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iRAP PATENT BRIEF

March 2009

By Alton Parrish, Senior Industry Analyst, iRAP, Inc

Four IBM researchers say they can cut the cost of mask making for use in nanoimprint technology by a factor of three in U.S. Patent Application 2008011660220080116602. IBM’s techniques result in perfect mask replicas with little need for stringent inspection and which can be used “in cut and paste” fashion to form smaller, longer and more complex device features not possible with traditional optical lithography (see feature story below).

University of Canterbury spinoff Nanocluster Devices Limited (Christchurch, NZ) received U.S. Patent 7,494,907 for simplified methods of preparing electrically conducting nanoscale wire-like structures called Percolating Cluster Assembled Nanodevices (PeCANs) and Templated Cluster Assembled Nanodevices (TeCANs) which can form transistors, sensors and optical devices at 20 nm nanoscales, smaller than permitted by optical lithography

Fanqing Chen and Jay Keasling of Lawrence Berkeley National Laboratory have developed a technology that opens up new territory for bioremediation, providing for separation of carbon-based nanomaterials, such as fullerene waste, from a liquid mixture by the addition of bacterial cells. The patent pending Bioremediation System for Separating Nanoparticle Waste is available for technology licensing from LBNL

Seagate received U.S. Patent 7,448,860 for its invention of a nanolubricant that facilitates the use of a stamper for forming sub-micron sized features and patterns in large area substrate surfaces by means of imprint lithography. The stamper has particular utility in the formation of servo patterns in the surfaces of substrates used in the manufacture of information storage and retrieval media, e.g., hard disk magnetic recording media.

Ashland Licensing and Intellectual Property LLC researchers have developed a novel use of nanomaterials as a viscosity modifier and thermal conductivity improver for gear oil and other lubricating oil compositions according to U.S. Patent Application #20080242566. The lubricant has higher viscosity index, higher shear stability, and improved thermal conductivity compared to currently available gear oils.

Deirdre Olynick and Weilun Chao of Berkeley Lab, and Ivo Rangelow of the University of IImenau, Germany, have developed a new dry etching process that alternates deposition and etching for producing and transferring nanoscale patterns in silicon, metals, or any materials that can be spontaneously etched in a fluorine-based chemistry. The new method, which offers a versatility at the nanoscale that previous methods have failed to achieve, can be used for either shallow or deep etching of thin films, metal molds, or silicon-based polymer films, or deep etching of metal, for example, to make zone plate lenses for X-ray or EUV (extreme ultraviolet) optical devices. It can also be used to etch nanofeatures for the fabrication of nanoresolution templates for nanoimprint lithography (NIL), nanodevices (e.g., nanoelectronics and nano-electro-mechanical systems [NEMS]), and nano-optics. The technology, covered by U.S. Patent Application 20070015371, is available for licensing and collaborative research.

University of Pittsburgh researchers Hong Koo Kim, Zhijun Sun and Christopher C.A. Capelli developed a metallic nano-optic device possesses multifunctional capability in shaping and processing (i.e., focusing, bending, collimating, and/or spatial- and wavelength-filtering) an optical beam (i.e., a focused, unfocused or diffuse incident radiation) in a fashion that overcomes the limitations of diffractive optics. According to U.S. Patent 7,492,530, the structure comprises a nanoaperture array which is designed to transmit a light with proper phase retardation between aperture elements such that the emerging beam evolves into a desired shape as it emanates from the apertures, similar to the beam shaping with a phased-array antenna in microwaves. The device utilizes the plasmonic phenomena occurring in nanoaperture arrays and preferably has spatial-, wavelength-, and/or polarization-filtering characteristic besides the beam shaping function. Finite-difference time-domain (FDTD) analysis results show that such devices are feasible in the optical frequency range.

North Carolina State University (Raleigh, NC) earned U.S. Patent 7,491,407 for a “Fiber-based nano drug delivery systems (NDDS).” According to inventors Behnam Pourdeyhimi, Rory Holmes and Trevor J. Little their process produces extruded fibers containing a mixture of drugs and pharmaceutically acceptable polymers such that the drugs form nanofibers. The nanofibers provide significant surface area allowing fast dissolution of the drugs. Means for directly forming such fibers into caplets or tablets are also an aspect of the invention.

FUJIFILM Corporation (Tokyo, JP) received U.S. Patent 7,491,487 for a Polymerizable composition and lithographic printing plate precursor.

ASML Netherlands B.V. (Veldhoven, NL) garnered U.S. Patent 7,491,478 for a Lithographic apparatus and device manufacturing method.

Tekna Plasma Systems Inc. (Sherbrooke, CA) won U.S. Patent 7,494,527 for its process for plasma synthesis of rhenium nano and micro powders and for coatings as well as the apparatus to make the powders.

iRAP Featured Discovery highlighting a patent or patent application

IBM Cut & Paste Masks Slash Imprint Lithography Costs

Photolithography has been the main lithographic tool for processing patterns of resist down to 45 nanometers (nm). However, present and future microelectronics will require minimum feature sizes below 45 nm. While advances in a number of lithography techniques (e.g., ultraviolet (UV), enhanced ultraviolet (EUV) emersion, maskless emersion, laser, phase-shift, projection ion, and electron beam lithography (EBL) may enable high-scale production at these dimensions, they are all nearing their theoretical limits with respect to wavelength, overlay accuracy, and/or cost. Pushed to the limit, the weaknesses of each process present difficult problems, and the resulting patterning defects can result in significant yield loss. Nanoimprint lithography offers solutions to 2 nm and smaller. .

IBM researchers developed a method (and lithographic masks and mold structures) to reduce the cost of fabricating a lithographic mask (or mold) by spatially segmenting the process to employ one or more independently verified multi-use imprint sub masks. Inventors Matthew E. ; Colburn, Yves C Martin, Theodore G van Kessel and Hematha K Wickramasinghe reveal in U.S. Patent Application 20080116602 a cut-and-paste imprint lithographic mold that could result in “a factor of three (3) improvement in costs” by reducing mask making expenses by maintaining “molecular fidelity.”

The traditional mask making process itself introduces a multitude of distortions and defects that must be individually corrected and inspected. The serial printing and inspection of lithographic masks (or molds) is expensive and time-consuming. A phase shift mask might cost $150,000 and may require a month to fabricate and inspect.

The construction of a mask is usually performed using e-beam lithography. Once constructed, the mask is then inspected and, if necessary, repaired. The mask write time and subsequent inspection is by far the longest part of the process. For example, a critical mask (e.g., using optical phase correction or OPC) may take 24-48 hours to print using the e-beam tool, but may take days to inspect. Hence, the inspection process (which may include some repair time of the defects found during the inspection) takes relatively the most time.

Mask costs are expected to keep increasing with decreases in size. A set of masks costs about $800,000 at 90 nm, and at least $1.2 million at 65 nm. Setting up a he modern 45 nm process mask shop can cost between $200-500 million. The purchase price of a photomask can range from $1,000 to $150,000 for a single, high end phase shift mask; as many as 30 masks (varying in price) may be required to manufacture a complete mask set.

Imprint lithography faithfully reproduces the mask pattern, often to molecular dimensions. By this, it is meant that features on the imprint mask (or mold) are the same size and in the same relative location as the features printed on the chip. By using imprint lithography, the inspection time is significantly reduced because imprint lithography reproduces a pattern with features with molecular fidelity. In cases calling for a multi-chip mask if one produces a single instance of a chip, which is perfect and which is referred to as the "master", then it is possible to produce replicas of the chip (in the case of a multi-chip mask) which are similarly accurate (perfect) and which therefore would not need an inspection, or at least not a rigorous inspection as that for the first chip ("master"). If the chip is perfect (e.g., defect-free) in one area, then replicas of the chip likewise should be defect-free in all areas.

IBM’s method forms a redundant pattern on multiple masks or molds, including forming an imprint mold for a single redundant element and inspecting the imprint mold, and lithographically imprinting the pattern on the mold onto multiple product masks or molds. Thus, the present inventors have recognized that many lithographic levels on a given product contain patterned regions that are common to more than one product. Examples may include embedded RAM, SRAM, processor elements etc. In addition, it is often common to have more than one chip on a single mask (i.e., 2.times.2 array). In the case of a common, 4-chip mask, there might be a factor of three (3) improvement in costs. The more chips on the mask, the greater the savings will be.

Thus, with the 4-chip mask, first one would start by having an existing pattern on the mask, and then that pattern would be repeated a plurality of times (e.g., 4 times) on the mask, either directly 4 times, or in the case of existing patterns, then the chip could be added thereto. It is a well known attribute of two-dimensional self assembly processes that long range order is difficult to achieve. If a portion of the pattern can be made perfect (as in the present invention), it can be copied and replicated using cut-and-paste imprint lithography and extended to larger areas or used to advantage in discrete locations. The power of this technique is that a given topographic pattern need only be made perfect once. Thereafter, it can be used whole or in part to realize larger instances or multiple instances of the pattern

In addition to chip patterns in the conventional sense, pattern topography information can be cut and pasted with similar cost improvements. Any topography resulting from self assembly, a biological process, an optical interference process etc. can be replicated and copied to other areas, with great advantage. It is a well known attribute of two-dimensional self assembly processes that long range order is difficult to achieve. If a portion of the pattern can be made perfect, it can be copied and replicated using cut-and-paste imprint lithography and extended to larger areas or used to advantage in discrete locations. The power of this technique (e.g., the inventive technique) is that a given topographic pattern need only be made perfect once. Thereafter, it can be used whole or in part to realize larger instances or multiple instances of the pattern.

Thus, the fundamental implication of the method and system is that a perfect pattern once produced can be replicated many times. Consequently, in the case of a patterning process that works with low probability (i.e., self assembly), the invention makes the pattern available for manufacturing.
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