ABSTRACT
The semiconductor technologies used in custom microelectronic circuits are essentially the same as those used in standard off-the-shelf ICs. Indeed, it would be strange if this was otherwise since the custom IC market is not as large as the global demand for standard parts, and hence the costs of semiconductor production lines are largely recouped from sales of the latter. There may have been a few exceptions to this, for example, very large high-tech companies engaged in the computer or instrumentation industry who require components at the leading edge of performance, but in general the normal customer for user specific ICs (USICs) will be using well-proven technology in the ICs which he or she commissions or purchases from a vendor. (Note, in this text we will use the terminology ‘‘user specific’’ for a custom IC rather than the term ‘‘application specific’’ [ASIC], which has been widely used up to now. The reason is that the term ‘‘ASIC’’ has also been applied to off-the-shelf VLSI ICs made for specific applications [see Chapter 3, Section 3.7], which are truly application specific but available to all. A further confusion in terminology is the increasing use of the term application specific standard part (ASSP) for the latter, which is much clearer, thus leaving the term ASIC as a rather inexplicit early term in this field.)
Chapter 1 looked back on the broad developments in germanium, silicon and other semiconductor technologies, from which it is evident that silicon is the dominant technology both now and in the foreseeable future. Germanium technology, with its poor temperature characteristics compared with silicon due to its lower energy gap (0.72 eV for Ge compared with 1.12 eV for Si), will not be mentioned further.
