Application Note

Stable & fast gas flow control for vacuum deposition

Mass Flow Controllers are used in vacuum deposition equipment for the supply of gas into the process. They make sure this can be done in a controlled and precise way. Ideally the flow instruments can react quickly (fast response) and reach a setpoint within milliseconds. For processes like this, users can benefit from the FLEXI-FLOW Compact.

Reactive sputtering in practice
Physical Vapor Deposition (PVD) sputtering or reactive sputtering, is a layer deposition technique where sputtered particles react with a gas that is introduced to the sputtering chamber. High-energy argon is applied to e.g. metal (aluminum), releasing a vapor of sputtered metal particles. They react with the supplied reactive gases, allowing very thin ceramic layers to be deposited on glass, silicon wafers, metal or polymer. Reactive sputtering is used for applying coatings for anti-reflection, hardening, anti-wear, etc.

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Flow control in Reactive sputtering for coated glass
Vacuum deposition by reactive sputtering for coated glass

Requirements for reactive sputtering

Fast flow control is essential in vacuum deposition technology. Each second saves time and energy, resulting in a better efficiency of the deposition equipment. The gas flows need to be supplied with a large dynamic flow range, in a reproducible way and with long-term stability. So the quality remains assured.

Important topics

  • Fast response flow control
  • Shut-off functionality
  • Large dynamic range
  • Communication interfaces

The solution

The FLEXI-FLOW Compact Mass Flow Controller reaches 150 msec response time without overshoot. This way, we can meet the requirements of vacuum coating customers that need multi-channel flow solutions offering stable and fast flow control in combination with shut-off functionality.

Fast response flow control

End-users of vacuum deposition equipment require a very fast responding gas supply system. They optimize process conditions like pressure and gas flow and monitor the result by measuring the coating thickness during the coating process. During the process, there should be a stable, controlled gas flow to keep the coating of the correct thickness and composition.

Fast flow control with FLEXI-FLOW

When the sputter system observes that the thickness or transparency is deviating, it corrects the deposition process by adjusting the gas flows. Therefore, a very fast flow control is desired with a response in the 150-millisecond range.

The FLEXI-FLOW mass flow controller can do this. In case there are variations in inlet pressure, the gas flow controller keeps the flow at the setpoint as responsive as possible. When there are changes in the reactor chamber, the flow controller receives a new setpoint. This way, fast response to new setpoints results in less waste and less rejected products.

Shut-off functionality

A shut-off valve can be integrated to minimize leakage to the vacuum chamber in the phase of vacuuming - especially useful in ultra-high vacuum reactors.

Large dynamic range

The large dynamic flow range with a high turndown ratio of at least 1:1000 reduces the number of models and spare parts needed and improves the flexibility of the vacuum deposition equipment.

Communication interfaces

Compact multi-channel solutions are available with interface of choice through a gateway, making use of industrial protocols like Ethernet, EtherCAT and Profinet. Data produced in this way can be used for predictive maintenance.

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Flow scheme vacuum chamber
Example of process scheme with 6 Mass Flow Controllers. Shut-off valves are implemented to guaranty very low leak rate to the vacuum chamber