Block Copolymer Directed Self-Assembly: Modeling and Characterization Challenges for Next Generation Materials for Nanomanufacturing

Abstract:

Block copolymer (BCP) self-assembly is one of the front running material based methods to fabricate integrated circuits and bit-patterned memory storage media with feature sizes in the sub-20 nm regime. Traditional photolithographic methods have reached fundamental limits in their ability to fabricate ever smaller features, and alternative approaches such as BCPs are necessary to continue the shrinking features sizes that have driven the semiconductor industry for the past few decades. BCPs fit this role nicely as they naturally form periodic nanoscale structures due to the dissimilar chemistry of the blocks but constrained chain connectivity. A few issues need to be resolved for BCPs to move from the laboratory into actual device fabrication. The most critical aspect of BCP self-assembly that needs addressing is ensuring the morphological patterns produced during processing have defect-free long-range order.

In this presentation, two critical aspects of BCP self-assembly are examined. The first is using directed self-assembly (DSA) processes to ensure the patterns produced by the BCPs indeed have long-range order and the desired morphology. DSA combines top-down techniques like electron beam lithography to make templates that interact with the bottom-up self-assembly of the BCPs to complement the best aspects of both methods to achieve better control of the nanomanufactured materials. Several case studies of topographical templated DSA are examined. Experimentally fabricated sample results using polystyrene-b-polydimethylsiloxane are shown to agree with the predictive results of self-consistent field theory (SCFT) calculations. These results show the ability of physical models like SCFT to be a design tool for BCP DSA. The second aspect explored is having a non-destructive quality control characterization technique to ensure patterns produced from BCP DSA are the morphologies expected for a given set of conditions. Critical dimension small angle X-ray scattering (CDSAXS) has showed promise as a non-invasive technique capable of extracting real space periodic nanoscale features for periodic nanogratings. This X-ray scattering technique was applied to lamellae forming polystyrene-b-poly(methyl methacrylate) DSA samples. The internal morphology is then found from the data using SCFT models that best reproduce the scattered experimental intensity. By designing the right DSA template with SCFT and using methods like CDSAXS to characterize and validate the model, both SCFT and CDSAXS will enable BCP DSA to solve problems in future nanomanufacturing materials.