Bird's Beak Configuration and Elimination of Gate Oxide Thinning Produced during Selective Oxidation

Publisher Website
Google Scholar
Abstract
In the selective oxidation scheme for processing Si MOS devices, is used to mask gate oxide areas against the isolation oxidation. After removing the , gate oxide is grown. This scheme produces three topographical features which have ramifications in subsequent processing and in device properties: a notch in the isolation oxide, penetration of the isolation oxide under the masking , and thinning of the gate oxide at the isolation oxide edge; the first two features form the bird's beak configuration. The transmission electron microscope was applied to thin film (<1 μm) cross sections through the bird's beak in order to obtain an accurate description of these features. The bird's beak extended typically 1.5 and 0.8 μm in the n‐ and p‐channel structures, respectively, leading to a corresponding decrease in the active device length of 3.8 and 2.3 μm for the 1.4 μm thick isolation oxide. Gate oxide at the edge of the bird's beak was thinned 35–100% in the n‐channel samples and 20–50% in the p‐channel samples. It was found that oxidation subsequent to the isolation oxidation and removal destroys the oxidation barrier (wet oxidation seemingly more effective than dry and more convenient). Thus, a method which incorporates an additional, short, sacrificial wet oxidation step between isolation and gate oxidations, in order to overcome the thinning phenomenon, is described.

This publication has 0 references indexed in Scilit: