AlN Buffer Layer Growth via Halogen Gas Injection
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Solution Overview
Problem
The homogeneous formation of AlN particles in the gas phase during hydride vapor phase epitaxy (HVPE) processes leads to negative effects such as reduced deposition rate, yield, and poor thickness uniformity of AlN films, along with macro contaminants and structural defects, hindering the growth of high-quality epitaxial layers.
Innovation Solution
The method involves flowing additional hydrogen halide or halogen gas, such as Cl2, into the growth zone to suppress homogeneous particle formation during the deposition of aluminum-containing group III-nitride buffer layers, improving crystal quality and morphology by inhibiting and dissolving homogeneous species on the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If aluminum trihalide and ammonia are used for AlN deposition in HVPE process, then AlN films can be formed, but homogeneous gas-phase reactions produce AlN particles that reduce deposition rate, yield, and thickness uniformity
Solution Approach 1:
The patent introduces a carrier gas (such as hydrogen or nitrogen) as an intermediary substance to transport aluminum trihalide and ammonia separately to the reaction zone, preventing their direct homogeneous mixing in the gas phase while enabling controlled heterogeneous reaction on the substrate surface, thus improving thickness uniformity without sacrificing deposition rate
Solution Approach 2:
The patent creates different local environments within the reaction chamber: a particle-free zone over the substrate with controlled reactant delivery, and a reaction zone where heterogeneous deposition occurs. This local differentiation ensures high thickness uniformity on the substrate while maintaining high deposition rate through optimized local reactant concentration
2Reliability
If aluminum trihalide and ammonia are mixed in the gas phase, then AlN particles form rapidly, but this leads to macro contaminants and structural defects in the films
Solution Approach 1:
The patent extracts the harmful homogeneous gas-phase reaction pathway by separating reactant delivery and preventing bulk mixing, allowing only the desired heterogeneous surface reaction to occur, thereby eliminating AlN particle formation and macro contaminants while maintaining film quality
Solution Approach 2:
The patent uses an inert carrier gas atmosphere to transport reactants without allowing them to undergo unwanted homogeneous reactions in the bulk gas phase, creating a controlled environment that prevents particle formation while enabling high-quality film deposition
3Manufacturing precision
If additional hydrogen halide or halogen gas is flowed into the growth zone to suppress homogeneous particle formation, then crystal quality improves, but process complexity increases
Solution Approach 1:
The patent modifies the chemical composition parameter of the gas phase by introducing hydrogen halide or halogen gas, which changes the reaction kinetics to suppress homogeneous particle formation and promote heterogeneous surface deposition, thereby improving crystal quality with a relatively simple process modification
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 deposition rate, yield, and thickness uniformity of AlN films, achieving crystal quality comparable to or superior to the highest-quality GaN layers grown by MOCVD or HVPE, while reducing surface roughness and structural defects.
Implementation Method 1
forming group III-nitride buffer layers that contain aluminum by flowing an ammonia gas into a growth zone of the processing chamber, flowing an one or more metal halide containing precursors (wherein at least one is aluminum halide containing precursor) to the growth zone
Implementation Method 2
The additional hydrogen halide or halogen gas that is flowed into the growth zone suppresses homogeneous particle formation during deposition of buffer layers
Data Source
AI summary
Methods are disclosed for growing high crystal quality group III-nitride epitaxial layers with advanced multiple buffer layer techniques. In an embodiment, a method includes forming group III-nitride buffer layers that contain aluminum on suitable substrate in a processing chamber of a hydride vapor phase epitaxy processing system. A hydrogen halide or halogen gas is flowing into the growth zone during deposition of buffer layers to suppress homogeneous particle formation. Some combinations of low temperature buffers that contain aluminum (e.g., AlN, AlGaN) and high temperature buffers that contain aluminum (e.g., AlN, AlGaN) may be used to improve crystal quality and morphology of subsequently grown group III-nitride epitaxial layers. The buffer may be deposited on the substrate, or on the surface of another buffer. The additional buffer layers may be added as interlayers in group III-nitride layers (e.g., GaN, AlGaN, AlN).