Fluorine Implantation and Residual Stresses in Polysilicon Films

Abstract

X-ray diffraction techniques were utilized to study the film stress effects in silicon wafers subjected to several processing conditions. The wafer processing matrix consisted of three thicknesses of polysilicon deposited on (100) silicon with a 25 nm layer of SiO{sub 2}. The polysilicon was doped with phosphorous and arsenic after which the samples were implanted with fluorine at 30 KeV at a dose of 6 x 10{sup 15} cm{sup 2}. A synchrotron radiation source at Brookhaven National Laboratory on beamline X-14 was employed to determine the residual stresses in the polysilicon film by a powder diffraction technique ordinarily used on polycrystalline material. X-ray rocking curve experiments were employed to determine the stress in the film from measurements of the curvature of the substrate. These two stress measurements allow the estimation of the stress gradient in the intermediate amorphous oxide layer. Correlations are made between the stress gradients, the fluorine distribution in the wafer and the electrical characteristics of the structures. 15 refs., 6 figs., 2 tabs.