RAMAN MICROPROBE ANALYSIS OF STRAINED POLYSILICON DEPOSITED LAYERS

Microscopic strain distributions in varying thicknesses of polysilicon layers deposited as bridges over silicon substrates were determined b y high resolution micro-Raman spectroscopy. In particular, we mapped t he dependence of the first order Raman spectrum as a function of the p osition across polysilicon bridges (approximately 550 X 230 mu m(2)), over tunnels etched in the silicon substrate. Shifts in Raman band fre quencies as a function of position on the bridge structures were obser ved to be dependent upon the thickness of the membrane layer (between 1 and 3 mu m) as well as the annealing conditions. Assuming a simplifi ed uni-axial stress parallel to the surface, the effective tensile str ess at the center of the bridge of thickness 2.5 mu m is reduced by an nealing from 2.5 GPa to 0.18 GPa. (C) 1998 Elsevier Science B.V.