Fabricating minute devices

Abstract

I remember being impressed to hear that the first university mainframe computer that I used had 1 megabyte of 'core' memory. Less than 15 year later I can write this article using a diminutive Macintosh desktop computer with the same amount of memory, and only eight silicon chips are needed to provide it. Many factor led to this astonishing advance, one of which is the ability to fabricate ever smaller devices and pack a higher density of them onto an integrated circuit. The size of the minimum feature on a typical chip has halved every four years and is now below 1μm. Advanced research is aimed at developing silicon MOSFETs whose crucial dimension, the length of the gate, is only 0.1μm. Several laboratories fabricate devices in GaAs with gates of half this length (50 nm) – only 100 lattice spacings. I shall explain briefly how these tiny structures are drawn and imprinted on the semiconductor, illustrating the techniques with devices made at Glasgow University.