Superjunction High-Voltage FET Structure for Breakdown and Hot Carrier Control
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Solution Overview
Problem
High voltage field effect transistors often suffer from surface breakdown voltage due to complex extended low doped drain (LDD) structures, which increase process complexity and cost while reducing breakdown voltage.
Innovation Solution
The implementation of superjunction structures with lateral p-n junctions, including source-side and drain-side extension regions with interlaced counter-doped rails, reduces hot carrier injection and maintains high breakdown voltage without significantly increasing doping concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex extended low doped drain (LDD) structures are used to improve surface breakdown characteristics, then breakdown voltage is improved, but process complexity and manufacturing cost increase
Solution Approach 1:
The drain extension region is segmented into multiple vertically stacked regions with different doping concentrations (first through fourth doping concentrations), creating a graded structure that improves surface breakdown characteristics while simplifying the overall process compared to complex extended LDD structures
Solution Approach 2:
Different regions of the drain extension structure are assigned different doping concentrations locally, with higher doping near the surface and lower doping deeper in the structure, optimizing both breakdown voltage and process simplicity through localized property variation
2Reliability
If complex extended low doped drain (LDD) structures are used to improve surface breakdown characteristics, then breakdown voltage is improved, but manufacturing cost increases
Solution Approach 1:
The drain extension region is divided into multiple vertically stacked regions with different doping concentrations, achieving improved breakdown characteristics through a structured approach that reduces manufacturing complexity and cost compared to conventional methods
3Reliability
If doping concentration is increased to improve breakdown voltage, then breakdown voltage is improved, but hot carrier injection increases
Solution Approach 1:
The drain extension structure implements spatially varying doping concentrations at different vertical levels, with higher doping concentrations near the surface and lower concentrations deeper in the structure, thereby maintaining high breakdown voltage while reducing hot carrier injection through localized doping optimization
Solution Approach 2:
The extension region is segmented into multiple doping zones that independently control electrical characteristics, allowing the structure to achieve high breakdown voltage through cumulative effect while minimizing hot carrier generation in any single high-field region
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 superjunction structure effectively reduces hot carrier injection and maintains high breakdown voltage, suitable for high voltage operations above 20V, while simplifying the manufacturing process and reducing costs.
Implementation Method 1
forming a source-side extension region and a drain-side extension region by implanting dopants of a second conductivity type into an upper portion of the semiconductor material layer employing at least the gate electrode as a first ion implantation mask
Implementation Method 2
forming source-side counter-doped rails and drain-side counter-doped rails within upper portions of the source-side extension region and the drain-side extension region, respectively by implanting dopants of the first conductivity type
Data Source
AI summary
A field effect transistor includes a semiconductor channel having a doping of a first conductivity type, a gate structure overlying the semiconductor channel, a source region and a drain region, a source-side extension region including a source-side-extension plate portion and source-side-extension rail portions that overlie the source-side-extension plate portion, source-side counter-doped rails having a doping of the first conductivity type, a drain-side extension region including a drain-side-extension plate portion and drain-side-extension rail portions that overlie the drain-side-extension plate portion, and drain-side counter-doped rails interlaced with the drain-side-extension rail portions. A first superjunction structure is provided between the source-side counter-doped rails and the source-side extension region. A second superjunction structure is provided between the drain-side counter-doped rails and the drain-side extension region.