Vitreous Silica Crucible Inner Surface Control
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Solution Overview
Problem
The existing methods for manufacturing vitreous silica crucibles lack a controlled inner surface property, leading to issues such as melt surface vibration and crystallization defects during the Czochralski method for producing silicon single crystals, particularly for larger diameters, which affects the yield and quality of silicon wafers.
Innovation Solution
A method involving precise temperature control of the silica powder layer, fume, and arc flame during the arc fusing process in a rotating mold, using radiation thermometers to measure and adjust temperatures within optimal ranges (4.8 to 5.2 μm wavelength) to achieve a uniform and stable inner surface property of the crucible.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the diameter of silicon single crystal is increased to manufacture larger wafers, then the productivity and yield of silicon wafers is improved, but the melt surface vibration becomes more severe and the pulling time is lengthened
Solution Approach 1:
The invention changes the physical-chemical parameters of the crucible inner surface by controlling the crystallization process. Specifically, it forms a cristobalite layer with controlled thickness (0.1-10 μm) and specific surface free energy characteristics on the crucible inner surface. This parameter change in the surface properties reduces the interaction between molten silicon and the crucible surface, thereby suppressing melt surface vibration and enabling stable growth of larger diameter silicon single crystals.
2Length of stationary object
If the pulling time is lengthened to grow larger diameter silicon single crystals, then the wafer diameter is increased, but the crucible inner surface reacts with silicon melt causing crystallization and brown ring formation
Solution Approach 1:
The invention performs preliminary action by forming a controlled cristobalite layer on the crucible inner surface before the actual silicon crystal pulling process. This pre-formed layer acts as a protective barrier that prevents direct reaction between the molten silicon and the crucible material during the extended pulling time required for large diameter crystals. The layer is formed by heating the crucible to 1000-1500°C for 1-100 hours before use, creating a stable surface that resists further crystallization and brown ring formation during subsequent crystal growth.
3Volume of moving object
If the crucible inner surface contacts silicon melt for extended time, then larger diameter crystals can be grown, but the surface reacts causing dislocation and deteriorating single crystallization yield
Solution Approach 1:
The invention changes the surface energy parameters of the crucible inner surface by forming a cristobalite layer with specific thickness and density characteristics. This parameter change reduces the chemical reactivity between the crucible surface and molten silicon, preventing dislocation formation and maintaining high single crystallization yield even during extended pulling times for large diameter crystals.
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 enables the production of vitreous silica crucibles with controlled inner surface properties, reducing defects and improving the yield and quality of silicon single crystals by maintaining optimal temperatures, especially for larger crucible diameters, thereby enhancing the productivity and quality of silicon wafers.
Implementation Method 1
radiation thermometers to measure and adjust temperatures within optimal ranges (4.8 to 5.2 μm wavelength)
Implementation Method 2
the silica powder layer is heated and fused by arc discharge generated by carbon electrodes
Implementation Method 3
arc discharge generated by carbon electrodes comprising: a preparation process for determining optimal temperatures during heating and fusing the silica powder layer
Data Source
AI summary
The present invention provides a method of manufacturing a vitreous silica crucible by heating and fusing a silica powder layer in a rotating mold by arc discharge generated by carbon electrodes comprising: a preparation process for determining optimal temperatures during heating and fusing the silica powder layer for one or more selected from the group consisting of the silica powder layer, fume generated during arc fusing, and arc flame generated in the arc discharge; a temperature measuring process for measuring actual temperatures during heating and fusing for one or more selected from the group where the optimal temperatures are determined; and a temperature controlling process for controlling the actual temperatures for one or more selected from the group where the actual temperatures are measured so that the actual temperatures match the optimal temperatures.