WORLD’S 1ST:SPRAY ON SILICON INKJET

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WORLD’S 1ST:SPRAY ON SILICON INKJET

 user 2006-04-13 at 10:12:00 am Views: 58
  • #15072

    Spray-on silicon makes its debut
    April 2006
    Researchers
    in Japan have unveiled a new way to make silicon-based microelectronic
    devices. The method involves depositing silicon directly onto a
    substrate from solution and overcomes some of the problems associated
    with traditional silicon-processing lithographic techniques, such as
    using sophisticated clean rooms and expensive vacuum equipment. The
    researchers say the technique could lead to a way of making large,
    flexible displays using “ink-jet” technology .
    Silicon
    microelectronic devices are currently made by heating highly purified
    silicon in a vacuum and allowing the resulting “mist” of free silicon
    atoms to coat a surface such as a plastic. Once deposited, the solid
    film is etched and patterned using photolithography techniques to
    produce circuit elements. However, this method is expensive and
    complicated because it has to be carried out in an ultra-clean
    environment to ensure that impurities do not contaminate the silicon
    and ruin its electronic properties.
    The new technique, developed by
    a team led by Masahiro Furusawa of the Seiko Epson Corporation in
    Nagano-ken, avoids these complications. It uses a liquid form of
    silicon that can be made at room temperature and pressure and can then
    be sprayed onto a surface using an ink-jet printer.
    Furusawa and
    co-workers start with a molecule called cyclopentasilane, which
    contains five silicon atoms joined in a ring. When this liquid is
    exposed to ultraviolet light, some of the rings break open to form
    linear chains. These link up end-to-end to form even longer chains,
    producing a highly viscous fluid.
    The team dilute the liquid with an
    organic solvent, which they then deposit on a surface either by
    spin-coating or ink-jet printing. The resulting liquid film is finally
    heated at around 500°C, which converts it into hard, polycrystalline
    silicon. The team claims to have been able to make transistors from the
    films.
    According to the scientists, the electronic properties of
    their films are as good as those of ultra-pure films made by
    conventional processing techniques. Although the properties of the
    ink-jetted films were not quite as good as those that were
    spray-coated, the former were still much better than solution-processed
    films of organic carbon-containing materials.
    The new process is not
    perfect, however, as air and water have to be carefully excluded.
    Furthermore, the current ink-jetting method does not have the
    resolution necessary to pattern high-density integrated circuits needed
    to make computer chips. Nevertheless, the technique could be a novel,
    inexpensive and easy way of making devices for a range of everyday
    electronic equipment, including circuits for large-area displays, solar
    cells and sensors.

            
    Silicon film, TFTs use micro-liquid processes
    Apr
    2006Seiko Epson Corp. and JSR Corp. claims to have succeeded in
    creating the world’s first silicon film with liquid coating and inkjet
    patterning processes. The performance of low-temperature polysilicon
    thin-film transistors (LTPS TFTs) produced with silicon film formed by
    the spin coat method is said to be comparable to that achieved when
    using silicon film formed using the conventional CVD method.
    The new
    material jointly announced by Epson and JSR is a high order silane
    compound of hydrogen and silicon dissolved in an organic solvent. It
    forms a silicon film when spin coated on the substrate and baked in an
    inert atmosphere. When fabricating a TFT prototype using a silicon film
    formed by spin coating (other than the formation of the silicon coat,
    the production process is the same as for conventional LTPS TFTs), the
    electrons achieved mobility of 108cm2/Vs.
    Epson used its proprietary
    micro liquid processes to demonstrate the possibilities of printed
    TFTs, forming a silicon film pattern onto a substrate by firing the
    materials onto a substrate using the inkjet method. As a result, part
    of the pattern formation associated with traditional photolithography
    is unnecessary, said the company. Forming a TFT prototype using a
    silicon film pattern using the inkjet method, the electrons achieved
    mobility of 6.5cm2/Vs, a figure that is said to be lower than that
    achieved with spin coating. Although improvements need to be made to
    the inkjet process, Epson believes that printed TFTs show sufficient
    potential.|
    This research was commissioned by Japan’s New Energy and
    Industrial Technology Development Organization, an incorporated
    administrative agency.