Suppression of the redox reaction between the IGZO surface and the reducing agent TMA using fluorine oxidizing agent treatment

We propose that the post-deposition oxidation of the IGZO surface is essential for improving the interface quality, with Al2O3 prepared by atomic layer deposition (ALD) employing a common metal precursor trimethylaluminum (TMA). Here, the ALD-Al2O3 process was conducted using H2O as an oxidant at a substrate temperature of 150 degrees C after IGZO deposition. The depth-resolved X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) data reveal the defect-rich and poor interface of the standard Al2O3/IGZO stack due to the redox reaction between the IGZO surface and TMA. The anion character of the IGZO was modified by introducing fluorine, which is known as a stability enhancer for oxide semiconductors. We highlight that the presence of the fluorine also improves the interface quality with ALD-Al2O3. As a consequence of the fluorine incorporation prior to the ALD-Al2O3 process, the chemical reduction reaction of the IGZO surface was effectively alleviated, resulting in a defect-passivated and sharp interface owing to the strong oxidizing nature of the fluorine. This study proposes that the post-deposition oxidation of the IGZO surface is essential to counteract the oxygen-scavenging behavior of TMA, a common Al precursor for ALD-Al2O3.

Automated summary

This study investigates the importance of post-deposition oxidation of the IGZO surface in enhancing interface quality and highlights the benefits of introducing fluorine. It suggests that the presence of fluorine effectively alleviates the chemical reduction reaction, resulting in a defect-passivated and sharp interface.