Precautions For Breakdown And Design Of Semiconductor Devices

There are two main types of breakdown mechanisms for semiconductor devices: ESD electro -inflection and thermal breakdown.Electric breakdown refers to the breakdown of the device caused by a strong electric field. This process is usually reversible. When the voltage disappears, the electrical characteristics of the device will be restored.Thermal breakdown (secondary breakdown) is related to the current. When the right direction is turned on, the current exceeds a certain limit (beyond the green area), and the device will cause heat burning.

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In the MOSFET (metal oxide semiconductor field effect crystal), there are two types of leakage breakdown voltage BVDS: one is the leakage of the PN knotThe avalanche breakdown, the second is the throughout of the two districts.The avalanche breakdown is when the inverse voltage is added, and as the reverse voltage increases, the reverse electrical field consumed by the PN end consumed area increases. When the electrons (or holes) and the lattice collideWidth Energy (EG) forced the collision -band electronics to transition to the guide zone, thereby generating a bunch of new electronic cave pairs. This process is called collision electrical ionization.When the electrical field consumed to a certain extent, the new electronics excited by the collision electricityYes, it may continue to generate new loads. This process will continue to continue, called avalanche double.If the current of the avalanche increases the current, the current of the outflow of the PN knot tends to be infinite, so the so -called avalanche penetration occurs.

In the MOS integrated circuit, when the N -channel MOSFET is in a cut -off state, the substrate voltage is negative, which will reduce the BVDS significantly.Experiments show that when the resistivity of the substrate is greater than a certain value (such as 1. cm), the BVDS is no longer related to the doping concentration of the substrate materials, but the polarity, size, and grid oxidation layer of the gate voltageDecisions of thickness.

When designing and applying semiconductor devices, these breakdown mechanisms and related restrictions need to be considered.For example, in order to prevent ESD electro -inflection, the structural design or protection circuit of the device can be optimized to limit the voltage.In order to prevent heat penetration, you can choose a density that is more suitable for high current density or use a more efficient heat dissipation solution.When applying MOSFET, you can optimize the performance of BVDS by adjusting the design of the metal grid electrode, the thickness of the oxidation layer, and the resistivity of the substrate material.