Apparatus for treating substrate and method for treating a substrate

A method for controlling a flow rate, the method comprising:

• oscillating ultrasonic waves at one point in a pipe through which a fluid flows, receiving the ultrasonic waves at an other point of the pipe, measuring an arrival time of the ultrasonic waves from one point to the other point to calculate a measurement flow rate of the liquid flowing in the pipe, and determining an error of the measurement flow rate by comparing the measurement flow rate with a set flow range of the liquid in a normal state;
• determining the type of error;
• and
• performing feedback control of a discharge flow rate of the liquid discharged to a target according to the type of error determined in the determining step,
• wherein the performing includes:
• a first feedback mode performed in a first error state in which the measurement flow rate is calculated in a state in which the measurement flow rate deviates from a range of the set flow rate;
• and
• a second feedback mode performed in a second error state in which the measurement flow rate is not calculated,
• wherein in the first feedback mode, an upper limit of the set flow range is lowered and a lower limit of the set flow range is increased, and
• wherein, upon determining that the first error state has stopped occurring, the performing restores the upper limit and the lower limit to the normal state.

An apparatus for treating a substrate, comprising:

• a support unit configured to support the substrate;
• a nozzle configured to discharge a liquid to a substrate supported by the support unit;
• a pipe connected to the nozzle to allow the liquid to flow inside;
• a sensor configured to oscillate ultrasonic waves at one point inside the pipe and receives ultrasonic waves at an other point inside the pipe;
• a valve installed in the pipe and configured to control an opening and closing rate of the pipe;
• and
• a controller configured to measure an arrival time of the ultrasonic waves from one point to the other to calculate a measurement flow rate of the liquid flowing in the pipe and perform feedback control of the opening and closing rate of the valve according to the measurement flow rate,
• wherein the controller is configured to determine an error of the measurement flow rate by comparing the measurement flow rate with a set flow rate of the liquid in a normal state and differently performs feedback control of the opening and closing rate of the valve according to a type of the determined error, and
• wherein the type of the error includes:
• a first error state in which the measurement flow rate deviates from a range of the set flow rate, but the measurement flow rate is calculated;
• and
• a second error state in which the measurement flow rate is not calculated,
• wherein the controller changes a first feedback mode in the first error state,
• wherein in the first feedback mode, an upper limit of the set flow range is lowered and a lower limit of the set flow range is increased, and
• wherein, upon determining that the first error has stopped occurring, the controller restores the upper limit and the lower limit to the normal state.