Topology of Silicon Structures with Recessed SiO2

Abstract

The performance and packing density of silicon integrated circuits can be increased by the use of thermally grown silicon dioxide for the dielectric isolation of the active components of the circuit and by employing fabrication procedures which yield devices with flat surfaces. Using masking, anisotropic etching of the silicon substrate, and thermal oxidation, structures were fabricated in which the was recessed below the original surface. Because of the lateral oxidation under the edge of the mask, a so‐called bird's beak shaped structure is formed at the and interfaces. Factors which influence the surface planarity due to the bird's beak formation have been studied experimentally. This investigation studies the minimization of the bird's beak by using a combination of a thick film, a thin pad, and a suitable thickness of recessed oxide (ROX). Uniform anisotropic etching and parallel alignment to <110> are also required to maintain dimensional control.