STUDIES OF THE EFFECTS OF NF3 ON THE GROWTH OF POLYSILICON FILMS BY LOW-PRESSURE CVD .1. EFFECT ON GROWTH-RATE

The control of crystalline quality of polysilicon prepared by low-pres sure chemical vapour deposition (LPCVD) is important for device applic ations. A number of reaction parameters affect this quality and, in ge neral, 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 polys ilicon by attempting to etch layers during the deposition process in o rder to reduce the size of crystallites in the layers. in this paper w e report on the effect of nitrogen trifluoride on the growth rate of p olysilicon. We interpret the decreased growth rate in the presence of NF3 in terms of an etching effect by molecular fluorine and as a resul t of growth inhibition by strong surface adsorption of the NF3. The me chanism of this inhibition is discussed.