RC-IGBT Diffusion Layer Layout for Lower-Cost Reverse Withstand Design
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Solution Overview
Problem
The manufacturing cost of reverse conducting IGBTs (RC-IGBTs) is increased due to the requirement of forming p-type diffusion layers of different depths, which complicates the manufacturing process.
Innovation Solution
The RC-IGBT design includes a semiconductor substrate with a cell region, termination region, and wiring region, where a diffusion layer of a second conductivity type is formed simultaneously in all regions, including an IGBT region, diode region, and termination region, with trench gates penetrating the substrate, and the depth of the base layer is set to be less than active trench gates but equal to or greater than anode, wiring well, and termination well layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If p-type diffusion layers of different depths are formed in the termination region and IGBT region, then the reverse withstand voltage is properly held, but the manufacturing cost increases and manufacturing process becomes complex
Solution Approach 1:
The patent merges the formation of p-type diffusion layers across different regions (IGBT region and termination region) into a single simultaneous manufacturing step. The p-type base layer in the IGBT region and the p-type termination well layer in the termination region are formed together in one diffusion process, eliminating the need for separate sequential steps and reducing manufacturing complexity and cost while maintaining the required different depths through selective masking and doping conditions
2Reliability
If p-type diffusion layers of different depths are formed in the termination region and IGBT region, then the reverse withstand voltage is properly held, but the manufacturing process becomes complex
Solution Approach 1:
The patent combines multiple diffusion steps into one simultaneous process. By using a single p-type diffusion step with appropriate masking patterns and doping conditions, both the p-type base layer and p-type termination well layer are formed in the same process batch, significantly simplifying the manufacturing process flow while achieving the required depth differentiation through process parameter control
3Ease of manufacture
If the base layer depth is made less than active trench gate depth, then simultaneous formation of diffusion layers is enabled, but the IGBT region structure must be carefully designed
Solution Approach 1:
The patent controls the depth of p-type diffusion layers by adjusting diffusion parameters such as temperature, time, and doping concentration. By optimizing these parameters, the base layer depth is precisely controlled to be less than the active trench gate depth, enabling simultaneous formation while maintaining manufacturing precision through parameter optimization rather than relying solely on geometric constraints
Data Source
AI summary
An RC-IGBT includes a semiconductor substrate having a cell region, a wiring region, and a termination region. The semiconductor substrate includes a diffusion layer of a second conductivity type provided on a first main surface side of a drift layer in an IGBT region, a diode region, the wiring region, and the termination region. The diffusion layer includes a base layer in the IGBT region, an anode layer in the diode region, a wiring well layer in the wiring region, and a termination well layer in the termination region. A depth of the base layer is less than depths of a plurality of trench gates, and is equal to or more than depths of the anode layer, the wiring well layer, and the termination well layer.