H 2 Plasma and PMA Effects on PEALD-Al 2 O 3 Films with Different O 2 Plasma Exposure Times for CIS Passivation Layers

In this study, the electrical properties of Al O film were analyzed and optimized to improve the properties of the passivation layer of CMOS image sensors (CISs). During Al O 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 Al O 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 Al O 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 Al O film suitable for application as a CIS passivation layer with a reduced number of interface traps. However, the Al O 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.