New self-assembly strategies for next generation lithography

Abstract

Future demands of the semiconductor industry call for robust patterning strategies for critical dimensions below twenty nanometers. The self assembly of block copolymers stands out as a promising, potentially lower cost alternative to other technologies such as e-beam or nanoimprint lithography. One approach is to use block copolymers that can be lithographically patterned by incorporating a negative-tone photoresist as the majority (matrix) phase of the block copolymer, paired with photoacid generator and a crosslinker moiety. In this system, poly(-methylstyrene-block-hydroxystyrene)(PMS-b-PHOST), the block copolymer is spin-coated as a thin film, processed to a desired microdomain orientation with long-range order, and then photopatterned. Therefore, selfassembly of the block copolymer only occurs in select areas due to the crosslinking of the matrix phase, and the minority phase polymer can be removed to produce a nanoporous template. Using bulk TEM analysis, we demonstrate how the critical dimension of this block copolymer is shown to scale with polymer molecular weight using a simple power law relation. Enthalpic interactions such as hydrogen bonding are used to blend inorganic additives in order to enhance the etch resistance of the PHOST block. We demonstrate how lithographically patternable block copolymers might fit in to future processing strategies to produce etch-resistant self-assembled features at length scales impossible with conventional lithography.

Fast Assembly of Ordered Block Copolymer Nanostructures through Microwave Annealing

“…This technology underpins the entire integrated circuits industry, and yet it is ultimately expected to reach fundamental resolution limits. − As a result, new strategies are being sought to complement photolithography and achieve next generation requirements in a cost-effective manner. Among the array of possibilities, self-assembly is emerging as a powerful option, and the use of self-assembled block copolymers (BCPs) to generate organized nanostructures is becoming the subject of intense research. − Recent editions of the Semiconductor Industry Association’s International Technology Roadmap for Semiconductors (ITRS), in fact, explicitly include templating with BCPs as an emerging technology for generating high-resolution patterns . With these soft polymeric materials, the size and spacing of structures can be tuned by selecting appropriate polymer block lengths, and nanostructures as small as 3 nm in diameter can be generated .…”

In pursuit of Moore’s Law: polymer chemistry in action

“…Schwartz et al 20 used a first-generation block Photoresist chemistry in the semiconductor field H Xu et al polymer, poly(α-methylstyrene-block-hydroxystyrene) (Figure 2a) with the hydroxyl functionality of polyhydroxystyrene (PHOST) allowing photochemical crosslinking, when blended with photoactive generators and crosslinkers. By annealing the film first in acetone, crosslinking the film using UV light and then switching the uncrosslinked areas using THF vapor, two different morphologies on one layer of block copolymer film were demonstrated for the first time (Figure 2b).…”