Czochralski Monocrystal Melting Setup for Stable Seeding
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Solution Overview
Problem
Existing czochralski monocrystalline processes face challenges in first seeding and shouldering due to improper barium carbonate powder scattering, crucible positioning, and melting power settings, leading to inefficiencies and difficulties in crystal formation.
Innovation Solution
Optimizing the position of barium carbonate powder scattering and crucible positioning, along with adjusting melting power, to enhance the dissolution of barium carbonate into silicon liquid and promote a dense quartz layer formation, thereby improving the first seeding and shouldering survival rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If barium carbonate powder is uniformly attached to the inner wall of the crucible bottom corner, then the powder scattering is simplified, but the dissolution of barium carbonate into silicon liquid is delayed
Solution Approach 1:
The patent applies preliminary action by pre-positioning barium carbonate powder on specific areas of the crucible inner wall (upper, middle, and lower sections) before melting begins. This predetermined distribution ensures that the powder is optimally positioned to dissolve quickly into the silicon liquid as it forms, rather than being uniformly attached at the bottom where dissolution is delayed.
2Ease of manufacture
If the crucible is placed at the lower limit position during material melting, then the setup is simplified, but the melting efficiency decreases and crucible edge collapse occurs
Solution Approach 1:
The patent applies dynamics by making the crucible position adjustable rather than fixed at the lower limit. The crucible can be moved to different heights (first position for efficient melting, second position for preventing edge collapse) depending on the melting stage, optimizing both melting efficiency and crucible safety throughout the process.
3Ease of manufacture
If the crucible is placed at the lower limit position, then the positioning is simplified, but barium powder undergoes excessive high-temperature baking which negatively impacts crucible seeding and shouldering
Solution Approach 1:
The patent applies dynamics by making the crucible position adjustable rather than fixed at the lower limit. The crucible can be moved to different heights (first position for efficient melting, second position for preventing edge collapse) depending on the melting stage, optimizing both melting efficiency and crucible safety throughout the process.
4Productivity
If excessive material melting power is applied, then the melting speed is increased, but the temperature becomes excessively high causing transformation of glassy quartz to crystalline quartz
Solution Approach 1:
The patent applies parameter changes by adjusting the melting power parameters to an optimal range rather than using excessive power. The power is controlled within specific parameters that maintain high melting speed while preventing the temperature from rising to levels that would cause unwanted phase transformation of the crucible quartz from glassy to crystalline form.
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 optimized process reduces the number of times of first seeding and shouldering, increasing the survival rate and enhancing the quality and efficiency of monocrystalline formation.
Implementation Method 1
A heater is started, and the solid silicon material in the crucible is melted into liquid silicon at a high temperature.
Implementation Method 2
the position of barium carbonate powder scattering in the existing technologies is not thoroughly researched, or as disclosed in CN107460538A, uniformly attaching the barium carbonate powder to the inner wall of the crucible bottom corner is not beneficial to quick dissolution of the barium carbonate powder into the silicon liquid
Implementation Method 3
the process of decomposing the barium carbonate powder into barium oxide, and ultimately reacting barium oxide and silicon dioxide to form barium silicate
Implementation Method 4
the presence of barium silicate also promotes formation of a dense crystalline quartz layer at a relatively low temperature in glassy quartz
Data Source
AI summary
Disclosed is czochralski monocrystalline forming process and application thereof. A barium powder scattering position, a position of a crucible for melting, and a melting power in material preparing and melting procedures are changed and optimized: when the barium powder scattering position is at ⅔ of a position above a lower part of a straight arm of the crucible in the vertical direction: the crucible for melting is at a position of −50 mm at the beginning of melting, and at a position of 30 mm when the linear size of a non-melted block at the later stage of melting is 200 mm-300 mm; a main heater power of the melting power is 85 KW, and a bottom heater power is 70 KW.