Solid State Electronic Devices, 7th Edition

9.5 Ultra Large-​ Scale Integration (ULSI)

In the early development of integrated circuits it was felt that the inevitable defects that occur in processing would prevent the fabrication of devices containing more than a few dozen logic gates. One approach to integration on a larger scale tried in the late 1960s involved fabricating many identical logic gates on a wafer, testing them, and interconnecting the good ones (a process called discretionary wiring). While this approach was being developed, however, radical improvements were made in device processing which increased the yield of good chips on a wafer dramatically. By the early 1970s it was possible to build circuits with many hundreds of components per chip, with reasonable yield. These ...