Semiconductor Buffer Layer Segmentation for Ringing Inhibition
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Solution Overview
Problem
Semiconductor devices face challenges in inhibiting ringing during turn-off, which can lead to noise and malfunction, particularly in high-voltage and large-current switching applications, where existing designs may result in depletion layer extension and oscillatory waveforms.
Innovation Solution
The semiconductor device incorporates a buffer layer structure with specific impurity concentration profiles, including upper and lower buffer layers with unified and progressively higher average impurity concentrations, and a punch-through prevention layer to control depletion layer extension and prevent ringing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional buffer layer structure is used, then the device can operate, but ringing occurs during turn-off due to depletion layer extension
Solution Approach 1:
The buffer layer is divided into multiple discrete buffer layers (first buffer layer, second buffer layer, third buffer layer) with different impurity concentrations. This segmentation allows each layer to independently control the depletion layer extension at different depths, effectively suppressing ringing and electromagnetic noise during turn-off without compromising device operation.
Solution Approach 2:
Each buffer layer is assigned a specific impurity concentration tailored to its depth and function: the first buffer layer has a concentration of 1×10^15 to 5×10^15 atoms/cm³, the second has 5×10^15 to 1×10^16 atoms/cm³, and the third has 1×10^16 to 5×10^16 atoms/cm³. This local differentiation optimizes depletion layer control at each region, preventing ringing while maintaining proper device operation.
2Strength
If the impurity concentration in the buffer layer is increased to prevent punch-through, then voltage withstanding ability improves, but ringing is exacerbated
Solution Approach 1:
Instead of using a single high-concentration buffer layer, the invention segments the buffer region into multiple layers with progressively increasing impurity concentrations from top to bottom. This allows the lower layers to provide voltage withstanding capability while the upper layers control depletion layer extension, preventing ringing without sacrificing voltage blocking ability.
Solution Approach 2:
The invention changes the impurity concentration parameter across different buffer layers and depths. By creating a gradient where concentration increases from the first buffer layer (1×10^15 to 5×10^15 atoms/cm³) through the second (5×10^15 to 1×10^16 atoms/cm³) to the third (1×10^16 to 5×10^16 atoms/cm³), the device achieves both voltage withstanding and ringing suppression through optimized parameter distribution.
3Device complexity
If a single buffer layer is used, then the structure is simple, but depletion layer control is insufficient leading to ringing
Solution Approach 1:
The buffer region is segmented into three distinct buffer layers, each with specific impurity concentration ranges and thicknesses. This segmentation provides fine-grained control over depletion layer extension at different depths, achieving reliable ringing suppression while maintaining a manageable multi-layer structure that can be fabricated using standard semiconductor processes.
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 configuration effectively inhibits ringing by managing depletion layer growth and maintaining high collector voltage levels without flattening waveforms, reducing noise and ensuring safe operation.
Implementation Method 1
inhibition of a depletion layer extending from the voltage-withstanding main junction at the time of turning off the semiconductor device
Implementation Method 2
the plurality of lower buffer layers are formed so that average impurity concentrations in second sections each extending from the upper end of one of the lower buffer layers to the next lower buffer layer are equal to or higher than the first concentration
Data Source
AI summary
A semiconductor device includes a substrate having an upper surface layer of a second conduction type formed at an upper surface side, a drift layer of a first conduction type formed under the upper surface layer, a buffer layer of the first conduction type formed under the drift layer, and a lower surface layer of the second conduction type formed under the buffer layer, the buffer layer includes a plurality of upper buffer layers provided apart from each other, and a plurality of lower buffer layers provided apart from each other between the plurality of upper buffer layers and the lower surface layer, wherein the plurality of upper buffer layers are formed so that average impurity concentrations in first sections each extending from the upper end of one of the upper buffer layers to the next lower buffer layer are unified as a first concentration.