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

SUPPLIERS


MKS Instruments, Inc.: http://www.mksinst.com



ARTICLES



OEM Group announces post-dice clean solutions for plasma and laser dicing methods

09/28/2017  OEM Group announced today a post-dice clean solution on the proven Cintillio Batch Spray platform following plasma and laser dicing methods.

Understanding the impact of valve flow coefficient (Cv) in fluid systems

09/26/2017  Understanding the impact of valve flow coefficient (Cv) in fluid systems for microelectronics manufacturing.

New deionized water vapor delivery module from Brooks Instrument

09/11/2017  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.

Analysis of global lithography metrology equipment market

08/25/2017  The lithography metrology equipment market is riding on the high wave of the semiconductor industry.

ALD tools evolve with industry needs

07/13/2017  Veeco Instruments (Veeco) recently announced that Veeco CNT -- formerly known as Ultratech/Cambridge Nanotech -- shipped its 500th Atomic Layer Deposition (ALD) system to the North Carolina State University.

SEMI and Solid State Technology announce 2017 “Best of West” Award finalists

06/28/2017  Each year at SEMICON West, the “Best of West” awards are presented by Solid State Technology and SEMI.

EV Group optimizes resist and lithographic processing for plasma dicing

06/20/2017  EVG resist processing and lithography systems provide pre-processing solution to enable complete damage-free advanced dry plasma dicing on thin semiconductor wafers.

SEMICON West preview: Equipment components and subsystems

06/08/2017  Attention turns to subcomponents to improve yields at advanced nodes.

Global semiconductor wafer-level equipment revenue to grow 11% in 2016

04/20/2017  Worldwide semiconductor wafer-level manufacturing equipment (WFE) revenue totaled $37.4 billion in 2016, an 11.3 percent increase from 2015, according to final results by Gartner, Inc.

3D-Micromac receives large volume orders from solar industry for its microCELL TLS system

04/18/2017  3D-Micromac AG today announced that the total received order volume for its microCELL TLS high-throughput half-cell cutting tools tops 1.5 GW for tool deliveries in 2017 to date.

EVG breaks speed and accuracy barrier in mask alignment lithography for semiconductor packaging

03/08/2017  New IQ Aligner NT achieves double throughput and alignment accuracy over previous-generation platform; opens up new applications for EVG lithography solutions.

Record spending for fab equipment expected in 2017 and 2018

03/07/2017  Today, SEMI announced updates to its World Fab Forecast report, revealing that fab equipment spending is expected to reach an industry all-time record − more than US$46 billion in 2017.