A process for fabricating a flow control device which includes a housing with separate main flow and flow control (servo) passages between an inlet port and an exit port. A control chamber in the housing is in fluid communication with the servo passage. A flexible membrane forms a partition between the main flow passage and the control chamber. The servo passage includes a variable servo orifice upstream of the control chamber and a fixed orifice downstream of the chamber. When the servo valve is open to permit passage of fluid into the control chamber, the resultant pressure on the membrane maintains the main valve closed. The main valve opens in response to closing the servo valve. The fixed orifice has a profile sufficiently small to provide for an acceptable leak or continuous fluid flow through the device when the servo valve is open, and further provides for a soft start when the servo valve is closed to open the main valve. The fixed orifice, servo valve including a servo valve orifice and electrostatically controlled closure tabs, and a microbridge flow sensing device, are advantageously formed on a monolithic semiconductor chip mounted inside the housing. Significantly, a dielectric layer is deposited on a portion of the substrate surface surrounding the orifice formed therein to form the mesa and subsequently other dielectric and conductive layers are deposited with etching.

Patent Information

Number	US  5441597
Country	US
Status	Issued
Date	08/15/1995