Optical Linewidth Measurements on Photomasks and Wafers

Publisher Summary This chapter discusses the origins of systematic errors in optical linewidth-measurement systems. It discusses the advances in modeling the linewidth-measurement process, including imaging in the optical microscope, a primary linewidth-measurement system in use at the National Bureau of Standards (NBS). The photomultiplier system is referred to as an optical image-scanning system, whereas a semiautomatic TV-microscope system, which determines linewidth from analysis of the video image profile, is referred to as a video image-scanning system. The accuracy of optical imaging methods is dependent upon the characteristics of the optical image formed by the microscope and is affected by diffraction and aberrations in the optical system as well as the partial coherence of the illumination. To determine linewidth to accuracy better than this, one must use an optical threshold that corresponds to the true line edge location. The threshold used for edge detection varies considerably with the type of measuring instrument used. In summary, optical image-scanning linewidth-measurement systems are found less frequently in production environments than image-shearing systems.

[1]  Dennis A. Swyt,et al.  Quantitative Sub-Micrometer Linewidth Determination Using Electron Microscopy , 1981, Advanced Lithography.

[2]  Diana Nyyssonen.  Calibration Of Optical Systems For Linewidth Measurements On Wafers , 1980, Other Conferences.

[3]  D. Nyyssonen.  Optical Linewidth Measurements On Wafers , 1978, Other Conferences.

[4]  E. Wolf,et al.  Electromagnetic diffraction in optical systems, II. Structure of the image field in an aplanatic system , 1959, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[5]  E. Kintner,et al.  Method for the calculation of partially coherent imagery. , 1978, Applied optics.

[6]  Emil Wolf,et al.  Principles of Optics: Contents , 1999 .

[7]  Some experimental measurements of diffraction images in low-resolution microscopy , 1963 .

[8]  Russell D. Young,et al.  Comparison Of Linewidth Measurements On An Sem/Interferometer System And An Optical Linewidth-Measuring Microscope , 1977, Other Conferences.

[9]  A. L. Flamholz,et al.  Automatic Width And Overlay Measurement , 1978, Other Conferences.

[10]  Dennis A. Swyt.  An NBS Physical Standard For The Calibration Of Photomask Linewidth Measuring Systems , 1978, Other Conferences.

[11]  R. Kinzly.  Investigations of the Influence of the Degree of Coherence upon Images of Edge Objects , 1965 .

[12]  D. Nyyssonen.  Linewidth measurement with an optical microscope: the effect of operating conditions on the image profile. , 1977, Applied optics.

[13]  B M Watrasiewicz,et al.  Image formation in microscopy at high numerical aperture. , 1965, Optica acta.

[14]  C. Burckhardt.  Diffraction of a Plane Wave at a Sinusoidally Stratified Dielectric Grating , 1966 .

[15]  L. C. Martin,et al.  The theory of the microscope , 1931 .

[16]  F. Kaspar.  Computation of light transmitted by a thick grating, for application to contact printing , 1974 .

[17]  P. Ciddor.  Some Theoretical and Experimental Studies of a Scanning Photoelectric Microscope , 1971 .

[18]  W. Charman.  Diffraction Images of Circular Objects in High-Resolution Microscopy , 1963 .

[19]  F. Kaspar,et al.  Diffraction by thick, periodically stratified gratings with complex dielectric constant , 1973 .

[20]  Richard E. Swing.  Microdensitometer Optical Performance: Scalar Theory and Experiment , 1976 .

[21]  H. Rottmann.  Photolithography in integrated circuit mask metrology , 1974 .

[22]  J. Dyson,et al.  Precise Measurement by Image-Splitting , 1960 .

[23]  E. C. Teague,et al.  Piezodriven 50‐μm range stage with subnanometer resolution , 1978 .

[24]  D. Nyyssonen.  Optical Linewidth Measurements On Silicon And Iron-Oxide Photomasks , 1977, Other Conferences.

[25]  T. H. James,et al.  The theory of the photographic process. , 1966 .

[26]  J. Goodman.  Introduction to Fourier optics , 1969 .