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Browse Prior Art Database

Silicon Based Dielectric Material with Extremely Low Dielectric Constant

IP.com Disclosure Number: IPCOM000103695D
Original Publication Date: 1993-Jan-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 2 page(s) / 74K

Publishing Venue

IBM

Related People

Collins, R: AUTHOR [+2]

Abstract

This article describes a method for making a silicon-based dielectric material with an extremely low capacitance. Typical films currently used for dielectrics include silicon dioxide and silicon nitride. These films are usually limited to relative dielectric constants above about 3. In this article, the low dielectric constant is achieved by using porous silicon, which can be made to have an extremely large void fraction. Thus, the majority of the film is void space, and that fraction would have a dielectric constant of 1. By changing the void space, the dielectric constant can be continuously varied.

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Silicon Based Dielectric Material with Extremely Low Dielectric Constant

       This article describes a method for making a
silicon-based dielectric material with an extremely low capacitance.
Typical films currently used for dielectrics include silicon dioxide
and silicon nitride.  These films are usually limited to relative
dielectric constants above about 3.  In this article, the low
dielectric constant is achieved by using porous silicon, which can be
made to have an extremely large void fraction.  Thus, the majority of
the film is void space, and that fraction would have a dielectric
constant of 1.  By changing the void space, the dielectric constant
can be continuously varied.

      Porous silicon can be produced by electrochemical etching and
the porosity can be varied from N 20-70 percent (G. Bomchil, A.
Halimaoui and R. Herino, Appl. Surf. Sci, 41-42, 604 (1989)).  The
remaining material has very small dimensions and will be depleted for
moderate doping densities, thus acting as an insulator.  It can also
be oxidized (K. Imai and S. Nakajima, IEDM 376 (1981)) and converted
to silicon dioxide.  The dielectric constant of the resulting
material can be estimated by accounting for the volume fraction of
material (either silicon or silicon dioxide, with relative dielectric
constants of 11.9 and 3.9) and void space.  Thus, porous silicon with
a 50 percent porosity which has been fully oxidized would have a
dielectric constant of roughly 2.

      This invention is quite simple to implement with conventional
integrated circuit fabrication techniques and a simple
electrochemical etch step.  The meta...