LDMOS Drain Finger Termination for Avalanche Current Distribution
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Solution Overview
Problem
LDMOS transistors face challenges in achieving homogeneous breakdown voltage distribution, leading to concentrated avalanche current at termination ends, resulting in high on-state resistance and reduced robustness at high breakdown voltages.
Innovation Solution
The implementation of a drain finger termination configuration where the area of the drift region is gradually increased near the drain end of the drain finger, allowing for a well-distributed avalanche current along the drain finger, achieved by laterally tilting the gate structures and shields away from the drain region at the drain ends.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the drift region area is kept uniform along the drain finger, then the manufacturing process is simple, but the avalanche current becomes concentrated at termination ends resulting in high on-state resistance
Solution Approach 1:
The drift region area is gradually increased in proximity to the drain end of the drain finger, creating a non-uniform structure where different regions have different properties. This local variation in drift region area distributes the avalanche current more evenly along the drain finger, reducing concentration at termination ends and lowering on-state resistance while maintaining manufacturing feasibility
2Reliability
If the gate structure extends uniformly along the drain finger, then the device structure is simple, but the breakdown voltage distribution becomes non-homogeneous
Solution Approach 1:
The gate structure is laterally tilted away from the drain region at the drain ends, creating an asymmetric configuration. This asymmetric gate structure, combined with the varying drift region area, achieves homogeneous breakdown voltage distribution along the drain finger by controlling the electric field distribution, while the tilt angle and extent can be optimized to balance performance and manufacturing complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances transistor performance by achieving lower on-state resistance at high breakdown voltages, thereby improving robustness and stability of the transistor.
Implementation Method 1
obtain a well-distributed avalanche current at the breakdown voltage along the length of the drain finger
Data Source
AI summary
A semiconductor device, such as a laterally diffused metal-oxide-semiconductor (LDMOS) transistor, includes a semiconductor substrate in which a source region and a drain region are disposed. The drain region has a drain finger terminating at a drain end. A gate structure is supported by the semiconductor substrate between the source region and the drain region, the gate structure extending laterally beyond the drain end. A drift region in the semiconductor substrate extends laterally from the drain region to at least the gate structure. The drift region is characterized by a first distance between a first sidewall of the drain finger and a second sidewall of the gate structure, and the gate structure is laterally tilted away from the drain region at the drain end of the drain finger to a second distance that is greater than the first distance.