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28 May 2004 Advances in vortex via fabrication
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Vortex masks composed of rectangles with nominal phases of 0°, 90°, 180° and 270° have been shown to print sub-100nm vias and via arrays when projected into negative resist using 248nm light. Arrays with pitches down to 210nm and CDs as small as 64nm have been reported. While promising, 248nm vortex via images showed some anomalies: The developed contacts were somewhat elliptical, with four different repeating via shapes. The common depth of focus for these four classes of via was limited by their different behaviors through focus. Phase edges in isolated vortex pair structures tended to print, also limiting the useful DOF. These issues can be ameliorated by employing 193nm illumination and a new negative-tone resist. Smaller NAs and higher coherence extend the common depth of focus and larger NAs can be used to print even more tightly spaced patterns. Advanced optical proximity correction techniques can also be applied to reduce the via ellipticity and placement error, and a more optimal choice of geometrical phase depth reduces pattern variability. Further developments and incremental improvements in vortex via design and processing may make it the method of choice for via patterning at the 45nm node.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Marc David Levenson, Takeaki Joe Ebihara, Michael Reilly, George Barclay, Vaishali Vorha, Carolyne Stafford, Martin E. Mastovich, Yasutaka Morikawa, and Naoya Hayashi "Advances in vortex via fabrication", Proc. SPIE 5377, Optical Microlithography XVII, (28 May 2004);

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