Mapping of electrical leakage in transistors by anodic oxidation

Recently developed electrochemical methods permit the optical mapping of large and small bipolar transistors in an integrated circuit for electrical leakage before metallization. In one methods the emitters of the leaky transistors are decorated by a deposit of amorphous silicon produced as a result of anodic dissolution of the n
⁺
silicon in that region. Other methods depend on the colors of the anodic oxide grown on the emitter and base regions of the leaky transistors. A close relationship has been established between the oxide growth on the emitter and the base regions and the defective electrical characteristics of the transistor.