Method and apparatus for detecting anomalous discharge in plasma processing equipment using weakly-ionized thermal non-equilibrium plasma

• US 6,753,499 B1
• Filed: 11/28/2001
• Issued: 06/22/2004
• Est. Priority Date: 03/28/2000
• Status: Expired due to Fees

• Current Assignee: Japan Science And Technology Corpration, Tokyo Cathode Laboratory Company Limited
• Original Assignee: Japan Science And Technology Corpration, Kumamoto Technopolis Foundation
• Inventors: Takeshita, Masayoshi, Yasaka, Mitsuo
• Primary Examiner(s): Van, Quang T.
• Application Number:
  US09/980,379
• Time in Patent Office: 937 Days
• Field of Search: 219/121.59, 219/121.43, 219/69.16, 219/69.13, 374/117, 324/409, 156/345.28, 204/298.03, 204/298.32, 735/97
• US Class Current: 219/121.59
• CPC Class Codes: B01J 19/088 giving rise to electric discharges for heating purposes H05B7/00; for the production of ozone C01B13/11, H01T19/00
• CPC Class Codes: B01J 19/10 employing sonic or ultrasonic vibrations
• CPC Class Codes: B01J 2219/0894 Processes carried out in the presence of a plasma
• CPC Class Codes: G01H 1/00 Measuring characteristics of vibrations in solids by using direct conduction to the detector G01H9/00, G01H11/00 take precedence
• CPC Class Codes: G01N 2291/011 Velocity or travel time
• CPC Class Codes: G01N 2291/015 Attenuation, scattering
• CPC Class Codes: G01N 2291/0258 Structural degradation, e.g. fatigue of composites, ageing of oils
• CPC Class Codes: G01N 2291/105 two or more emitters, two or more receivers
• CPC Class Codes: G01N 29/0618 synchronised with scanning, e.g. in real-time
• CPC Class Codes: G01N 29/14 using acoustic emission techniques echo of particles G01N29/046; measuring mechanical vibrations or acoustic waves in solids in general G01H1/00
• CPC Class Codes: G01N 29/223 Supports, positioning or alignment in fixed situation mounting transducers per se G10K11/004
• CPC Class Codes: G01N 29/38 by time filtering, e.g. using time gates
• CPC Class Codes: G01N 29/4436 with a reference signal amplitude comparison G01N29/48
• CPC Class Codes: G01N 29/4445 Classification of defects
• CPC Class Codes: H01J 2237/0206 Extinguishing, preventing or controlling unwanted discharges
• 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 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H01J 37/34 operating with cathodic sputtering H01J37/36 takes precedence ; methods of cathodic sputtering C23C14/34
• CPC Class Codes: H05H 1/0093 by acoustic means, e.g. ultrasonic

Abstract

An anomalous arc discharge detection apparatus, including multiplicity of ultrasonic detectors placed at different sections of a plasma processing chamber such that an ultrasonic wave accompanying an anomalous discharge is detected by the ultrasonic detectors at different propagation times or with different delay times. The detected signals are compared with each other on the same time axis to obtain the maximum range of variation of the detected waveforms and the differences in delay time of the respective ultrasonic detectors. From the comparison of the maximum range of variation and the delay times of the ultrasonic detectors, the position of the source point, and the level as well, of the anomalous arc discharge are determined, which can be displayed on a monitor and utilized to issue an alarm if necessary. The position of the anomalous discharge may be obtained by an asymptotic approximation based on recursive calculations of the distances from the source point to the respective ultrasonic detectors using formulas which define the distances in terms of the delay times. This can be done using only four ultrasonic detectors arranged on the wall of the processing chamber. An AE sensor hold case is provided to accommodate an AE sensor. The hold sensor has a lower cover which has one end to be glued onto an appropriate position of the processing chamber, and an upper cover which pushes the AE sensor against the lower cover with an adequate pressure.

Claims

1. An anomalous arc discharge detection apparatus for use with a plasma processing equipment, comprising:

a plasma chamber;

first and second electrodes arranged in said plasma chamber;

a high frequency power source connected to said first electrode for generating a weakly-ionized thermal non-equilibrium plasma in said chamber;

a multiplicity of ultrasonic detection means for detecting ultrasonic waves accompanying an anomalous arc discharge in said plasma processing equipment, and for generating signals indicative of the ultrasonic wave detected;

data processing means for processing waveforms of said ultrasonic wave signals; and

monitor means for displaying a signal indicative of said anomalous discharge.

2. The anomalous arc discharge detection apparatus according to claim 1, wherein

said multiplicity of ultrasonic detection means are mounted on predetermined sections of said plasma processing equipment, and

said data processing means is adapted to determine the location of an anomalous arc discharge based on the propagation time differences of said ultrasonic wave from said source point to the respective multiple ultrasonic detection means.

3. The anomalous arc discharge detection apparatus according to claim 2, wherein said ultrasonic detection means are provided with electrically insulated mounting means for mounting said ultrasonic detection means on said plasma processing equipment in an electrically insulated condition.

4. The anomalous arc discharge detection apparatus according to claim 3, further comprising:

means for determining the level of an anomalous event (AE) generating an ultrasonic wave by processing waveforms of said ultrasonic wave processed by said data processing means; and

means for generating an alarm for issuing an alarm when said level exceeds a given threshold.

5. The anomalous arc discharge detection apparatus according to claim 4, wherein said ultrasonic detection means are provided with electrically insulated mounting means for mounting said ultrasonic detection means on said plasma processing equipment in an electrically insulated condition.

6. The anomalous arc discharge detection apparatus according to claim 2, comprising four ultrasonic detection means, installed on the walls of said plasma processing chamber, for use in the determination of the location of said source point by an asymptotic approximation method.

7. The anomalous arc discharge detection apparatus according to claim 1, further comprising:

means for determining the level of an anomalous event (AE) generating an ultrasonic wave by processing waveforms of said ultrasonic wave processed by said data processing means; and

means for generating and issuing an alarm when said level exceeds a given threshold.

8. The anomalous arc discharge detection apparatus according to claim 7, wherein said ultrasonic detection means are provided with electrically insulated mounting means for mounting said ultrasonic detection means on said plasma processing equipment in an electrically insulated condition.

9. A method of detecting an anomalous arc discharge in a plasma processing equipment, comprising steps of:

mounting four ultrasonic detection means at predetermined positions of said plasma processing equipment; and

locating the source point of said anomalous arc discharge based on the propagation time differences of an ultrasonic wave propagating from said source point to the respective multiple ultrasonic detection means.

10. The method of detecting an anomalous arc discharge according to claim 9, wherein said method uses four ultrasonic detection means, and said step of locating the anomalous arc discharge is an asymptotic approximation of the position of said source point through recursive calculations of the distances between said source point to the respective ultrasonic detection means from said propagation time differences, using known relationships between said distances and said propagation time differences.

11. An acoustic sensor hold case for accommodating an AE sensor, said hold case having one side to be glued onto an exterior of a processing chamber of a plasma processing equipment, said hold case comprising:

a generally slab shaped lower cover having a polished flat inner surface for acoustically coupling said one side with said AE sensor;

a generally cylindrical upper cover for enclosing said AE sensor, wherein

said upper and lower covers are configured to be connected together by screws to firmly secure said AE sensor in position in said hold case so that the input end of said AE sensor is abutted against said inner surface of said lower cover with an adequate pressure, providing acoustic coupling therebetween.

12. The acoustic sensor hold case according to claim 11, further comprising at an inner upper position of said upper cover a resilient member which causes said input end of said AE sensor abuts against a couplant coated on the inner surface of said lower cover with an adequate pressure when said upper and the lower covers are coupled together.

13. The acoustic sensor hold case according to claim 11, wherein only said one end of said AE sensor hold case is covered with an electrically insulative film.

14. The acoustic sensor hold case according to claim 11, further comprising at an inner upper section of said upper case an electrically conductive contact which abuts against said AE sensor, thereby bringing said AE sensor and said upper case to the same electric potential when said upper and lower covers are coupled together.

15. The acoustic sensor hold case according to claim 11, further comprising an acoustically insulative member between the contacting surfaces of said upper and lower covers.

16. The acoustic sensor hold case according to claim 11, wherein said upper cover is provided in either the upper end or the side wall thereof with an opening for passing therethrough an output connector of said AE sensor.

17. The acoustic sensor hold case according to claim 11, further comprising a rubber bushing lying along the inner periphery of said lower cover and extending along the external periphery of said AE sensor such that said bushing keeps said AE sensor not in direct contact with said upper cover when said upper and lower covers are coupled together.

18. An anomalous arc discharge detection apparatus for use with a plasma processing equipment, comprising:

a multiplicity of ultrasonic detection means for detecting ultrasonic waves accompanying an anomalous arc discharge in said plasma processing equipment, and for generating ultrasonic wave signals indicative of the ultrasonic waves detected;

data processing means for processing waveforms of said ultrasonic wave signals;

monitor means for displaying a signal indicative of said anomalous discharge;

electrically insulated mounting means for mounting said ultrasonic detection means on said plasma processing means in an electrically insulated condition.

19. A plasma processing apparatus comprising:

a plasma chamber;

first and second electrodes arranged in said plasma chamber;

a high frequency power source connected to said first electrode for generating a plasma in said chamber;

an ultrasonic detector for detecting ultrasonic waves created by said plasma and for generating ultrasonic signals indicative of the ultrasonic waves detected;

a data processor connected to said ultrasonic detector for processing said ultrasonic wave signals to identify an anomalous arc discharge in said chamber.

20. An apparatus in accordance with claim 19, wherein:

the plasma generated by said high frequency power source and said electrodes in said chamber, is capable of chemical vapor deposition (CVD), ashing, etching, and sputtering of a semiconductor substrate, as well as surface processing thereof.

21. An apparatus in accordance with claim 19, wherein:

the plasma generated by said high frequency power source and said electrodes in said chamber, is for chemical vapor deposition (CVD), ashing, etching, and sputtering of semiconductor substrates, as well as for surface processing thereof.

22. An apparatus in accordance with claim 19, wherein:

said high frequency power source and said electrodes generate a plasma in said chamber used in chemical vapor deposition (CVD), ashing, etching, and sputtering of semiconductor substrates.

23. An apparatus in accordance with claim 19, wherein:

said high frequency power source and said electrodes generate a weakly-ionized thermal non-equilibrium plasma in said chamber.

24. A method for operating a plasma processing apparatus, the method comprising the steps of:

providing a plasma chamber with first and second electrodes arranged in said plasma chamber;

applying high frequency electrical energy to said first electrode to generate a plasma in said chamber;

measuring ultrasonic waves from said chamber created by said plasma;

generating ultrasonic signals indicative of the ultrasonic waves detected;

processing said ultrasonic wave signals to identify an anomalous arc discharge in said chamber.

25. A method in accordance with claim 24, wherein:

said applying of said high frequency electrical energy to said first electrode generates a weakly-ionized thermal non-equilibrium plasma in said chamber.

26. A method in accordance with claim 24, further comprising:

using said plasma for chemical vapor deposition (CVD), ashing, etching, and sputtering of a semiconductor substrate.