NBTI/HCI Modeling and Full-Chip Analysis in Design Environment

Hot-carrier (HC) degradation and negative bias temperature instability (NBTI) of MOS devices are the two most important reliability concerns for deep submicron (DSM) designs. HC degradation occurs when the channel electrons are accelerated in the high electric field near the drain of the MOS device and create interface states, electron traps, or hole traps in the gate oxide near the drain. LDD structure has become the standard drain structure to alleviate HC effects and the device-based DC criteria have been used extensively to qualify devices for HC reliability. It is becoming clear that these guidelines are too conservative for DSM technologies. It is therefore strongly desirable that circuit reliability simulation using a realistic AC (transient) circuit operation condition should be on the fingertips of the circuit designers to achieve the following goals: to maximize design performance by minimizing design guard-band, to speed up timing closure by reducing design iterations and to ensure circuit reliability by fixing design reliability problems. How to fit reliability simulation into the design environment is a more interesting topic from designer’s perspective.