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Printing Chips
batty writes :"Nature has this article about a process that uses a quartz die and a laser to mechanically print features onto chips instead of photo-etching them. The article mentions engraving a silicon wafer with features only 10 nanometres in size, as opposed to 130 nanometres using photlithography, and the process is quicker, simpler, and more environmentally friendly than current processes. Which is nice."
... four days ago. But thanks for the link to the Nature article.
Good grief, study some EE instead of spouting off.
Silicon is used to make the TRANSISTORS. This is because it is easy to implant boron etc. into the silicon for making the wells in the transistor. This process (if manufacturable in high volume) will be useful for making the TRANSISTORS. You still have to connect them. What are you going to do, deposit silicon on top of the wafer, now, to make another "mask"? Then melt the silicon and pour in metal on top of that or something? If you've figured out how to do that the combined might of the semiconductor industry wants to pay you a lot of money!
No, you have to deposit various layers of metal and dielectric to connect the transistors. Many ICs have up to 7 or 8 layers of metalization, which means depositing the ILD, putting in interconnects, and depositing the metal (think "wires"). Currently the only way to do this is through photo masking followed by some deposition process.
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You have a number of implicit assumptions in your comment which I would like to query. As well as the /. article, I have read the The Economists take on the same research.
Point 1 - they are not talking about a single-die stamper. Actually they were talking about a whole-wafer stamper, created by e-beam lithography, If, as you suggest, a single stamper is good for only 500 stamps, this gives a 500:1 power boost to e-beam - good going.
Point 2, the stamping is not purely mechanical. A laser beam at a frequency at which the quartz stamper is transparent but the silicon isn't is shone through the stamper. This softens the silicon, so the stamper presses into it. No photoresist, and far less mechanical wear on the stamper. Quartz is pretty damned hard stuff, whereas softened silicon is (I guess) not - so I would guess a lifetime in the thousands or tens of thousands for the stamper, not hundreds.
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Nature's article stated that a laser was used to 'liquify' silicon and then the quartz mask was pressed into the resulting mush. This doesn't make sense because (a) heat is something you dont want when doing fine patterning - thermal expansion tends to cause everything to shift by microns, and you want to work with nanometers. (b) Melting silicon and then quickly re-cooling it tends to destroy the crystal structure which is needed for semiconductors to work. Making a single Si crystal requires long, SLOW cooling. (c) Even if the previous items could be overcome, so what? Pressing a pattern into liquid Si and then cooling it gives you lumpy silicon - not a transistor. Transistors are made by putting small amounts of impurities (Phosphorus and Arsenic mostly) into the Si which changes the conductivity and the dominant charge carriers.
Sooo... Assuming that Nature really boned this one up, here's how the Scientific American version works: A thin layer of polymer (like a photoresist) is spread over the wafer, then the mask is carefuly aligned to any existing structures and placed in contact with the wafer/polymer combo. The laser is then used to cause a photochemical reaction that hardens the polymer in places where it isn't protected by the mask. The remaining soft polymer is then removed (I'm guessing there's a solvent step here - so much for the no chemical use idea) and the result is the pattern of whatever you're trying to make left in the hardened polymer. From here, you can etch, implant, or whatever other normal Si processing step you want. The main difference seems to be that the contact mask in the new process and the thin polymer layers give a higher resolution.
If anyone has more specific info or a link to a technical paper, please post it. Right now it appears that we have two major science magazines in conflict, and from my experience (I once had to build a mask generator in grad school - amazing what you can do with LabView and some old photography equipment) the SciAm version makes a heck of a lot more sense.