Elizabeth A. Dobisz

Rectangular Patterns Using Block Copolymer Directed Assembly for High Bit Aspect Ratio Patterned Media

We report a nanofabrication method that combines block copolymer directed assembly with e-beam lithography to achieve highly uniform rectangular patterns with a critical dimension of 16 nm, a full pitch of 27 nm, and arbitrary aspect ratio. This fabrication method enables geometries that are not natural to block copolymer assembly, preserves both the feature uniformity and the center-to-center spacing of the original block copolymer, sustains long-range translational order, and facilitates high-resolution, high-density patterns through feature density multiplication. These highly uniform arrays of dense rectangular features are particularly attractive for fabricating magnetic bit patterned media with high bit aspect ratio.

Patterned Media: Nanofabrication Challenges of Future Disk Drives

Scaling of the bit size in conventional magnetic recording media is becoming increasingly difficult due to the superparamagnetic limit. Innovations in magnetic recording technology are emerging to enable the continued growth in bit areal density. Thermal stability problems of conventional granular media can be greatly helped by patterning single domain magnetic islands for each magnetic bit. Fabrication of patterned media requires application of nanoimprint lithography for high-volume production of patterned media disks and high-resolution electron beam lithography for fabrication of the nanoimprint masters. We discuss the approaches and the many challenges to the implementation of patterned media disks.

Image quality and pattern transfer in directed self assembly with block-selective atomic layer deposition

Self-assembled block copolymer patterns may render more robust masks for plasma etch transfer through block-selective infiltration with metal oxides, affording opportunities for improved high contrast, high fidelity pattern transfer for sub-15 nm lithography in wafer-scale processes. However, block selective infiltration alters the self-assembled block copolymer latent image by changing feature size, duty cycle, and sidewall profile. The authors systematically investigate the effects of aluminum oxide infiltration of 27 and 41 nm pitch line/space patterns formed using polystyrene-b-poly(methyl methacrylate) block copolymers and evaluate the process compatibility with directed self assembly. The degree of image distortion depends on the amount of infiltrated material, with smaller amounts resulting in complete mask hardening and larger amounts shifting and collapsing pattern features. An attractive feature of the resulting oxide mask is the relatively smooth line edge roughness of the final transferred fea...

High-Density Bit Patterned Media: Magnetic Design and Recording Performance

We examine the magnetic properties and recording performance of bit patterned exchange coupled composite (ECC) magnetic media at different bit and island aspect ratios. The ECC media consists of Co/Pd and Co/Ni multilayers whose coupling is controlled using Pd interlayers. We show that this multilayer system can be tuned to provide writeable media with a low switching field distribution for bit patterned magnetic recording. The recording performance of 100 Gb/in2 media shows a sub 1e-4 bit error rate floor and misregistration errors that are well-described by a simple error model.

Fabrication of chevron patterns for patterned media with block copolymer directed assembly

Advances in block copolymer directed assembly have highlighted the potential of block copolymer lithography to define patterned templates for magnetic recording bit patterned media (BPM). The naturally periodic features found in block copolymer films display superior size uniformity at ultrahigh densities, making them ideal lithographic masks to define the highly periodic data bits in the data sector of hard disk drives. In addition to the data bits, BPM architecture requires additional features to encode servo information. Because of the nature of the information stored in servo sectors, the geometry and shape of servo features differ from those in the data sectors, potentially compromising their compatibility with the features that can be naturally formed by block copolymers. The authors investigated the compatibility of a block copolymer directed assembly with the formation of complex chevron structures for sector header servo patterns within the framework of a BPM design that uses rectangular bits as ...

Diamondoid Coating Enables Disruptive Approach for Chemical and Magnetic Imaging with 10 nm Spatial Resolution

Diamondoids are unique molecular nano-materials with diamond structure and fascinating properties such as negative electron affinity and short electron mean free paths. A thin layer of diamondoids deposited on a cathode is able to act as an electron monochromator, reducing the energy spread of photo-emitted electrons from a surface. This property can be applied effectively to improve the spatial resolution in x-ray photoemission electron microscopy (X-PEEM), which is limited by chromatic aberration of the electron optics. In this paper, we present X-PEEM measurements reaching the technological relevant spatial resolution of 10 nm without the need of expensive and complex corrective optics. Our results provide a simple approach to image surface chemical and magnetic information at nanometer scales by employing diamondoids.

Vertical directionality-controlled metal-assisted chemical etching for ultrahigh aspect ratio nanoscale structures

High aspect ratio nanoscale features are becoming increasingly important in a wide range of applications. In this paper, the authors describe the concepts of vertical directionality-controlled metal-assisted chemical etching (V-MaCE) and demonstrate resolution and fabrication capabilities for V-MaCE in the context of x-ray diffractive optics. The authors fabricate x-ray grating structures having a period of 50 nm, 25 nm lines, and 25 nm spaces, with a thickness of 1.26 μm, and achieve an aspect ratio of ∼50:1. In order to maintain the vertical etching profiles of these deep structures, the authors demonstrate the design and usage of adjacent, outrigger, gratings to balance the electron-hole concentration.

Bit patterned media optimization at 1 Tdot/in2 by post-annealing

We report on the fabrication of 1 Tdot/in2 bit patterned media with high coercivity (HC) and narrow intrinsic switching field distribution (iSFD) based on nanoimprint from a master pattern formed by e-beam guided block copolymer assembly onto a carbon hard mask and subsequent pattern transfer via etching into a thin CoCrPt perpendicular anisotropy recording layer. We demonstrate that an additional vacuum annealing step after pattern transfer into the CoCrPt layer and after Carbon hard mask removal not only yields recovery from undesired damage of the island edges, but actually transforms the islands into a magnetically more favorable compositional phase with higher HC, lower iSFD/HC, and three-fold increased thermal stability. Energy filtered transmission electron microscopy analysis reveals that the diffusion of Cr from the island cores to the periphery of the islands during post-annealing is responsible for the transformation of the magnetic bits into a more stable state.

Fabrication of 1 Teradot/in.2 CoCrPt bit patterned media and recording performance with a conventional read/write head

1 Teradot/in.2 (Td/in.2) CoCrPt alloy bit patterned media (BPM) disks were patterned by direct write e-beam lithography, and the recording performance was measured with a commercial recording head. Recording analysis showed a minimum error rate of 2 × 10−3, which was limited by the fraction of BPM patterning defects Continuous magnetic media disks were coated with a 20 nm thick carbon hard mask film by PECVD followed by a 8.5 nm thick hydrogen silsesquioxane (HSQ) resist by spin coating. A series of 1 Td/in.2 dot patterns were e-beam written in the HSQ, and the patterns were etched into the carbon hard mask by reactive ion etching. The underlying magnetic media was physically etched with 200 eV Ar. The carbon hard mask maximum thickness was limited by erosion of the HSQ dots during the carbon hardmask etch and shadowing of the mask during the magnetic media etch. The minimum carbon thickness and the maximum CoCrPt thickness were determined by erosion of the hardmask pillars during etching of the CoCrPt ma...

Front Matter: Volume 8102

This PDF file contains the front matter associated with SPIE Proceedings Volume 8102, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.