Pressure-based flow rate control device and malfunction detection method therefor

A malfunction detection method for a pressure-type flow rate control device of a gas flow system comprising a plurality of pressure-type flow rate control devices,

• each pressure-type flow rate control device comprising:
• a restriction part interposed in a gas flow channel;
• an upstream-side pressure sensor for detecting a gas pressure on an upstream side of the restriction part;
• a downstream-side pressure sensor for detecting a gas pressure on a downstream side of the restriction part;
• a flow control valve provided in the gas flow channel on an upstream side of the upstream-side pressure sensor;
• and
• a computation control circuit controlling the flow control valve based on detected values of the upstream-side pressure sensor and the downstream-side pressure sensor, thereby controlling a flow rate to a set flow rate,
• a first pressure-type flow rate control device being provided to a first flow line and a second pressure-type flow rate control device being provided to a second flow line, the first flow line and the second flow line being connected to a same process chamber,
• the malfunction detection method comprising:
• a step of, when an on-off valve provided on a downstream side of the downstream-side pressure sensor and the flow control valve in the first flow line are closed, and no gas flow occurs in the first flow line while gas is supplied through the second flow line to the process chamber, by the computation control circuit of the first pressure-type flow rate control device, computing a difference between a detected value of the upstream-side pressure sensor and a detected value of the downstream-side pressure sensor and
• outputting a signal for pressure sensor malfunction determination based on the difference obtained by computation.