The electrochemical and electronic activities of defects were investigated for excimer laser-annealed polycrystalline Si thin films. Variations in surface geometry and Raman spectra with Secco etching-time were compared for as-crystallized and hydrogenated poly-Si films. In as-crystallized films, etching preferentially attacked defects at the grain boundary. Furthermore, defects in grains were attacked by etching, which was deduced from etching rate and variation in the stress in films. Hydrogenation prior to etching effectively protected defects at the grain boundary, and in grains, from etching. The effects of hydrogenation were interpreted in terms of diminishing localized electronic states related to defects. Hydrogenation followed by Secco etching revealed sub-micron size defects that were attributed to the segregation of oxide lying deep in films. The variation in the Raman spectra with etching time indicated that the local-vibration mode at 2000/cm was related to electrochemically active defects terminated by H; predominantly at grain boundaries. It was also shown that the Raman scattering intensity was strongly modulated by interference in thinned films and the roughness of the etched surface.

Characterization of Defects in Polycrystalline Silicon Thin Films Using Chemical Etching, Hydrogenation, and Raman Spectroscopy. K.Kitahara, H.Ogasawara, J.Kambara, M.Kobata, Y.Ohashi: Japanese Journal of Applied Physics, 2008, 47, 54-8