A Study of Enhancement Quality of HfO2 Grown at Low Temperature

Abstract

By Moore’s law, the double of transistors every two years in CMOS technology. However, this integration density is getting their limitation on the horizontal dimension. So it is required a new scaling method. 3D ICs is an excellent alternative: The layer of devices are built on the top of each other, so it can increase the number of transistor per mm2. However, because of the sequential fabrication process, it has a thermal budget problem. This is the top device that has to grow at low temperature to preserve the performance of the bottom device. However, at low growth temperature, it leads to a reliability problem. Moreover, the electrical properties of the dielectric are poorer than those grown at high temperatures because of non-stoichiometric compounds due to limited thermal energy. Therefore, there are necessities for improving the dielectric qualities of the thin film at the low-temperature growth. In this study, we demonstrated the effect of low-temperature O2 annealing on HfO2 thin film growth at low-temperatures. HfO2 MIM capacitor was fabricated by the ALD process at 150˚C. Then, O2 annealing was introduced at 250˚C by RTA systems with a target of improving the dielectric quality. The TZDB measurement was applied to evaluate reliability after low-temperature O2 annealing. Their electrical properties were compared by capacitance-voltage (C-V) and leakage current (I-V). The dielectric constant was extracted before and after low-temperature O2 annealing and it increased even at low annealing temperatures. This study is expected to help in improving the dielectric quality of low-temperature growth devices in the future.