Mesa Thermal Conduits for Cooling III-V Semiconductor Devices
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Solution Overview
Problem
High junction temperatures in III-V semiconductor devices, such as HBTs and HEMTs, hinder device performance and reliability, and existing solutions like wafer bonding increase process complexity.
Innovation Solution
A method involving the creation of a laterally isolated mesa structure on a semiconductor substrate, with active layers in the upper portion, and forming openings in the dielectric material to remove the bottom portion of the mesa and fill the cavity with a highly thermally conductive material, enhancing heat removal without substrate transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If wafer bonding is used to transfer devices to high thermal conductivity substrate, then heat removal is improved, but process complexity increases
Solution Approach 1:
The invention extracts the thermal management function from the substrate itself and implements it through a separate thermal conduit structure. Instead of requiring wafer bonding to transfer devices to a different substrate, the patent introduces thermal conduits that extend from the device active regions down to the substrate, creating a dedicated heat removal pathway that is integrated into the existing device structure.
Solution Approach 2:
The thermal conduit acts as an intermediary element between the device and the substrate. This conduit serves as a thermal bridge that facilitates heat transfer from the device to the substrate without requiring direct contact or wafer bonding. The conduit can be filled with thermally conductive materials to enhance the thermal coupling while maintaining the monolithic device architecture.
2Temperature
If thermally resistive material layers are replaced with more thermally conductive ones, then heat removal is improved, but device structure complexity increases
Solution Approach 1:
The invention segments the thermal management function into distinct thermal conduits that are spatially separated and individually optimized. Instead of replacing entire material layers across the device, the patent creates discrete thermal pathways that can be selectively positioned under high-power regions, allowing different parts of the device to have different thermal management solutions.
Solution Approach 2:
The thermal conduits are strategically positioned in regions where heat removal is most critical, such as under collector or drain regions of power devices. This localized approach allows the device structure to maintain its original composition in non-critical areas while implementing enhanced thermal management only where needed, thus minimizing overall structural complexity.
3Temperature
If heat spreading dielectric layers are used in back-end processing, then heat removal is improved, but manufacturing steps increase
Solution Approach 1:
The invention merges the thermal management function with the existing device fabrication process by forming thermal conduits using the same lithography and etching steps that define device regions. The thermal conduits are created as part of the standard device architecture rather than as a separate post-processing step, thereby eliminating additional manufacturing complexity.
Solution Approach 2:
The thermal conduit structure serves multiple functions: it provides mechanical support, enables heat removal, and can be integrated with interconnect structures. This multi-functionality reduces the need for separate heat spreading layers and simplifies the overall manufacturing process by consolidating multiple functions into a single structural element.
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 improves heat removal from active device layers while maintaining a monolithic production process, enhancing the thermal conductivity and thus the reliability and performance of high-power semiconductor devices like HBTs and HEMTs.
Implementation Method 1
a bottom portion of the mesa structure and/or a portion of the dielectric material in a region directly adjacent to said bottom portion of the mesa structure is removed relative to the substrate and relative to said active layers. A cavity is thereby formed that is subsequently filled with a highly thermally conductive material, thereby creating a volume of high thermal conductivity configured to remove heat from the device to the substrate
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3~5
AI summary
An isolated mesa structure (2) is produced on a semiconductor substrate (1), with active layers (5,6;36-39) of a semiconductor device integrated in an upper portion of the mesa structure (2). One or more openings (15,45,55,70) are formed in the dielectric material (11,25,27,43) that is isolating the mesa structure (2) on the lateral sides thereof, and a bottom portion of the mesa structure and/or a portion of the dielectric material directly adjacent said bottom portion of the mesa structure is removed. A cavity (16,46,59) is thereby formed that is subsequently filled with a material of high thermal conductivity, thereby creating a thermally conductive volume (17,47,61) configured to remove heat from the device to the substrate.. The invention is also related to a semiconductor component obtainable by applying the method according to the invention.