Apparatus and a method for high numerical aperture microscopic examination of materials

A Raman spectrometer useful in examining a sample semiconductor wafer having a flat back surface and having an index of refraction greater than unity, said Raman spectrometer comprising:

• a plano-convex lens having an index of refraction approximately equal to the index of refraction of the semiconductor wafer;
• means for optically coupling the plano-convex lens to the back surface of the sample semiconductor wafer;
• illuminating means for generating light energy which is substantially coherent and monochromatic and for coupling the light energy into the semiconductor wafer at a predetermined angle of incidence and a predetermined position with respect to the plano-convex lens wherein reflected rays at approximately 90.degree. to the specularly reflected wave in the semiconductor wafer are coupled through the optical coupling means and through the plano-convex lens;
• spatial filtering means for passing the rays reflected at 90.degree. to the incident wave in the semiconductor wafer, provided by the plano-convex lens to the relative exclusion of other rays provided by the plano-convex lens;
• and
• spectrometer means for generating a Raman spectrogram from the rays passed by the spatial filtering means.

An absorption spectrometer useful in examining a sample semiconductor wafer having a flat back surface and having an index of refraction greater than unity, said absorption spectrometer comprising:

• a plano-convex lens having an index of refraction approximately equal to the index of refraction of the semiconductor wafer;
• means for optically coupling the plano-convex lens to the back surface of the sample semiconductor wafer;
• first illuminating means for generating light signals which are substantially monochromatic and for modulating said monochromatic light signals with a modulating signal having a frequency substantially less than the frequency of said monochromatic light signals and for illuminating said semiconductor wafer with said light signals;
• second illuminating means for generating a further light signal which is substantially monochromatic and coherent
• means for coupling said further light signal into said semiconductor wafer through said plano-convex lens;
• means for changing the focal point of the further light signal in the semiconductor wafer
• imaging means for detecting an image of the further light signal substantially at the focal point of the further light signal in the semiconductor wafer;
• and
• means for detecting absorption of the light signals provided by said first illuminating means by detecting modulation, by said modulating signal, of the further light signal in the image formed by said imaging means.