Browse Prior Art Database

Defect Free Si in Regrown SIMOX Structures

IP.com Disclosure Number: IPCOM000109184D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 2 page(s) / 87K

Publishing Venue

IBM

Related People

Davari, B: AUTHOR [+3]

Abstract

SIMOX is an attractive method for producing silicon-on-insulator starting material because the superficial Si and buried oxide thicknesses can be easily controlled by the implantation energy and dose. One difficulty commonly observed with this material is concentrations of defects in the superficial Si; another difficulty is that disorder in the Si crystal can be present near the bottom interface. These factors can limit the minimum thickness of the Si layer usable in MOSFETs. For example, if the disorder and defected regions extend over a 200-400 Angstrom range, the minimum thickness usable for devices and circuits would be 600 to 800 Angstroms. With present SIMOX fabrication methods, there is no method for overcoming this problem.

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Defect Free Si in Regrown SIMOX Structures

       SIMOX is an attractive method for producing
silicon-on-insulator starting material because the superficial Si and
buried oxide thicknesses can be easily controlled by the implantation
energy and dose.  One difficulty commonly observed with this material
is concentrations of defects in the superficial Si; another
difficulty is that disorder in the Si crystal can be present near the
bottom interface.  These factors can limit the minimum thickness of
the Si layer usable in MOSFETs.  For example, if the disorder and
defected regions extend over a 200-400 Angstrom range, the minimum
thickness usable for devices and circuits would be 600 to 800
Angstroms.  With present SIMOX fabrication methods, there is no
method for overcoming this problem.

      The present invention outlines a method for greatly reducing
and possibly eliminating the high defect densities present in SIMOX.
The details of the method are outlined in Figs. 1-5.  Normally the
heavy dose of oxygen (1.8e18 cm-3, 200 keV) is implanted into a blank
Si wafer.  In the invention, the oxygen implant is carried out into a
wafer on which a masking pattern of material such as SiO2, Si3N4, a
metal such as W, or other material has been placed (Fig. 1).  The
oxygen implant is carried out as normal, but underneath the masked
regions the Si remains implant-free except for the straggle that
occurs laterally (Fig. 2).  The masking material can then be removed,
or i...