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



US demand for semiconductor machinery to total $7.4B in 2021

02/16/2018  Growth in demand for wafer processing equipment will account for the majority of value growth.

CSTIC and SEMICON CHINA 2018: Brooks Instrument to present new mass flow controller with self-diagnostics​

02/09/2018  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.

Leak check semiconductor process chambers quickly and reliably

02/08/2018  INFICON,a manufacturer of leak test equipment, introduced the UL3000 Fab leak detector for semiconductor manufacturing maintenance teams to easily check the tightness of vacuum chambers for wafer production.

Boston Semi Equipment develops custom automation modules for strip handling equipment

01/31/2018  Boston Semi Equipment (BSE) today announced that it has started shipping units of its new strip load/unload module to a top 10 semiconductor manufacturer.

Turbulent times ahead for trade

01/25/2018  International trade is one of the best tools to spur growth and create high-skill and high-paying jobs. Over 40 million American jobs rely on trade, and this is particularly true in the semiconductor supply chain. Over the past three decades, the semiconductor industry has averaged nearly double-digit growth rates in revenue and, by 2030, the semiconductor supply chain is forecast to reach $1 trillion.

NAURA Akrion Inc. acquired Akrion’s surface preparation business

01/18/2018  Beijing NAURA Microelectronics Equipment Co.,Ltd. and Akrion Systems LLC today jointly announced that the previously announced acquisition by NAURA has been completed.

$55.9B semiconductor equipment forecast: New record with Korea at top

12/12/2017  Today, SEMI, the global industry association representing the electronics manufacturing supply chain, released its Year-end Forecast at the annual SEMICON Japan exposition.

CVD completes purchase of 180,000 sq. ft. facility

12/08/2017  This new facility will be the primary manufacturing center for the Company’s wholly owned subsidiary, CVD Materials Corporation.

Semiconductor industry continues upward trend toward record year

11/30/2017  The semiconductor industry continued its upward trend in the third quarter of 2017, notching 12 percent sequential growth with strength across all application markets, according to IHS Markit.

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.