LDMOS Drift Region Doping Profile Optimization
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Solution Overview
Problem
High voltage semiconductor devices, such as LDMOS, face challenges in achieving reduced on-resistance and improved breakdown voltage due to limitations in sub-surface current control and non-uniform channel doping.
Innovation Solution
The semiconductor device incorporates a well region of a first conductive type at the substrate surface, with a gate electrode, source and drain regions, and a drift region of a second conductive type positioned under the drain region, featuring impurity regions with varying concentrations to optimize impurity distribution and depletion region expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LDMOS structure with uniform doping is used, then manufacturing is simpler, but on-resistance is high and breakdown voltage is limited
Solution Approach 1:
The patent implements non-uniform channel doping where the doping concentration varies laterally across the channel region. Specifically, the channel doping concentration is higher near the source region and lower near the drain region, creating locally optimized electrical characteristics that simultaneously improve breakdown voltage and reduce on-resistance without requiring complex multi-step doping processes
Solution Approach 2:
The patent changes the doping concentration parameter along the channel length to optimize device performance. By gradually varying the doping concentration from source to drain, the patent achieves improved electric field distribution and carrier transport, resulting in higher breakdown voltage and lower on-resistance while maintaining manufacturing simplicity through a single doping step
2Reliability
If drift region is added under drain to improve breakdown voltage, then breakdown voltage increases, but device complexity increases
Solution Approach 1:
The patent merges the drift region functionality with the channel region by implementing a gradual transition of doping concentration rather than creating a distinct, separate drift region. This integration reduces device complexity by eliminating the need for additional region boundaries and interfaces while still achieving the desired breakdown voltage enhancement through the non-uniform doping profile
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 effectively reduces on-resistance and enhances breakdown voltage by expanding the depletion region and improving impurity concentration gradients, resulting in improved performance for high voltage applications.
Implementation Method 1
a drift region of a second conductive type disposed under the drain region
Implementation Method 2
impurity regions with varying concentrations to optimize impurity distribution and depletion region expansion
Data Source
AI summary
A high voltage semiconductor device includes a well region of a first conductive type formed at a surface portion of a substrate, a gate electrode disposed on the well region, a source region formed at a surface portion of the well region adjacent to the gate electrode, a drain region formed at a surface portion of the well region adjacent to the gate electrode, and a drift region of a second conductive type disposed under the drain region.