Analysis and characterization of a mechanical sensor to monitor stress in interconnect features

Abstract

A mechanical rotating stress sensor fabricated in copper has been characterized in 100 nm single damascene technology. Geometrical variations to the structure produce a distinctive behaviour which can be used to fit the actuating stress. Existing analytical models were tested and shown to be unable to describe the structure due to geometric non-linearities not considered by these one-dimensional solutions. A model based on the large strain finite element method was developed to include this non-linearity and fully describe the sensor design for all geometrical variations. The stress determined from the Cu rotating sensors is comparable to measurements performed using high intensity X-ray diffraction on similar samples. Furthermore, the simulation methodology is validated for calibrated Al sensors. All of the studied samples show an excellent fit with the developed finite element analysis, demonstrating the validity of the model to predict smaller geometries, showing that the sensor can be utilized in future integration schemes and applied to other material systems.