Formation of cylindrical insulation layer in semiconductor substrate - using self-aligned etch process resulting in smooth field oxide on top surface

摘要

An insulated layer for use in a semiconductor device is formed by etching a narrow and deep cylindrical trench, filling it with an oxide layer and oxidising a polycrystalline Si layer. A process is also claimed. The process consists of forming an oxide layer on a Si surface followed by a nitride layer. Using a resist process a window is defined and etched. Then a polySi layer is deposited and channel stopper dopants implanted through it. The surface is planarised by deposition of an oxide layer which forms a plug in the etched window and is etched back until the polySi is reached. The Si exposed at the surface is then etched back and the process continued into the substrate where no masking oxide or nitride is present. Then a CVD oxide layer is deposited and etched back using a dry etch process until the polySi layer is laid bare. Then the polySi layer is oxidised and the nitride layer removed. USE/ADVANTAGE - The process is self-aligned, with the width of the trench defined by the thickness of the polySi layer. The field-oxide layer on top of the structure is even and without ripples.