LIGHTHOUSE Gas Sampling in Semiconductor and Pharmaceutical Cleanrooms User Manual
- June 27, 2024
- LIGHTHOUSE
Table of Contents
Gas Sampling in Semiconductor and Pharmaceutical Cleanrooms
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Specifications
-
Product Name: Sterility Verification Gas Sampler
-
Application: Gas Sampling in Semiconductor and Pharmaceutical
Cleanrooms -
Usage: Verifying Sterility
Product Information
Contamination Free Manufacturing (CFM) of Integrated Circuits
(ICs) and Sterile injectable pharmaceutical products involves
particle control and removal. Cleanrooms are defined by particle
concentrations in the air, and efforts are made to minimize
particles in processing equipment and medicines.
Micro Contamination in Pharmaceutical Cleanrooms
Contaminants on a Si wafer’s surface can be ionic materials,
elemental particles, molecular compounds, or airborne dust acquired
during manufacturing processes.
Different Types of Wafer Contamination:
-
Ionic Materials: Composed of cations and
anions like chlorine, sodium, and fluorine. -
Elemental Particles: Made from metals like
copper, dust, metal debris, fibers, and Si particles. -
Molecular Compounds: Films or particles from
organic vapors like greases, solvent residues, etc. -
Airborne Dust: Contaminants from airborne dust
during processing.
Sources of Semiconductor Cleanroom Contamination
Sources include foreign materials, parasitic reactions, ionic
contaminants, air molecule contaminants, organic particles,
elements like alkaline metals, transition metals, dopants, acids,
bases, and organic compounds.
Gases in the Semiconductor Industry
Compressed gases like Ammonia and Silane are essential for
processes such as chemical vapor deposition (CVD) in the
semiconductor industry.
Product Usage Instructions
-
Ensure the Gas Sampler is properly assembled and connected to
the sampling system. -
Select the appropriate sampling location within the cleanroom
or semiconductor facility. -
Follow the specific procedure for gas sampling as outlined in
the user manual provided with the product. -
Analyze the collected gas sample using appropriate techniques
to verify sterility or contamination levels. -
Repeat the sampling process periodically to ensure ongoing
sterility verification.
Frequently Asked Questions (FAQ)
Q: How often should gas sampling be performed?
A: Gas sampling should be performed regularly as per the
facility’s standard operating procedures. It is recommended to
conduct sampling during critical production phases and whenever
contamination is suspected.
Q: Can the Gas Sampler be used for sampling other gases?
A: The Gas Sampler is designed specifically for sterility
verification in cleanrooms and semiconductor facilities. It is not
recommended for sampling other gases outside its intended use.
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Verifying Sterility
Gas Sampling in Semiconductor and Pharmaceutical Cleanrooms
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Overview
Contamination Free Manufacturing (CFM) of Integrated Circuits (ICs) and
Sterile injectable pharmaceutical products has historically involved particle
control and removal.
Although yield-destroying and batch destroying defects are often traced to
process non-uniformities, a majority of the effort to control contamination in
IC & Pharma facilities has focused on particle control.
Cleanrooms are defined by the particle concentrations in the air and designers of processing equipment strive to minimize the number of particles-per-wafer processed through the equipment or particulates found in injectable medicines.
Micro Contamination in Pharmaceutical Cleanrooms
When a medication is contaminated with microorganisms like bacteria or fungus,
the consequences can range from harmless to fatal. For nonsterile drugs taken
orally, the effects may be less likely to be dire, as our gastrointestinal
tracts provide a highly acidic, unhospitable environment that can kill most
microorganisms. However, medications that are administered intravenously or in
the form of eye drops, must be completely sterile. Any contaminant can find
its way directly into the bloodstream, causing sepsis or even death.
Therefore, the monitoring of particles in these pharmaceutical sterile
manufacturing environments is critical to ensure patient safety and product
efficacy and quality.
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What are Different Types of Wafer Contamination?
Contaminants on a Si wafer’s surface are just absorbed ions, elements,
particles, and gases, which were acquired during the entire wafer
manufacturing process. Surface contaminants can be classified into four types:
Ionic Materials
Ionic materials are composed of cations and ion that can be physically
adsorbed or chemically bonded from inorganic compounds.
Examples are chlorine, sodium, and fluorine.
Elemental Particles
Also called atomic particles, these are made from metals such as copper and
other heavy metals that can be electrochemically plated out on the surface of
the semiconductor. They may also consist of dust, metal debris, fibers, and Si
particles.
Molecular Compounds
Molecular compounds are films or particles of condensed
organic vapors from greases, solvent residues, photoresists, fingerprints,
metal oxides, hydroxides,
lubricants, and other organic compounds.
Airborne Dust
Contaminants can spawn from airborne dust during processing. It can be
acquired from equipment, factory operators, wafer handling, chemical
processing, film deposition, and gas piping. Moving equipment and containers
for liquids are the number one carrier of particles and contaminants that can
transfer on a Si wafer. On the other hand, solid materials, ambient air,
gases, liquids, and chemicals don’t accumulate as many particles, so they
cause less particle contamination.
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Sources of Semiconductor Cleanroom Contamination
Foreign Materials:
· Fluid Impurities: Chemicals, Gas.
· Tools’ Impurities: Corrosion, Out-Gassing, and Handling.
· Particles: Suspensions within Fluids, Abrasion, Environment, Operators.
Parasitic Reactions
· Between Reactive Materials.
· Corrosion, Out-Gassing, Dissolution of Tool Parts.
Contamination Classification Ionic Contaminant Ionic Contaminant Ionic
Contaminant Ionic Contaminant and Air Molecule Contaminant
Ionic Contaminant and Air Molecule Contaminant
Organics Particles
Particles
Elements
Alkaline Na, K
Transition Metals: Ni,Co,Fe,…
Dopants: Al, P, In, Ga, As, B,…
Acids: F-, Cl-, CH3COO-, Br-, PO4–, SO4–
Bases: NH3 Amines
Organics
Organics
Inorganic
Sources
· Human Pollution · Works · Chemical and Gases
· Human Pollution · Works · Chemical and Gases · Networks-tools-processes
· Process: Wet Processes, Implantation/Works
· Material Out-Gassing · Chemical and Gases
· Process pollution: Etch, Wet Process
· Chemical Vapor Deposition (CVD) · Works · Material Out-Gassing · Traffic
Pollution · Industrial Poluution
· Process pollution: Etch, Wet Processes
· CVD Deposition · Works · Material Out-Gassing · Traffic Pollution ·
Industrial Pollution
· Process Pollution: Wet process and Lithography process
· Process Pollution: Dry Etch Polymers, Resist Strip, Wet Process
· Material Out-Gassing · Chemicals and Gasses
· Process Pollution: Dry Etch Polymers, Resist Strip, Wet Process
· Material Out-Gassing · Chemical and Gases
Wafer Effects
· Electrical Instability Gate Oxide Leakage Retention
· Gate Oxide Integrity (GOI) degradation
· Shift of voltage threshold in the transistor device
· Pad Corrosion · Aluminum Corrosion · Defectivity on Deep UV (DUV) and
Mid UV (MUV) Resist · Salt Deposition on Lens,
Masks, and Wafers
· Footing on DUV Resist · Salt Deposition on Lens,
Masks, and Wafers · Photolithography activation,
especially with 193nm process
· Photolithography activation, especially with 193nm process
Eg: Contamination with solvent on resist
· Gate Oxide Integrity · High Resistivity Contact · Deposition on Surface ·
Lens Degradation · Defectivity with Opens or Shorts
on Pattern Wafers
· Gate Oxide Integrity · High Resistivity Contact · Deposition on Surface ·
Lens Degradation · Defectivity with Opens or Shorts
on Pattern Wafers
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Image courtesy of asml.com
Gases in the Semiconductor Industry
In the semiconductor industry, compressed gases are essential for a wide range
of processes from the fabrication of microchips to cleaning and maintenance:
Ammonia and Silane: Used in chemical vapor deposition (CVD) to produce silicon
nitride and silicon films, respectively.
Argon: Used in sputtering processes to deposit thin films and in plasma
etching and cleaning.
Chlorine and Boron Trichloride: Used in etching processes to create
microelectronic circuits on semiconductors.
Clean Dry Air (CDA): Used for tools and machinery that require clean,
moisture-free air.
Helium: Employed for cooling in various equipment and as a carrier gas for
thin film deposition.
Hydrogen: Used as a reducing agent in various processes, including atmospheric
annealing and epitaxial layer deposition
Nitrogen: The most widely used gas for purging and inerting, as well as for
providing a clean, dry atmosphere for process and storage operations to
prevent oxidation.
Oxygen: Utilized in oxidation processes to grow silicon oxide layers on
wafers.
Sulfur Hexafluoride (SF6): Commonly used as an insulating gas in electrical
equipment as well as plasma etching.
Bulk gases are a significant portion of supply spend for semiconductor and
display fabs. Effective
supply often requires on-site production, storage, and distribution. These
facilities are built concurrently with the fab, and the first qualified gas
deliveries are made as soon as the fab shell is complete.
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Gases in the Pharmaceutical Industry
In recent years, we have seen an increase in regulations centered around
comprehensive contamination control plans. For example, the GMP Annex 1 2022
update revolves around building your cleanroom according to a riskbased
contamination control plan that considers higher testing standards and levels.
To stay in compliance with these ever stringent and increasing regulations, it
is important to consider every factor of your contamination control plan,
including monitoring compressed gases.
Compressed gases play several critical roles in the pharmaceutical industry,
ranging from production processes to packaging and quality control:
Argon: Used as a protective atmosphere for the storage and packaging of
pharmaceuticals to prevent oxidation.
Carbon Dioxide: Utilized in supercritical CO2 extraction processes for
pharmaceuticals, which is an efficient method for extracting active
ingredients. It’s also used in pH control of water used in pharmaceuticals.
Clean Dry Air (CDA): Used in pneumatic systems and for instrumentation that
requires clean, moisture-free air.
Ethylene Oxide: Used for sterilizing medical products and devices.
Helium: Sometimes used for leak detection in packaging because of its small
molecular size and inert properties.
Hydrogen: Employed in hydrogenation processes, which are crucial for the
manufacture of many drugs.
Nitrogen: Used extensively for inerting and blanketing to protect oxygen-
sensitive materials from degradation or combustion. It’s also used in
freezedrying (lyophilization) processes to remove moisture from pharmaceutical
products.
Oxygen: Employed in fermentation processes for aerobic bacteria and in various
biosynthesis processes.
All compressed gases are one of three major categories: Liquefied, Non-
Liquefied, and Dissolved Gases. Liquefied gases are gases which can become
liquids when under pressure in th cylinder. Propane, nitrous oxide and carbon
dioxide are examples of liquefied gases.
Compressed air is used abundantly in pharmaceutical and electronics
cleanrooms. Some uses of compressed gases include: de-dusting, spray-coating
tablets, over-pressurizing mixing and holding tanks, driving liquids through
fill lines and filters, and operating control valves.
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There are several ways in which particle contaminants can get into compressed gases:
Compressor Wear: Particles can be generated from the mechanical wear and tear
of compressor components. Metal flakes or rubber from seals and gaskets can
contaminate the gas as it is compressed.
Desiccant Dust: Desiccant used in drying the compressed gas can break down,
leading to desiccant dust particles being carried along with the gas flow.
Handling and Transportation: Handling and transporting gas cylinders can stir
up particles that may have settled or introduce new contaminants from the
environment where the cylinders are stored and moved.
Improper Filtration: Inadequate filtration within the gas delivery system, or
failure to properly maintain filters, can allow particles to pass through.
Filters may also shed fibers or particles themselves.
Installation and Maintenance Activities: Particles can be introduced during
installation or maintenance of the gas delivery system. This includes dust and
debris from new piping or from maintenance tools and processes.
Intake Contamination: Particles from the ambient air can enter the gas during
the initial intake process if the intake filters are inadequate or have become
degraded over time.
Residual Particles from Manufacturing: Residual particles from the
manufacturing process of the gas cylinders or the gas itself might not be
completely removed and can contaminate the gas.
System Corrosion: Internal corrosion of the compression system and the piping
can release particles into the gas stream. Moisture in the system can
accelerate this corrosion, increasing the risk of contamination.
What Gas Standards are used or followed?
ISPE Good Practice Guide provides the following chart as a helpful
recommendation of sampling using cleanroom specifications for compressed air
plans per contaminant:
Test
Frequency / Location
Nonviable Particles Tested every 3 months on a rotating basis for sampling locations following the central systen’s final filter at predetermined locations on the horizontal piping run for each floor.
Viable Particles
Tested every 3 months on a rotating basis for sampling locations following the central system final filter and at predetermined locations on the horizontal piping run for each floor.
Dew Point (moisture) Monitoring continuously using in-line dew point instrumentation following compressed air dryer.
Hydrocarbon (oils)
Annual sampling and testing following the coalescing filter to verify the hydrocarbon content of the compressed air system.
The International Society for Pharmaceutical Engineers (ISPE) Good Practice
Guide, recommends, “in cases where the gas is entering a classified area, it
is required to at least meet the room classification
limits established for the cleanroom environment” (2016).
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ISO Standards:
ISO 8573: This series covers the purity classes and contamination levels for
particles, water, and oil in compressed air. It specifies methods for
measuring contaminants and is widely used as a reference for air quality
across various industries.
ISO 7396: This standard covers medical gas pipeline systems, including
requirements for the supply systems for compressed medicinal gases.
ISO 12500: This series complements ISO 8573 by providing detailed methods for
testing air treatment equipment used in compressed air systems, including
filters and dryers. It helps in assessing the performance of equipment
intended to remove contaminants such as oil aerosols, vapors, and
particulates.
ASTM Standards:
ASTM G93: Standard for cleaning and testing materials used in oxygen-enriched
environments, which includes guidelines for handling gases to prevent
contamination.
ASTM D1945: Standard test method for analyzing natural gas by gas
chromatography, which can be adapted for other compressed gases to determine
their composition.
ASTM D2986: Standard practice for the evaluation of air-assay media by the
monodisperse DOP (dioctyl phthalate) smoke test, useful in assessing filter
performance in gas handling systems.
Compressed Gas Association (CGA) Standards:
CGA G-4.1: Pertaining to cleaning equipment for oxygen service, outlining
methods for ensuring that compressed oxygen and other gases do not become
contaminated.
CGA G-7: A guidebook on the proper use and handling of compressed gases,
providing broad guidelines on storage, handling, and procedures for
maintaining gas purity.
European Pharmacopoeia (Ph. Eur.) and United States Pharmacopeia (USP):
These pharmacopeias include standards and specifications for medical gases,
detailing purity requirements, testing methods, and handling procedures to
ensure safety and efficacy in pharmaceutical applications.
US FDA Guidance for Industry
Sterile Drug Products Produced by Aseptic Processing Current Good
Manufacturing Practice recommends that “compressed gas should be of
appropriate purity… and it’s microbiological and particle quality after
filtration should be equal to or better than that of the air in the
environment into which the gas is introduced.”
SEMI Standards:
Specifically for the semiconductor industry, the SEMI standards cover
everything from gas chemical purity to material compatibility and handling
practices, ensuring that the gases do not introduce contaminants that could
affect semiconductor manufacturing processes. In the semiconductor industry,
the gases used in the manufacturing process are graded primarily based on
their purity levels, as even minute impurities can significantly impact the
quality and performance of semiconductor devices. The grading of semiconductor
gases is typically divided into several categories:
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Electronic Grade: This is the most common grade used in semiconductor
manufacturing. Electronic grade gases are highly pure, typically 99.999% pure
or better, often referred to as “Five Nines” purity. The specification might
extend to even higher purity levels like 99.9999% (“Six Nines”) depending on
the requirements of specific applications.
Ultra-High Purity (UHP): UHP gases are a step above the standard electronic
grade, required for processes where even trace amounts of contaminants could
be detrimental. These gases are usually 99.9999% pure or better. UHP gases are
critical for manufacturing processes like oxidation, deposition, and various
etching processes, where absolute control over contaminants is necessary.
The grading of gases is supported by rigorous testing and certification
processes, which include:
Particulate Count: Ensuring that the gas contains minimal solid particles, as
these can clog or contaminate semiconductor tools.
Moisture Levels: Moisture is often a critical contaminant in semiconductor
processes and must be controlled to extremely low levels.
Research Grade: Research grade gases are used primarily in R&D environments
where experimental processes are conducted. These gases might have specific
tailored compositions and are characterized by high purity levels similar to
or sometimes exceeding those of UHP gases.
Instrument Grade: Used primarily for calibration and instrumentation
applications within the manufacturing process, instrument grade gases are
highly reliable for ensuring the accuracy and performance of analytical
equipment. They have stringent requirements for both purity and consistency.
“Particulate Contamination in gases is related to a sample colume of 1cubic
foot based on allowable limits at a particular size.
For example, 10/0.01 N2 mean 20 10 particles of size @0.1um for Nitrogen
pipline gas (SEMI C6.6)
Spec Gas (Specification Gas): Spec gases are defined by their specific
compositions to meet the exact requirements of particular processes. They
often have defined levels of certain dopants
or contaminants that are precisely controlled
to achieve the desired characteristics in a
semiconductor device.
”
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ISO 8573
This is the primary and most widely recognized international standard for
compressed air quality. It specifies the amounts of contamination allowed in
terms of particles, water, and oil in compressed air systems, and outlines
methods for measuring these contaminants. ISO 8573 is divided into several
parts, each focusing on different types of contaminants. This standard is
often used as a benchmark for compressed gases in various applications, not
just compressed air. ISO 8573 is made up of 9 parts:
ISO 8573-1: (2010) Quality Classes: This part is the cornerstone of the
standard, defining the quality classes of compressed air with respect to
particles, water, and oil. Each class specifies the concentration limits for
these contaminants. For instance, the classes for particulates determine the
number of particles per cubic meter and are classified by their size. Similar
classes exist for humidity (water content) and oil (both aerosol and vapor
forms).
ISO 8573-2: (2018) Test Methods for Oil Aerosol Content: Provides the
methodologies for quantifying the amount of oil aerosol present in the
compressed air.
ISO 8573-3: (1999) Test Methods for Humidity: Outlines the methods for
measuring the moisture content of compressed air, which is critical for
applications where moisture can impact product quality or process efficiency.
ISO 8573-4: (2019) Test Methods for Solid Particles: Describes the techniques
used to determine the concentration and size distribution of solid particles
in compressed air, essential for preventing contamination in sensitive
manufacturing processes.
ISO 8573-6: (2003) Test Methods for Gaseous Contaminants: Provides guidelines
for identifying and measuring gaseous contaminants in compressed air,
including but not limited to CO, CO2, SO2, NOx, and hydrocarbons.
ISO 8573-7: (2003) Test Method for Viable Microbiological Contaminant Content:
Details the procedures for assessing the presence of viable microbiological
organisms in compressed air, an important consideration for industries like
pharmaceuticals and food processing where sterility is paramount.
ISO 8573-8: (2004) Test Methods for Solid Particle Content by Particle
Counting Using Optical Particle Counter: Expands on part 4 by introducing an
optical particle counting method for more precise measurement of particle
contamination.
ISO 8573-9: (2004) Test Methods for Liquid Water Content: Outlines methods to
measure liquid water content in compressed air, which can be critical in
avoiding corrosion and ensuring the integrity of pneumatic systems.
ISO 8573-5: (2001)
Test Methods for Oil Vapor and Organic Solvent Content: Specifies procedures
for measuring the amount of oil vapor and organic solvents, which are crucial
for applications requiring highly pure air, such as in pharmaceutical and food
production.
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Monitoring the particle count within compressed gases
ISO 8573 Part 4:
1. Provides a sampling method for compressed air.
2. A guide for choosing suitable measuring equipment to determine its
particle size and concentration by number.
3. Establishes a minimum sampling volume of 1000L (1m³).
4. Use of Optical Particle Counter for testing sizes from 0.1 to 10µm.For
non-viable particles a Particle Counter is used with a High Pressure Diffuser
(HPD) placed inline between the gas line and the particle counter sample
inlet. The HPD diffuses the high pressure gas so the flow rate of the sample
is equalized. It is critical that the flow rate is maintained correctly.
To sample compressed gas, a particle counter will need an accessory called a High Pressure Diffuser (HPD). The HPD connects the particle counter and the compressed gas line and diffuses the gas as is enters the particle counter sample inlet. If the high-pressured gas enters the particle counter sample inlet without the HPD, the sensor inside the particle counter can be damaged and the results of the testing will not be accurate.
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High Pressure Diffusers:
HPD is required to reduce the pressure of the gas to be sampled to ambient
such that the gas may be sampled at the instrument’s standard flow rate while
at the same time not introducing particulate contamination to the gas sample.
In addition to the required pressure reduction, the HPD maintains isokinetic
flow through to the device output to ensure that the size-distribution of any
particles suspended in the gas is correct and uniform. This Particle Counter
system above is suitable for monitoring gases in the Pharmaceutical Industry.
When testing dangerous gases it is important to ensure the gas is ported and
exhausted away from the test environment and the operator safely. HPDs come in
two forms
1. Ported for safe ventilation
2. Vented for use with atmospheric gases such as, Nitrogen, Oxygen, Argon,
Carbon dioxide and other safe gases to locally vent include Helium, Nitrous
Oxide and Hydrogen.
Semiconductor Applications gas monitoring down to 100nano meters
In the electronics industry there is a requirement to monitor smaller particle
sizes down to 0.1µm. The most advanced setup is the High-Pressure Controller
(HPC) in combination with a Solair 1100LD (0.1 to 5.0µm) particle counter.
Solair1100LD Laser Particle Counter with HPC gas flow controller used in
semiconductor, hard disk drive and flat
panel display LED industries.
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Application example of Semiconductor Nitrogen gas system being monitored down to 100nm
What is Required to monitor for microbiological particles in compressed gases?
Analyzing micro burden data at point of use outlets throughout compressed air
pipeline systems at a given time, acts as a window of observation into the
control of the facility. Maintaining control means proper preventative
maintenance, microbial monitoring scheduling and risk assessment must be
appropriate for the industry being monitored. Many accreditation bodies can
aid in the understanding of microbial limits and specifications, critical to
specific industry needs.
Once the compressed air microbial monitoring plan is approved, a sampling
procedure that provides the company with the results suitable
to its limits and specifications needs to be established. This requires the
use of a procedure that accurately measures and samples a specific volume of
air for microbial burden analysis inside the tested compressed air system.
To monitor for viable particles an active air sampler is used with a HPD
connected to the sample inlet. The other end of HPD connects to the gas line.
ISO 8573-7:2003 Compressed Air Part 7: Test method for viable
microbiological contaminant content is followed for this type of monitoring.
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Microbiological Air Sampler with Gas Sampler adapter attached to monitor gas lines for microbial contamination.
The Gas Sampler is a high-performance portable gas sampling adapter for use
with the ActiveCount microbiological air samplers
The Active Count100H illustrated above has a unique flow control interface
that stabilizes the flow, so it is appropriate for sample measurement before
the sample media is placed inside the sample head of the device.
For more information on monitoring for contamination in cleanroom applications
visit our knowledge center for the most comprehensive library of cleanroom
monitoring applications, webinars, tech papers and more:
www.golighthouse.com/en/knowledge-center/
ISO 8573 offers valuable guidelines and regulations for testing compressed gasses, a source of viable and nonviable particle contamination in cleanrooms. This is a critical portion of your contamination control plan and should not be overlooked. Either particle counters or active air samplers can be used for gas sampling, depending on your needs. Lighthouse Worldwide Solution offers comprehensive and industry standard-setting options for both possibilities, designed to meet your needs, abide by regulations, and keep your cleanroom clean.
To learn more about our environmental monitoring products, scan the QR code.
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References
- ASML | The world's supplier to the semiconductor industry
- Knowledge Center Archive - LWS Knowledge Center