Power Semiconductor Device With Segmented Epitaxial Layers
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Solution Overview
Problem
Existing power semiconductor devices, particularly IGBTs, face challenges with resistivity dispersion and switching speed due to non-uniform dopant concentration in substrates, leading to increased voltage overshoot and switching losses.
Innovation Solution
A power semiconductor device is fabricated using a first epitaxial layer with a higher doping concentration than a second epitaxial layer, where the first epitaxial layer is polished to form a field stop layer with a thickness of 5 to 25 μm and resistivity dispersion of less than 5%, and the second epitaxial layer has a trench structure with a gate insulating layer and emitter electrode, reducing resistivity dispersion and enhancing voltage endurance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick substrate is used to reduce electric field, then voltage endurance is improved, but switching loss increases and device size increases
Solution Approach 1:
The substrate is segmented into two functional layers: a first epitaxial layer with higher doping concentration (1E15 to 1E16 atoms/cm³) serving as a field stop layer, and a second epitaxial layer with lower doping concentration (1E13 to 1E14 atoms/cm³) serving as the drift region. This segmentation allows the field stop layer to terminate electric field lines and reduce voltage overshoot, while the thinner overall structure reduces switching loss and device size compared to using a single thick substrate.
2Loss of energy
If dopant concentration is increased to reduce on-resistance, then conduction loss is reduced, but voltage overshoot increases
Solution Approach 1:
Different regions of the device are assigned different doping concentrations to optimize local functions. The first epitaxial layer has higher doping concentration (1E15 to 1E16 atoms/cm³) to reduce on-resistance and conduction loss in the drift region, while the second epitaxial layer has lower doping concentration (1E13 to 1E14 atoms/cm³) to serve as a high-voltage drift region with longer carrier lifetime. This local differentiation allows simultaneous optimization of conduction and voltage characteristics.
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 solution achieves uniform resistivity and reduced switching losses, improving the reliability and stability of the power semiconductor device by minimizing voltage overshoot and enhancing switching speed.
Implementation Method 1
the first epitaxial layer is polished to form a field stop layer with a thickness of 5 to 25 μm and resistivity dispersion of less than 5%
Implementation Method 2
a first epitaxial layer with a higher doping concentration than a second epitaxial layer
Data Source
AI summary
Provided is a power semiconductor device and a fabrication method thereof are provided. The power semiconductor device includes: a first epitaxial layer; a collector layer formed on one side of the first epitaxial layer; and a second epitaxial layer formed on another side of the first epitaxial layer, the first epitaxial layer having a higher doping concentration than the second epitaxial layer.