Embedded Stress Sensors for Strained Technologies Process Control

Mechanical stress management becomes a major issue for state-of-the-art CMOS technologies. Mechanical stress induced by the process steps is often at the origin of yield losses but also opportunities for technologies performance enhancement. Usual methods for mechanical stress measurement generally require offline measurements and are not compatible with fast correction of process parameters. We propose here embedded stress piezoresistive sensors to allow fast monitoring of mechanical stress and enable real time correction of the process parameters. The test vehicle presented here is dedicated to the gate structure stress monitoring. It is especially very sensitive to the nitride contact etch stop layer stress level. It is shown, in particular, that the structure is able to monitor process-related stress change in the nitride layer. Its feasibility, sensitivity, and relevance in an advanced process control scheme are investigated.