Path to Move Beyond the Resolution Limit with Directed Self-Assembly

Directed self-assembly (DSA) of block copolymers (BCPs) has long been viewed as a powerful alternative to extend the resolution of optical lithography. For full-area patterning applications, despite significant progress, the two most prominent DSA methods (chemoepitaxy and graphoepitaxy) are facing a scalability challenge: the critical dimension (CD) of the guiding patterns will need to be continuously scaled down to closely match the dimension of the BCP microdomain, a task that not only contravenes some of the resolution gains achieved by density multiplication but that will also become particularly difficult below 10 nm. To avoid this conundrum, we propose here a synergistic integration of graphoepitaxy and chemoepitaxy through self-registered self-assembly (SRSA) to enable the simultaneous realization of feature density multiplication and CD shrinkage resolution gains. We report nearly perfect DSA on prepatterns with high density multiplication factors and CD of several multiples of the BCP microdomain size. A prepattern consisting of alternating stripes of a relatively thicker neutral mat and a thinner neutral brush with preferential wetting sidewalls serves as a topographic pattern to guide an ultrathin BCP blend film inside the trenches. As the oriented BCP pattern assembles, the blend film deploys a layer of chemical markers on the bottom surface through SRSA generating 1:1 chemical contrast patterns inside the trenches. After thorough removal of the blend film, the newly formed self-registered chemical patterns interpolated by the remaining neutral mat strips serve as the guiding patterns for a second chemoepitaxial DSA step to achieve full-area, defect-free DSA of thick BCP films.

Double-Patterned Sidewall Directed Self-Assembly and Pattern Transfer of Sub-10 nm PTMSS-b-PMOST

The directed self-assembly (DSA) of two sub-20 nm pitch silicon-containing block copolymers (BCPs) was accomplished using a double-patterned sidewall scheme in which each lithographic prepatterned feature produced two regions for pattern registration. In doing so, the critical dimension of the lithographic prepatterns was relaxed by a factor of 2 compared to previously reported schemes for DSA. The key to enabling the double-patterned sidewall scheme is the exploitation of the oxidized sidewalls of cross-linked polystyrene formed during the pattern transfer of the resist via reactive ion etching. This results in shallow trenches with two guiding interfaces per prepatterned feature. Electron loss spectroscopy was used to study and confirm the guiding mechanism of the double-patterned sidewalls, and pattern transfer of the BCPs into a silicon substrate was achieved using reactive ion etching. The line edge roughness, width roughness, and placement error are near the target required for bit-patterned media applications, and the technique is also compatible with the needs of the semiconductor industry for high-volume manufacturing.