Semiconductor Epitaxial Layer Thickness Optimization for Power MOSFETs
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Solution Overview
Problem
In-vehicle semiconductor devices with power MOSFETs face challenges in reducing ON-resistance and preventing reverse current flow when the battery connection is reversed, as existing solutions either increase ON-resistance or require complex structures.
Innovation Solution
A semiconductor device design featuring a semiconductor substrate with distinct regions and thicknesses for the epitaxial layer in the first and second regions, allowing for optimized thickness adjustments to minimize ON-resistance while ensuring breakdown voltage, even when the battery is connected in reverse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the thickness of the epitaxial layer in the first region is reduced to minimize ON-resistance, then the ON-resistance decreases, but the breakdown voltage may be compromised
Solution Approach 1:
The patent applies local quality by creating different epitaxial layer thicknesses in different regions: the first region (where the power MOSFET is formed) has a thinner epitaxial layer to reduce ON-resistance, while the second region has a thicker epitaxial layer to maintain breakdown voltage. This spatial differentiation of thickness allows each region to be optimized for its specific function without compromising the other.
2Reliability
If two power MOSFETs are connected in series to prevent reverse current flow, then reverse current protection is achieved, but the ON-resistance increases
Solution Approach 1:
The patent extracts the reverse current protection function from the power MOSFET circuit by forming a separate semiconductor element (such as a Zener diode or breakdown structure) in the second region. This extracted protection mechanism operates independently through breakdown voltage characteristics, allowing the power MOSFET to maintain low ON-resistance without being forced into a series connection configuration that would increase resistance.
Data Source
AI summary
A semiconductor substrate has a first main surface and a second main surface opposite to each other, and includes a substrate body and an epitaxial layer. A first power MOSFET is formed in a first region defined in the semiconductor substrate, and a second power MOSFET is formed in a second region defined in the semiconductor substrate. A thickness of the epitaxial layer in the first region located between a first main surface's first portion and a second main surface's first portion is less than a thickness of the epitaxial layer in the second region located between a first main surface's second portion and a second main surface's second portion.