Polysilicon electromigration sensor which can detect and monitor

Abstract

A polysilicon sensor is described which can be incorporated onto a silicon wafer containing integrated circuits for the purpose of detecting and monitoring electromigration(EM) in metal test stripes representative of the interconnection metallurgy used by the integrated circuits. The sensor capitalizes on the property of silicon whereby a small increase in temperature causes a large increase in carrier concentration. In this regard, the local temperature rise of an adjacent metal line undergoing EM failure manifests itself as a decrease in resistance of the sensor. The sensor is particularly suited for testing multi-level metallurgies such as those having an aluminum alloy sandwiched between metallic layers such as those used for diffusion barriers and anti-reflective coatings. Its fabrication is compatible with conventional MOSFET processes which use a self-aligned polysilicon gate. It can be particularly useful when built into the wafer kerf area or into a manufacturing test site(MTS) where it can be used to qualify the metallization of a particular job. Structures built into the wafer kerf can be tested immediately after metallization while those built into MTS chips can be reserved for long term reliability testing.