Wafer release mechanism

1. A method, comprising:

placing a wafer onto a chuck equipped with lift pins, wherein one or more of the lift pins incorporates thereon an integrated pressure sensor configured to measure a pressure exerted by the wafer;

measuring a first pressure applied to the one or more lift pins by the wafer;

lowering the lift pins to place the wafer on the chuck;

applying a first voltage to the wafer through the chuck;

processing the wafer; and

removing the wafer from the chuck, wherein removing the wafer comprises:

applying a second voltage to the wafer;

flowing a gas over the wafer to remove a residual electrostatic charge;

pressing the one or more lift pins against the wafer to measure a second pressure exerted by the wafer; and

in response to the measured second pressure being substantially equal to the first pressure, raising the wafer, with the lift pins, above the chuck.

2. The method of claim 1 , wherein the first voltage has an opposite polarity to the second voltage.

3. The method of claim 1 , wherein measuring the first pressure comprises measuring a weight of the wafer.

4. The method of claim 1 , wherein measuring the first pressure comprises resting the wafer on the one or more lift pins above the chuck.

5. The method of claim 1 , wherein the second pressure corresponds to an electrostatic force and a weight of the wafer.

6. The method of claim 1 , wherein removing the wafer further comprises:

in response to the second pressure being higher than the first pressure, re-flowing the gas over the wafer;

pressing the one or more lift pins against the wafer to measure a third pressure exerted by the wafer; and

in response to the measured third pressure being substantially equal to the first pressure, raising the wafer, with the lift pins, above the chuck.

7. A method, comprising:

placing a wafer onto a chuck equipped with lift pins, wherein one or more of the lift pins incorporates thereon an integrated pressure sensor configured to measure a pressure exerted by the wafer;

resting the wafer on the lift pins above the chuck to measure a first pressure applied to the one or more lift pins by the wafer;

lowering the lift pins to place the wafer on the chuck;

processing the wafer; and

removing the wafer from the chuck, wherein removing the wafer comprises:

flowing a gas over the wafer;

pressing the lift pins against the wafer to measure a second pressure exerted on the one or more lift pins by the wafer; and

in response to the measured second pressure being substantially equal to the first pressure, raising the wafer, with the lift pins, above the chuck.

8. The method of claim 7 , wherein the first pressure corresponds to a weight of the wafer and the second pressure corresponds to the weight of the wafer and to one or more forces applied to the wafer.

9. The method of claim 8 , wherein the one or more forces comprise an electrostatic force, a pressure differential force, or a combination thereof.

10. The method of claim 7 , wherein removing the wafer further comprises:

in response to the measured second pressure being higher than the first pressure, re-flowing the gas over the wafer;

pressing the lift pins against the wafer to measure a third pressure exerted to the one or more lift pins by the wafer; and

in response to the measured third pressure being substantially equal to the first pressure, raising the wafer, with the lift pins, above the chuck.

11. A method, comprising:

lowering, with lift pins, a wafer onto a chuck;

applying a first voltage to the wafer through the chuck;

applying, after processing the wafer, a second voltage to the wafer;

flowing a gas over the wafer to remove a residual electrostatic charge;

measuring, prior to processing the wafer, a first pressure applied to the lift pins by the wafer;

measuring, after processing the wafer, a second pressure exerted by the wafer, wherein measuring the first and second pressures comprises sensing pressures using one or more pressure sensors attached to corresponding lift pins; and

in response to the second pressure being substantially equal to the first pressure, raising, with the lift pins, the wafer above the chuck.

12. The method of claim 11 , wherein measuring the first pressure comprises measuring a weight of the wafer.

13. The method of claim 11 , wherein measuring the second pressure comprises measuring one or more forces applied to the wafer and a weight of the wafer.

14. The method of claim 13 , wherein the one or more forces comprise an electrostatic force, a pressure differential force, or a combination thereof.

15. The method of claim 11 , wherein measuring the first and second pressures comprises measuring the first and second pressures using the one or more pressure sensors, wherein each pressure sensor has a cross sectional area that is substantially equal to a cross sectional area of the lift pins.

16. The method of claim 15 , wherein measuring the first and second pressures with the one or more pressure sensors comprises pressing the one or more pressure sensors against a backside surface of the wafer to measure the first and second pressures exerted on the lift pins by the wafer.

17. The method of claim 11 , further comprising:

in response to the second pressure being higher than the first pressure, re-flowing the gas over the wafer.

18. The method of claim 11 , wherein flowing the gas comprises flowing an inert gas.

19. The method of claim 11 , wherein flowing the gas comprises flowing helium, argon, xenon, or neon.

20. The method of claim 11 , the one or more pressure sensors comprising one or more of a piezoresistive pressure sensor, an electromagnetic pressure sensor, and an optical pressure sensor.