J211012 繰り返し圧縮応力によるシリコン単結晶中の欠陥形成と残存引張強度([J211-01]"壊れない"マイクロシステムのためのナノ力学・ナノ計測(1))

Abstract

In this study, we investigated the possible correlation between fatigue mechanism and internal defects such as dislocation through the fatigue test under cyclic compressive loading. We used specimens made of p-type single crystalline silicon wafer, and prepared with p-n junction and ohmic contact in advance to the fatigue test. The specimen having oval trench was designed for approximately 2.27GPa compressive stress concentration. The fatigue test with a frequency of 20 Hz and range from 1×10^6 to 1×10^7 cycles was performed under controlled atmospheres (80℃, 80% relative humidity). By detecting electron beam induced current (EBIC), growth of internal defects was observed in a scanning electron microscope. After the fatigue test, static fracture strength was reduced by approximately 16% due to the defects induced by cyclic compressive stress. This is likely to be a mechanism determining fatigue lifetime of silicon, as well as a risk to fatigue fracture.