CF4 plasma-based atomic layer etching of Al2O3 and surface smoothing effect

Plasma-based Al2O3 atomic layer etching (pALE) has a reaction mechanism similar to thermal Al2O3 ALE (tALE). The main difference between the two methods is that pALE uses plasma instead of HF in tALE to fluorinate Al2O3 to AlF3. In this study, the CF4 plasma source commonly used for dry etching is combined with a self-developed low-ion-bombardment remote Al2O3 plasma-based ALE system to obtain Al2O3 plasma fluorination conditions, and then the AlCl(CH3)2 (dimethylaluminum chloride) precursor is used to develop the pALE Al2O3 process. In addition to using x-ray photoelectron spectroscopy to investigate ideal fluorination conditions of CF4 plasma for Al2O3 films and establishing the linear etching rate curves of pALE at different process temperatures (250–400 °C), we used atomic force microscopy to analyze the surface morphology of the Al2O3 films after dry etching and pALE. We showed that pALE can smooth Al2O3 films with a root mean square surface roughness of 1.396–0.655 nm and used anodic aluminum oxide substrates with nanotrench structures to demonstrate that pALE can improve the surface roughness of nonplanar structures.