LDMOS Drift Region Layout With Segmented Floating Field Plates
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Solution Overview
Problem
Existing laterally diffused metal oxide semiconductor (LDMOS) devices with longitudinal floating field plate structures face limitations in reducing on-resistance while increasing breakdown voltage due to blocked current paths in the drift region.
Innovation Solution
A novel LDMOS device design featuring a longitudinal floating field plate array with a plurality of trench structures filled with a conductive layer and dielectric layer, along with implantation regions of opposite conductivity type, is introduced to enhance breakdown voltage and reduce on-resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a longitudinal floating field plate structure is introduced into the drift region, then the breakdown voltage is increased and on-resistance is decreased to a certain extent, but the current path is blocked due to the deep trench being located in the conductive channel
Solution Approach 1:
The single deep trench field plate structure is segmented into multiple shallow trench field plate structures arranged in parallel. This segmentation allows the conductive channel to flow around the trenches through lateral paths, preventing current blockage while maintaining the voltage-blocking function. The multiple shallow trenches collectively provide the necessary breakdown voltage enhancement without creating a single point of current obstruction.
Solution Approach 2:
The invention transitions from a single deep vertical trench structure to multiple shallow trenches with lateral extension. By adding the lateral dimension and distributing the field plates across multiple positions, the current can flow laterally around the trenches rather than being blocked vertically. This dimensional change resolves the contradiction between voltage blocking and current flow.
2Strength
If a longitudinal floating field plate structure is introduced, then the withstand voltage is increased, but the on-resistance remains high because the drift region has fewer conductive paths
Solution Approach 1:
The field plate structure is divided into multiple segmented shallow trenches rather than one deep trench. This segmentation creates multiple discrete conductive paths around each trench, increasing the total number of available current paths in the drift region. The segmented approach maintains structural simplicity while providing multiple lateral conduction routes.
Solution Approach 2:
The field plates are positioned at specific locations within the drift region, creating local field enhancement zones without affecting the entire conductive channel uniformly. This localized approach allows current to flow through unaffected regions while gaining the voltage-blocking benefit at specific critical points.
Data Source
AI summary
Disclosed are a laterally diffused metal oxide semiconductor device and a method for preparing the same. The device includes a substrate (101) of a first conductivity type, a drift region (102) of a second conductivity type, a longitudinal floating field plate array and a plurality of implantation regions (103) of the first conductivity type. The drift region is located in the substrate of the first conductivity type. The longitudinal floating field plate array includes a plurality of longitudinal floating field plate structures (104) arranged at intervals in rows and columns. Each longitudinal floating field plate structures includes a dielectric layer (1041) disposed on an inner surface of a trench and a conductive layer (1042) filling the trench. The plurality of implantation regions are located in the drift region of, each implantation region is located between two adjacent longitudinal floating field plate structures in each row.