Browse Prior Art Database

Thermal Oxide Growth in Integrated Vacuum Processing Systems

IP.com Disclosure Number: IPCOM000101216D
Original Publication Date: 1990-Jul-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 102K

Publishing Venue

IBM

Related People

Liehr, M: AUTHOR [+3]

Abstract

Disclosed here is a method for achieving high quality thermal SiO2 film growth in a multichamber integrated processing environment, which typically involves vacuum (or ultrahigh vacuum) wafer transfer chambers acting as load locks for introducing wafers into the oxidation reactor. In such systems it is possible, by integrated surface cleaning in one reactor chamber with oxidation in another, to achieve clean (oxygen- free) silicon surfaces before oxidation; in these cases the teaching of this disclosure may be essential to realizing high quality oxide material (e.g., high dielectric breakdown fields). The essential point is to raise the temperature of the wafers to oxidation temperature in such a way that the silicon surface is slightly oxidized during this ramp-up, rather than etched by trace concentrations of oxygen.

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Thermal Oxide Growth in Integrated Vacuum Processing Systems

       Disclosed here is a method for achieving high quality
thermal SiO2 film growth in a multichamber integrated processing
environment, which typically involves vacuum (or ultrahigh vacuum)
wafer transfer chambers acting as load locks for introducing wafers
into the oxidation reactor.  In such systems it is possible, by
integrated surface cleaning in one reactor chamber with oxidation in
another, to achieve clean (oxygen- free) silicon surfaces before
oxidation; in these cases the teaching of this disclosure may be
essential to realizing high quality oxide material (e.g., high
dielectric breakdown fields).  The essential point is to raise the
temperature of the wafers to oxidation temperature in such a way that
the silicon surface is slightly oxidized during this ramp-up, rather
than etched by trace concentrations of oxygen.

      Smith and Ghidini (*) established some time ago the phase
boundary which separates Si oxidation (Si + O2 T SiO2) from Si
etching by O2 (2Si + O2 T 2 SiOI).  At O2 concentrations below the
boundary, etching dominates, while net oxidation of the surface
occurs above the boundary. Because of the thermal activation energy
involved (essential that for SiO product desorption), the boundary
moves to higher O2 concentration at higher temperature.  The data of
(*) treats the case where low concentrations of oxygen were present
in a vacuum ambient, but one can expect that a qualitatively similar
behavior will arise in the case of low oxygen concentrations in an
inert, atmospheric pressure ambient (e.g., an oxidation or annealing
furnace without the intentional presence of oxygen).

      One might expect that etching of the silicon surface prior to
thermal oxide growth would be deleterious to oxide dielectric
strength, because the random statistics of etching inevitably causes
microscopic roughening of the surface.  In contrast, if the silicon
surface is always maintained in oxidation conditions (rather than
etching conditions), etching and roughening of the surface should be
prevented, and dielectric quality maintained.  Preliminary results
demonstrate this systematics.

      In standard oxidation situations, wafer preclean can remove
surface oxide.  However, upon transporting the wafer through air and
particularly upon heating up the wafer as it is moved in
oxygen-containing air into the oxidation furnace, the surface is
always exposed to O2 an...