Method for monitoring process endpoints in a plasma chamber and a process monitoring arrangement in a plasma chamber

• US 5,846,373 A
• Filed: 06/28/1996
• Issued: 12/08/1998
• Est. Priority Date: 06/28/1996
• Status: Expired due to Term

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Mundt, Randall S., Harshbarger, William, Pirkle, David R.
• Primary Examiner(s): Knode, Marian C.
• Assistant Examiner(s): Brumback, Brenda G.
• Application Number:
  US08/671,918
• Time in Patent Office: 893 Days
• Field of Search: 216/84, 156/345
• US Class Current: 156/345.25
• CPC Class Codes: C23C 16/4405 Cleaning of reactor or parts inside the reactor by using reactive gases
• CPC Class Codes: C23C 16/50 using electric discharges generation and control of plasma in discharge tubes for surface treatment H01J37/32, H01J37/34
• CPC Class Codes: C23C 16/52 Controlling or regulating the coating process C23C16/45557, C23C16/279 take precedence
• CPC Class Codes: G01B 11/0683 measurement during deposition or removal of the layer
• 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: H01J 37/32972 Spectral analysis

Abstract

Thin film deposition process endpoints and in situ-clean process endpoints are monitored using a single light filter and photodetector arrangement. The light filter has a peak transmission proximate a characteristic wavelength of the deposition plasma, such as Si, and one of the plurality of reaction products, such as NO, in the plasma chamber during in-situ cleaning. Emissions passing through the filter are converted to voltage measurements by a photodetector. In deposition endpoint monitoring, emission intensity of the Si emissions reflected off the surface of the substrate oscillate as deposition thickness increases, with each oscillation corresponding to a definite increase in thickness of the film. The endpoint of the deposition is reached when the number of oscillations in signal intensity versus time corresponds to a desired film thickness. Alternatively, a deposition rate for the film is calculated from the oscillation frequency of emissions reflected off the substrate. Endpoint occurs when the integrated deposition rate corresponds to the desired film thickness. In in-situ clean endpoint monitoring, the endpoint of the process is reached when emission intensity of the particular reaction product decreases to a substantially steady state value, meaning that the reaction is complete.

Claims

1. A process monitoring arrangement in a plasma chamber for deposition of silicon dioxide on a semiconductor substrate, comprising:

a plasma chamber having a wall and at least one inlet supplying silicon and oxygen reactants, the plasma chamber including plasma generating equipment for generating, during an SiO₂ deposition process, a silicon and oxygen containing deposition plasma;

a window mounted in the wall of the plasma chamber;

a wavelength selective element in optical communication with the window, the wavelength selective element having a peak transmission proximate a characteristic wavelength of the deposition plasma;

a photodetector for monitoring emission intensity of light emitted by the deposition plasma during the SiO₂ deposition process, the light being reflected off the semiconductor substrate and passed through the wavelength selective element prior to being received by the photodetector; and

a computer monitoring voltage output from the photodetector to determine endpoints of the SiO₂ deposition process.

2. The process monitoring arrangement as set forth in claim 1, wherein the wavelength selective element includes a light filter.

3. The process monitoring arrangement as set forth in claim 2, wherein the light filter includes an interference filter and peak transmission of the wavelength selective element is in a range of 236 to 264 nm.

4. The process monitoring arrangement as set forth in claim 1, wherein the wavelength selective element includes a spectrometer.

5. The process monitoring arrangement as set forth in claim 1, wherein the wavelength selective element includes diffraction gratings.

6. The process monitoring arrangement as set forth in claim 1, wherein the wavelength selective element includes a prism.

7. The process monitoring arrangement as set forth in claim 1, wherein the wavelength selective element comprises an interference filter and the computer determines the thickness of the SiO₂ layer by counting a number of oscillations in emission intensity of Si reflected off the semiconductor substrate.

8. The process monitoring arrangement as set forth in claim 1, wherein the wavelength selective element comprises an interference filter, the computer determines the thickness of a silicon dioxide layer deposited on the semiconductor substrate by determining a deposition rate of the deposited silicon dioxide layer as a function of the voltage oscillation frequency of the plasma emission reflected off the semiconductor substrate, and the computer calculates an accumulated thickness of the silicon dioxide layer as a function of the deposition rate.

9. The process monitoring arrangement as set forth in claim 1, wherein the plasma chamber includes a supply of fluorine for an in-situ chamber cleaning process in which a fluorine containing etching plasma reacts with silicon dioxide in the plasma chamber and forms a plurality of reaction products, the peak transmission of the wavelength selective element is proximate a characteristic wavelength of the deposition plasma and one of the plurality of reaction products, the photodetector monitors emission intensity of one of the reaction products during an in-situ chamber cleaning process, and the computer monitors voltage output from the photodetector and determines endpoints of the in-situ chamber cleaning process.

10. The process monitoring arrangement as set forth in claim 9, wherein the at least one of the reaction products is NO.

11. A process monitoring arrangement in a plasma chamber, comprising:

a plasma chamber having a wall, the plasma chamber including plasma generating equipment for generating, during a deposition process, a first plasma for generating a first material layer and, during an in-situ clean process, a second plasma, the second plasma reacting with first material layer deposits in the plasma chamber to form a plurality of reaction products;

a window mounted in the wall of the plasma chamber;

a wavelength selective device in optical communication with the window, the wavelength selective device having a peak transmission proximate both a characteristic wavelength of the first plasma and one of the plurality of reaction products;

a photodetector for monitoring emission intensity of light emitted by the first plasma during the deposition of the first material layer on a semiconductor substrate and the one of the reaction products during the in-situ clean process; and

a computer monitoring voltage output from the photodetector to determine endpoints of the first material layer deposition process and the in-situ clean process.

12. The process monitoring arrangement as set forth in claim 11, wherein the wavelength selective element includes a light filter.

13. The process monitoring arrangement as set forth in claim 12, wherein the light filter includes an interference filter and peak transmission of the wavelength selective element is in a range of 236 to 264 nm.

14. The process monitoring arrangement as set forth in claim 11, wherein the wavelength selective element includes a spectrometer.

15. The process monitoring arrangement as set forth in claim 11, wherein the wavelength selective element includes diffraction gratings.

16. The process monitoring arrangement as set forth in claim 11, wherein the wavelength selective element includes a prism.

17. The process monitoring arrangement as set forth in claim 11, wherein the wavelength selective element comprises an interference filter and the computer determines the thickness of the SiO₂ layer by counting a number of oscillations in emission intensity of Si reflected off the semiconductor substrate.

18. The process monitoring arrangement as set forth in claim 11, wherein the wavelength selective element comprises an interference filter, the computer determines the thickness of a silicon dioxide layer deposited on the semiconductor substrate by determining a deposition rate of the deposited silicon dioxide as a function of the voltage oscillation frequency of the plasma emission reflected off the semiconductor substrate, and the computer calculates an accumulated thickness as a function of the deposition rate.