Patent ID: 6843122

Claim:
In a mass flow controller which is capable of accurately controlling and correctly adjusting the flowing amounts of various gases used for a fabrication of a semiconductor to flow by a desired amount, a mass flow controller for a control purge, comprising: a sensor which is adapted to detect a temperature variation at both sides of a detection coil based on a flow of a gas flowing through a tube and to output a value of a temperature difference to a control circuit; a bypass which is adapted to flow a part of gas inputted from the outside to a tube in which a sensor is installed and to divide and output a flow of gas; a valve which is adapted to adjust and output a flowing amount of gas inputted through the bypass based on a gain adjustment for a common control or a gain adjustment for a purge function of the control circuit; and a control circuit which is adapted to switch to a resistor having a gain value capable of performing a purge function by judging that the mode corresponds to a purge mode when a set value of a flowing amount inputted by a user who uses a mass flow controller in a state that a purge function mode is set, and to switch to a resistor having a gain value capable of performing a common control function by judging the mode corresponds to a common control mode when a set value of a flowing amount inputted by a user is below a threshold value, and to compute the current mass flowing amount based on a value of a temperature difference based on a gas flow inputted from the sensor in a state that a gain is adjusted for a purge mode or common control mode, to compare with a flowing amount set by a user and to control the valve for thereby decreasing or increasing a gas flowing amount inputted from the outside.