Vortex Mask: Making 80nm contacts with a twist!

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 undefmed) is always dark. Printed in negative resist, lowest order vortices would produce contact holes with O.2<k1<O.5, roughly 80-200nm diameter, with 248nm exposure and NAO.63. Arrays of vortices with kPjth>O.6 can be produced using a chromeless phase-edge mask composed of rectangles with phases of O, 900, 1 80° 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 8Onm diameter spots on pitches 250nm at =0.15. EMF simulations predict that the 0-270° phase step will not be excessively dark ifthe 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.

X-ray vortex beams: A theoretical analysis

“…This opens up a whole new parameter space of possible application for optical vortices. Possible x-ray applications include using the dark vortex core to mask a bright source, as in an astronomical x-ray source [23], or in a synchrotron-based small angle scattering experiment or, as a component in an x-ray phase-shifting mask, where the central zero in the vortex intensity pattern defines a small dot in the negative photoresist that creates a contact that can be used to connect layers [24]. Another idea might be to take advantage of elemental characteristic absorption energies to allow the selective transfer of orbital angular momentum thus allowing the manipulation of components of a structure that contain elements matching the tuned beam energy -for instance microfabricated objects carrying certain metal compounds may be moved while leaving their surroundings unaffected.…”

Alternating phase shift mask architecture scalability, implementations, and applications for 90-nm and 65-nm technology nodes and beyond

“…The double phase edge approach can also be realized in a diagonal manner such that two diagonal phase edges crossed at the intersection corner for contact hole patterning, as is illustrated in the so called "Vortex mask" [9]. When the exposed phase edges are arrayed into dense grating, the effective transmission and effective phase can be modulated by the CD and duty cycle of the phase grating for target feature patterning [7,8,10].…”

Contact hole formation by multiple exposure technique in ultralow <inline-formula><math display="inline" overflow="scroll"><msub><mi>k</mi><mrow><mn>1</mn></mrow></msub></math></inline-formula> lithography

“…2. 1 In the case of the double L&S formation method, L&S patterns are formed separately. The common space area becomes a hole.…”