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US 11,768,431 B2Granted
Method of fast surface particle and scratch detection for EUV mask backside
AssigneeTaiwan Semiconductor Manufacturing Company, Ltd.
InventorsChih-Cheng Chen, ShinAn Ku, Ting-Hao Hsu, Hsin-Chang Lee
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Abstract
A method of scanning a substrate and determining scratches of the substrate includes transmitting a converging beam of light that comprises multiple wavelengths to the substrate. Each wavelength of the multiple wavelengths focuses at a different distance in a focus interval around and including a surface of the substrate. The method also includes receiving reflected light from the surface of the substrate and determining a height or depth of the surface of the substrate based on a wavelength of the reflected light having a highest intensity.
Claims20
A method of scanning a substrate, comprising:
- placing the substrate over a stage such that a front surface faces the stage;
- transmitting a converging beam of light that comprises multiple wavelengths to a back surface of the substrate, wherein the multiple wavelengths respectively:
- focus at a first location on the back surface of the substrate and without entering the substrate get reflected from the first location, and
- focus above the first location and without entering the photomask get reflected from the first location of the back surface of the substrate, and
- get reflected from the first location of the back surface of the photomask without being focused and without entering the substrate;
- receiving reflected light bounced back from the back surface of the substrate;
- determining a spectrum of the reflected light intensity versus wavelength;
- determining, based on the spectrum, a first wavelength of the reflected light bounced back from the back surface having a highest intensity, wherein the highest intensity is verified to be a peak intensity if the highest intensity is at least two times greater than an average intensity value of the spectrum, and wherein the converging beam with the first wavelength focuses at the first location;
- and
- determining a height or depth at the first location from the back surface of the substrate directly and only based on the first wavelength of the reflected light as a peak wavelength corresponding to the peak intensity.
7 more elements
A method of scanning a substrate, comprising:
- receiving and reflecting by a beam splitter reflected light bounced back based on an incident light directed at a first location of an open surface of the substrate, the first location including a defect;
- configuring the reflected light to pass through a pinhole;
- detecting the reflected light bounced back from the first location after passing through the pinhole;
- determining a spectrum of the detected reflected light intensity versus wavelength;
- determining a first wavelength of a peak intensity of the spectrum, wherein a highest intensity of the spectrum is verified to be the peak intensity if the highest intensity is at least two times greater than an average intensity value of the spectrum, and wherein the incident light with the first wavelength focuses at the first location;
- and
- determining a height or a depth of the defect measured from the open surface of the substrate directly and only based on the first wavelength as a peak wavelength corresponding to the peak intensity.
4 more elements
A system for scanning a substrate, comprising:
- a main controller;
- a light source coupled to the main controller and configured to transmit a beam of light that comprises multiple wavelengths to the substrate;
- a stage coupled to the main controller and configured to move the substrate;
- an optical system disposed in a light path between the light source and the substrate and coupled to the main controller and configured for focusing the beam of light on an open surface of the substrate;
- and
- a spectrometer to receive a reflected beam of light bounced back by roughness on the open surface of the substrate, wherein the reflected beam of light is directed by the optical system to the spectrometer, the spectrometer is configured for:
- detecting reflected light bounced back from a first location including a defect on the open surface of the substrate;
- determining a spectrum of the detected reflected light intensity versus wavelength;
- determining a first wavelength of a peak intensity of the spectrum, wherein a highest intensity of the spectrum is verified to be the peak intensity if the highest intensity is at least two times greater than an average intensity value of the spectrum;
- and
- determining a height or a depth of the defect measured from the open surface of the substrate directly and only based on the first wavelength as a peak wavelength corresponding to the peak intensity.
8 more elements
Dependencies are inferred from the claim text.