In situ reaction mechanism studies of plasma-assisted atomic layer deposition of Al2O3

Abstract

Reaction mechanisms during plasma-assisted atomic layer deposition (ALD) of Al2O3 from Al(CH3)3 and O2 plasma were studied by time-resolved quartz crystal microbalance measurements, mass spectrometry, and optical emission spectroscopy. Al(CH3)3 chemisorption on the oxide surface after the plasma pulse releases CH4 products while from the detection of CO, CO2, and H2O in the O2 plasma it is established that surface –CH3 groups are predominantly removed by O radical-driven combustionlike reactions. Also a second pathway exists for –CH3 removal driven by H2O generated in this plasma step. These reaction pathways are expected to be generic for plasma-assisted ALD of oxides from metal organic precursors.

Synthesis and in situ characterization of low-resistivity TaNx films by remote plasma atomic layer deposition

“…In our previous work on plasmaassisted ALD of Al 2 O 3 from a metal-organic precursor and O 2 plasma, we showed that optical emission spectroscopy can yield information on the ALD reaction mechanisms and the timing of the plasma step. 24 Evidently, similar insight can be expected for plasma-assisted ALD for metal nitrides.…”

Surface chemistry of plasma-assisted atomic layer deposition of Al2O3 studied by infrared spectroscopy

“…2,7 In our previous work on plasma-assisted ALD of Al 2 O 3 , we observed the formation of CH 4 after Al͑CH 3 ͒ 3 adsorption, while mainly CO, CO 2 , and H 2 O were formed in the O 2 plasma half-cycle through combustionlike surface reactions. 3,8 The surface chemistry during this plasma-assisted ALD process could not be fully resolved yet, because no measurements on the surface groups were available.…”

“…For example, the increase in -OH surface groups involved in plasma-assisted ALD when going to lower temperatures can be related to the increase in growth per cycle. However, care must be taken in such interpretation, since residual H 2 O ͑ei-ther being remnants of the excessive H 2 O dosing during thermal ALD or of the H 2 O reaction byproducts created during plasma-assisted ALD 3 ͒ is difficult to completely purge out of the reactor, especially at the low temperatures employed. Residual H 2 O can lead to -CH 3 consumption and -OH formation during the purge time and ͑relatively long͒ infrared measurement time following the Al͑CH 3 ͒ 3 precursor half-cycle.…”

“…To extend the applications of ALD, processes using alternative oxidant sources, such as O 3 and O 2 plasma, are actively researched. Using these oxidant sources, additional reactivity is supplied to the surface chemistry and this potentially allows for deposition at lower temperatures ͑Ͻ150°C͒ without compromising film quality.…”

“…Using these oxidant sources, additional reactivity is supplied to the surface chemistry and this potentially allows for deposition at lower temperatures ͑Ͻ150°C͒ without compromising film quality. [1][2][3] In order to fully exploit the benefits of the ALD technique, a fundamental understanding of the underlying surface chemistry is of vital importance. To this end the ALD process of Al 2 O 3 has been studied in great detail, since it shares generic features to equivalent metal oxide ALD processes.…”