Characterization and Modeling of Very Low Degradations of N⁺ Polysilicon Resistor Under Thermal Stress

Polysilicon resistors are widely used in bipolar-CMOS-DMOS (BCD) technology for current sensing applications due to their stability and integration capabilities. However, their long-term reliability is compromised by resistance degradation under thermal and electrical stress. In this work, we present a comprehensive electrical and physical characterization of N+ polysilicon resistors subjected to controlled stress conditions. Through extensive experimental analysis, we quantify the resistance drift over time and temperature, identifying the primary degradation mechanisms. We propose an empirical degradation model that accurately captures the observed behavior, accounting for both short- and long-term resistance drifts. Microstructural investigations using transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) reveal dopant segregation and grain boundary effects, providing insights into the physical origins of degradation. The proposed model offers predictive capabilities, enabling better design optimization and lifetime estimation of polysilicon resistors in critical sensing applications.