An Investigation of Field-Effect Passivation Layer Characteristics Using Second Harmonic Generation Measurement

Second harmonic generation (SHG) characteristics of single and multilayer field-effect passivation (FEP) structures were investigated for CMOS image sensor application. By compensating the internal multiple reflection effect, the SHG characteristics of single and multilayer FEP structures were compared under equivalent conditions. Analysis of the time-dependent SHG intensity confirmed that the multilayer FEP structure has a 2.7 times higher SHG intensity than the single-layer structure, and the FEP layer is negatively charged from the initial state. In particular, when atomic layer deposition conditions were varied to control the Al ₂ O ₃ composition ratio, the SHG demonstrated greater detecting sensitivity than conventional material analysis methods such as RBS and XPS, even though it cannot distinguish the elements. Moreover, SIMS composition analysis verified that the initial state SHG intensity increase under high oxygen ambient Al ₂ O ₃ growth condition can be attributed to the change of impurities rather than the effect of oxygen areal density increase.