Effect of Phosphorus Doping on Crystallization-Induced Stress of Silicon Thin Films

The effect of phosphorus doping on the crystallization-induced stress of silicon thin films is discussed experimentally. Amorphous silicon thin films are deposited on thermally-oxidized silicon substrates using chemical vapor deposition. Phosphorus is doped to the film during film deposition using PH3 gas. The initial residual stress of the phosphorus doped films is constant at -200 MPa, regardless of dopant concentration. The internal stress of the films changes to a tensile stress of 800 MPa during crystallization due to film shrinkage. Although the magnitude of the stress change is independent of the dopant concentration, the crystallization temperature of the film decreases with an increase of dopant concentration. The doped phosphorus at the film/ substrate interface affects the crystallization process, i.e., the structure and crystallinity of the silicon thin films. The surface condition of the substrate also affects the crystallinity and crystallization-induced stress of the film.