Atomic layer deposition of HfO2 investigated in situ by means of a noncontact atomic force microscopy

An ultra high vacuum atomic force microscope operating in a noncontact mode has been employed to investigate in situ atomic layer deposition (ALD) of HfO2. Tetrakis-di-methyl-amido-Hf and H2O were used as precursors and the deposition process was performed on Si(001)/SiO2 substrate maintained at 230 °C. The relation between the film growth and the root mean square surface roughness was studied after each ALD cycle. The histograms of the initial stages of the ALD process have been compared in terms of the surface height data as a way of characterizing the growth process. Parameter values corresponding to HfO2 layer thickness and coverage were calculated. A detailed analysis of the surface height histograms allowed one to construct a simplified growth model and confirm the completion of the first HfO2 layer after four ALD cycles.