Method and apparatus for detecting the endpoint of a chamber cleaning

• US 6,534,007 B1
• Filed: 08/01/1997
• Issued: 03/18/2003
• Est. Priority Date: 08/01/1997
• Status: Expired due to Fees

• Current Assignee: Applied Komatsu Technology, Inc., Applied Materials Incorporated
• Original Assignee: Applied Komatsu Technology, Inc.
• Inventors: Blonigan, Wendell T., Gardner, James T.
• Primary Examiner(s): Markoff, Alexander
• Application Number:
  US08/904,432
• Time in Patent Office: 2,055 Days
• Field of Search: 134/1.1, 134/1.2, 134/1.3, 134/18, 134/22.1, 134/1, 422/62, 438/905, 438/7, 438/8, 438/9, 438/16, 156/345.25, 250/528.1, 216/59, 216/60
• US Class Current: 422/62
• CPC Class Codes: C23C 14/564 Means for minimising impurities in the coating chamber such as dust, moisture, residual gases
• CPC Class Codes: C23C 16/4405 Cleaning of reactor or parts inside the reactor by using reactive gases
• CPC Class Codes: H01J 37/32862 In situ cleaning of vessels and/or internal parts
• CPC Class Codes: H01J 37/32963 End-point detection
• CPC Class Codes: Y10S 438/905 Cleaning of reaction chamber

Abstract

A method and apparatus for cleaning a CVD chamber including optoelectronic detection of the completion or endpoint of the cleaning procedure once a ratio of emission lines reaches a threshold value. The method comprises the steps of: providing a plasma of a cleaning gas into the chamber and creating a plasma from the cleaning gas. The intensity of emission lines of the cleaning gas and of at least one background gas in the chamber are monitored. A ratio of the intensity of the cleaning gas emission line to the intensity of the background gas emission line is determined and monitored as a function of time. The determined ratio is compared to a preset threshold calibration value. The flow of gas is controlled based on the comparing step. The apparatus includes a cleaning gas supply with a valved inlet providing an entrance to the interior of the chamber for passing cleaning gas to the interior of the chamber. A detector having an optical input is disposed for sensing the electromagnetic radiation. The detector has a first channel for detecting a relative intensity of an emission line corresponding to the cleaning gas and a second channel for detecting a relative intensity of the emission line corresponding to the background gases. Software or circuitry is employed to determine a normalized signal using a signal from the first channel and a signal from the second channel. The value of the normalized signal is substantially invariant with respect to simultaneous corresponding changes in the intensity of the signal measured by the first channel and the intensity of the signal measured by the second channel.

Claims

1. Apparatus for detecting the endpoint of a plasma cleaning process for removing a residue deposited on an interior surface of a chemical vapor deposition chamber, wherein said residue is deposited on said surface by a chemical vapor deposition process performed in the deposition chamber before the cleaning process is performed, comprising:

a chemical vapor deposition vacuum chamber having a chamber wall enclosing an interior of the chamber, wherein the chamber wall includes a surface exposed to said interior on which said residue deposits during said chemical vapor deposition process;

a plasma source connected to the chamber so as to maintain a plasma in the interior of the vacuum chamber, wherein the plasma includes one or more reactive species that react with said residue on the chamber wall;

a first photodetector that produces a first electrical signal responsive to light emissions only at a wavelength substantially equal to a characteristic emission wavelength of one of said reactive species, the first photodetector being optically coupled to receive light from the interior of the vacuum chamber;

a second photodetector that produces a second electrical signal responsive to light emissions over a wider range of wavelengths than the first photodetector, wherein the second photodetector is optically coupled to receive light from the interior of the vacuum chamber, and wherein said wider range of wavelengths includes light emissions of at least one background gas in the vacuum chamber; and

a circuit, connected to receive the first and second electrical signals, for signalling the occurrence of an endpoint only after the ratio of the first electrical signal to the second electrical signal exceeds a threshold.

2. Apparatus according to claim 1, wherein the circuit signals the occurrence of an endpoint only after the ratio of the first electrical signal to the second electrical signal has remained above said threshold throughout a predetermined period of time.

3. Apparatus according to claim 1, further comprising:

a narrow band optical filter that transmits light only at said characteristic emission wavelength, the narrow band optical filter being optically interposed between the first photodetector and the interior of the vacuum chamber; and

a broad band optical filter that transmits light over said wider range of wavelengths, the broad band optical filter being optically interposed between the second photodetector and the interior of the vacuum chamber.

4. Apparatus according to claim 1, wherein the plasma is formed from a gas mixture that includes a fluorine-containing gas.

5. Apparatus according to claim 4, wherein the fluorine-containing gas is NF₃.

6. Apparatus according to claim 4, wherein the characteristic emission wavelength to which the first photodetector responds is 704 nm.

7. Apparatus according to claim 1, wherein:

said one or more reactive species collectively are effective to remove said residue from the chamber wall.

8. Apparatus according to claim 1, wherein the plasma source is a remote plasma source comprising:

a remote plasma chamber connected to supply a plasma to the chemical vapor deposition vacuum chamber.

9. Apparatus according to claim 1, wherein the plasma source is an in-situ plasma source coupled to the chemical vapor deposition vacuum chamber so as to form a plasma in-situ within the chamber.

10. Apparatus according to claim 1, wherein said range of wavelengths to which the second electrical signal is responsive includes light emissions of said at least one background gas at a plurality of different wavelengths.

11. Apparatus according to claim 1, wherein said range of wavelengths to which the second electrical signal is responsive includes light emissions of a plurality of background gases in the vacuum chamber.

12. Apparatus for detecting the endpoint of a plasma cleaning process for removing a residue deposited on an interior surface of a chemical vapor deposition chamber, wherein said residue is deposited on said surface by a chemical vapor deposition process performed in the deposition chamber before the cleaning process is performed, comprising:

a chemical vapor deposition vacuum chamber having a chamber wall enclosing an interior of the chamber, wherein the chamber wall includes a surface exposed to said interior on which said residue deposits during said chemical vapor deposition process;

a plasma source connected to the chamber so as to maintain a plasma in the interior of the vacuum chamber, wherein the plasma includes one or more reactive species that react with said residue on the chamber wall;

a narrow band optical filter that transmits light only at a characteristic emission wavelength of one of said reactive species;

a first photodetector that produces a first electrical signal, the first photodetector being optically coupled through said narrow band optical filter to receive light from the interior of the vacuum chamber;

a neutral density optical filter;

a second photodetector that produces a second electrical signal, the second photodetector being optically coupled through said neutral density filter to receive light from the interior of the vacuum chamber; and

a circuit, connected to receive the first and second electrical signals, for signalling the occurrence of an endpoint only after the ratio of the first electrical signal to the second electrical signal exceeds a threshold.

13. Apparatus according to claim 12, wherein the plasma source is a remote plasma source comprising:

a remote plasma chamber connected to supply a plasma to the chemical vapor deposition vacuum chamber.

14. Apparatus according to claim 12, wherein the plasma source is an in-situ plasma source coupled to the chemical vapor deposition vacuum chamber so as to form a plasma in-situ within the chamber.

15. Apparatus for detecting the endpoint of a plasma cleaning process for removing a residue deposited on an interior surface of a chemical vapor deposition chamber, wherein said residue is deposited on said surface by a chemical vapor deposition process performed in the deposition chamber before the cleaning process is performed, comprising:

a chemical vapor deposition vacuum chamber having a chamber wall enclosing an interior of the chamber, wherein the chamber wall includes a surface exposed to said interior on which said residue deposits during said chemical vapor deposition process;

an in-situ plasma source coupled to the vacuum chamber so as to form a plasma within the interior of the vacuum chamber, wherein the plasma includes one or more reactive species that react with said residue on the chamber wall;

a first photodetector that produces a first electrical signal responsive to light emissions only at a wavelength substantially equal to a characteristic emission wavelength of one of said reactive species, the first photodetector being optically coupled to receive light from the interior of the vacuum chamber;

a second photodetector that produces a second electrical signal responsive to light emissions over a wider range of wavelengths than the first photodetector, wherein the second photodetector is optically coupled to receive light from the interior of the vacuum chamber, and wherein said wider

range of wavelengths includes light emissions of at least one background gas in the vacuum chamber; and

a circuit, connected to receive the first and second electrical signals, for signalling the occurrence of an endpoint only after the ratio of the first electrical signal to the second electrical signal exceeds a threshold.