Patterned SiC Heteroepitaxy for Cooler GaN HEMTs
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Solution Overview
Problem
GaN based high electron mobility transistors (HEMTs) face performance limitations due to self-heating effects, which degrade channel temperature and transconductance, and increase thermal resistance at the interface between the epitaxial structure and the SiC substrate, hindering efficient heat dissipation.
Innovation Solution
A patterned surface on the SiC substrate is created with trenches or pits to increase the interface area between the epitaxial structure and the substrate, reducing thermal resistance and enhancing heat dissipation by conformally forming a heteroepitaxial layer structure, which facilitates efficient heat transfer and reduces phonon scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flat SiC substrate surface is used for heteroepitaxial growth, then the device structure is simple and manufacturing is easier, but the thermal resistance at the interface between the epitaxial structure and substrate is high, leading to self-heating effects
Solution Approach 1:
The patent transforms the flat two-dimensional substrate surface into a three-dimensional patterned surface with trenches or pits. This dimensional change increases the interface area between the epitaxial structure and substrate, providing more thermal conduction paths and reducing thermal resistance, thereby improving heat dissipation and thermal stability.
Solution Approach 2:
The substrate surface is segmented into multiple regions by forming an array of trenches or pits. This segmentation creates numerous discrete thermal conduction channels distributed across the interface, collectively enhancing heat dissipation efficiency while maintaining structural integrity.
2Reliability
If the interface area between epitaxial structure and substrate is increased by patterning, then thermal resistance is reduced and heat dissipation is enhanced, but the manufacturing process becomes more complex
Solution Approach 1:
The substrate surface is patterned with trenches or pits before the heteroepitaxial growth process. This preliminary action prepares the thermal conduction pathways in advance, allowing the epitaxial layers to conformally grow over the patterned surface and establish efficient thermal contact with the substrate during subsequent processing steps.
3Reliability
If self-heating effects are reduced through improved thermal dissipation, then channel temperature decreases and transconductance improves, but requires additional substrate processing steps
Solution Approach 1:
The substrate surface is modified locally by forming trenches or pits only in specific regions where heat dissipation is critical. This local quality change concentrates thermal management resources where most needed, reducing channel temperature and improving transconductance without uniformly complicating the entire device structure.
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 increased interface area between the epitaxial structure and the substrate significantly reduces thermal resistance, enabling more efficient heat dissipation and improving the reliability and performance of GaN based HEMTs by reducing self-heating effects and enhancing thermal stability.
Implementation Method 1
The increased interface area between the epitaxial structure and the substrate significantly reduces thermal resistance, enabling more efficient heat dissipation
Implementation Method 2
enhancing heat dissipation by conformally forming a heteroepitaxial layer structure, which facilitates efficient heat transfer and reduces phonon scattering
Data Source
AI summary
A method of forming a semiconductor device structure includes patterning a surface of a semiconductor substrate, wherein the semiconductor substrate comprises a material having a thermal conductivity greater than about 50 W/m-K. The method further includes conformally forming a heteroepitaxial layer structure on the surface of the semiconductor substrate, and forming a semiconductor device in the heteroepitaxial layer structure. A semiconductor device structure according to some embodiments includes semiconductor substrate having a patterned surface. The semiconductor substrate is formed of a material having a thermal conductivity greater than about 50 W/m-K. The device structure includes a heteroepitaxial layer structure conformally formed on the patterned surface of the semiconductor substrate, and at least one metal contact on the heteroepitaxial layer structure.