Graphite Component Ni Concentration Control for Single Crystal Quality
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Solution Overview
Problem
The Czochralski method for manufacturing single crystals is affected by impurities in the graphite material, leading to reduced Life Time (LT) and Light Point Defect (LPD) abnormalities due to high diffusion coefficients of metallic impurities like Ni, which impact crystal quality and increase manufacturing time.
Innovation Solution
Analyzing and maintaining the Ni concentration in graphite components used in the furnace at 30 ppb or less to prevent Ni diffusion into the melt, thereby avoiding LT and LPD abnormalities in the single crystal, using high-sensitivity analysis methods like plasma ashing and acid-dissolving for precise quantification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multi-pulling method is used to increase productivity, then manufacturing time is reduced, but impurity diffusion from graphite material increases causing LT reduction and LPD abnormalities
Solution Approach 1:
The patent changes the purity parameter of the graphite material from conventional standards (0.3-0.5 ppm total impurities) to a specific parameter control where Ni concentration is limited to 30 ppb or less. This parameter change enables the graphite material to withstand the extended processing times of multi-pulling without causing LT reduction or LPD abnormalities, thus resolving the contradiction between productivity improvement and crystal quality maintenance.
2Ease of manufacture
If conventional purity standards for graphite material are used, then manufacturing cost is reduced, but Ni diffusion causes LT reduction and LPD abnormalities
Solution Approach 1:
The patent applies local quality by specifically controlling the Ni concentration in the graphite material to 30 ppb or less, while other impurities can remain at conventional levels. This targeted local quality control addresses the specific problem of Ni diffusion causing LT reduction and LPD abnormalities without requiring complete purification of all impurities, thus balancing manufacturing cost and crystal purity.
3Manufacturing precision
If graphite material with higher purity is used, then crystal quality is improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent changes the purity specification parameter from comprehensive total impurity control to a specific Ni concentration control of 30 ppb or less. This parameter change achieves the necessary crystal purity for high-quality single crystals while avoiding the excessive cost of complete high-purity graphite material, thus resolving the contradiction between crystal purity and manufacturing cost.
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
This approach ensures the production of high-quality single crystals with reduced LT and LPD abnormalities, improving yield and productivity by effectively controlling impurity levels, particularly in multi-pulling processes where multiple crystals are grown from the same crucible.
Implementation Method 1
impurities each having a high diffusion coefficient in graphite, quartz, and silicon diffuse outwards from the graphite material, then diffuse and pass through the quartz crucible containing a melt
Implementation Method 2
a high-sensitivity analysis method for performing plasma ashing and acid-dissolving with respect to a graphite material
Data Source
AI summary
According to the present invention, there is provided a method for manufacturing single crystal based on a Czochralski method, including: analyzing Ni concentration in at least one of graphite components used in a furnace in which the single crystal is manufactured; and manufacturing the single crystal using the at least one of the graphite components when the analyzed Ni concentration is 30 ppb or less. As a result, in manufacture of the single crystal based on the Czochralski method, the method that enables manufacturing high-quality single crystal in which a reduction in LT (Life Time) or an LPD (Light Point Defect) abnormality does not occur can be provided.