At last, semiconductor industry begins embracing nano
BY PAULA DOE
Even though the conservative semiconductor industry, with its extreme performance and manufacturing demands, has done much of its manufacturing in nanoscale dimensions for years, it hasn’t yet had much use for the unique properties of nanoparticles, fullerenes, nanowires, quantum dots, etc.-the technologies usually considered “true” nanotech. Nor have the nanoscale patterning processes developed by the chip makers been of much use to the rest of the nanotechnology world.
But the old ways are starting to change. Among the emerging technologies selected by the volunteer committee of industry executives to highlight this year at the chip industry’s big SEMICON West show (July 16-20, San Francisco) are modeling of nanoscale properties, nanoscale control of diamond thin films, and high-throughput nanoimprinting. All are nanotechnology solutions already implemented in electronics products, and all have potential for applications in other sectors, too.
Modeling nano effects for materials screening
Plug in the chemical elements of a material, and take a guess at its structure, and Atomistix Inc.’s modeling software will crunch out a prediction of the material’s electrical properties. The software bases its projections on the laws of quantum mechanics that govern electron transport at the nanoscale.
The Copenhagen-based company says modeling can screen new materials for desired properties considerably faster even than combinatorial synthesis experiments. Moreover, says company president Kurt Stokbro, “The model shows how the material would work if it were perfect, and can quantify the impact of defects.” He notes that in a recent search for new spintronics memory structures, the model predicted what turned out to be the best material, although it took considerably longer to get the experiments to confirm that it worked.
Atomistix’s software enables visualization of a ZnO nanowire’s conductive density, calculated across about 500 atoms and 5000 electrons in about 12 hours on a 16-node PC cluster.
“As geometries move further down the nanoscale, the costs of experiments continue to climb, but the cost of computing continues to plummet, so modeling becomes more and more cost-effective,” says Stokbro. He notes a recent study by market researcher International Data Corp. (IDC) showing that modeling software typically returned $3 to $9 for every $1 invested. The study focused on the pharmaceutical industry, where usage is more established, and revealed that the heaviest users realized the best returns.
Atomistix’s software allows researchers to build and manipulate atomic scale models of nanoelectronic devices, to calculate things like the transport properties of nanowires and carbon nanotubes, leakage voltage in semiconductor structures, and charge transfer in biological systems. It can also simulate how the measurement probe itself influences these nano systems and can calculate virtual measurement data that can be compared with experimental results.
The effective potential of a cross section of the wire.
The Atomistix models were developed over the past 10 years at the Technical University of Denmark and have so far been used mostly by Ph.D.s, either in theoretical physics or chemistry research at universities or in large companies. But advances in computer capability have recently enabled the processing of huge models in a time- and cost-efficient manner. With greater intelligence in the models, Atomistix is stepping up its efforts to make them easier for engineers to use and is offering training workshops and consulting help.
Adding diamond to the engineer’s toolkit
Advanced Diamond Technologies (ADT) aims to make diamond just another material for engineers to consider for realizing the performance they need. The Romeoville, Ill.-based company is introducing diamond-on-insulator (DOI) wafers, ready for sacrificial etching of MEMS devices. In addition, ADT has released diamond MEMS products of its own to show off the possibilities of devices designed to take advantage of diamonds’ properties.
Because of the material’s hardness, structures made entirely of diamond (not just coated with diamond film) don’t wear out as fast as silicon-based ones. And because diamond is naturally hydrophobic, parts made from it are less likely to stick to each other-meaning diamond-based designs avoid a major source of reliability problems. Finally, diamond’s stiffness and light weight enable it to vibrate at higher frequencies than most other materials, making it potentially attractive for things like MEMS RF devices, pressure sensors, resonators, microphones, and AFM probe tips.
This diamond micro-scale tuning fork filters and selects RF signals in the same way a radio works to tune an FM signal.
Diamond thin films have been around for some time, but they’ve typically been rough, highly variable, expensive, and in limited supply. ADT’s president Neil Kane says his company can meet tight specifications with its patented diamond-film technology, ultrananocrystalline diamond (UNCD), which is grown one atom at a time in 3 to 5nm crystals by a CVD semiconductor process. The process yields a smooth surface without polishing, and the company is now ramping up production to ensure a reliable supply for MEMS makers. “We’re making the wafers available, so designers can now start developing with diamond in ways that weren’t possible before,” says Kane.
The company has been working to exploit the acoustic velocity of diamond for a high-frequency RF micromachine. The device is destined for a rugged, broadband wireless telecommunications systems-for military and civilian applications-in a DARPA-funded project. Diamond resonators will reportedly enable devices to work above 5 billion cycles per second (5GHz).
ADT is also working with seal supplier John Crane Inc., coating the surfaces of mechanical seals with the diamond film to improve friction and wear characteristics in extreme environments. And it’s working on diamond packaging and electrodes to improve biocompatibility and reduce the size of implantable electronics with the DOE effort to develop an implantable electronic artificial retina or seeing-eye chip.
Moving NIL into production
At last it seems that nanoimprint lithography (NIL) is starting to move from the lab into the factory. One customer is using Obducat’s NIL technology to produce an optical component that forms a part of a consumer product now on the market. And others are experimenting with NIL for producing high-brightness LEDs, hard disks, and optical media.
Malmo, Sweden-based Obducat AB recently launched a roduction model based on its NIL technology that has a throughput of up to 30 wafers per hour. Obducat argues that the technology now looks easily scalable to higher volumes, with 90 wafers per hour its next goal. “Imprint is going to be the enabling lithography technique for people who want to print nanostructures in a very cost-efficient way,” says Marc Beck, senior applications engineer at Obducat.
These SEM micrographs show the discrete track recording pattern on a polymer stamp pressed from an Obducat-made master (top), and its imprint on a hard-disk substrate (bottom).
Key to Obducat’s increased throughput is getting more mileage out of the costly wafer-scale master stamp, which must be patterned very slowly with an e-beam. The company uses this permanent master to press out multiple disposable stamps on rolls of polymer. Creating disposable polymer stamps has a number of advantages. First, pressing them continually cleans the master, as any particles stick to the polymer. Also, using the soft stamps prevents damage to the master that would occur if a particle came between the hard master and the hard target substrate. Finally, using each polymer intermediary stamp only one time prevents contamination. While one imprint head is stamping out the polymer stamps, a second head presses them onto the substrate.
Also potentially useful for scaling is Obducat’s use of a full-wafer stamp instead of a step-and-repeat system-and its soft press technology, which uses pressurized gas to apply pressure evenly across large and uneven substrates.
The developers of these and other showcased nano and MEMS innovations-including Nano Cluster Devices’ selective deposition of copper nanoclusters, Karma Technology’s quick-change probe tip modules, and Energetiq’s short-wavelength plasma lamps without contaminating electrodes-will be available to explain and demonstrate them at the Emerging Technologies TechXpot at SEMICON West; see www.semiconwest.org/ProgramsandEvents/TechXPOTS/000182 for details.