Monocrystal Oxygen Control via Inactive Gas Flow Rate
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Solution Overview
Problem
Existing methods for manufacturing monocrystals struggle to control oxygen concentration uniformly along the crystal length, leading to undesirable oxygen profiles and inability to increase oxygen concentration effectively during the early stages of crystal pulling.
Innovation Solution
A manufacturing method using a pulling-up apparatus with controlled inactive gas flow rates and pressures, where the gas flow rate directly above the dopant-added melt is adjusted between 40 L/min to 400 L/min and chamber pressure between 5332 Pa to 79980 Pa, to manage oxygen concentration by influencing evaporation and convection, allowing precise control of oxygen absorption in the monocrystal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the gas pressure is increased to limit evaporation of silicon oxide material, then oxygen concentration in the monocrystal increases, but the oxygen concentration profile along the longitudinal direction becomes uneven
Solution Approach 1:
The patent applies dynamics by making the gas flow rate variable during the crystal pulling process. The flow rate is increased in stages: initially at a lower rate to allow oxygen incorporation, then increased to control evaporation and limit oxygen loss, and finally adjusted again to achieve the desired oxygen concentration profile. This dynamic adjustment resolves the contradiction between increasing oxygen concentration and maintaining profile uniformity.
Solution Approach 2:
The patent implements periodic action through staged gas flow rate adjustments during different phases of crystal pulling. The process is divided into multiple stages with distinct gas flow rates: an initial stage with lower flow rate, an intermediate stage with increased flow rate, and a final stage with adjusted flow rate. This periodic modulation of gas flow enables precise control over oxygen concentration distribution along the crystal length.
2Quantity of substance
If the gas flow rate above the melt surface is increased to control oxygen absorption, then oxygen concentration in early-pulled crystal increases, but control precision over oxygen concentration decreases
Solution Approach 1:
The patent uses dynamic control of gas flow rate to address this contradiction. By adjusting the gas flow rate in real-time based on the pulling stage and desired oxygen concentration, the system maintains precise control throughout the process. The gas flow rate is dynamically modified to balance oxygen incorporation in early stages with overall concentration control, preventing both oxygen deficiency and loss of control precision.
3Quantity of substance
If the chamber pressure is increased to compensate for oxygen decrease during pulling, then oxygen concentration increases, but the ability to manufacture monocrystal with desirable oxygen concentration is limited
Solution Approach 1:
The patent overcomes the limitation of fixed pressure control by implementing dynamic gas flow rate adjustment. Instead of relying solely on pressure increases, the system modulates gas flow rate throughout the pulling process, enabling flexible adaptation to different oxygen concentration requirements. This dynamic approach provides versatility in manufacturing monocrystals with various oxygen concentration profiles.
Solution Approach 2:
The patent applies parameter changes by modifying multiple process parameters including gas flow rate, chamber pressure, and pulling speed in coordination. By changing these parameters dynamically rather than relying on a single parameter adjustment, the system achieves both desired oxygen concentration and control flexibility. The coordinated parameter changes enable adaptation to different monocrystal 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
This method enables the production of monocrystals with desirable oxygen concentrations by controlling oxygen absorption, reducing differences between intended and actual oxygen profiles, and improving the uniformity of oxygen concentration along the crystal length.
Implementation Method 1
a flow rate of the inactive gas directly above a free surface of the dopant-added melt in the crucible is increased when the monocrystal is manufactured
Implementation Method 2
the oxygen concentration of the monocrystal is decreased as a flow rate of the inactive gas directly above a free surface of the dopant-added melt in the crucible is increased
Data Source
AI summary
Using a pulling-up apparatus, an oxygen concentration of the monocrystal at a predetermined position in a pulling-up direction is controlled based on a relationship in which the oxygen concentration of the monocrystal is decreased as a flow rate of the inactive gas at a position directly above a free surface of the dopant-added melt is increased when the monocrystal is manufactured with a gas flow volume in the chamber being in the range of 40 L/min to 400 L/min and an inner pressure in the chamber being in the range of 5332 Pa to 79980 Pa. Based on the relationship, oxygen concentration is elevated to manufacture the monocrystal having a desirable oxygen concentration. Because the oxygen concentration is controlled under a condition corresponding to a condition where the gas flow rate is rather slow, the difference between a desirable oxygen concentration profile of the monocrystal and an actual oxygen concentration profile is reduced.