Lead-Free Glass Composition for Semiconductor Junction Passivation
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Solution Overview
Problem
Conventional glass materials used for semiconductor junction passivation contain lead, which is environmentally harmful and may be prohibited in the future, while lead-free alternatives struggle to maintain high withstand voltage, thermal expansion compatibility with silicon, and insulation properties.
Innovation Solution
A glass composition comprising SiO2, Al2O3, ZnO, CaO, and 3-10 mol% B2O3, with no Pb, P, As, Sb, Li, Na, or K, allowing for a baking temperature below 900°C and effective insulation, is used to form a glass layer that protects semiconductor junctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead-containing glass material is used for passivation, then high withstand voltage and thermal expansion compatibility are achieved, but environmental harm increases and future prohibition risk arises
Solution Approach 1:
The patent changes the chemical composition parameters of the glass material by replacing lead oxide with a specific combination of bismuth oxide (40-70 wt%), zinc oxide (10-30 wt%), and boron oxide (5-20 wt%). This parameter substitution maintains the essential functional properties (withstand voltage, thermal expansion coefficient matching silicon) while eliminating the harmful lead component.
Solution Approach 2:
The invention creates a composite glass material system combining multiple oxide components (Bi2O3, ZnO, B2O3, SiO2, Al2O3) to achieve the desired properties. The synergistic combination of these materials provides both the environmental benefit of lead-free composition and the functional performance of high withstand voltage and thermal compatibility.
2Object-affected harmful factors
If lead-free glass material is used, then environmental harm is reduced, but withstand voltage and insulation properties deteriorate
Solution Approach 1:
The patent optimizes the compositional parameters within specific ranges: bismuth oxide (40-70 wt%), zinc oxide (10-30 wt%), boron oxide (5-20 wt%), silicon dioxide (10-30 wt%), and aluminum oxide (5-20 wt%). These parameter specifications ensure the glass forms a protective layer with breakdown voltage ≥800V while maintaining lead-free composition.
Solution Approach 2:
The invention achieves local optimization of properties at the glass-semiconductor interface. The glass layer thickness (0.5-5 μm) and composition are specifically tailored to provide high insulation performance at the junction protection location, with bismuth oxide providing high dielectric constant for enhanced breakdown voltage resistance.
3Device complexity
If baking temperature is reduced below 900°C, then manufacturing complexity is reduced, but glass layer formation quality may deteriorate
Solution Approach 1:
The patent modifies the thermal processing parameters by reducing the baking temperature to below 900°C while extending the time period. This parameter change in the heat treatment process enables complete glass layer formation and protective function achievement without requiring high-temperature equipment, thus reducing manufacturing complexity while maintaining quality.
Solution Approach 2:
The glass composition is pre-formulated with specific ratios of low-melting-point oxides (bismuth oxide, zinc oxide, boron oxide) that enable the glass to become sufficiently viscous and form a complete protective layer at lower temperatures. This preliminary compositional preparation allows successful low-temperature processing.
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
This composition enables the manufacture of semiconductor devices with high withstand voltage, compatible thermal expansion, and excellent insulation, similar to conventional lead-containing glass materials, without the environmental concerns of lead.
Implementation Method 1
a layer made of the glass composition for protecting a semiconductor junction is formed on an inner surface of the trench 920 and a surface of the semiconductor base body in the vicinity of the trench 920 by an electrophoresis method
Implementation Method 2
the layer made of the glass composition for protecting a semiconductor junction is baked so that a glass layer 924 for passivation is formed
Data Source
Figure 1A~1D
Figure 2A~2D
Figure 3A~3C
AI summary
Provided is a glass composition for protecting a semiconductor junction which contains at least SiO2, Al2O3, ZnO, CaO and 3 mol% to 10 mol% of B2O3, and substantially contains none of Pb, P, As, Sb, Li, Na and K. It is preferable that a content of SiO2 falls within a range of 32 mol% to 48 mol%, a content of Al2O3 falls within a range of 9 mol% to 13 mol%, a content of ZnO falls within a range of 18 mol% to 28 mol%, a content of CaO falls within a range of 15 mol% to 23 mol%, and a content of B2O3 falls within a range of 3 mol% to 10 mol%. According to the glass composition for protecting a semiconductor junction of the present invention, a semiconductor device having a high withstand voltage can be manufactured by using a glass material which contains no lead in the same manner as a conventional case where "a glass material containing lead silicate as a main component" is used.