H Plasma and PMA Effects on PEALD-AlO Films with Different O Plasma Exposure Times for CIS Passivation Layers.

In this study, the electrical properties of AlO film were analyzed and optimized to improve the properties of the passivation layer of CMOS image sensors (CISs). During AlO deposition processing, the O plasma exposure time was adjusted, and H plasma treatment as well as post-metallization annealing (PMA) were performed as posttreatments. The flat-band voltage (V) was significantly shifted (ΔV = 2.54 V) in the case of the AlO film with a shorter O plasma exposure time; however, with a longer O plasma exposure time, V was slightly shifted (ΔV = 0.61 V) owing to the reduction in the carbon impurity content. Additionally, the as-deposited AlO sample with a shorter O plasma exposure time had a larger number of interface traps (interface trap density, D = 8.98 × 10 eV·cm). However, D was reduced to 1.12 × 10 eV·cm by increasing the O plasma exposure time and further reduced after PMA. Consequently, we fabricated an AlO film suitable for application as a CIS passivation layer with a reduced number of interface traps. However, the AlO film with increased O plasma exposure time deteriorated owing to plasma damage after H plasma treatment, which is a method of reducing carbon impurity content. This deterioration was validated using the C-V hump and breakdown characteristics.