Comparison of NMOS and PMOS hot carrier effects from 300 to 77 K

Since hot carrier effects can pose a potential limit to device scaling, hot-carrier-induced device degradation has been one of the major concerns in modern device technology. Currently, there is a great interest in pursuing low-temperature operation of MOS devices since it offers many advantages compared to room temperature operation. Also, low-temperature operation is often required for space applications. However, low-temperature operation exacerbates hot carrier reliability of MOS devices. Even though hot carrier effects are significantly worse at low temperature, most of the studies on hot-carrier-induced device degradation were done at room temperature and little has been done at low temperature. In this work, hot-carrier-induced device degradation is characterized from 77 K to room temperature for both NMOS and PMOS devices with the emphasis on low-temperature behavior of hot carrier degradation. For NMOS devices, the worst case bias condition for hot carrier effects is found to be a function of temperature. It is also determined that one of the primary reasons for the great reduction on hot carrier device lifetime at low temperature is that a given amount of damage simply induces a greater reduction on device performance at low temperature. For PMOS devices, the initial damage appears similar for both room temperature and 77 K; however, subsequent annealing indicates that the damage mechanism at 77 K differs markedly from that at 300 K. Hot carrier stressing on PMOS devices at low temperature appears to induce hole generation and substantial interface state creation upon annealing unlike 300 K stressed devices. This finding may have serious reliability implications for PMOS devices operated at cryogenic temperatures.