This paper describes a fast and effective sample preparation method to allow backside fault localization on GaN package devices. Backside analysis by Photon Emission Microscopy (PEM) is becoming preferable to frontside analysis when the die is covered by metal layers. This paper describes an optimized method for backside sample preparation on GaN package devices having a thick heavily doped p-type silicon substrate. The method combines mechanical and chemical deprocessing steps, resulting in a fast and effective sample preparation technique for PEM analysis. Additionally, the laser marking process parameters to facilitate orientation during the final physical failure analysis by Focused Ion Beam (FIB) are also shared.

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