IGBT Base Region Segmentation for Breakdown Immunity
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Solution Overview
Problem
Semiconductor devices, particularly IGBTs, face challenges with breakdown immunity due to local current concentration, which can lead to element breakdown and parasitic transistor activation by current filaments.
Innovation Solution
The semiconductor device design includes specific layer configurations and electrode arrangements, such as n-type and p-type semiconductor layers with varying impurity concentrations and surface densities, along with control electrodes and insulating films, to manage current distribution and prevent parasitic transistor activation, thereby enhancing breakdown immunity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional IGBT structure is used, then device simplicity is maintained, but breakdown immunity deteriorates due to current filament concentration
Solution Approach 1:
The base region is segmented into multiple semiconductor layers (first base layer, second base layer, third base layer) with different conductivity types and impurity concentrations. This segmentation creates multiple current paths that distribute current density, preventing localized current filaments that cause breakdown in conventional single-layer structures.
Solution Approach 2:
Each semiconductor layer is assigned specific local properties: the first base layer has high impurity concentration for low resistance, the second base layer has intermediate properties for current distribution, and the third base layer has low impurity concentration for high breakdown voltage. This local quality differentiation optimizes both reliability and current distribution throughout the device.
2Use of energy by moving object
If impurity concentration is increased to reduce resistance, then conductivity improves, but current filament concentration increases causing breakdown
Solution Approach 1:
The patent systematically varies impurity concentration parameters across different layers: the first base layer uses high impurity concentration (1E16-1E18 atoms/cm³) for low resistance, while the third base layer uses lower concentration (1E14-1E16 atoms/cm³) for high breakdown voltage. This parameter optimization across layers simultaneously achieves good conductivity and breakdown immunity.
Solution Approach 2:
Different regions of the base region are assigned different impurity concentrations tailored to their specific functional requirements. The emitter-side layer prioritizes conductivity, the collector-side layer prioritizes breakdown voltage, and intermediate layers provide transition and current distribution, resolving the contradiction between conductivity and breakdown immunity.
3Ease of manufacture
If single-layer base region is used, then manufacturing is simplified, but current distribution is poor leading to parasitic transistor activation
Solution Approach 1:
The base region is divided into three distinct semiconductor layers that can be fabricated using standard sequential deposition and doping techniques. While slightly more complex than a single layer, the segmented structure remains compatible with conventional manufacturing processes while providing superior current distribution that prevents parasitic transistor activation.
Solution Approach 2:
The second base layer acts as an intermediary between the high-conductivity first base layer and the high-breakdown-voltage third base layer. This intermediate layer facilitates smooth current transition and distribution, preventing current concentration that would activate parasitic transistors, while maintaining manufacturing feasibility through standard layer-by-layer fabrication.
Data Source
AI summary
A semiconductor device includes a semiconductor part, first and second electrodes, and a control electrode. The semiconductor part is provided between the first and second electrodes. The semiconductor part includes first to seventh layers. The second of a second conductivity type is provided between the first layer of a first conductivity type and the first electrode. The third and fourth layers of the first conductivity type are arranged along the second layer between the second layer and the first electrode. The fifth layer of the second conductivity type is provided between the second electrode and the first layer. The sixth and seventh layers are arranged along the fifth layer between the first and fifth layers. The sixth and seventh layers include the first-conductivity-type impurities with first and second surface densities, respectively. The first surface density is greater than the second surface density.