A New Differential Pressure Sensor Based Mass Flow Controller for Advanced Semiconductor Processing

A new type of pressure-based MFC has been developed based on a combination of absolute and differential pressure transducers. The differential pressure sensor provides a direct measurement of pressure differential across a flow restricting device such as a laminar flow element. This eliminates a requirement to have matched discrete pressure sensors across a flow restrictor to calculate accurate pressure differential. Another design consideration of the MFC is to locate the pressure sensors and flow restrictor upstream of the control valve to provide better immunity from downstream pressure fluctuations typically experienced in pulsed chemical vapor deposition applications, as well as achieve faster bleed down time of residual gases through the MFC. In addition, unlike conventional pressure-based MFCs, the differential pressure sensor-based MFCs can be operated at varying downstream pressure conditions-high vacuum and atmospheric pressures.