Research On Application Of Low-temperature Microwave Annealing Technology In Gate Dielectric

Microwave annealing as a new emerging annealing technique of low thermal budget is drawing increasingly attention and is widely used in researching the crystallization of amphorous silicon, the formation of silicide, dopant activation and so on. Significant results have been achieved. For example, dopant activation with little diffusion has been achieved under low temperature, low resistivity silicide as well as crystallization of amphorous silicon and carbon silicon have been formed, and so on. The defects in the dielectric of metal-oxide-semiconductor may cause the shift of threshold voltage, which may cause instability of devices. Accordingly, in this paper, we have investigated the application of low temperature microwave annealing in gate dielectric stack. Furthermore, we have proposed a fabrication method of MOSFETs using gate-first process on the basis of experimental data.Reparation of defects in the high-K/metal gate stack with microwave annealing is investigated in this paper. Samples are splitted into six batches. They are no annealing(HfO2 thin film are 11.9 nm and 23.4nm), microwave annealing prior to deposition of molybdenum, rapid thermal annealing prior to deposition of molybdenum, microwave annealing after deposition of molybdenum and rapid thermal annealing after the deposition of molybdenum, respectively. At frequency of 100 kHz and 1 kHz, C-V curves for all samples with Mo/HfO2/Si (100) Metal-Insulator-Semiconductor structures are measured. The flat band voltage (Vfb) and hysteresis window are extracted from the measured C-V curves at frequency of 100 kHz. Thus, the fixed charge density and the charged traps density in the high-K/metal gate are estimated, and the density of fast interface states is calculated with Terman method. From the kinks on the C-V curves measured at frequency of 1 kHz, the density of slow interface states in the high-K/metal gate is qualitatively described. The results show that, after microwave annealing, the fixed charge, the charged traps, the fast interface states and the slow interface states have been repaired to some extent. In addition, at similar thermal budget, microwave annealing repairs more fixed charges, slow interface states and charged traps in the high-K/metal gate than rapid thermal annealing. However, for the reparation of the fast interface states, microwave annealing has no obvious advantage.On the basis of reparation of defects in high-k/metal gate and source-drain dopant activation using low-temperature microwave annealing technique reported by recent literature, this paper proposes a fabrication method of MOSFETs using gate-first process, unlike traditional gate-first process with high temperature annealing, which employs low-temperature microwave annealing technique. Thus, it won’t cause the shift of threshold voltage of MOSFETs and the formation of thin SiO2 interfacial layer, and avoids the complicated and expensive gate-last process. In brief, low-temperature microwave technology overcomes the shortcomings of traditional gate-first and gate-last processes, hence, it can be served as a promising replacement of traditional annealing method below 22 nanometer node.