Lead-Free Glass Composition for Semiconductor Junction Protection
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Solution Overview
Problem
Conventional glass materials used for semiconductor junction protection contain lead, which is environmentally hazardous and may be prohibited in the future, requiring a lead-free alternative that maintains high breakdown strength and compatibility with silicon wafers.
Innovation Solution
A glass composition comprising SiO2, B2O3, Al2O3, ZnO, and alkaline earth metal oxides like CaO, MgO, and BaO, with specific mole percentage ranges, that has a linear expansion coefficient matching silicon to prevent warping and ensure high breakdown voltage characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead-containing glass material is used for passivation layer, then insulation property and breakdown strength are improved, but environmental harm and potential prohibition occur
Solution Approach 1:
The patent changes the chemical composition parameters of the glass material by replacing lead oxide with a specific combination of metal oxides (B2O3: 10-30 wt%, SiO2: 40-60 wt%, Al2O3: 5-15 wt%, and other metal oxides: 1-10 wt%). This parameter substitution maintains the electrical insulation properties and breakdown strength while eliminating the harmful lead component, resolving the contradiction between reliability and environmental harm.
Solution Approach 2:
The patent creates a composite glass material system combining multiple metal oxides (boron oxide, silicon oxide, aluminum oxide, and other metal oxides) to achieve the desired electrical and mechanical properties. This composite approach replaces the simple lead-based glass with a multi-component system that provides equivalent or superior performance without environmental toxicity, resolving the contradiction between breakdown strength and environmental safety.
2Object-affected harmful factors
If glass composition is changed to remove lead, then environmental safety is improved, but breakdown strength and insulation property may deteriorate
Solution Approach 1:
The patent systematically adjusts the weight percentages of various metal oxides to compensate for the removal of lead. Specifically, B2O3 is set at 10-30 wt% to provide glass network modification and improve electrical properties, while SiO2 at 40-60 wt% maintains the glass structure and provides insulation. This precise parameter control ensures breakdown strength is maintained at environmentally safe composition levels.
Solution Approach 2:
The patent assigns specific functional roles to different metal oxide components within the glass: B2O3 for electrical property enhancement, SiO2 for structural integrity and insulation, Al2O3 for chemical stability, and other metal oxides for additional property tuning. This functional differentiation ensures that each component contributes to maintaining breakdown strength while the overall composition remains lead-free and environmentally safe.
3Reliability
If glass layer is formed to cover pn junction, then junction protection and insulation are improved, but warping may occur due to thermal expansion mismatch
Solution Approach 1:
The patent addresses thermal expansion mismatch by carefully selecting metal oxide combinations that produce a glass material with thermal expansion coefficient compatible with silicon substrates. The specific composition (B2O3: 10-30 wt%, SiO2: 40-60 wt%, Al2O3: 5-15 wt%, other metal oxides: 1-10 wt%) is designed to minimize differential thermal expansion during manufacturing and operation, preventing warping while maintaining junction protection through the glass passivation layer.
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 composition enables the manufacture of semiconductor devices with high breakdown strength and excellent forward and reverse breakdown voltage characteristics without lead, while avoiding warping and crystallization, and maintaining insulation properties.
Implementation Method 1
an average linear expansion coefficient within a temperature range of 50° C. to 550° C. falls within a range of 3.33×10−6 to 4.13×10−6
Implementation Method 2
a glass layer for passivation is formed such that the glass layer covers a pn junction exposure portion
Data Source
AI summary
Provided is a glass composition for protecting a semiconductor junction which contains at least SiO2, B2O3, Al2O3, ZnO and at least two oxides of alkaline earth metals selected from a group consisting of CaO, MgO and BaO, and substantially contains none of Pb, As, Sb, Li, Na and K, wherein an average linear expansion coefficient within a temperature range of 50° C. to 550° C. falls within a range of 3.33×10−6 to 4.13×10−6. A semiconductor device having high breakdown strength can be manufactured using such a glass material containing no lead in the same manner as a conventional case where “a glass material containing lead silicate as a main component” is used.