LDMOS Doped Drift Region Layout for Breakdown and Kirk Effect
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Solution Overview
Problem
As semiconductor devices are scaled down, maintaining low on-resistance and high breakdown voltage in transistors becomes challenging, particularly in lateral diffused MOSFETs, where the Kirk effect and parasitic BJT action can degrade performance.
Innovation Solution
Incorporating a lightly doped drain (LDD) region between the gate and drain in lateral diffused MOSFETs, which suppresses the Kirk effect and enhances drain current performance while maintaining high breakdown voltage by optimizing dopant concentrations and spatial arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If semiconductor devices are scaled down to maintain high integration density, then integration density is improved, but transistor performance (on-resistance and breakdown voltage) deteriorates
Solution Approach 1:
The drain region is segmented into multiple doped regions with different doping concentrations (first doped region with lower concentration, second doped region with higher concentration). This segmentation allows the device to simultaneously achieve low on-resistance (through the heavily doped second region) and high breakdown voltage (through the lightly doped first region), resolving the performance degradation issue while maintaining scaled dimensions for high integration density
Solution Approach 2:
Different regions of the semiconductor device are assigned different doping concentrations tailored to their specific functional requirements. The first doped region has lower concentration optimized for breakdown voltage, while the second doped region has higher concentration optimized for on-resistance. This local quality differentiation maintains transistor performance despite overall device scaling
2Length of moving object
If conventional MOSFET structures are used in scaled-down devices, then device size is reduced, but Kirk effect and parasitic BJT action increase degrading performance
Solution Approach 1:
The first doped region acts as an intermediary between the gate and the second doped region, moderating the electric field distribution. This intermediate layer with lower doping concentration reduces the peak electric field at the drain junction, thereby suppressing the Kirk effect and parasitic BJT action that would otherwise be exacerbated in scaled-down conventional structures
Solution Approach 2:
The doping concentration parameter is changed across different regions to address harmful effects. By implementing a gradient doping profile (lower concentration in the first region, higher in the second), the electric field distribution is modified to suppress the Kirk effect and parasitic BJT action, allowing smaller device dimensions without performance degradation
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
The LDD region improves drain current characteristics and maintains high breakdown voltage, effectively addressing the Kirk effect and parasitic BJT issues, thereby enhancing transistor performance in scaled-down semiconductor devices.
Implementation Method 1
a doped region in the drift region and between the drain region and the gate structure
Data Source
AI summary
A semiconductor device includes a gate structure, a drift region, a source region, a drain region, a first doped region, and a second doped region. The gate structure is over a semiconductor substrate. The drift region is in the semiconductor substrate and laterally extends past a first side of the gate structure. The source region is in the semiconductor substrate and adjacent a second side of the gate structure opposite the first side. The drain region is in the drift region. The first doped region is in the drift region and between the drain region and the gate structure. The second doped region is within the drift region. The second doped region forms a P-N junction with the first doped region at a bottom surface of the first doped region.