STABLE AND COST-EFFECTIVE
MEASUREMENT OF UHP GASES
There are some limitations to using PED technology. The
sensitivity of the measurement means it is suitable only for trace
analysis applications (<1000 parts per million). Due to the nature
of the plasma, the sensor also exhibits some occasional mild
cross-interferences due to the sample matrix, which requires
more demanding chromatographic methods – also sometimes
the case with FID technology. Overall, however, the PED sensor
revolutionizes the analysis of hydrocarbons, CO and CO 2 ,
improving measurement sensitivity, successfully addressing
the safety concerns associated with the use of hydrogen and
reducing the cost of ownership.
Right: a chromatogram obtained with a PED sensor at 5ppb for
CH 4 , CO 2 and NMHC. This chromatogram shows clear sensitivity
to hydrocarbons, as well as sensitivity to CO 2 achieved without
the use of a methanizer. While a methanizer is always required
to measure CO and CO 2 with a FID sensor, it is not required by
the PED – improving measurement reliability, avoiding catalyst
poisoning risks associated with methanizers and creating a
further reduction in cost of ownership.
Thermal Conductivity (TCD) and Flame
Ionization Detector (FID) sensors are long-
established and are the most widely used
measurement technologies. However, a more
recent technological development has
surpassed their performance, especially when
ultra-trace level measurement is required.
However, this sensor type uses a flame
to burn hydrocarbons, which requires air
and hydrocarbon-free hydrogen fuel gas.
Increasingly stringent health and safety
requirements means concerns over using
flammable pure hydrogen have been
raised by users.
Challenged to find a safer alternative
to the FID, Servomex’s R&D team
undertook extensive research on
Servomex’s existing Plasma Emission
Detector (PED) technology, aiming to
improve the technology’s sensitivity
and identify a configuration specific to
hydrocarbons, while avoiding the use of
explosive gases.
Their intensive research led to the
development of a PED sensor optimized
for the trace-level analysis of hydrocarbons.
ADVANTAGES OF PLASMA EMISSION DETECTOR TECHNOLOGY
The new Servomex PED sensor offers
many advantages over FID technology.
It is very sensitive and selective to any
molecules containing carbons (organic
or inorganic), being up to 100 times
more sensitive than a FID measurement,
depending on the carrier gas.
FID sensors are traditionally renowned
for sensitivity, with the best FID sensors
offering a detection limit between
10 parts per billion (ppb) and 20ppb
methane equivalent. This limitation is
due to the FID sensor requiring carrier
gas, fuel and air to operate, making the
sensor more prone to noise from low-
level hydrocarbon contamination from
those three potential sources. However, the Pure Gas (P-Gas), used inside
the fab after the purifier stage, has much
lower LDL requirements of 1ppb or less.
Any hydrocarbons contained in any of
these gases are ionized by the sensor,
causing drift and noise which limits
reliable performance for ultra-trace
level measurements. As the PED sensor requires only a carrier
gas, external contamination from air
and fuel is removed. While it is still very
important to have a clean carrier gas,
techniques exist to obtain a clean helium
or argon carrier gas with a total impurity
level below 1ppb. In addition, avoiding
the use of hydrogen and air reduces cost
of ownership, as less gas is consumed and
fewer purification systems are required.
This level of detection is usually acceptable
for General Gas (G-Gas) made before
the main purifier, which requires a lower
detection limit (LDL) of about 10ppb.
(Fig.1) shows
PED sensor a
This chromat
to hydrocarb
achieved with
which conver
methaniser is
and CO 2 with
(Fig.2) shows
the PED - imp
Servomex Na
avoiding cata
level, again sh
with methan
with this new
reduction in
of detection
is below 1 pp
EXPERT PAPER
NanoChrome:CH 4 , CO 2 and NMHC at 5ppb with new PED
Fig.1 – PED sensitivity to CH 4 , CO 2 and NMHC with NanoChrome
A step response using a SERVOPRO NanoChrome analyzer at
ppb level, again showing the sensitivity achieved with this
sensor. The achievable limit of detection for CO, CO 2 , CH 4 and
NMHC is below 1ppb. A
chromatogram
obtained
for speciated hydrocarbons
Fig.2
– New PED sensitivity
step change
analysis, showing the PED sensor’s clear sensitivity to the
different hydrocarbons.
Fig.2 – New PED sensitivity step change
a clean carrier
a clean helium
total impurity
avoiding the u
ownership co
less purificatio
PED SENSITIVITY TO CH 4 , CO 2 AND
NMHC WITH NanoChrome
NEW PED RESPONSE TO HYDROCARBONS
NanoChrome CH 4 step change
FID technology is commonly used for
hydrocarbons analysis, being relatively
simple to use and offering a very sensitive,
selective and linear measurement.
The new Servomex PED sensor offers many
advantages over FID technology. The new
PED sensor is very sensitive and selective to
any molecules containing carbons (organic or
inorganic), being up to 10 to 100 times more
sensitive than a FID measurement, depending
on the carrier gas.
NEW PED SENSITIVITY STEP CHANGE
EXPERT PAPER
In the field of gas chromatography,
many sensors are available that cover
a broad range of measurements. Each
sensor has advantages and drawbacks,
so a solid understanding of the different
technologies is important.
analysis. This sensor is relatively simple
to use, offering a very sensitive, selective
and linear measurement, but there are
operational disadvantages. As the name
implies, this sensor type uses a flame to
burn hydrocarbons, which requires air and
hydrocarbon-free hydrogen fuel gas to burn.
In recent years, more stringent health and
S E RVO M E X .CO M
A MEASUR
(Fig.3) shows
speciated hyd
the PED sens
different hyd
(Fig.2) shows a step response using a
Hydrocarbon
analysis with new PED detector
Servomex NanoChrome analyser
at ppb
level, again showing the sensitivity achieved
with this new sensor. The achievable limit
of detection for CO, CO 2 , CH 4 and NMHC
is below 1 ppb.
Fig.3 – New PED response to hydrocarbons
THE SERVOPRO NanoChrome
The PED sensor is at the heart of the
SERVOPRO NanoChrome analyzer,
designed to measure ultra-trace levels of
impurities in electronic gases.
Offering the most stable P-Gas analysis on
the market, even at the lowest levels, the
NanoChrome delivers a superb sub-ppb
measurement of the contaminant gases and
hydrocarbons that can be present at ultra-
trace levels in semiconductor manufacture.
It also provides an industry-leading LDL
of 0.5ppb for impurities in an oxygen
background – this includes measurements
for CO, CO 2 , CH 4 and NMHC.
Fig.3 – analytical
New PED response
to hydrocarbons
This
sensitivity
and ultra-
stable reliability is enhanced by
(Fig.3) shows chromatogram obtained for
speciated hydrocarbons analysis, showing
the PED sensor’s clear sensitivity to the
different hydrocarbons.
S E RVO M E X .CO M
advanced signal recovery, utilizing
specially developed adaptive
chromatographic filtering methods and
ProPeak peak detection techniques for a
sensitive, selective measurement.
Using a Direct Analysis Methodology, the
NanoChrome removes the doubt associated
with FID and RGD measurements.
A MEASUR
Alongside the DF-500 ultra-trace range
and DF-700 moisture analyzer range,
the NanoChrome ensures Servomex
provides the semiconductor industry with
a complete, single-supplier solution for
reliable UHP gas analysis.
Download the NanoChrome brochure today: servomex.com/downloads
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S E RVO M E X .CO M
A MEASURABLE ADVANTAGE