Mobile ion contamination in CMOS circuits: a clear and present danger

The struggle against positive mobile ionic contamination (PMIC) in integrated circuit devices continues in spite of the tremendous gains in the purity of semiconductor grade starting materials. As device geometries have decreased and levels of integration have increased, package types have multiplied. Highly sophisticated analytical techniques are required to unambiguously identify the specific ions causing a particular single transistor to fail. The monitoring of VLSI wafer manufacturing and packaging process steps to assure minimal residual positive ionic contaminants takes greater efforts as the level of device-killing contamination decreases. This tutorial presents analytical case studies for the unambiguous identification of failure-causing metal ionic contamination.