Silicon Single Crystal Neck Formation via Hydrogen Atmosphere
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Solution Overview
Problem
The existing methods for producing silicon single crystals, such as the Czochralski process, face challenges in achieving a high success rate for dislocation-free neck formation, especially when the constant diameter portion of the neck needs to be larger than 3 mm, which is required for supporting heavier crystals, and current solutions either increase the system size or have low success rates.
Innovation Solution
A process involving a hydrogen-containing atmosphere with a hydrogen gas equivalent concentration of 3 to 20% is used during neck formation, where hydrogen atoms are introduced into the silicon melt to interstitially fix dislocations, preventing their propagation and generation, allowing for the formation of dislocation-free crystals even with larger neck diameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the constant diameter portion of the neck is increased in diameter to support heavier crystals, then the mechanical strength is improved, but the success rate for eliminating dislocations drops sharply
Solution Approach 1:
The patent changes the chemical composition parameter of the atmosphere from inert gas to hydrogen-containing atmosphere (3-20% hydrogen), which fundamentally alters the interaction between the atmosphere and silicon melt. This parameter change enables dislocation elimination success rates of 90-95% even with larger neck diameters (4.5-10 mm) that provide sufficient mechanical strength for heavy crystals.
Solution Approach 2:
Hydrogen acts as an intermediary substance that dissolves into the silicon melt and modifies the solidification process. The hydrogen atoms facilitate dislocation elimination by interacting with the silicon crystal structure during neck formation, enabling both large diameter and high success rate simultaneously.
2Reliability
If the constant diameter portion of the neck is reduced to 3 mm or less to achieve high dislocation elimination success rate, then the success rate for eliminating dislocations is improved, but the mechanical strength is insufficient for supporting heavy crystals
Solution Approach 1:
By changing the atmosphere composition to contain hydrogen (3-20% concentration), the patent enables the neck to achieve both sufficient mechanical strength and high dislocation elimination success rate. This parameter change removes the need to compromise between diameter size and success rate.
3Reliability
If an auxiliary heating mechanism is added to heat the neck during dislocation elimination, then the dislocation elimination success rate is improved, but the device complexity increases and the system size increases
Solution Approach 1:
Hydrogen gas serves as a chemical intermediary that provides the necessary thermal and chemical effects during neck formation without requiring auxiliary heating equipment. The hydrogen-containing atmosphere naturally facilitates dislocation elimination through dissolution into the melt and interaction with the crystal structure during solidification.
Solution Approach 2:
The patent replaces the mechanical/thermal system (auxiliary heating mechanism) with a chemical system (hydrogen-containing atmosphere). This substitution eliminates complex heating equipment while achieving the same or better dislocation elimination效果 through chemical interactions during solidification.
4Strength
If the constant diameter portion of the neck is increased to 4.5 mm or more to support 300 kg+ crystals, then the mechanical strength is sufficient, but the success rate for eliminating dislocations drops to below 50%
Solution Approach 1:
The patent changes the atmosphere composition parameter to contain hydrogen (3-20% concentration), which fundamentally improves the dislocation elimination process. This parameter change enables achieving 90-95% success rates even with large neck diameters (4.5-10 mm) required for supporting heavy 300 kg+ crystals.
Solution Approach 2:
Hydrogen acts as a chemical intermediary that dissolves into the silicon melt and facilitates dislocation elimination during solidification. This intermediary mechanism enables simultaneous achievement of large neck diameter for mechanical strength and high success rate for dislocation elimination.
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 approach significantly increases the success rate for eliminating dislocations, achieving nearly 100% for necks with diameters up to 3 mm and improving it to 90-95% for necks with diameters of 4.5 to 10 mm, enhancing the stability and efficiency of silicon single crystal production.
Implementation Method 1
hydrogen atoms are introduced into the silicon melt to interstitially fix dislocations
Implementation Method 2
hydrogen atoms are introduced into the silicon melt to interstitially fix dislocations, preventing their propagation and generation
Implementation Method 3
When the seed crystal 16 is brought into contact with the surface of the silicon melt 13, the resulting thermal shock generates a high density of dislocations in the seed crystal 16
Implementation Method 4
a crystal starting material melted by the heater 12, i.e., a polysilicon melt 13, is held within the crucible 11
Implementation Method 5
The crucible 11 is composed of a quartz receptacle 11a as an inner layer and, fitted on the outside thereof, a graphite receptacle 11b as an outer layer
Data Source
AI summary
A process for producing a silicon single crystal includes the steps of bringing a seed crystal into contact with a silicon melt, gradually pulling the seed crystal from the melt so as to form a neck having a tapered portion and a constant diameter portion, then pulling a silicon single crystal. The atmosphere used during neck formation is a hydrogen-containing atmosphere prepared by adding a hydrogen-containing substance to an inert gas. The hydrogen-containing substance has a hydrogen gas equivalent concentration in the hydrogen-containing atmosphere of 3 to 20%.