Optical monitoring and control system and method for plasma reactors

• US 20030201162A1
• Filed: 04/18/2003
• Published: 10/30/2003
• Est. Priority Date: 03/30/2000
• Status: Active Grant

• Current Assignee: Tokyo Electron Limited
• Original Assignee: Tokyo Electron Limited
• Inventors: Liu, Lianjun, Johnson, Wayne L.
• Granted Patent: US 7,018,553 B2
• Time in Patent Office: Days
• US Class Current: 204/192.13
• CPC Class Codes: C23C 16/509 using internal electrodes
• CPC Class Codes: C23C 16/52 Controlling or regulating the coating process C23C16/45557, C23C16/279 take precedence
• CPC Class Codes: H01J 37/32082 Radio frequency generated discharge H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence
• CPC Class Codes: H01J 37/32532 Electrodes
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H01J 37/32972 Spectral analysis
• CPC Class Codes: H01J 37/3299 Feedback systems
• CPC Class Codes: H05H 1/0037 by spectrometry

Abstract

A method of adjusting plasma processing of a substrate in a plasma reactor having an electrode assembly. The method includes the steps of positioning the substrate in the plasma reactor, creating a plasma in the plasma reactor, monitoring optical emissions emanating from a plurality of different regions of the plasma in a direction substantially parallel to the surface of the substrate during plasma processing of the substrate, and determining an integrated power spectrum for each of the different plasma regions and comparing each of the integrated power spectra to a predetermined value. One aspect of the method includes utilizing an electrode assembly having a plurality of electrode segments and adjusting RF power delivered to the one or more electrode segments based on differences in the integrated power spectra from the predetermined value. Another aspect of the invention includes altering the flow of gas to different regions of the plasma in response to differences in the integrated power spectra detected by the fiber optic sensors. Several types of novel electrode assemblies suitable for carrying out the method of the invention are also disclosed.

Claims

1. A method for monitoring plasma processing of a substrate with a surface in a plasma reactor having an electrode, the method comprising the steps of:

a) positioning the substrate in the plasma reactor;

b) creating a plasma in the plasma reactor;

c) monitoring optical emissions emanating from a plurality of different regions of the plasma, which regions are spaced apart in a direction parallel to the surface of the substrate during plasma processing of the substrate;

d) determining an integrated power spectrum for each of said different plasma regions and comparing each of said integrated power spectra to a predetermined value.

2. A method for adjusting plasma processing of a substrate comprising carrying out the method according to claim 1, and further including the step of adjusting RF power delivered to each of said electrode segments based on differences in said integrated power spectra from said predetermined value.

3. A method according to claim 2, wherein said step of adjusting RF power is effectuated to alter the characteristics of the plasma in a direction parallel to the substrate.

4. A method according to claim 2, further including the steps of:

a) identifying a magnitude of the power spectrum at predetermined wavelengths corresponding to one or more predetermined gases for each of said different plasma regions;

b) comparing said power spectrum magnitude to a predetermined value for each said sensor; and

c) adjusting power delivered to one or more electrode segments based on differences in said integrated power spectrum magnitude from said predetermined value.

5. A method according to claim 4, further including the step of iterating the above-defined steps until said differences in said integrated power spectrum magnitude are within a predetermined value.

6. A method for adjusting plasma processing of a substrate comprising carrying out the method according to claim 1, and further including the step of adjusting the flow of gas to different regions of the plasma based on differences in said integrated power spectrum magnitude from said predetermined value.

7. A plasma processing system for controlling the processing of a substrate with a plasma, the system comprising:

a) a plasma reactor chamber capable of containing the plasma;

b) a substrate pedestal for supporting the substrate;

c) a segmented electrode assembly arranged within said chamber adjacent said substrate, said assembly having a plurality of electrode segments;

d) a plurality of RF power supplies, each said supply electrically connected to a corresponding one of said electrode segments;

e) a plurality of fiber optic sensors integrated into said electrode assembly, each of said sensors having first and second ends, said second ends arranged to receive light from respective regions of the plasma and transmit said light to said first ends;

f) a sensor array system arranged to receive light from said first ends of said fiber optic sensors and to convert said light into an electronic output signal corresponding to the spectral content of said light as a function of position across the plasma; and

g) a control system in electrical communication with said sensor array system and said plurality of RF power supplies, for controlling the RF power to said electrode segments based on said electronic output signal from said sensor array system.

8. A system according to claim 7, further comprising:

a) a vacuum system electronically connected to said controller and in pneumatic communication with said plasma chamber;

b) an electrode chamber for containing a flowing cooling fluid;

c) a cooling system in fluid communication with said electrode chamber and in electronic communication with said control system; and

d) a gas supply system in pneumatic communication with said electrode assembly and in electronic communication with said control system.

9. An electrode assembly for a plasma reactor system for processing a substrate with a plasma, the electrode comprising:

a) a plurality of substantially planar electrode segments arranged adjacent one another and arranged to be substantially parallel to the substrate when said segments are installed in the reactor system;

b) insulating members, arranged between said electrode segments, each having a sensor bore formed therein; and

c) a plurality of fiber optic sensors each having first and second ends, with said second ends held within respective sensor bores such that said second ends receive light from respective regions of the plasma.

10. An electrode assembly according to claim 9, wherein said second end is recessed in said sensor bore.

20. A plasma processing system for controlling the processing of a substrate with a plasma, the system comprising:

a) a plasma reactor chamber capable of containing the plasma;

b) a substrate pedestal for supporting the substrate;

c) a segmented electrode assembly according to claim 9 arranged within said chamber and facing the substrate;

d) a plurality of RF power supplies, each said supply electrically connected to a corresponding electrode segment;

e) a sensor array system arranged to receive light from said fiber optic sensors and to convert said light into an electronic output signal corresponding to the spectral content of said light; and

f) a control system in electrical communication with said sensor array system and said plurality of RF power supplies, for controlling the power to said electrode segments from said RF power supplies based on said electronic output signal from said sensor array system.

11. An electrode assembly for a plasma reactor system for processing a substrate with a plasma, comprising:

a) a planar electrode body having upper and lower substantially planar surfaces with a plurality of through-bores connecting said upper and lower surfaces, through which gas can flow; and

b) two or more fiber optic support members respectively arranged in corresponding two or more of said bores, each of said members capable of holding a fiber optical sensor within said bore such that the fiber optical sensor receives light from the plasma.

12. An electrode assembly according to claim 11, wherein a portion of each of said two or more bores is threaded and said two or more fiber optic support members include a threaded portion which threadedly engage said two or more bores.

13. An electrode assembly according to claim 11, further including two or more fiber optic sensors held within said two or more of said fiber optic support members

14. An electrode assembly for a plasma reactor system for processing a substrate with a plasma, comprising:

a) a planar electrode body having upper and lower substantially planar surfaces with a plurality of through-bores having an input end at said upper surface and an exit end at said lower surface;

b) two or more transparent windows, each arranged at a respective exit end of a respective one of said bores; and

c) two or more fiber optic sensors each having a first end and a second end, with each of said second ends arranged within a corresponding one of said two or more bores adjacent one of said windows.

15. An electrode assembly according to claim 14, wherein said fiber optic sensor is held fixed within each of said bores by a bonding medium.

16. An electrode assembly according to claim 14, wherein said window has an edge, and further includes:

a) one or more heating elements arranged adjacent said window edge; and

b) a heating unit electronically connected to said elements, for controlling the heating of said window.

17. An electrode assembly for a plasma reactor system for processing a substrate with a plasma, comprising:

a) an electrode body having a lower surface;

b) a plurality of adjustable nozzle units arranged along said electrode body lower surface, for controlling the flow of gas through the electrode assembly, each said nozzle unit having a nozzle plug with a tip, and a nozzle bore passing through said nozzle plug and said tip; and

c) a plurality of fiber optic sensors, each held in one of said nozzle bores such that said fiber optic sensors can receive light from the plasma through said tip.

18. An electrode assembly according to claim 17, further comprising:

a) nozzle adjusting means for adjusting gas flow through said adjustable nozzle units; and

b) control means for controlling said nozzle adjusting means.

19. An electrode assembly according to claim 18, further comprising:

a) a control system in electronic communication with said control means, for controlling the adjustment of said control means in response to light from said fiber optic sensors.

21. A plasma processing system for controlling the processing of a substrate with a plasma, the system comprising:

a) a plasma reactor chamber capable of containing the plasma in an interior region;

b) a substrate pedestal for supporting the substrate;

c) an electrode assembly according to claim 18 arranged within said chamber and facing said substrate;

d) a sensor array system arranged to receive light from said fiber optic sensors and to convert said light into an electronic output signal corresponding to the spectral content of said light; and

e) a control system in electrical communication with said sensor array system and said control means for controlling said nozzle adjusting means, for controlling the flow of gas into said plasma reactor interior region based on an electronic output signal from said sensor array system.

22. A method for improving overall plasma processing uniformity of a wafer in a plasma processing system having a plasma and an electrode assembly with a plurality of electrode segments connected to respective RF power supplies, comprising the steps of:

a) determining a time to an endpoint for each of a plurality of portions of a first wafer using an array of sensors arranged adjacent the plasma and spaced apart in a direction substantially parallel to the wafer;

b) loading a second wafer to be processed into the plasma processing system; and

c) adjusting RF power delivered to each electrode segment by an amount proportional to differences in said endpoint times.

23. A method according to claim 22, wherein said step a) includes the steps of:

i) sensing emission spectra corresponding to different regions of the plasma and subtracting a background signal from each sensor signal;

ii) calculating a power spectrum for each said plasma region;

iii) identifying the magnitude of the power spectrum at predetermined wavelengths corresponding to specific gases present in each said plasma region; and

iv) comparing the magnitude of said power spectrum obtained in said step iii) to a predetermined criterion.