Stress in polycrystalline and amorphous silicon thin films

Abstract

Stress in polycrystalline and amorphous silicon thin films deposited on oxidized silicon wafers is determined from the lengthening of the undercut edge of a silicon stripe. The technique measures only compressive stresses, has a stress resolution of 108 dyn/cm2, and a spatial resolution on the wafer of 250 μm. Unannealed silicon thin films deposited on oxide are under high compressive stress (1010 dyn/cm2). This stress is reduced below the resolution by annealing at 1100 °C for 20 min in N2, except for the thinnest polycrystalline silicon films studied (230 nm thick).