EFFECT OF HYDROGEN ANNEALING ON HOT-CARRIER INSTABILITY OF X-RAY-IRRADIATED CMOS DEVICES

In the very large scale integration (VLSI) technology, the need for high density and high performance integrated circuit (IC) chip demands advanced processing techniques that often result in the generation of high energy particles and photons. Frequently, the radiation damage are introduced by these energetic particles and photons during device processing. The radiation damage created by x-ray irradiation, which can often occur during metal sputtering process, has been shown to potentially enhance hot-carrier instability if the neutral traps which act as electron or hole traps in the silicon dioxide is not annealed out. In this paper, we investigate the effects of annealing using different hydrogen contents and temperatures on the device characteristics and hot carrier instability of 0.5-mu-m CMOS devices after 1500 mJ/cm2 synchrotron x-ray irradiation. Three different annealing conditions were employed; 400-degrees-C H-2, 450-degrees-C H-2, and 400-degrees-C H-2 + N2. It is found that for all three different hydrogen anneals the normal characteristics of irradiated CMOS devices can be effectively recovered. The hot-carrier instability of both p- and n-channel MOSFETs are significantly enhanced after x-ray irradiation due to the creation of neutral traps and positively charged oxide traps. After high H-2 (100%) concentration anneals at 450-degrees-C, the hot-carrier instability in irradiated n-channel devices is greatly reduced and comparable to the non-irradiated devices. Although the hot-carrier instability in p-channel devices is also significantly reduced after annealing, the threshold voltage shifts are still enhanced as compared to the devices without exposure to x-ray irradiation during maximum gate current stress. For those non-irradiated, but hydrogen-annealed p-channel devices, the hot-carrier instability was observed to be worse than the non-irradiated device without hydrogen annealing.