Peter R. Krauss

Imprint of sub-25 nm vias and trenches in polymers

A nanoimprint process that presses a mold into a thin thermoplastic polymer film on a substrate to create vias and trenches with a minimum size of 25 nm and a depth of 100 nm in the polymer has been demonstrated. Furthermore, the imprint process has been used as a lithography process to fabricate sub‐25 nm diameter metal dot arrays of a 100 nm period in a lift‐off process. It was found that the nanostructures imprinted in the polymers conform completely with the geometry of the mold. At present, the imprinted size is limited by the size of the mold being used; with a suitable mold, the imprint process should mold sub‐10 nm structures with a high aspect ratio in polymers. The nanoimprint process offers a low cost method for mass producing sub‐25 nm structures and has the potential to become a key nanolithography method for future manufacturing of integrated circuits and integrated optics.

Imprint Lithography with 25-Nanometer Resolution

A high-throughput lithographic method with 25-nanometer resolution and smooth vertical sidewalls is proposed and demonstrated. The technique uses compression molding to create a thickness contrast pattern in a thin resist film carried on a substrate, followed by anisotropic etching to transfer the pattern through the entire resist thickness. Metal patterns with a feature size of 25 nanometers and a period of 70 nanometers were fabricated with the use of resist templates created by imprint lithography in combination with a lift-off process. With further development, imprint lithography should allow fabrication of sub-10-nanometer structures and may become a commercially viable technique for manufacturing integrated circuits and other nanodevices.

Sub-10 nm imprint lithography and applications

Nanoimprint lithography (NIL) is a new lithography paradigm that is based on deformation of a resist by compression molding rather than altering its chemical structure by radiation, and is designed to fabricate nanostructures inexpensively with high throughput. In this paper, we present significant new developments in achieving holes and dots with 6 nm feature size, 40 nm period on silicon, and 10 nm feature size, 40 nm period on a Au substrate. Moreover, we present an application of NIL to the fabrication of nanoscale compact disks (NanoCDs) of 400 Gbits/in/sup 2/ data density.

Imprint lithography with sub-10 nm feature size and high throughput

Abstract Nanoimprint lithography, a high-throughput, low-cost, nonconventional lithographic method proposed and demonstrated recently, has been developed and investigated. Nanoimprint lithography has demonstrated 10 nm feature size, 40 nm pitch, vertical and smooth sidewalls, and nearly 90° corners. Further experimental study indicates that the ultimate resolution of nanoimprint lithography could be sub-10 nm, the imprint process is repeatable, and the mold is durable. In addition, uniformity over a 15 mm by 18 mm area was demonstrated and the uniformity area can be much larger if a better designed press is used. Nanoimprint lithography over a non-flat surface has also been achieved. Finally, nanoimprint lithography has been successfully used for fabricating nanoscale photodetectors, silicon quantum-dot, quantum-wire, and ring transistors.

Single‐domain magnetic pillar array of 35 nm diameter and 65 Gbits/in.2 density for ultrahigh density quantum magnetic storage

Using electron beam nanolithography and electroplating, arrays of Ni pillars on silicon that have a uniform diameter of 35 nm, a height of 120 nm, and a period of 100 nm were fabricated. The density of the pillar arrays is 65 Gbits/in.2—over two orders of magnitude greater than the state‐of‐the‐art magnetic storage density. Because of their nanoscale size, shape anisotropy, and separation from each other, each Ni pillar is single domain with only two quantized perpendicular magnetization states: up and down. Each pillar can be used to store one bit of information, therefore such nanomagnetic pillar array storage offers a rather different paradigm than the conventional storage method. A quantum magnetic disk scheme that is based on uniformly embedding single‐domain magnetic structures in a nonmagnetic disk is proposed.

Nanolithographically defined magnetic structures and quantum magnetic disk (invited)

Isolated and interactive arrays of magnetic nanostructures as small as 15 nm are fabricated using nanolithography and related technologies, and are characterized using magnetic force microscopy. It has been demonstrated that manipulating the size, aspect ratio, and spacing of these nanostructures can lead to unique control of their magnetic properties. A quantum magnetic disk based on discrete single‐domain nanomagnetic structures with storage density of 65 Gbits/in.2 is demonstrated along with a low‐cost method for mass producing such disks. Other impacts that nanofabrication can bring to the development of future magnetic storage are discussed.

NANO-COMPACT DISKS WITH 400 GBIT/IN2 STORAGE DENSITY FABRICATED USING NANOIMPRINT LITHOGRAPHY AND READ WITH PROXIMAL PROBE

Nano-compact disks (Nano-CDs) with 400 Gbit/in2 topographical bit density (nearly three orders of magnitude higher than commercial CDs) have been fabricated using nanoimprint lithography. The reading and wearing of such Nano-CDs have been studied using scanning proximal probe methods. Using a tapping mode, a Nano-CD was read 1000 times without any detectable degradation of the disk or the silicon probe tip. In accelerated wear tests with a contact mode, the damage threshold was found to be 19 μN. This indicates that in a tapping mode, both the Nano-CD and silicon probe tip should have a lifetime that is at least four orders of magnitude longer than that at the damage threshold.

Nanoscale silicon field effect transistors fabricated using imprint lithography

We report the fabrication and characterization of nanoscale silicon field effect transistors using nanoimprint lithography. With this lithographic technique and dry etching, we have patterned a variety of nanoscale transistor features in silicon, including 100 nm wire channels, 250-nm-diam quantum dots, and ring structures with 100 nm ring width, over a 2×2 cm lithography field with good uniformity. Compared with devices fabricated by the conventional electron-beam lithography, we did not observe any degradation in the device characteristics. The successful fabrication of the semiconductor nanodevices represents a step forward to make nanoimprint lithography a viable technique for the mass production of semiconductor devices.

Study of nanoscale magnetic structures fabricated using electron‐beam lithography and quantum magnetic disk

Two types of nanoscale single‐domain magnetic structures were fabricated using e‐beam nanolithography and were studied using magnetic force microscopy. The first structure is the isolated and interactive arrays of Ni bars on silicon that are 35 nm thick, 1 μm long, and have widths ranging from 15 to 200 nm and spacings ranging from 200 to 600 nm. The second structure is an array of Ni pillars on silicon that have a uniform diameter of 35 nm, a height of 120 nm, and a density of 65 Gbits/in2—over two orders of magnitude greater than the state‐of‐the‐art magnetic storage density. It was found that the magnetic properties of these structures can be controlled by engineering their size and spacing. When the bar width is smaller than 150 nm, the bars become single magnetic domain. As the width of the isolated bars decreased from 200 to 55 nm, the magnetic field needed to switch the magnetization of these bars increased monotonically from 100 to 740 Oe which is the highest field reported for Ni. However, further reduction of bar width led the switching field to decrease due to thermal effect. Furthermore, it was found that as the bar spacings become smaller, the interaction between the bars will reduce the switching field. Finally, based on the artificially patterned single‐domain magnetic structures, we propose a new paradigm for ultra‐high‐density magnetic recording media: quantum magnetic disk.

Fabrication of planar quantum magnetic disk structure using electron beam lithography, reactive ion etching, and chemical mechanical polishing

A planar quantum magnetic disk (QMD) with a magnetic storage density of 65 Gbit/in.2, over two orders of magnitude greater than the state‐of‐the‐art magnetic storage density, has been fabricated. The planar QMD structure consists of single‐domain nickel (magnetic) nanopillars uniformly embedded in a SiO2 (nonmagnetic) disk. Electron beam lithography was used to define the QMD bit’s size and location, and reactive ion etching was used to form an SiO2 template. Nickel electroplating was used to selectively deposit nickel into the template openings, and chemical mechanical polishing was used to planarize the surface. The resulting QMD consists of ultrahigh density arrays of single‐domain magnetic pillars with a 50 nm diameter and 100 nm period uniformly embedded in 200‐nm‐thick SiO2 and with a surface roughness of 0.5 nm root mean square. Each single‐domain structure has a quantized magnetic moment and acts as a single bit to store one bit of binary information. Furthermore, a method for mass production of Q...