| AVS 62nd International Symposium & Exhibition | |
| Plasma Science and Technology | Wednesday Sessions |
| Session PS+TF-WeA |
| Session: | Plasma Deposition and Plasma Assisted ALD |
| Presenter: | Roger Bosch, Eindhoven University of Technology, The Netherlands |
| Authors: | R.H.E.C. Bosch, Eindhoven University of Technology, The Netherlands L.E. Cornelissen, Eindhoven University of Technology, The Netherlands C.K. Ande, Eindhoven University of Technology, The Netherlands W.M.M. Kessels, Eindhoven University of Technology, The Netherlands |
| Correspondent: | Click to Email |
Silicon nitride (SiNx) deposited by ALD is gaining a lot of interest lately, as it allows for conformal films prepared at low temperatures while maintaining a high film quality and uniform thickness. This is challenging for conventional deposition techniques, such as CVD and PECVD. Within the work presented in this contribution, the growth of SiNx by ALD and the associated surface chemistry have been studied. The chosen plasma-assisted ALD process employs bis(tertiary-butylamino)silane (SiH2[NHC(CH3)3]2,BTBAS) as precursor and N2 plasma as co-reactant. Various in situ studies have been performed and the experimental work has been complemented with DFT calculations.
More particularly, to study the surface chemistry we developed a versatile setup, which combines ALD with Fourier transform infrared spectroscopy. A sample manipulator was designed that enabled us to study the species present at the surface, with a submonolayer sensitivity, as a function of substrate temperature (100-300°C) and incident angle of the IR beam. The setup also allowed for gas phase measurements.
Gas phase infrared measurements have been performed to identify which species were present in the reactor after the precursor dose and N2 plasma exposure. The measurements revealed that tert-butylamine ((CH3)3CNH2) is the main reaction product after precursor exposure. This indicates that the Si-N bond in the precursor molecule breaks when it interacts with active sites at the surface.
Surface infrared measurements have been conducted at different temperatures to determine which species were present at the surface after one of the ALD half cycles, i.e. after the BTBAS half cycle and after the N2 plasma half cycle. Amongst others, a pronounced density of Si-H at the surface has been established, and at lower temperatures (~100°C) also a signal from C-H groups was clearly observed after BTBAS dosing. From these infrared measurements, complemented with DFT calculations and additional thin film studies, we propose a mechanism for the growth of SiNx by ALD using BTBAS and N2 plasma, which will be discussed during the presentation.