Alkali-Free Boron Aluminosilicate Glass for High Crystallization Margin
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Solution Overview
Problem
Existing substrate glasses for polysilicon transistors lack both high thermal stability and high devitrification resistance, leading to deformation and production issues during high-temperature processing, which affects the manufacturing process and increases costs.
Innovation Solution
An alkali-free boron aluminosilicate glass composition with specific mole percentages of SiO2, Al2O3, B2O3, MgO, CaO, SrO, BaO, and SnO2, optimized for high thermal stability and crystallization margin, prepared through a melting and overflow downdraw process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the processing temperature is increased to 450-600°C for polysilicon transistor fabrication, then electron mobility and switching speed are improved, but substrate glass deformation occurs due to insufficient thermal stability
Solution Approach 1:
The patent changes the chemical composition parameters of the glass substrate by formulating an alkali-free boron aluminosilicate system with specific oxide ratios (SiO2: 68.54-72.82%, Al2O3: 11.84-13.5%, B2O3: ≤2.23%, MgO: 4.72-6.6%, CaO: 4.65-5.8%, SrO: 0.8-1.5%, BaO: 3.2-3.79%). This composition adjustment raises the strain point above 735°C, enabling the glass to maintain dimensional stability during high-temperature polysilicon processing while supporting the required electron mobility performance
Solution Approach 2:
The patent creates a composite glass system combining multiple oxide components (silica, alumina, boron oxide, magnesia, lime, strontia, and baryta) in specific proportions. This composite formulation synergistically enhances thermal stability through the combined effects of high-strain-point silica-alumina network and devitrification-resistant boron-magnesium-calcium phases, allowing simultaneous achievement of thermal resistance and electrical performance
2Stability of the object's composition
If the production temperature is increased for high thermal stability glass, then thermal resistance is improved, but refractory material corrosion increases and stone defects occur
Solution Approach 1:
The patent optimizes the chemical composition parameters to achieve a strain point above 735°C through an alkali-free boron aluminosilicate system. The controlled B2O3 content (≤2.23%) and alkaline earth metal oxide ratios ((MgO+CaO+SrO+BaO)/Al2O3: 1.15-1.30) create a glass that attains high thermal resistance at a relatively moderate melting temperature of 1590-1630°C, reducing refractory corrosion compared to conventional high-temperature glasses
Solution Approach 2:
The patent applies local quality by creating specific phase compositions within the glass matrix. The boron-magnesium-calcium-strontium-barium phase distribution provides localized thermal stability and chemical resistance, while the silica-alumina network provides structural integrity. This heterogeneous phase structure enables high thermal resistance at lower processing temperatures, minimizing refractory material attack
3Stability of the object's composition
If the forming temperature is increased to improve thermal stability, then strain point is improved, but crystallization risk increases and service life of production line decreases
Solution Approach 1:
The patent changes the composition parameters to achieve a strain point above 735°C through an optimized alkali-free boron aluminosilicate formulation. The specific ratio of network formers (SiO2+Al2O3: 81.63-84.66%) to modifiers, combined with controlled B2O3 content, raises the strain point while keeping the melting temperature at 1590-1630°C, reducing the thermal load on production equipment and extending service life
Solution Approach 2:
The patent optimizes the liquidus temperature parameter by controlling the glass composition, achieving a liquidus temperature of 1180-1220°C. This creates a crystallization margin of 370-450°C between the liquidus temperature and the forming temperature (1270-1310°C), preventing cold-end devitrification and ensuring production line stability without requiring excessive forming temperatures
4Stability of the object's composition
If the liquidus temperature is reduced to widen crystallization margin, then forming process stability is improved, but thermal stability may be compromised
Solution Approach 1:
The patent simultaneously optimizes multiple composition parameters: SiO2 (68.54-72.82%), Al2O3 (11.84-13.5%), B2O3 (≤2.23%), MgO (4.72-6.6%), CaO (4.65-5.8%), SrO (0.8-1.5%), and BaO (3.2-3.79%). This coordinated parameter adjustment achieves a liquidus temperature of 1180-1220°C while maintaining strain point above 735°C, creating a crystallization margin of 370-450°C that ensures both forming stability and thermal performance
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 glass achieves high strain point temperatures above 735°C, low liquidus viscosity, and wide crystallization margin, reducing deformation, improving production yield, and extending production line life while lowering costs.
Implementation Method 1
a glass with high thermal stability (i.e., a glass with a high strain point) can prevent deformation caused by poor thermal resistance during a thermal treatment stage of panel manufacturing
Implementation Method 2
Only when the liquidus temperature of the substrate glass is controlled below a certain threshold, and a difference between the forming temperature and the liquidus temperature (i.e., a crystallization margin) is widened, can the forming process proceed normally
Data Source
AI summary
The present disclosure relates to the technical field of electronic glass, and specifically relates to an alkali-free boron aluminosilicate glass with high thermal stability and high crystallization margin and a method for preparing the same. alkali-free boron aluminosilicate glass thermal stability In mole percentage, raw materials for preparing the alkali-free boron aluminosilicate glass with high thermal stability and high crystallization margin include: 68.54 to 72.82% SiO2, 11.84 to 13.5% Al2O3, ≤2.23% B2O3, 4.72 to 6.6% MgO, 4.65 to 5.8% CaO, 0.8 to 1.5% SrO, 3.2 to 3.79% BaO, and 0.1% SnO2, SiO2+Al2O3 is 81.63 to 84.66%, and (MgO+CaO+SrO+BaO)/Al2O3 is 1.15 to 1.30.