Drift-Layer-Free MOSFET Structure for High Breakdown Voltage
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Solution Overview
Problem
Conventional MOSFETs face a trade-off between on-resistance and breakdown voltage due to the presence of a drift layer, where low on-resistance results in decreased breakdown voltage and high breakdown voltage increases on-resistance.
Innovation Solution
A semiconductor device is developed without a drift layer, featuring a first semiconductor layer, a source portion, a source electrode, a second semiconductor layer, a drain electrode, and a gate electrode, where the shortest distance between the inversion layer and the drain electrode satisfies a specific formula, and the impurity concentration in the source portion is higher than in the first semiconductor layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a drift layer with low impurity concentration is formed to improve breakdown voltage, then breakdown voltage increases, but on-resistance increases due to high drift resistance
Solution Approach 1:
The patent removes the drift layer from the conventional MOSFET structure, extracting the problematic component that causes the trade-off between breakdown voltage and on-resistance. By eliminating the drift layer, the invention achieves both high breakdown voltage and low on-resistance simultaneously, as confirmed by the abstract stating 'a novel semiconductor device for high breakdown voltage, which has no drift layer'
Solution Approach 2:
The patent changes the impurity concentration parameter in the semiconductor layer to achieve the desired performance. Specifically, the semiconductor layer has an impurity concentration of 1×10^14 to 1×10^16 atoms/cm³, which is higher than the conventional drift layer, allowing the device to achieve high breakdown voltage without the associated high on-resistance penalty
2Reliability
If the impurity concentration in the drift layer is increased to reduce drift resistance, then on-resistance decreases, but breakdown voltage decreases due to increased electric field strength
Solution Approach 1:
The patent eliminates the drift layer entirely, removing the source of the trade-off between on-resistance and breakdown voltage. This extraction allows the device to achieve low on-resistance through direct carrier transport in the semiconductor layer without the resistance penalty of a drift layer, while maintaining high breakdown voltage through optimized impurity concentration in the remaining structure
Solution Approach 2:
The patent optimizes the impurity concentration in the semiconductor layer (1×10^14 to 1×10^16 atoms/cm³) to achieve the desired balance of low on-resistance and high breakdown voltage without requiring a drift layer. This parameter change in the semiconductor layer replaces the need for a separate drift layer with controlled impurity concentration
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 design allows for reduced on-resistance and higher breakdown voltage without the limitations of the drift layer trade-off, achieving improved performance in semiconductor devices.
Implementation Method 1
a gate electrode arranged on at least one selected from surfaces of the first semiconductor layer via a gate insulating film interposed therebetween and capable of forming by an applied electric field, an inversion layer in a region of the first semiconductor layer near the surface of the first semiconductor layer contacting the gate insulating film
Implementation Method 2
a drain electrode separated from the inversion layer and arranged in Schottky contact with the second semiconductor layer
Data Source
AI summary
The present invention provides a novel semiconductor device for high breakdown voltage having no drift layer. The semiconductor device includes a first semiconductor layer of a first conductivity type which is either a p-type or an n-type conductivity type, a source portion arranged so as to be in contact with the first semiconductor layer and configured as a semiconductor portion of a second conductivity type different from the first conductivity type, a source electrode arranged in ohmic contact with the source portion, a gate electrode arranged on at least one selected from surfaces of the first semiconductor layer via a gate insulating film interposed therebetween and capable of forming by an applied electric field, an inversion layer in a region of the first semiconductor layer near the surface of the first semiconductor layer contacting the gate insulating film, a second semiconductor layer of the first conductivity type arranged so as to be in contact with the inversion layer, and a drain electrode separated from the inversion layer and arranged in Schottky contact with the second semiconductor layer.