Dimension Dependence of Unusual HCI-Induced Degradation on N-Channel High-Voltage DEMOSFET

According to reliability models, a short-channel MOSFET is susceptible to the device characteristics degradation due to the hot carrier injection (HCI) effect. In this paper, we describe an anomalous degradation behavior that is opposite to the general understandings on the n-channel high-voltage drain-extended MOSFETs. The experimental data indicate that the threshold voltage $(V_{\rm th})$ degrades much worse in a long-channel device than in a short-channel one during the HCI stress. In addition, a narrow device shows more $V_{\rm th}$ shifts than a wide one does. These phenomena showing the dimension dependence on the channel length $(L_{{\rm ch}})$ and channel width $(W)$ can be attributed to the alleviation of the Kirk\´s effect and the STI-enhanced residual mechanical stress. An injection efficiency in the form of the normalized gate-to-drain current $(I_{{\rm gs}}/I_{{\rm ds}})$ is successfully introduced to project the dimension-dependent $V_{\rm th}$ shift. The kinetic equation of trap formation is involved in the numerical simulation for giving a comprehensive interpretation on the degradation mechanism.