• The Financial District


There is an old joke in the semiconductor business that the number of people predicting the death of Moore’s law doubles every two years. This refers to another prediction, made in the 1970s by Gordon Moore, one of the founders of Intel, a giant chipmaker, said The Economist today in its July 18, 2020 issue, that the number of transistors which can be crammed onto a silicon chip doubles every two years. When that number exceeded a million in the mid-1980s, some said the rate of progress had to slow down. By 2005 the number of transistors on a chip rose above 1 billion, which many thought was unsustainable. But there are now around 50 billion transistors jostling for space on some chips and producers are gunning for more.

In the current state of the art, the smallest components (transistors and diodes) made on a silicon chip are about seven nanometers (billionths of a meter) across. That is a thousandth of the diameter of a red blood cell. But problems are mounting. As components shrink, electrons start to leak from the connections between them, causing interference and unreliability. The prophets of doom have therefore returned. Once again, however, they look like they are wrong. The answer to the electron-leakage problem is better insulation between chip components. And a group of researchers in South Korea and Britain think they have the insulator required. It is called thin-film amorphous boron nitride (a-bn).

Among the firms attempting to develop graphene transistors is Samsung, a giant South Korean electronics group. Its researchers have not, however, neglected boron nitride. One of them, Hyeon-Jin Shin, working in collaboration with Hyeon Suk Shin (no relation) of the Ulsan National Institute of Science and Technology in South Korea and Manish Chhowalla of the University of Cambridge, in Britain, has come up with a form of thin-film boron nitride that lacks the regular hexagonal structure of standard white graphene—hence the description “amorphous.” Crucially, the way this substance is made may permit the integration of boron nitride into the standard chip-making process.

Thin-film materials are usually created by a process called chemical vapor deposition (cvd), and a-bn is no exception. The technique, as its name suggests, involves vaporizing the material in question, or chemicals that will react together to make it, and then depositing the result on a substrate. In the case of microelectronics, this substrate is usually a wafer of silicon. In general, for two-dimensional materials such as graphene and white graphene, cvd has to be done at above 700°C. This is too hot for existing fabs. But with thin-film a-bn, Hyeon-Jin Shin says, the temperature can be turned down as low as 400°C. That lower temperature should allow the material to be deposited directly onto silicon wafers and other substrates without having to retool the multi-billion-dollar factories, known as fabs, in which computer chips are made. This, she believes, means thin-film a-bn could be commercialized for chipmaking much faster than other two-dimensional materials. The new, amorphous films are thicker than standard white graphene, but only slightly so. At three nanometers, they are well within the size-range needed to form part of the next sceptic-busting generation of components. They are also thermally, mechanically and electrically stable. And they preserve white graphene’s wide band gap, and thus its insulating properties. Add their fab-friendliness into the calculation and their future looks bright. With luck, then, the Moore’s-law naysayers have been outmaneuvered again.

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