Design of a Trench-Field Limiting Ring Composite Termination Structure
To improve the breakdown voltage performance of silicon power devices and the flow direction of IGBT currents,a trench-field limiting ring composite termination structure was proposed.A floating polysilicon trench was introduced at the main junction,a trench with dielectric was introduced at the left side of the field limiting ring,and the right side of the trench was just intersected with the transverse expansion interface on the left side of the field limiting ring.The results show that this structure improves the distribution of IGBT main junction current wires,changes part of the current path to longitudinal flow,changes the collision ionization path,and improves the reliability of the device termination structure while increasing the main junction potential.The field limiting ring structure with dielectric slots further shortens the termination length,with a transverse to longitudinal depletion ratio of 3.79,which is reduced by 1.48％compared with that of the traditional field limiting ring structure.The utilization rate of silicon wafers is improved,thereby reducing the chip area and saving manufacturing costs.This method is very effective in the design of FLR termination.
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