The vortex mask: making 80-nm contacts with a twist!

Marc David Levenson; Grace Dai; Takeaki Ebihara

doi:10.1117/12.467406

27 December 2002 Vortex Mask: Making 80nm contacts with a twist!

Marc David Levenson, Grace Dai, Takeaki Ebihara

Proceedings Volume 4889, 22nd Annual BACUS Symposium on Photomask Technology; (2002) https://doi.org/10.1117/12.467406
Event: Photomask Technology 2002, 2002, Monterey, CA, United States

Abstract

An optical vortex has a phase that spirals like a corkscrew. Since any nonzero optical amplitude must have a well-defined phase, the axis of a vortex (where the phase is undefined) is always dark. Printed in negative resist, lowest order vortices would produce contact holes with 0.21<0.5, roughly 80-200nm diameter, with 248nm exposure and NA=0.63. Arrays of vortices with k_pitch>0.6 can be produced using a chromeless phase-edge mask composed of rectangles with phases of 0°, 90°, 180° and 270°. EMF and Kirchhoff-approximation simulations reveal that the image quality of the dark spots is excellent, and predict a process window with 15% exposure latitude and 400nm DOF for 80nm diameter spots on pitches ≥250nm at σ=0.15. EMF simulations predict that the 0-270° phase step will not be excessively dark if the quartz wall is vertical. Chrome spots at the centers can control the diameters which otherwise are set by the parameters of the imaging system and exposure dose. Unwanted vortices can be erased from the image by exposing with a second, more conventional, trim mask. This method would be superior to the other ways of producing sub-wavelength vias, but successful implementation requires the development of appropriate negative-tone resist processes.

Citation Download Citation

Marc David Levenson, Grace Dai, and Takeaki Ebihara "Vortex Mask: Making 80nm contacts with a twist!", Proc. SPIE 4889, 22nd Annual BACUS Symposium on Photomask Technology, (27 December 2002); https://doi.org/10.1117/12.467406

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