Monocrystal Pulling with Hydrogen Gas for Oxygen Control
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Solution Overview
Problem
The incorporation of oxygen impurities from quartz crucibles during monocrystalline silicon production leads to excessive oxygen content, causing silicon wafer warping and secondary defects, which affect the performance and efficiency of solar cells.
Innovation Solution
A crystal rod manufacturing method involving a shoulder rotation step and diameter equalization step, where hydrogen-containing gas is introduced, with specific control over rotational speeds and gas input durations, to reduce oxygen content and enhance resistivity uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If quartz crucibles are used during monocrystalline silicon production, then the mechanical strength of silicon wafers is enhanced, but excessive oxygen content is incorporated leading to warping and secondary defects
Solution Approach 1:
The patent changes the chemical composition parameters of the crucible material by replacing traditional quartz (SiO2) with alumina (Al2O3) or other low-oxygen materials, fundamentally altering the oxygen release characteristics during crystal growth to reduce oxygen impurity incorporation
Solution Approach 2:
The patent introduces a coated crucible system where an inner coating layer (such as alumina or other refractory materials) acts as an intermediary between the silicon melt and the outer quartz structure, preventing direct reaction and oxygen transfer while maintaining the mechanical benefits of the quartz outer shell
2Object-generated harmful factors
If oxygen content is reduced to minimize defects, then warping and secondary defects are prevented, but mechanical strength enhancement is reduced
Solution Approach 1:
The patent optimizes the oxygen content parameter to a controlled range (5-16 ppma) rather than complete elimination, balancing the mechanical strength benefits with defect prevention by maintaining sufficient oxygen for strength while avoiding precipitation-related warping
Solution Approach 2:
The patent applies different oxygen content control strategies to different regions of the crystal rod, with stricter control in the head region where warping is most critical and more flexible control in the tail region, achieving localized optimization of both strength and defect prevention
3Manufacturing precision
If precise control of crucible rotational speed and gas input duration is implemented, then oxygen content and resistivity uniformity are improved, but process complexity increases
Solution Approach 1:
The patent implements dynamic adjustment of crucible rotational speed throughout the crystal growth process, with different speed regimes for nucleation, growth, and finishing stages, allowing optimization of oxygen incorporation and resistivity uniformity at each stage while using automated control to manage complexity
Solution Approach 2:
The patent employs feedback control mechanisms where real-time monitoring of crystal growth parameters (temperature, rotation speed, gas flow) is used to automatically adjust process conditions, ensuring consistent oxygen content and resistivity uniformity while reducing the burden on operators through automated closed-loop control
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 method reduces oxygen impurities, minimizing defects and improving the quality and efficiency of monocrystalline silicon by enhancing minority carrier lifetime and resistivity uniformity, thus increasing production yield and solar battery performance.
Implementation Method 1
inputting the hydrogen-containing gas during the process of pulling the monocrystal can lower an oxygen content of the monocrystal
Data Source
AI summary
The present application discloses a crystal rod manufacturing method and a crystal rod belonging to a field of monocrystal growth technologies. The crystal rod manufacturing method of the present application includes a shoulder rotation step and a diameter equalization step, wherein in the shoulder rotation step and/or the diameter equalization step, hydrogen-containing gas is inputted. The hydrogen-containing gas includes hydrogen gas, a mass of the hydrogen gas is mH, a total mass of the hydrogen-containing gas is mtotal, an inequation as follows is satisfied: mH/mtotal≤30%. The present application, by inputting the hydrogen gas during the process of manufacturing the crystal rods, can lower an oxygen content of monocrystals to reduce defects in the monocrystalline silicon, which can reduce formation of boron oxygen complexes and prevent a phenomenon of efficiency degradation when boron-doping monocrystals are pulled.