Surface damage of single-crystal silicon abraded in ethanol and deionized water

Abstract

Semiconductor grade, single-crystal silicon wafers of (1 0 0) p-type were abraded by a single-point, slow speed (2.3 cm sec⁻¹) 90° pyramid diamond in ethanol and deionized water. The scratching was carried out in each of the fluids with a load of 0.5 N on the sliding diamond. The scratching produces a groove, the depth of which depends on the number of traverses of the diamond. A measure of the cross-sectional area of the groove was used to determine the abrasion rate in ethanol, which was about 1.3 times that in deionized water. Some of the samples scratched in deionized water were annealed at 1000° C for 1 h and these samples, along with those unannealed and scratched in both fluids, were fractured perpendicular to the scratch in a three-point bend apparatus. The fracture strengths and the mirror distances obtained by scanning electron microscope (SEM) observation were used to deduce tensile residual stresses of 15.6 and 99.0 MN m⁻² beneath the grooves formed in deionized water and ethanol, respectively. The SEM investigation also showed that (a) the groove surfaces contained microcracks wedged with wear debris, and (b) dislocations were generated and propagated away from the groove surfaces as a result of annealing. The relatively higher tensile residual stress produced in the presence of ethanol is consistent with the higher wear rate in this fluid.