Browse Prior Art Database

High Resolution Depth Profiling of Thin Oxide Nitride Oxide (ONO) Structures

IP.com Disclosure Number: IPCOM000121425D
Original Publication Date: 1991-Aug-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 1 page(s) / 39K

Publishing Venue

IBM

Related People

Cohen, SA: AUTHOR [+4]

Abstract

Compositional depth profiles of thin (Z5nm) oxide/nitride/oxide (ONO) structures are important in ONO process development/manufacturing, but are beyond the capabilities of Auger and secondary ion mass spectrometry profiling. Ellipsometry in conjunction with plasma etching has been shown in our work to be capable of providing high-resolution ONO depth profiles with fast turn- around time.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

High Resolution Depth Profiling of Thin Oxide Nitride Oxide (ONO)
Structures

      Compositional depth profiles of thin (Z5nm) oxide/nitride/oxide
(ONO) structures are important in ONO process
development/manufacturing, but are beyond the capabilities of Auger
and secondary ion mass spectrometry profiling.  Ellipsometry in
conjunction with plasma etching has been shown in our work to be
capable of providing high-resolution ONO depth profiles with fast
turn- around time.

      An automatic He/Ne ellipsometer using an angle of incidence of
74~ with respect to the surface normal was used.  A CF4 plasma of 30
W 13.56 MHz power at 25 mTorr pressure was employed to slowly etch
the ONO layer. Ellipsometry data may be acquired simultaneously from
which remaining ONO thickness versus etch time plots can be obtained.
These data are used to construct etch rate versus thickness plots.
For our plasma conditions the Si3N4 etch rate is about 2x that of
SiO2 .  For ONO films of a thickness of Z5.5nm and less we can
clearly see the nitride layer in the first 2-3 nm from the surface,
followed by Z3 nm of SiO2 .  For different deposition conditions we
have used this approach to establish differences in the thicknesses
of the individual dielectric layers.

      Alternatively one may determine the refractive index of the
infinitesimal layer removed by etching and construct a refractive
index versus thickness plot.

      Disclosed anonymously.