Czochralski Crystal Growth Pressure Control for Uniform Doping
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Solution Overview
Problem
The Czochralski method for preparing monocrystalline silicon in the solar photovoltaic industry often results in non-uniform distribution of doping elements, leading to significant differences in axial resistivity that fail to meet the requirements of photovoltaic products.
Innovation Solution
A crystal growth method involving controlled furnace pressure changes during the Czochralski process, including initial high pressure to stabilize doping and later low pressure to volatilize impurities, combined with a single crystal furnace vacuum system to enhance vacuumization, ensuring uniform doping and reduced resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If doping element is added during the Czochralski growth process, then semiconductor performance of silicon is improved, but non-uniform distribution of doping element causes large difference in axial resistivity
Solution Approach 1:
The patent applies dynamics by changing the furnace pressure from a static constant value to a dynamic varying value during the crystal growth process. The pressure is adjusted in different stages: initially set to a first value for doping element addition and melting, then changed to a second value for shoulder formation, and finally adjusted to a third value for constant-diameter growth. This dynamic pressure control optimizes doping element distribution uniformity while maintaining semiconductor performance.
Solution Approach 2:
The patent implements parameter changes by systematically varying the furnace pressure parameter throughout the crystal growth process. Different pressure values (first value, second value, third value) are applied at different growth stages to control the behavior of doping elements. This parameter optimization resolves the contradiction between achieving adequate doping for semiconductor performance and maintaining uniform distribution for consistent axial resistivity.
2Ease of operation
If constant pressure is maintained during crystal growth, then process control is simplified, but doping element distribution uniformity deteriorates
Solution Approach 1:
The patent transforms the static constant pressure process into a dynamic multi-stage pressure control process. The furnace pressure is actively adjusted according to the growth stage: first value during initial melting and doping, second value during shoulder formation, and third value during constant-diameter growth. This dynamic approach maintains ease of operation through systematic control while dramatically improving doping element distribution uniformity.
Solution Approach 2:
The patent applies periodic action by implementing distinct pressure control phases corresponding to different growth stages. Each stage has its own optimized pressure value, creating a periodic pattern of pressure adjustment that matches the periodic nature of crystal growth phases. This staged approach simplifies operational control by providing clear pressure guidelines for each phase while ensuring uniform doping distribution throughout the crystal.
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 improves the uniformity of doping element distribution and reduces axial resistivity differences in monocrystalline silicon, enhancing the quality and efficiency of solar cell production.
Implementation Method 1
a vacuum degree of the single crystal furnace is detected; in a case that the vacuum degree of the single crystal furnace does not meet a vacuum requirement, alerting is performed
Implementation Method 2
adding a dopant into the single crystal furnace in an environment at a second furnace pressure
Data Source
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AI summary
The present application discloses a crystal growth method, a single crystal furnace vacuum system, and a Czochralski crystal growth device. The method includes: performing leakage detection on a single crystal furnace in an environment at a first furnace pressure; adding a dopant into the single crystal furnace in an environment at a second furnace pressure, where the second furnace pressure is greater than the first furnace pressure; and performing a crystal pulling process after the dopant is added. The present application can reduce differences in axial concentration distribution of a doping element in doped monocrystalline silicon, improve the uniformity of axial resistivity of the monocrystalline silicon, and also improve production efficiency.