Group III-Nitride Crystal Dislocation Reduction via Two-Stage Growth
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Solution Overview
Problem
Conventional methods for manufacturing group III-nitride crystals, such as GaN or AlN, result in high dislocation densities when used as substrates for semiconductor devices, leading to reduced device performance and lifespan due to penetrating dislocations.
Innovation Solution
A method involving the growth of a first group III-nitride crystal with a higher crystal growth rate parallel to the seed crystal's surface, followed by a second crystal growth with a lower rate vertical to the surface, significantly reducing dislocation density by controlling the propagation direction of dislocations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional vertical growth method is used, then crystal growth is simple, but dislocation density is high
Solution Approach 1:
The crystal growth process is divided into two distinct stages: first growing a crystal with lateral growth rate greater than vertical growth rate to reduce dislocations, then growing a crystal with vertical growth rate greater than lateral growth rate to achieve desired thickness. This segmentation allows each stage to optimize for its specific purpose, resolving the contradiction between low dislocation density and simple growth process.
Solution Approach 2:
The invention dynamically adjusts growth conditions between two stages: initially creating conditions where lateral growth exceeds vertical growth to suppress dislocation propagation, then switching to conditions where vertical growth exceeds lateral growth to achieve the required crystal thickness. This dynamic adjustment resolves the contradiction by adapting growth parameters to different process requirements.
2Manufacturing precision
If ELO method is used to reduce dislocations, then dislocation density decreases, but manufacturing cost increases
Solution Approach 1:
The invention extracts and eliminates the need for complex mask formation, photolithography, and etching steps required by ELO methods. Instead, it uses controlled differential growth rates in two stages to achieve dislocation reduction, thereby maintaining low dislocation density while significantly simplifying the manufacturing process and reducing costs.
Solution Approach 2:
The invention replaces expensive and complex ELO processing steps with a simpler, more cost-effective two-stage growth approach. The first stage uses temporary lateral growth preference to reduce dislocations, then the second stage restores normal vertical growth, achieving the same dislocation reduction effect as ELO but with much lower manufacturing complexity and cost.
3Manufacturing precision
If lateral growth rate is increased to reduce dislocations, then dislocation density decreases, but crystal thickness increases
Solution Approach 1:
The invention segments the growth process into two distinct phases: the first phase uses lateral growth rate greater than vertical growth rate to reduce dislocation density, while the second phase uses vertical growth rate greater than lateral growth rate to achieve the desired crystal thickness. This segmentation resolves the contradiction by dedicating each phase to a specific objective.
Solution Approach 2:
The invention employs periodic alternation between two growth modes: initially favoring lateral growth to suppress dislocations, then switching to favoring vertical growth to achieve required thickness. This periodic switching of growth preferences allows the crystal to simultaneously achieve low dislocation density and appropriate thickness 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
This approach effectively reduces dislocation density to at most 5×10^6/cm², enhancing the performance and longevity of semiconductor devices by minimizing dislocation-related issues.
Implementation Method 1
growing a first group III-nitride crystal on the seed crystal by liquid phase method; wherein in the step of growing a first group III-nitride crystal on the seed crystal, rate of crystal growth in a direction parallel to a main surface of the seed crystal is higher than rate of crystal growth in a direction vertical to the main surface of the seed crystal
Implementation Method 2
growing a second group III-nitride crystal on the first group III-nitride crystal; wherein in the step of growing a second group III-nitride crystal on the first group III-nitride crystal, rate of crystal growth in a direction parallel to a main surface of the seed crystal is lower than rate of crystal growth in a direction vertical to the main surface of the seed crystal
Data Source
AI summary
A method of manufacturing a group III-nitride crystal substrate including the steps of introducing an alkali-metal-element-containing substance, a group III-element-containing substance and a nitrogen-element-containing substance into a reactor, forming a melt containing at least the alkali metal element, the group III-element and the nitrogen element in the reactor, and growing group III-nitride crystal from the melt, and characterized by handling the alkali-metal-element-containing substance in a drying container in which moisture concentration is controlled to at most 1.0 ppm at least in the step of introducing the alkali-metal-element-containing substance into the reactor is provided. A group III-nitride crystal substrate attaining a small absorption coefficient and the method of manufacturing the same, as well as a group III-nitride semiconductor device can thus be provided.