468925 Anomalous ALD Growth per Cycle Under Precursor-Limited Conditions
Alumina ALD using trimethylaluminum and water as precursors is among the most widely studied ALD processes . Under nominal deposition conditions, a growth-per-cycle (gpc) of 0.11 nm/cycle is typically found under self-saturating conditions. As one reduces either or both precursor dosages, one would expect to find that the gpc ultimately begins to drop from the value corresponding to the self-saturating plateau to a value of zero as the dosage drops to the same. Henn-Lecordier and coworkers , however, found anomalously high gpc values in the precursor-starved region of operation. In this paper, we will report similar findings in which gpc values that are approximately double that of the nominal value of 0.11 nm/cycle as the TMA does is reduced while holding the water dose constant. Furthermore, we find that film thickness remains spatially uniform in this region, up to the point where precursor depletion becomes important. Potential reaction mechanisms for the observed behavior will be presented.
 Puurunen, R. L., Surface chemistry of atomic layer deposition: A case study for the trimethylaluminum/water process, Appl. Phys. Rev. 97 121301:52 (2005).
 Henn-Lecordier, L., M. Anderle, E. Robinson, and G. W. Rubloff, J. Vac. Sci. Technol. A, 29 051509-1 (2011).