The semiconductor industry is among the few that require all components and equipment to be ultra high purity (UHP), and for manufacturing processes to be carried out in specialized cleanrooms. This is because even trace amounts of unwanted contaminants in the environment can cause defects in microchips.
Thus, the instruments, gases, and solvents used during fabrication – such as for the chemical vapor deposition (CVD) of various materials onto silicon wafers – must be ultra high purity. Many of these chemical compounds are also highly aggressive, toxic, and even pyrophoric (spontaneously igniting at room temperature). Needless to say, leak tightness is a major safety consideration during manufacturing processes.
Pressure Instruments for Semiconductor Fabrication Plants
Pressure gauges and pressure transducers are found throughout the semiconductor manufacturing process. These instruments are responsible for monitoring and controlling the pressure of solvents, forming gases, cleaning gases, and other critical fluids. But not just any gauge or sensor will do. For quality assurance, process optimization, and the protection of both people and the environment, the instruments used in fab facilities need to meet three key criteria for purity and leak tightness.
1. UHP material selection and finishing
Corrosion contaminates processes and enables fugitive emissions, while rough surfaces contain microscopic spaces that trap impurities. To meet the UHP requirements of semiconductor fabrication, WIKA uses especially high-quality stainless steel produced by double melting – vacuum induction melting (VIM) and vacuum arc remelting (VAR) – to produce an extremely homogeneous and inclusion-free alloy that meets the SEMI F20 specification for use in UHP semiconductor manufacturing applications.
The “double melts” then undergo electropolishing to ensures that surfaces are as smooth and uniform as possible. This entails putting the work pieces in an electrolyte solution and connected as an anode. The resulting electrochemical reaction does two things:
- Meticulously smooths the material’s surface layer, resulting in an average roughness of ≤13 µm.
- Forms an oxide layer that passivates the surface for extra resistance against corrosion and pitting.
2. Leak-tight welding and connections
The gases used in semiconductor manufacturing can harm people and the environment if they escape. For that reason, WIKA assembles the components of every UHP pressure transducer and UHP pressure gauge using a carefully controlled orbital welding process. The instruments then undergo a helium leak test, which is 5,000 times more sensitive than general industry standards (EN 837-1, ASME B40.100, ISO 5171) and 1,000 times more sensitive than the water bath test or the pressure drop test.
We pay particular attention to the connection surface between the instrument and the application, especially the sealing. Conventional polymers do not meet purity requirements, as those seals would outgas and thus contaminate the process. That’s why our UHP instruments use a threaded connection with a metal seal between the sealing lips. This seal is made of a softer material than the threaded connection; when mechanical force is applied during tightening, the seal adapts to the lips’ contours and metallically secures the connection.
3. UHP cleaning and packaging
To ensure the highest level of cleanliness, UHP pressure transducers and UHP pressure gauges are manufactured in a cleanroom in accordance with ISO 5. Afterwards, they undergo a double-cleaning process to remove production residue:
- The UHP instrument is first washed with distilled water, then rinsed with isopropyl alcohol, which evaporates quickly without residue.
- Once the instrument is dry, it is purged with an ultrapure gas like nitrogen.
After this rigorous cleaning cycle, the UHP instrument is double bagged so that it can be brought into a fab facility’s cleanroom without the risk of introducing contaminants.
WIKA’s Family of UHP Pressure Instruments
To meet the exacting requirements of semiconductor manufacturing, WIKA offers high-performance UHP pressure gauges and transducers. They help protect people and the environment – and boost profitability – with corrosion-resistant alloys, electropolished finishing, leak-tight welding and connections, and UHP cleaning and packaging.
UHP pressure transducers by WIKA
The WU series is our line of UHP transducers. In addition to their reliability and robustness, these instruments are extremely compact. Although not essential for quality or safety, the size of the transducer is a key consideration when designing or retrofitting a semiconductor fabrication plant. Look for instruments that are small enough to fit in tight spaces without sacrificing accuracy, stability, or features like integrated displays or EtherCAT® networking capabilities.
- The WUC-1x series features the WUC-10 (single end), WUC-15 (flow through), and WU-16 (modular surface mount). It is the most compact UHP transducer currently available in the market.
- The WU-2x series features the WU-20 (single end), WU-25 (flow through), and WU-26 (modular surface mount). With ATEX and IECEx zone 2 approvals, these state-of-the-art pressure transducers are ideal for applications in hazardous areas, both indoors and out.
- The WUD-2x series has all the specifications of the WU-2x, but with the addition of a rotatable LED display that can be read from any position. This compact UHP transducer is ideal for installing in on-tool gas distribution systems. Two programmable switch outputs enable application-specific operations for monitoring and control.
- The WUD-2x-E series builds on the success of the WU-2x and WUD-2x with the addition of EtherCAT®, the primary communication protocol for larger instrumentation and control systems. Two RJ45 ports enable cable redundancy for greater process reliability.
UHP pressure gauges by WIKA
WIKA USA is a leading manufacturer of UHP Bourdon tube pressure gauges. These instruments are produced, assembled, calibrated, and packaged in a Class 100 cleanroom at the Lawrenceville, Georgia, location.
- The 230.15 and 230.25 UHP pressure gauges have all wetted parts – Bourdon tube, socket, process connection – and the movement made of electropolished 316L (230.15) or 316L VIM/VAR (230.25) stainless steel. The case and various face seal connections are made of electropolished stainless steel (304 SS for model 203.25). Both models offer the option for a VCR® (vacuum coupling radiation)-compatible face seal fitting for an ultra-tight process connection.
- The 230.15-851 increases the functionality of UHP pressure gauges with a built-in electrical switch contact (reed contact). The 230.25w-851.3 is even more versatile with up to two switch contacts and electrical output signal. To change the switch point on either model, simply remove the window and move the pointer to the desired value.
- The 332.54-UHP is WIKA’s most accurate UHP pressure gauge. With up to ±0.25% of span (ASME B.40.1 Grade 3A), it can be used as a test gauge and for calibrating other pressure instruments.
The HYDRA line
WIKA developed the patented HYDRA double diaphragm system in cooperation with leading companies in the semiconductor industry. HYDRA-Gauges and HYDRA-Sensors offer extra safety and reliability with diaphragm seal redundancy. If the primary seal suffers a breach, the secondary seal effectively prevents the semiconductor-grade system fill fluid from contaminating the process media. All wetted parts are made of perfluoroalkoxy (PFA), a fluoropolymer with excellent resistance to extreme chemicals and high temperatures.
Additional features:
- HYDRA-Gauge: For convenient onsite readings, the pressure gauge is 360° rotatable, even after installation.
- HYDRA-Sensor: This system combines the superior performance of the S-20 pressure transmitter with the double diaphragm system. An attachable display is available as an accessory.
UHP Pressure Solutions for the Semiconductor Industry
WIKA offers the semiconductor industry a wide range of high-quality stainless steel UHP transducers and gauges – all manufactured, helium tested, calibrated, and double bag packed in a Class 100 cleanroom. We also offer accessories, like the GCS-1 gas cylinder scale, for the semiconductor industry. Contact WIKA USA for more information about these and other reliable measurement solutions for your UHP applications.
Products mentioned in this article
• WU-20/WU-25/WU-26 ultra high purity transducer
• WUD-20/WUD-25/WUD-26 UHP transducer with integrated display and optional switch contacts
• WUD-20-E/WUD-25-E/WUD-26-E UHP transducer with integrated display and EtherCAT®
• WUC-10/WUC-15/WUC-16 ultra high purity transducer
• 230.15 and 230.25 stainless steel Bourdon tube pressure gauges, UHP series
• 230.15-851 stainless steel Bourdon tube pressure gauge with reed switch, UHP series
• 230.25w-851.3 stainless steel Bourdon tube pressure gauge with up to 2 reed switches and electrical output signal, UHP series
• 332.54-UHP stainless steel Bourdon tube pressure gauge, inspector test gauge
• HYDRA-Gauge UHP pressure gauge
• HYDRA-Sensor UHP pressure transducer
• GCS-1 gas cylinder scale