Silicon Nitride Crucible Coating for Oxygen Control
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Solution Overview
Problem
Conventional crucibles used in directional solidification processes for producing multicrystalline silicon ingots for solar energy applications face issues with high oxygen content, leading to light-induced degradation, and inadequate ingot-release characteristics, which affect the quality and yield of the silicon wafers.
Innovation Solution
A crucible coating composition comprising silicon nitride, a medium, and sintering agents like yttria and silica is applied to the inner surface, with varying compositions on different areas to minimize oxygen exposure and enhance ingot release, using a combination of binders and dispersants to improve adhesion and reduce residual carbon content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional coating is applied to the crucible, then the ingot-release characteristic is improved, but the oxygen content in the silicon ingot increases leading to light-induced degradation
Solution Approach 1:
The patent applies different coating compositions to different areas of the crucible inner surface. A first coating composition is applied to a first area and a second coating composition containing an additive is applied to a second area. This local differentiation allows the coating to provide release properties where needed while minimizing oxygen contamination in critical zones, thereby resolving the contradiction between ease of operation and harmful factors.
2Object-affected harmful factors
If a coating is applied to the crucible to reduce oxygen content, then the quality of silicon wafers is improved, but the adhesion of the coating to the crucible may be insufficient
Solution Approach 1:
The patent uses composite coating compositions that combine silicon nitride with specific additives (such as yttria, silica, and carbon) to create a multi-functional coating system. This composite structure provides both low oxygen content and improved adhesion to the crucible surface, simultaneously addressing quality requirements and structural integrity needs.
3Object-affected harmful factors
If silicon nitride coating is applied to the crucible, then the oxygen content in silicon is reduced, but the coating may not adhere properly without additional additives
Solution Approach 1:
The patent introduces intermediary substances (additives such as yttria, silica, carbon, and binders) that facilitate the bonding between silicon nitride coating and the crucible surface. These intermediaries act as mediators that enable proper adhesion while maintaining the low oxygen content property of the silicon nitride, making the coating process feasible and effective.
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 approach results in multicrystalline silicon ingots and wafers with reduced oxygen content and improved ingot-release characteristics, minimizing light-induced degradation and ensuring efficient crucible-to-ingot separation without cracking.
Implementation Method 1
A coating composition comprising silicon nitride, a medium, and sintering agents like yttria and silica is applied to the inner surface
Implementation Method 2
a sintering agent selected from yttria and silica
Data Source
AI summary
Silicon nitride coated crucibles for holding melted semiconductor material and for use in preparing multicrystalline silicon ingots by a directional solidification process; methods for coating crucibles; methods for preparing silicon ingots and wafers; compositions for coating crucibles and silicon ingots and wafers with a low oxygen content.