Detection of contaminants on low wavelength masks

A testing method, comprising:

• testing a lithography mask using a combination of Raman techniques and infrared absorption techniques;
• and
• using said testing to detect contaminants on said mask, including contaminants which may be substantially transparent at ultraviolet and visible wavelengths, wherein said testing comprises first testing a known cleaned mask, to determine a background spectrum, and second testing a mask to be tested, and subtracting said background spectrum to obtain a resultant absorption spectrum.

A testing method, comprising:

• testing a lithography mask using a combination of Raman techniques and infrared absorption techniques;
• and
• using said testing to detect contaminants on said mask, including contaminants which may be substantially transparent at ultraviolet and visible wavelengths, wherein said lithography is carried out using 157 nm light, wherein said using comprises determining materials which are transparent at visible and ultraviolet inspection wavelengths, but opaque at 157 nm, wherein said testing comprises detecting scattered light and detecting transmitted light.

A testing method, comprising:

• testing a mask using a first technique which uses a first kind of light to detect interaction with dipole moments of elements on the surface of said mask which comprises finding contaminants which are transparent under one of visible and/or ultraviolet light;
• and
• testing said mask using a second technique simultaneously with the first technique which comprises finding contaminants which are transparent under one of visible and/or ultraviolet light, using a second kind of light different than the first kind of light.

A method, comprising:

• using both of a predetermined first and second measuring techniques to detect spectra of a plurality of different contaminants which are transparent at visible wavelengths, but which are detectable at lower than visible wavelengths to obtain spectra;
• and
• comparing said spectra against said spectra of said plurality of different contaminants.

A tasting system, comprising:

• a light source which produces a Raman laser and an infra red absorption spectroscopy output;
• and
• a detector which subtracts a background spectra from an acquired spectra, and detects a result of both IR absorption and Raman spectroscopy on a sample.

A method comprising:

• inspecting a mask surface using a first technique that does not depend on interacting with any material on the mask surface in a way that depends on the visible light passing characteristics of the material;
• and
• also inspecting said mask surface using a second technique where the surface is visually inspected and testing a mask which is clean, to obtain a spectrum therefrom, and subtracting said spectrum form a final spectrum, to from a spectrum to be analyzed.

A testing method, comprising:

• testing a mask using a first technique which uses a first kind of light to detect interaction with dipole moments of elements on the surface of said mask which comprises funding contaminants which are transparent under one of visible and/or ultraviolet light;
• testing said mask using a second technique simultaneously with the first technique which comprises finding contaminants which are transparent under one of visible and/or ultraviolet light, using a second kind of light different than the first kind of light, and testing a mask which is clean, to obtain a spectrum therefrom, and subtracting said spectrum from a final spectrum, to form a spectrum to be analyzed.