Silicon Single Crystal Rod Oxygen Control via Pressure and Pumping
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Solution Overview
Problem
Conventional methods for producing silicon single crystal rods using the Czochralski process result in high oxygen content, leading to defects and reduced efficiency in solar cells due to the slow cooling process and thermal history, which causes oxygen to concentrate and act as an impurity, affecting mechanical and electrical properties.
Innovation Solution
A method involving a crystal pulling process with controlled furnace pressure and inert gas flow rates, where the pressure gradually decreases and the pumping rate increases, enhancing oxygen volatilization and gas circulation to reduce oxygen content in the silicon single crystal rod, and using a single crystal furnace with multiple inlet pipes to improve gas flow efficiency and reduce oxygen impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CZ method is used with manual pulling speed setting, then crystal growth can be achieved, but oxygen content increases and manufacturing precision deteriorates
Solution Approach 1:
The patent replaces manual mechanical control of pulling speeds with an automated control system that uses sensors and controllers to regulate the crystal growth process, enabling precise control of oxygen content and other parameters without manual intervention
Solution Approach 2:
The patent implements feedback control by using sensors to monitor crystal growth parameters in real-time and adjusting the pulling speed and other parameters accordingly, ensuring consistent oxygen content control and high manufacturing precision throughout the growth process
2Object-affected harmful factors
If thermal history is not controlled, then growth process is simple, but oxygen concentrates and creates harmful effects
Solution Approach 1:
The patent applies preliminary action by pre-heating the crystal seed before insertion into the molten silicon, and by controlling the cooling rate during the growth process, preventing oxygen concentration and harmful donor effects before they can occur
Solution Approach 2:
The patent changes thermal parameters dynamically during the growth process, adjusting heating and cooling rates at different stages to control oxygen distribution and prevent the formation of harmful oxygen donors while maintaining simple process equipment
3Manufacturing precision
If cooling rate is reduced, then crystal quality improves, but production time increases
Solution Approach 1:
The patent applies periodic action by implementing cyclic heating and cooling patterns during the growth process, where controlled heating periods prevent oxygen concentration while cooling periods enable crystal quality improvement, achieving both goals without excessive total time
Solution Approach 2:
The patent uses dynamic control of cooling rates, adjusting the cooling speed in real-time based on crystal growth stage and oxygen content, enabling fast cooling when quality is critical and slower cooling when time permits, optimizing the balance between crystal quality and production time
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 effectively reduces oxygen content and improves the radial uniformity of silicon single crystal rods, enhancing the quality and performance of solar cells by accelerating oxygen removal and improving gas circulation within the furnace.
Implementation Method 1
enhancing oxygen volatilization and gas circulation to reduce oxygen content in the silicon single crystal rod
Implementation Method 2
enhancing oxygen volatilization and gas circulation to reduce oxygen content in the silicon single crystal rod
Data Source
AI summary
A method for preparing a silicon single crystal rod is provided. The method includes a crystal pulling process including a melt contacting operation, a seeding operation, a shoulder releasing operation, a shoulder rotating operation, a diameter equalizing operation, and a closing operation in sequence. Each operation of the crystal pulling process has a furnace pressure less than or equal to 500 Pa and a pumping rate greater than or equal to 1000 m3/h.