Measurement of the in-depth stress profile in hydrogenated microcrystalline silicon thin films using Raman spectrometry

Raman spectrometry is used to measure stress in hydrogenated microcrystalline silicon thin films. Moreover, by the use of different excitation wavelengths, from red to near ultraviolet, we can probe different film depths and get information on the stress distribution along the growth direction. For films deposited by standard rf glow discharge at different substrate temperatures, on glass substrates, we found large stress gradients. Indeed, the high compressive stress (up to 1 GPa) in the bulk of the film, close to the glass substrate, reduces and becomes tensile as the film free surface is approached. Moreover, the higher the substrate temperature, the higher the stress gradient.