Impact of Mechanical Stress on Hot-Carrier Lifetime and Time-Dependent Dielectric Breakdown in Downscaled Complimentary Metal–Oxide–Semiconductor

Abstract

The interactions of hot-carrier (HC) instability and time-dependent dielectric breakdown (TDDB) with mechanical stress are investigated intensively. We determined from experimental data that the hot-carrier injection in p-type metal–oxide–semiconductor field-effect transistors (PMOSFETs) occurs at the center of the channel under the most severe stress condition of Vgs = Vds and that a physical mechanism similar to negative bias temperature instability (NBTI) is responsible for degradation at room temperature, as confirmed from the result of hydrodynamic simulations. We demonstrated that mechanical stress resulting from the sidewall spacer accelerates this hot carrier degradation in short-channel PMOSFETs. This phenomenon is not observed in the n-type MOSFET (NMOSFET) case. We also observed that the anomalous degradation in TDDB for downsized NMOSFETs is caused by the compressive stress from shallow trench isolation (STI) and shows strong correlation with hydrogen processes. The optimization of hydrogen processes and mechanical stress is indispensable for a highly reliable system LSI in the future.