Heat Shield Void Design for Silicon Ingot Defect Reduction
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Solution Overview
Problem
Ingot puller apparatuses using heat shields with insulation throughout result in defects such as large in-grown voids and oxygen precipitates in single crystal silicon ingots, leading to gate-oxide-integrity failures, particularly in Perfect Silicon wafer products used for advanced memory devices.
Innovation Solution
The ingot puller apparatus features a heat shield with a void within its leg segment, allowing for enhanced heat extraction and reduced thermal conduction, which minimizes defects by maintaining a uniform temperature gradient and reducing particle contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If heat shield includes insulation throughout to maintain temperature, then temperature maintenance is improved, but defect formation (voids and oxygen precipitates) increases
Solution Approach 1:
The heat shield transitions from uniform insulation to a differentiated structure with insulated outer surfaces and a void (uninsulated region) at the center. This local quality change allows different zones to serve different functions: the insulated outer surfaces maintain overall thermal stability while the central void enables enhanced heat extraction at the critical melt interface, preventing defect formation without sacrificing temperature maintenance.
Solution Approach 2:
The heat shield is segmented into distinct functional zones: an insulated outer shell and a central void region. This segmentation allows the structure to simultaneously perform thermal insulation and localized heat extraction, resolving the contradiction between maintaining temperature and preventing defects by separating these functions into different spatial zones.
2Object-affected harmful factors
If heat extraction is enhanced to reduce defects, then defect reduction is improved, but temperature uniformity deteriorates
Solution Approach 1:
The central void creates a localized region of enhanced heat extraction precisely where needed at the melt interface, while the insulated outer surfaces maintain overall temperature uniformity. This local quality differentiation allows selective heat management that reduces defects without compromising global thermal stability.
Solution Approach 2:
The central void acts as an intermediary thermal pathway that facilitates heat extraction from the melt to the heat shield without directly compromising the thermal insulation provided by the outer shell. This intermediary structure enables controlled heat transfer that prevents defect formation while maintaining temperature uniformity in the bulk crystal.
3Object-affected harmful factors
If foot extends radially inward to reduce particle contamination, then cleanliness is improved, but heat conduction increases
Solution Approach 1:
The foot structure extends radially inward to sweep the melt interface and reduce particle contamination, while the central void ensures that this extended structure does not create a continuous thermal conduction path. The local quality of the foot (extending inward for cleanliness) is decoupled from thermal conduction by the intervening void space.
Solution Approach 2:
The void is extracted from the heat shield structure at the critical location where the foot extends inward. This extraction of insulating material creates a thermal break that prevents the foot from becoming a heat conduction bridge, allowing the foot to perform its particle removal function without excessive heat loss.
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 design achieves a 10%-35% improvement in the Perfect Silicon window and a 10% lower pull rate, reducing defects and enhancing the quality of wafers by maintaining a uniform temperature gradient and minimizing heat loss.
Implementation Method 1
The heat shield has a void (e.g., an area without insulation) disposed within the heat shield
Data Source
AI summary
Ingot puller apparatus for preparing a single crystal silicon ingot by the Czochralski method are disclosed. The ingot puller apparatus includes a heat shield. The heat shield has a leg segment that includes a void (i.e., an open space without insulation) disposed in the leg segment. The heat shield may also include insulation partially within the heat shield.