Shield Electrode Segmentation in Power MOSFETs
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Solution Overview
Problem
Existing semiconductor components face challenges in optimizing gate-to-drain capacitance, leading to inefficiencies in power switching due to ringing issues in high side FETs, particularly in applications with high source inductance, which can cause system malfunctions and energy dissipation.
Innovation Solution
The solution involves forming trenches with dielectric material and polysilicon shield electrodes, connecting a predetermined percentage of shield electrodes to the gate electrodes to increase gate-to-drain capacitance, and adjusting the series resistance of the shield electrode to mitigate ringing, while also reducing on-resistance and optimizing the accumulation layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If shield electrodes are added to lower gate-to-drain capacitance, then transition rate increases and switching efficiency improves, but switch node ringing increases causing system malfunctions
Solution Approach 1:
The patent applies local quality by making different portions of the shield electrode have different electrical connections. Specifically, a first portion of the shield electrode is connected to the gate electrode while a second portion is connected to the source electrode, creating localized regions with different electrical characteristics to simultaneously achieve capacitance reduction and ringing suppression.
Solution Approach 2:
The shield electrode is segmented into multiple portions with different connections. The first portion connects to the gate electrode and the second portion connects to the source electrode, dividing the shield electrode's function to address both the transition rate improvement and ringing reduction requirements.
2Loss of energy
If gate-to-drain capacitance is reduced for higher efficiency, then power losses decrease, but switch node ringing becomes more pronounced
Solution Approach 1:
Different portions of the shield electrode are connected to different nodes (gate and source) to create local electrical characteristics that simultaneously reduce overall gate-to-drain capacitance for lower power losses while suppressing switch node ringing through the distributed connection structure.
3Object-generated harmful factors
If shield electrode series resistance is increased to reduce ringing, then switch node ringing decreases, but on-resistance increases reducing efficiency
Solution Approach 1:
The shield electrode is divided into portions with different resistance characteristics and connections. The first portion with connection to gate electrode has different resistance than the second portion connected to source, allowing optimization of ringing suppression without excessive increase in overall on-resistance.
Solution Approach 2:
Different portions of the shield electrode are assigned different electrical connections and resistance characteristics, creating local quality variations that enable ringing suppression in critical regions while maintaining low on-resistance in current-carrying regions.
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 reduces switch node ringing, enhances the softness factor, and decreases reverse recovery charge, thereby improving the efficiency and reliability of power MOSFETs by optimizing gate-to-drain capacitance and series resistance.
Implementation Method 1
A dielectric material is formed over portions of the shield electrode... increasing the gate-to-drain capacitance of the FET to a desired value
Implementation Method 2
optimizing the accumulation layer formation... reducing on-resistance
Data Source
AI summary
A semiconductor component that includes gate electrodes and shield electrodes and a method of manufacturing the semiconductor component. A semiconductor material has a device region, a gate contact region, a termination region, and a drain contact region. One or more device trenches is formed in the device region and one or more termination trenches is formed in the edge termination region. Shield electrodes are formed in portions of the device trenches that are adjacent their floors. A gate dielectric material is formed on the sidewalls of the trenches in the device region and gate electrodes are formed over and electrically isolated from the shield electrodes. A gate electrode in at least one of the trenches is connected to at least one shield electrode in the trenches.