Czochralski Single-Crystal Manufacturing with Melt Maturing
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Solution Overview
Problem
The Czochralski method for manufacturing large-diameter single crystals faces challenges with dislocation generation, leading to increased remelting ratios and reduced yield, particularly when producing crystals with nitrogen or low resistivity, due to unmelted dopant remains and surface oxide issues.
Innovation Solution
A modified Czochralski method involving a crucible with a large diameter, where the melt is matured by heating and moving the heater and crucible up and down to ensure uniform heating, preventing unmelted dopant and oxide attachment, and applying a magnetic field to suppress dislocation generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the crystal manufacture is started as soon as possible after melting, then the time required for the whole manufacture is shortened, but dislocation is easily generated in large diameter crystals
Solution Approach 1:
The patent introduces a maturing step that is performed preliminarily before the crystal growth step. This maturing step allows the melt to be prepared in advance by removing unmelted remains and dopants, thereby preventing dislocation generation during subsequent crystal growth without extending the total manufacturing time significantly.
Solution Approach 2:
The patent extracts and removes unmelted remains of crystalline raw material and dopants from the melt through the maturing step. This extraction of harmful elements prevents dislocation generation during crystal growth, resolving the contradiction between quick manufacturing and high reliability.
2Reliability
If a maturing step is added to prevent unmelted remains, then dislocation generation is reduced, but the manufacturing process becomes more complex and time-consuming
Solution Approach 1:
The patent merges the maturing step with the existing melting and temperature decrease steps. The maturing is performed during the temperature control phase after melting, combining multiple functions into a single integrated process rather than adding a completely separate complex step.
Solution Approach 2:
The maturing step utilizes the existing heater and crucible system to perform self-purification of the melt. The process automatically removes unmelted remains and dopants through controlled heating and convection without requiring additional complex equipment or manual intervention.
3Device complexity
If the heater and crucible are kept stationary during maturing, then the process is simple, but uniform heating is not achieved and local quality changes occur
Solution Approach 1:
The patent introduces dynamic movement of the crucible during the maturing step. The crucible is rotated and/or moved vertically to enable uniform heating of the entire melt volume. This dynamic approach ensures homogeneous temperature distribution and prevents local quality changes while maintaining process simplicity.
Solution Approach 2:
The patent employs periodic rotation and movement of the crucible during maturing. This periodic action ensures that all parts of the melt are periodically exposed to the heater, achieving uniform heating throughout the melt volume without requiring continuous complex operation.
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 method effectively reduces dislocation generation, improves remelting and dislocation-free ratios, and enhances the yield and quality of large-diameter single crystals by ensuring thorough melting and uniform heating, even in large crucibles.
Implementation Method 1
producing a melt by heating and melting a crystalline raw material in a crucible with a heater
Implementation Method 2
applying a magnetic field to suppress dislocation generation
Data Source
AI summary
The present invention is a single-crystal manufacturing method based on the Czochralski method, comprising at least the steps of: producing a melt by heating and melting a crystalline raw material in a crucible with a heater; maturing the melt by keeping the melt at a high temperature; growing a single crystal after dipping a seed crystal into the matured melt, wherein the heater and the crucible are relatively moved up and down in the step of maturing. As a result, there is provided a single-crystal manufacturing method that enables the generation of dislocation to be effectively suppressed and a high quality single crystal to be manufactured at good yield, particularly in case of pulling the single crystal having a large diameter, in manufacture of the single crystal.