We describe a novel deterministic bottom-up / top-down approach to sub-30 nm photolithography using a film composed of assembled block brush polymers of highly uniform composition and chain length. The polymer architecture consists of a rigid backbone of polymerized norbornene, each linked to flexible short side brush chains. The resultant ‘bottle brush’ topology has a cylindrical shape with short brush chains arranged concentrically around the backbone, in which the cylinder radius is determined by the number of monomers within the brush fragment, while the cylinder length is determined by the degree of backbone polymerization. The modularity of the synthetic system allows a wide diversity of lithographically useful monomers, sequencing, dimension and property variation. Sequential grafting of pre-synthesized blocks allows for facile formation of either concentric or lengthwise block copolymers. Placement of brush chains of different compositions along different regions of the cylinder, along with variation of the relative concentric and lengthwise dimensions, provides mechanisms to align and control placement of the cylinders. These polymers are compatible with photoacid generators (PAGs) and crosslinker functionality. Our results are consistent with a model that the bottle brush polymers assemble (bottom-up) in the film to yield a ‘forest’ of vertically arranged cylindrical block brush polymers, with the film thickness determined by the coherence lengths of the cylinders. Subsequent imaging via electron beam (EB or ebeam) or optical radiation yields a (top-down) mechanism for acid catalyzed crosslinking of adjacent cylinders. Uncrosslinked cylinders are removed in developer to yield negative photoresist patterns. Exposure doses are very low and throughputs are amenable to the requirements of Extreme Ultraviolet (EUV) lithography. The limiting resolution with ebeam exposure is potentially about two cylinder diameters width (< 8 nm), with the smallest observed patterns approaching 10 nm.

Date Published: 29 March 2013
PDF: 13 pages
Proc. SPIE 8682, Advances in Resist Materials and Processing Technology XXX, 86820H (29 March 2013); doi: 10.1117/12.2014528

Published in SPIE Proceedings Vol. 8682:
Advances in Resist Materials and Processing Technology XXX
Mark H. Somervell, Editor(s)