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Magnetic recording bit patterned media (BPM) stands as a promising technology to deliver thermally stable magnetic storage at densities beyond 1 Tb/in2. High throughput BPM fabrication will be enabled by nanoimprint lithography which relies on a high-quality master template to be able to meet pattern fidelity and low defectivity specifications. Master template fabrication for BPM can be done by e-beam lithography alone or by e-beam directed self-assembly of block copolymers. Incorporating servo features in the fabrication of master templates brings numerous nanofabrication challenges that vary depending on which method is used. Here we demonstrate the fabrication of conventional servo features at 200 Gd/in2 using e-beam lithography and we explore some nonconventional servo geometries that are compatible with self-assembly for BPM beyond 1 Td/in2.

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.

Magnetic lithography (ML) is a process qualitatively analogous to contact optical lithography which transfers information from a nanopatterned magnetic mask (analog of optical photomask) to magnetic media (analog of photoresist), and is interesting for applications in instantaneous parallel magnetic recording, in particular for servowriting applications. The magnetic mask consists of nanopatterned magnetically soft material (FeNiCo, FeCo) on a thin flexible plastic substrate, typically Polyethylene teraphtalate (PET) or polyimide. When uniformly magnetized media is brought into intimate contact with the magnetic mask, an externally applied magnetic field selectively changes the magnetic orientation in the areas not covered with the soft magnetic material. Flexible substrate of the magnetic mask offers superior compliance to magnetic media which is likely to have imperfect flatness and surface particulate contamination. We discuss nanofabrication challenges of magnetic masks on plastic substrates, including electron beam lithography, electroplating and lift-off processing on the nanometer scale, adhesion of metal thin films on PET and polyimide substrates, and release of plastic films from rigid substrates used during the processing. We present results on fabricated magnetic masks, magnetic force microscopy images of the magnetic transition patterns and disk spinstand tests of servowritten patterns.

The scanning force microscope (SFM) was used to investigate the temperature dependent micro mechanical properties of polymethylmethacrylate (PMMA) films with a thickness of 35 nm in the range of the radius of gyration. Force–distance curves were performed in the glass transition range to create permanent nanometric indentations with maximal forces up to 4 μN. Quantitative measurements of the indentation depth during and after application of the force, hysteresis energy and slope of the loading part are carried out as function of sample temperature and applied force. The glass transition of the polymer film can be clearly identified by the change of the mechanical properties of the polymer. Surprisingly, only a small change of elasticity at the glass transition is observed.

Load/unload (L/UL) has recently replaced contact start-stop (CSS) technology in major segments of the hard disk-drive (HDD) industry. Although L/UL has existed since the earliest HDDs, recent implementations use fixed ramp L/UL systems, which are considerably simpler than earlier versions. L/UL offers multiple advantages over CSS, including practically unlimited start-stop cycles and improved shock robustness. However, disk damage can occur in L/UL drives due to head-disk contacts, and a variety of parameters including vertical L/UL speed and slider corner radius should be optimized to minimize damage. Tight control of key tolerances is essential to maximize available disk real estate and minimize the required disk spacing to accommodate L/UL. Power-off retract systems for L/UL must produce higher retract torque than those for CSS designs, leading to new retract circuit designs.

A method for instantaneous parallel recording on magnetic media using a flexible master has been developed. Magnetic lithography (qualitatively analogous to optical lithography) transfers information from a patterned magnetic mask (analog of optical photomask) to magnetic media (analog of photoresist). The mask consists of patterned soft magnetic material (FeNiCo, FeCo) on a flexible polyethylene tetraphthalate (PET) substrate. When uniformly magnetized media is brought into intimate contact with the magnetic mask, an externally applied magnetic field selectively changes the magnetic orientation in the areas not covered with the soft magnetic material. Imperfect flatness or the presence of particular contaminants can result in local loss of intimate contact between the master and media, resulting in loss of resolution of submicron features in the transferred magnetic pattern. A flexible master, held against the media via an applied pressure, offers superior compliance to imperfections, even at relatively small applied pressures. We fabricated samples of submicron patterned FeCo and FeNiCo magnetic masks, and successfully transferred patterns to hard disk CrPtCo-based magnetic media. The details of the method, including fabrication of the magnetic mask on flexible PET substrates, physics of the magnetic lithography pattern transfer, and magnetic force microscopy images of the magnetic transition patterns are reported.

Bit patterned media (BPM) for magnetic recording has emerged as a promising technology to deliver thermally stable magnetic storage at densities beyond 1Tb/in2. Insertion of BPM into hard disk drives will require the introduction of nanoimprint lithography and other nanofabrication processes for the first time. In this work, we focus on nanoimprint and nanofabrication challenges that are being overcome in order to produce patterned media. Patterned media has created the need for new tools and processes, such as an advanced rotary e-beam lithography tool and block copolymer integration. The integration of block copolymer is through the use of a chemical contrast pattern on the substrate which guides the alignment of di-block copolymers. Most of the work on directed self assembly for patterned media applications has, until recently, concentrated on the formation of circular dot patterns in a hexagonal close packed lattice. However, interactions between the read head and media favor a bit aspect ratio (BAR) greater than one. This design constraint has motivated new approaches for using self-assembly to create suitable high-BAR master patterns and has implications for template fabrication.

A new frequency modulation (FM) technique has been demonstrated which enhances the sensitivity of attractive mode force microscopy by an order of magnitude or more. Increased sensitivity is made possible by operating in a moderate vacuum (

The atomic force microscope (AFM) can now bridge the gap from imaging objects that can be seen with an optical microscope to imaging atoms: a range in magnification of 104. High magnification images of germanium show single atoms separated by 0.4 nm while low magnification images of entire cells and portions of an integrated circuit chip provide lateral and vertical information over a range of 25 μm.

This paper approaches future areal density estimation for storage (tape, disk, and NAND flash) using processing and in particular minimum feature roadmaps. And discusses the process implications faced by recording storage for achieving these projections especially in the 2010 time period when disk areal densities are projected at 500 Gbit/in2, when disk drive minimum features converge with NAND flash features projected at 35 nm, and when a transition from continuous to patterned media may occur. The annual increases in IC memory density set the areal density increases that disk drives must achieve to maintain present day cost per bit ratios with solid state memory applications. Second, patterned media requires the formation of read and write sensors with dimensions that coincide with NAND flash dimensions. In sum, novel and cost effective minimum feature processing must be anticipated in order to sustain areal density growth for magnetic recording.

Ultrahigh storage densities of up to 1 Tb/in./sup 2/ or more can be achieved by using local-probe techniques to write, read back, and erase data in very thin polymer films. The thermomechanical scanning-probe-based data-storage concept, internally dubbed "millipede", combines ultrahigh density, small form factor, and high data rates. High data rates are achieved by parallel operation of large 2D arrays with thousands micro/nanomechanical cantilevers/tips that can be batch-fabricated by silicon surface-micromachining techniques. The inherent parallelism, the ultrahigh areal densities and the small form factor may open up new perspectives and opportunities for application in areas beyond those envisaged today.

Flexible Magneticsencompases the design, fabrication and characterization of magnetic devices and systems built on thin flexible substrates. Although device and system functionality is magnetic in nature, flexible magnetics draws interesting parallels to flexible electronics, especially in the challenge of fabrication on plastic substrates. Some of those challenges include substrate surface quality and maximum processing temperature, tooling issues related to mechanical properties of flexible substrates, adhesion of thin films deposited on plastics, as well as thermal stability of fabricated devices.One application of flexible magnetics relevant to the information storage industry is magnetic lithography. Magnetic lithography is a process qualitatively analogous to contact optical lithography. Magnetic lithography transfers information from a patterned magnetic mask (analogous to the optical photomask) to magnetic media (analog of the photoresist), and is interesting for applications in rapid, parallel magnetic recording. The magnetic mask consists of patterned magnetically soft material (FeNiCo, FeCo) on a thin flexible plastic substrate, typically Polyethylene Teraphtalate (PET) or polyimide. When uniformly magnetized media is brought into intimate contact with the magnetic mask, an externally applied magnetic field selectively changes the magnetic orientation in the areas not covered with the soft magnetic material. The flexible magnetic mask offers superior compliance to contaminated or nonplanar magnetic media. We discuss nanofabrication challenges of magnetic masks on plastic substrates, including electron beam lithography, electroplating and lift-off processing on the nanometer scale, adhesion of metal thin films on PET and polyimide substrate, and release of plastic films from the rigid substrates used during the processing. We present results on fabricated magnetic masks, and magnetic force microscopy images of the magnetic transition patterns.Besides fabrication of magnetic nanostructures and devices on plastic substrates, we also present our results on nanoscale patterning of plastic thin film. We will present our results on fabrication of sub-100 nm scale nanochannels in polyimide films, as well as self-assembly of ordered arrays of polyimide nanodots. Nanoscale patterned plastic films are interesting for the potential application in magnetic lithography, as well as for the application in micro- and nanofluidics, due to the mechanical flexibility and biological inertness of plastic materials. We will discuss interesting biosensing systems that may result from the combination of magnetic functionality, electronic control and patterned nanofludic channels on plastic substrates.

Ultrahigh storage densities of up to 1 Tb/in2. or more can be achieved by using local-probe techniques to write, read back, and erase data in very thin polymer films. The thermomechanical scanning-probe-based data-storage concept, internally dubbed "millipede", combines ultrahigh density, small form factor, and high data rates. High data rates are achieved by parallel operation of large 2D arrays with thousands micro/nanomechanical cantilevers/tips that can be batch-fabricated by silicon surface-micromachining techniques. The inherent parallelism, the ultrahigh areal densities and the small form factor may open up new perspectives and opportunities for application in areas beyond those envisaged today.

Flexible magnetic lithography is a process qualitatively analogous to contact optical lithography which transfers information from a patterned magnetic mask (analog of optical photomask) to magnetic media (analog of photoresist), and is interesting for applications in instantaneous parallel magnetic recording. The magnetic mask consists of patterned soft magnetic material (FeNiCo, FeCo) on a flexible plastic substrate, typically Polyethylene Teraphtalate (PET). When uniformly magnetized media is brought into intimate contact with the magnetic mask, an externally applied magnetic field selectively changes the magnetic orientation in the areas not covered with the soft magnetic material. Flexible substrate of the magnetic mask o.ers superior compliance to magnetic media which is likely to have imperfect flatness and surface particulate contamination.Although magnetic in physical nature, flexible magnetics draws interesting parallels to flexible electronics, especially in challenges of fabrication of sub-micron patterns on thin flexible plastic substrates. We fabricated samples of sub-micron patterned FeCo and FeNiCo magnetic masks on PET substrates by using combined lamination/release process of PET films. Rigid substrates, typically silicon or quartz were initially laminated with PET films and processed using standard fabrication procedures. After completing magnetic mask device fabrication, PET films were released from the rigid substrates.We successfully transferred patterns from magnetic masks to hard disk CrPtCo-based magnetic media. The details of the method, including physics of the magnetic lithography pattern transfer, fabrication of the magnetic mask on flexible PET substrates, lamination and release of PET films, and magnetic force microscopy (MFM) images of the magnetic transition patterns are reported.

A small hard disk drive for portable or hand-held applications is described, which is the result of the confluence of several technological trends. First, the individual technologies which underlie magnetic areal storage density are being improved at a rate which allows a 60% per year increase in data storage in a given area. As this rate continues, it becomes much more favorable to decrease the size of a magnetic disk drive. Secondly, there is currently major growth in the range and complexity of portable information/communication devices. The function (and ubiquity) of these devices is expanding rapidly through advances in miniaturization, power reduction and expanding communications infrastructure. Thirdly, general storage needs are also expanding, and are being driven particularly by the need to capture, transmit and store images. A prototype disk drive, called a Micro Drive, has been developed for this general market. Details of the design and components of the disk drive, which is compatible with the new Compact Flash CF Type II standard, are given. The device applications and functional performance issues are also addressed.

The atomic force microscope (AFM) is a promising new method for studying the surface structure of both conductors and insulators. In mapping a graphite surface with an insulating stylus, we have achieved a resolution better than 2.5 A.

We demonstrate a technique for measuring the intrinsic bit-error-rate as a function of write misregistration in bit patterned media. We examine the recording performance at bit densities of 100, 200, and 320 Gigabits per square inch (Gb/in2) and find that the on-track write misregistration margin for error rates below 10−4 is ∼1/4 of a bit length for all three densities. We demonstrate two-dimensional recording at sub 10−4 bit error rate at 100 and 200 Gb/in2 and with a 10−3 bit error rate at 320 Gb/in2.

The properties of monolayer films of organic materials are important for a variety of technologies. We have employed the STM and AFM to study Langmuir-Blodgett films of a variety of polymers on substrates of graphite, molybdenum sulfate, and gold (111) on mica. The polymers were poly(octadecyl acrylate) (PODA), atactic and syndiotactic poly(methyl methacrylate) (PMMA) and poly(2-methyl 1-pentene sulfone) (PMPS). One striking feature was the degree of order observed; a second was the morphological difference between films of submonolayer thickness (long thin fibrils) and those of at least monolayer thickness (lumpy structures arranged in domains). By pulsing the STM bias voltage to values in excess of 4 V, we were able to bring about local modification of the polymer morphology.

Direct imaging of ultrathin organic films on solid surfaces is important for a variety of reasons; in particular, the use of such films as ultrathin resists for nanometer scale fabrication and information recording requires that we understand their microstrucure. We have used the Langmuir–Blodgett technique to prepare monolayer and submonolayer films of poly(octadecylacrylate) (PODA) and poly(methylmethacrylate) (PMMA) on graphite substrates. Atomic scale images obtained with the scanning tunneling microscope (STM) and the atomic force microscope of the PODA films showed a variety of structures, including isolated narrow fibrils, parallel groups of fibrils, and an ordered structure consistent with the side chain crystallization expected with that material. The fibrils observed are interpreted as individual polymer chains or small bundles of parallel chains. Images of the PMMA samples show no ordered regions. By applying voltage pulses on the STM tip, we were able to locally modify and apparently cut throu...

The atomic force microscope (AFM) can be used to image the surface of both conductors and nonconductors even if they are covered with water or aqueous solutions. An AFM was used that combines microfabricated cantilevers with a previously described optical lever system to monitor deflection. Images of mica demonstrate that atomic resolution is possible on rigid materials, thus opening the possibility of atomic-scale corrosion experiments on nonconductors. Images of polyalanine, an amino acid polymer, show the potential of the AFM for revealing the structure of molecules important in biology and medicine. Finally, a series of ten images of the polymerization of fibrin, the basic component of blood clots, illustrate the potential of the AFM for revealing subtle details of biological processes as they occur in real time.

A new atomic force microscope, which combines a microfabricated cantilever with an optical lever detection system, now makes it possible to measure the absolute force applied by a tip on a surface. This absolute force has been measured as a function of distance (=position of the surface) in air and water over a range of 600 nm. In the absolute force versus distance curves there are two transitions from touching the surface to a total release in air caused by van der Waals interaction and surface tension. One transition is due to lifting off the surface; the other is due to lifting out of an adsorbed layer on the surface. In water there is just one transition due to lifting off the surface. There is also a transition in air and water when the totally released tip is pulled down to touch the surface as the surface and tip are brought together. Based on the force versus distance curves, we propose a procedure to set the lowest possible imaging force. It can now be as low as 10−9 N or less in water and 10−7 N...

Tilt boundaries have been observed on the (0001) surface of graphite by scanning tunneling microscopy (STM). Rotation angles about the c axis of 6.5°, 8°, and 19° were found, indicating no preferential orientation of grains in the basal plane of graphite. The grain boundary region between crystallites appears disordered with a width varying between 10 and 100 A. Moire patterns are observed near grain boundaries when multiple tips scanning over different grains contribute to the image simultaneously. Such images support the theory that multiple isolated tips, occasionally hundreds of angstroms apart, can contribute to STM images.

Atomic force microscope images of polymerized monolayers of n-(2-aminoethyl)-10,12-tricosadiynamide revealed parallel rows of molecules with a side-by-side spacing of approximately equal to 0.5 nanometer. Forces used for imaging (10(-8) newton) had no observable effect on the polymer strands. These results demonstrate that atomic force microscope images can be obtained for an organic system.

We present a reproducible technique for forming holes on a graphite surface with a scanning tunneling microscope. The holes have an average diameter of 40 A (20 A minimum) with an average resolvable spacing of 60 A. Holes are produced by applying a short voltage pulse (3–8 V, 10–100 μs) across the tunneling gap which removes one or more layers of graphite in a small region directly below the tip. Arrays of hundreds of holes have been formed with yields as high as 99.6%. The writing process has a higher success rate in air or in the presence of water vapor. This suggests that the physical mechanism is a chemical process.

The atomic force microscope (AFM) is a promising new method for studying the surface structure of both conductors and insulators. In mapping a graphite surface with an insulating stylus, we have achieved a resolution better than 2.5 A.