Silicon Single-Crystal Pulling With Dynamic Ar Flow During Counter Doping
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Solution Overview
Problem
The incorporation of a solid dopant into a solid-liquid interface before dissolution causes dislocation in silicon single crystals during counter doping, particularly in the production of IGBTs where reduced Ar gas flow rates are used to lower oxygen content.
Innovation Solution
Adjusting the Ar gas flow rate and pressure in the pulling-up furnace during the addition of a secondary dopant, increasing the flow rate and decreasing the pressure to prevent non-melted dopant incorporation into the solid-liquid interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a secondary dopant is added to the silicon melt during crystal pulling-up to correct resistivity, then the resistivity uniformity is improved, but dislocation occurs in the single crystal
Solution Approach 1:
The patent applies preliminary action by increasing the Ar gas flow rate before adding the secondary dopant to the melt. This preliminary increase in gas flow prevents the dopant from reaching the solid-liquid interface in a non-dissolved state, thereby preventing dislocation while still allowing the dopant to be effectively incorporated into the melt for resistivity correction.
Solution Approach 2:
The patent changes the Ar gas flow rate parameter dynamically during the doping process. The flow rate is increased to a second flow rate (greater than the first flow rate) when the secondary dopant is added, and then restored to the first flow rate after the dopant is fully dissolved. This parameter change ensures complete dissolution of the dopant while maintaining crystal quality.
2Manufacturing precision
If the Ar gas flow rate is reduced to lower oxygen content in the single crystal, then the oxygen concentration is improved, but the dopant dissolution is hindered
Solution Approach 1:
The patent applies dynamics by making the Ar gas flow rate adjustable and time-dependent. The flow rate is dynamically increased during the dopant addition period to ensure complete dissolution, and then dynamically restored to the lower flow rate after the dopant is fully incorporated. This dynamic adjustment allows the process to meet both oxygen concentration control and dopant dissolution requirements.
Solution Approach 2:
The patent implements periodic action by temporarily increasing the Ar gas flow rate during the dopant addition phase and then restoring it to the normal operating flow rate. This periodic variation in gas flow rate ensures that the dopant is fully dissolved without permanently compromising the low oxygen concentration environment needed for high-quality crystal growth.
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
Prevents dislocation of silicon single crystals by ensuring the secondary dopant is fully dissolved in the melt, maintaining uniform resistivity and reducing the risk of defects.
Implementation Method 1
the flow rate of Ar gas supplied to a pulling-up furnace during a first period in which the secondary dopant is not added is set as a first flow rate, and the flow rate of Ar gas supplied to the pulling-up furnace during a second period that includes a period in which the secondary dopant is added is set as a second flow rate that is greater than the first flow rate
Implementation Method 2
These dopants are introduced with a polycrystalline silicon raw material into a quartz crucible and are melted together with the polycrystalline silicon by adding heat with a heater
Implementation Method 3
The CZ method grows a large-diameter single crystal below a seed crystal by immersing the seed crystal in a silicon melt stored in a quartz crucible and gradually pulling up the seed crystal while rotating the seed crystal and the quartz crucible
Data Source
AI summary
Provided is a manufacturing method of a silicon single crystal according to the present invention includes a melting process for generating a silicon melt containing a primary dopant, and a crystal pulling-up process that pulls up a silicon single crystal from the silicon melt. The crystal pulling-up process includes at least one additional doping process for adding a dopant raw material containing a secondary dopant into the silicon melt. A flow rate of Ar gas during a first period in which the secondary dopant is not added is set as a first flow rate, and the flow rate of Ar gas during a second period that includes a period in which the secondary dopant is added is set as a second flow rate that is greater than the first flow rate.