Studies of the effects of NF3 on the growth of polysilicon films by low-pressure CVD. Part 1.—Effect on growth rate

Abstract

The control of crystalline quality of polysilicon prepared by low-pressure chemical vapour deposition (LPCVD) is important for device applications. A number of reaction parameters affect this quality and, in general, it has been found previously that layers grown in the amorphous state show good structural perfection and low strain on annealing. We have investigated a new strategy for producing good crystalline polysilicon by attempting to etch layers during the deposition process in order to reduce the size of crystallites in the layers. In this paper we report on the effect of nitrogen trifluoride on the growth rate of polysilicon. We interpret the decreased growth rate in the presence of NF₃ in terms of an etching effect by molecular fluorine and as a result of growth inhibition by strong surface adsorption of the NF₃. The mechanism of this inhibition is discussed.