Guard Rings with Flared Portions for High Voltage Stability
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Solution Overview
Problem
Semiconductor devices, particularly power devices like IGBTs, face instability in breakdown voltage due to voltage gradients within the substrate, making it challenging to achieve high breakdown voltage in a small area, which is essential for reducing chip size and increasing circuit density.
Innovation Solution
The implementation of guard rings with flared portions and a clamp diode around semiconductor elements, which are spaced uniformly and biased to different potentials, helps maintain breakdown voltage while reducing the peripheral region's width, thereby achieving higher breakdown voltages in a reduced space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the device size is reduced to increase circuit density, then the chip area decreases, but the breakdown voltage stability deteriorates due to voltage gradients in the substrate
Solution Approach 1:
The device is segmented into multiple regions with different doping concentrations and guard ring structures. The substrate is divided into a drift region with first doping concentration and a buffer region with second doping concentration, creating distinct functional zones that manage voltage distribution and improve breakdown voltage stability in the reduced chip area.
Solution Approach 2:
Different regions of the device are assigned different local properties: the drift region has one doping concentration optimized for voltage blocking, while the buffer region has a different doping concentration for field control. Guard rings are strategically positioned with specific doping profiles to locally manage electric field distribution, ensuring voltage stability in the compact design.
2Reliability
If guard rings are added to improve breakdown voltage stability, then the voltage control improves, but the device complexity increases
Solution Approach 1:
Multiple functions are merged into the guard ring structure: they serve as both electrical field control elements for voltage stability and as part of the overall device geometry for compactness. The guard rings are integrated with the drift and buffer regions, combining voltage blocking, field management, and structural organization into a unified design that improves reliability without proportionally increasing complexity.
Data Source
AI summary
An electronic device including a substrate, a semiconductor element disposed on the substrate, and a plurality of guard rings at least partially surrounding the semiconductor element, wherein adjacent guard rings are spaced apart by a substantially uniform distance as measured along an entire length of the guard rings, and at least one of the plurality of guard rings has a flared portion. In an embodiment, at least one of the plurality of guard rings electrically floats. In another embodiment, the plurality of guard rings are disposed at least partially below a primary surface of the substrate. In an embodiment, the electronic device is a high voltage MOSFET or an IGBT.