Electromechanical Switches Could Reduce Future Computers' Cooling Needs

Earthquake Retrofit writes "Science Daily is reporting that researchers at Case Western Reserve University have taken the first step to building a computer capable of operating in extreme heat. Te-Hao Lee, Swarup Bhunia and Mehran Mehregany have made electromechanical switches — building blocks of circuits — that can take twice the heat that would render electronic transistors useless. 'The group used electron beam lithography and sulfur hexafluoride gas to etch the switches, just a few hundred nanometers in size, out of silicon carbide. The result is a switch that has no discernable leakage and no loss of power in testing at 500 degrees Celsius. A pair of switches were used to make an inverter, which was able to switch on and off 500,000 times per second, performing computation each cycle. The switches, however, began to break down after 2 billion cycles and in a manner the researchers do not yet fully understand. ... Whether they can reach the point of competing with faster transistors for office and home and even supercomputing, remains to be seen. The researchers point out that with the ability to handle much higher heat, the need for costly and space-consuming cooling systems would be eliminated.'"

Comments

Steampunk

[russotto]

Miniaturized relays are interesting, but an inverter which operates at 0.0005 Ghz is less interesting. Somehow I don't think we'll be seeing this replace electronics anytime soon. (well, except in lithium battery microcontrollers :-) ). Although it would be interesting technology for a steampunk novel.

Re:Steampunk

[msauve]

"an inverter which operates at 0.0005 Ghz is less interesting. Somehow I don't think we'll be seeing this replace electronics anytime soon."

As you alluded to, there are billions of microcontrollers out there running at less than 0.5 MHz. Heck, the good ol' Mostek 6502 ran at 1 MHz, and started an industry (KIM-1, Commodore PET, Apple ][, etc.) This is still in the research stage, but even at the current speeds, useful processors could be built (but apparently not last very long), especially since this would open new markets where traditional semiconductor gates won't function.

But, even short of a full processor, there could be uses for logical applications (gate arrays).

Relays are back!

[John Hasler]

I tried to tell them that tubes and transistors were just a fad. Relays were good enough for the Z4 and they're good enough for us. These kids and their newfangled gadgets...

Impervious to electromagnetic radiation

[Alain Williams]

Presumably (says I having read the article but not knowing much more about this) the mechanical switches:

• will not generate electromagnetic radiation. This will eliminate the need for tempest protection, ie the bad guys can't evesdrop by picking up radio waves — although I wonder if they could ''listen'' to the clacking of the relays
• will not be succeptible to destruction by EMP (electromagnetic pulse)

Both attributes that the military would like.

Re:Impervious to electromagnetic radiation

[MattskEE]

Presumably (says I having read the article but not knowing much more about this) the mechanical switches:

How prescient ;-)

No, when they mention radiation in the article it's because these devices are radiation-hard, i.e. they will last a long time in a radioactive environment such as many satellites fly in. Standard silicon CMOS devices on the other hand degrade very quickly because charged particles get trapped in the gate oxide changing the gate threshold, degrading performance, and then eventually killing the device. The silicon crystal itself is more vulnerable to defects from radiation, which increases channel resistance, again degrading performance and killing the device.

The SiC MEMs devices are more robust because SiC is more robust at high temperatures and radiation filled environments, plus as a primarily mechanical system rather than electrical, it will probably be more tolerant to crystal defects.

In a computer this will emit just as much electromagnetic radiation as a silicon chip because the radiation comes from the flow of current being turned on and off. It doesn't matter one bit if you do it with a vacuum tube, BJT, MOSFET, or MEMs device, you will get electromagnetic radiation.

It may be more robust to EMP than a Si-CMOS device, but it will still be vulnerable to contact degradation when an EMP causes breakdown of the air or vacuum dielectric.

The military does love the idea of MEMs switches, more so for radar/comms, but they got burned bad after DARPA and DOD agencies funded 10's of millions, or probably more, in R&D with no useful results. The main problem with MEMs switches has always been reliability, which you will see is also a problem in the MEMs devices being promoted in this article.

Energy conversion to heat still exists

[Technician]

There are two sources of heat in modern semiconductor CPU's.

One is leakage, the heat generated by current times resistance squared in transistors that are off.

The higher current that is related to the clock speed is the heat generated by transistors that are turned on using the same current times resistance squared.

To keep the on current at a bare minimum, transistors are paired with one on and one off so the current through the pair should be zero except for leakage. The current flows when they are clocked and the capacitance (stored voltage) of the wire between transistors and gate capacitance of the MOSFET it drives supplies current during switching.

How does this no heat switch avoid the current of switching the capacitance between the switches. From what I can tell is this part is able to handle higher temperatures. I do not see it as a no power (no heat generated) device.

Silicon Nitride has much higher resistance than most metals. Due to the resistance and temperature resistance, it is often used as hot surface ignition in gas appliances. Current through the switches will create heat. It is unavoidable.

At it's current speed of 0.000.5 GHZ clock speed, I can believe the current power consumption is very low. How does this stack up to an Atom CPU clocked at 0.000.5 GHZ?

Quit talking about gigahertz

[AdamHaun]

Nobody's going to use this for desktop CPUs. The whole point is that the switches work at 500 degrees C, where silicon doesn't. This technology would be used for embedded control in extremely hostile environments, where 500 kHz would be just fine. The article names the inside of a jet engine and the surface of Venus as examples.

These would be great for high-end test equipment

[smellsofbikes]

I do test circuit hardware design and we use standard relays all over the board, for switching bits of circuitry into and out of contact with an integrated circuit we're testing. We use mechanical relays because of the same reasons they say: zero leakage current when they're open, and extremely low resistance when they're closed, which semiconductor switches just can't equal. The problem is the lifetime of the relays, so we have to socket them all (which, when you're building a board with 500 relays on it, is a significant time and money sink) and replace them pretty often on high-running parts (some of our parts have been in high-volume production for 20 years.) Plus they're big and take up the majority of the board. Having a device that's tiny and can last a billion cycles would be completely awesome.

NASA

[pablo_max]

Seems like something interesting for planetary exploration where standard CPUs on a probe would be rendered useless in a matter of hours. Much as the equipment sent to Venus.