Method of separating semiconductor wafer with dielectrics

Abstract

A method for separating a joined substrate type wafer, which wafer is composed of a pair of semiconductor substrates joined through an insulation film, utilizes dielectrics through simple processing steps. Trenches for separating a semiconductor substrate with dielectrics are dug from the surface of the substrate and a dielectrics film is deposited on the surface of the substrate including the trenches. Then poly-crystalline silicon under layer is grown by CVD method to a thickness of about 0.5 .mu.m. Thereafter, a poly-crystalline silicon filler layer, which is deep enough to fill the trenches, is grown over the underlying poly-crystalline silicon under layer, followed by selectively removing the two poly-crystalline silicon layers from the surface of the substrate excluding the regions inside the trenches. An alternative embodiment contemplates depositing a second dielectrics film interposed between the poly-crystalline silicon under layer and the poly-crystalline silicon filler layer. The overall process substantially increases the insulation between the various semiconductor regions while increasing the smoothness of the dielectrics film by controlling the grain size of the poly-crystalline silicon matrix.