Accession Number : ADA191895

Title :   A Practical Interferometric Technique for Mask/Wafer Alignment During Proximity Printing,

Corporate Author : NAVAL OCEAN SYSTEMS CENTER SAN DIEGO CA

Personal Author(s) : Bartelt, J L ; Olney, R D ; Lagnado, I

PDF Url : ADA191895

Report Date : May 1987

Pagination or Media Count : 2

Abstract : A new automated technique for sensing translational/rotational mask-to-wafer alignment will be presented that is useful with proximity printing processes such as masked ion beam or x-ray lithography. The technique is based on computer interpretation of fringe patterns created by laser beams diffracted from unique grating structures on both the mask and the wafer. It requires no moving parts and features a simple optical configuration that uses a dielectric cube beamsplitter to the novel grating structure and fringe analysis provides a capture range in excess of 20 um. Additional key features of the technique are that it is insensitive to variations in the gap between mask and wafer and that its performance does not degrade with changes in surface reflectivity or topography as device wafers are processed. A single channel of the grating alignment technique has been implemented and tested in a laboratory bench fixture. The required mathematics, computer code, and experimental results will be discussed.

Descriptors :   *INTERFEROMETRY, *MASKS, *WAFERS, ALIGNMENT, AUTOMATION, CHANNELS, COMPUTER PROGRAMS, CONFIGURATIONS, GRATINGS(SPECTRA), ION BEAMS, LASER BEAMS, LITHOGRAPHY, MECHANICAL COMPONENTS, OPTICAL PROPERTIES, PATTERNS, REFLECTIVITY, STRUCTURES, SURFACES, TOPOGRAPHY, X RAYS, INTEGRATED CIRCUITS

Subject Categories : Electrical and Electronic Equipment

Distribution Statement : APPROVED FOR PUBLIC RELEASE