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Plasma Oxidation in a Very Dilute Oxygen Plasma to Form a High Quality Interface for PECVD Oxide

IP.com Disclosure Number: IPCOM000102707D
Original Publication Date: 1990-Dec-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 90K

Publishing Venue

IBM

Related People

Bright, A: AUTHOR [+3]

Abstract

This article describes a process which provides a uniform, repeatable, high quality interface on silicon for deposition of plasma enhanced chemical vapor deposition (PECVD) silicon dioxide. This results in a thermal-quality oxide with no high temperature processing.

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Plasma Oxidation in a Very Dilute Oxygen Plasma to Form a High Quality Interface for PECVD Oxide

       This article describes a process which provides a
uniform, repeatable, high quality interface on silicon for deposition
of plasma enhanced chemical vapor deposition (PECVD) silicon dioxide.
This results in a thermal-quality oxide with no high temperature
processing.

      A key aspect of processes for depositing silicon dioxide on
silicon is the initial preparation of the silicon surface so that a
high quality interface (low interface state density, long minority
carrier lifetime, etc.) results.  Such a high quality interface may
be produced by growing a thin oxide layer on the silicon using a
low-power He plasma containing a very low partial pressure of oxygen
or water vapor.  Under these conditions, a plasma oxide is grown with
electrical properties which are much better than conventional plasma
oxides (which are generally grown in pure oxygen at high power), and
in fact are comparable to thermal oxides (which are grown at much
higher temperatures).  This process has been used successfully in
combination with a PECVD silicon dioxide deposition process [1] to
form oxide films of gate quality without the need for high
temperature processing.

      The process as currently practiced uses the following
conditions:
   Power density N0.04 W/cm2 (range 0.02-0.08)
   Total pressure N1 Torr (range 0.5-2)
   Oxygen partial pressure N0.1-100 mTorr
   Diluent gas: He (1000 sccm)
   Process time N10 min. (range 3-30)
   Substrate temperature 350oC

      The power density is sufficiently low that ion bombardment of
the surface is kept below the sputtering threshold.  The pressure and
gas flow conditions were chosen for compatibility with the PECVD
oxide process [1] and tool with which it is used.  This is required
since the process is run immediately prior to the PECVD deposition
process, in the same process chamber.

      Two methods have been used to achieve low levels of oxygen
atoms in the plasma.  The first makes use of the residual atmosphere
in the process chamber (N0.2 mTorr, predominantly water vapor).  The
He plasma causes the water molecules to dissociate into O and H atoms
which are clearly seen i...