GaN Substrate Tilt Angle for Edge Crystallinity
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Solution Overview
Problem
The existing methods for producing non-polar or semi-polar GaN substrates with larger diameters face challenges in achieving high crystallinity at the edges perpendicular to the c-axis, particularly in forming orientation flats with high accuracy, due to low crystal quality at the edges.
Innovation Solution
The development of GaN substrates with specific tilt angles and configurations, including a disk-shaped design with a tilt angle of 45° to 135° relative to the (0001) plane, featuring a single diffraction peak in X-ray diffraction patterns and controlled alkali metal and halogen concentrations, to ensure high crystallinity across the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a bulk GaN crystal is grown on a C-plane GaN template by HVPE method to produce non-polar or semi-polar GaN substrates, then the substrate can be obtained with millimeter-thick crystal, but the substrate size is limited to elongated shape with diameter in the order of millimeters and cannot provide large-area substrate like 2-inch substrate
Solution Approach 1:
The invention uses a C-plane GaN template as a seed to grow a bulk GaN crystal, which is then sliced into multiple non-polar or semi-polar GaN substrates. This segmentation approach allows production of large-area substrates while maintaining crystal quality through the template-guided growth process
Solution Approach 2:
The invention transitions from growing crystals in the c-axis direction (vertical dimension) to producing substrates with large lateral dimensions (horizontal dimension). By slicing the bulk crystal at specific angles to obtain non-polar or semi-polar planes, large-area substrates can be produced while maintaining the benefits of template-guided crystal growth
2Measurement precision
If the edge portion of a GaN substrate in a direction perpendicular to the c-axis has low crystal quality, then it is difficult to form an orientation flat with high accuracy, but the edge portion is necessary for substrate processing and device fabrication
Solution Approach 1:
The invention performs preliminary crystal growth on a C-plane GaN template before slicing into final substrates. This preliminary action ensures that the bulk crystal has high and uniform quality throughout, including the edge portions, enabling subsequent precise orientation flat formation
Solution Approach 2:
The invention changes the crystal orientation parameters by slicing the bulk GaN crystal at specific angles to produce non-polar or semi-polar planes. This parameter change allows the edge portions to maintain high crystal quality while providing the necessary geometric features for processing
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 enables the production of non-polar or semi-polar GaN substrates with diameters of 2 inches or more, maintaining high crystallinity at the edges and facilitating the production of nitride semiconductor devices with improved yield and reliability.
Implementation Method 1
a single diffraction peak appears in an X-ray diffraction pattern obtained by θ scan in which an X-ray (CuKα1: wavelength: 0.1542 nm) is incident to the first point and the incident angle θ of the incident X-ray is varied while the 2θ angle of the diffracted X-ray is fixed to twice the Bragg angle of 28.99° of the {11-20} plane
Implementation Method 2
the 2θ angle of the diffracted X-ray is fixed to twice the Bragg angle of 28.99° of the {11-20} plane
Data Source
AI summary
A disk-shaped GaN substrate has a diameter of 2 inches or more has a front surface tilted with a tilt angle of 45° or more and 135° or less relative to the (0001) plane in a tilt direction within a range of ±5° around the <10-10> direction, and a back surface which is a main surface opposite to the front surface. The GaN substrate has a first point positioned in a direction perpendicular to the c-axis when viewed from the center thereof, on the side surface thereof. A single diffraction peak appears in an X-ray diffraction pattern obtained by θ scan in which an X-ray (CuKα1: wavelength: 0.1542 nm) is incident to the first point and the incident angle θ of the incident X-ray is varied while the 2θ angle of the diffracted X-ray is fixed to twice the Bragg angle of 28.99° of the {11-20} plane.