Optical Interferometric Determination of In-Plane Residual Stresses in SiO_2 Films on Silicon Substrates

摘要

Shadow moire interferometry was used to measure the out-of-plane de-flections in 100 mm (4 in.) diameter, 0.5 mm (0.02 in.) thick, (100) p-type silicon wafers that contained thin rf-sputtered SiO_2 films deposited on one side of the wafer. These deflections were used to calculate in-plane residual stresses over a large spatial area of the wafers. Residual stress maps were produced from these measurements. The SiO_2 film thicknesses ranged from 50 to 1600 nm (2 x 10~(-6) to 6.4 x 10~(-5) in.). Benchmark experiments on the silicon wafers without the silica films showed that the in-plane residual stresses are tensile and of the order of 3 MPa (0.45 ksi). The in-plane residual stresses in the films are com-pressive and range from approximately 50 GPa (7.5 x 10~3 ksi) for the 50 nm (2 x 10~(-6) in.) films to 1.2 GPa (180 ksi) for the 1600 nm (6.4 x 10~(-5) in.). The film stress varied with thickness.