Editorial MAY/JUNE 1983

There seems to be universal agreement that one of the most important current trends in the integrated circuit industry is the enormous boom in the market for semi-custom design of products. In recognition of this, Microelectronics Journal has devoted this special issue to the subject.

Although it is likely that most people think of semi-custom as the design of inter- connection layers for gate arrays and ULAs, it is worth remembering that the term also covers standard cell designs and bipolar circuits. Although at first sight the full mask set requirement for a standard cell approach seems almost prohibitive, the real trade-offs between circuit performance, area utilisation and lead time in relation to cost are much less obvious. These points and others, are made by both Shenton and Pyne in their respective views of futu re trends.

Two further papers in this issue concentrate on the specific features of modern gate array devices while Walker and King address the problem of testing which may easily be overlooked in the semi-custom design process which tends to be sensitive to deadlines.

When digital and analogue functions are to be mixed, chip architecture becomes critical and this is the subject of a paper by Kemp. The more general subject of analogue design is covered by a comprehensive tutorial paper by Bray. While not totally original, this may be a useful survey for those who need to become involved in what is fast becoming a last cut - the detailed design of analogue circuits.

A recurring theme in any discussion of semi-custom design, perhaps even more than for IC design in general, is the availability of design aids. It is essential that designers of custom circuits have access to a well integrated set of tools from function specification through simulation to mask layout. All too often this is not the case although many supplies of uncommitted devices have developed reasonably efficient systems for their own particular requirements. The present trend away from main-frame based software suites and turn-key graphics systems towards micro-based workstations with design software sharing a common data base is, like most innovations, confusing in its proliferation at the moment.

Although workstations are appearing in great profusion, comparison between them is very difficult, if not impossible. It is to be hoped that, in a reasonably short time, some commonality can be established, so as to allow users to select these products in a basis of true comparison and cost effectiveness for the purpose required.

Finally, as an early warning for our next special issue in December, I would like to solicit papers on silicon on insulator technology. This will cover such topics as silicon-on-sapphire, recrystallised poly-silicon, porous oxidation, implanted oxygen etc. Contributions or suggestions will be welcomed as always.

JOHN BUTCHER