Nitride Semiconductor Substrate With SiC Carbonized Diffusion Barrier
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Solution Overview
Problem
The production of high-quality nitride semiconductor substrates is challenging due to difficulties in growing large-diameter substrates with high resistivity and thermal conductivity, leading to degradation of device characteristics in high-frequency devices.
Innovation Solution
A nitride semiconductor substrate is created with a heat-resistant support substrate, a planarization layer, a silicon single crystal layer with high carbon concentration, and a carbonized layer containing silicon carbide, which suppresses resistivity changes and enhances crystallinity, while being cost-effective and easy to manufacture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a high resistance silicon substrate is used to obtain low-cost nitride semiconductor epitaxial substrate with large diameter, then manufacturing cost is reduced and substrate diameter is increased, but thermal conductivity is insufficient and device reliability degrades due to heat generation
Solution Approach 1:
The patent employs a composite substrate structure consisting of a silicon substrate with a transferred silicon-germanium alloy layer. This composite structure combines the cost-effectiveness and large diameter availability of silicon substrates with the improved thermal conductivity and lattice matching properties of silicon-germanium alloy, thereby resolving the contradiction between manufacturing cost and device reliability.
Solution Approach 2:
The patent modifies the substrate properties by introducing a silicon-germanium alloy layer with controlled germanium concentration (5-30%). This parameter change enhances the thermal conductivity and electrical resistivity of the substrate while maintaining cost-effectiveness, thus improving device reliability without sacrificing the economic advantages of silicon-based substrates.
2Ease of manufacture
If a nitride semiconductor is grown by epitaxial growth on a composite substrate with transferred Si thin film, then substrate cost is reduced, but resistivity changes during growth due to heat treatments or impurity mixing, degrading device characteristics
Solution Approach 1:
The patent introduces a silicon-germanium alloy layer as an intermediary between the silicon substrate and the nitride semiconductor layer. This intermediate layer acts as a buffer that prevents impurity diffusion and resistivity changes during epitaxial growth, while still allowing the use of cost-effective silicon substrates. The alloy layer stabilizes the interface and maintains resistivity control throughout the growth process.
Solution Approach 2:
The patent uses a composite structure of silicon substrate plus silicon-germanium alloy layer to achieve both cost reduction and resistivity stability. The composite material properties combine the advantages of silicon (cost, availability) with silicon-germanium (resistivity stability, lattice matching), resolving the contradiction between substrate cost and manufacturing precision.
3Manufacturing precision
If the thickness of carbonized layer is increased to improve crystallinity, then nitride semiconductor layer quality improves, but surface roughness and substrate warp increase, reducing device yield
Solution Approach 1:
The patent optimizes the carbonized layer thickness to a specific range (4-2000 nm) to achieve the desired balance. Within this parameter range, the layer provides sufficient crystallinity improvement for the nitride semiconductor layer while keeping surface roughness and substrate warp within acceptable limits, thus resolving the contradiction between manufacturing precision and shape control.
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 substrate achieves high-quality nitride semiconductor layers with suppressed surface roughness and warp, maintaining device characteristics and reducing production costs.
Implementation Method 1
a carbonized layer containing silicon carbide as a main component and having a thickness of 4 to 2000 nm provided on the silicon single crystal layer... it is possible to suppress the degradation of device characteristics due to changes in resistivity caused by impurities diffusing from the nitride semiconductor layer (epitaxial layer) to the silicon single crystal layer during the growth of the nitride semiconductor layer on the carbonized layer
Implementation Method 2
a nitride semiconductor layer provided on the carbonized layer... during the growth of the nitride semiconductor layer on the carbonized layer
Data Source
AI summary
A nitride semiconductor substrate includes: a heat-resistant support substrate having a core including nitride ceramic enclosed in an encapsulating layer; a planarization layer provided on the heat-resistant support substrate; a silicon single crystal layer having a carbon concentration of 1×1017 atoms/cm3 or higher provided on the planarization layer; a carbonized layer containing silicon carbide as a main component and having a thickness of 4 to 2000 nm provided on the silicon single crystal layer; and a nitride semiconductor layer provided on the carbonized layer. This provides a high-quality nitride semiconductor substrate (a nitride semiconductor substrate particularly suitable for GaN-based high mobility transistors (HEMT) for high-frequency switches, power amplifiers, and power switching devices); and a method for producing the same.