| AVS 62nd International Symposium & Exhibition | |
| Thin Film | Thursday Sessions |
| Session TF+EM+NS+PS+SM-ThM |
| Session: | Plasma ALD and Nano-applications |
| Presenter: | Akhil Sharma, Eindhoven University of Technology, The Netherlands |
| Authors: | A. Sharma, Eindhoven University of Technology, The Netherlands V. Longo, Eindhoven University of Technology, The Netherlands A.A. Bol, Eindhoven University of Technology, The Netherlands W.M.M. Kessels, Eindhoven University of Technology, The Netherlands |
| Correspondent: | Click to Email |
In atomic layer deposition (ALD) the associated precursor chemistry has a large effect on the quality and properties of the deposited thin films. The most commonly used hafnium precursor for ALD of HfO2 is HfCl4. This precursor is not ideal for all applications due to possible chlorine contamination and the generation of corrosive by-products during the ALD process. Organometallic precursors such as Hf(NtMe)4 promise to be a better choice but they typically suffer from a limited thermal stability. In this context, HfCp(NMe2)3 might offer a better alternative because of its higher thermal stability. However, while using H2O as oxygen source in a thermal ALD process it yields a low growth rate1. This creates an opportunity for studying this precursor in combination with other oxygen sources. In this work, we report on the development of a novel plasma-enhanced ALD (PE-ALD) process using HfCp(NMe2)3 in combination with an O2 plasma to deposit HfO2 thin films. To our knowledge, to date, the PE-ALD for this precursor has not been reported in the literature.
Our results show that the PE-ALD process offers significant advantages over the reported thermal ALD process such as a high growth rate, reduced deposition temperature, shorter cycle time and good control over composition of the deposited films. In contrast to the thermal ALD process using HfCp(NMe2)3 and water1, the PE-ALD process has resulted into a wide ALD temperature range (150-400°C) with significantly higher growth per cycle values (1.1Å/cycle) and shorter cycle times which ultimately improves the wafer throughput. The level of impurities were found to decrease with increasing the deposition temperature as concluded from XPS and ERD analyses. The concentrations of residual carbon and hydrogen reduced from 1.0 at% to 0.2 at% and 3.4 at% to 0.8 at%, respectively, by increasing the deposition temperature from 200°C to 400°C. Moreover, RBS studies showed an improvement in stoichiometry of HfO2 thin films with increase in deposition temperature resulting in a Hf/O ratio of ~0.5 at 400°C. Furthermore, GI-XRD measurements detected a strong transition from amorphous (300°C) to fully crystallized films (400°C), consisting of a mixture of monoclinic, tetragonal and cubic phases. These results therefore have demonstrated that PE-ALD using HfCp(NMe2)3 and O2 plasma is a promising and viable alternative to the thermal ALD process producing high quality HfO2 thin films over a wider temperature range and with faster cycle times.
1. Consiglio et al, J. Vac. Sci. Technol. A 30(1), 2012