Methods, systems, and apparatus for mass flow verification based on rate of pressure decay

An electronic device manufacturing system, comprising:

• a gas supply;
• a mass flow controller (MFC) coupled to the gas supply;
• a mass flow control verification system having an inlet and an outlet, the inlet coupled to the MFC, the mass flow control verification system including:
• a control volume serially coupled to the inlet to receive a gas flow;
• a flow restrictor serially coupled to the control volume and the outlet;
• and
• a controller adapted to allow the gas supply to flow gas through the mass flow control verification system to achieve a stable pressure in the control volume, terminate the gas flow from the gas supply, and measure a rate of pressure decay in the control volume over time;
• and
• a process chamber coupled to a flow path coupled to the mass flow controller and configured to receive one or more process chemistries via the mass flow controller.

A method of verifying a mass flow controller, the method comprising:

• causing a gas to flow from a gas supply through a calibrated flow standard, a control volume, and a flow restrictor at a steady pressure measured in the control volume;
• terminating the gas flow from the gas supply;
• measuring a first rate of gas pressure decay in the control volume;
• replacing the calibrated flow standard with the mass flow controller;
• causing the gas to flow from the gas supply through the mass flow controller, the control volume, and the flow restrictor at a steady pressure measured in the control volume;
• terminating the gas flow from the gas supply;
• and
• measuring a second rate of gas pressure decay in the control volume.