In-situ film thickness measurement using spectral interference at grazing incidence

• US 20030090676A1
• Filed: 09/24/2001
• Published: 05/15/2003
• Est. Priority Date: 09/24/2001
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Goebel, Andreas, Raoux, Sebastien, Sarfaty, Moshe
• Granted Patent: US 6,888,639 B2
• Time in Patent Office: Days
• US Class Current: 356/504
• CPC Class Codes: G01B 11/0675 using interferometry
• CPC Class Codes: G01N 21/8422 Investigating thin films, e.g. matrix isolation method
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: H01L 22/12 for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions electrical measurement of diffusions H01L22/14
• 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

A method and system using spectral interference of light from plasma emissions collected at near grazing incidence to in-situ monitor and control the film thickness of a non-opaque film. Embodiments of this invention are particularly useful to all substrate processing chambers equipped to form an in-situ plasma within the chamber and which are used to deposit or etch non-opaque films. One embodiment of the method of the present invention forms a plasma within a substrate processing chamber to deposit a non-opaque film on a wafer substrate within the chamber. During the plasma deposition process, a plurality of wavelengths of radiation including those reflected from the top and bottom layer of the film being deposited upon a wafer surface are collected through an existing viewport, and conveyed to a spectrometer for measurements via an optical fiber attached near this viewport. These measurements are analyzed to determine the film'"'"'s thickness. An alternate embodiment of the method of the present invention uses an interference filter to confine the spectral composition of the plasma emissions to an emission at a narrow wavelength interval and a photodiode to detect the intensity of the emission.

Claims

1. A method for in-situ measurement of the film thickness of a non-opaque film on a substrate, said method comprising:

forming a plasma to deposit or etch said film;

collecting optical emissions, including those emitted from said plasma and reflected from said film on said substrate surface at grazing incidence;

determining a rate of interference within the reflected light; and

using said rate of interference to determine said film thickness.

2. The method of claim 1 wherein grazing incidence is an angle of at least 80 and less than 90 degrees as measured between an observation direction and a direction normal to said substrate surface.

3. The method of claim 1 further comprising using ex-situ measurements to obtain calibration data and performing said analyzing with said calibration data.

4. The method of claim 1 further comprising using an interference filter to confine the spectral composition of said optical emissions to an emission at a narrow spectral interval and a photodiode to detect said emission.

5. The method of claim 1 further comprising using the full spectral composition of said optical emissions and analyzing said interference fringes at a plurality of wavelengths.

6. The method of claim 1 wherein said rate of interference is correlated with a deposition rate.

7. A substrate processing system, said system comprising:

a chamber having a chamber wall and a substrate support; and

a window positioned in an opening of said chamber wall such that an angle between a center of said window and said substrate support is at least 80 and less than 90 degrees inclusive as measured with respect to a normal to said substrate support, said system configured to in-situ measure a film thickness of a non-opaque film being processed in said chamber, where being processed is being deposited or etched.

8. The substrate processing system of claim 7 further comprising:

an optical fiber, configured to be coupled with said window and configured to convey plasma emissions generated from a plasma source within said chamber;

a light detection device to detect a rate of interference caused by the interference of said plasma emissions reflected from a top and a bottom of a substrate surface placed within said chamber; and

a data analysis device configured to analyze said rate of interference to provide wafer state data, said system configured to in-situ measure a film thickness of a non-opaque film being processed in said chamber, where being processed is being deposited or etched.

9. A substrate processing system, said system comprising:

a chamber having a chamber wall and a substrate support;

a window positioned in an opening of said chamber wall such that an angle between a center of said window and said substrate support is at least 80 and less than 90 degrees inclusive as measured with respect to a normal to said substrate support;

an optical fiber configured to be coupled to said window and configured to convey plasma emissions generated from a plasma source within said chamber;

a light detection device to detect a rate of interference caused by the interference of said plasma emissions reflected from a top and a bottom of a substrate surface placed within said chamber; and

a data analysis device configured to analyze said rate of interference to provide wafer state data, said system configured to in-situ measure a film thickness of a non-opaque film being processed in said chamber, where being processed is being deposited or etched.

10. The system of claim 9 wherein said light detection device comprises an interference filter to confine the spectral composition of said optical emissions to an emission at a narrow wavelength band and a photodiode to detect said emission.

11. The system of claim 9 wherein said light detection device comprises a spectrometer to analyze the full spectral composition of said optical emissions at a plurality of wavelengths.

12. The system of claim 9 wherein the angle of incidence of said reflected optical emissions, measured between the observation direction and the direction normal to said substrate, is in a range of at least 80 and less than 90 degrees inclusive.

13. The system of claim 9 wherein said window is one of (a) a sapphire window or (b) a quartz window, and wherein said window is vertically mounted with its bottom edge placed above said substrate surface.

14. The system of claim 9 wherein said window is one of (a) a sapphire window or (b) a quartz window, and wherein said window is vertically mounted with its bottom edge placed above said substrate surface and its top edge placed below an upper electrode of said chamber.

15. The system of claim 9 wherein said optical fiber is mounted perpendicular to said window, and where no optical lens devices are placed between said window and said optical glass fiber.

16. The system of claim 9 wherein said wafer state data comprises fringe frequency, film thickness per fringe, total film thickness, deposition rate, and etch rate.

17. A method for in-situ control of the deposition of a non-opaque film on a substrate, said method comprising:

forming a plasma;

depositing said film using said plasma;

counting periodic oscillations in plasma emissions caused by the interference of plasma emissions reflected from a top and a bottom of said film; and

stopping the deposition of said film once a predetermined oscillation count is reached.

18. A method for in-situ control of the etching of a non-opaque film on a substrate, said method comprising:

forming a plasma;

etching said film using said plasma;

counting periodic oscillations in plasma emissions caused by the interference of plasma emissions reflected from a top and a bottom of said film; and

stopping the etching of said film once a predetermined oscillation count is reached.