Optimization of ALD-ZnO Thin Films Toward Higher Conductivity

Zinc oxide (ZnO) fabricated by atomic layer deposition (ALD) is a promising material to replace tin-doped indium oxide (ITO) as standard transparent conductive oxide (TCO). However, its conductivity is still often about one order of magnitude below that of ITO. Variations in precursor choice, deposition process parameters, and post-processing of ALD-ZnO are tested concerning their impact in improvement of the TCO performance. Replacing the conventional diethylzinc (DEZ) with dimethylzinc (DMZ) as well as post-deposition annealing in H₂ yields no improvement for the highly conductive films (<10 mΩ cm) deposited at around 200 °C. However, reducing the purge time of the ALD process from 10 s down to 1 s and simultaneously increasing the DEZ pulse duration leads to a reduction in resistivity from 7.6 mΩ cm to 2.8 mΩcm. Furthermore, this process optimization involves a reduction of the total deposition time by almost one order of magnitude.