Induction Heating Coil Radial Step for Single Crystal Uniformity
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Solution Overview
Problem
The FZ method for manufacturing silicon single crystals faces challenges in evenly heating large-diameter raw material rods, leading to variations in the melted surface height, which can cause interruptions in the manufacturing process due to uneven heating and increased dislocation generation.
Innovation Solution
An induction heating coil with a radial step formation on its upper surface, surrounding the opening, and a step non-formation area adjacent to the slit, allows for even heat distribution across the peripheral direction of the raw material rod, reducing height variations and improving heat generation uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the diameter of the raw material rod is increased to improve yield, then the productivity is improved, but the heating uniformity deteriorates leading to variation in melted surface height
Solution Approach 1:
The induction heating coil is designed with a step structure where the upper surface has a first region with a first height and a second region with a second height lower than the first height. This creates local quality differences in the coil structure to achieve uniform heating across the large-diameter raw material rod, preventing variation in melted surface height while maintaining high productivity
2Use of energy by moving object
If a halogen lamp heater is added as an auxiliary heater to improve heating efficiency, then the heating efficiency is improved, but the reliability deteriorates due to coolant boiling and coil breakage
Solution Approach 1:
The patent removes the halogen lamp heater auxiliary heating system from the induction heating apparatus. By extracting this problematic component, the reliability issue of coolant boiling and coil breakage is eliminated while maintaining heating efficiency through the optimized induction coil design with step structure
3Ease of manufacture
If the induction heating coil structure is simplified to reduce manufacturing cost, then the ease of manufacture is improved, but the heating uniformity deteriorates
Solution Approach 1:
The patent modifies the geometric parameters of the induction heating coil by introducing a step structure with different heights in different regions. This parameter change in the coil geometry enables uniform heat generation across the large-diameter raw material rod while maintaining a relatively simple overall coil structure that can be manufactured
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 design enables stable growth of single crystals by reducing heat generation variations and preventing sagging of the melted surface, thereby enhancing the dislocation-free success rate and process stability.
Implementation Method 1
a magnetic field, which is generated when a high-frequency current is made to flow in an induction heating coil, is applied to a silicon raw material to cause an eddy current to flow in the silicon raw material through electromagnetic induction
Implementation Method 2
thereby generating Joule heat due to the eddy current, and the generated Joule heat is used to heat the silicon raw material
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
Provided is an induction heating coil (20) that heats a raw material rod (2) in manufacturing a single crystal (4) by an FZ method. The induction heating coil (2) includes an annular-shaped coil conductor (21) having an opening (22) at its center; a slit (23) radially extending from the opening (22) to separate one end portion of the coil conductor (21) and the other end portion thereof from each other; and a radial step (25) formed on an upper surface (21A) of the coil conductor (25) . The upper surface (21A) of the coil conductor (21) has a step formation area (28) in which the step (25) is formed in a circular arc shape in a plan view so as to surround the opening (22) and a step non-formation area (29) having no step. The step non-formation area (29) includes a slit neighborhood (27A) adjacent to the slit (23) . The step formation area (28) is an area more distant from the slit (23) than the step non-formation area (29). The step (25) is formed near and radially inside the outer peripheral end (2e) of a straight body part of the raw material rod.