Mass flow controller, flow control method using the same, and substrate processing method including the same

A substrate processing method, comprising:

• placing a substrate in a substrate processing apparatus;
• and
• allowing a gas supply system to supply a process gas to the substrate processing apparatus,
• wherein supplying the process gas to the substrate processing apparatus includes:
• starting to supply the process gas to the substrate processing apparatus;
• and
• changing a flow rate of the process gas during the supply of the process gas,
• wherein changing the flow rate of the process gas includes:
• calculating a first value that is a difference between a target value of the flow rate of the process gas and a current flow rate of the process gas;
• and
• controlling a flow control valve of the gas supply system based on the first value,
• wherein controlling the flow control valve includes:
• when the first value is less than a first reference flow rate, controlling the flow control valve under a first mode;
• and
• when the first value is greater than the first reference flow rate, controlling the flow control valve under a second mode,
• wherein controlling the flow control valve under the first mode includes applying a first voltage to a first piezoelectric stack assembly of a piezoelectric actuator connected to the flow control valve, and
• wherein controlling the flow control valve under the second mode includes applying a second voltage to a second piezoelectric stack assembly on the first piezoelectric stack assembly, the second voltage being greater than the first voltage.

A mass flow controller of a substrate processing apparatus, comprising:

• a flow control valve disposed in a flow path connecting a gas supply system to the substrate processing apparatus;
• a piezoelectric actuator connected to the flow control valve and configured to drive the flow control valve;
• and
• a voltage supply device that applies a voltage to the piezoelectric actuator,
• wherein the piezoelectric actuator includes:
• a first piezoelectric stack assembly that includes a plurality of first piezoelectric stacks;
• and
• a second piezoelectric stack assembly that includes a plurality of second piezoelectric stacks and is disposed on the first piezoelectric stack assembly, and
• wherein the voltage supply device includes:
• a first voltage supply device electrically connected to the first piezoelectric stack assembly so as to apply a first voltage to the first piezoelectric stack assembly;
• and
• a second voltage supply device electrically connected to the second piezoelectric stack assembly so as to apply a second voltage to the second piezoelectric stack assembly;
• wherein the mass flow controller further comprises a processing unit configured to selectively cause either the first voltage to be provided to the first piezoelectric stack assembly or the second voltage to be provided to the second piezoelectric stack assembly.