Measurement of stress gradients in hydrogenated microcrystalline silicon thin films using Raman spectroscopy

Raman spectroscopy is a powerful tool to measure stress in semiconductors. We show both large stress values and stress gradients in hydrogenated microcrystalline silicon thin films, by the use of different excitation wavelengths, from red to near-ultraviolet, allowing us to probe different film depths. For films deposited by standard radio frequency glow discharge at different substrate temperatures, we find that stress evolves from highly compressive in the bulk of the film, close to the glass substrate, to tensile near the film free surface. Moreover, the higher the substrate temperature, the higher the stress gradient.