Shallow n+-p junctions were formed by using an  in situ  doped thin polycrystalline Si layer as a diffusion source. The As-doped films were applied by means of rapid thermal processing chemical vapor deposition. Dopant pile-up phenomena were observed at both the polycrystalline Si/Si interface and at the surface. The dopant concentrations were higher at lower deposition temperatures. The observed pile-up phenomena at the polycrystalline Si/Si interface were temperature dependent and were due mainly to As segregation at the grain boundary. The dopant distribution was due mainly to grain boundary diffusion and grain growth mechanisms. Extremely shallow n -p junctions were obtained and laterally uniform delineated junctions were observed. The dopant concentration in the Si substrate fell by 2 orders of magnitude within less than 50nm.

T.Y.Hsieh, H.G.Chun, D.L.Kwong, D.B.Spratt. Applied Physics Letters, 1990, 56[18], 1778-80