Fine Tuning of Lithographic Masks through Thin Films of PS-b-PMMA with Different Molar Mass by Rapid Thermal Processing

Abstract

The self-assembly of asymmetric polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) block copolymer based nanoporous thin films over a broad range of molar mass (Mn) between 39 kg·mol(-1) and 205 kg·mol(-1) is obtained by means of a simple thermal treatment. In the case of standard thermal treatments, the self-assembly process of block copolymers is hindered at small Mn by thermodynamic limitations and by a large kinetic barrier at high Mn. We demonstrate that a fine tuning of the annealing parameters, performed by a Rapid Thermal Processing (RTP) machine, permits us to overcome those limitations. Cylindrical features are obtained by varying Mn and properly changing the corresponding annealing temperature, while keeping constant the annealing time (900 s), the film thickness (∼30 nm), and the PS fraction (∼0.7). The morphology, the characteristic dimensions (i.e., the pore diameter d and the pore-to-pore distance L0), and the order parameter (i.e., the lattice correlation length ξ) of the samples are analyzed by scanning electron microscopy and grazing-incidence small-angle X-ray scattering, obtaining values of d ranging between 12 and 30 nm and L0 ranging between 24 and 73 nm. The dependence of L0 as a 0.67 power law of the number of segments places these systems inside the strong segregation limit regime. The experimental results evidence the capability to tailor the self-assembly processes of block copolymers over a wide range of molecular weights by a simple thermal process, fully compatible with the stringent constraints of lithographic applications and industrial manufacturing.

Development and Synchrotron‐Based Characterization of Al and Cr Nanostructures as Potential Calibration Samples for 3D Analytical Techniques

“…The SEM micrograph shown in Figure a confirms the formation of hexagonally packed nanometer size cylinders, perpendicularly oriented with respect to the substrate. The in‐plane morphology of the DBC pattern, the pore diameter ( d ) (Figure b) and the center‐to‐center distance between the pores ( L 0 ), were extracted from SEM image on a large area, ≈ 8 × 8 μm 2 , following the procedure described in literature . The results of this analysis, as well as the film thickness and porosity extracted from SE, are reported in Table .…”

“…An asymmetric PS‐ b ‐PMMA DBC with molar mass ( M n ) of 67 kg mol −1 was selected for this work. The DBC deposition (Figure ‐a3 and b3) and successive annealing step were carried out following the procedure described in literature . By this step, phase segregation between PS and PMMA was finalized and perpendicular orientated cylinders of PMMA were formed in a PS matrix (Figure ‐a4 and b4).…”

High temperature surface neutralization process with random copolymers for block copolymer self‐assembly

“…In principle, the value of the Flory − Huggins interaction parameter χ for this class of materials would allow the preparation of nanoscale periodic patterns featuring a domain resolution of ca 11 nm when a BCP with a molecular weight of 39 kg mol −1 is employed . However, this value is never reached because, after removal of the PMMA component, the pore opening procedure involves an exposure step to oxygen plasma to completely remove the grafted RCP layer.…”

Evolution in surface morphology during rapid microwave annealing of PS‐b‐PMMA thin films

“…(D)]. The fraction of perpendicular cylinders at the free surface increases to approximately 75% at 20 W. In contrast, simple thermal annealing for 12 h at 160 °C leads to increased long‐range order of parallel cylinders in comparison to the as cast film, as expected for films thicker than 2 L 0 …”

“…In general, rapid thermal annealing techniques using laser heating, radiation in rapid thermal processing, or microwave energy have been able to provide similar (or even better) ordering kinetics without the same EHS concerns . As such there has been significant interest in microwave annealing for DSA.…”