Purge gas flow control for high-precision film measurements using ellipsometry and reflectometry
First Claim
1. An optical method for measuring characteristics of a sample using a broadband metrology tool in a purge gas flow environment, comprising:
- purging a beam path for the metrology tool with purge gas at a first flow rate;
illuminating a surface of the sample by a beam of source radiation, the beam comprising at least one wavelength component in a vacuum ultraviolet (VUV) range and/or at least one wavelength component in a ultraviolet-visible (UV-Vis) range; and
adjusting a flow rate of a purge gas between the first flow rate for metrology measurements made when the source radiation is in the VUV range and a second flow rate for metrology measurements made when the source radiation is in the UV-Vis range.
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Abstract
An optical method and system for measuring characteristics of a sample using a broadband metrology tool in a purge gas flow environment are disclosed. In the method a beam path for the metrology tool is purged with purge gas at a first flow rate. A surface of the sample is illuminated by a beam of source radiation having at least one wavelength component in a vacuum ultraviolet (VUV) range and/or at least one wavelength component in an ultraviolet-visible (UV-Vis) range. A flow rate of a purge gas is adjusted between the first flow rate for metrology measurements made when the source radiation is in the VUV spectral region and a second flow rate for metrology measurements made when the source radiation is in the UV-Vis spectral region. The system includes a light source, illumination optics, collection optics, detector, a purge gas source and a controller. The purge gas source is configured to supply a flow of purge gas to a beam path in the light source and/or illumination optics and/or sample and/or collection optics and/or detector. The controller is configured to control a flow rate of the purged gas flow in response to an output signal from the detector.
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Citations
20 Claims
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1. An optical method for measuring characteristics of a sample using a broadband metrology tool in a purge gas flow environment, comprising:
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purging a beam path for the metrology tool with purge gas at a first flow rate; illuminating a surface of the sample by a beam of source radiation, the beam comprising at least one wavelength component in a vacuum ultraviolet (VUV) range and/or at least one wavelength component in a ultraviolet-visible (UV-Vis) range; and adjusting a flow rate of a purge gas between the first flow rate for metrology measurements made when the source radiation is in the VUV range and a second flow rate for metrology measurements made when the source radiation is in the UV-Vis range. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An optical system for measuring characteristics of a samples using a broadband metrology tool in a purged gas flow environment, comprising:
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a light source configured to supply a beam of source radiation having at least one wavelength component in a VUV range and/or at least one wavelength component in a UV-Vis range; illumination optics adapted to illuminate a surface of the sample with the beam source of radiation; collection optics collecting signal radiation generated by interaction of the beam source radiation with the surface of the sample; a detector adapted to provide at least one output signal in response to the signal radiation collected from the collection optics, wherein the signal is related to a property of the surface of the sample; a purge gas source configured to supply a flow of purge gas to a beam path in the light source and/or illumination optics and/or sample and/or collection optics and/or detector; and a controller operably coupled to the detector and the purge gas source, wherein the controller is configured to control a flow rate of the purged gas flow in response to the output signal from the detector by adjusting a flow rate of the purge gas between a first flow rate for metrology measurements made when the source radiation is in the VUV range and a second flow rate for metrology measurements made when the source radiation is in the UV-Vis range. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification