Floating Guard Rings for High-Voltage Semiconductor Devices
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Solution Overview
Problem
Existing high-voltage semiconductor devices face challenges in achieving higher breakdown voltages without increasing input capacitance, which leads to slower transistor speeds and larger gate currents during switching.
Innovation Solution
The implementation of guard rings, which are floating electrodes made of electrically conductive material isolated from the source, drain, and gate electrodes, positioned between the gate and drain electrodes, with an insulating layer in between, helps shape the electric field to reduce peak electric fields and increase breakdown voltages without increasing capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If field plates are used to increase breakdown voltage, then device breakdown voltage is improved, but input capacitance increases leading to slower transistor speeds
Solution Approach 1:
A guard ring is introduced as an intermediary floating electrode between the gate and drain electrodes. This guard ring is electrically isolated from both the gate and drain through insulating layers, allowing it to shape the electric field and increase breakdown voltage without being electrically connected to the gate, thereby avoiding the capacitance increase that would occur with a traditional field plate connected to the gate.
Solution Approach 2:
The electric field management function is segmented into two independent components: the gate electrode for controlling channel conduction and the floating guard ring for field shaping. This segmentation allows the guard ring to perform field plate functionality (increasing breakdown voltage) without being electrically connected to the gate, thus avoiding the harmful capacitance effect while maintaining fast switching speeds.
2Reliability
If field plates are used to increase breakdown voltage, then device breakdown voltage is improved, but gate current increases during switching
Solution Approach 1:
The floating guard ring serves as an intermediary that shapes the electric field to increase breakdown voltage without being electrically connected to the gate. Since the guard ring is isolated by insulating layers, it does not create additional capacitive loading on the gate, thereby reducing the gate current required during switching operations compared to traditional field plate structures.
3Reliability
If guard rings are positioned close to the semiconductor material layer, then field shaping effectiveness is improved, but risk of device breakdown increases
Solution Approach 1:
An insulating layer is introduced as a mediator between the floating guard ring and the semiconductor material layer. This insulating layer allows the guard ring to be positioned close to the semiconductor material for effective field shaping while preventing direct contact that would cause breakdown. The insulating layer acts as a protective barrier that enables close positioning without the harmful effects of direct contact.
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 design allows for higher voltage operation while maintaining fast switching speeds and reducing switching losses by effectively managing the electric field and preventing device breakdown.
Implementation Method 1
A portion of an insulating layer is between at least a portion of the guard ring and the semiconductor material layer
Implementation Method 2
A guard ring is a floating electrode formed of electrically conductive material above a semiconductor material layer... helps shape the electric field to reduce peak electric fields and increase breakdown voltages
Data Source
AI summary
Semiconductor devices with guard rings are described. The semiconductor devices may be, e.g., transistors and diodes designed for high-voltage applications. A guard ring is a floating electrode formed of electrically conducting material above a semiconductor material layer. A portion of an insulating layer is between at least a portion of the guard ring and the semiconductor material layer. A guard ring may be located, for example, on a transistor between a gate and a drain electrode. A semiconductor device may have one or more guard rings.