Mixed Signals
Any sufficiently advanced information is indistinguishable from noise
Tuesday 24 June 2008, 12:41 PM
Nanowires!
Just in the lunch break (yes! Fed at last!) at the IBM Zurich labs show-and-tell day, which as usual is full of sessions that overrun and no time to do anything except scribble the most incomprehensible of notes.
One of the more interesting things happening here is nanowire – the creation of very thin whiskers of material that can be used to make novel and potentially groundbreaking semiconductor devices. So far, these have mostly been made out of silicon, and the way you create a forest of these is disarmingly simple.
First, take your silicon wafer. Then, print a pattern of nanometric gold dots on it – I'll get back to how IBM do that later. Take your wafer covered in tiny gold particles, heat it up until the gold melts and stick it in an atmosphere of a gas containing more silicon. The vaporous silicon dissolves in the gold dots until no more can be absorbed – a supersaturated solution – at which point, the silicon in the gold starts to crystallise out at the barrier where the gold is resting on the silicon wafer. This creates a small bulge in the wafer, pushing the gold dot upwards. The process continues, with the bulge turning into a whisker, then a wire, all the time growing upwards.
This isn't fast – only around 50 nanometres a minute – but you can do billions at a time. Once you have your nanowires, you can deposit other stuff around them to create transistors that work at extremely small voltage swings, extremely fast. And it looks as if this will work down to around 9nm, which will be just in time: from having devices looking good in the lab to getting into development normally takes five to six years, and then it's another five to six years from there into production. 2020 is a reasonable guess.
Just about any material can be grown as a nanowire – indeed, by changing the gas composition during the process, you can change material and grow different zones and mixes of elements. IBM is particularly interested in what are known as III-V elements, which cluster around the part of the periodic table that's good at making electronics, because they're also optically active: we haven't had the optical interconnect talk yet but IBM, like everyone else, is absolutely convinced that there's only one way forward for high performance computing, and that's by using more and more light.
Right, off to the labs...
One of the more interesting things happening here is nanowire – the creation of very thin whiskers of material that can be used to make novel and potentially groundbreaking semiconductor devices. So far, these have mostly been made out of silicon, and the way you create a forest of these is disarmingly simple.
First, take your silicon wafer. Then, print a pattern of nanometric gold dots on it – I'll get back to how IBM do that later. Take your wafer covered in tiny gold particles, heat it up until the gold melts and stick it in an atmosphere of a gas containing more silicon. The vaporous silicon dissolves in the gold dots until no more can be absorbed – a supersaturated solution – at which point, the silicon in the gold starts to crystallise out at the barrier where the gold is resting on the silicon wafer. This creates a small bulge in the wafer, pushing the gold dot upwards. The process continues, with the bulge turning into a whisker, then a wire, all the time growing upwards.
This isn't fast – only around 50 nanometres a minute – but you can do billions at a time. Once you have your nanowires, you can deposit other stuff around them to create transistors that work at extremely small voltage swings, extremely fast. And it looks as if this will work down to around 9nm, which will be just in time: from having devices looking good in the lab to getting into development normally takes five to six years, and then it's another five to six years from there into production. 2020 is a reasonable guess.
Just about any material can be grown as a nanowire – indeed, by changing the gas composition during the process, you can change material and grow different zones and mixes of elements. IBM is particularly interested in what are known as III-V elements, which cluster around the part of the periodic table that's good at making electronics, because they're also optically active: we haven't had the optical interconnect talk yet but IBM, like everyone else, is absolutely convinced that there's only one way forward for high performance computing, and that's by using more and more light.
Right, off to the labs...
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