Flow control method for multizone gas distribution

A method of supplying a process gas to a process chamber and controlling flow conditions, comprising:

• initiating a known flow rate of a process gas to a process chamber;
• dividing said known flow rate of said process gas into a first flow of said process gas at a first flow rate and a second flow of said process gas at a second flow rate;
• measuring a first pressure associated with said first flow of said process gas;
• measuring a second pressure associated with said second flow of said process gas;
• calculating a first correlation of said flow conditions between the sum of said first pressure and said second pressure and the sum of said first flow rate and said second flow rate;
• calculating a second correlation of said flow conditions between a ratio of said first flow rate to said second flow rate and a ratio of said first pressure to said second pressure;
• controlling said first flow rate and said second flow rate according to a target flow condition by adjusting a first conductance of said first flow of said process gas and a second conductance of said second flow of said process gas;
• and
• determining a fault condition, an erroneous fault condition or a service condition associated with a variation in said flow conditions during the supply of said process gas to said process chamber by monitoring said first pressure, or said second pressure, or a combination of said first pressure and said second pressure.