Yuko Tsuchiya

Microswelling-free negative resists for ArF excimer laser lithography utilizing acid-catalyzed intramolecular esterification

We have examined alicyclic polymers with a (gamma) -hydroxy acid structure in order to investigate the properties of (gamma) -hydroxy acid and (gamma) -lactone as function groups of ArF negative resist materials. From the viewpoint of transparency and dry-etching resistance, (gamma) -hydroxy acid and (gamma) -lactone structure were found to be suitable for ArF negative resists materials. Surprisingly, the reactivity of the acid-catalyzed reaction of (gamma) -hydroxy acid is affected by the polymer structure. Using ArF excimer laser stepper, 0.20-micrometers line-and-space patterns without micro-swelling distortion were obtained from a negative resist consisting of alicyclic polymer with the (gamma) - hydroxy acid structure and a photoacid generator. Distortion was avoided because the number of carboxyl groups decreased drastically in the exposed area by the acid-catalyzed intramolecular esterification of (gamma) -hydroxy acid to (gamma) -lactone. As a result, (gamma) -hydroxy acid and (gamma) -lactone structure were found to be suitable function groups for ArF negative resist materials.

Silicon Mold Etching with Hard Mask Stack Using Spherical Structure of Block Copolymer for Bit-Patterned Media with 2.8 Tbit/in.2

We investigated a silicon mold fabrication that uses a hard mask stack by using poly(methyl methacrylate)-block-poly(methacrylate polyhedral oligomeric silsesquioxane) (PMMA-b-PMAPOSS) as the block copolymer (BCP) to assemble nano-patterns for a nano-imprint lithography process during bit-patterned media manufacturing. We developed a dry development process comprised of a single step by taking both the selectivity and anisotropy into consideration, which enables us to create hole patterns by using an array of PMMA spheres embedded in a PMAPOSS matrix. The availability of this process was evaluated from the experimental results that showed that hole patterns at several areal densities were successfully obtained by adjusting the process time under a fixed etching condition. The capability of the pattern transfer to a hard mask from the hole patterns of residual PMAPOSS could be improved by changing the hard mask material from SiO2 to amorphous carbon based on the results from an X-ray photoelectron spectroscopy (XPS) surface analysis. Silicon molds with areal densities of up to 2.8 Tbit/in.2 were successfully fabricated by using an optimized process condition and the hard mask stack.

Fabrication of Discrete Track Media with Patterned Servo-areas and Tracks on Disk Substrate

Discrete track media (DTM) with patterned servo-areas and recording tracks were fabricated on disk substrates in a two-step RIE process, creating a fine pattern transfer from an imprinted resist mask to a substrate surface without variations in groove depth. The fabricated DTM with perpendicular magnetic recording layers flew stably during read out signal detection.