Physical boundaries of performance: the interconnection perspective

Several interconnection issues relating to faults and reliability are reviewed. Whereas the occurrence of opens in interconnections or shorts between interconnections is well understood within conventional models of digital systems, the faults originating from the analog characteristics of signals propagating across interconnection lines (particularly long lines) is less often discussed. However, such functional faults are likely to become increasingly important, not only due to the higher frequency operation of VLSI circuits but also due to the development of advanced packaging schemes using thin film technologies and multichip modules (MCMs). Such MCMs are characterized by line lengths much longer than typically encountered within VLSI circuits. The 'digital' signal being transmitted across a long VLSI or MCM interconnection line is represented here as an 'analog' signal which must be restored to a legitimate digital signal level at the specified times imposed by flip-flops. Incorrect restoration of the 'digital' signal at the far end is treated as a fault.<>