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QTAT Method of Measuring Low-Temperature Silicon Epitaxial Films

IP.com Disclosure Number: IPCOM000102694D
Original Publication Date: 1990-Dec-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 4 page(s) / 124K

Publishing Venue

IBM

Related People

Chu, JO: AUTHOR [+5]

Abstract

The present trend in semiconductor technology for high performance devices relies heavily on the application of a novel low-temperature epitaxial (LTE) process (*) to fabricate, for example, "submicron" epitaxial silicon films for the base materials. Consequently, for the development of such a crucial low-temperature CVD process for manufacturing operation it is very important to have a scheme for a quick and accurate film thickness measurement on a routine monitor basis for the typical "submicron" epitaxial films as deposited by such an UHV/CVD LTE tool. Presently, conventional infrared-reflectance techniques are used to measure (high temperature) epitaxial silicon film thicknesses, but this method will measure film thicknesses only down to 1 micron and, hence, is inadequate for submicron LTE film measurements.

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QTAT Method of Measuring Low-Temperature Silicon Epitaxial Films

       The present trend in semiconductor technology for high
performance devices relies heavily on the application of a novel
low-temperature epitaxial (LTE) process (*) to fabricate, for
example, "submicron" epitaxial silicon films for the base materials.
Consequently, for the development of such a crucial low-temperature
CVD process for manufacturing operation it is very important to have
a scheme for a quick and accurate film thickness measurement on a
routine monitor basis for the typical "submicron" epitaxial films as
deposited by such an UHV/CVD LTE tool. Presently, conventional
infrared-reflectance techniques are used to measure (high
temperature) epitaxial silicon film thicknesses, but this method will
measure film thicknesses only down to 1 micron and, hence, is
inadequate for submicron LTE film measurements.  In contrast SIMS
analysis is an excellent technique for measuring LTE films, but it is
a very slow and time-consuming procedure for doing a single-point
measurement on a wafer.  An approach for overcoming these problems is
to use polysilicon monitors in the UHV/CVD LTE batch tool and instead
directly measure the corresponding deposition of polysilicon film on
the polysilicon monitor as an equivalent Quick Turn-Around Time
(QTAT) measurement for the LTE film.  Since no growth selectivity or
incubation delays are expected between epi- and poly- film deposition
on single crystalline and polysilicon substrates, respectively, this
is a valid and equivalent film thickness measurement for the
as-deposited LTE film.  Moreover, by measuring the polysilicon
monitor at exactly the same point before and after deposition, no
(further) systematic error will be introduced in the thickness
measurement and the final resolution will be limited only by the
measurement tool for the polysilicon film.  To attest this QTAT
method a direct comparison of the SIMS measurement is made to the
QTAT difference thickness measurement of the as-deposited
corresponding polysilicon film on the control monitors from the same
batch of processed wafers.  The results are summarized in the Table.
SIMS analysis in Fig. 1 shows that the as-deposited polysilicon film
is 1013-Angstroms thick which is essentially identical to the film
thickness of 1039 Angstroms for...