Electromigration Performance Improvement of Metal Heaters for Si Photonic Ring Modulators

Ring-based, resonant Si photonic (SiPho) devices are temperature sensitive and require thermal tuning for stable operation, which is accomplished with integrated metallic heaters. This paper investigates the combined electromigration (EM) and thermal performance of tungsten (W) heaters using calibrated electro-thermal finite element models. The current injectors that are used to supply the current to the heater are a known weak spot for electromigration. The presented modelling study shows the conflicting design requirements for optimal thermal performance and optimal EM performance, which results in the need of a careful trade-off, supported by experimental reliability data. Based on modelling results, new device designs are proposed with significant performance increase. Lastly, a new methodology is introduced which allows to predict the lifetime of the W-heaters, given specific operating conditions such as ambient temperature and required phase shift.