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Process Sequence for Forming a Recessed Oxide Isolation Structure With Minimum Lateral Oxidation

IP.com Disclosure Number: IPCOM000101906D
Original Publication Date: 1990-Sep-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 40K

Publishing Venue

IBM

Related People

Euen, W: AUTHOR [+2]

Abstract

The described process sequence drastically reduces the lateral oxidation while increasing the oxidation rate in the regions where the recessed oxide is to be formed.

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Process Sequence for Forming a Recessed Oxide Isolation Structure With Minimum Lateral Oxidation

       The described process sequence drastically reduces the
lateral oxidation while increasing the oxidation rate in the regions
where the recessed oxide is to be formed.

      The general approach used to produce a recessed oxide isolation
structure leads to what is known as a "bird's beak" which is formed
by lateral oxidation under the edge of the masking nitride layer.
This undesired effect increases the area required for building a
semiconductor device, e.g., a storage cell.  The length of the bird's
beak can be influenced to some extent by optimizing the thickness of
the pad structure.  However, the improvement obtainable thereby is
minimal.

      In the process sequence described, which serves to minimize the
lateral oxidation, arsenic is implanted in those regions where the
pad nitride, used as a mask during the recessed oxide growth process,
is removed.  The energy of the implant is chosen such that the depth
of the arsenic peak concentration is close to the surface of the
silicon wafer.  The subsequent oxidation process takes place at 600oC
in a wet ambient.  At such a low temperature, an oxide thickness
ratio (implanted silicon regions to unimplanted silicon regions) of
7.7 to 45 is achieved, depending on the final thickness of the
recessed oxide.  An arsenic dose of 2.016 cm2 yielded optimal results
with respect to an increase in the oxidation r...