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Gate Quality Thin Oxide by Plasma Oxidation in a Very Dilute Oxygen Plasma

IP.com Disclosure Number: IPCOM000102705D
Original Publication Date: 1990-Dec-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 94K

Publishing Venue

IBM

Related People

Bright, AA: AUTHOR

Abstract

A process is described which provides a high quality thin oxide (<~50Ao) at low processing temperatures. The oxide has excellent interface properties, good uniformity, and low defect density and may be suitable for use as a gate oxide in sub-.25mm MOS devices.

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Gate Quality Thin Oxide by Plasma Oxidation in a Very Dilute Oxygen Plasma

       A process is described which provides a high quality thin
oxide (<~50Ao) at low processing temperatures.  The oxide has
excellent interface properties, good uniformity, and low defect
density and may be suitable for use as a gate oxide in sub-.25mm MOS
devices.

      Plasma oxidation or plasma anodization is widely used for
growing relatively thick silicon oxides at high growth rates without
the use of high processing temperatures.  The electrical properties
of such oxides are poor compared to thermal oxides, however.  This
article describes a new plasma oxidation process which produces
reproducible thin oxides of gate oxide quality by using a low power
plasma containing a very low partial pressure of oxygen or water
vapor in He.  Under these conditions the oxide growth rate is reduced
and the film quality is much higher than conventional plasma oxides.

      The process as currently practiced in a batch PECVD system is
similar to the interfacial oxide process described in (1).  Oxygen is
provided in the plasma either by direct doping of the He with O2 . or
by making use of the residual water vapor in the process chamber.
Using either method, an oxide of about 30 Ao is grown in 10 minutes.
The maximum oxide thickness (after an hour) is about 50 Ao .

      Electrical measurements of the interface properties of MOS
structures made with these films are difficult due to problems with
annealing aluminum-gate devices with very thin oxides.  The interface
properties can, however, be inferred from measurements of thicker
oxides composed of the plasma oxide at the interface plus a thicker
PECVD oxide overlayer (1).  Excellent interface properties are
obtained on such structures.  Since the interface is formed during
the plasma oxide process, it can be concluded that the plasma oxide
by itself produces a high quality interface.

      The breakdown characteristics and defect density can be
measured directly on thin plasma oxide MOS structures, since
annealing is not required for these measurements.  The breakdown
distributions for a thin plasma oxide and a PECVD oxide (2) with no
prior plasma oxide were measured.  The results are summarized in
Table I.  The plasma oxide is clearly superior and has proper...