Nanocircuitry

Nanocircuits are electrical circuits on the scale of nanometers. One nanometer is equal to 10^-9 meters or a row of 10 hydrogen atoms. With circuits becoming smaller, they are able to fit more on a computer chip. Thus, they will be able to perform more complex functions using less power and at a faster speed. Nanocircuits are organized into three different parts: transistors, interconnections, and architecture, all dealt within the nano scale.

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Production Methods

One of the most fundamental concepts to understanding nanocircuits is the formulation of Moore’s Law. This concept arose when Intel co-founder Gordon Moore became interested in the cost of transistors and trying to fit more onto one chip. It relates that the number of transistors that can be fabricated on a silicon integrated circuit—and therefore the computing speed of such a circuit—is doubling every 18 to 24 months.¹ The more transistors one can fit on a circuit, the faster the computer will be. This is why scientists and engineers are working together to produce these nanocircuits so millions and perhaps even billions of transistors will be able to fit onto a chip. Despite how good this may sound, there are many problems that arise when so many transistors are packed together. With circuits being so tiny, they tend to have more problems than larger circuits, more particularly many defects. Nanoscale circuits are more sensitive to temperature changes, cosmic rays and electromagnetic interference than today's circuits.² As they pack more transistors onto a chip, phenomena such as stray signals on the chip, the need to dissipate the heat from so many closely packed devices, and the difficulty of creating the devices in the first place will halt or severely slow progress. ³ Many believe the market for nanocircuits will reach equilibrium around 2015. At this time they believe the cost of a fabrication facility may be as much as $200 billion. There will be a time when the cost of making circuits even smaller will be too much, and the speed of computers will reach a maximum. For this reason, many scientists believe that Moore’s Law will not hold forever and will soon reach a peak.

In producing these nanocircuits, there are many aspects involved. The first part of their organization begins with transistors. As of right now, most electronics are using silicon-based transistors. Transistors are an integral part of circuits as they control the flow of electricity and transform weak electrical signals to strong ones. They also control electric current as they can turn it on off, or even amplify signals. Circuits now use silicon as a transistor because it can easily be switched between conducting and nonconducting states. However, in nanoelectronics, transistors might be organic molecules or nanoscale inorganic structures.⁴ Semiconductors, which are part of transistors, are also being made of organic molecules in the nano state.

The second aspect of nanocircuit organization is interconnection. This involves logical and mathematical operations and the wires linking the transistors together that make this possible. In nanocircuits, nanotubes and other wires as narrow as one nanometer are used to link transistors together. Nanowires have been made from carbon nanotubes for a few years. Until a few years ago, transistors and nanowires were put together to produce the circuit. However, scientists have been able to produce a nanowire with transistors in it. In 2004, Harvard University nanotech pioneer Charles Lieber and his team have made a nanowire—10,000 times thinner than a sheet of paper—that contains a string of transistors.⁵ Essentially, transistors and nanowires are already pre-wired so as to eliminate the difficult task of trying to connect transistors together with nanowires.

The last part of nanocircuit organization is architecture. This has been explained as the overall way the transistors are interconnected, so that the circuit can plug into a computer or other system and operate independently of the lower-level details.⁶ With nanocircuits being so small, they are destined for error and defects. Scientists have devised a way to get around this. Their architecture combines circuits that have redundant logic gates and interconnections with the ability to reconfigure structures at several levels on a chip.⁷ The redundancy lets the circuit identify problems and reconfigure itself so the circuit can avoid more problems. It also allows for errors within the logic gate and still have it work properly without giving a wrong result.

Potential Applications and Breakthroughs

Scientists in India have recently developed the world’s smallest transistor which will be used for nanocircuits. The transistor is made entirely from carbon nanotubes. Nanotubes are rolled up sheets of carbon atoms and are more than a thousand times thinner than human hair.⁸ Normally circuits use silicon-based transistors, but these will soon replace those. The transistor has two different branches that meet at a single point, hence giving it a Y shape. Current can flow throughout both branches and is controlled by a third branch that turns the voltage on or off. This new breakthrough can now allow for nanocircuits to hold completely to their name as they can be made entirely from nanotubes. Before this discovery, logic circuits used nanotubes, but needed metal gates to be able to control the flow of electrical current.

Arguably the biggest potential application of nanocircuits deals with computers and electronics. Scientists and engineers are always looking to make computers faster. Some think in the nearer term, we could see hybrids of micro and nano: silicon with a nano core—perhaps a high-density computer memory that retains its contents forever.⁹ Unlike conventional circuit design, which proceeds from blueprint to photographic pattern to chip, nanocircuit design will probably begin with the chip—a haphazard jumble of as many as 1024 components and wires, not all of which will even work—and gradually sculpt it into a useful device.¹⁰ Instead of taking the traditional top-down approach, the bottom-up approach will probably soon have to be adopted because of the sheer size of these nanocircuits. Not everything in the circuit will probably work because at the nano level, nanocircuits will be more defective and faulty because of their compactness. Scientists and engineers have created all of the essential components of nanocircuits such as transistors, logic gates and diodes. They have all been constructed from organic molecules, carbon nanotubes and nanowire semiconductors. The only thing left to do is find a way to eliminate the errors that come with such a small device and nanocircuits will become a way of all electronics. However, eventually there will be a limit as to how small nanocircuits can become and computers and electronics will reach their equilibrium speeds.

Existing Products

Intel has become a leader in the computer industry when it comes to building smaller and faster microchips. One of their new products is the Intel Core2 Duo Processor. Although it is based on microarchitecture, it uses nanocircuitry in its design. They are up to 40% faster than microprocessors out now and are even more energy-efficient. Currently, the core duo contains over 150 million transistors, very characteristic of a nanocircuit which holds millions of transistors as well. The manufacturing process 65 nm, makes it a true nanocircuit. This is one of the leading processors for computers equipped for gaming and other high definition applications. Recently, Intel released information about a 45nm processor that will be released in 2007, which is slightly smaller than the 65 nm processor used now.

Economic Impact

With the vast improvements in reducing the size of circuits, comes a rising cost to produce these nano components. Scientists believe that one day a fabrication facility for making nanocircuit could cost as much as over $200 billion. The increased cost comes from the difficulty of producing such circuits as they take more time and effort than circuits today. The fabrication plant will create a raw nanocircuit—billions on billions of devices and wires whose functioning is rather limited. From the outside it will look like a lump of material with a handful of wires sticking out.¹¹ Eventually the theory of Moore’s Law will have to reach equilibrium with the fabrication methods currently used. Circuits will only be able to be so fast and small without creating any severe problems. The cost for producing even better nanocircuits will increase further as more money will be needed to develop new fabrication methods and ways of designing faster, better nanocircuits. Until that time, companies like Intel will continue to thrive in the nano business with their promises of their chip being the fastest and better than their counterpart. Nanocircuits may still have their problems, but that will not stop companies from mass producing them in order to become the most technologically advanced company with the fastest product.

See also

• Moore's Law
• Nanotechnology
• History of nanotechnology
• List of nanotechnology applications
• Implications of nanotechnology

References

1 Stokes, Jon. ”Understanding Moore's Law","ars technica", 2003-02-20. Retrieved on March_23, 2007.

2 Patch, Kimberly. “Design handles iffy nanocircuits","TRN",2003-03-26. Retrieved on March_23, 2007.

3 Patch, retrieved on March_23, 2007.

4 Eds. Scientific American, Understanding Nanotechnology (New York: Warner Books, 2002) p.93.

5 Pescovitz, David.“Nanowires with built-in transistors","boing boing", 2004-07-01. Retrieved on March_23, 2007.

6 Eds. Scientific American, 93.

7 Patch, retrieved on March_23, 2007.

8 “Indians make the world’s tiniest transistor","SiliconIndia", 2005-09-06. Retrieved on March_23, 2007.

9 Eds. Scientific American, 93.

10 Eds. Scientific American, 94.

11 Eds. Scientific American, 101.