TECHNOLOGY FOCUS PROCESS STUDY
LASER MEASUREMENTS FOR
TRACE MOISTURE SEMICONDUCTOR WAFER
MANUFACTURE
Tunable Diode Laser Spectroscopy (TDL)
technology is the key to Servomex’s DF-700
moisture analyzer series and its capability
to measure trace moisture in pure gases.
Our TDL moisture sensing is a spectroscopic
technique that uses a diode laser as its
light source. It uses a robust and simple
optical design, with both the sample and
reference measured with a single laser
source and a single detector.
TDL sensing offers clear advantages over
other measurement techniques, as the
moisture sample comes only into contact
with a few optical components made
from very robust materials.
The technique works according to the
fundamental principle of Beer’s law
(also known as the Beer-Lambert law)
which relates the attenuation of light to
the properties of the material through
which that light is travelling. Because of
this, the moisture reading is stable over
time, and is able to operate in non-ideal
environments for many years without
requiring calibration. Servomex’s DF-700
moisture analyzers use an advanced TDL
spectroscopy technique, which utilizes
additional information buried within the
shape of the water IR absorption line.
After correction for absolute pressure,
this is subtly dependent on the chemical
composition of the (host) gas or gas matrix
under investigation, providing additional
data for increased measurement stability
and sensitivity.
In spectroscopy, a longer path length is
often used to achieve more measurement
sensitivity. In order to make a sensitive
laser measurement, Servomex employs
a robust Herriott Cell to reflect the laser
back and forth numerous times, using
mirrors inside the measuring cell. By
making multiple passes, this increases the
laser path length, allowing the analyzer
to achieve extremely high sensitivity. The wafer manufacturing process requires
the use of ultra-pure gases, as the smallest
of impurities can result in major defects in
a wafer, causing costly scrap and waste.
The result is an exceptional performance
capable of measuring down to sub parts-
per-billion levels, allowing analyzers such
as the DF-750 and DF-760E to offer an
industry-leading lower detection limit of
100 parts per trillion. To avoid contamination, semiconductor
customers employ a variety of resources,
including strict gas supplier specifications,
multiple gas purification techniques, real-
time continuous gas purity monitoring
and post-process inspection to ensure
ultra-pure gases are delivered to the
manufacturing process.
In addition, TDL moisture sensing offers
drift-free operation, high accuracy and
low maintenance, all achieved through
self-correcting optics and laser line
locking onto the water peak. The laser
line lock system consists of a sealed
moisture ampoule; a portion of the laser
light is redirected through this, locking the
laser wavelength onto the exact moisture
line of interest and removing the possibility
of significant drift.
Servomex provides a unique, single-supplier
gas analysis solution designed to meet
the requirements of semiconductor wafer
manufacture. This comprehensive suite
of gas analyzers measures every impurity
present in the manufacture process,
improving yield and ensuring product purity.
This unique solution can continuously
monitor all critical process gases prior to
entering the wafer manufacturing process.
This includes oxygen (O 2 ), nitrogen (N 2 ),
hydrogen (H 2 ), helium (He), argon (Ar),
carbon monoxide (CO), carbon dioxide
(CO 2 ) and more. It also enables users
to monitor all major process impurities
including O 2 , moisture (H 2 O), methane
(CH 4 ), non-methane hydrocarbons (NMHC)
and many others at part-per-trillion (ppt)
detection levels. Servomex also offers the
customer a complete turnkey integrated
Continuous Quality Control (CQC) system
designed to meet specific customer
requirements for collecting and trending
gas purity data.
Complete with a Servomex-built software
package to collect and trend real-time
gas analysis data, Servomex is the
only company to offer a full suite of
technologies and CQC systems to meet
every impurity analysis need of the wafer
manufacturing process.
SERVOMEX SOLUTIONS FOR UHP ANALYSIS IN WAFER PRODUCTION
DF-550E/560E Series DF-745 SGMax DF-749/DF-750 Series DF-760E
Oxygen analyzer designed to
monitor ppt-level semiconductor
UHP gas. Trace moisture measurements
of various background gases
in semicon fabs. Trace/ultra-trace moisture
measurements of UHP gases
in semicon fabs. Ultra-trace dual measurement
of moisture and oxygen for
PCB bulk gases.
SERVOPRO
Chroma SERVOPRO
NanoChrome SERVOPRO
MonoExact DF310E
SERVOMEX'S TDL SOLUTION
DF-700 SERIES
fast response
LOW MAINTENANCE COSTS
See our analyzers
across the process
OVERLEAF
Find out more at: servomex.expert/df-700
P12
Versatile trace gas analyzer
platform configurable for a
variety of applications.
Sub-ppb trace measurement
of UHP gases for the
semiconductor industry.
Advanced touchscreen ppm
and % oxygen analyzer for
IG applications.
P13