During the 1990s, Scotland’s Silicon Glen looked as though it could rival other world centres for chipmaking. It could not compete with California’s Silicon Valley itself but the country looked an attractive choice to a number of Far Eastern technology companies who promised to build and expand plants there.
One-by-one they came – and one-by-one they left... Some were never even opened. Hynix built the shell for its fab close to Dunfermline, but then never moved in. Motorola bought the empty shell in 2000; but later, as Freescale Semiconductor, decided to close even its existing fab in East Kilbride, selling the Dunfermline building to an oil-rig services company, which had it demolished.
Scotland’s survivors are plants that came long before, and lived through the 1990's waves of inward investment and outflow, and which adapted to the competitive environment. Freescale closed its East Kilbride plant because the 150mm wafers it could handle could not compete with the larger wafers used by other plants around the world. National Semiconductor, on the other hand, which built its fab at Greenock in 1969, instead upgraded its fab to handle 200mm wafers.
Semefab, which was originally opened as part of General Instrument at the end of the 1960s as well, moved into making sensing micromachined devices similar to those used in phones and games machines.
Scotland’s longest-living fab, at Raytheon in Glenrothes, is moving in a different direction, using the material silicon carbide to hew out a niche for itself as more standard silicon processing moves to foundries in the Far East. The material is not just extremely hard; it will work happily at much higher temperatures than those of silicon with the added benefit of having a wider bandgap. This difference in energy levels between insulating and conducting states makes transistors and diodes made out of silicon carbide less prone to break down under high voltages than silicon counterparts.
“Six years ago, we started looking at silicon carbide,” says Paul D’Arcy, semiconductor business lead at Raytheon in Glenrothes. “We had this fab and thought, where else could we use these capabilities?”
Working mainly on specialised devices for safety-critical industries, the silicon fab at Raytheon had been able to stay productive using comparatively small 100mm (4in) wafers. “That is currently state of the art for silicon carbide,” D’Arcy says. “We are now up on 4in with silicon carbide. It is a case of ‘when not if’ for silicon carbide to go to 6in, and we have one eye on that.”
An upgrade to 6in would expand capacity in a cost-effective way. D’Arcy adds: “Most of the equipment we are bringing in is compatible with 6in processing. We have installed enough capacity to see us through the foreseeable future but I would like to have a capacity problem sooner rather than later.”
Raytheon is operating the fab as a foundry service, providing manufacturing for other companies, many of them based outside the UK; but D’Arcy says that the company sees the material as an opportunity for the power modules business based in Glenrothes, making the move to the new material more strategic: “The modules guys are actively using silicon carbide to further their aims in sectors such as aviation and in other harsh environments”.
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