Investigation on the Initial Hot-Carrier Injection in P-LDMOS Transistors With Shallow Trench Isolation Structure

In this paper, early-stage hot-electron generation is shown to inject electrons into the shallow trench isolation (STI) edge above the drift region that causes the linear-region drain current to increase abruptly in the first moment of the stress for P-LDMOS transistors. After this early-stage carrier trapping, the transistor exhibits normal hot-carrier degradation during the following stress period. To further study this phenomenon, the geometry and the doping profile of the drift region near the STI edge and the polysilicon gate doping area are changed to investigate the initial I_DLIN increase. Two-dimensional device simulator is used to analyze the experimental results. It is proven that the amount of current increase strongly depends on the distance from the maximum impact ionization generation rate point to the STI.