CONTROL SYSTEMS EMPLOYING DEFLECTION SENSORS TO CONTROL CLAMPING FORCES APPLIED BY ELECTROSTATIC CHUCKS, AND RELATED METHODS

• US 20150138687A1
• Filed: 01/17/2014
• Published: 05/21/2015
• Est. Priority Date: 11/19/2013
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: BOYD, Wendell Jr., PARKHE, Vijay D., MAKHRATCHEV, Konstantin, ONO, Masanori, THACH, Sehn, BUSCHE, Matthew
• Granted Patent: US 9,558,981 B2
• Time in Patent Office: Days
• US Class Current: 361/234
• CPC Class Codes: H01L 21/67288 Monitoring of warpage, curvature, damage, defects or the like
• CPC Class Codes: H01L 21/6833 Details of electrostatic chucks

Abstract

A control system that includes deflection sensors which can control clamping forces applied by electrostatic chucks, and related methods are disclosed. By using a sensor to determine a deflection of a workpiece supported by an electrostatic chuck, a control system may use the deflection measured to control a clamping force applied to the workpiece by the electrostatic chuck. The control system applies a clamping voltage to the electrostatic chuck so that the clamping force reaches and maintains a target clamping force. In this manner, the clamping force may secure the workpiece to the electrostatic chuck to enable manufacturing operations to be performed while preventing workpiece damage resulting from unnecessary higher values of the clamping force.

Claims

1. A control system, comprising:

an electrostatic chuck;

a sensor positioned to determine a deflection of a workpiece into at least one recess of the electrostatic chuck as the electrostatic chuck applies a clamping force to the workpiece; and

a controller programmed to determine from the deflection the clamping force applied to the workpiece by the electrostatic chuck, and to adjust a clamping voltage at the electrostatic chuck so that the clamping force reaches and maintains a target clamping force.

2. The control system of claim 1, wherein the sensor comprises a proximity sensor.

3. The control system of claim 1, wherein the sensor comprises an interferometric displacement sensor.

4. The control system of claim 1, wherein the sensor comprises a capacitive proximity sensor.

5. The control system of claim 1, wherein the electrostatic chuck comprises a material comprising at least one of aluminum oxide or aluminum nitride.

6. The control system of claim 1, wherein the at least one recess of the electrostatic chuck is formed by adjacent mesas of a plurality of mesas of the electrostatic chuck, and the plurality of mesas support the workpiece.

7. The control system of claim 1, wherein the sensor emits a radiation to a surface of the workpiece and measures the radiation reflected to determine the deflection.

8. The control system of claim 7, wherein the sensor comprises an end portion of an optical fiber that emits the radiation within from the at least one recess.

9. The control system of claim 8, wherein the optical fiber receives the portion of the radiation which is reflected.

10. The control system of claim 1, wherein the sensor comprises a load cell disposed in the at least one recess abutting against the workpiece to determine the deflection.

11. The control system of claim 10, wherein the load cell comprises a Teflon coated plunger to abut against the workpiece.

12. The control system of claim 6, wherein the sensor includes an electrical current measurement sensor, comprising:

a first electrode that produces a first voltage at a first mesa of the adjacent mesas; and

a second electrode that produces a second voltage at a second mesa of the adjacent mesas,

wherein the sensor is configured to determine the deflection based on an electrical current created across a portion of the workpiece from the first voltage and the second voltage.

13. A plasma chamber, including a control system, comprising:

an electrostatic chuck;

a sensor positioned to determine a deflection of a workpiece into at least one recess of the electrostatic chuck as the electrostatic chuck applies a clamping force to the workpiece; and

a controller programmed to determine from the deflection the clamping force applied to the workpiece by the electrostatic chuck, and to adjust a clamping voltage at the electrostatic chuck so that the clamping force reaches and maintains a target clamping force.

14. The control system of claim 13, wherein the controller comprises a proportional-integral-derivative (PID) controller.

15. The control system of claim 14, wherein the PID controller determines a clamping voltage correction.

16. The control system of claim 15, wherein the controller applies a clamping voltage to the electrostatic clamp, wherein the clamping voltage is the sum of the clamping voltage correction and a clamping voltage setpoint.

17. The control system of claim 15, wherein the PID controller receives a clamping force error, wherein the clamping force error being a difference between the clamping force and a clamping force setpoint.

18. A method for controlling a clamping force of an electrostatic chuck, comprising:

determining with a sensor a deflection of a workpiece into at least one recess of an electrostatic chuck;

determining with a controller a measured clamping force applied to the workpiece by the electrostatic chuck; and

applying with the controller a clamping voltage to the electrostatic chuck so that the clamping force reaches and maintains a target clamping force.

19. The method of claim 18, wherein the determining with the sensor comprises emitting a radiation to a surface of the workpiece and measuring a portion of the radiation which is reflected.

20. The method of claim 18, wherein the determining with the sensor comprises abutting a load cell against the workpiece.