13 September 1982 Characterization Of The Ultratech Wafer Stepper
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A brief characterization of the Ultratech Model 900 wafer stepper is presented. Excellent control critical dimensions for 1-gum minimum features is accomplished by using a broad spectral bandwidth for exposure which minimizes standing wave effects and by using numerical aperture of 0.315 illuminated with coherence factor of 0.45. Minimal variation in linewidth is seen over 5000A to 8000A poly and metal steps with little evidence of standing wave patterns in the resist profiles. A large depth of focus is obtained with a highly corrected 1:1 lens design which keeps astigmatism and field curvature below 0.5um. The automatic site-by-site alignment system on the Model 900 has proven extremely reliable at all wafer levels with a repeatability better than 0.16um (2 sigma). Lens-to-lens distortion below 0.2um (2 sigma) results from the inherent symmetry in the folded 1:1 design and from careful lens fabrication. A precision lenedistortion test is described with a 2 sigma error below 0.04um and the overlay distortion for the three Ultratech lenses is presented.
© (1982) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Ron Hershel, Ron Hershel, Ron Voison, Ron Voison, } "Characterization Of The Ultratech Wafer Stepper", Proc. SPIE 0334, Optical Microlithography I: Technology for the Mid-1980s, (13 September 1982); doi: 10.1117/12.933559; https://doi.org/10.1117/12.933559

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