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 2 O 3 film were analyzed and optimized to improve the properties of the passivation layer of CMOS image sensors (CISs). During Al 2 O 3 deposition processing, the O 2 plasma exposure time was adjusted, and H 2 plasma treatment as well as post-metallization annealing (PMA) were performed as posttreatments. The flat-band voltage (V fb ) was significantly shifted (ΔV fb = 2.54 V) in the case of the Al 2 O 3 film with a shorter O 2 plasma exposure time; however, with a longer O 2 plasma exposure time, V fb was slightly shifted (ΔV fb = 0.61 V) owing to the reduction in the carbon impurity content. Additionally, the as-deposited Al 2 O 3 sample with a shorter O 2 plasma exposure time had a larger number of interface traps (interface trap density, D it = 8.98 × 10 13 eV -1 ·cm -2 ). However, D it was reduced to 1.12 × 10 12 eV -1 ·cm -2 by increasing the O 2 plasma exposure time and further reduced after PMA. Consequently, we fabricated an Al 2 O 3 film suitable for application as a CIS passivation layer with a reduced number of interface traps. However, the Al 2 O 3 film with increased O 2 plasma exposure time deteriorated owing to plasma damage after H 2 plasma treatment, which is a method of reducing carbon impurity content. This deterioration was validated using the C-V hump and breakdown characteristics.