GaN FET Front-Side Cooling via Poly-Diamond Dielectric
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Solution Overview
Problem
Current thermal management approaches for GaN devices are inadequate for high power density applications, as they rely on single-side cooling, thermal interface materials that increase thermal resistance and risk of hot-spot formation, and are not compatible with high frequency operation or dual-side cooling.
Innovation Solution
The integration of a high thermal conductivity poly-diamond dielectric on the front-side of GaN devices, combined with electroformed metal heat-sinks and micro-channels for direct thermal contact, allowing for dual-side cooling and minimizing thermal interfaces, thereby enhancing heat spreading and removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If thermal interface materials (TIM) and heat spreaders are used for power amplifier attachment to the heat sink, then thermal contact is improved, but the number of thermal interfaces increases, potential for thermal voids increases, and assembly costs increase
Solution Approach 1:
The patent removes thermal interface materials from the thermal management system, achieving direct bonding between the GaN device and heat sink. This extraction of the TIM layer eliminates the source of thermal voids while maintaining thermal contact through direct metallurgical bonding.
Solution Approach 2:
The patent combines the GaN device mounting with the heat sink attachment into a single direct bonding process. By merging these two previously separate steps (device attachment and thermal interface application), the system eliminates intermediate layers and reduces the number of thermal interfaces.
2Ease of manufacture
If single-side backside heat spreading and cooling is used, then manufacturing is simplified, but heat removal capability is insufficient for high power density GaN devices
Solution Approach 1:
The patent transitions from single-side (one-dimensional) cooling to dual-side (two-dimensional) cooling by adding front-side heat removal capabilities. This dimensional expansion allows heat to be extracted from both the top and bottom of the GaN device, effectively doubling the heat removal pathways.
Solution Approach 2:
The patent segments the heat removal function into two independent cooling paths: front-side cooling through the gate region and backside cooling through the substrate. This segmentation allows each side to handle a portion of the thermal load, increasing overall heat removal capability.
3Reliability
If conventional cooling methods are used, then device operation is maintained, but power handling capability is limited and hot-spot formation risk increases
Solution Approach 1:
The patent applies local quality by placing heat extraction structures directly at the heat generation points (gate and drain regions). The front-side heat sink is positioned adjacent to the gate, and backside cooling is applied near the drain, creating localized thermal management zones that prevent hot-spot formation.
Solution Approach 2:
The patent introduces diamond-like carbon (DLC) as an intermediary material that provides both electrical isolation and thermal conduction pathways. The DLC layer enables direct thermal contact between the gate and front-side heat sink while maintaining electrical insulation, facilitating efficient heat removal without compromising device operation.
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 enables GaN power amplifiers to operate at significantly higher power densities, reducing the number of thermal interfaces and potential for thermal voids, and achieving greater than three times improvement in power handling compared to conventional methods.
Implementation Method 1
a first poly-diamond dielectric thermally coupled to the first gate, wherein the first poly-diamond dielectric facilitates heat removal from a top of the FET
Implementation Method 2
electroformed metal heat-sinks and micro-channels for direct thermal contact, allowing for dual-side cooling and minimizing thermal interfaces
Implementation Method 3
electroformed metal heat-sinks and micro-channels
Data Source
AI summary
Apparatus and methods are provided for heat removal and spreading from a field effect transistor (FET) including a substrate, a first source, a first gate, and a drain on the substrate, and a poly-diamond dielectric thermally coupled to the first gate wherein the poly-diamond dielectric facilitates heat removal from a top of the FET.