METHODS AND APPARATUS FOR CONTROLLING A PLASMA PROCESSING SYSTEM

• US 20110118863A1
• Filed: 11/19/2010
• Published: 05/19/2011
• Est. Priority Date: 11/19/2009
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Valcore, John C. JR.
• Granted Patent: US 8,909,365 B2
• Time in Patent Office: Days
• US Class Current: 700/108
• CPC Class Codes: H01J 37/32 Gas-filled discharge tubes heating by discharge H05B

Abstract

A method and apparatus for compensating a bias voltage at the wafer by measuring RF voltage signals in RF driven plasma including at least an electrostatic, chuck (ESC), a capacitive divider, a signal processing and signal conditioning network is disclosed. The bias compensation device includes a capacitive divider to detect the RF voltage at the ESC, a signal conditioning network for the purpose of filtering specific RF signals of interests, and a signal processing unit for computing the DC wafer potential from the filtered RF signals.

Claims

1. A method for controlling a plasma processing system operating using multiple RF frequencies, comprising:

obtaining an RF voltage signal from an RF sensing mechanism via a high impedance path;

processing said RF voltage signal to obtain a plurality of signals, said plurality of signals including at least individual signals corresponding to individual ones of said multiple RF frequencies;

inputting said plurality of signals into a transfer function; and

providing an output of said transfer function as a control signal to control at least a subsystem of said plasma processing system.

2. The method of claim 1 wherein said RF sensing mechanism is sufficiently proximate to a non-plasma exposing component of said ESC sub-system to obtain said RF voltage signal.

3. The method of claim 2 wherein said non-plasma exposing component is a base plate.

4. The method of claim 3 wherein said RD sensing mechanism is an RF rod.

5. The method of claim 1 wherein said high impedance path is implemented at least by a capacitor divider network.

6. The method of claim 1 wherein said plurality of signals also include at least a signal corresponding to an unfiltered broadband version of said RF voltage signal.

7. The method of claim 1 wherein said processing includes calibrating said plurality of signals.

8. The method of claim 1 wherein said transfer function represents a linear transfer function.

9. The method of claim 8 wherein said linear transfer function is obtained using multi-variate analysis.

10. The method of claim 1 wherein said transfer function represents a non-linear transfer function.

11. The method of claim 10 wherein said non-linear function is obtained using a power equation.

12. The method of claim 1 wherein said processing includes at least analog filtering.

13. The method of claim 1 wherein said processing includes at least digital signal processing.

14. A plasma processing system configured for processing at least one wafer disposed on an electrostatic chuck (ESC), comprising:

an RF sensing mechanism, said RF sensing mechanism is sufficiently proximate to a non-plasma exposing component of said ESC to obtain an RF voltage signal;

a high impedance arrangement coupled to said RF sensing mechanism to facilitate acquisition of said RF voltage signal while reducing perturbation of RF power driving a plasma in said plasma processing system;

a signal processing arrangement configured to receive said RF voltage signal and to apply one of a digital and analog version of said RF voltage signal to a transfer function to obtain a transfer function output; and

an ESC power supply subsystem configured to receive said transfer function output as a feedback signal to control said plasma processing system during processing of said at least one wafer.

15. The plasma processing system of claim 14 wherein said non-plasma exposing component is a base plate.

16. The plasma processing system of claim 14 wherein said RF sensing mechanism is an RF rod.

17. The plasma processing system of claim 14 wherein said high impedance arrangement is implemented at least by a capacitor divider network.

18. The plasma processing system of claim 14 wherein said RF voltage signal is processed by said signal processing arrangement into a plurality of signals that includes at least a signal corresponding to an unfiltered broadband version of said RF voltage signal.

19. The plasma processing system of claim 18 wherein said processing includes calibrating said plurality of signals.

20. The plasma processing system of claim 14 wherein said transfer function represents a linear transfer function.

21. The plasma processing system of claim 14 wherein said transfer function represents a non-linear transfer function.