Characteristics and Breakdown Behaviors of Polysilicon Resistors for High Voltage Applications

Abstract

With the rapid development of the power integrated circuit technology, polysilicon resistors have been widely used not only in traditional CMOS circuits, but also in the high voltage applications. However, there have been few detailed reports about the polysilicon resistors’ characteristics, like voltage and temperature coefficients and breakdown behaviors which are critical parameters of high voltage applications. In this study, we experimentally find that the resistance of the polysilicon resistor with a relatively low doping concentration shows negative voltage and temperature coefficients, while that of the polysilicon resistor with a high doping concentration has positive voltage and temperature coefficients. Moreover, from the experimental results of breakdown voltages of the polysilicon resistors, it could be deduced that the breakdown of polysilicon resistors is thermally rather than electrically induced. We also proposed to add an N-type well underneath the oxide to increase the breakdown voltage in the vertical direction when the substrate is P-type doped.

Evaluation of stability and robustness of poly-Si resistors with different dopant concentrations

“…13) The electrical properties of lightly and heavily doped poly-Si resistors were reported to differ according to the conduction mechanisms; however, the effects of dopant concentration and stress condition on the resistor's stability or robustness have not been investigated. 14,15) The resistance of poly-Si resistor under stress over time is reported to increase exponentially to the point of saturation. The hydrogen out-diffusion theory based on the GB conduction of poly-Si resistor has been advanced to be the mechanism responsible for the resistivity increase in poly-Si resistors.…”