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Usually in BCD process, HDD is the highly doped drain which helps to have a better electrical connection between metal contract and semiconductor, so that no wanted Schottky junction forms. NHDD is basically a extended drain region with higher annealing time/temperature, usually with high ion implantation energy one can dope the N-type purity in bulk and than use annealing to get a higher doped area below the drift region. |
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