3-D TRANSISTORS: REDEFIGNING THE TRANSISTOR

Researchers from Purdue and Harvard universities have created a new type of transistor made from a material that could replace silicon and have a 3-D structure instead of conventional flat computer chips. The traditional flat two-dimensional “planar” gate is replaced with a thin three-dimensional silicon fin that rises up vertically from the silicon substrate.

 

Left shows traditional planar transistor. Right shows our 3d transistor.

The approach could enable engineers to build faster, more compact and efficient integrated circuits and lighter laptops that generate less heat than today’s. The transistors contain tiny nanowires made not of silicon, like conventional transistors, but from a material called indium-gallium-arsenide.

Why called 3d?

          These are called finFET’s for fin field-effect-transistors. The distinguishing characteristic of the FinFET is that the conducting channel is wrapped by a thin silicon “fin”, which forms the gate of the device. The thickness of the fin (measured in the direction from source to drain) determines the effective channel length of the device.

 

It’s actually a tri-gate transistor. The traditional flat two-dimensional “planar” gate is replaced with a thin three-dimensional silicon fin that rises up vertically from the silicon substrate. It’s necessary to sustain Moore’s Law–doubling the number of transistors on a silicon device every two years. As device dimensions become prohibitively small, cramming in transistors in the traditional two-dimensional fashion becomes impossible. So, 3D or vertical transistors become necessary. And Intel isn’t just talking about this theoretically, it’s going to manufacture chips based on these transistors.

The fins are made not of silicon, like conventional transistors, but from a material called indium-gallium-arsenide. Called FinFETs, for fin field-effect-transistors, researchers from around the world have been working to perfect the devices as potential replacements for conventional transistors.

Working:

Actually transistors contain critical components called gates, which enable the devices to switch on and off and to direct the flow of electrical current. In today’s chips, the length of these gates is about 45 nanometers, or billionths of a meter.

The semiconductor industry plans to reduce the gate length to 22 nanometers by 2015. However, further size reductions and boosts in speed are likely not possible using silicon, meaning new designs and materials will be needed to continue progress. Creating smaller transistors also will require finding a new type of insulating layer essential for the devices to switch off. As gate lengths are made smaller than 22 nanometers, the silicon dioxide insulator used in conventional transistors fails to perform properly and is said to “leak” electrical charge.

This 22nm transistor is possible because of its complex 3 dimensional combination of transistor upon transistor. Implies here we have to consider the transistor as a set of transistors instead of a single transistor which can be worked efficiently in the bunch. The 22nm transistor performs better and uses less energy than the current cutting edge 32nm transistor. The first processor using this 22nm 3D technology will be called Ivy Bridge.

The fin like design is critical to preventing current leakage, in part because the vertical structure can be surrounded by an insulator, whereas a flat device has the insulator on one side only.

Above picture gives the perfect example of what has been explained above.

Courtesy: news from net, science daily and few famous websites.

Posted by

Gopi chand ( MGIT ECE 4th year)

 

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