High Resolution Scanning Microscope

Abstract: A scanning microscope is disclosed that uses an optical phase shift technique to improve optical resolution by a factor of about two compared to conventional light microscopes, without reducing either the depth of focus or the working distance. The technique reduces, for example, error in the location of edges of features on lithographic masks or wafers. The technique also permits the accurate determination of edges on features that would otherwise be too narrow to be measured. The microscope is useful in any field where optical microscopes are employed, including for example both semiconductor and biological applications. it is also useful in optical data storage applications, where it could be used to increase the amount of data stored per unit area by a factor between about 2 and about 4. In addition, by reducing the numerical aperture of the optical system, the depth of focus may be extended by a factor of four in comparison to a conventional optical system, while maintaining the resolution. The microscopes use standard components to produce high intensity images with large working distances and large depths of focus, without substantial mechanical complexity.