Method of producing amorphous silicon for hard mask and waveguide applications

Abstract

A specialized physical vapor deposition process provides dense amorphous semiconducting material with exceptionally smooth morphology. In particular, the process provides dense, smooth amorphous silicon useful as a hard mask for etching optical and semiconductor devices and as a high refractive index material in optical devices. DC sputtering of a planar target of intrinsic crystalline semiconducting material in the presence of a sputtering gas under a condition of uniform target erosion is used to deposit amorphous semiconducting material on a substrate. DC power that is modulated by AC power is applied to the target. The process provides dense, smooth amorphous silicon at high deposition rates. A method of patterning a material layer including forming a hard mask layer of amorphous silicon on a material layer according to the present DC sputtering process is also provided. The low average surface roughness of the amorphous silicon hard mask is reflected in the low average surface roughness of the sidewalls of the etched material layer. In addition, a method of forming optical devices in which the DC sputtered amorphous semiconductor materials are used as the high refractive index material is provided.