Yautzong Hsu

Directed Self‐Assembly of Poly(2‐vinylpyridine)‐b‐polystyrene‐b‐poly(2‐vinylpyridine) Triblock Copolymer with Sub‐15 nm Spacing Line Patterns Using a Nanoimprinted Photoresist Template

Low molecular weight P2VP-b-PS-b-P2VP triblock copolymer (poly(2-vinlypyridine)-block-polystyrene-block-poly(2-vinylpyridine)] is doped with copper chloride and microphase separated into lamellar line patterns with ultrahigh area density. Salt-doped P2VP-b-PS-b-P2VP triblock copolymer is self-assembled on the top of the nanoimprinted photoresist template, and metallic nanowires with long-range ordering are prepared with platinum-salt infiltration and plasma etching.

Servo-Integrated Patterned Media by Hybrid Directed Self-Assembly

A hybrid directed self-assembly approach is developed to fabricate unprecedented servo-integrated bit-patterned media templates, by combining sphere-forming block copolymers with 5 teradot/in.(2) resolution capability, nanoimprint and optical lithography with overlay control. Nanoimprint generates prepatterns with different dimensions in the data field and servo field, respectively, and optical lithography controls the selective self-assembly process in either field. Two distinct directed self-assembly techniques, low-topography graphoepitaxy and high-topography graphoepitaxy, are elegantly integrated to create bit-patterned templates with flexible embedded servo information. Spinstand magnetic test at 1 teradot/in.(2) shows a low bit error rate of 10(-2.43), indicating fully functioning bit-patterned media and great potential of this approach for fabricating future ultra-high-density magnetic storage media.

Cleaning induced imprint template erosion

Abstract. We studied the erosion and feature stability of fused silica patterns under different template cleaning conditions. The conventional sulfuric acid and hydrogen peroxide mixture (SPM) cleaning is compared with an advanced nonacid process. Spectroscopic ellipsometry optical critical dimension measurements were used to characterize the changes in pattern profile with good sensitivity. This study confirmed the erosion of the silica patterns in the traditional acid-based SPM cleaning mixture (H2SO4+H2O2) at a rate of ∼0.1  nm per cleaning cycle. However, the advanced nonacid cleaning process only showed critical dimension shift of ∼0.01  nm per cleaning. Contamination removal and pattern integrity of sensitive 20-nm features under MegaSonic assisted cleaning was also demonstrated.

Spectroscopic ellipsometry optical critical dimension measurements of templates and imprinted resist for patterned magnetic media applications

The authors have applied spectroscopic ellipsometry optical critical dimension (SE-OCD) measurement to grating templates and imprinted resist patterns with a pitch of 72.6 nm, corresponding to a track density of 350 ktpi (kilotracks per inch) for discreet track recording media. Their experiments indicate that SE-OCD is sensitive in detecting topography features in template profiles. The measurement of imprinted resist pattern is complicated by parameter correlation. Comparison of SE-OCD reported template and imprinted resist profiles can be used to study imprint pattern fidelity.

Imprint directed self-assembly of cylinder-forming Si-containing block copolymer for 6nm half-pitch line patterning

A new imprint directed self-assembly (DSA) route is developed for creating high resolution line patterns consisting of in-plane polystyrene-block-polydimethylsiloxane (PS-b- PDMS) cylinders. Resist line prepatterns are prepared by nanoimprint and trimmed by oxygen plasma to proper feature geometry and dimension. Registered block copolymer line patterns with exceptional long-range order are generated after DSA then, with the smallest half-pitch of 6 nm or so. Excellent stretching capability of PS-b-PDMS polymer chains indicates a broad process window for DSA. Initial pattern transfer results at 16.5 nm pitch imply the potential of this approach for future nanodevice fabrication at ultra-high pattern resolution.

Controlling template erosion with advanced cleaning methods

We studied the erosion and feature stability of fused silica patterns under different template cleaning conditions. The conventional SPM cleaning is compared with an advanced non-acid process. Spectroscopic ellipsometry optical critical dimension (SE-OCD) measurements were used to characterize the changes in pattern profile with good sensitivity. This study confirmed the erosion of the silica patterns in the traditional acid-based SPM cleaning mixture (H2SO4+H2O2) at a rate of ~0.1nm per cleaning cycle. The advanced non-acid clean process however only showed CD shift of ~0.01nm per clean. Contamination removal & pattern integrity of sensitive 20nm features under MegaSonic assisted cleaning is also demonstrated.