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Reducing Lateral Oxidation in Recessed Oxide Isolated Structure

IP.com Disclosure Number: IPCOM000084341D
Original Publication Date: 1975-Oct-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Rideout, VL: AUTHOR

Abstract

A major concern with all recessed-oxide (ROX) isolation processes, is the extent of the lateral oxidation (bird's beak effect) produced during processing which reduces the silicon surface area available for active devices. The lateral oxidation occurs due to oxygen diffusing along the oxide pad under the nitride oxidation mask.

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Reducing Lateral Oxidation in Recessed Oxide Isolated Structure

A major concern with all recessed-oxide (ROX) isolation processes, is the extent of the lateral oxidation (bird's beak effect) produced during processing which reduces the silicon surface area available for active devices. The lateral oxidation occurs due to oxygen diffusing along the oxide pad under the nitride oxidation mask.

The objective is to minimize the oxide pad thickness, maximize the nitride layer thickness, and minimize the undercut etching of the oxide pad without significantly degrading device performance. The present ROX processes address the three factors listed above. Still the bird's beak effect occurs and remains a problem which preferably should be further minimized. At least three solutions may be feasible:
1. Increase the vertical oxidation rate in the ROX regions, by

ion implantation damage.
2. Decrease the lateral oxidation rate in the nitride masked Si

device regions by an oxy-nitride layer.
3. Use another material, such as W, moly, or Al(2)O(3) to

hold down the nitride to prevent curling, and to reduce

undercut etching of the oxide pad.

This description is primarily concer ed with the first technique. First it is recognized that an implantation mask is already in place, with the purpose of masking the boron channel-stopper implant in the device regions. This mask can also be used for another purpose, namely to mask the device regions from a damage-inducing implant in the subs...