CHEMICAL VAPOR DEPOSITION OF THIN FILM MATERIALS FOR ...

3.4 Conclusion
In summary, TDMAH adsorption and reaction on hydrogenated Si(100) surface has been
investigated by in-situ ATR-FTIR experiments. It has been found that for temperatures below
100˚C, physisorption is the main mode of TDMAH adsorb onto the crystal surface and no
obvious surface Si-H bonds breaking. These physisorbed TDMAH molecules can be pumped
away easily. At temperatures between 100˚C and 150˚C, surface adsorbed TDMAH molecules
start to decompose and newly emerging IR peaks at 1591 cm -1 and 1639 cm -1 were assigned to
N=C and Hf-H vibrational mode respectively based on a β-hydride elimination mechanism. The
decomposition species on the surface has been found hard to desorb at low temperatures, which
can contaminate the thin film growth if the purging/pumping time is not long enough. The
surface Si-H bonds subtraction has been found for adsorption above 150˚C and it's closely
related to the TDMAH decomposition behavior.
Hafnium nitride thin film deposition by PEALD using TDMAH and hydrogen plasma has
been investigated. Uniform and moderately conductive HfNxCy thin films were deposited on
Si(100) and SiO2 substrates. A thin surface layer (2~3nm) containing both hafnium nitride and
organic complexes of TDMAH decomposition has been found by in vacuo XPS analysis. Depth
profile analysis by XPS indicated the existence of hafnium carbide phase in the bulk. Thin film
resistivity is greatly affected by the level of hydrogen plasma power, in which higher plasma
power results in lower thin film resistivity. In spite of this tunability of resistivity by plasma
power, carbon incorporation is still a big issue for this PEALD method. Therefore, more
appropriate reducing agent or nitrogen source is probably needed to get pure HfN thin film by
CVD/ALD method.
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