HEMT Buffer Superlattice Structure for Lattice Mismatch Control
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Solution Overview
Problem
High electron mobility transistors (HEMTs) face issues with lattice defects and thermal expansion coefficient mismatch, leading to reliability and performance problems due to the structural mismatch between semiconductor materials, which existing solutions like protruding epitaxial structures or insulating masks do not adequately address.
Innovation Solution
A semiconductor device with a buffer layer comprising a first superlattice layer arranged horizontally and a second superlattice layer arranged vertically, both made of alternating heteromaterials, which helps to prevent the upward transmission of lattice defects and improve compatibility between substrate and stacked layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional buffer layers are used without superlattice structures, then the fabrication process is simple, but lattice defects extend or diffuse upwardly causing poor device reliability
Solution Approach 1:
The buffer layer is segmented into multiple superlattice layers (first and second superlattice layers) with alternating heteromaterials arranged in different directions. This segmentation creates a complex multi-layer structure that effectively blocks and redirects lattice defects, preventing their upward propagation while maintaining device reliability
Solution Approach 2:
The patent introduces a dual-directional superlattice structure where the first superlattice layer has heteromaterials arranged in a first direction and the second superlattice layer has heteromaterials arranged in a second direction different from the first. This dimensional change creates a three-dimensional defect redirection network that effectively prevents lattice defects from extending upward, resolving the contradiction between reliability improvement and structural complexity
2Manufacturing precision
If heteromaterials are stacked vertically in the second superlattice layer, then lattice defect propagation is blocked, but the fabrication process becomes more complex
Solution Approach 1:
The vertical stacking of heteromaterials in the second superlattice layer segments the buffer structure into multiple alternating layers. This segmentation creates multiple interfaces that block and redirect lattice defects vertically, improving manufacturing precision in defect control while the segmented nature allows for systematic fabrication approaches
Solution Approach 2:
The second superlattice layer uses composite heteromaterials stacked vertically, combining different semiconductor materials with complementary properties. This composite structure effectively blocks lattice defect propagation through the vertical stacking of materials with different lattice constants, achieving high manufacturing precision in defect control
3Stability of the object's composition
If a dual superlattice structure is implemented, then thermal expansion coefficient compatibility is improved, but the device structure becomes more complex
Solution Approach 1:
The dual superlattice structure uses composite heteromaterials in both the first and second superlattice layers, where alternating layers of different materials provide graded thermal expansion properties. This composite approach improves thermal expansion coefficient compatibility between the substrate and upper layers while distributing the structural complexity across multiple functional layers
Solution Approach 2:
The patent changes the structural parameters of the buffer layer by implementing a dual superlattice configuration with heteromaterials arranged in different directions. This parameter change creates a structure that better matches the thermal expansion characteristics of the substrate and active layers, improving compositional stability while the systematic parameter changes allow for controlled fabrication
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 configuration significantly reduces lattice defects, enhancing the reliability and performance of HEMTs by laterally diverting defects and improving the lattice and thermal expansion coefficient compatibility, thus preventing dislocation, fracture, and peeling issues.
Implementation Method 1
to prevent lattice defects from extending or diffusing upwardly. Thus, the semiconductor device of the present disclosure may significantly improve the defects of gallium nitride based material layers caused by lattice mismatch
Implementation Method 2
improve the defects of gallium nitride based material layers caused by lattice mismatch and/or thermal expansion coefficient mismatch
Data Source
AI summary
The present disclosure provides a semiconductor device and a fabricating method thereof, the semiconductor device including a substrate, a nucleation layer, a buffer layer, an active layer and a gate electrode. The nucleation layer is disposed on the substrate, and the buffer layer is disposed on the nucleation layer, wherein the buffer layer includes a first superlattice layer having at least two heteromaterials alternately arranged in a horizontal direction, and a second superlattice layer having at least two heteromaterials vertically stacked along a vertical direction. The at least two heteromaterials stack at least once within the second superlattice layer. The active layer is disposed on the buffer layer, and the gate electrode is disposed on the active layer.