Impact of the polysilicon doping level and thermal oxidation on the properties of P-MOS capacitor structures

Abstract

In this paper, we present a study of different parameters characterising polysilicon/oxide/monosilicon structures, after extraction from the capacitance voltage C(V) and conductance voltage G(V) curves, at high frequency (1 MHz). The polysilicon films are elaborated by chemical vapour deposition at low pressure (LPCVD) from silane (SiH4) and boron trichloride (BCl3) gas mixture, at a temperature of 605°C. They have been subjected to thermal annealing in dry oxidising atmosphere at temperatures ranging between 850 and 1,100°C. The extraction of parameters such as the doping level at the oxide substrate interface, the flat band voltage, the oxide thickness and the interface states density has shown that they are strongly influenced by oxidation treatments and doping level. The results show that there are two competing phenomena in the case of boron doped polysilicon gate: the polydesertion and the diffusion. The study has demonstrated the polysilicon’s ability to play the gate’s material role, while preserving the dielectric’s quality on which it is deposited.