New Transistor will Built Atom by Atom

A more precise manufacturing method will help as electronics shrink ever smaller.

Chip stack: This illustration shows the layers that make up a gate in a 22-nanometer transistor. The white balls on the bottom are silicon. The light blue balls in the middle are silicon dioxide molecules; the larger turquoise balls higher up are hafnium oxide; and the yellow balls are nitrogen atoms.
Credit: Applied Materials.
Applied Materials, the world's leading supplier of manufacturing equipment to chipmakers, has announced a new system for making one of the most critical layers of the transistors found in logic circuits.
Applied Materials' new tool, announced at the Semicon West conference in San Francisco on Tuesday, deposits a critical layer in transistors one atom at a time, providing unprecedented precision.
As chipmakers scale transistors down to ever-smaller sizes, enabling speedier and more power-efficient electronics, atomic-scale manufacturing precision is a growing concern. The first chips with transistors just 22 nanometers in size are going into production this year, and at that size, even the tiniest inconsistencies can mean that a chip intended to sell at a premium must instead be used for low-end gadgetry.
Transistors are made up of multiple layers: an active silicon material topped with an interfacing layer and then a layer of a material called a dielectric, which makes up the "gate" that switches the transistor on and off.
Applied Materials sells equipment for depositing these layers, called the gate stack, on top of silicon wafers. In the switch from today's 32-nanometer to the next generation of 22-nanometer transistors, it's become trickier to make the gate. The interface and dielectric layers both have to get thinner, and the behavior of the layers can be affected by tiny flaws where the materials touch. And as the layers get thinner, tiny flaws can be magnified even more than in larger transistors made from thicker layers.
Manufacturing accuracy will be even more important in the next-generation three-dimensional transistors that chipmaker Intel will begin producing later this year. In these devices, the active area is a raised strip that the interface and gate layers contact on three sides. This increased area of contact helps these devices perform better, but it also means an increased vulnerability to flaws.
The process uses atomic-layer deposition, or ALD, which lays down a single atomic layer of the dielectric at a time. This method is more expensive, but it's become necessary, says Atif Noori, global product manager of Applied Materials' ALD division. For the heart of the transistor—the gate—to work, "you have to make sure you're putting all the atoms right where you want them."
One source of inconsistencies in microchips is exposure to air. In Applied Materials' new tool, the entire process of depositing the gate stack is done in a vacuum, one wafer at a time. Making the gate stack entirely under a vacuum also leads to a 5 to 10 percent increase in the speed at which electrons travel through the transistor; this can translate into power savings or faster processing. Ordinarily, there's significant variation in the amount of power it takes to turn on a given transistor on a chip; manufacturing under a vacuum tightens that distribution by 20 to 40 percent.

Soft Memory Chip have new windows for biocompatible electronics

Conventional electronics are typically made of rigid, brittle materials and don't function well in a wet environment. "Our memory device is soft and pliable, and functions extremely well in wet environments -- similar to the human brain," says researcher Michael Dickey. Credit: Michael Dickey, North Carolina State University.

Researchers from North Carolina State University have developed a memory device that is soft and functions well in wet environments – opening the door to a new generation of biocompatible electronic devices.
"We've created a memory device with the physical properties of Jell-O," says Dr. Michael Dickey, an assistant professor of chemical and biomolecular engineering at NC State and co-author of a paper describing the research.
Conventional electronics are typically made of rigid, brittle materials and don't function well in a wet environment. "Our memory device is soft and pliable, and functions extremely well in wet environments – similar to the human brain," Dickey says.

Researchers have created a memory device with the physical properties of Jell-O, and that functions well in wet environments. Credit: Michael Dickey, North Carolina State University

Prototypes of the device have not yet been optimized to hold significant amounts of memory, but work well in environments that would be hostile to traditional electronics. The devices are made using a liquid alloy of gallium and indium metals set into water-based gels, similar to gels used in biological research.

The device's ability to function in wet environments, and the biocompatibility of the gels, mean that this technology holds promise for interfacing electronics with biological systems – such as cells, enzymes or tissue. "These properties may be used for biological sensors or for medical monitoring," Dickey says.

The individual components of the "mushy" memory device have two states: one that conducts electricity and one that does not. These two states can be used to represent the 1s and 0s used in binary language. Most conventional electronics use electrons to create these 1s and 0s in computer chips. The mushy memory device uses charged molecules called ions to do the same thing. Credit: Michael Dickey, North Carolina State University.

The device functions much like so-called "memristors," which are vaunted as a possible next-generation memory technology. The individual components of the "mushy" memory device have two states: one that conducts electricity and one that does not. These two states can be used to represent the 1s and 0s used in binary language. Most conventional electronics use electrons to create these 1s and 0s in computer chips. The mushy memory device uses charged molecules called ions to do the same thing.

In each of the memory device's circuits, the metal alloy is the circuit's electrode and sits on either side of a conductive piece of gel. When the alloy electrode is exposed to a positive charge it creates an oxidized skin that makes it resistive to electricity. We'll call that the 0. When the electrode is exposed to a negative charge, the oxidized skin disappears, and it becomes conducive to electricity. We'll call that the 1.
Normally, whenever a negative charge is applied to one side of the electrode, the positive charge would move to the other side and create another oxidized skin – meaning the electrode would always be resistive. To solve that problem, the researchers "doped" one side of the gel slab with a polymer that prevents the formation of a stable oxidized skin. That way one electrode is always conducive – giving the device the 1s and 0s it needs for electronic memory.
Provided by North Carolina State University (news : web)

New Flexible LED ( Latest Small LED )

Researchers create a smaller, flexible LED

                                                                                   

University of Miami professor at the College of Engineering, Jizhou Song, has helped design an light-emitting diode (LED) light that uses an array of LEDs 100 times smaller than conventional LEDs. The new device has flexibility, maintains lower temperature and has an increased life-span over existing LEDs. The findings are published online by the Proceedings of the National Academy Incandescent bulbs are not very efficient, most of the power they use is converted into heat and only a small fraction of the power gets converted to light. Since LEDs reduce energy waste and present an alternative to conventional bulbs.
In this study, the scientists focused on improving certain features of LED lights, like size, flexibility and temperature. Song's role in the project was to analyze the thermal management and establish an analytical model that reduces the temperature of the device.
"The new model uses a silicon substrate, novel etching strategies, a unique layout and innovative thermal management method," says Song, co-author of the study. "The combination of these manufacturing techniques allows the new design to be much smaller and keep lower temperatures than current LEDs using the same electrical power."
In the future, the researchers would also like to make the device stretchable, so that it can be used on any surface, such as deformable display monitors and biomedical devices that adapt to the curvilinear surfaces of the human body.

More information: The PNAS paper is titled 'Unusual Strategies for Using InGaN Grown on Silicon (111) for Solid State Lighting.' Published online before print June 10, 2011, doi: 10.1073/pnas.1102650108
Abstract

Properties that can now be achieved with advanced, blue indium gallium nitride light emitting diodes (LEDs) lead to their potential as replacements for existing infrastructure in general illumination, with important implications for efficient use of energy. Further advances in this technology will benefit from reexamination of the modes for incorporating this materials technology into lighting modules that manage light conversion, extraction, and distribution, in ways that minimize adverse thermal effects associated with operation, with packages that exploit the unique aspects of these light sources. We present here ideas in anisotropic etching, microscale device assembly/integration, and module configuration that address these challenges in unconventional ways. Various device demonstrations provide examples of the capabilities, including thin, flexible lighting “tapes” based on patterned phosphors and large collections of small light emitters on plastic substrates. Quantitative modeling and experimental evaluation of heat flow in such structures illustrates one particular, important aspect of their operation: small, distributed LEDs can be passively cooled simply by direct thermal transport through thin-film metallization used for electrical interconnect, providing an enhanced and scalable means to integrate these devices in modules for white light generation.
Provided by University of Miami (news : web)