions, while other specimens were fabricated from (110) wafers under different conditions. Tensile tests of specimens prepared under the identical fabrication conditions showed that (100) specimens had lower strength than (110) specimens along <100> and <110> axes; the average strength decreased from 3.62 GPa to 3.14 GPa for <110>. This decrease in strength is related to differences in damage that ultimately causes fractures. While (110) specimens fractured due to fabrication damage at top corners, fractures of (100) specimens were due to pit-like defects on bottom surfaces. Since these defects were introduced during SOI bonding processes, the fractures of (100) specimens were dominated by intrinsic SOI defects rather than damage introduced during specimen fabrication processes. To realize higher-strength structures on SOI wafers, both the damage caused during fabrication and the intrinsic defects need to be controlled.

Tensile Strength of Silicon Nanowires Batch-Fabricated into Electrostatic MEMS Testing Device

“…As mentioned above, the thickness uniformity of the EB resist should have been improved by optimizing the coating process, and the width of the openings near the specimen should have been revised. The tensile strength was comparable to the microscale specimens [27], which we did not expect to find. As a result of the surface oxidation process, the surface of the silicon would have been smoothed of any roughness that was caused by patterning, such as the jagged edge of the EB resist and the scallops that were generated in the Bosch process.…”

Nanometer Order Separation Control of Large Working Area Nanogap Created by Cleavage of Single-Crystal Silicon Along {111} Planes Using a MEMS Device

“…It has been reported that cleavage along the (110) plane deflects onto to the (111) plane because of bond reconstruction near the crack tip [20], making it unstable and unsuitable for obtaining nanogaps with large-area smooth surfaces. On the other hand, cleavage along the (111) plane is not disrupted by deflection and produces smooth surfaces, as reported by the Uesugi et al [21] Therefore, cleavage along the {111} plane is adopted in this study. This can be achieved by using (110) oriented silicon wafers because (111) plane exists in the direction orthogonal to (110) planes.…”

Mechanical reliability of silicon microstructures

“…There is a significant difference in the Weibull modulus of measured tensile strength among the three orientations. The <111>-direction specimen shows a smaller deviation than the <110>-and <100>-direction specimens, which may be due to the smooth fracture surface of the <111>-direction specimen [47].…”

“…The crystallographic orientation effect has been investigated [16,47,48]. The tensile strength does not show significant differences among specimens with three major inplane orientations: <100>, <110> and <111> axial directions}.…”