FinFET Technology & Basics

- overview or tutorial about the basics and essential details of FinFET technology being used in many integrated circuit technologies to reduce feature sizes and power consumption.

FinFET technology has recently seen a major increase in adoption for use within integrated circuits.

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.

This type of FET 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.

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.

FinFET basics

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

The main characteristic of the FinFET is that it has a conducting channel wrapped by a thin silicon "fin" from which it gains its name. The thickness of the fin determines the effective channel length of the device.

In terms of its structure, it typically has a vertical fin on a substrate which runs between a larger drain and source area. This protrudes vertically above the substrate as a fin.

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
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.
Feature sizes Possible to pass through the 20nm barrier previously thought as an end point.
Static leakage current Typically reduced by up to 90%
Operating speed Often in excess of 30% faster than the non-FinFET versions.

The FinFET is a technology that is used within ICs. FinFETs are not available as discrete devices. However FinFET technology is becoming more widespread as feature sizes within integrated circuits fall and there is a growing need to provide very much higher levels of integration with less power consumption within integrated circuits.

By Ian Poole

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