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

• Published in: Nanomaterials (Basel, Switzerland) Vol. 13; no. 4
• Main Authors: An, Jehyun, Choi, Kyeongkeun, Park, Jongseo, Kang, Bohyeon, You, Hyunseo, Ahn, Sungmin, Baek, Rockhyun
• Format: Journal Article
• Language: English
• Published: MDPI AG 01.02.2023
• Subjects: Complementary metal oxide semiconductors; Plasma physics; Sensors; South Korea
• ISSN: 2079-4991; 2079-4991
• DOI: 10.3390/nano13040731

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