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Germanium Concentration Depth Profiles of Silicon-Germanium Alloys Using Rie/Ellipsometry

IP.com Disclosure Number: IPCOM000120840D
Original Publication Date: 1991-Jun-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 58K

Publishing Venue

IBM

Related People

deFresart, E: AUTHOR [+3]

Abstract

In-situ HeNe ellipsometry during reactive ion etching (RIE) of SiGe alloys has been used to obtain the Ge concentration of the alloy as a function of depth. This method requires the following inputs and procedures: (1) The complex refractive index at 632.8 nm of the SiGe alloy needs to be known with high accuracy as a function of Ge content. In this work the complex refractive index of thick SiGe films with varying Ge concentrations was determined using ellipsometry. The Ge concentration was obtained by Rutherford backscattering. (2) The ellipsometric variables Psi and Delta are measured as a function of time during reactive ion etching of the SiGe alloy. A low power CF4 plasma is used to etch the SiGe alloys. The etch rate depends on the RF power and can be chosen based on the desired depth resolution.

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Germanium Concentration Depth Profiles of Silicon-Germanium Alloys
Using Rie/Ellipsometry

      In-situ HeNe ellipsometry during reactive ion etching
(RIE) of SiGe alloys has been used to obtain the Ge concentration of
the alloy as a function of depth. This method requires the following
inputs and procedures:
(1)  The complex refractive index at 632.8 nm of the SiGe alloy needs
to be known with high accuracy as a function of Ge content.  In this
work the complex refractive index of thick SiGe films with varying Ge
concentrations was determined using ellipsometry. The Ge
concentration was obtained by Rutherford backscattering.
(2)  The ellipsometric variables Psi and Delta are measured as a
function of time during reactive ion etching of the SiGe alloy.  A
low power CF4 plasma is used to etch the SiGe alloys.  The etch rate
depends on the RF power and can be chosen based on the desired depth
resolution.
(3)  The Psi, Delta, Time data are converted point-by-point starting
from the sample surface into a refractive index versus sample depth
plot. The known relationship between the real and imaginary part of
the refractive index of the SiGe alloy is used for this numerical
procedure.
(4)  The refractive index - sample depth data are converted into Ge
concentration - sample depth plots using the relationship between the
SiGe alloy refractive index and the Ge concentration.

      Using the above, the depth profile of the Ge concentration in
an unknown epitaxial SiG...