Pressure regulator and polishing apparatus having the pressure regulator
A pressure regulator capable of improving both stability of pressure and responsiveness to an input signal is disclosed. A PID controller is configured to stop producing a corrective command value from a point in time when a pressure command value has changed until a PID control starting point and to produce the corrective command value after the PID control starting point. A regulator controller is configured to control operation of a pressure regulation valve so as to eliminate a difference between the pressure command value and a first pressure value from the point in time when the pressure command value has changed until the PID control starting point, and to control the operation of the pressure regulation valve so as to eliminate a difference between the corrective command value and the first pressure value after the PID control starting point.
1. A pressure regulator comprising:
a pressure regulation valve configured to regulate a pressure of a fluid supplied from a fluid supply source;
a first pressure sensor configured to measure the pressure regulated by the pressure regulation valve;
a second pressure sensor located downstream of the first pressure sensor;
a PID controller configured to produce a corrective command value for eliminating a difference between a pressure command value inputted from an external device and a second pressure value of the fluid measured by the second pressure sensor, the PID controller being configured to stop producing the corrective command value from a point in time when the pressure command value has changed until a PID control starting point and to produce the corrective command value after the PID control starting point that represents a moment at which a preset delay time has elapsed; and
a regulator controller configured to control operation of the pressure regulation valve so as to eliminate a difference between a first pressure value of the fluid measured by the first pressure sensor and one of the pressure command value and the corrective command value, the regulator controller being configured to control the operation of the pressure regulation valve so as to eliminate the difference between the pressure command value and the first pressure value from the point in time when the pressure command value has changed until the PID control starting point, and to control the operation of the pressure regulation valve so as to eliminate the difference between the corrective command value and the first pressure value after the PID control starting point.
2. The pressure regulator according to claim 1 , wherein the delay time starts when a predetermined condition is satisfied for a first time after the pressure command value has changed, and the predetermined condition is that a deviation of the second pressure value from the pressure command value that has changed falls within a predetermined range.
3. The pressure regulator according to claim 1 , wherein the second pressure sensor has a pressure-measuring accuracy higher than that of the first pressure sensor with respect to evaluation items including linearity, hysteresis, stability, and repeatability.
4. A polishing apparatus comprising:
a polishing table for supporting a polishing pad thereon;
a top ring configured to press a substrate against the polishing pad on the polishing table, the top ring having a pressure chamber for pressing the substrate against the polishing pad;
a polishing controller configured to control operation of the top ring; and
a pressure regulator coupled to the top ring and configured to regulate pressure in the pressure chamber,
the pressure regulator including:
a pressure regulation valve configured to regulate a pressure of a fluid supplied from a fluid supply source;
a first pressure sensor configured to measure the pressure regulated by the pressure regulation valve;
a second pressure sensor located downstream of the first pressure sensor;
a PID controller configured to produce a corrective command value for eliminating a difference between a pressure command value inputted from the polishing controller and a second pressure value of the fluid measured by the second pressure sensor, the PID controller being configured to stop producing the corrective command value from a point in time when the pressure command value has changed until a PID control starting point and to produce the corrective command value after the PID control starting point that represents a moment at which a preset delay time has elapsed; and
a regulator controller configured to control operation of the pressure regulation valve so as to eliminate a difference between a first pressure value of the fluid measured by the first pressure sensor and one of the pressure command value and the corrective command value, the regulator controller being configured to control the operation of the pressure regulation valve so as to eliminate the difference between the pressure command value and the first pressure value from the point in time when the pressure command value has changed until the PID control starting point, and to control the operation of the pressure regulation valve so as to eliminate the difference between the corrective command value and the first pressure value after the PID control starting point.
5. The polishing apparatus according to claim 4 , wherein the delay time starts when a predetermined condition is satisfied for a first time after the pressure command value has changed, and the predetermined condition is that a deviation of the second pressure value from the pressure command value that has changed falls within a predetermined range.
6. The polishing apparatus according to claim 4 , wherein the second pressure sensor has a pressure-measuring accuracy higher than that of the first pressure sensor with respect to evaluation items including linearity, hysteresis, stability, and repeatability.