Invited Paper PS+SS-WeM3
Plasma Diagnostics and Nanoscale Surface Processing - Application to SiO2, High-k PVD and ALD
Wednesday, November 2, 2011, 8:40 am, Room 202
Introduction
Reactive plasmas are widely used for surface processings due to its controllable ion energy and radial fluxes.
Nano size feature control with plasma processing requires nonthermal chemistry with low energy ion exposure. Metastable atoms with internal energy of a few eV become important for the quality and throughput of deposition as ion energy is reduced.
Minimizing the processing target to the nanoscale also reveals the new properties of materials interacting with plasmas due to the size effect. Namely, sticking coefficients of radicals on metal significantly increase.
In the presentation, some recent results on metastable radical induced deposition including HfO2 ALD are shown. The latest findings of nano particle interaction with reactive plasmas are introduced for the model case of PVD based HfSiON film growth.
Reactive metastables for oxide growth : SiO2 and HfO2
The density of metastable O(1D) (1.9eV) in Ar-diluted O2 ICP shows maximum at O2 fraction of 1% and the flux shows significant increase due to the reduced quenching by O2. O(1D) density is measured by Vacuum UltraViolet Absorption Spectroscopy (VUVAS). The XPS analysis shows the stoichiometry of the grown SiO2 is comparable to the thermal oxide as well as the electrical breakdown.
The scheme is applied to the plasma enhanced atomic layer deposition (PEALD) of HfO2. The reagent is TEMAH and the oxidant is Ar-diluted O2 ICP. The increased O(1D) flux enables less particle film surface with fewer carbon contamination.
Reactive surface nano particles interacting with plasma : HfSiON growth
Hf nanoparticles self assembled on SiO2/Si(100), origin of HfSiON, have sticking coefficient of N radicals close to 1 in the initial stage of N2 ICP exposure. The reactivity of the nanoparticles with underlying SiO2 is enhanced by the plasma exposure, results in the formation of carbon free HfSiON film.
Concluding remarks
- Metastables are important reactant for low temperature non-biased deposition processes
- Metastable flux is controllable with the base gas chemistry
- Nanoscale surface features are current concerns for plasma deposition
- Nano sized surface has totally different reaction kinetics including interface with underlayer
- Nano size effect of the surface is evident for radical reactivity
- Self assembly (bottom up scheme) is highly important for next generation nano scale plasma processing as well as lithographic techniques (top down scheme)
Acknowledgement
This work was supported by MEXT Grant-in-Aid for Scientific Research on Innovative Areas （22110520） and JSPS Grant-in-Aid for Young Scientists (B) (21760033).