Nitride Semiconductor Substrate Curved Interface Dislocation Filtering
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Solution Overview
Problem
Conventional methods for growing nitride semiconductor substrates face challenges in achieving low dislocation density and reducing variation in off-angle, which affects surface morphology and light emission uniformity, leading to issues in semiconductor device reliability and performance.
Innovation Solution
A method involving a base substrate with a curved (0001) plane, where a first layer with inclined interfaces is grown to reduce dislocation density and then a second layer with a mirror surface is formed, using a combination of epitaxial growth techniques to control the crystal structure and oxygen concentration, resulting in a substrate with improved crystal quality and reduced off-angle variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a crystal layer is grown on a conventional substrate using standard epitaxial methods, then the substrate can be manufactured with basic properties, but the dislocation density remains high and crystal quality is insufficient
Solution Approach 1:
The growth process is segmented into multiple distinct stages: initial layer growth on curved substrate, first layer with inclined interfaces for dislocation filtering, and second layer for final crystal perfection. Each layer serves a specific function in progressively improving crystal quality while reducing dislocation density.
Solution Approach 2:
The substrate surface is pre-curved before growth to create a specific geometric configuration that facilitates controlled dislocation propagation. The initial layer is grown with predetermined thickness and properties to prepare the foundation for subsequent layers, establishing the crystal orientation and reducing off-angle variation before the main growth phases.
2Productivity
If standard epitaxial growth is used to increase production efficiency, then manufacturing speed improves, but off-angle variation increases and surface morphology deteriorates
Solution Approach 1:
Different regions of the crystal structure are grown with different properties: the initial layer has specific thickness and curvature adaptation, the first layer develops inclined interfaces with specific orientation for dislocation management, and the second layer achieves final mirror surface quality. Each region's growth parameters are locally optimized for its specific function.
Solution Approach 2:
The growth process dynamically transitions between different growth modes and conditions. The substrate curvature is maintained at specific values (5m to 500m radius) during growth, and the growth rate, temperature, and pressure are dynamically adjusted between stages to control off-angle variation and maintain surface morphology while preserving productivity.
3Ease of manufacture
If the substrate is made flat to simplify manufacturing, then ease of manufacture improves, but dislocation density cannot be effectively reduced and crystal quality suffers
Solution Approach 1:
The substrate is intentionally given a controlled curved surface with specific radius (5m to 500m) instead of being perfectly flat. This curvature creates a geometric configuration that guides dislocation propagation paths, allowing them to be filtered and reduced in the inclined interfaces of the first layer while maintaining manufacturing feasibility through controlled substrate preparation.
4Device complexity
If a single-layer growth structure is used to reduce process complexity, then device complexity decreases, but the ability to control dislocation density and crystal quality is insufficient
Solution Approach 1:
The growth structure is divided into three functionally distinct layers: initial layer for substrate adaptation and curvature management, first layer with inclined interfaces for dislocation filtering, and second layer for final crystal perfection and mirror surface formation. This segmentation enables each layer to address specific crystal quality issues that cannot be solved with a single-layer structure.
Solution Approach 2:
The first layer with inclined interfaces acts as an intermediary between the curved substrate and the final crystal layer. It serves as a dislocation filter that captures and redirects dislocations away from the final crystal structure, while its inclined interfaces gradually transition the crystal orientation from the substrate curvature to the final flat mirror surface, mediating the stress and dislocation flow.
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 approach results in a nitride semiconductor substrate with a dislocation density less than 1×10^6 cm^-2 over 95% of the surface, 50 μm square dislocation-free regions, and a reduced variation in off-angle, enhancing the reliability and performance of semiconductor devices.
Implementation Method 1
X-ray locking curve measurement for (0002) plane diffraction, which is performed to the main surface by irradiating with (Cu) Kα1 X-rays through a two-crystal monochromator of Ge (220) plane
Implementation Method 2
observation of the main surface of the nitride semiconductor substrate in a field of view of 250 μm square using a multiphoton excitation microscope to obtain a dislocation density from a dark spot density
Implementation Method 3
a method for manufacturing a nitride semiconductor substrate, which is a method for manufacturing a nitride semiconductor substrate with a vapor deposition method
Implementation Method 4
an initial step of epitaxially growing a single crystal of a group III nitride semiconductor with the (0001) plane as a growth surface directly on the main surface of the base substrate to grow an initial layer
Data Source
AI summary
There is provided a nitride semiconductor substrate having a diameter of 2 inches or more and having a main surface whose closest low index crystal plane is a (0001) plane, wherein X-ray locking curve measurement for (0002) plane diffraction, which is performed to the main surface by irradiating with (Cu) Kα1 X-rays through a two-crystal monochromator of Ge (220) plane and a slit, reveals that full width at half maximum FWHMb is 32 arcsec or less, and FWHMa−FWHMb obtained by subtracting FWHMb from FWHMa is 30% or less of FWHMa, wherein FWHMa is full width at half maximum of the (0002) plane diffraction when a slit width in ω direction is 1 mm, and FWHMb is full width at half maximum of the (0002) plane diffraction when a slit width in ω direction is 0.1 mm.