Growth and Crystallization of TiO2 Thin Films by Atomic Layer Deposition Using a Novel Amido Guanidinate Titanium Source and Tetrakis-dimethylamido-titanium

We studied the growth of TiO2 by liquid injection atomic layer deposition (ALD) utilizing two different amide-based titanium sources, tetrakis-dimethylamido-titanium [(NMe2)(4)-Ti, TDMAT] and its recently developed derivative, tris-(dimethylamido)-mono-(N,N'-diisopropyl-dimethyl-amido-guanidinato)-titanium {[(N-iPr)(2)NMe2]Ti(NMe2)(3), TiA(3)G(1)}, with water vapor as counterreactant. A clear saturation of growth with an increasing precursor supply was found for TDMAT between 150 and 300 degrees C and for TiA(3)G(1) between 150 and 330 degrees C. Representative growth per cycle (GPC) values at 250 degrees C were 0.041 and 0.044 nm/cycle, respectively. Compared to that of TDMAT, ALD of TiA(3)G(1) exhibited a significantly higher stability in the GPC values up to 300 degrees C coinciding with an improved temperature stability of the precursor. Both processes showed a minimum of the growth rate as a function of temperature. In all cases, the residual carbon and nitrogen contents of the TiO2 films were <3 atom %. Conformal growth was demonstrated on three-dimensional pinhole structures with an aspect ratio of around 1:30. Deposition temperatures of <= 200 degrees C led to quasi-amorphous films. At higher growth temperatures, the anatase phase developed, accompanied by the brooldte and/or the rutile phase depending on process conditions, deposition temperature, and film thickness.