| AVS 62nd International Symposium & Exhibition | |
| Thin Film | Thursday Sessions |
| Session TF+EM+NS+PS+SM-ThM |
| Session: | Plasma ALD and Nano-applications |
| Presenter: | Saurabh Karwal, Eindhoven University of Technology, The Netherlands |
| Authors: | S. Karwal, Eindhoven University of Technology, The Netherlands B.L. Williams, Eindhoven University of Technology, The Netherlands W.M.M. Kessels, Eindhoven University of Technology, The Netherlands M. Creatore, Eindhoven University of Technology, The Netherlands |
| Correspondent: | Click to Email |
Transition metal nitrides (TMNs) have gained much attention in the semiconductor industry due to their characteristics such as copper and lithium diffusion barriers, metal-like behaviour (i.e. low resistivity) and high hardness, mechanical strength and chemical inertness. Among TMNs, hafnium nitride exhibits a low bulk resistivity of 33 μΩcm and highest negative Gibbs free energy of formation (HfN: -88.2, TiN: -80.4, TaN: -60.3 kcal/mol) and hence could serve as novel material for several applications, such as diffusion barrier and gate electrode in microelectronics, and reflective back contact for CIGS solar cells.
Conductive hafnium nitride thin films were deposited by inductively coupled plasma (ICP)- assisted atomic layer deposition using a heteroleptic metalorganic hafnium precursor, tris(dimethylamino)cyclopentadienylhafnium CpHf(NMe2)3 [TDMACpH] and H2-or N2- fed plasmas serving as co-reactants. The effects of the substrate temperature, plasma chemistry and plasma exposure time have been investigated in terms of growth-per-cycle (GPC), chemical, electrical and morphological properties of the deposited layer. It has been observed that highly resistive (0.75 Ωcm) Hf3N4 thin films are obtained via an A-B type ALD cycle (TDMACpH/N2 –fed plasma) with a GPC of 0.035 nm/cycle. Furthermore, a limited abstraction of the ligands leads to a residual carbon content in the layer of 7%.
Instead, conductive films (1.8 x 10-3 Ωcm) are achieved upon the application of an A-B-C ALD cycle where an intermediate H2- fed plasma exposure step is included between the TDMACpH exposure and the N2-fed plasma step, with a GPC of 0.045 nm/cycle. This intermediate step is found to be responsible for a more efficient removal of the precursor ligands and for the reduction of Hf4+ state to Hf3+ state, essential for guaranteeing electron conductivity. This transition of chemical and electrical properties of the deposited thin films is also accompanied by a change in crystallographic properties from amorphous (A-B ALD cycle) to conductive cubic HfN (A-B-C ALD cycle), as revealed by grazing incidence X-ray diffraction.
Contact: s.karwal@tue.nl