A new way to extend Moore’s law

ALL good things come to an end. Moore’s law—the observation that the number of transistors that can be crammed onto a chip of a given size doubles every two years—has built the modern, computerised world. But as transistors get smaller, making them smaller still gets harder. In recent years Moore’s law has begun to slow.

For all the fearsome complexity of computer chips, their basic components are simple. Transistors are nothing more than switches. To turn one on, a voltage is applied to part of it called a gate. This allows electrical current to flow through a channel between the transistor’s input and output. As transistors shrink, though, insulation breaks down and the current applying the voltage tends to leak away, reducing the gate’s ability to control the channel. One reason for this is a phenomenon called quantum tunnelling, in which the uncertainty of an electron’s position means it is sometimes found in another part of the transistor without having physically crossed there.

To try to keep things ticking along, chipmakers have been tinkering with the basic design of the transistor itself. In 2012, for example, Intel, the biggest chipmaker of the lot, introduced transistors in which the gate surrounds the channel on three sides, making it better able to impose its will.

Now IBM, a computing firm, has gone one better. In collaboration with Samsung, a Korean electronics giant, and GlobalFoundries, another big chipmaker, it has developed a new kind of transistor composed of three sheets of silicon, laid horizontally, which are surrounded completely by gate material. Such devices remain laboratory prototypes. But IBM’s engineers reckon they should permit Moore’s law to carry on until the mid 2020s.

After that, things get murkier. It is hard to improve on a design that wraps the gate entirely around the channel. If firms want to keep shrinking their products, more radical ideas will be needed. One is to use new materials, such as tubes composed of rolled-up sheets of carbon atoms, the physical properties of which permit components to be smaller. Another is to make a virtue of necessity and build devices that take advantage of quantum oddities such as tunnelling, rather than trying to resist them. A third option is to stack transistors on top of one another, keeping a chip’s area the same but increasing its volume. IBM has fingers in all of these pies, too.