Multi-zone Variable Power Density Heater for VGF Crystal Growth
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Solution Overview
Problem
Current vertical gradient freeze (VGF) crystal growth processes face issues with thermal stresses due to radial temperature gradients, leading to crystal distortion and lower quality yields, as existing heater systems fail to precisely control temperature profiles.
Innovation Solution
A heater design featuring multiple zones with varying power density gradients, allowing for controlled temperature and heat flux profiles in both vertical and radial directions, achieved by adjusting power input to electrode paths with changing widths along the heater length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If multi-zone external graphite heaters or changing the relative position of the crucible and heater are used to achieve the temperature gradient profile, then the vertical temperature gradient is improved, but radial temperature gradient and thermal stresses increase
Solution Approach 1:
The heater winding is designed with non-uniform turn spacing where the spacing between adjacent turns varies along the length of the heater. Specifically, the turn spacing is tighter at the ends and more spaced out in the middle section, creating zones with different power density characteristics. This local variation in heating intensity allows precise control of the temperature profile while minimizing radial temperature gradients that cause thermal stresses.
Solution Approach 2:
The system enables dynamic adjustment of heating parameters during the crystal growth process. The power density distribution can be modified by changing the current through different sections of the heater winding, allowing the temperature profile to be optimized at different stages of crystal growth and to compensate for thermal stresses in real-time.
2Ease of manufacture
If uniform heater design is used, then manufacturing simplicity is maintained, but temperature profile control precision deteriorates
Solution Approach 1:
The heater is segmented into distinct zones along its length, with each zone having a specific turn spacing pattern. This segmentation allows independent optimization of temperature control in different regions (hot zone, transition zone, cold zone) while maintaining a relatively simple overall heater structure that can be manufactured using standard techniques.
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 precise control of the temperature gradient, reducing thermal stresses and improving crystal quality by allowing for tailored heat distribution during the VGF process.
Implementation Method 1
a heater comprising a plurality of zones each defined by an electrode path disposed through a length of the heater and having a width that varies along the length of the heater, at least two zones having a variable power density gradient through the length of each zone
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 1E~1F
AI summary
A heater comprises a plurality of zones with at least two zones having a variable power density gradient different from one another. The heater having zones of different variable power density gradients allows for controlling the heat output and temperature profile of the heater in one or more directions of the heater. The heater can be used, for example, to control the temperature profile in a vertical direction.