Browse Prior Art Database

Multiple Bandgap Structures in a Homogeneous System

IP.com Disclosure Number: IPCOM000112415D
Original Publication Date: 1994-May-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Cressler, JD: AUTHOR [+2]

Abstract

The effects of external stress and resulting strain in a semiconductor crystal are relatively well known [1]. Altering the symmetry of the crystal changes the electronic band structure of the crystal leading to electrical properties which can differ significantly from the unstrained crystal. For Si, it has been shown that biaxial compressive strain of 1% reduces the bandgap of the crystal by &app. mV Electrically, this is significant.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 79% of the total text.

Multiple Bandgap Structures in a Homogeneous System

      The effects of external stress and resulting strain in a
semiconductor crystal are relatively well known [1].  Altering the
symmetry of the crystal changes the electronic band structure of the
crystal leading to electrical properties which can differ
significantly from the unstrained crystal.  For Si, it has been shown
that biaxial compressive strain of 1%  reduces the bandgap of the
crystal by &app.  mV Electrically, this is significant.

      Recently, it has been shown that substantial levels of biaxial
strain can be produced in localized regions of a semiconductor wafer
by patterning the surface with appropriate trench patterns, filling
these trenches with, for example, silicon dioxide and thermally
oxidizing the wafer surface at a relatively high temperature [2].
The degree of compressive strain generated at the oxidation
temperature depends on the trench geometry and the oxidation
conditions chosen.  As the wafer cools to room temperature, further
strain can be generated due to the thermal expansion mismatch between
the substrate and the trench-fill material.  With appropriate choice
of the trench-fill material, the thermal strain is additive with the
oxidation-induced strain (SiO&sub2.  filled trenches in a Si
substrate achieve this goal).  The degree of compressive strain
generated during cooling also depends on the trench geometry chosen.
In this manner, strain levels approaching 1% can be a...