Category Archives: Mass Flow Controllers


Brooks Instrument will showcase its newly enhanced GF125 mass flow controller (MFC) with high-speed EtherCAT connectivity and embedded self-diagnostics at the China Semiconductor Technology International Conference (CSTIC) in conjunction with SEMICON China 2018 in Shanghai.

CSTIC runs March 11-12 at the Shanghai International Convention Center, while SEMICON China takes place March 14-16 at the Shanghai New International Expo Center.

Building on the company’s proven GF Series of MFCs with EtherCAT connectivity for high-speed communications, the newly enhanced GF125 MFC features embedded self-diagnostics that automatically detect sensor drift and valve leak-by to help minimize tool downtime and improve process yield. As a result, the enhanced GF125 can run leak and drift self-diagnostics without interrupting process flow steps or requiring any hardware changes, thereby improving process gas accuracy and wafer production throughput.

Technology experts from Brooks Instrument will discuss the newly enhanced GF125 MFC capabilities with a presentation on “Advanced Mass Flow Controllers With EtherCAT Communication Protocol and Embedded Self-Diagnostics” during the CSTIC poster session.

For SEMICON China, Brooks Instrument will be co-exhibiting in booth 3675 with its regional business partner, SCH Electronics Co., Ltd., to demonstrate the newly enhanced GF125 MFC with high-speed EtherCAT connectivity and embedded self-diagnostics, along with a broad range of other mass flow meters and controllers and pressure and vacuum products for semiconductor manufacturing.

“At Brooks Instrument, we’re eager to present and exhibit at the China Semiconductor Technology International Conference and SEMICON China tradeshow,” said Mohamed Saleem, Chief Technology Officer at Brooks Instrument. “With more than 70 years of history in new technology developments, our company is focused on improving the precision and performance of mass flow, pressure and vacuum technologies to help enable advanced semiconductor manufacturing and address the challenges involved with next-generation production tools and processes.”

In addition to the newly enhanced GF125 MFC with high-speed EtherCAT connectivity and embedded self-diagnostics, Brooks Instrument will showcase other key components designed to meet critical gas chemistry control challenges and improve process yields for nodes 10nm and below, including the VDM300 vapor delivery module as well as other proven MFCs with EtherCAT.

Brooks Instrument will be exhibiting at SEMICON Taiwan 2017 with a new vaporization product, mass flow controllers with high-speed EtherCAT, and a broad range of other mass flow meters, controllers and capacitance manometers for semiconductor manufacturing.

The show runs September 13-15 at the Taipei Nangang Exhibition Center in Taipei, Taiwan. Brooks Instrument will be co-exhibiting with its regional business partner SCH Electronics Co., Ltd. at booth 168.

With more than 70 years of history in new technology developments, Brooks Instrument is focused on improving the precision and performance of mass flow, pressure and vacuum technologies to help enable advanced semiconductor manufacturing.

“At Brooks Instrument, we’re excited to be presenting for the first time at SEMICON Taiwan,” said Mohamed Saleem, Chief Technology Officer at Brooks Instrument. “We look forward to having one-on-one conversations with our colleagues from Taiwan and across the region about their key needs and the challenges they face implementing next-generation production tools and processes.”

A world leader in advanced flow, pressure, vacuum and vapor delivery solutions, Brooks Instrument will showcase key components in its portfolio designed to meet critical gas chemistry control challenges and improve process yields for 10nm and beyond nodes. This includes the new VDM300 vapor delivery module (VDM) as well as the company’s proven GF100 Series mass flow controllers (MFC) with high-speed EtherCAT® connectivity.

VDM300 Vapor Delivery Module: The self-contained VDM delivers precise amounts of ultra-high-purity deionized water (DIW) vapor to help ensure accurate and repeatable processing for functions such as plasma etching and photoresist stripping. Using proven vapor-draw vaporization technology, the VDM300 features an improved graphical user interface and firmware.

Full-scale flow capacity is up to 3,000 standard cubic centimeters per minute (sccm), with a better control turndown ratio of 20:1. Flow accuracy is ±1.0 percent of set point at 10-100 percent full-scale, while repeatability is less than ±0.2 percent of full-scale.

With its optional EtherCAT interface, the VDM300 joins the Brooks Instrument line of EtherCAT-enabled products, which also includes the company’s proven GF100 Series MFCs. The VDM300 uses the same signal processing and calibration techniques as the GF100 Series.

GF100 Series MFC with High-Speed EtherCAT Connectivity: Brooks Instrument has enhanced its industry-leading GF100 Series MFCs with high-speed EtherCAT interfaces for both high-flow and low-flow applications.

Responding to rapidly evolving requirements for next-generation tools and fabs, the GF100 Series includes several features to help boost process yields and productivity:

  • Embedded diagnostics to leverage real-time EtherCAT data acquisition capabilities for advanced fault detection and classification;
  • An ultra-stable flow sensor (less than ±0.15 percent of full-scale drift per year) enables tighter low set point accuracy and reduces maintenance requirements;
  • Improved valve shutdown reduces valve leak-by, minimizing potential first wafer effects;
  • Enhancements to the GF100 advanced pressure transient insensitivity to less than one percent of set point with five PSI per second pressure perturbations, which reduces crosstalk sensitivity for consistent mass flow delivery.

Celebrating its 70th anniversary, Brooks Instrument will be exhibiting at SEMICON West 2016 with new mass flow controllers (MFC) equipped with the high-speed EtherCAT interface, along with a broad range of other mass flow meters, controllers, vaporizers and capacitance manometers for semiconductor manufacturing.

The show runs July 12-14 at the Moscone Center in San Francisco. Brooks Instrument will be located in the South Hall at booth 1323.

A world leader in advanced flow, pressure, vacuum and vapor delivery solutions, Brooks Instrument will showcase key components in its MFC portfolio designed to meet critical gas chemistry control challenges and improve process yields for sub-20nm nodes. This includes the company’s newly enhanced GF100 Series MFCs with high-speed EtherCAT connectivity, as well as the GF135 advanced diagnostic MFC. Information on other pressure-based flow control technologies will also be available.

With its 70-year history in leading technology development, Brooks Instrument is focused on improving the precision and performance of mass flow, pressure and vacuum technologies to help enable advanced semiconductor manufacturing. Key items at SEMICON West include:

GF100 Series MFC with High-Speed EtherCAT Connectivity: Brooks Instrument has enhanced its industry-leading GF100 Series MFCs with high-speed EtherCAT interfaces for both high-flow and low-flow applications.

Responding to rapidly evolving requirements for next-generation tools and fabs, the GF100 Series features several additions to help boost process yields and productivity:

  • Embedded diagnostics to leverage real-time EtherCAT data acquisition capabilities for advanced fault detection and classification;
  • An ultra-stable flow sensor (less than 0.15 percent of S.P. drift per year) enables tighter low set point accuracy and reduces maintenance requirements;
  • Improved valve shutdown reduces valve leak-by, minimizing potential first wafer effects;
  • Enhancements to the GF100 advanced pressure transient insensitivity to less than one percent of S.P. with five PSI per second pressure perturbations, which reduces crosstalk sensitivity for consistent mass flow delivery.

GF135 Advanced Self-Diagnostic PTI MFC: The GF135 is the first “smart” pressure transient insensitive (PTI) MFC that can perform self-diagnostics such as integral rate-of-decay flow measurement without stopping the flow of process gas. This provides a competitive advantage, allowing semiconductor manufacturers to verify process gas accuracy, check valve leak-by, and monitor sensor stability in real time without removing the flow controller from the gas line – saving thousands of dollars in lost productivity.

With this unique real-time error detection technology, process and equipment engineers can reduce wafer scrap and lost production time from unacceptable flow deviations and unnecessary preventative maintenance checks. The Brooks Instrument GF135 PTI MFC also offers industry leading actual process gas accuracy and fast flow settling time for ascending and descending set points, helping to improve productivity and chamber-to-chamber matching.

Interactive Demonstration: The Brooks Instrument booth will include an interactive mass flow control demonstration where attendees can watch real-time gas flow error detection and advanced diagnostics on the GF135 MFC. Applications engineers will also be available to answer questions about the latest technologies to enhance process control, improve chamber matching and support process yield programs for semiconductor manufacturing. In addition, attendees are encouraged to visit the company in booth 1323 to share in its 70th anniversary celebration.

Recent trends in multi-sensor measurements within a mass flow controller are reviewed, with a focus on controller self-diagnostics.

BY WILLIAM VALENTINE and SHAUN PEWSEY, Brooks Instrument, Hatfield, PA

Sub 20nm nodes and complex 3D architecture are driving new process control challenges. In regards to gas delivery, these complex and highly sensitive processes require mass flow controllers (MFCs) to provide better accuracy, repeatability, long term stability and consistent dynamic response. In addition, foundries are driving a need for greater process and equipment flexibility which means the MFC must meet demanding process requirements across a wider control range.

While the quality, reliability, accuracy, response and range of MFCs continues to improve year after year, the process is still at risk because meaningful real-time in situ data is limited or nonexistent. Consequently, an error in delivered flow that is substantial enough to cause yield and scrap issues would go undetected until the next off-line flow check.

In situ data traditionally has been limited to detecting obvious hard failures such as an MFC that is not communicating; the flow output doesn’t meet the set point; or the MFC output at a zero set point is offset (not zero). A zero offset will cause a change in flow accuracy if it is due to an active change in the zero reference of the flow meter. However, zero offsets recorded during a process can also be caused by an MFC valve leak or even an isolation valve leak. A few fault detection and clarification (FDC) systems attempt to trend valve voltage but hysteresis of up to 40 percent of a reading means that only obvious failures can be detected.

In lieu of in situ flow data, flow tests are performed off-line using a technique such as chamber rate of rise (ROR). The ROR technique is simply to evacuate a known volume, flow gas into it and measure pressure change. With chamber ROR, the known volume is the processing chamber. The chamber is taken off-line (not running a process) and the MFC is given a flow set point. As gas flows into the constant volume chamber, the chamber pressure rises at a constant rate. Flow can be calcu- lated using the gas law as shown in FIGURE 1. Off-line testing reduces tool availability and can only detect flow errors after the fact, placing wafer lots at risk. Chamber ROR accuracy is +/- 3 percent of reading to +/- 5 percent of reading, depending on flow rate, gas properties, temperature gradients, manometer accuracy and chamber outgassing. Even if a better flow standard is available, flow tests are time-consuming. Chamber ROR testing every MFC at only one set point on a four-chamber etch tool can take 12 hours and is typically performed weekly.

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Process engineers are seeking an in situ flow verification process to ensure process repeatability enabling real-time FDC to alarm on conditions that could lead to wafer scrap. In situ flow data could also be used to intelligently determine when to take a tool down for flow verification tests instead of running time-consuming weekly flow maintenance checks on all MFCs.

The evolution of the MFC

In 2004, MFC manufacturers developed pressure transient insensitive (PTI) MFCs. Pressure sensors were added to measure fluctuations in pressure and advanced control concepts were introduced to compensate for pressure fluctuations in real time.

Recently, several manufacturers have experimented with using pressure and temperature signals available in PTI MFCs to determine if the controller accuracy is degrading. (The authors have used the phrase “multi- sensor diagnostics” to describe this new class of advanced MFCs). Every multi-sensor diagnostic technique involves some form of pressure rate of decay (ROD). ROD is similar to chamber ROR except instead of flowing into a constant volume and measuring the pressure rise, flow is released from a constant volume and the rate of pressure decay is measured. The concept has been around for 30 years and involves shutting off an upstream valve to create a constant volume and measuring the pressure drop within the volume. The technique wasn’t practical until digital processors with enough computational power were available to perform the technique.

Multi-sensor diagnostic instrumentation can be broken into two groups. The first group (idle self-diagnostic) can only perform self-diagnostics while the tool is idle or in between process steps. Pressure decay in the volume is measured but there is no attempt to control flow. The signature of the pressure drop is compared to a previous measurement and analyzed to look for changes. While considered an improvement, this technique does not provide true in situ data and a dynamic event during a process could easily go undetected. The second group (active self-diagnostic) actively controls process steps while the pressure decay is measured. Although more challenging to implement, this technique enables true in situ flow verification (FIGURE 2).

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Examples of idle self-diagnostics

Example 1 – thermal MFC: The upstream isolation valve is closed and the position of the flow control valve is frozen. The MFC then records pressure decay. The characteristics of the pressure decay curve are compared to a baseline curve. Changes in the curve are trended to determine if a flow sensor is degrading (FIGURE 3). Special maintenance checks would have to be programed into the tool controller to take advantage of this technique as it cannot be triggered during a normal process run.

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Example 2 – pressure-based MFC: Traditional pressure- based MFCs measure pressure drop across a laminar flow element (LFE) (FIGURE 4). The valve must be placed upstream for two reasons. First, the pressure measurement is more accurate and stable if P2 is vacuum; second, this method requires a stable inlet pressure, P1. The downside to placing the valve upstream is slow turn off. The gas must bleed through the laminar flow element after the gas is turned off. The bleed downtime is a function of gas properties, the laminar flow element volume upstream of the LFE, and pressure in the upstream volume. For multi-sensor diagnostics, the manufacturer takes advantage of the bleed-down and characterizes the pressure decay every time the MFC is given a command to shut off. Any deviation from baseline signifies a change in either the LFE flow path or pressure sensors, and would trigger the user to perform a maintenance check.

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Active self-diagnostics

Unlike idle self-diagnostics, where MFC characterization is performed when the MFC is not running a process, the latest development in multi-sensor self-diagnostics enables true in situ flow verification. This means flow anomalies can be captured in real-time during a process and assessed before several wafers are affected.

FIGURE 5 shows the cross-section of a multi-sensor self-diagnostic MFC mounted on a traditional surface mount gas stick. In this example, the MFC contains a pilot valve that enables the MFC to control the state of the upstream isolation valve. Other implementations integrate the isolation valve into the body of the MFC.

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The MFC closes the upstream isolation valve when it is ready to take a secondary flow measurement. This creates a fixed volume between the isolation valve and the MFC control valve. While pressure decays in the volume, the MFC control system continues to maintain flow while recording pressure, temperature and time. A secondary flow measurement is computed based on the pressure decay (ROD) and compared to baseline data recorded during the installation of the MFC on the tool. Once this measurement is complete, the MFC re-opens the isolation valve. PTI technology is used to compensate for the initial pressure spike, ensuring continued stable flow. The same measurement technique can be used to monitor zero drift and valve leak when the MFC is given a zero set point.

Case study on etch process tool at leading IDM

Two multi-sensor MFCs capable of active self-diagnostics were installed on an etch chamber at a major integrated device manufacturer. The MFCs were configured to store accuracy, zero drift and valve leak self-diagnostic data in flash memory located within the MFC. Perfor- mance transparency tests were run with self-diagnostics activated to ensure the technology did not change the process. The process engineers continued to perform regular off-line flow verification tests at a set point of 30 percent. No accuracy issues were detected by the tradi- tional maintenance tests and no adjustments such as re-zeroing or re-calibration were performed. Data was collected for 24 months.

Active multi-sensor diagnostics vs. off-line chamber ROR: Self-diagnostic data was collected during the regular off-line flow verification tests. FIGURE 6 shows that repeatability of self-diagnostics was 8X better than the time-consuming off-line flow verification tests.

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Active flow accuracy: The etch process utilized MFC set points of 4 percent, 12 percent, 24 percent and 40 percent (FIGURE 7). In situ active self-diagnostic data was automatically collected at each set point every three seconds during wafer processing. The MFC flow accuracy was very repeatable over the two-year test period at set points of 24 percent and 40 percent. However, flow accuracy at 4 percent shows an increase in flow of 1 percent over the two-year evaluation period. Note that off-line flow verification tests were only performed at a set point of 30 percent where the MFC is stable. Tradi- tional off-line chamber ROR flow tests proved not only to be costly, but also ineffective in detecting flow changes in this case.

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In situ zero drift trending: Increasing flow errors at low set points usually indicate a change in the zero of the flow meter. The output of a flow meter should be zero at no flow. However, all measurement instruments will eventually drift resulting in some level of zero offset. A small zero offset in the flow meter is a negligible part of the flow signal at a high flow rate. However, small zero offsets can become significant when the MFC is operated at low set point such as 4 percent shown in this tool data. Conse- quently, the self-diagnostic zero reading was analyzed to see if the accuracy error at a 4 percent set point correlated with zero drift.

The MFC zero drift rate was < 0.027 percent full scale (FS) per year. This is exceptionally stable and 20X less than the spec limit (FIGURE 8). No mainte- nance test performed today on-tool would identify this low level of zero drift. This data highlights recent improvements in the stability of thermal MFCs. However, expanding the zero drift axis does reveal a slight trend in zero of 0.045 percent FS. This offset is exactly equal to the 1.1 percent of reading flow error identified during process runs at the 4 percent set point.

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Valve leak: Valve leak is linked to first wafer effects and can indicate contamination in the gas delivery line. Excessive valve leak can cause loss of control at low set points. Self-diagnostic valve leak was trended during this study. The MFC valve leak was extremely low and stable throughout the study (FIGURE 9). Process engineers typically get concerned when valve leak reaches 0.5 percent FS to 1.0 percent FS. The data reveals excellent resolution of the valve measurement and demonstrates how easy it would be to detect changes in valve leak well before it could affect process yield.

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TABLE 1 compares data and resolution available in situ from a traditional MFC; a tool in idle mode; a tool off-line; and the active multi-sensor self-diagnostic data captured in this study. The process knowledge gained from this technology enables the process engineer to be proactive instead of reactive. In addition, an intelligent FDC system could use this data to identify more subtle MFC issues such as excessive sensitivity to changes in pressure or temperature, and even leaks in the gas stick isolation valves.

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This data highlights how current best known methods for MFC on-tool monitoring and off-line maintenance are unable to capture changes in process and ensure repeatability.
The on-tool study demonstrated multi-sensor self- diagnostic MFC technology is a process-transparent upgrade with the capability to:

• Track flow changes in situ with 10X better resolutionthan currently available for off-line flow verification processes

• Enable advanced fault detection and classification where MFC performance is tracked while running process, and logic trees can be set up to determine root causes of process degradation

• Increase tool up-time, where determining the root cause before taking the tool off-line will minimize downtime; reduce or eliminate scheduled flow-verification tests; reduce troubleshooting; and reduce tool maintenance

• Eliminate MFC-induced wafer scrap, using an alarm to alert for conditions that may lead to wafer scrap before producing product.


1. Shajii, Ali, et al, “Model-Based Solution for Multigas Mass Flow Control with Pressure Insensitivity.” Solid State Technology Magazine, July, 2004.
2. McDonald, Mike R., “Beyond Pressure Transients: Using Pressure-Insensitive Mass Flow Controllers to Control Gases in Semiconductor Manufacturing.” Semiconductor Manufac- turing Magazine, March, 2006.
3. Valentine, Bill and Pete Friedli, “New MFC Control System Improves Tool Uptime and Process Consistency.” Solid State Technology Magazine, April, 2002.

Mass Flow Controllers

December 11, 2015

In plasma-etch, chemical vapor deposition and many other processes, accurate metering of gas flow into the process chamber is critical because, beyond the process wafer, all materials that participate in the etch or deposition are introduced in gas form. In a majority of these processes, two or more of these gases react to produce the essential film or passivation layer and even slight deviations in gas flow—even on the order of 1%— can cause the process to fail.

A mass flow controller (MFC) is a device used to measure and control the flow gas into the process chamber. A gas mass flow controller is designed and calibrated to control a specific type of gas at a particular range of flow rates. The MFC can be given a setpoint from 0 to 100% of its full scale range but is typically operated in the 10 to 90% of full scale where the best accuracy is achieved. The device will then control the rate of flow to the given setpoint. MFCs can be either analog or digital.

All mass flow controllers have an inlet port, an outlet port, a mass flow sensor and a proportional control valve. The MFC is fitted with a closed loop control system which is given an input signal by the operator (or an external circuit/computer) that it compares to the value from the mass flow sensor and adjusts the proportional valve accordingly to achieve the required flow. The flow rate is specified as a percentage of its calibrated full scale flow and is supplied to the MFC as a voltage signal.

While numerous technologies have been developed to accomplish gas flow metering, the semiconductor market has focused largely on two: the thermal- based mass flow controller (MFC) and the more recently introduced pressure-based flow controller.

Today, 1% accuracy is required for challenging applications and Pewsey believes we will soon see a requirement for 0.5% accuracy. Tighter flow repeatability is also required for chamber matching.

New MFC designs feature real-time rate-of-decay flow error detection technology to continually test for changes in the device’s performance. Data can be used to improve accuracy at critical low-flow set points, set up alarm limits for critical performance parameters and monitor trends for predictive maintenance.

Additional Reading

Real time gas flow monitoring improves mass flow controller performance in wafer fab

MKS Instruments, Inc., a global provider of technologies that enable advanced processes and improve productivity, has introduced the I-250, I-500 and I-1000 Mass Flow Controllers. These products extend MKS’ I-Series full scale flow rate capabilities to 250, 500 and 1000 slm, respectively, and provide mass flow control for large scale production processes such as in Biopharm, Heat Treatment and Spray Coating. Available as both MFCs and MFMs, the IP66-rated I-250, I-500 and I-1000 are reliable, cost effective solutions for today’s most rigorous industrial applications. Simultaneous to this release, MKS is also releasing a G-Series version of the 250 slm product, the G-250.

The I-250, I-500 and I-1000 incorporate the latest digital mass flow control electronics; a proven, patented thermal sensor and mechanical design provide 1% of setpoint accuracy and precise control for full scale flow rates from 100 to 250 slm (I-250), 250 to 500 slm (I-500) and 500 to 1000 slm (I-1000). Multi-gas/multi-range capability is enabled through the onboard Ethernet interface and allows the user to change the gas and range of the instrument, reducing inventory requirements. The I-250, I-500 and I-1000 also feature the ability to convert flow measurements to the user’s unit of choice (e.g., slm, scfh, kg/hr.).

With the release of these products, the MKS I-Series mass flow products now provide customers with flow rate control capabilities extending from less than 1 sccm up to 1000 slm. Designed for use in harsh environments where resistance to liquid or dust ingress is essential, these elastomer-sealed instruments are available with analog I/O (0 to 5 VDC or 4 to 20 mA), with digital I/O soon to follow.

mks-iseries-mass flow

Brooks Instrument, a provider of advanced flow, pressure, vacuum and level solutions, has expanded its GF 40/80 Series portfolio of thermal mass flow controllers. Broader capabilities, including increased flow rates up to 50 slpm and a “normally open” valve for non-hazardous gas applications, are ideal upgrades for users of Aera (Hitachi), Celerity, Tylan, Mykrolis, Millipore and Unit mass flow controllers, as well as other competitive devices.

The GF 40/80 Series leads the market in long-term zero stability at less than 0.5% per year. This specification means the device will return more reliable accuracy data for a longer period of time, giving users greater confidence in the numbers reported. The GF 40/80 Series is also available with Brooks’ patented MultiFlo, a powerful technology that enables users to re-program the gas and/or range in minutes without the trouble and cost of removing the mass flow controller from service. Brooks has expanded the flow rates for the GF 40/80 Series from 30 slpm to 50 slpm, making these devices an excellent choice for applications that require a higher flow rate with the flexibility of a MultiFlo-capable mass flow controller.

Newly expanded RS485 communication protocols increase the flexibility and application range of the GF 40/80 Series. These versions of the RS485 protocols are ideal for users of Aera (Hitachi), Celerity, Tylan, Mykrolis, Millipore and Unit mass flow controllers, which are now part of the Brooks product line following its acquisition of Celerity Instrumentation in 2009. These end users can now upgrade to a device that offers better accuracy and repeatability while keeping the same communication protocols.

The GF 40/80 Series also integrates the EtherCAT communication protocol, which is a high-performance, ethernet-based fieldbus system designed for process control applications requiring short data update times with low communication “jitter.” Adopted by leading-edge technology companies, EtherCAT makes it easier to network instrumentation for advanced process control and diagnostics capabilities.

The GF 40 is now equipped with a “normally open” valve for non-hazardous gas applications that require a fully open valve in the event of a process interruption. Normally open valves are desirable in applications where it is preferable for the valve to remain open even if a facility loses power, so that the mass flow controller continues to provide maximum purge gas flow from the system.

The GF 80 also features a new Teflon valve seat. The valve seat is non-reactive, which allows the GF 80 to be used in applications for corrosive and reactive gases.

mass flow controllers