Bubble-Free Quartz Crucible Coating for Silicon Crystal Growth
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Solution Overview
Problem
Existing methods for forming a devitrified coating on quartz crucibles for silicon crystal growth face challenges in achieving a uniform coating without pinholes, which can lead to erosion and damage when the crucible is reused due to large pinholes allowing molten silicon to flow and cause quartz layer exposure.
Innovation Solution
A method involving the formation of a bubble-free quartz layer with a thickness of 80 μm to 4 mm on the crucible's inner surface, covered with alkaline earth hydroxide and heated to achieve devitrification, reducing pinhole diameter and preventing quartz layer damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a devitrified coating is formed on the inner surface of a quartz crucible using conventional methods, then the coating provides protection against impurity mixing, but pinholes are formed in the coating which allow molten raw material to flow through and cause erosion of the quartz layer during repeated use
Solution Approach 1:
The patent applies preliminary action by forming a bubble-free quartz layer on the inner surface of the crucible before applying the devitrification accelerator. This preliminary layer prevents bubbles from forming in the final devitrified coating, thereby eliminating pinholes that would otherwise allow molten material to erode the quartz layer during repeated use.
Solution Approach 2:
The patent changes the physical parameters of the quartz layer by controlling bubble formation and elimination during the coating process. Specifically, it maintains the quartz layer at a temperature of 600°C or lower during devitrification accelerator application to prevent bubble generation, and ensures complete bubble removal before devitrification occurs, resulting in a pinhole-free coating.
2Productivity
If the crucible is reused to save resources and reduce cost, then resource efficiency improves, but the pinholes in the devitrified coating allow molten raw material to flow through and enlarge erosion and damage with each use
Solution Approach 1:
The bubble-free quartz layer is formed as a preliminary protective measure before devitrification, ensuring that even during repeated use, there are no pinholes for molten material to penetrate and cause erosion. This allows the crucible to be reused multiple times while maintaining structural integrity.
3Manufacturing precision
If a uniform devitrified shell is formed on the crucible surface, then protection against impurity mixing is improved, but it is difficult to achieve uniform coverage without pinholes using conventional devitrification accelerators
Solution Approach 1:
The bubble-free quartz layer serves as a uniform foundation before devitrification accelerator application. This preliminary uniform layer ensures that the subsequent devitrified coating forms evenly across the entire inner surface without pinholes, achieving high manufacturing precision.
Solution Approach 2:
The patent controls temperature parameters during the coating process, maintaining the quartz layer at 600°C or lower during accelerator application to prevent bubble formation. This parameter control ensures uniform coating formation without the complexity of additional equipment modifications.
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 solution results in a devitrified coating with significantly smaller pinholes, minimizing quartz layer exposure and crucible damage during repeated use, ensuring the integrity of the crucible surface.
Implementation Method 1
heating the surface to at least a temperature at which the surface becomes devitrified
Implementation Method 2
forming a devitrified coating on a quartz layer that includes no bubbles and has a very smooth surface
Data Source
AI summary
A coating method for coating a crucible and a quartz crucible for growing a silicon crystal are provided. In the coating method, a bubble-free quartz layer which is 80 μm to 4 mm thick is formed on an inner surface of a crucible for growing a silicon crystal, and the surface of the bubble-free quartz layer is covered with alkaline earth hydroxide, following which heating is performed to a temperature at which the surface becomes devitrified. The surface may be covered by immersing the inner surface in a solution of the alkaline earth hydroxide. The heating may be performed before the crucible for growing silicon crystal is filled with a solid raw material to be melted.