As semiconductor devices get faster and levels of integration increase, more detail is required in device construction, to achieve this new materials are being introduced into the 300 mm wafer production process to increase production efficiency. As a result of this trend, there is now a larger variety of liquid sources and flow rates used in the semiconductor manufacturing process.

The Digital series of flow controller uses a Peltier element which cools the liquid rather than the more common thermal heating element; this gives the advantage of removing the risk of boiling those chemicals that have a low boiling point, thus allowing a greater range of chemical control.

HORIBASTEC is the world leader in this area offering a full line up liquid source vaporization control systems utilizing different methodologies including baking, direct injection and mixing to guarantee efficient and stable delivery of vapor to the point of use. Auto refill systems complete the lineup offering uninterrupted, safe and reliable delivery of the liquid precursor increasing uptime and reducing operator handling and risk of process contamination.

Cooling measurement method.

The flow rate sensor in the LF-F/LV-F series of fine mass flow controllers for liquids consists of an electronic cooling element (Peltier element) that is in contact with a capillary tube, as well as several temperature detection elements. When the liquid is flowing, the sensor detects the temperature rise (?T) corresponding to the flow rate and displays it as flow rate. Unlike methods where heat is added, this cooling method enables flow rate measurement of liquids with low boiling points. It also prevents problems with interference due to the influence of secondary discharge (vaporization) and makes accurate flow rate measurements possible.

Structure/Operating principle.

The LV-F series of mass flow controllers and LF-F series of mass flow meters use the same measurement principle. The LV-F also has a piezo actuator valve and an internal comparison control circuit. These compare the flow rate setting signal and the flow rate output signal and automatically control the valve aperture so that the two signals will match to control the liquid. Since they use a feedback control system, there are no flow rate variations as a result of external factors, and, there fore, stable, accurate control is possible. The use of piezo actuator valve, which is both stable and does not generate heat, as the control valve makes these units ideal for flow control of liquids with low boiling points.