Theoretical and experimental analysis of wire segment holograms for statistical interconnect metrology

Theoretical and experimental results using computer generated wire segment holograms for statistical interconnect metrology are presented. Test structures have been constructed using a process capable of imaging 1-μm features and consist of arrays of wire segments illuminated by a He-Ne Laser. Since the holograms are fabricated at the same time as actual wires on the wafer, the quality of the projected image correlates with the emergence of global feature patterning errors. Specifically, this paper presents data on the effect of varied exposure time on the intensity of the projected image. An initial statistical analysis indicates that the test structures are capable of detecting variations in wire geometry which are approximately 1.0% of the nominal wire width. It is anticipated that significant improvements to this level of sensitivity can be obtained by optimization of the holographic encoding process and test image selection