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NASA Space Hardware Science

NASA Building Massively Heat-Resistant Chips 172

Posted by kdawson
from the don't-bother-with-water-cooling dept.
coondoggie writes "NASA researchers have designed and built a new circuit chip that can take the heat of a blast furnace and keep on performing. Silicon carbide (SiC) chips can operate at 600 degrees Celsius or 1,112 degrees Fahrenheit where conventional silicon-based electronics — limited to about 350 C — would fail. The new silicon carbide differential amplifier integrated circuit chip may provide benefits to anything requiring long-lasting electronic circuits in very hot environments such as jets, spacecraft, and industrial machinery. In particular, NASA said SiC applications will include energy storage, renewable energy, nuclear power, and electrical drives."
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NASA Building Massively Heat-Resistant Chips

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  • by lordofthechia (598872) on Tuesday September 11, 2007 @11:57PM (#20566795)
    In case you didn't know, Apollo has been developing a system to grow diamond wafers through CVD (Carbon Vapor Deposition) for you guessed it, semiconductor use.

    Anyway SiC is used in jewelry [moissanite.com] too (obviously with the same properites), just never realized that it could be used to make microelectronic devices like this. Heh, my wife's engagement ring just got way cooler.
  • by Anonymous Coward on Wednesday September 12, 2007 @12:06AM (#20566869)
    http://en.wikipedia.org/wiki/Thermal_noise [wikipedia.org]

    TFA talked about an analog amplifier. As such, noise is a problem. The higher the temperature a circuit is operated at, the greater the noise. For some low noise applications, it is standard practice to run an amplifier in a liquid nitrogen bath. For most applications, room temperature is ok from a noise standpoint. The temperature TFA talks about would produce about three times the noise of a room temperature circuit. For many applications, that would be way too much.

    For some applications, high temperature operation would be hard to avoid. Landing a probe on Venus comes to mind in that regard. The extra noise induced by temperature should cause lots of engineering misery.
  • 350C for Silicon? (Score:4, Informative)

    by Mateorabi (108522) on Wednesday September 12, 2007 @12:13AM (#20566937) Homepage
    Summary claims 350C for traditional silicon, but most silicon based transistor manufacturers list only 125C as the maximum junction temperature. (Which makes the package temp max out at 70-85C.) Makes me question how fast and loose the author was playing with the numbers. Article starts with 600C for SiC, but in the same paragraph they are down to 500C for only < 2000hrs of operation? Hype?


    Also, do SiC transitors switch as fast as doped silicon? Otherwise the "make a pentium with it!" ideas might fall flat.

  • by lordofthechia (598872) on Wednesday September 12, 2007 @12:14AM (#20566939)
    Hmm... somehow lost my link to Apollo, well here [apollodiamond.com] it is.
  • by dido (9125) <dido@@@imperium...ph> on Wednesday September 12, 2007 @12:40AM (#20567217)

    Silicon carbide is really hard stuff. It's another name for the industrial abrasive carborundum [wikipedia.org] and it's generally harder than sapphire (9 on the Mohs scale) but slightly softer than diamond (10 on the Mohs scale).

  • Re:Sorry, OT... (Score:4, Informative)

    by Dunbal (464142) on Wednesday September 12, 2007 @12:58AM (#20567365)
    Don't worry, NONE of those digits are significant, since the ACTUAL temperature of a blast furnace is around [wikipedia.org] 2000-2300 degrees C. I certainly remember the kilns at the cement plant my dad worked at used to get up to around 1900 C. 600 degrees is nothing as far as furnaces are concerned, although it's more than your oven can do.
  • by GloomE (695185) on Wednesday September 12, 2007 @01:58AM (#20567745)
    Not all circuit boards are glass fiber.
    Ceramics are already used where you need precision e.g. wave guides.
  • by ACDChook (665413) on Wednesday September 12, 2007 @02:01AM (#20567767)

    Can you imagine a Venus lander 'floating' on a super-dense gas/liquid?
    And why would a Venus lander need to do this? Last I heard Venus was no gas giant. The Russian probes all seemed to find a solid surface to land on.
  • by jank1887 (815982) on Wednesday September 12, 2007 @02:11AM (#20567843)
    congratulations. you have no idea what you're talking about.

    high temperature boards are ceramic (AlN, Al2O3, HTCC, DBC, etc.) seeing as how they're fired from 1-2000C, they'll be ok.

    silver-glass die attaches are okay up to 400-450C. Beyond that, you have high-temp brazes, AuIn, AgAuGe, AgCu, oh and AuNi ok up to 950C.

    Circuit!= computer. Chip != microprocessor. SiC chips = power electronics switch or sensor components. sure, you could build a processor out of these, but you could also just go back and build a Pentium out of vac.tubes.

    It's a wide-bandgap semiconductor material that is being extensively developed for specific power or harsh environment applications. There currently are no MOS devices (used in your PC). Switching speeds typcially in the kilohertz range, for power conditioning. That chip is a single transistor, about the size of the piece of silicon in your PC. Finally, silicon's only okay to 150-200C. The article should have said 350F, not 350C.

    read and learn. http://en.wikipedia.org/wiki/Power_semiconductor_device [wikipedia.org]

  • the packaging... (Score:2, Informative)

    by Anonymous Coward on Wednesday September 12, 2007 @02:38AM (#20568021)
    the limiting factor with Si is infact the packaging AND that is going to be the limiting factor with SiC operating temp as well

    NASA are right in saying that Silicon can operate at 350C but that is the exposed die that isn't on any substrate and using spring-point connections
    Start packaging the thing up and you have the die solder down onto something, solder wires onto the die and it is these things that put the operating temp at 125C

    Semikron have IGBT modules that they say can operate upto a die temp of 175 simply because they have got a method of not using solder to bond the die down and they use spring-points todo the electronic/electrical connections all allowing the temp to be risen

    Sure SiC "may" be able to operate at some nice high temps BUT there are NO!!!! packaging available to take advantage of this!!! and thus the max temp comes crashing down to the nice 175 (or 125 depending if you can/cant use some of the more advance bonding methods)

    This is again all pie in the sky stuff anyway... The problem is SiC is a bitch to grow and their yield is very low due to micro-piping occurring in the wafers making them useless.
    Not only that they have only just been able to make a switch!!! SiC diodes have existed for a few years now and for custom modules you can get an inverter brick with SiC diodes and they have only just been able to make a JFET out of SiC that is low voltage/current/switching-speed....

    So much so that quite a few semiconductor makers have invested alot into diamond (cause when it grows it grows just as good as silicon, just slow... oh they aint figured out a way to dope it yet ;)).

  • Copper? (Score:3, Informative)

    by 2901 (676028) on Wednesday September 12, 2007 @07:24AM (#20569777) Homepage Journal
    The traditional challenge is to get the melting point of solder low enough. The worry about moving to lead-free solder is "how will we keep the melting point down." It is the silicon chip that is the delicate component
    that is damaged by heat.

    Ofcourse the low heat tolerance of silicon chips, by limiting permitted temperatures during manufacturing, also limits required temperatures. No-one requires circuit boards to withstand more heat than the components can take. So some materials that sheltered behind the poor temperature resistance of silicon chips are out, but there is no fundamental problem.
  • Re:350C for Silicon? (Score:1, Informative)

    by Anonymous Coward on Wednesday September 12, 2007 @08:03AM (#20570053)
    125C is what the vendor would recommend as maximum operating temperature for a silicon die for very simple parts. This is essentially based on reliability and what electrical parameter of the chip they are willing to "guarantee" or designed for.

    Translation:
    If you operate a chip beyond what it was designed for, then you are on your own. The chip might not even function correctly. The leakages of the chip and/or internal resistance might become so high that it would burn out. Metal might migrate into junctions and cross short circuit. Package or bond wire might break etc. A chip is make up of a large number of different parts that expand/contract differently.
  • by FuzzyDaddy (584528) on Wednesday September 12, 2007 @09:31AM (#20571131) Journal
    Tungsten is used in the current Aluminum metal via process, because it's very good at filling holes. (See Wikipedia [wikipedia.org] for a reference.

    I don't know if it's used for copper interconnects (I've been out of that business for years). It might work pretty well - the resistivity is twice that of Aluminum, which will slow down your interconnect performance some.

The flow chart is a most thoroughly oversold piece of program documentation. -- Frederick Brooks, "The Mythical Man Month"

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