Side Feed System for Continuous Czochralski Silicon Growth
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Solution Overview
Problem
The Czochralski method for growing crystalline ingots is cost-intensive due to the need to replace crucibles after each ingot, and the continuous Czochralski growth process faces challenges in replenishing silicon feedstock while maintaining tightly controlled temperatures and a non-reactive ambient.
Innovation Solution
A Czochralski growth system with a feed port and feed chamber that allows continuous supply of feedstock to the crucible, featuring a feeder system with an isolation valve and a drop box to manage the delivery of silicon feedstock, ensuring controlled addition and minimizing contamination and splashing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If batch Czochralski method is used to grow crystalline ingots, then high-quality monocrystalline silicon can be produced, but crucibles must be replaced after each ingot which increases cost and reduces throughput
Solution Approach 1:
The patent implements continuous Czochralski growth by enabling multiple ingots to be drawn from a single crucible without replacement. The system maintains continuous operation through automated feedstock replenishment and in-situ crucible heating, eliminating the batch process interruptions that previously limited throughput while maintaining ingot quality standards
2Loss of substance
If crucible replacement is performed frequently in batch Czochralski growth, then residual silicon loss is minimized, but time for crucible replacement and reheating greatly diminishes throughput
Solution Approach 1:
The system enables continuous operation by replenishing silicon feedstock directly into the crucible during ingot drawing, eliminating the need to stop production for crucible replacement. The crucible remains in the growth chamber throughout the process, maintaining thermal conditions and avoiding reheating cycles
Solution Approach 2:
The patent extends the service life of expensive crucibles by enabling multiple ingots to be grown from each crucible before replacement is necessary. This recovers the value of the crucible investment by maximizing its utilization, reducing both material loss and replacement frequency
3Productivity
If silicon feedstock is replenished to the Czochralski crucible during continuous growth, then continuous Czochralski growth is enabled, but maintaining tightly controlled temperatures and non-reactive ambient becomes challenging
Solution Approach 1:
The patent introduces a feed chamber as an intermediary component that interfaces with the growth chamber through a feed port. This isolated feed chamber allows feedstock to be loaded and prepared without exposing the hot crucible and melt to external contamination or temperature fluctuations, maintaining the non-reactive ambient and thermal stability required for continuous growth
Solution Approach 2:
The system divides the Czochralski growth system into separate functional zones: a growth chamber containing the hot crucible and melt, and an isolated feed chamber for feedstock management. This segmentation allows independent control of each zone, enabling feedstock replenishment without disrupting the temperature control and ambient conditions in the growth chamber
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
Enables continuous Czochralski growth with improved ingot quality by maintaining a consistent melt level and reducing crucible replacement costs, enhancing throughput and reducing the time required for crucible replenishment and reheating.
Implementation Method 1
The growth system further comprises at least one isolation valve. For example, the isolation valve may be attached to the feed port in the growth chamber.
Implementation Method 2
silicon is melted in a crucible to its liquid state at a temperature of about 1420° C.
Implementation Method 3
the liquid silicon freezes on the crystalline seed with the same orientation as that of the seed. The seed is then slowly raised away from the melt to form a growing crystalline ingot
Data Source
AI summary
A Czochralski growth system is described comprising a growth chamber, a feed port, and a feed chamber comprising a container for feedstock and a feeder. The feed port is disposed in at least one side wall of the growth chamber, and the feed chamber is attached to the growth chamber at the feed port. The feeder is insertable into the growth chamber through the feed port and supplies the feedstock into the growth chamber. Preferably this system can be used for producing silicon ingots using a continuous Czochralski method.