Photo Detector Passivation Defect Detection by Selective Etching

The patent applies preliminary action by performing an etching treatment on the passivation layer before final inspection. This preliminary etching step creates visible damage patterns at defect locations (pinholes) that can be detected during inspection, allowing defective devices to be identified and removed before field deployment. The etching process is controlled to affect only the passivation layer initially, creating a detection mechanism without compromising the protected semiconductor layer in non-defective areas.

The patent uses an etchant as an intermediary substance to reveal defects. The etchant selectively interacts with the passivation layer at defect locations, creating visible etch marks or patterns that indicate the presence of pinholes. This intermediary process transforms invisible or hard-to-detect defects into easily observable characteristics during inspection, solving the detection difficulty while maintaining the passivation layer's protective function.

The patent applies local quality by creating non-uniform etching effects. The etchant is applied in a controlled manner such that etching occurs preferentially at defect locations (pinholes) where the passivation layer is already compromised, rather than uniformly across the entire passivation layer. This localized etching approach enables defect detection while preserving the integrity of the passivation layer in non-defective areas, maintaining both detection capability and protective function.

The patent uses partial action by applying the etchant for a limited duration or in a controlled sequence that affects only the passivation layer initially. The etching process is stopped or adjusted before it can significantly etch the underlying semiconductor layer, except at defect locations where the passivation layer is already absent. This partial etching approach provides sufficient defect detection while preventing excessive damage to the semiconductor structure.