Lead-Free Passivation Glass Composition for Crack-Resistant Semiconductors
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Solution Overview
Problem
Current lead-free passivation glasses for semiconductor components, such as zinc borate glasses, suffer from chemical instability, high modulus of elasticity leading to cracking, and thermal expansion mismatches, while bismuth-containing glasses face high costs and oxidation issues, necessitating a solution that maintains stability and avoids cracking and gap formation during the passivation process.
Innovation Solution
A melt solder and glass powder composition with specific constituents including SiO2, Al2O3, B2O3, ZnO, and MgO, incorporating a magnesium- and aluminum-containing crystalline additive, which reduces thermal expansion mismatch and enhances acid resistance, thereby minimizing cracking and gap formation during the passivation of semiconductor components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead-free passivation glasses (e.g., zinc borate glasses) are used to replace lead-containing glasses, then environmental compliance is improved, but chemical stability deteriorates
Solution Approach 1:
The patent employs a composite glass composition combining multiple oxide components (B2O3, SiO2, Al2O3, ZnO, MgO) in specific ratios to achieve both lead-free compliance and enhanced chemical stability. The synergistic interaction between these components creates a passivation layer that resists acid etching while meeting environmental requirements.
Solution Approach 2:
The patent optimizes the compositional parameters of the glass, specifically controlling the weight percentages of each oxide component. By adjusting these parameters within defined ranges, the glass achieves optimal chemical stability and etch resistance without containing lead, thus resolving the contradiction between environmental compliance and material stability.
2Reliability
If zinc borate glass is used for passivation, then lead-free compliance is improved, but mechanical stability deteriorates due to high modulus of elasticity
Solution Approach 1:
The patent creates a composite glass system that combines zinc oxide with boron trioxide and other modifiers to reduce the overall modulus of elasticity. This composite approach maintains the lead-free advantage while achieving mechanical properties suitable for semiconductor passivation applications.
Solution Approach 2:
The patent modifies the glass composition parameters, particularly the ratios of ZnO to B2O3 and the addition of MgO and Al2O3, to control the modulus of elasticity. By optimizing these parameters, the glass achieves lower mechanical stress during thermal cycling, preventing crack formation while remaining lead-free.
3Reliability
If zinc borate glass is used for passivation, then lead-free compliance is improved, but thermal compatibility deteriorates due to thermal expansion mismatch
Solution Approach 1:
The patent adjusts the thermal expansion parameters of the glass by modifying its chemical composition. By controlling the proportions of B2O3, SiO2, and metal oxides, the glass achieves a thermal expansion coefficient that closely matches silicon substrates, thereby preventing delamination and cracking during thermal processing while maintaining lead-free status.
Solution Approach 2:
The patent explicitly addresses thermal expansion mismatch by designing a glass composition whose thermal expansion characteristics are matched to the silicon substrate. This is achieved through careful selection and proportioning of glass-forming and modifying oxides, ensuring compatible thermal behavior during manufacturing and operation.
4Reliability
If bismuth-containing glass is used for passivation, then passivation performance is improved, but cost increases and oxidation issues arise
Solution Approach 1:
The patent removes bismuth from the glass composition entirely, extracting this problematic element that causes oxidation issues and high costs. The resulting lead-free, bismuth-free glass formulation achieves comparable or superior passivation performance through alternative compositional strategies using more stable and cost-effective oxides.
Solution Approach 2:
The patent replaces expensive bismuth-containing materials with more economical oxide combinations. The new glass formulation uses abundant, low-cost materials such as boron trioxide, silicon dioxide, and metal oxides, eliminating the need for costly bismuth while maintaining effective passivation functionality.
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 proposed solution effectively reduces the susceptibility to cracking and gap formation, maintains chemical stability, and adjusts thermal expansion to match that of silicon, ensuring a reliable passivation layer without the need for significant changes to existing passivation methods, while being compliant with RoHS regulations.
Implementation Method 1
The average thermal expansion of polycrystalline silicon in the temperature range of 20° C. to 300° C. is ca. 3 ppm/K. In the case of lead containing glasses a mismatch of the thermal expansion due to the smaller E modulus is less critical.
Implementation Method 2
But the chemical stability of these glasses is not sufficient. After the glazing of silicon wafers for the purpose of cleaning they have to be etched with an acid. For that, normally, in the semiconductor industry HNO3 or HF are used.
Implementation Method 3
It is possible that the passivation layer cracks due to the volume contraction during cooling and differences with respect to the thermal expansion.
Data Source
AI summary
The disclosure relates to a glass and a melt solder for the passivation of semiconductor components, the use of the glass or the melt solder for the passivation of semiconductor components, a passivated semiconductor component and a method for passivating semiconductor components.