IGBT Field Stop Region Impurity Gradient for Ringing Suppression
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Solution Overview
Problem
The sudden decrease in depletion layer extension ratio at the OFF time of an IGBT leads to ringing in the voltage rise waveform, causing issues such as electromagnetic wave interference and increased costs in meeting EMI test specifications.
Innovation Solution
A semiconductor device with a field stop region having a gentle impurity concentration gradient in the film thickness direction, where the gradient is larger adjacent to the collector region than the drift region, preventing the depletion layer from reaching the collector region and reducing the extension ratio of the depletion layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a field stop region is disposed between drift region and collector region to prevent depletion layer from reaching collector region, then the IGBT can maintain proper electrical isolation at OFF time, but the sudden decrease in depletion layer extension ratio causes ringing in voltage rise waveform
Solution Approach 1:
The field stop region is designed with non-uniform impurity concentration distribution, where the impurity concentration varies in the film thickness direction. Specifically, the impurity concentration is higher near the collector region interface and lower near the drift region interface, creating different electrical properties in different parts of the field stop region to gradually control depletion layer extension and suppress ringing
Solution Approach 2:
The invention changes the impurity concentration parameter within the field stop region by creating a gradient distribution in the film thickness direction. This parameter variation allows the depletion layer to extend more gradually through the field stop region, preventing the sudden extension ratio decrease that causes ringing, while still maintaining proper electrical isolation
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 semiconductor device effectively suppresses ringing in the voltage rise waveform at the OFF time, reducing electromagnetic interference and maintaining compliance with EMI test specifications while minimizing costs.
Implementation Method 1
By the field stop region, a depletion layer that extends from an upper surface of the drift region is prevented from reaching the collector region at an OFF time
Data Source
AI summary
A semiconductor device includes: a first conductivity-type collector region; a second conductivity-type field stop region disposed on the collector region; a second conductivity-type drift region, which is disposed on the field stop region and has an impurity concentration lower than the field stop region; a first conductivity-type base region disposed on the drift region; and a second conductivity-type emitter region disposed on the base region, wherein an impurity concentration gradient in a film thickness direction of the field stop region is larger in a region adjacent to the collector region than in a region adjacent to the drift region.