Technology News
05/01/2005
Japanese engineers rate top technologies
SST’s partner Nikkei Microdevices sure didn’t come up with the usual names when it recently surveyed Japanese engineers on the hot companies to watch in the semiconductor industry. Most companies generated interest for rethinking the business model, not pushing technology limits, and few were established semiconductor players. The only two companies rated for purely technological breakthroughs were from the automotive sector - Toyota for its high quality SiC, and Bridgestone for its fast-reacting powder for displays. Japanese startup System Fabrication Technologies also got attention for its new approach to combining logic and memory chips into a chip-like system-in-a-package.
Toyota’s new method for growing high-quality SiC crystals looks likely to enable production of better high-voltage, high-temperature devices using SiC instead of silicon. Toyota affiliate Denso Corp. is starting development of power devices on SiC that may be ready for market in as little as two years, using the higher-quality and larger substrates grown with the repeated a-face method developed with Toyota Central R&D Laboratories. The Central Lab’s Daisuke Nakamura says the new crystal growth method shouldn’t be more costly than current products because it only requires a couple of extra steps at the beginning of the process.
Growing an SiC crystal tends to propagate the defects in the seed crystal, which spread vertically in the direction of the crystal growth. Toyota and Denso researchers slice off the growing crystal vertically, parallel to the growth direction and the defect lines, creating a crystal face with very few defects that can then be used as the new seed crystal to restart growth. The new crystal growth then has few defects, and if it is again sliced off parallel to the growth direction and defect lines, an even higher quality face is obtained, for an even better seed for growing a very low-defect crystal. The process makes 4H-SiC with 75 dislocation defects/cm2, two to three orders of magnitude fewer than other growth methods, and apparently essentially no micropipes.
A more unusual, potentially disruptive technology is tiremaker Bridgestone’s new quick-response liquid powder display, which uses a black and a white powder between glass sheets, based on the carbon black used in tires and more recently in toners. The black powder bears a positive charge, the white a negative charge, so one coats the top glass sheet, the other the bottom, depending on the charge to the glass. Change the charge, and the powders quickly switch positions, changing any point on the display from black to white, with no backlights, light loss or viewing angle issues. The powder reacts in 0.2 msec and the display holds its picture until the threshold voltage is again applied. Bridgestone plans to market its first low-cost, low-power display using the powder later this year.
System Fabrication Technologies, meanwhile, offers a new hybrid approach it calls system-on-silicon to integrate separate chips, which it claims gets system-on-a-chip performance with system-in-a-package memory capacity and low cost. The trick is essentially moving the upper global interconnect layers off the individual chips and onto a shared interconnect chip. The combination is designed as a unit using standard EDA tools; the chips are manufactured separately and then connected with microbumps. Company executives say they’ve made a unit with an embedded 128Mbit DRAM with 1024bit bus width using the approach - much more memory capacity than the 64 Mbits possible even in a 90nm-process SoC, and much higher bus width than the 32 bits possible with an SiP.
 Figure 2. SFT’s rethinking the SoC replaces vias with microbumps to integrate separate application chips on a global interconnect chip. |
The company plans to supply users with design software for easy integration of their ASIC designs with its own specially tweaked DRAM design, and then will assemble the multichip units onto the silicon interconnects. Users can design their ASIC as usual with their current EDA tools, but the macro software will treat the separate logic and memory chips as IP units, will convert the upper-level SoC interconnects to layers in a separate Si interposer, and will convert the vias into microbumps connecting the separate devices to the interposer. The venture will then microbump the separately manufactured ASICs and DRAMs to the interposer, contracting out the process to Shinko Electric.
SFT aims to have first samples of a combination of H.264 logic and DRAM chips for a video application ready by this summer, using a 0.11µm design rule and 60µm-pitch bumps.
Other top 10 companies to watch included eASIC, MediaTek, MEMS Core, Aldete, eSilicon, Jemitek, and Hirata Corp.
- PennWell partner Nikkei Microdevices
Nanotech gets more exotic: Carbon nanotubes could enable inkjet printing of electronic features
Even stranger than some of the current nanotechnology hype is some of the current nanotechnology science. Japanese researchers have found that water inside carbon nanotubes remains frozen up to room temperature, and then vaporizes all at once when heated up only slightly more. These unexpected properties propel the water out of the tube, suggesting that nanotubes could be used as nozzles for inkjet printing of very fine electronic features, relatively easily controlled by limited laser heating.
Hiromichi Kataura, of AIST’s Nanotechnology Research Institute, and Yutaka Maniwa, of Tokyo Metropolitan University, found that the smaller the diameter of the single-walled carbon nanotube, the higher the melting point of the water within it, just the opposite of what happens within small glass tubes. Water molecules inside a carbon nanotube of 1.17nm dia. remained ice up to 27°C, then vaporized at 45°C, at subatmospheric pressure. The reason for these surprising results is little understood, but the researchers suggest it may be related to the stable structure of stacked five-molecule rings the water forms within the nanotube.
 Water in a 1.17nm dia. carbon nanotube forms tube-shaped ice, which melts at 27°C, and vaporizes at 45°C, shooting out of the tube. (Source: AIST) |
Though inkjet printing of extremely fine features has been limited by the relatively large size of the manufacturable nozzles, carbon nanotubes could potentially perform ultraprecise printing. Since nanotubes of different crystalline structures differentially absorb light of different wavelengths, changing the wavelength of the light could heat only selected nanotubes, vaporizing and jetting out the ink in the patterns desired. Of course it remains to be seen if the effect still works with metals and dielectrics in the solution.
- PennWell partner Nikkei Microdevices