Swift Nanopattern Formation of PS-b-PMMA and PS-b-PDMS Block Copolymer Films Using a Microwave Assisted Technique

Abstract

Microphase separation of block copolymer (BCPs) thin films has high potential as a surface patterning technique. However, the process times (during thermal or solvent anneal) can be inordinately long, and for it to be introduced into manufacturing, there is a need to reduce these times from hours to minutes. We report here BCP self-assembly on two different systems, polystyrene-b-polymethylmethacrylate (PS-b-PMMA) (lamellar- and cylinder-forming) and polystyrene-b-polydimethylsiloxane (PS-b-PDMS) (cylinder-forming) by microwave irradiation to achieve ordering in short times. Unlike previous reports of microwave assisted microphase segregation, the microwave annealing method reported here was undertaken without addition of solvents. Factors such as the anneal time and temperature, BCP film thickness, substrate surface type, etc. were investigated for their effect of the ordering behavior. The microwave technique was found to be compatible with graphoepitaxy, and in the case of the PS-b-PDMS system, long-range translational alignment of the BCP domains was observed within the topographic patterns. To demonstrate the usefulness of the method, the BCP nanopatterns were turned into an 'on-chip' resist by an initial plasma etch and these were used to transfer the pattern into the substrate.

Block Co-Polymers for Nanolithography: Rapid Microwave Annealing for Pattern Formation on Substrates

“…Directed self-assembly of PS-b-PDMS on topographic patterns has been demonstrated in a number of articles [3,4,19,21,[32][33][34][35][36][37][38]. Further, Buriak et al has shown the effectiveness of microwave assisted method to guide cylinder-forming PS-b-PMMA and PS-b-P4VP BCPs on topographically patterned substrates [39].…”

“…This was followed by an O2 plasma etch to remove PS and affect oxidation of the PDMS to yield silica-like topographies indicative of the original BCP pattern. These steps follow similar methodology developed by Ross et al [17] and full etch details are available elsewhere [3,4,[18][19][20].…”

“…Here, we apply the use of the emerging microwave assisted solvothermal method (work in this area is in its infancy compared to more established methods of inducing self-assembly [2][3][4]) to promote self-assembly of a polystyrene-blockpolydimethylsiloxane (PS-b-PDMS) BCP at Si3N4 substrates and demonstrate the usefulness of this approach. This BCP has particular relevance because of its high Flory-Huggins parameter (χ) [12] which allows sub-10 nm feature size scaling [13][14][15][16], whilst high etch selectivity between PS and PDMS [17] facilitates selective removal of PS to form topographical silica-like patterns [3,4,[18][19][20].…”

Monitoring Thermally Induced Cylindrical Microphase Separation of Polystyrene-<i>block</i>-poly(methyl methacrylate) by Atomic Force Microscopy

“…Industrial demands for acceptable lithographic applications request the DSA process within 240 seconds [13,17]. The solvothermal method [18], microwave annealing method [19], and rapid thermal annealing method [20,21] are studied to shorten a DSA process period.…”

Study of the Kinetics and Mechanism of Rapid Self-Assembly in Block Copolymer Thin Films during Solvo-Microwave Annealing

“…Recently, the use of microwave has been demonstrated with poly(styrene-b-dimethylsiloxane) (PS-b-PDMS) system. 9 However, despite the promise of this technique, little is known about the mechanism of how microwave irradiation might sponsor the molecular motion that accompanies microphase separation. Buriak and coworkers have championed substrate heating as the primary source of molecular motion driven by defects in silicon substrates that absorb microwave radiation.…”