Local Seed Crystal Temperature Control for High-Quality Crystal Growth
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Solution Overview
Problem
Conventional crystal growth methods, such as the Vertical Bridgman Method, face challenges in accurately controlling the temperature gradient near the seed crystal, leading to issues like polycrystallization, thermal stress, and reduced crystallinity due to steep temperature gradients, which hinder the growth of high-quality crystals.
Innovation Solution
An apparatus with a temperature controlling means, including a hollow cap or helical pipe outside the crucible, allows for local cooling or heating of the seed crystal, enabling precise regulation of the axial temperature distribution to achieve optimal temperature conditions for crystal growth, using refrigerant flow and micro heaters to achieve steep temperature gradients without damaging the seed crystal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a steep temperature gradient is applied in the vicinity of the seed crystal to control the solid-liquid interface position, then the position control is improved, but thermal stress distorts the crystal lattice and increases defects
Solution Approach 1:
The temperature control system is segmented into multiple independent heating zones along the axial direction. Each zone can be controlled separately to create different temperature gradients in different regions, allowing steep gradients near the interface while maintaining gentler gradients elsewhere to reduce thermal stress
Solution Approach 2:
Different temperature gradient conditions are applied to different spatial locations: a steep temperature gradient is applied locally at the solid-liquid interface to control position, while gentler gradients are maintained in other regions to minimize thermal stress and crystal defects
2Reliability
If the temperature gradient is reduced to minimize thermal stress, then crystal quality is improved, but the solid-liquid interface position cannot be controlled accurately
Solution Approach 1:
The heating system is divided into multiple independently controllable zones, enabling the application of different temperature gradients in different axial regions simultaneously
Solution Approach 2:
A steep temperature gradient is applied locally at the solid-liquid interface region to ensure precise position control, while gentler gradients are maintained in other regions to minimize thermal stress and maintain crystal quality
3Temperature
If conventional heating elements are used to liquefy raw materials, then the raw material melting is achieved, but accurate local temperature regulation near the seed crystal cannot be performed
Solution Approach 1:
The single heating element is replaced with multiple heating zones that can be independently controlled, allowing different temperature conditions in different regions - high temperature for raw material liquefaction and precise local temperature control near the seed crystal
Solution Approach 2:
Different temperature conditions are applied to different locations: high temperature is maintained in the bulk region to keep raw materials liquefied, while precise local temperature regulation is achieved near the seed crystal to control the solid-liquid interface and minimize thermal stress
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 allows for the growth of highly-qualified crystals with improved yield by precisely controlling the temperature gradient near the seed crystal, reducing defects and polycrystallization, and enabling temperature gradients up to 600° C/cm, significantly higher than conventional methods, while maintaining seed crystal integrity.
Implementation Method 1
means for regulating refrigerant flow running through the hollow portion
Implementation Method 2
micro heaters to achieve steep temperature gradients without damaging the seed crystal
Implementation Method 3
liquefied materials in the growth chamber is solidified from a low-temperature seed crystal
Data Source
AI summary
Highly-qualified crystals are grown with good yield under an optimal temperature condition by controlling the axial temperature distribution in the vicinity of the seed crystal locally. In an apparatus for producing crystals to grow crystals wherein a seed crystal 14 is placed in a crucible 11 which is retained in a furnace, raw materials 12 filled in the crucible 11 are heated and liquefied, and a raw material 12 slowly cooled in the crucible 11 from below upward, the apparatus including a temperature controller for controlling temperature to cool or heat the vicinity of the seed crystal 14 locally. The temperature controller controls the temperature by a hollow constructed cap 17 mounted outside the portion of crucible 11 and regulates refrigerant flow running through the hollow portion.