Solvent-Tunable Orientation and Confinement-Induced Feature Compression in High-χ Cylindrical Block Copolymer Thin Films

The self-assembly of block copolymers (BCPs) serves as a highly promising bottom-up approach for fabricating periodic nanostructures in microelectronics and semiconductor applications, particularly for achieving high-resolution patterning through directed self-assembly. However, controlling the orientation of high-χ BCPs remains challenging due to their strong incompatibility and the complexity of interfacial interactions and processing conditions. This study investigates the effects of solvent-block interactions by modulating the χ parameter between the solvent and the blocks, thereby achieving control over both horizontal and vertical orientations of cylindrical high-χ BCPs poly[2-(perfluorobutyl) ethyl methacrylate]-block-poly(2-vinylpyridine) (PFPV). Compared with low-χ BCPs, PFPV exhibits significant feature compression under side-wall confinement, forming nanostructures smaller than its intrinsic periodic feature size (L₀ = 16 nm). As the trench width decreases, the pattern size progressively compresses from 14.5 to 12.4 nm. When the LWR exceeds 5 nm, the template width window for guiding linear BCP stripe formation narrows markedly; when it exceeds 7 nm, vertically oriented stripes parallel to the template edges tend to undergo a lateral reorientation, a phenomenon in agreement with the simulation results. Finally, the process window evaluation confirms that well-ordered self-assembled morphologies were achieved in templates with dimensions smaller than 104 × 216 nm². As the template width increased from 120 to 168 nm, linear arrays were maintained but exhibited minor alignment defects. Beyond 168 × 168 nm², fingerprint-like patterns gradually formed due to the weakening of template confinement effects. These findings demonstrate the potential of high-χ BCPs for fabricating periodic dense line arrays suitable for advanced technology nodes. This study provides new insights into solvent-tunable orientation control and template compatibility mechanisms, contributing significantly to the advancement of nanofabrication technology.