Variable-Emissivity Cooling Jacket for Single-Crystal Ingot Defect Control
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Solution Overview
Problem
Existing ingot puller apparatus and methods are inadequate in reducing the number and size of defects, such as voids and oxygen precipitates, in single crystal silicon ingots, which can lead to gate-oxide-integrity failures in semiconductor devices.
Innovation Solution
An ingot puller apparatus with a cooling jacket featuring regions of varying emissivity and a moveable design to control cooling profiles, allowing for precise temperature gradients and cooling rates during ingot growth, thereby minimizing defect formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional cooling jackets with uniform emissivity are used, then the cooling process is simple, but the cooling profile cannot be precisely controlled to minimize defects
Solution Approach 1:
The cooling jacket incorporates surface regions with different emissivity coefficients (first region with lower emissivity, second region with higher emissivity) to create localized cooling zones. This allows precise control of the cooling profile at different locations along the ingot, enabling optimization of thermal gradients to minimize defect formation while maintaining a relatively simple overall jacket structure.
2Reliability
If cooling rate is increased to reduce defect formation, then ingot quality improves, but thermal gradients become too steep causing growth instability
Solution Approach 1:
By positioning the high-emissivity surface region at specific locations along the cooling jacket, the system creates localized enhanced cooling zones that promote rapid cooling and reduce defects without causing excessive thermal gradients throughout the entire ingot. The low-emissivity regions provide more gradual cooling to maintain growth stability.
Solution Approach 2:
The system dynamically adjusts the cooling profile by controlling the emissivity characteristics at different zones, allowing the cooling rate to be optimized at various stages of ingot growth. This dynamic control enables the system to adapt cooling intensity to match the crystal growth conditions, preventing both defect formation and growth instability.
3Manufacturing precision
If thermal gradients are increased to control solid-melt interface profile, then defect distribution improves, but cooling efficiency decreases
Solution Approach 1:
The cooling jacket uses surface regions with different emissivity coefficients to create localized thermal zones. The high-emissivity region provides efficient cooling where needed to control the solid-melt interface profile, while the low-emissivity region reduces cooling intensity to maintain overall cooling efficiency. This localized approach allows precise control of thermal gradients without wasting cooling energy throughout the entire ingot.
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 reduces defects in single crystal ingots by controlling cooling profiles, enhancing the quality of the ingot and reducing the propensity for gate-oxide-integrity failures.
Implementation Method 1
a cooling jacket positioned in the growth chamber between the crucible and the growth chamber outlet and including an inner surface defining a cooling passage
Implementation Method 2
The inner surface of the cooling jacket includes a first surface region having a first emissivity coefficient and a second surface region having a second emissivity coefficient larger than the first emissivity coefficient to control a cooling profile of the single crystal ingot
Data Source
AI summary
An ingot puller apparatus for producing a single crystal ingot includes a housing defining a growth chamber and a growth chamber outlet, a crucible positioned in the growth chamber for containing a melt of semiconductor material, a cooling jacket positioned in the growth chamber between the crucible and the growth chamber outlet and including an inner surface defining a cooling passage having an inlet proximate the crucible and an outlet proximate the growth chamber outlet, and a puller positioned to pull the single crystal ingot from the melt and through the cooling passage. The inner surface of the cooling jacket includes a first surface region having a first emissivity coefficient and a second surface region having a second emissivity coefficient larger than the first emissivity coefficient to control a cooling profile of the single crystal ingot.