Porous-Partition Dopant Conduit for Uniform Silicon Ingot Doping
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Solution Overview
Problem
Existing dopant feed systems for silicon ingot production face issues with volatile dopants vaporizing uncontrollably, leading to oxide particle formation, limited payload capacity, non-uniform dopant distribution, and inconsistent ingot quality due to solid dopant ejection and manual refilling requirements.
Innovation Solution
A dopant feed system with a porous partition member in the dopant conduit that sublimes solid dopant using inert gas, maintaining a consistent gaseous dopant concentration by continuous feeding, and ensuring uniform dopant distribution across the melt surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If volatile dopant is fed from a feed hopper located above the silicon melt level, then dopant can be introduced into the melt, but the dopant vaporizes uncontrolled into the surrounding environment resulting in oxide particle formation that can fall into the melt and become incorporated into the growing crystal
Solution Approach 1:
The harmful vaporization process is extracted and relocated from the growth chamber environment to a separate dopant feed system. The dopant is vaporized in a controlled manner within the feed system rather than in the surrounding environment, preventing oxide particle formation that would contaminate the melt and crystal.
Solution Approach 2:
An intermediary dopant feed system with a porous partition member is introduced between the dopant source and the melt. This intermediary structure controls the dopant delivery process, allowing vaporized dopant to pass through the porous partition in a controlled manner directly into the melt, preventing uncontrolled vaporization and oxide particle formation in the environment.
2Quantity of substance
If gas phase dopant is used to introduce volatile dopants into the growth chamber, then dopant can be supplied, but the system must be manually refilled each time a doping procedure is performed and cannot be refilled while in use, resulting in limited dopant payload capacity
Solution Approach 1:
The dopant delivery system transitions from a gas phase storage system with limited payload to a solid phase storage system with continuous feeding capability. By changing the physical state parameter of dopant storage from gas to solid, the system achieves significantly increased payload capacity and the ability to refill during operation without interrupting the crystal growth process.
Solution Approach 2:
Solid dopant is pre-loaded into the dopant feed system before the crystal growth process begins. The porous partition member is pre-prepared with solid dopant material, allowing the system to operate continuously throughout the growth process without interruption for refilling, thereby increasing the effective dopant payload capacity.
3Quantity of substance
If gas phase dopant system is used, then dopant can be introduced into the melt, but the system supplies dopant non-uniformly during a growth process, thereby increasing the variation in dopant concentration along a grown ingot's longitudinal axis
Solution Approach 1:
The porous partition member provides localized control of dopant delivery at different positions along the dopant feed conduit. The porous structure creates multiple localized exit points for dopant vapor, ensuring uniform distribution of dopant throughout the melt rather than concentrated delivery at a single location, thereby improving dopant concentration uniformity along the ingot's longitudinal axis.
4Temperature
If solid dopant granules are introduced into an evaporation receptacle near the melt, then dopant can be vaporized, but the solid dopant granules move vigorously and are ejected from the evaporation receptacle causing them to fall into the melt, reducing the consistency of the dopant process
Solution Approach 1:
A porous partition member is used as the evaporation surface within the dopant feed system. The porous structure provides a large surface area for dopant vaporization while physically retaining the solid dopant granules within the pores. This prevents vigorous movement and ejection of solid dopant granules into the melt, while still achieving effective vaporization for dopant delivery.
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
The system achieves stable and repeatable dopant incorporation, reducing oxide particle formation and enhancing ingot consistency by controlling dopant concentration and minimizing solid dopant ejection, allowing larger ingots to be grown with uniform resistivity profiles.
Implementation Method 1
Solid dopant supported by the partition member is heated to sublime the solid dopant
Implementation Method 2
Inert gas having sublimed dopant mixed therein is contacted with the melt to absorb dopant from the inert gas into the melt
Data Source
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AI summary
Ingot puller apparatus for preparing silicon ingots that include a dopant feed system are disclosed. The dopant feed system include a dopant conduit having a porous partition member disposed across the dopant conduit. Solid dopant falls onto the partition member where it sublimes. The sublimed dopant is carried by inert gas through the partition member to contact and dope the silicon melt.