N-type Conductive AlN Crystal Growth via HVPE Preheating
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Solution Overview
Problem
The existing methods for manufacturing n-type conductive aluminum nitride semiconductor crystals using the HVPE method face challenges such as low crystal growth rate, high halogen impurity content, and deteriorated homogeneity, which affect the quality and durability of the semiconductor devices.
Innovation Solution
A method involving the formation of an aluminum nitride crystal layer followed by a n-type conductive semiconductor crystal layer doped with Si atoms, where the substrate is preheated to 1,200°C or more, resulting in a crystal with reduced halogen impurities and improved crystallinity, characterized by a columnar crystalline form and specific Si concentration, and an absorption coefficient suitable for ultraviolet light transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the HVPE method is used to form n-type conductive aluminum nitride semiconductor crystal layer, then the deposition rate is high, but the homogeneity of the crystal is markedly deteriorated and halogen impurities are contained
Solution Approach 1:
The patent changes the substrate temperature parameter to 1200°C or more, which is higher than conventional HVPE processing temperatures. This parameter change transforms the reaction kinetics to reduce halogen impurity incorporation while maintaining high deposition rates, and improves crystal homogeneity by enhancing atomic mobility and reducing defect formation during growth
2Productivity
If the HVPE method is used to form n-type conductive aluminum nitride semiconductor crystal layer, then the deposition rate is high, but the crystal growth rate is low
Solution Approach 1:
By increasing the substrate temperature to 1200°C or more, the patent accelerates the crystal growth rate while maintaining high deposition rates. The elevated temperature enhances the surface reaction kinetics and adatom mobility, enabling faster crystal lattice formation without sacrificing the high material deposition capability of HVPE
3Reliability
If the n-type conductive aluminum nitride semiconductor crystal layer is formed on AlN-selfsupporting substrate, then the substrate is insulating, but the current pass becomes laterally elongated and heat is generated
Solution Approach 1:
The patent extracts and removes the insulating AlN-selfsupporting substrate after forming the n-type conductive crystal layer on it. This extraction eliminates the electrical resistance problem caused by the insulating substrate, allowing current to flow vertically through the conductive crystal layer without lateral elongation and associated heat generation
4Manufacturing precision
If the substrate temperature is increased to 1,200°C or more, then the halogen impurity content is reduced and crystallinity is improved, but the energy consumption increases
Solution Approach 1:
The patent optimizes the substrate temperature parameter to 1200°C or more, which provides the necessary thermal energy to reduce halogen impurity incorporation and improve crystallinity. While this increases energy consumption, the resulting high-quality crystal with reduced defects and impurities leads to better device performance and reliability, justifying the energy investment
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 approach enhances the crystal growth rate, reduces dislocation density, and improves the electrical properties of the n-type conductive aluminum nitride semiconductor crystal, ensuring high-quality semiconductor layers with minimal halogen impurities and efficient light transmission.
Implementation Method 1
wherein the substrate is preheated to 1,200°C or more
Implementation Method 2
a method involving the formation of an aluminum nitride crystal layer followed by a n-type conductive semiconductor crystal layer doped with Si atoms, where the substrate is preheated to 1,200°C or more
Implementation Method 3
n-type conductive semiconductor crystal layer doped with Si atoms
Data Source
Figure 1
AI summary
This invention provides a selfsupporting substrate which consists of a n-type conductive aluminum nitride semiconductor crystal and is useful for manufacturing the vertical conductive type AlN semiconductor device. The n-type conductive aluminum nitride semiconductor crystal, by which the selfsupporting substrate is made up, contains Si atom at a concentration of 1×1018 to 5×1020 cm-3, is substantially free from halogen atoms, and substantially does not absorb the light having the energy of not more than 5.9 eV. The selfsupporting substrate can be obtained by a method comprising the steps of forming an AlN crystal layer on a single crystal substrate such as a sapphire by the HVPE method, preheating the obtained substrate having the AlN crystal layer to a temperature of 1,200°C or more, forming a second layer consisting of the n-type conductive aluminum nitride semiconductor crystal is formed on the AlN crystal layer in high rate by the HVPE method and separating the second layer from the obtained laminate.