Methods and apparatus for determining an etch endpoint in a plasma processing system

• US 20030183335A1
• Filed: 03/27/2003
• Published: 10/02/2003
• Est. Priority Date: 09/30/1998
• Status: Abandoned Application

• Current Assignee: Eric A. Hudson, Jaroslaw W. Winniczek, Mark Wiepking, M.J. Francois Chandrasekar Dassapa
• Original Assignee: Eric A. Hudson, Jaroslaw W. Winniczek, Mark Wiepking, M.J. Francois Chandrasekar Dassapa
• Inventors: Dassapa, M.J. Francois Chandrasekar, Hudson, Eric A., Winniczek, Jaroslaw W., Wiepking, Mark
• Application Number:
  US10/401,640
• Publication Number:
  US 20030183335A1
• Time in Patent Office: Days
• US Class Current: 156/345.1
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H01J 37/32963 End-point detection
• CPC Class Codes: H01L 22/26 Acting in response to an ongoing measurement without interruption of processing, e.g. endpoint detection, in-situ thickness measurement endpoint detection arrangements in CMP apparatus B24B37/013, in discharge apparatus H01J37/32

Abstract

Methods and apparatus for ascertaining the end of an etch process while etching through a target layer on a substrate in a plasma processing system which employs an electrostatic chuck. The end of the etch process is ascertained by monitoring the electric potential of the substrate to detect a pattern indicative of the end of the etch process. By the way of example, changes to this potential may be observed by monitoring the current flowing to the pole of the electrostatic chuck. Upon ascertaining the pattern indicative of the end of the etch process, for example by monitoring the current signal, a control signal is produced to terminate the etch. If a bias compensation power supply is provided to keep the currents flowing to the poles of the electrostatic chuck substantially equal but opposite in sign throughout the etch, the compensation voltage output by the bias compensation power supply may be monitored for the aforementioned pattern indicative of the end of the etch process in order to terminate the etch.

Claims

1. An endpointing arrangement for ascertaining an end of an etch process while etching through a target layer on a substrate in a plasma processing system, comprising:

an electrostatic chuck having a first pole and a second pole;

a first DC power supply coupled to said first pole and said second pole for supplying chucking voltages to said first pole and said second pole;

a first current monitoring circuit coupled between said first pole and said first DC power supply for monitoring a first current supplied to said first pole, said first current monitoring circuit outputting a first signal indicative of said first current;

a second current monitoring circuit coupled between said second pole and said first DC power supply for monitoring a second current supplied to said second pole, said second current monitoring circuit outputting a second signal indicative of said second current;

a differential amplifier arrangement coupled to said first current monitoring circuit and said second current monitoring circuit, said differential amplifier arrangement receives said first signal and said second signal as input and outputs a control signal;

a variable DC power supply coupled to said differential amplifier arrangement for receiving said control signal, said variable DC power supply being configured to output a compensation voltage for biasing said first DC power supply responsive to said control signal; and

an endpoint monitoring circuit coupled to said variable DC power supply, said endpoint monitoring circuit receives as an input said compensation voltage and includes circuitry for analyzing said compensation voltage for a pattern characteristic of said end of said etch process, said endpoint monitoring circuit further including circuitry for outputting an endpoint signal indicative of said end of said etch process upon ascertaining said pattern in said compensation voltage.

2. The endpointing arrangement of claim 1 wherein said compensation voltage biases said first DC power supply to maintain said first current and said second current substantially constant during said etch process.

3. A method for ascertaining an end of an etch process while etching through a target layer on a substrate in a plasma processing system, said plasma processing system including an electrostatic chuck having a first pole, a first DC power supply coupled to said first pole for supplying a chucking voltage to said first pole, a first current monitoring circuit coupled between said first pole and said first DC power supply for monitoring a first current supplied to said first pole, said first current monitoring circuit outputting a first signal indicative of said first current, and a variable DC power supply configured to output a compensation voltage for biasing said first DC power supply responsive to said first signal, thereby causing said chucking voltage to vary responsive to said compensation voltage, said method comprising:

coupling an endpoint monitoring circuit to said variable DC power supply, said endpoint monitoring circuit having an endpoint monitoring input and an endpoint monitoring output;

receiving at said endpoint monitoring input said compensation voltage;

analyzing, using said endpoint monitoring circuit, said compensation voltage for a pattern characteristic of said end of said etch process; and

outputting at said endpoint monitoring output an endpoint signal indicative of said end of said etch process upon ascertaining said pattern in said compensation voltage.

4. The method of claim 3 wherein said electrostatic chuck includes a second pole coupled to said first DC power supply, said plasma processing system includes a second current monitoring circuit coupled between said second pole and said first DC power supply for monitoring a second current supplied to said second pole, wherein said compensation voltage output by said variable DC power supply is responsive to both said first signal and a second signal output by said second current monitoring circuit, said second signal being indicative of said second current.

5. The method of claim 4 wherein said plasma processing system includes a differential amplifier arrangement coupled to said first current monitoring circuit and said second current monitoring circuit, said differential amplifier arrangement receives said first signal and said second signal as input and outputs a control signal to said variable DC supply to cause said compensation voltage output by said variable DC power supply to vary responsive to both said first signal and said second signal.

6. The method of claim 4 wherein said first signal and said second signal is employed by said variable DC power supply to maintain said first current and said second current substantially constant during said etch process.

7. The method of claim 4 wherein said endpoint monitoring circuit includes a general purpose microcomputer.

8. The method of claim 4 wherein said electrostatic chuck represents a Johnsen-Rahbek chuck.

9. The method of claim 4 wherein said substrate includes a conductive layer underlying said target layer.

10. The method of claim 4 wherein said substrate includes a dielectric layer underlying said target layer.

11. The method of claim 4 wherein said target layer represents a silicon dioxide-containing layer, said substrate further includes a dielectric layer underlying said target layer.

12. The method of claim 4 wherein said target layer represents a low dielectric constant layer, said substrate further includes a dielectric layer underlying said target layer.

13. An endpointing arrangement for ascertaining an end of an etch process while etching through a target layer on a substrate in a plasma processing system, comprising:

an electrostatic chuck having a first pole;

a first DC power supply coupled to said first pole for supplying a chucking voltage to said first pole;

a first current monitoring circuit coupled between said first pole and said first DC power supply for monitoring a first current supplied to said first pole, said first current monitoring circuit outputting a first signal indicative of said first current;

a variable DC power supply configured to output a compensation voltage for biasing said first DC power supply responsive to said first signal, thereby causing said chucking voltage to vary responsive to said compensation voltage;

an endpoint monitoring circuit coupled to said variable DC power supply, said endpoint monitoring circuit receives as an input said compensation voltage and includes circuitry for analyzing said compensation voltage for a pattern characteristic of said end of said etch process, said endpoint monitoring circuit further including circuitry for outputting an endpoint signal indicative of said end of said etch process upon ascertaining said pattern in said compensation voltage.

14. The endpointing arrangement of claim 13 wherein said electrostatic chuck includes a second pole coupled to said first DC power supply, said endpointing arrangement further comprises:

a second current monitoring circuit coupled between said second pole and said first DC power supply for monitoring a second current supplied to said second pole, said second current monitoring circuit outputting a second signal indicative of said second current, wherein said compensation voltage output by said variable DC power supply is responsive to both said first signal and said second signal.

15. The endpointing arrangement of claim 14 wherein said compensation voltage output by said variable DC power supply is configured to keep said first current and said second current substantially equal but opposite in sign.

16. The endpointing arrangement of claim 14 wherein said compensation voltage output by said variable DC power supply is configured to keep said first current and said second current substantially constant throughout said etching irrespective whether magnitudes of said first current and said second current are equal.

17. The endpointing arrangement of claim 14 further comprising a differential amplifier arrangement coupled to said first current monitoring circuit and said second current monitoring circuit, said differential amplifier arrangement receives said first signal and said second signal as input and outputs a control signal to said variable DC supply to cause said compensation voltage output by said variable DC power supply to vary responsive to both said first signal and said second signal.

18. The endpointing arrangement of claim 14 wherein said endpoint monitoring circuit includes a general purpose microcomputer.

19. The endpointing arrangement of claim 14 wherein said electrostatic chuck represents a Johnsen-Rahbek chuck.

20. The endpointing arrangement of claim 14 wherein said substrate includes a conductive layer underlying said target layer.

21. The endpointing arrangement of claim 14 wherein said substrate includes a dielectric layer underlying said target layer.

22. The endpointing arrangement of claim 14 wherein said target layer represents a silicon dioxide-containing layer, said substrate further includes a dielectric layer underlying said target layer.

23. An endpointing arrangement for ascertaining an end of an etch process while etching through a target layer on a substrate in a plasma processing system, comprising:

an electrostatic chuck having a first pole;

a first DC power supply coupled to said first pole for supplying a chucking voltage to said first pole;

a first current monitoring circuit coupled between said first pole and said first DC power supply for monitoring a first current supplied to said first pole, said first current monitoring circuit outputting a first signal indicative of said first current;

an endpoint monitoring circuit coupled to said first current monitoring circuit, said endpoint monitoring circuit receives as a first input said first signal and includes circuitry for analyzing said first signal for a pattern characteristic of said end of said etch process, said endpoint monitoring circuit further including circuitry for outputting an endpoint signal indicative of said end of said etch process upon ascertaining said pattern in said first signal.

24. The endpointing arrangement of claim 23 wherein said electrostatic chuck includes a second pole coupled to said first DC power supply, said endpointing arrangement further comprises:

a second current monitoring circuit coupled between said second pole and said first DC power supply for monitoring a second current supplied to said second pole, said second current monitoring circuit outputting a second signal indicative of said second current, wherein said endpoint monitoring circuit receives as a second input said second signal, said endpoint signal being responsive to both said first signal and said second signal.

25. The endpointing arrangement of claim 23 wherein said electrostatic chuck represents a monopolar electrostatic chuck.

26. An endpointing arrangement for ascertaining an end of an etch process while etching through a target layer on a substrate in a plasma processing system, comprising:

an electrostatic chuck having a first pole and a second pole;

a first DC power supply coupled to said first pole and said second pole for supplying chucking voltages to said first pole and said second pole;

a first current monitoring circuit coupled between said first pole and said first DC power supply for monitoring a first current supplied to said first pole, said first current monitoring circuit outputting a first signal indicative of said first current;

a second current monitoring circuit coupled between said second pole and said first DC power supply for monitoring a second current supplied to said second pole, said second current monitoring circuit outputting a second signal indicative of said second current;

a differential amplifier arrangement coupled to said first current monitoring circuit and said second current monitoring circuit, said differential amplifier arrangement receives said first signal and said second signal as inputs and outputs a differential output signal responsive to both said first signal and said second signal.

an endpoint monitoring circuit coupled to said differential amplifier arrangement, said endpoint monitoring circuit receives as an input said differential output signal and includes circuitry for analyzing said differential output signal for a pattern characteristic of said end of said etch process, said endpoint monitoring circuit further including circuitry for outputting an endpoint signal indicative of said end of said etch process upon ascertaining said pattern in said differential output signal.

27. The endpointing arrangement of claim 26 wherein said electrostatic chuck represents a Johnsen-Rahbek chuck.

28. The endpointing arrangement of claim 26 wherein said substrate includes a conductive layer underlying said target layer.

29. The endpointing arrangement of claim 26 wherein said substrate includes a dielectric layer underlying said target layer.

30. An endpointing arrangement for ascertaining an end of an etch process while etching through a target layer on a substrate in a plasma processing system, comprising:

an electrostatic chuck having a first pole and a second pole;

a first DC power supply coupled to said first pole and said second pole for supplying chucking voltages to said first pole and said second pole;

a first current path coupled in parallel with outputs of said first DC power supply;

a first current monitoring circuit coupled to a node in said first current path for monitoring a first current flowing to said node, said first current monitoring circuit outputting a first signal indicative of said first current; and

an endpoint monitoring circuit coupled to said first current monitoring circuit, said endpoint monitoring circuit receives as an input said first signal and includes circuitry for analyzing said first signal for a pattern characteristic of said end of said etch process, said endpoint monitoring circuit further including circuitry for outputting an endpoint signal indicative of said end of said etch process upon ascertaining said pattern in said first signal.

31. The endpointing arrangement of claim 30 wherein said first current monitoring circuit is coupled in series between said node and ground.

32. The endpointing arrangement of claim 30 further comprising a variable DC power supply, said first current monitoring circuit is coupled in series between said variable DC power supply and said node.

33. An endpointing arrangement for ascertaining an end of an etch process while etching through a target layer on a substrate in a plasma processing system, comprising:

an electrostatic chuck having a first pole;

a first DC power supply coupled to said first pole for supplying a chucking voltage to said first pole;

an endpoint monitoring circuit configured to receive a signal reflecting a potential of said substrate, said endpoint monitoring circuit including circuitry configured to analyze said signal reflecting said potential of said substrate for a pattern characteristic of said end of said etch process, said endpoint monitoring circuit further including circuitry for outputting an endpoint signal indicative of said end of said etch process upon ascertaining said signal reflecting said potential of said substrate.

34. The endpointing arrangement of claim 33 wherein said signal reflecting said potential of said substrate is obtained by a probe in contact with said substrate.