GROWTH STUDIES AND REACTION MECHANISM OF THE ATOMIC LAYER DEPOSITION OF HAFNIUM OXIDE

摘要

The implementation of HfO{sub}2 gate dielectrics in sub-45 nm devices requires optimization of nanometer-thin HfO{sub}2 layers, deposited e.g. by Atomic Layer Deposition (ALD). In this work, we optimize the ALD conditions such as precursor pulse time and deposition temperature for HfO{sub}2 layers with physical thickness below 2 nm. Additionally, we investigate intermediate treatments in the ALD reaction cycle, such as exposure to gas phase moisture or remote plasma at low temperature and thermal anneals. Such intermediate treatments affect both growth-per-cycle (GPC) and impurity content of the HfO{sub}2 layers. The impact of these process modifications allows a better understanding of the reaction mechanisms in the HfCl{sub}4/H{sub}2O ALD process. The GPC is enhanced from 1.4-1.8 Hf/nm{sub}2 for conventional ALD to 3-4 Hf/nm{sup}2 for intermediate treatments at low temperature. Intermediate anneals reduce the Cl-content by about 2 orders of magnitude. Improvements in growth behavior result in better electrical performance, e.g. better scalability of Equivalent Oxide Thickness (EOT) and reduced leakage current as compared to the conventional process indicating better HfO{sub}2 film quality. On the other hand, the reduction of the Cl-content does not systematically improve the electrical properties.