| 摘要 |
PURPOSE:To increase the bonding area without increasing a breakdown voltage by forming the vicinity of the surface of a substrate of a P-N junction with a high density diffused layer. CONSTITUTION:When a potential difference is generated between a conductor 4 and a substrate 1 by a surge input and a P-N junction is conducted, if the conductor 4 is lower potential than the substrate 1, i.e., if the P-N junction is forwardly biased, the entire junction between semiconductor layers 2, 3 and the substrate 1 serues as a current path, the potential difference between the substrate 1 and the conductor 4 is clamped to so-called junction potential difference (approx. 0.6V), and no high potential difference is generated. Then, if the conductor 4 is higher in potential than the substrate 1, the P-N junction is conducted by the breakdown for the potential difference of the breakdown voltage (approx. 11V) or higher to clamp the potential difference between the conductor 4 and the substrate 1. A main current path is concentrated to the surface of the substrate by the surface breakdown, but a small current path exists in the bottom of the junction. The current concentration in the N-type region can be alleviated due to the presence of the well layer 2.
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