HFET Shield Wrap Segmentation for EMI Reduction
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Solution Overview
Problem
High-voltage field effect transistors (HFETs) in switched-mode power converters experience electromagnetic interference and degradation due to high-frequency electromagnetic fields, which can damage surrounding components and reduce device lifetime.
Innovation Solution
A shield wrap is integrated around the HFET to contain and reduce electromagnetic radiation, preventing interference and degradation by covering the device surface without creating a DC electrical path between the source and drain electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shield wrap is added around the HFET to contain electromagnetic radiation, then electromagnetic interference and device degradation are reduced, but device complexity and manufacturing complexity increase
Solution Approach 1:
The shield wrap is divided into multiple discrete metal segments (first shield segment, second shield segment, third shield segment) rather than a continuous shield. These segments are positioned at different locations around the HFET and connected through capacitive coupling, allowing the shield to contain electromagnetic radiation while reducing complexity compared to a complete continuous enclosure.
Solution Approach 2:
Capacitive coupling acts as an intermediary mechanism to connect the discrete metal segments of the shield wrap. The capacitive coupling allows electromagnetic field containment while maintaining electrical isolation, solving the contradiction between effective shielding and structural simplicity.
2Object-affected harmful factors
If a shield wrap is integrated around the HFET, then electromagnetic radiation is contained and interference is reduced, but manufacturing precision requirements increase
Solution Approach 1:
Instead of requiring uniform precision throughout an entire continuous shield, the segmented shield wrap allows different regions to have different positioning tolerances. The first, second, and third shield segments can be positioned independently with relaxed precision requirements, as long as they maintain the overall shielding geometry around the HFET.
Solution Approach 2:
The segmentation of the shield into multiple discrete segments reduces the cumulative precision requirements compared to a single continuous shield. Each segment can be manufactured and positioned independently, allowing for easier assembly and reduced overall manufacturing precision demands while maintaining effective electromagnetic containment.
3Reliability
If the shield wrap uses discrete metal segments with capacitive coupling, then DC electrical path between source and drain is avoided, but shield effectiveness may be reduced
Solution Approach 1:
Capacitive coupling serves as an intermediary that provides electrical isolation (blocking DC current between source and drain) while simultaneously maintaining electromagnetic shielding effectiveness. The capacitive coupling allows AC electromagnetic fields to be contained while blocking DC electrical conduction, resolving the contradiction between electrical isolation and shielding effectiveness.
Solution Approach 2:
The shield structure changes the electrical parameters by using capacitive coupling instead of direct conductive connections between metal segments. This parameter change allows the shield to block DC electrical paths while maintaining effectiveness against electromagnetic radiation through the capacitive coupling mechanism.
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
The shield wrap effectively confines electromagnetic radiation, improving the HFET's performance and longevity by reducing capacitive coupling and electromagnetic interference, leading to more stable operation at higher drain voltages.
Implementation Method 1
A shield wrap is integrated around the HFET to contain and reduce electromagnetic radiation
Implementation Method 2
improving the HFET's performance and longevity by reducing capacitive coupling and electromagnetic interference
Data Source
AI summary
A semiconductor device includes a heterostructure field effect transistor (HFET) having an active region in a semiconductor film between a source electrode and a drain electrode, where a gate electrode is over a portion of the active region and is configured to modulate a conduction channel in the active region. The semiconductor device also includes a first passivation film over the active region and an encapsulation film over the first passivation film. A first metal pattern is disposed on the encapsulation film, and the first metal pattern includes a shield wrap over the majority of the active region and is electrically connected to the source electrode. A gap is defined in the first metal pattern and the gap separates the shield wrap from a portion of the first metal pattern that is connected to the drain electrode, and the gap is not formed over the active region.