| For thin-oxide polysilicon-gate MOS capacitors after constant current stress, gate voltage change, flatbad voltage change and effective barrier height measurements show that negative and positive charges are trapped within a tunneling distance from both sides of the oxide. The generation and filling of new electron traps is continuous from the beginning of the stress period to the final oxide breakdown and it does not saturate. However, the generation of positive charge eventually saturates because of the compensation due to the coexistence of opposite polarities of charges. The higher electric fields and thicker oxides generate more positive charges near the anode side due to the larger distribution of the high-energy tail of energetic electrons.;An analytical model based on the capacitively coupled equivalent circuit for the FLOTOX EEPROM cell is established and its operation is simulated to provide guidelines for device design and optimization. A modified capacitive circuit model which includes the trapped charge in the oxide and transient effects due to deep depletion in the substrate is developed for the same EEPROM cell. The threshold voltage window collapse due to the trapped charges in the oxide is more significant as the charge trap location moves closer to the cathode side.;Based on the constant current stress and ramp voltage stress I-V measurements, we developed a new breakdown model, the "local field enhanced bond breaking model." As a result of coupling generated positive charges with the trapped negative charges, a local electric field is generated and, provided it has the same direction as the original oxide field, the combined electric field is augmented. When this locally high electric field reaches a critical value, the network of SiO... |
