RCFS IGBT Vertical Field Stop Depth for Parasitic Zener Diode Suppression
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Solution Overview
Problem
Conventional insulated gate bipolar transistors (IGBTs) face issues with the formation of parasitic Zener diodes due to the lateral alignment of N+ and P-type doped layers, which affects their performance and breakdown voltage.
Innovation Solution
The manufacturing process involves creating trenches on the substrate with specific depth profiles for ion implantation, forming irregular PN junctions on the backside, preventing the formation of Zener diodes by ensuring the field stop depth is greater than the trench depth, thereby enhancing the IGBT's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If N+ type doped layer and P type doped layer are formed on the same horizontal plane of the backside of the substrate, then the manufacturing process is simplified, but lateral Zener diode forms which degrades device performance
Solution Approach 1:
The patent introduces a vertical depth dimension to separate the N+ and P type doped layers. Instead of placing them on the same horizontal plane, the N+ field stop layer is positioned at a first depth from the back surface while the P type layer is positioned at a second depth, creating a vertical separation that prevents lateral Zener diode formation while maintaining manufacturing feasibility through controlled ion implantation processes
2Reliability
If field stop depth is increased to prevent Zener diode formation, then breakdown voltage is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies precise parameter ranges for the ion implantation process: the N+ field stop layer is implanted to a depth of 0.5-2.0 micrometers from the back surface, while the P type layer is implanted to a depth of 2.0-5.0 micrometers. These controlled parameter ranges achieve adequate vertical separation to prevent Zener diode formation while maintaining manufacturability through standard ion implantation capabilities
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 approach effectively suppresses the formation of parasitic Zener diodes, improving the high-performance characteristics of the IGBT by maintaining an irregular PN junction, thus enhancing breakdown voltage and overall device performance.
Implementation Method 1
performing an ion implantation process on back side of the first conductive type substrate to form a first conductive type field stop ion implantation with a field stop depth from a back face of the first conductive type substrate
Data Source
AI summary
A high-performance reverse-conduction field-stop (RCFS) insulated gate bipolar transistor (IGBT) includes a first conductive type substrate, a plurality of trenches defined on a bottom face of the substrate, a plurality of first conductive type doping regions formed on bottom face of the trenches, a second conductive type doping region formed on bottom face of the substrate, and a first conductive type field stop doping region formed in the substrate and separated from the bottom face of the substrate by a field stop depth, where the field stop depth is larger than a depth of the trench. Due to a separation between the first conductive type doping regions and the second conductive type doping region, Zener diode can be prevented from forming on bottom side of the substrate and the performance of IGBT can be accordingly enhanced.