The Critical Shear Stress for Slip Generation due to Scratches in Silicon Wafers

Abstract

The relationship between slip dislocations generation due to scratches on silicon wafers and oxygen concentration has been investigated by three-point bending tests at high temperatures from 973 to 1123 K. We have measured the critical shear stresses for slip initiation caused by surface scratches as the onset of dislocation motions. In addition to the locking effect by oxygen atoms of dislocations, it was found that strain rate also has an important role on the value of the critical stress for slip generation caused by scratch. In order to take into account the effect of the strain rate, a new empirical equation as a function of strain rate for the estimation of critical shear stress was developed using the results with the three-point bending in this study. The equation obtained in this work indicates that ramp rates in the thermal process of wafer have a crucial effect on the slip dislocation generation. The estimation of critical shear stress of slip dislocation using this equation shows a good agreement with the experimental results of a heat treatment process.