Mirco electronics

Introduction

It is a small world. Smaller and smarter electronic gizmos are making the world smaller by the day. But what is of greater interest is that the constituents of these technologies themselves are shrinking. Smaller, faster, better has become the new mantra in this field of electronics.
Microelectronics is a field that is changing at a breathtaking pace. It is virtually impossible for one to keep track of the latest technologies and research in this ever-changing field. In the past few years the latest trend in microelectronics is nanoelectronics.
"It is a staggeringly small world that is below," Richard Feynman said in his famous 1959 speech about nanotechnology, There’s Plenty of Room at the Bottom. "In the year 2000, when they look back at this age, they will wonder why it was not until the year 1960 that anybody began seriously to move in this direction." In fact, what may now inspire greater wonder is just how far nanotechnologists have come in 40 years.
In the same speech Richard Feynman said that, “The principles of physics, as far as I can see, do not speak against the possibility of maneuvering things atom by atom." It is at this scale that researchers around the world are working at. Nanoelectronics is paving the way for a new generation of devices and computers.
     This paper attempts at presenting a few of the latest and prominent researches that have been conducted and are being conducted currently in the vast field of microelectronics.

Lithography

Lithography in the field of electronics is the process which is a photography-like technique that focuses light or laser or electron beams (Electron Beam Lithography) to carve circuit patterns on silicon wafers. Lithography is akin to photography in that it uses light to transfer images onto a substrate. Silicon is the traditional substrate used in chipmaking. The silicon wafer that is coated with a light-sensitive polymer is known as a resist.  Though there are numerous methods of lithography this paper limits itself to describing Extreme Ultraviolet Lithography (EUVL) and Nanoimprint lithography.
Extreme Ultraviolet Lithography(EUVL)
Using extreme-ultraviolet (EUV) light to carve transistors in silicon wafers will lead to microprocessors that are up to 100 times faster than today's most powerful chips, and to memory chips with similar increases in storage capacity.
FIG 1 shows the process being carried out. A laser is directed at a jet of xenon gas. When the laser hits the xenon gas, it heats the gas up and creates a plasma. Once the plasma is created, electrons begin to come off of it and it radiates light at 13 nanometers, which is too short for the human eye to see.

The light travels into a condenser, which gathers in the light so that it is directed onto the mask. A representation of one level of a computer chip is patterned onto a mirror by applying an absorber to some parts of the mirror but not to others. This creates the mask. The pattern on the mask is reflected onto a series of four to six curved mirrors, reducing the size of the image and focusing the image onto the silicon wafer. Each mirror bends the light slightly to form the image that will be transferred onto the wafer. This is just like how the lenses in your camera bend light to form an image on film.
This entire process has to take place in a vacuum because these wavelengths of light are so short that even air would absorb them. Additionally, EUVL uses concave and convex mirrors coated with multiple layers of molybdenum and silicon -- this coating can reflect nearly 70 percent of EUVL light at a wavelength of 13.4 nanometers. The other 30 percent is absorbed by the mirror. Without the coating, the light would be almost totally absorbed before reaching the wafer. The mirror surfaces have to be nearly perfect; even small defects in coatings can destroy the shape of the optics and distort the printed circuit pattern, causing problems in chip function.
Nanoimprint Lithography

Silicon chips could be made more quickly and cheaply using a new technique developed by physicists in the US. Stephen Chou and colleagues at Princeton University have successfully imprinted patterns onto silicon using quartz moulds instead of the usual combination of lithography and etching. With a resolution of just 10 nm and an 'imprint time' of 250 ns, the new process could revolutionize the semiconductor industry - and keep 'Moore's Law' on track for another 25 years.
Nanoimprint lithography (NIL), a new approach to nanolithography, patterns a resist by physically deforming the resist’s shape with a mold, instead of modifying the resist’s chemical properties with radiation as in conventional lithography. NIL has demonstrated 10 nm feature size on a flat surface and the potential for low-cost and high throughput. One key issue for NIL to become a major lithography tool is to imprint on non-flat surfaces. This method employs the stamping of a hard mold into a soft material, which can be used to imprint features smaller than 10 nanometers across
 above shows the process being carried out. The team inscribed the pattern into a quartz mould using 'impact lithography', which is much cheaper and easier than the photolithography of silicon .The mould was then placed on top of a silicon wafer. A pulse
of light from a helium-neon laser - with a wavelength of 633 nm - was then fired through the mould to melt the top layer of silicon. The researchers then pressed the mould into this liquid silicon and removed it after the silicon had solidified, leaving the pattern.
Since silicon reflects more light as a liquid than it does as a solid, the team could tell when the mould needed to be removed by measuring how much of the laser pulse was reflected. The researchers also say that the mould can be used several times.

Diamond as a substitute for silicon

The microelectronic chips of the future might be made of diamond rather than silicon. Scientists in Germany may have found a way to make thin high-quality crystalline diamond films that could drive smaller, higher temperature devices than can silicon chips.
Using diamond for electronics might seem strange. Being a form of pure carbon, diamond does not normally carry a current at all. But if atoms of boron or nitrogen, for instance, are sprinkled into the lattice of carbon atoms these dopants supply mobile electrons, enabling the diamond to act as a semiconductor, like silicon.
'Diamond chips' would be invaluable in electronic devices exposed to high temperatures. Semiconducting diamond works up to temperatures of 500 °C -- silicon devices fail at around 150 °C.
Also diamond can withstand higher voltages before breaking down. So diamond devices could be made smaller than silicon ones working at the same voltage, without risk of catastrophic failure.

DNA microarrays are reshaping basic biology

A start-up firm called Affymetrix in Santa Clara, Calif., had a big idea five years ago. By adapting the methods of microprocessor manufacturing, it created microchips that contain thousands of distinct DNA probes on glass in place of transistors on silicon. 

The working principle of these microchips is as follows:
Firstly the glass is coated with a grid of tiny spots, 20 to 100 microns diameter; each spot contains millions of copies of a short sequence of DNA; and a computer keeps track of which DNA sequences are where. To make their snapshot, scientists extract from their sample cells messenger RNA (mRNA). Using enzymes, they make millions of copies of the mRNA molecules, tag them with fluorescent dye and break them up into short fragments. The tagged fragments are washed over the chip and, overnight, perform a remarkable feat of pattern matching, randomly bumping into the DNA probes fixed to the chip until they stick to one that contains a perfect genetic match. Although there are occasional mismatches, the millions of probes in each spot ensure that it lights up only if complementary mRNA is present. The brighter the spot fluoresces when scanned by a laser, the more mRNA of that kind was in the cell.
However these chips are still too expensive for widespread use and few doctors know how to interpret their results. Besides even well understood genetic diseases have innumerable possible mutations. An accurate diagnostic chip may have to include them all. 
Although it may be many years before DNA microarrays find routine use by physicians, they have already begun to change experimental biology in profound ways. They have made research vastly more productive. For example, In December 2000 a group of researchers from MIT reported that they had used microarrays for yeast to rediscover, in a matter of weeks, seven genes known to control a particular protein--research that originally took about 30 scientist-years to complete by conventional means. And the microarray experiments identified three additional genes that had been missed.
     At the moment the regulation of only a few genes in any organism is understood. If we knew the complete regulatory circuitry--how all genes are turned on or off and coordinate their activity with one another to deal with the environment--such a map would vastly increase our capacity to develop drugs for serious medical problems

Nanocomputing

Computers are becoming smaller by the day. Researchers are making breakthroughs creating methods of computing at a nano-scale.
Single Electron Memory
The single-electron memory is the latest development in the field of microelectronics called ‘single electronics’, in which electrons are shunted around circuits one by one like strollers through a maze. The electrons pass through turnstiles, hop between resting places, and as they go on their way they flip switches and perform ‘logic operations’ just like the electrical currents in ordinary computers. The difference is that the currents are minute so very little power is consumed. And because the electrons pass through the system one at a time, the electrical current is ‘granular’ -- like a trickle of sand from an hourglass, rather than a stream of liquid gushing through a lock gate.
This low-power, low-heat ‘granular’ electronics would manipulate information, not in the form of electrical pulses representing the binary digits ‘1’ and ‘0’ that encode information in today’s computers, but instead by using single electrons to represent a ‘bit’ of information. That is to say, the presence of an electron in a channel would signify a ‘1’, the absence a ‘0’. 
Some other nano computing are :

• Quantum Computers
• IBM’s Molecular Computer

Nano's

This include like:

1. Carbon Nanotubes Could Lengthen Battery Life.
2. Carbon Nanotubes Could Serve as Ultrafast Oscillators.
3. Researchers Fashion the First Single Molecule Circuit.
4. Nanotube 'Peapods' Exhibit Surprising Electronic Properties.
5. nano step toward efficient LED lighting .
6. Nano Solar Cells .

The above some topic which I have not elaborated  in post ..Beacuse I am post another post  for those topic that post will be specially related to "Nano technology"

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