Reliability of integrated resistors and the influence of WLCSP bake

This paper presents the long-term stability of integrated CMOS resistors in a 40nm technology node. Unsilicided polysilicon and diffusion resistors with two different geometries were investigated. The thermal stability of the resistors was studied at different stress temperatures. Some resistors were subjected to the critical bake temperature in the WLCSP (Wafer Level Chip Scale Packaging) assembly process. The resistance shifts were measured at different stress temperatures after the bake. It was found that WLCSP thermal budget has a significant influence on the resistor shift characteristics in the case of p-poly resistors.