Slashdot Mirror
Perv-y Material Heralds Move From Silicon
RalphTWaP writes "The Register has posted this report about the successful use of perovskite oxides as a replacement for silicon oxide in chip manufacture. As the Reg reports, the journal Science contains the original article. Best of luck getting at it though. Perhaps that kind of thing is what this other article was talking about."
The main property of this substance is that it 'meshes' well with silicon on the molecular level, as well as its unusually high electrostatic resistance. It will just (maybe) replace SiO2 insulation on silicon wafers. It is NOT, however, a Si wafer replacement, like Germanium derivatives.
As someone who works in this field I thought I might throw in my two cents.
:-). Suffice it to say that there are zillions of other interesting properties you can get from various perovskites. The famous 1-2-3 superconductor YBa2Cu3O(7-x) is a modified perovskite structure; colossal magnetoresistive materials like (La,Sr)MnO3 have been studied for use in hard drive read heads; (Pb,Zr)TiO3 is a so-called piezoelectric material-- moves when you put a voltage on it-- so you could use it for nanomachines... etc. etc. Silicon, of course, is silicon. So it's a cool thing to put them together.
[For the nosy kind of people who like qualifications: I'm a collaborator of Dr. McKee. See for example Lin et. al., "Epitaxial Growth of Pb(0.2)Zr(0.8)TiO3 on Si and etc.", Appl. Phys. Lett. 78, 2034 (ref. 27 in the Science article) on which I am an author.]
First, this technology is not enormously new. It's gotten into Science now, which makes it more high-profile, but it dates back at least to a publication in 1998 (McKee, Walker, and Chisholm, "Crystalline Oxides on Silicon: The First Five Monolayers", Phys. Rev. Lett. 81, 3014).
People have been trying to put perovskite oxides on silicon for quite some time (see, e.g., Refs. 12-15 in the PRL paper), for various reasons. [By the way, the prototypical perovskite oxide has the form ABO3, where A is a 2+ cation and B is a 4+ cation; the structure is cubic with a unit cell consisting of A at the vertices, O centered on the faces, and B in the center of the O tetrahedron. They're named after the original "perovskite" mineral, CaTiO3. It has nothing even remotely perverted about it. So get your mind out of the gutter.] One of these reasons is, as the article mentions, gate dielectrics (insulators) for field-effect transistors. A field-effect transistor consists of a conducting channel, usually made out of a semiconductor. By applying an electric field to the semiconductor you can enormously change the conductivity of the channel. However, you don't want the electrode you use to apply this field to short to the channel, so you have to put an insulator in between. There is a lower limit on the thickness of the gate insulator imposed by the desire to limit the leakage current between the gate electrode and the channel. By switching insulators, you can extend this limit.
Another use is for capacitors in DRAM. A DRAM cell works by either storing or not storing charge in a capacitor. The capacitor has to store a certain charge (~10 000 electrons) to be reliably read as on or off. If you recall the definition of capacitance Q = C V and the parallel-plate capacitor equation C = epsilon A / d (epsilon is the dielectric constant and depends on what material you put in the capacitor; A is the area; d is the spacing between plates; V is the voltage across the capacitor), you realize that there are four ways to increase Q: increase V, increase epsilon, increase A, decrease d. V is set by the operating voltages in the device, and there's a lower limit on d, again, due to leakage. You want to decrease A as much as possible to squeeze more cells on the chip. So one attractive thing to do is to switch to a material with greater epsilon. Perovskite oxides give you that opportunity.
Perhaps the most exciting use of COS at the moment is to integrate ferroelectric materials with silicon. Ferroelectrics (e.g. BaTiO3, (Pb,Zr)TiO3, both of which are perovskites) are materials with a permanent electric polarization, just like ferromagnets have a permanent magnetic polarization. You can use this permanent field to store data by switching its direction (hence the notion of a 15-year state in a processsor). One particularly attractive way to do this is to replace the gate dielectric in a field-effect transistor with a ferroelectric. Since the ferroelectric has its own built-in field, the transistor remains on or off without your putting in a gate voltage, and even when you power down the device. Hence you can set the state of a processor built from these things, walk away, and come back years later and it will still be there. These materials are also candidates for use in devices to replace Flash memory and that ilk.
I'd go on but I'm supposed to get back to work
-------------
The Register article is woefully short on details, so it's impossible for me to say whether or not a perv RAM system would be inappropriate. (name aside) I would have liked more information, but the supposed like to the journal "Science" just led back to slashdot. Then again, maybe IE is being flaky.
Yes, I'm still a junky. Are you still a bitch?
If the internal fields remain 'for 15 years' then the power consumption of the chip should hopefully be lower, since the cache shouldn't need power refresh.
:).
Caches already don't need (much) power to refresh. They're made of CMOS SRAM, which means that they only dissipate a lot of power when their state changes (ideally they'd dissipate none when the state isn't changing, but there's leakage current across gates and across junctions to the substrate).
Caches are power-hungry because any access has to a) do a tag lookup and b) propagate itself across the entire cache. There are tricks you can use to reduce the power cost of this, but this will still dominate by far over static power requirements.
Heat generation within both caches and the chip core is mainly caused by changing states and shuffling information around, not by maintaining an existing state. I've been studying this for a few years now
If the internal fields remain 'for 15 years' then the power consumption of the chip should hopefully be lower, since the cache shouldn't need power refresh.
This might also increase clock speed from heat issues, as well as no need for dead refresh cycles in the cache.
I wonder how much the new stuff costs. Hopefully its dirt (sand) cheap.
********* sig: If you don't like the law, get filthy stinking rich, and buy a better one.
I put yttrium barium copper oxide and perovskite oxide in a room and let them fight it out.
--
Poliglut
"We show that the physical and electrical structure and hence the inversion charge for crystalline oxides on semiconductors can be understood and systematically manipulated at the atomic level. Heterojunction band offset and alignment are adjusted by atomic-level structural and chemical changes, resulting in the demonstration of an electrical interface between a polar oxide and a semiconductor free of interface charge. In a broader sense, we take the metal oxide semiconductor device to a new and prominent position in the solid-state electronics timeline. It can now be extensively developed using an entirely new physical system: the crystalline oxides-on-semiconductors interface."
URLs Abstract and article (subscription may be required...)
My summary:
Oak Ridge National Lab scientsts demonstrate "crystalline oxide semiconductors", that are a combination of Ba-SrO and SrTiO3 on Silicon or BaTiO3 on Germanium. The cool thing is it looks like this will enable germanium field effect transistors that could switch faster than the 210 GHz Si-Ge transistors that IBM can now produce.
I think we're talking about sex in general
Best Slashdot Co
The "Science" link is actually to slashdot's home page...
3 /5529/468
Here's a working link...
http://www.sciencemag.org/cgi/content/abstract/29
... okay, it's not REALLY working. You have to buy access! Wasn't there a protest by scientists about this kind of thing?
- - - - -
Napster-to-go says "Fill and refill your compatible MP3 player", which is a lie. It's not MP3. It's WMA with DRM.
It's a feature. You too can have that Blue Screen of death for 15 years! Yes, you heard us right. We guarantee the last state you were in will be saved for 15 years....
At the next eco-hypocrisy-meeting, count the private jets used to get to the meeting. Should be interesting to see that
As the Reg reports, the journal Science contains the original article. Best of luck getting at it though.
I suppose it is hard to get through with the wrong link:)
Try this one instead(Reg required).
"as plurdled gabbleblotchits on a lurgid bee" - Prostetnic Vogon Jeltz. (One man's humorous is another mans flamebait)
This is nothing new. Check out MRAM. Its a rather interesting concept for incredibly high-speed non-volatile memory. You have a layered compound which can polarize - but it has a different resistance based on its polarity. You have sense lines which run through the material to measure the resistance. You have "write" lines on the top and bottom which run current over it - depending on the direction of the current flow, you can change the polarity that way. It effectively acts like a hard disk with no moving parts, and is thus incredibly fast, taking almost little power on reads and moderate power on writes. It takes no power when it is doing neither. The current research is into making it be more data-dense.
Several major companies have a lot of money invested in this, with IBM leading the pack last time I checked.
-= rei =-
"Well, then fire it up and show me what this..." (sigh)
I do want the computer to return to the previous state. I like the memory and the processor to get cleared when I reboot the computer. If they did not, my Windows uptime would soon go from 6 hours to 6 microseconds.
We're talking about breast implants, right?
Screw 3...
One of the potential advantages of this include being able to "print" the circuit while it's flat, then "corrogate" the results making a chip with a larger surface area in a small space, both miniturising the area needed on a circuit board to support the chip, and making heat transfer away from the chip more efficient.
Another is that the technology can be used on chips where the environment would naturally be flexible, which in some industrial strength situations is a necessity.
Exciting stuff indeed!
--
Racists should be sent back to where they came from