The Effect of film thickness on the electrical properties of LPCVD polysilicon films

Abstract

The effect of film thickness on the electrical properties of boron-doped LPCVD polysilicon films with doping concentration ranging from 1 x 1017to 1 x 1019cm-3 has been characterized from 1.2 μm down to 0.1 μm. The resistivity increases exponentially as the film thickness decreases, rather than remaining constant, and the rate of increase is a strong function of doping concentration. After a quantitative study on the physical mechanisms which can affect the resistivity as film thickness decreases, the carrier trapping effect due to grain-size variation at different film thicknesses is shown to be the dominant factor. A trapping model without assuming the depletion approximation can explain well the experimental data and enhances understanding of the resistivity behavior as the polysilicon film thickness decreases. © 1984, The Electrochemical Society, Inc. All rights reserved.