(110)シリコンの高温下のすべりと破壊に及ぼす引張軸方位の影響

Abstract

Tensile testing of single crystal silicon microstructures was performed along tensile axes of <110> and <111> at 500 °C in a vacuum to investigate crystallographic effects on their slip occurrences and fracture behaviors at the high temperature. Specimens with parallel portions 120 μm long, 2 μm wide, and 5 μm thick, were designed along the two tensile axes on (110) wafers, and were fabricated from SOI (silicon-on-insulator) wafer using UV lithography and deep RIE (reactive ion etching) processes. The specimens were subjected to tensile testing at 500 °C in a vacuum, which exhibited linear stress increments until their fractures at 3.2 GPa on <110> and at 4.0 GPa on <111>. Contrary to the obtained linear nominal stress increments, fractured specimens possessed surface steps due to slip along {111}. The fracture surfaces exhibited large planes oriented mostly along {111} indicating cleavage fracture behaviors. Stress concentration around the surface step was analyzed employing finite element method to discuss effect on the surface step on decrease in nominal tensile strength at a high temperature, and criteria for slip were discussed based on maximum shear stress along the slip system.