GaN Substrate Structure for Scalable Semiconductor Fabrication
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Solution Overview
Problem
Fabricating large-area GaN bulk wafers is challenging and expensive, limiting the scalability and cost-effectiveness of GaN-based semiconductor devices.
Innovation Solution
A substrate structure comprising a non-GaN-based substrate with sequentially stacked GaN-based material layers, including a buffer layer, a densely-doped n-type contact layer, a lightly-doped p-type channel layer, and a lightly-doped n-type drift layer, allowing for the fabrication of GaN-based semiconductor devices on larger, less expensive substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a GaN bulk wafer is used to fabricate vertical type devices, then excellent material properties (high breakdown electric field, high electron saturation speed, high thermal conductivity) are achieved, but the fabrication cost increases and large area wafers become difficult to manufacture
Solution Approach 1:
The invention segments the GaN-based semiconductor structure into multiple functional layers (buffer layer, first conductive type layer, second conductive type layer, third conductive type layer) grown on a non-GaN substrate. This segmentation allows each layer to be optimized for specific functions while using cost-effective non-GaN substrates, resolving the contradiction between achieving excellent material properties and reducing fabrication costs.
Solution Approach 2:
The invention introduces a buffer layer as an intermediary between the non-GaN substrate and the GaN-based active layers. This buffer layer mediates the lattice mismatch and thermal expansion differences, enabling the growth of high-quality GaN layers on inexpensive non-GaN substrates like silicon or sapphire, thus reducing fabrication costs while maintaining device reliability.
2Reliability
If a GaN bulk wafer is used to fabricate vertical type devices, then excellent material properties are achieved, but large area wafers become difficult to manufacture
Solution Approach 1:
The invention segments the semiconductor structure into thin functional layers grown epitaxially on a large-area non-GaN substrate. This approach enables the manufacturing of large-area wafers (e.g., 6-inch or 8-inch silicon substrates) that would be difficult to obtain as GaN bulk wafers, while maintaining excellent thermal conductivity through the GaN-based active layers.
Solution Approach 2:
The invention changes the substrate material parameter from GaN bulk to non-GaN materials (silicon, sapphire, SiC), enabling significant increases in wafer area and diameter. This parameter change allows large-area device fabrication while the GaN-based functional layers preserve the necessary thermal and electrical properties.
Data Source
AI summary
According to example embodiments, a substrate structure may include a GaN-based third material layer, a GaN-based second material layer, a GaN-based first material layer, and a buffer layer on a non-GaN-based substrate. The GaN-based first material layer may be doped with a first conductive type impurity. The GaN-based second material layer may be doped with a second conductive type impurity at a density that is less than a density of the first conductive type impurity in the first GaN-based material layer. The GaN-based third material layer may be doped with a first conductive type impurity at a density that is less than the density of the first conductive type impurity of the GaN-based first material layer. After a second substrate is attached onto the substrate structure, the non-GaN-based substrate may be removed and a GaN-based vertical type semiconductor device may be fabricated on the second substrate.