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Inversion-Free Trench Isolation

IP.com Disclosure Number: IPCOM000101697D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Conti, RA: AUTHOR [+4]

Abstract

Isolation trenches formed in P-type substrate and lined with SiO2 or an Si3N4/SiO2 composite commonly experience sidewall leakage due to high oxide and surface state charge of the MOS or MNOS structure (1). To eliminate this problem, we propose that an Al2O3-SiO2 (AOS)- or an SiO2-Al2O3-SiO2 (OAOS)-lined trench be used. It has been shown that high density negative charge generated in both the MAOS (2) and/or MOAOS (3) structures will be sufficient to prevent surface inversion from occurring.

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Inversion-Free Trench Isolation

       Isolation trenches formed in P-type substrate and lined
with SiO2 or an Si3N4/SiO2 composite commonly experience sidewall
leakage due to high oxide and surface state charge of the MOS or MNOS
structure (1).  To eliminate this problem, we propose that an
Al2O3-SiO2 (AOS)- or an SiO2-Al2O3-SiO2 (OAOS)-lined trench be used.
It has been shown that high density negative charge generated in both
the MAOS (2) and/or MOAOS (3) structures will be sufficient to
prevent surface inversion from occurring.

      These processing steps can be used to construct the aluminum
oxide dual dielectric passivated (AODDP) or oxide-aluminum oxide dual
dielectric passivated (OAODDP) trench sidewall:
 1.  After the trench is opened and the sidewall cleaned, a thin
thermal oxide (less than 50 A) is grown on the trench sidewall.
 2.  A layer of low pressure, low temperature CVD aluminum oxide of
thickness 1500-2400 A is deposited.
 3.  Anneal the structure in an oxidizing ambient at a temperature of
at least 950oC for at least 20 minutes.
 4.  For the AODDP structure, deposit a (1000-3000 A) PECVD SiO2
layer.

      Thereafter, the structure is ready for subsequent device
processing such as trench poly fill.

      Recent data have shown that the AODDP structure has a large
negative charge in its as-formed state and after a post anneal at
temperatures > = 930oC as shown in the figure.  This charge is
sufficient to prevent sidewall inver...