GaN Device Thermal Design via Segmented Cells and Vias
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Solution Overview
Problem
Gallium nitride material devices face challenges in thermal management, as increased device temperature leads to reduced carrier mobility, sheet charge density, and higher leakage currents, limiting their ability to operate at high power densities.
Innovation Solution
The design involves arranging transistors in cells with optimized spacing and staggered configurations, along with thermally conductive packaging and selective substrate removal to enhance heat conduction, including the use of vias and thermally conductive material regions to improve thermal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If transistors are arranged in a compact configuration to increase device integration, then device area is reduced, but thermal resistance increases and heat removal becomes inefficient
Solution Approach 1:
The device is segmented into multiple independent cells, each containing transistors with their own heat removal pathways. This segmentation allows heat to be distributed and removed from multiple locations simultaneously, reducing overall thermal resistance while maintaining compact device area.
Solution Approach 2:
Heat removal pathways are extended into the vertical dimension by incorporating through-substrate vias and heat sinks positioned beneath the active region. This three-dimensional thermal management approach enables efficient heat extraction without increasing the planar device footprint.
2Power
If device power density is increased to improve output power, then productivity is improved, but device temperature increases leading to degraded electrical properties
Solution Approach 1:
Thermally conductive intermediary materials are introduced between the active region and the heat sink to facilitate efficient heat transfer. These intermediaries provide low-thermal-resistance pathways that enable high power density operation while maintaining acceptable junction temperatures and electrical properties.
Solution Approach 2:
The thermal conductivity parameter of the packaging materials and heat removal structures is significantly increased compared to conventional designs. This parameter change enables the device to dissipate heat more effectively, allowing operation at high power densities without degrading electrical properties due to excessive temperature rise.
3Ease of manufacture
If conventional packaging with standard thermal conduction is used, then manufacturing simplicity is maintained, but thermal resistance is too high for high power density operation
Solution Approach 1:
The packaging structure employs composite materials with superior thermal conductivity, combining highly conductive heat sink materials with thermally enhanced interconnect structures. This composite approach achieves low thermal resistance while maintaining manufacturing feasibility through established fabrication processes.
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 reduces thermal resistance, enabling gallium nitride material devices to operate at high power densities while maintaining excellent electrical properties, increasing reliability and extending device lifetime.
Implementation Method 1
the layout involves grouping the transistors into cells and spacing the cells an appropriate distance from each other... The devices were attached to high thermal conductivity Cu-Mo laminate... single-ended ceramic packages
Implementation Method 2
Each cell is separated from an adjacent cell by an inter-cell spacing, wherein each inter-cell spacing is greater than each gate pitch
Data Source
AI summary
Gallium nitride material devices and methods associated with the devices are described. The devices may be designed to provide enhanced thermal conduction and reduced thermal resistance. The increased thermal conduction through and out of the gallium nitride devices enhances operability of the devices, including providing excellent RF operation, reliability, and lifetime.