FinFET Transistor Technology

FinFET transistor technology is being used in many areas of IC technology where the 3D fins provide added density for same feature size.

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FinFET technology has recently seen a major increase in adoption for use within integrated circuits. Compared to the more usual planar technology, FinFET transistor technology offers some significant advantages in IC design.

The FinFET technology promises to provide the deliver superior levels of scalability needed to ensure that the current progress with increased levels of integration within integrated circuits can be maintained.

The FinFET offers many advantages in terms of IC processing that mean that it has been adopted as a major way forwards for incorporation within IC technology.

FinFET background

FinFET technology has been born as a result of the relentless increase in the levels of integration. The basic tenet of Moore's law has held true for many years from the earliest years of integrated circuit technology. Essentially it states that the number of transistors on a given area of silicon doubles every two years.

Some of the landmark chips of the relatively early integrated circuit era had a low transistor count even though they were advanced for the time. The 6800 microprocessor for example had just 5000 transistors. Todays have many orders of magnitude more.

To achieve the large increases in levels of integration, many parameters have changed. Fundamentally the feature sizes have reduced to enable more devices to be fabricated within a given area. However other figures such as power dissipation, and line voltage have reduced along with increased frequency performance.

There are limits to the scalability of the individual devices and as process technologies continued to shrink towards 20 nm, it became impossible to achieve the proper scaling of various device parameters. Those like the power supply voltage, which is the dominant factor in determining dynamic power were particularly affected. It was found that optimising for one variable such as performance resulted in unwanted compromises in other areas like power. It was therefore necessary to look at other more revolutionary options like a change in transistor structure from the traditional planar transistor.

One of the key issues is that as technologies use smaller feature sizes, the source and the drain of the MOS devices used encroach into the channel, making it easier for leakage current to flow between them and also making it very difficult to turn the transistor off completely.

FinFET basics

FinFET technology takes its name from the fact that the FET structure used looks like a set of fins when viewed.

In fact the FinFET gained its name from Profs. Chenming Hu, Tsu-Jae King-Liu and Jeffrey Bokor at the University of California, Berkeley who were the first to coin the term as a result of the shape of the structure.

FinFETs are 3d structures that rise above the substrate and resemble a fin. The 'fins' form the source and drain, effectively and in this way they enable more volume than a traditional planar transistor for the same area. The gate wraps around the fin, and this gives more control of the channel as there is sufficient length for the control. Also as the channel has been extended there is very little current to leak through the body when the device is in the 'off' state. This also allows the use of lower threshold voltages and it results in better performance and lower power dissipation.

The gate orientation is at right angles to the vertical fin. And to traverse from one side of the fin to the other it wraps over the fin, enabling it to interface with three side of the fin or channel.

This form of gate structure provides improved electrical control over the channel conduction and it helps reduce leakage current levels and overcomes some other short-channel effects..

The term FinFET is used somewhat generically. Sometimes it is used to describe any fin-based, multigate transistor architecture regardless of number of gates.

Advantages of FinFET technology

There are many advantages to IC manufacturers of using FinFETs.

FinFET Advantages
Parameter Details
Feature sizes Possible to pass through the 20nm barrier previously thought as an end point.
Power Much lower power consumption allows high integration levels. Early adopters reported 150% improvements.
Operating voltage FinFETs operate at a lower voltage as a result of their lower threshold voltage.
Operating speed Often in excess of 30% faster than the non-FinFET versions.
Static leakage current Typically reduced by up to 90%

FinFET technology is being adopted in a variety of forms by IC manufacturers who need to increase the density of their ICs without using such small feature sizes that the device performance falls. As a result, FinFET transistor technology has enabled the development in IC technology to continue to follow Moore’s law.

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