Incorporation of direct current superposition as a means for high quality contact and slotted contact structures utilizing litho-freeze-litho-etch

Incorporation of litho-freeze-litho-etch (LFLE) double patterning techniques have had limited uses in the industry due to a number of issues including : LER / LWR degradation of 1st layer patterning during the 2nd exposure, the necessity to utilize thermal `freezing' resists which necessitate the incorporation of alcohol-based resist systems, and the inability of extending such processes to NTD resist platforms which have superior patterning capabilities for specific structures which are attractive for LFLE type of applications. The incorporation of directed current superposition (DCS) `freeze' process enables greater flexibility in the materials selection for a true litho-freeze-litho-etch process without incurring any of the detriments of previous LFLE processes. By creating a method to crosslink and harden the initial resist pattern through interaction of ballistic electrons and through the deposition of a thin SiO 2 skin overtop the hardened feature, the initial structure becomes impervious to any solvent attack or exposure-effects associated with typical LFLE processes while simultaneously providing a mechanism to enable a very controllable method for C/H shrink. Additionally, the incorporation of the DCS freeze process provides unlimited flexibility with respect to resist material selection and enables the incorporation of NTD based resists in order to leverage the small trench and hole printing capabilities of these resists in the generation of small contacts and slot contacts through various cross-point double patterning methods. The DCS process can even be tuned to provide LER / LWR benefits to the initial pattern in order to create good fidelity performance of the final structure. We will present results through etch showing the generation of slotted and circular contacts through the LFLE process incorporating the directed current superposition process incorporating multiple type of resist platforms in order to produce a library of different types of contact structures.