Development of the Liquid Mass-Flow Controller
Hiroshi Fujita, Naoaki Sakurai, Tokio Sugi, Shigemi Kato · Journal of the Visualization Society of Japan · 1997
It is extremely important to control liquid used in the wet process of the production of semiconductors or LCDs, because it affects processing uniformity or etching rates. Since the flow control is now made through a fixed valve, there occur changes in the flow of such liquid according to changes in its supply pressure or variations of the shape of the valve. This makes unevenness in the processing of semiconductors or LCDs. To solve this problem, we have developed a very clean, liquid mass flow controller to be used for various chemicals in the production of such products. This liquid mass flow controller consists of three components including a flow meter, an indication and control component, and a flow control valve. The controller compares the liquid flow information indicated on the indicator with the set value all the time, and moves the flow control valve upward/downward so that the flow can change to the set value. All the parts which contact liquid are made of fluorine-contained resin to prevent metal contamination of various supply liquid. The flow control valve is of a non-contact drive, magnetic coupling system that allows for a high durability and a high withstand pressure. A magnet embedded in the valve stem of the flow control valve is covered with an alloy cover, so that hydrofluoric acid can be flown through. This configuration of the controller makes it possible to maintain a steady flow of liquid in spite of flow changes due to variations in supply pressure.