Young's modulus and residual stress of polycrystalline 3C-SiC films grown by LPCVD and measured by the load-deflection technique

Polycrystalline silicon carbide (poly-SiC) thin films were grown in a large-volume, low-pressure chemical vapor deposition (LPCVD) furnace using dichlorosilane (SiH2Cl2) and acetylene (C2H2) precursors. The deposition temperature was fixed at 900degreesC and the pressure was varied between 0.46 and 5 Torr. The load-deflection technique was used to determine the Young's modulus and residual stress of the as deposited poly-SiC films using bulk micromachined poly-SiC suspended diaphragms. The results indicated the residual stress of poly-SiC films changed from high tensile to low tensile stress as the deposition pressure increased from 0.46 to 2.5 Torr, which was consistent with results obtained from wafer curvature measurements. The Young's modulus of the films was independent of deposition pressure and averaged 396 GPa. Bent-beam strain gauges were also fabricated and used to measure the stresses in films exhibiting low compressive and tensile residual stresses. Measurements from these structures were consistent with the wafer curvature and, in the case of tensile films, the load-deflection measurements.