Meaning
Degradation mechanism involves the gain of sufficient kinetic energy by electrons or holes to overcome the potential barrier of the gate dielectric. In sub-micron transistors, hot carrier injection occurs when the high electric field near the drain accelerates carriers into the interface between the silicon and the oxide. This impact creates defects that permanently shift the performance of the device.
Interface Damage
Collisions between high-energy particles and the atomic lattice break the silicon-hydrogen bonds at the gate boundary. These broken bonds create trapping sites that capture charge and reduce the mobility of the carriers.
Transistor Aging
Threshold voltage increases as more charge is trapped, making it more difficult for the gate to control the flow of current. This shift slows down the switching speed of the logic gates and can lead to timing errors in high-speed digital circuits. Precise modeling of hot carrier injection is required to ensure the long-term stability of the processor during its operational life.
Operational Limit
Supply voltage and channel length are the primary factors that determine the severity of the effect. Reducing the operating voltage lowers the electric field and decreases the energy of the carriers. Modern design tools include aging simulations to help engineers choose the best balance between speed and the expected lifespan of the product.