Floating Zone Single Crystal Reflector and Edge Heating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The floating zone method for producing single crystals faces challenges in managing thermal stress and crystallization boundary bending, particularly as the crystal diameter and crystallization rate increase, which can lead to dislocation formation and reduced productivity.
Innovation Solution
A method and apparatus that utilize a reflector to impede crystallization heat emission and a heating device to heat the single crystal's outer edge, controlling the distance between the crystallization boundary's center and edge to mitigate thermal stress and bending, while maintaining a stable crystallization rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the diameter of the single crystal and the rate of crystallization are increased to improve productivity, then the output increases, but the bending of the crystallization boundary increases and thermal stress aggravates leading to dislocation formation
Solution Approach 1:
The patent applies local quality by implementing a reflector specifically at the outer edge region of the crystallization boundary where thermal stress is highest. This localized intervention targets the specific area where bending occurs most severely, rather than uniformly treating the entire crystal surface. The reflector is positioned to selectively influence heat transfer only in the critical outer region, maintaining crystal quality without restricting overall crystallization rate.
Solution Approach 2:
The patent converts the harmful thermal radiation that causes boundary bending into a beneficial effect by using a reflector to redirect this radiation back onto the crystal. The thermal stress and heat transfer that originally caused bending are now harnessed to maintain a more uniform temperature distribution and reduce boundary curvature, transforming the problematic thermal effects into a stabilizing mechanism.
2Reliability
If a reflector surrounding the single crystal is used to reduce thermal stress, then thermal stress is reduced, but heat transfer via the lateral surface is impeded requiring more heat supply
Solution Approach 1:
The reflector is positioned specifically at the outer edge region rather than surrounding the entire crystal. This localized placement reduces thermal stress where it is most critical (at the boundary) while minimizing the impact on overall heat transfer. The reflector's strategic positioning allows it to address the specific problem area without creating excessive thermal insulation that would require significant additional heating energy.
3Productivity
If the crystallization boundary is allowed to bend naturally with increased crystallization rate, then productivity is maintained, but thermal stress increases and dislocations form reducing crystal quality
Solution Approach 1:
The reflector converts the thermal radiation that naturally causes boundary bending into a beneficial stabilizing force. By redirecting the thermal radiation back onto the crystal at the outer edge, the system uses the same thermal energy that would cause bending to instead create a more uniform temperature distribution, reducing boundary curvature and preventing dislocation formation while maintaining high crystallization rates.
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 effectively reduces thermal stress and bending of the crystallization boundary, preventing dislocation formation and ensuring productivity by maintaining a uniform temperature distribution and controlled heat transfer, even as crystal diameter increases.
Implementation Method 1
the emission of crystallization heat is impeded by a reflector surrounding the single crystal
Implementation Method 2
the polycrystalline silicon is inductively melted and crystallized on a monocrystalline seed crystal. The polycrystalline silicon is usually provided in the form of a feed rod, which, starting from its lower end, is gradually melted by means of an induction heating coil
Implementation Method 3
the single crystal is heated in the region of an outer edge of the crystallization boundary by means of a heating device in a first zone
Data Source
AI summary
Single crystals are produced by means of the floating zone method, wherein the single crystal crystallizes below a melt zone at a crystallization boundary, and the emission of crystallization heat is impeded by a reflector surrounding the single crystal, wherein the single crystal is heated in the region of an outer edge of the crystallization boundary by means of a heating device in a first zone, wherein a distance Δ between an outer triple point Ta at the outer edge of the crystallization boundary and a center Z of the crystallization boundary is influenced. An apparatus for producing the single crystal provides a heat source below the melting induction coil and above the reflector.