System and method of operation of a digital mass flow controller

#This invention relates generally to systems and methods for operating a mass flow controller (MFC) with a closed loop control system utilizing an advanced digital control algorithm. More specifically, the present invention provides a closed loop control system for operating a mass flow controller, wherein all mathematical operators are realized within a digital processor.

#Many manufacturing processes require that the introduction rates of process gases into a process chamber be strictly controlled. These types of processes use mass flow controllers (MFCs) to control the flow rate of gases. Many problems exist with current technology mass flow controllers.

#MFC's have a high cost of ownership due to unscheduled maintenance of the tools in which the MFC are installed. Often there is no indication as to a specific type of failure. Common practice is to replace the MFC since it is perceived as a dynamic device that is believed to be inherently unreliable. As a result, a significant number of MFC's are returned to the factory and found to operate as specified resulting in a no problem found failure analysis.

#A more complete understanding of the present invention and the advantages thereof may be acquired by referring to the following description, taken in conjunction with the accompanying drawings in which like reference numbers indicate like features and wherein:

#FIG. 1 provides a block diagram for one embodiment of the present invention;

#FIG. 2 illustrates a timing diagram of event management within the present invention;

#Preferred embodiments of the present invention are illustrated in the FIGUREs, like numerals being used to refer to like and corresponding parts of various drawings.

#The present invention provides an architecture system for a digital mass flow controller control system that includes embedded diagnostics within the control system. Specifically, the digital engine of the present invention will discretely monitor specific system variables for the purpose of improving troubleshooting and preventive maintenance programs. These variables include but are not limited to the flow set-point, solenoid current, ambient temperature, the base resistance of the flow sensor, the inlet pressure which may be measured by an external pressure transducer. These variables are a valuable source of information to monitor and to reduce MFC pressure sensitivity. The digital engine also will monitor power supply voltages.

#The monitored variables are used to determine a more accurate flow measure within the MFC of the present invention.