Application Note

Flow control in MOCVD application

Stable & accurate flow control

Bronkhorst mass flow controllers play an indispensable role in the manufacturing of LEDs by MOCVD. A stable and accurate flow control of hydrogen gas results in improved MOCVD process conditions and thereby in LED product quality.

Metal organic chemical vapour deposition (MOCVD) is one of the manufacturing steps in LED production. In MOCVD, a carrier gas guides one or more vaporous organometallic compounds to a wafer. There, these compounds decompose and deposit very thin crystalline layers on the wafer to make red, green, or blue emitting LEDs. The type of material deposited – generally some kind of nitride – determines the light colour to be emitted.

A large manufacturer of mini-LEDs for TV screens uses MOCVD with hydrogen as carrier gas. They requested the help of Bronkhorst Taiwan for a reliable and stable solution to supply this carrier gas. 

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Flow control in MOCVD process

Requirements for flow control in MOCVD application

The customer requested a more accurate flow control of hydrogen gas supply, to improve their MOCVD process and therewith the quality of the LEDs. Stable flow conditions and a fast response of the flow controller to changes in settings are required.

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Important topics

  • Stable mass flow control for hydrogen gas
  • Fast control
  • Good service

Process solution

To improve the quality of the MOCVD process and therefore the LED quality, Bronkhorst Taiwan supplied multiple EL-FLOW Metal Sealed mass flow controllers to be used as standard devices inside the AIXTRON generation G3/G4 MOCVD equipment.

The aim of these flow controllers is to control the hydrogen carrier gas flow. A stable carrier gas flow is key to the quality of the entire process, as its flow rate determines the deposition rate of LED components. 

The Bronkhorst mass flow controllers supply a lot of gas to fill the chambers of the MOCVD reactor equipment. Several different types are used: small EL-FLOW mass flow controllers with typical gas flow rates of 20 ml/min ranging to large ones with flow rates of 20 l/min. 

Flow control in MOCVD process

The metal-to-metal seal construction with excellent resealing capability are unique features of the EL-FLOW Metal Sealed mass flow controllers. Moreover, they have a high-quality surface which makes them highly suitable for the stringent requirements in semiconductor and solar industries. In the current application, Bronkhorst EL-PRESS Metal Sealed pressure controllers are used as well.

Using these devices in the application results in a highly stable hydrogen gas flow rate with a fast response time to changes in process conditions. This improvement will lead to cost reductions as well as to reduction of stock items. 

Full-Service on-site

The Bronkhorst Taiwan service office is a full-service department. They perform calibrations as well as repairs to flow devices, even if they are 10 years old. Besides that, the service team visits the customers on-site for advice on how to use the flow devices and give tips on how to improve their process. 

For this project the service team helped the customer to fine-tune the process by adjusting the PID setting of the mass flow devices, to get a better control performance in the MOCVD system. This level of service provision has not been matched by any competing suppliers.

Bronkhorst full-service on-site

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