Freeze-Dried Dopant Granules for Silicon Ingot Resistivity Control
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Solution Overview
Problem
Existing methods for adding dopants to silicon melts during crystal growth face challenges in achieving precise and controlled impurity levels, leading to variability and deviations from desired resistivity specifications, particularly in large-scale single crystal silicon ingot production.
Innovation Solution
The use of freeze-dried dopants, manufactured by freezing aqueous precursor solutions into spherical granules, allows for precise control over dopant concentration and uniform distribution, reducing segregation and variability through controlled addition during Czochralski growth processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dopant addition methods are used during crystal growth, then the process is simple and fast, but the dopant concentration control precision and uniformity deteriorate due to segregation
Solution Approach 1:
The dopant is pre-loaded into a dopant delivery system (such as a dopant rod or dopant feed) before the crystal growth process begins. This preliminary preparation allows for controlled, incremental addition of dopant during growth, ensuring precise concentration control while maintaining a relatively simple overall process architecture.
Solution Approach 2:
A dopant delivery system acts as an intermediary between the dopant source and the crystal melt. This intermediary mechanism enables precise control over dopant addition rates and timing, reducing segregation effects while maintaining process simplicity through automated or semi-automated delivery.
2Productivity
If large charge sizes are used for scaling, then productivity increases, but variability and repeatability of dopant concentration worsen
Solution Approach 1:
The dopant delivery system incorporates feedback mechanisms (such as monitoring dopant consumption rates, crystal growth rates, and melt composition) that allow real-time adjustments to maintain consistent dopant concentration. This feedback control enables large-scale production while preserving repeatability and reducing variability through continuous optimization.
Solution Approach 2:
The dopant delivery system is designed to be dynamic and adaptable, allowing adjustment of dopant addition rates based on real-time process conditions. This dynamic control enables the system to maintain precise dopant concentration control even as production scale increases, ensuring reliability across different charge sizes.
3Manufacturing precision
If dopant is added to achieve target resistivity, then electrical properties improve, but segregation causes resistivity to decrease along crystal length
Solution Approach 1:
The dopant is pre-loaded into a dopant delivery system before crystal growth begins, enabling controlled, incremental addition throughout the growth process. This preliminary preparation allows for maintaining consistent dopant concentration in the melt, counteracting segregation effects and achieving uniform resistivity along the crystal length while meeting target specifications.
Solution Approach 2:
The dopant delivery system serves as an intermediary that mediates between the dopant source and the crystal melt, providing controlled addition that compensates for segregation. This intermediary mechanism maintains stable dopant concentration in the melt, ensuring uniform resistivity distribution along the crystal while achieving target electrical properties.
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 enhances the ability to meet tight resistivity requirements by minimizing dopant segregation and ensuring consistent dopant concentration, improving the reproducibility and efficiency of single crystal silicon ingot production.
Implementation Method 1
freezing each of the one or more liquid droplets of the aqueous precursor mixture to form one or more solidified droplets
Implementation Method 2
removing water from each of the one or more solidified droplets by sublimation to form one or more freeze dried dopant granules
Data Source
AI summary
Methods for growing a single crystal ingot using a freeze dried dopant include adding semiconductor material to a crucible of an ingot puller, heating the semiconductor material to form a melt, adding a freeze dried dopant to the melt, and pulling a single crystal ingot from the melt. A doping concentration of the single crystal ingot is controlled using the freeze dried dopant.