Abstract: A method for revealing the presence of heavy metal impurities that may have been introduced during the formation of a layer, such as the deposition of an epitaxial layer on a semiconductor substrate, uses the constant-magnitude steady-state surface photovoltage (SPV) method for determining the minority-carrier diffusion length by essentially two determination steps. A large ratio of the respective diffusion lengths determined before (actually measured or based on a priori knowledge of similar material) and after the epitaxial deposition step is indicative of the presence of a heavy metal impurity in the epitaxial layer. The method is based on the fact that the contaminating metal distributes itself substantially uniformly not only through the epitaxial layer but also throughout the substrate.

Abstract: A plurality of wafers is serially disposed between a reactant gas inlet portion and an exhaust gas outlet portion of a deposition chamber. The reactant gas comprises a predetermined mixture of N.sub.2 O and SiH.sub.4, and a positive, monotonically decreasing temperature gradient is provided between the wafer closest to the inlet portion to the wafer closest to the outlet portion, such that the thickness and resistivity of the deposited SIPOS (semi-insulating polycrystalline silicon) are substantially similar on each wafer.