Real time monitoring with closed loop chucking force control
Embodiments disclosed herein include a method for minimizing chucking forces on a workpiece disposed on a electrostatic chuck within a plasma processing chamber. The method begins by placing a workpiece on an electrostatic chuck in a processing chamber. A plasma is struck within the processing chamber. A deflection force is monitored on the workpiece. A chucking voltage is applied at a minimum value. A backside gas pressure is applied at a minimum pressure. The chucking voltage and or backside gas pressure is adjusted such that the deflection force is less than a threshold value. And the chucking voltage and the backside gas pressure are simultaneously ramped up.
1. A method for minimizing chucking forces on a workpiece disposed on a electrostatic chuck within a plasma processing chamber, the method comprising:
placing a workpiece on an electrostatic chuck in a processing chamber;
striking a plasma within the processing chamber;
monitoring a deflection force on the workpiece;
applying a chucking voltage at a minimum value;
applying a backside gas pressure at a minimum pressure;
adjusting the chucking voltage and or backside gas pressure such that the deflection force is less than a threshold value; and
simultaneously ramping up the chucking voltage and the backside gas pressure.
2. The method of claim 1 , further comprising:
reversing the process for de-chucking.
3. The method of claim 1 , wherein a minimum value of the chucking voltage force is less than a minimum value of the backside gas pressure.
4. The method of claim 1 , wherein the value of the backside gas pressure is less than the value of the chucking voltage force when the workpiece is chucked.
5. The method of claim 1 , wherein the deflection force is between about 50 mTorr and about 50 Torr.
6. The method of claim 5 , wherein the deflection force is about 1 Torr or less.
7. The method of claim 1 , further comprising:
Introducing a small time delay between the striking of the plasma and the chucking the workpiece.
8. The method of claim 7 , wherein the small time delay is between about 200 milliseconds and about 10 seconds.
9. The method of claim 1 , further comprising:
providing a closed loop control of the chucking force and backside gas pressure; and
minimizing the chucking force in response to the closed loop control.
10. The method of claim 1 , further comprising:
adjusting the clamping voltage to the ESC so that the clamping force reaches and maintains a target total clamping force.
11. The method of claim 1 , wherein applying the chucking voltage at the minimum value, further comprises:
selecting the chucking voltage to achieve a minimum force.