Seed Chuck Assembly Gas Flow Recirculation Control
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Solution Overview
Problem
The Czochralski crystal growth method faces challenges in producing single crystal ingots with low resistivity due to the evaporation of volatile dopants, which leads to deposit formation on crystal pulling system components, resulting in reduced yield and zero dislocation growth.
Innovation Solution
A crystal pulling system with a seed chuck assembly designed to reduce gas flow recirculation cells, featuring a flow guide and specific diameter ratios to enhance purge gas flow and inhibit the formation of recirculation cells, thereby preventing the back transport of evaporated species to the upper dome and receiving chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If large amounts of volatile dopants are added to achieve low resistivity, then the target resistivity is improved, but deposit formation on crystal pulling system components increases
Solution Approach 1:
The system divides the growth chamber into distinct zones with separate gas flow paths. The seed chuck assembly creates a controlled gas flow pattern that separates the lower recirculation cell (near the melt) from the upper recirculation cell (near the dome), preventing mixing and allowing independent control of each zone to reduce deposit formation while maintaining dopant concentration
Solution Approach 2:
Purge gas is introduced as an intermediary substance to carry volatile dopant species away from the melt and prevent their deposition on crystal pulling system components. The purge gas flow acts as a mediator between the dopant source and potential deposition surfaces, transporting harmful species to safe discharge locations
2Manufacturing precision
If volatile dopants are used to achieve low resistivity, then the electrical property is improved, but recirculation cell formation increases leading to back transport of evaporated species
Solution Approach 1:
The system segments the gas flow paths into separate lower and upper recirculation cells by positioning the seed chuck assembly to create distinct flow zones. This segmentation prevents the back transport of evaporated species from the lower cell to the upper cell, maintaining crystal structure integrity while allowing effective dopant incorporation
Solution Approach 2:
The system extracts and removes evaporated species from the lower recirculation cell through controlled purge gas flow before they can be transported to the upper dome and receiving chamber. By taking out these harmful species early in the process, the system prevents particle-induced loss of crystal structure
3Device complexity
If conventional seed chuck assembly is used, then the structure is simple, but gas flow recirculation cells form causing deposit build-up
Solution Approach 1:
The seed chuck assembly incorporates a flow guide with specific geometric features (such as a annular flow passage and optimized outer diameter) that create localized gas flow patterns. This local modification of the seed chuck structure generates controlled purge gas flow that prevents recirculation cell formation and deposit build-up without requiring complete system redesign
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 system effectively reduces the formation of deposits on crystal pulling system components, enhancing the yield of low-resistivity monocrystalline ingots by decoupling lower and upper recirculation cells and inhibiting the back transport of evaporated species, thus preventing particle-induced loss of crystal structure.
Implementation Method 1
reduce gas flow recirculation cells... enhance purge gas flow and inhibit the formation of recirculation cells... decoupling lower and upper recirculation cells
Implementation Method 2
enhance the evaporation of oxygen species from the melt as dopant oxides and suboxides... evaporated species... condense and deposit
Implementation Method 3
which may condense and deposit on components of the crystal pulling system... deposit formation on crystal pulling system components
Data Source
AI summary
Crystal pulling systems for growing monocrystalline ingots from a melt of semiconductor or solar-grade material are described. The crystal pulling systems include seed chuck assemblies designed to reduce formation of deposits on components of the crystal pulling systems by reducing and inhibiting the formation of gas flow recirculation cells within the crystal pulling systems.