Flow effects in epitaxial autodoping

A quantitative model has been developed to account for the flow effects in epitaxial autodoping for chemical-vapor-deposited films. Analytical expressions are derived for the autodoping variations along and against the direction of flow arising from a diffusion stripe in the substrate. These expressions relate the maximum concentration in the lateral autodoping peak to the distance from the autodoping source and to the carrier gas velocity. Experimental verification of the model is obtained for arsenic autodoping in silicon epitaxial films, which indicates that boundary layer effects are not predominant in the autodoping phenomenon. The analysis also yields a value of 2.5 cm2/sec for the arsenic vapor diffusivity in hydrogen at 1150 °C.