High, not flat: nanowires for a new chip architecture

Feb 02, 2010
Scheme of a silicon wafer with novel vertical transistors made out of silicon nanowires

Nowadays, a myriad of silicon transistors are responsible to pass on the information on a microchip. The transistors are arranged in a planar array, i.e. lying flat next to each other, and have shrunk down already to a size of only about 50 nanometers. Further miniaturization of transistors with a planar structure will soon come to an end due to fundamental physical limits. Still, even smaller transistors are desirable in order to continuously improve their functions while reducing the cost of the electronics.

Currently, researchers are working hard to find new approaches to overcome the physical limits on downscaling and integration of microchips. One such concept is to fabricate a completely new transistor architecture in three-dimensions. In this concept, instead of arranging them flat on the substrate the are turned by 90 degrees so that they stick out of the chip substrate like tiny columns. In this way, numerous vertical transistors could be built on the area normally occupied by only one planar transistor. This would finally be the step from micro to nanoelectronics.

The fabrication of vertical silicon nanowire arrays has already been reported. Yet there needs to be a more thorough research into the of silicon nanowires in order to be able to build reliable transistors for a new generation of microchips. Unlike conventional transistors, the current flow in these column-like transistors will be vertical, and they will be smaller and more energy-saving than today. Last but not least, there are high hopes to fabricate extremely efficient using silicon nanowires.

The Max Planck researchers in Halle produce monocrystalline silicon nanowires which are particularly suitable as components for microchips. At the FZD’s center, foreign atoms known as ‘dopants’ are implanted into the nanowires. The dopants occupy lattice sites of the host semiconductor increasing the electrical conductivity and the current flow through the semiconductor. Selective implantation of different dopants can change the polarity of the charge carriers in a transistor leading to the switching of the current flow. The planar silicon technology is well developed; however, this is not true for silicon nanostructures. “First, we analyzed wires with a diameter of 100 and 300 nanometers in length. But what we aim at are wires with a diameter of a few atoms only, as well as wires where individual atoms are strung together. We intend to closely characterize their behavior in materials and want to find out how their electrical properties can be tailored for application in nanoelectronics, e.g. for new field-effect transistors,” say FZD physicists Dr. Reinhard Koegler and Dr. Xin Ou.

The nanowires were investigated in Rossendorf using a technique (Scanning Spreading Resistance Microscopy, SSRM) that usually measures the position- dependent electrical resistivity in a specially-prepared two-dimensional cross-section of the nanowire. The resistivity is related to the atomic concentration of the dopants. In the current work, the researchers have found that the dopants in a silicon nanowire, namely boron and phorphorus, do not stay where they are expected, but drift to the surface of the nanowire where they become partially inactive and can no longer contribute to the . Up until now scientists were lacking an appropriate technique to visualize and quantify the consequences of an unequal distribution of dopants at the nanoscale. Chip designers have to pay attention to the newly found results if are to be applied for vertical transistors in the future.

Explore further: Study sheds new light on why batteries go bad

More information: “Carrier Profiling of Individual Si Nanowires by Scanning Spreading Resistance Microscopy“, Nano Letters 2010,10,171-175,
DOI:10.1021/nl903228s

Source: Forschungszentrum Dresden Rossendorf

5 /5 (8 votes)

Related Stories

Nanowires key to future transistors, electronics

Nov 26, 2009

(PhysOrg.com) -- A new generation of ultrasmall transistors and more powerful computer chips using tiny structures called semiconducting nanowires are closer to reality after a key discovery by researchers ...

New material for nanoscale computer chips

Aug 17, 2009

Nanochemists from the Chinese Academy of Sciences and Nano-Science Center, Department of Chemistry at University of Copenhagen have developed nanoscale electric contacts out of organic and inorganic nanowires. ...

Growing Europe's nanowires

Dec 16, 2009

(PhysOrg.com) -- European researchers have developed state-of-the-art nanowire 'growing' technology, opening the way for faster, smaller microchips and creating a promising new avenue of research and industrial ...

Recommended for you

For electronics beyond silicon, a new contender emerges

30 minutes ago

Silicon has few serious competitors as the material of choice in the electronics industry. Yet transistors, the switchable valves that control the flow of electrons in a circuit, cannot simply keep shrinking ...

Making quantum dots glow brighter

2 hours ago

Researchers from the University of Alabama in Huntsville and the University of Oklahoma have found a new way to control the properties of quantum dots, those tiny chunks of semiconductor material that glow ...

The future face of molecular electronics

2 hours ago

The emerging field of molecular electronics could take our definition of portable to the next level, enabling the construction of tiny circuits from molecular components. In these highly efficient devices, ...

Study sheds new light on why batteries go bad

Sep 14, 2014

A comprehensive look at how tiny particles in a lithium ion battery electrode behave shows that rapid-charging the battery and using it to do high-power, rapidly draining work may not be as damaging as researchers ...

Moving silicon atoms in graphene with atomic precision

Sep 12, 2014

Richard Feynman famously posed the question in 1959: is it possible to see and manipulate individual atoms in materials? For a time his vision seemed more science fiction than science, but starting with groundbreaking ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

dirk_bruere
not rated yet Feb 05, 2010
Looks like graphene is the real future
maxcypher
not rated yet Feb 06, 2010
Actually, these are silicon nanowires.