Multi-Batch Dopant Feeder for Silicon Ingot Resistivity Control
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Solution Overview
Problem
Existing ingot puller apparatuses struggle to maintain the resistivity of silicon wafers within a narrow range during the Czochralski process due to the decrease in net dopant concentration as the silicon solidifies, necessitating improved methods for adding multiple dopant batches during ingot growth.
Innovation Solution
An ingot puller apparatus with a dopant feeder system that includes multiple receptacles and a rotation mechanism to sequentially add dopant batches to the silicon melt, ensuring precise control over resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single dopant batch is added to the silicon melt, then the initial resistivity can be set, but the resistivity falls out of specification as solidification progresses due to decreasing dopant concentration
Solution Approach 1:
The dopant addition system is segmented into multiple separate dopant feeders (at least two), each capable of independently adding dopant batches to the silicon melt at different stages of crystal growth. This segmentation allows the total dopant dosage to be divided into multiple controlled additions, maintaining dopant concentration within specification throughout the solidification process.
Solution Approach 2:
The system performs preliminary action by pre-planning and preparing multiple dopant batches before crystal growth begins. The dopant feeders are pre-configured with specific dopant quantities and timing schedules, enabling proactive compensation for the expected decrease in dopant concentration as solidification progresses, rather than reacting to resistivity deviations after they occur.
2Manufacturing precision
If multiple dopant batches are added during ingot growth, then resistivity can be maintained within target range, but the device complexity increases with multiple receptacles and rotation mechanisms
Solution Approach 1:
Multiple dopant feeders are designed with universal, identical structures, each comprising a receptacle, rotation mechanism, and delivery system. This multi-functionality approach allows the same standardized component design to be replicated multiple times, reducing overall system complexity through standardization while still enabling multiple dopant additions. Each feeder unit can independently perform the complete function of dopant storage, delivery, and addition.
Solution Approach 2:
The system merges the functionality of multiple dopant addition operations into a coordinated system where dopant feeders operate in sequence during crystal growth. The rotation mechanisms of different feeders are synchronized, and dopant additions are timed to coincide with specific stages of ingot solidification, combining multiple complex operations into an integrated process that maintains simplicity through coordination.
3Reliability
If dopant concentration is increased to maintain resistivity, then resistivity specification is maintained, but the net dopant concentration decreases as silicon solidifies causing yield loss
Solution Approach 1:
The system ensures continuity of useful action by continuously monitoring crystal growth progress and continuously adding dopant in controlled batches throughout the solidification process. Rather than adding all dopant at the beginning and dealing with concentration depletion, or stopping growth to add dopant, the system maintains continuous crystal growth with continuous dopant supplementation, ensuring uninterrupted production and maximum prime yield while maintaining resistivity specifications.
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 apparatus effectively maintains resistivity within target ranges, enhancing prime yield and throughput by allowing counter-doping processes to achieve tight resistivity tolerances.
Implementation Method 1
a rotation mechanism for rotating the first dopant receptacle to release the first batch of dopant into the crucible and for rotating the second dopant receptacle to release the second batch of dopant into the crucible
Implementation Method 2
A tube is disposed below the dopant feeder for transporting the first and second batches of dopant to the crucible
Implementation Method 3
The polycrystalline silicon is heated to cause a silicon melt to form in the crucible
Implementation Method 4
As liquid silicon continues to solidify in the single-crystal silicon ingot
Data Source
AI summary
Ingot puller apparatus for producing a doped single crystal silicon ingot are disclosed. The ingot puller apparatus includes a dopant feeder having a first dopant receptacle for holding a first batch of dopant and a second dopant receptacle for holding a second batch of dopant. A rotation mechanism rotates the first dopant receptacle to release the first batch of dopant into the crucible and rotates the second dopant receptacle to release the second batch of dopant into the crucible.