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 1017 to 1 x 10 TM cm-3 has been characterized from 1.2 ~m down to 0.1 ~m. 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.

P-type and N-type multi-gate polycrystalline silicon vertical thin film transistors based on low-temperature technology

“…When increasing the active layer thickness, T AC , the smallest threshold voltage, V TH , and the highest field effect mobility, µ FE , are obtained. This indicates a better crystalline quality of the active layer on the sidewall, when increasing T AC , which is consistent with the polysilicon growth kinetics on the planar surface [12]. The rather low mobility µ FE and high threshold slope S are more likely to be due to the high roughness of the sidewalls caused by the long-time of the RIE process.…”

Impact of the Inhomogenous Structure of Polysilicon TFT's Active Layer on the Electrostatic Potential Distribution

“…These heights of potential barriers are more important in the Poly-Si layer having less thickness of active layer. Certainly, the increase in thickness causes a decrease in resistivity, which implies a decrease in height of potential barrier at the grain boundaries [5]. The following figures show a desertion of electrons at the interface for a negative gate voltage equal to -5V in the case of a thickness of 1 µm "Fig.…”