SiC Substrate Hole Layout for Thermal Isolation in HEMT Devices
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Solution Overview
Problem
In high electron mobility transistors with nitride semiconductor layers on silicon carbide substrates, heat generated in transistors is efficiently conducted to adjacent passive or active elements through the substrate, leading to increased temperatures and potential deviations in element characteristics.
Innovation Solution
A semiconductor device with a silicon carbide substrate featuring a hole with reduced internal thermal conductivity between the transistor and an element, formed by partially removing the substrate, and a metal layer connected via a via hole to suppress heat conduction, using a mask layer to create the hole with a smaller opening area on the substrate's bottom surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If heat is conducted through the silicon carbide substrate from the transistor to adjacent elements, then thermal management is simplified, but the adjacent elements experience temperature rises and characteristic deviations
Solution Approach 1:
The patent extracts the heat conduction path from the continuous silicon carbide substrate by creating holes that remove portions of the substrate between the transistor and adjacent elements. This discontinuities the thermal conduction path, preventing heat from reaching adjacent elements while maintaining the substrate's structural support function.
Solution Approach 2:
The patent applies local quality modification by creating regions of different thermal conductivity within the substrate. The areas with holes have reduced thermal conductivity compared to the solid substrate regions, allowing heat to be conducted efficiently in areas needing thermal management while blocking heat flow to sensitive adjacent elements.
2Strength
If the silicon carbide substrate is made continuous for structural integrity, then mechanical strength is maintained, but heat conduction to adjacent elements increases
Solution Approach 1:
The patent segments the continuous silicon carbide substrate by introducing holes that create discontinuities. These segmented regions maintain overall structural integrity while disrupting the thermal conduction path to adjacent elements, effectively decoupling mechanical support from heat transfer functions.
Solution Approach 2:
The holes act as intermediary structures that mediate between the transistor heat source and adjacent elements. By introducing these intermediate void spaces, the patent prevents direct thermal contact while maintaining the substrate's mechanical framework.
3Temperature
If a hole is created in the silicon carbide substrate to suppress heat conduction, then thermal isolation is improved, but manufacturing complexity increases
Solution Approach 1:
The patent introduces a porous or discontinuous structure into the silicon carbide substrate by creating holes. This porous configuration reduces thermal conductivity while maintaining the substrate's mechanical properties, achieving thermal isolation without requiring completely complex structural modifications.
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
Effectively suppresses heat conduction from the transistor to adjacent elements, maintaining desired characteristics by creating a thermal conduction suppressing region with lower thermal conductivity than the substrate, thereby preventing temperature rises in passive or active elements.
Implementation Method 1
the hole has an internal thermal conductivity smaller than a thermal conductivity of the silicon carbide substrate
Data Source
AI summary
A semiconductor device includes a silicon carbide substrate, a nitride semiconductor layer provided on a top surface of the silicon carbide substrate, a transistor provided on the nitride semiconductor layer, and an element provided on or above the silicon carbide substrate, wherein the silicon carbide substrate has a hole that is provided between the transistor and the element, the hole is formed by removing at least a part of the silicon carbide substrate from a bottom surface of the silicon carbide substrate and an internal thermal conductivity of the hole is smaller than a thermal conductivity of the silicon carbide substrate.