Optical diagnostics of semiconductor process using hyperspectral imaging
Disclosed are embodiments of an improved apparatus and system, and associated methods for optically diagnosing a semiconductor manufacturing process. A hyperspectral imaging system is used to acquire spectrally-resolved images of emissions from the plasma, in a plasma processing system. Acquired hyperspectral images may be used to determine the chemical composition of the plasma and the plasma process endpoint. Alternatively, a hyperspectral imaging system is used to acquire spectrally-resolved images of a substrate before, during, or after processing, to determine properties of the substrate or layers and features formed on the substrate, including whether a process endpoint has been reached; or before or after processing, for inspecting the substrate condition.
1. A method for diagnosing a plasma process step in a plasma processing system, comprising:
igniting a plasma in a plasma processing chamber of the plasma processing system;
collecting a plasma optical emission signal through a window mounted in a wall of the plasma processing chamber, and through collecting optics;
directing the plasma optical emission signal from the collecting optics into a wavelength tunable filter for tunably selecting a wavelength of the collected plasma optical emission signal;
detecting the wavelength-filtered plasma optical emission signal using an array detector; and
storing and processing images acquired by the array detector in a controller,
wherein the controller is configured for controlling at least the wavelength tunable filter and the array detector.
2. The method of claim 1 , further comprising:
selectively tuning a passband wavelength of the wavelength tunable filter, across a range or multiple overlapping or non-overlapping ranges of wavelengths in the deep ultraviolet (DUV), ultraviolet (UV), visible (VIS), and infrared (IR) portions of the optical spectrum.
3. The method of claim 2 , further comprising:
forming an image cube, the image cube consisted of a set of images detected by the array detector, each image in the set being acquired at a wavelength defined by an instantaneous passband wavelength to which the wavelength tunable filter is tuned.
4. The method of claim 3 , further comprising:
determining an endpoint of the plasma process step from a sequence of plasma optical emission spectra formed from a sequence of image cubes acquired during the plasma process step.
5. The method of claim 3 , further comprising:
determining a relative concentration of at least one chemical constituent of the plasma from at least one plasma optical emission spectrum formed from at least one image cube.
6. A method for measuring at least one property of at least one layer or structure formed on a substrate disposed in a semiconductor processing system, comprising:
initiating a process step in the semiconductor processing system;
illuminating the substrate with an illumination beam, the portion of the illumination beam reflected and diffracted from the substrate forming a diffracted optical signal;
collecting the diffracted optical signal through a window mounted in a wall of the semiconductor processing system, and through collecting optics;
tunably selecting a wavelength of either the illumination beam or the diffracted optical signal using a wavelength tunable filter disposed in either the illumination beam or the diffracted optical signal, respectively, to form a wavelength-filtered diffracted optical signal;
detecting the wavelength-filtered diffracted optical signal using an array detector; and
storing and processing images acquired by the array detector in a controller,
wherein the controller is configured for controlling at least the wavelength tunable filter and the array detector.
7. The method of claim 6 , further comprising:
selectively tuning a passband wavelength of the wavelength tunable filter, across a range or multiple overlapping or non-overlapping ranges of wavelengths in the deep ultraviolet (DUV), ultraviolet (UV), visible (VIS), and infrared (IR) portions of the optical spectrum.
8. The method of claim 7 , further comprising:
forming an image cube, the image cube consisted of a set of images detected by the array detector, each image in the set being acquired at a wavelength defined by an instantaneous passband wavelength to which the wavelength tunable filter is tuned.
9. The method of claim 8 , further comprising:
determining at least one property of a layer or structure formed on the substrate from at least one diffracted optical spectrum derived from at least one image cube.
10. The method of claim 9 , wherein the at least one property of a layer or structure on the substrate is a profile top critical dimension (CD), a profile bottom critical dimension (CD), a profile middle critical dimension (CD), a profile sidewall angle, a layer thickness, a layer optical property, or a remaining thickness of a layer being etched.
11. The method of claim 8 , further comprising:
determining an endpoint of the process step from a sequence of diffracted optical spectra derived from a sequence of image cubes acquired during the process step.
12. The method of claim 8 , further comprising:
determining a spatial correspondence of locations on the substrate and pixel locations in images of at least one selected image cube; and
deriving at least one diffracted optical spectrum from the at least one selected image cube.
13. The method of claim 12 , wherein the at least one diffracted optical spectrum is derived from a single selected pixel location across all images or a selected subset of images in the at least one selected image cube.
14. The method of claim 12 , wherein the at least one diffracted optical spectrum is derived from at least one selected region of pixel locations across all images or a selected subset of images in the at least one selected image cube.
15. The method of claim 12 , wherein the at least one diffracted optical spectrum is derived from all pixel locations across all images or a selected subset of images in the at least one selected image cube.
16. The method of claim 8 , wherein at least two diffracted optical spectra are derived from a single pixel location across all images or a selected subset of images in at least two image cubes, and wherein the single pixel location is selected such that a rate of change of at least one light intensity between two derived diffracted optical spectra exceeds a pre-selected threshold rate of change of light intensity.
17. The method of claim 8 , wherein at least two diffracted optical spectra are derived from a region of pixel locations across all images or a selected subset of images in at least two image cubes, and wherein the region of pixel locations is selected such that a rate of change of at least one light intensity between two derived diffracted optical spectra exceeds a pre-selected threshold rate of change of light intensity.
18. A method for inspecting a substrate in a substrate inspection system, comprising:
placing the substrate on a stage in the substrate inspection system;
illuminating the substrate with an illumination light source;
collecting an optical signal caused by illuminating the substrate, through collecting optics;
directing the collected optical signal from the collecting optics into a wavelength tunable filter for tunably selecting a wavelength of the collected optical signal;
detecting the wavelength-filtered signal using an array detector; and
storing and processing images acquired by the array detector in a controller,
wherein the controller is configured for controlling at least the wavelength tunable filter and the array detector.
19. The method of claim 18 , further comprising:
selectively tuning a passband wavelength of the wavelength tunable filter, across a range or multiple overlapping or non-overlapping ranges of wavelengths in the deep ultraviolet (DUV), ultraviolet (UV), visible (VIS), and infrared (IR) portions of the optical spectrum.
20. The method of claim 19 , further comprising:
forming an image cube, the image cube consisted of a set of images detected by the array detector, each image in the set being acquired at a wavelength defined by an instantaneous passband wavelength to which the wavelength tunable filter is tuned.
21. The method of claim 20 , further comprising:
determining at least one property of the substrate, or of a layer or structure formed on the substrate from at least one optical spectrum derived from at least one image cube.
22. The method of claim 20 , further comprising:
determining a spatial correspondence of locations on the substrate and pixel locations in images of at least one selected image cube; and
determining at least one optical spectrum from the at least one selected image cube.
23. The method of claim 22 , wherein the at least one optical spectrum is derived from a single selected pixel location across all images or a selected subset of images in the at least one selected image cube.
24. The method of claim 22 , wherein the at least one optical spectrum is derived from at least one selected region of pixel locations across all images or a selected subset of images in the at least one selected image cube.
25. The method of claim 22 , wherein the at least one optical spectrum is derived from all pixel locations across all images or a selected subset of images in the at least one selected image cube.