Silicon Crystal Pulling Speed Control for Crucible Deformation
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Solution Overview
Problem
Conventional methods for manufacturing defect-free silicon single crystal ingots fail to account for crucible deformation, leading to defective ingots during the multiple pull-up process, which increases the likelihood of defects as the number of ingots pulled increases.
Innovation Solution
A method that calculates and predicts crucible deformation to adjust the pulling-up speed of silicon single crystal ingots, ensuring the optimal conditions for defect-free ingot production by measuring and modifying the setup pulling-up speed based on changes in ingot diameter and silicon melt surface position, thereby maintaining a consistent temperature gradient and preventing ingot defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple ingots are pulled up using the same crucible to increase productivity, then the number of ingots produced increases, but crucible deformation occurs leading to defective ingots
Solution Approach 1:
The patent measures crucible deformation after each pull-up operation and uses this information to predict and adjust the pulling-up speed for the next ingot. This preliminary measurement and adjustment action prevents defect formation before it occurs, allowing multiple ingots to be produced with consistent quality
Solution Approach 2:
The system implements a feedback loop where crucible deformation is measured after each pull-up, this deformation data is used to predict deformation for the next ingot, and the pulling-up speed is adjusted accordingly. This closed-loop control maintains optimal V/G ratio despite cumulative crucible deformation, ensuring consistent ingot quality across multiple production cycles
2Manufacturing precision
If the pulling-up speed is increased to prevent interstitial bulk formation, then defect-free regions increase, but vacancy bulk formation is limited insufficiently
Solution Approach 1:
The patent dynamically adjusts the pulling-up speed parameter based on measured crucible deformation and predicted V/G ratio. By changing the speed parameter in response to actual crucible conditions, the system maintains optimal defect prevention characteristics throughout the pull-up process
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 enables the production of defect-free silicon single crystal ingots over the entire length, maintaining the quality equivalent to the first ingot pulled, even when multiple ingots are produced using the same crucible, by accurately accounting for crucible deformation and adjusting the pulling-up conditions accordingly.
Implementation Method 1
melting the silicon raw material with a heater for mass production (18)
Implementation Method 2
encircling the ingot (11) being pulled up by a heat shield member (24) disposed above a surface of the silicon melt (13)
Implementation Method 3
a temperature gradient in the axial direction near a solid-liquid interface of the silicon melt and the ingot is G (°C /mm)
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3
AI summary
By pulling up an ingot in consideration of deformation of a crucible, generation of the defective ingot is prevented and a plurality of ingots having equivalent quality with the first ingot are pulled up in a multiple pull-up. Firstly, a deformation amount of a crucible for experiment (34) upon melting a silicon raw material and a history of supply power to a heater for experiment (38) are measured to calculate deformation tendency of a crucible for mass production (14). Next, the size of the crucible for mass production is measured, the silicon raw material of the amount equivalent to the amount supplied to the crucible for experiment is melted with a heater for mass production (18), and an initial crucible external position with a predetermined gap (X) is measured before initiating pull-up. Moreover, the deformation amount of the crucible for mass production upon melting the silicon raw material is predicted based on such as a relation between the deformation tendency of the crucible for experiment and the initial crucible external position, an initial crucible internal position when the predetermined gap is provided is predicted based on the deformation amount of the crucible for mass production, and an optimal pulling-up speed of the ingot is derived from predictive calculation to initiate the pull-up of the ingot at the optimal pulling-up speed.