ScAlMgO4 Substrate Crystal Orientation Collapse Prevention
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Solution Overview
Problem
The Czochralski method for producing ScAlMgO4 single crystal substrates often results in crystal orientation collapse at the center due to a high temperature gradient, leading to poor quality substrates with broad full width at half maximum in rocking curve analysis.
Innovation Solution
Setting specific conditions for crystal diameter and growth rate, where the product of the crystal growth rate and the one-third power of the crystal diameter is between 2.6 and 3.0, to minimize crystal orientation collapse and achieve high-quality ScAlMgO4 single crystal substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the temperature gradient at the interface between the atmosphere and melt is increased to prevent seed crystal melting, then the seed crystal is protected from melting, but the center of the melt is easily cooled and crystal orientation collapses at the center of the pulled single crystal
Solution Approach 1:
The invention changes the physical parameters of the system by introducing a gas flow rate parameter and a distance parameter between the gas introduction port and melt surface. By controlling the gas flow rate within 1-10 L/min and maintaining the port at a specific distance (5-50 mm) from the melt surface, the patent creates an optimized temperature field that prevents both seed crystal melting and center cooling, resolving the contradiction between protecting the seed crystal and maintaining crystal orientation.
Solution Approach 2:
The patent introduces an inert gas (such as nitrogen or argon) as an intermediary medium between the atmosphere and the melt surface. This gas layer acts as a thermal buffer that moderates the temperature gradient, preventing direct contact between the cold atmosphere and the melt while still allowing sufficient heat transfer to maintain crystal orientation. The gas flow rate and distance parameters control the thickness and dynamics of this intermediary layer.
2Temperature
If the temperature of the melt is increased to sufficiently melt the material, then the material melts adequately, but the temperature in the region close to the surface becomes too high causing crystal orientation to collapse
Solution Approach 1:
The patent applies local quality by creating different thermal conditions at different locations within the crucible. The gas introduction port is positioned at a specific distance from the melt surface to provide localized cooling at the surface region while maintaining higher temperatures in the bulk melt. This spatial differentiation of temperature quality allows adequate melting in the bulk while preventing surface overheating that would cause orientation collapse.
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 reduces crystal orientation collapse and results in high-quality ScAlMgO4 single crystal substrates with a narrow full width at half maximum, suitable for applications like GaN preparation.
Implementation Method 1
The Czochralski method (hereinafter, also referred to as the 'CZ method') is known as a method for producing a ScAlMgO4 single crystal. The CZ method is a method including loading a material into a crucible disposed in a chamber, melting the material and then bringing a seed crystal into contact with a melt, and pulling the seed crystal with slow rotation by use of a pulling mechanism.
Implementation Method 2
An increased temperature gradient at the interface, however, causes the center of the melt (surface) to be easily cooled and causes crystal orientation to be easily collapsed at the center of the single crystal pulled.
Data Source
AI summary
A ScAlMgO4 single crystal substrate having less collapse of crystal orientation, and a method for producing the single crystal substrate. A ScAlMgO4 single crystal substrate is provided, wherein, when a center of the substrate is designated as coordinates (0,0) and a measurement beam width is set to 1 [mm]×7 [mm] to conduct analysis according to an X-ray diffraction method at respective coordinate positions of (x−m,0) to (xm,0) at an interval of 1 [mm] in an x-axis direction and (0,y−n) to (0,yn) at an interval of 1 mm in a y-axis direction, wherein m and n are each an integer falling within the range so that the measurement beam is not stuck out from the substrate, a worst value of a full width at half maximum of a rocking curve at each of the coordinate positions is less than 20 [sec.].