Tantalum Oxide Capacitor Film with Graded Fluorine Distribution
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Solution Overview
Problem
Existing capacitors with fluorine-including tantalum oxide experience capacitance degradation due to a high affinity with solid electrolytes, limiting their performance.
Innovation Solution
A tantalum oxide film with a specific configuration, including a first portion with high fluorine concentration, a second portion with lower fluorine concentration closer to the solid electrolyte, and optionally a third portion with even lower fluorine concentration closer to the metallic tantalum, is used to suppress capacitance degradation and maintain high relative permittivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluorine-including tantalum oxide is used in capacitors, then high relative permittivity is achieved, but capacitance degradation occurs due to high affinity with solid electrolyte
Solution Approach 1:
The patent applies local quality by creating a tantalum oxide film with non-uniform fluorine distribution. The film contains a first portion with high fluorine concentration (providing high relative permittivity) and a second portion with low fluorine concentration (providing low affinity with solid electrolyte). This spatial variation in composition allows different regions to serve different functions: the high-fluorine region maintains high capacitance while the low-fluorine region prevents harmful interactions with the solid electrolyte.
Solution Approach 2:
The patent segments the tantalum oxide film into distinct portions based on fluorine concentration. The film is divided into a first portion (high fluorine concentration) and a second portion (low fluorine concentration), where each segment has optimized properties for its specific function. This segmentation allows the capacitor to simultaneously achieve high relative permittivity and suppress capacitance degradation.
2Reliability
If fluorine concentration is increased to maintain high relative permittivity, then capacitance is improved, but affinity with solid electrolyte increases causing degradation
Solution Approach 1:
The patent resolves this contradiction by making the fluorine concentration spatially variable rather than uniform. The first portion of the film has high fluorine concentration to provide high relative permittivity and capacitance, while the second portion has low fluorine concentration to minimize harmful interactions with the solid electrolyte. This local differentiation allows both requirements to be satisfied simultaneously in different regions of the same film.
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 capacitor exhibits high capacitance and low dielectric loss tangent, with capacitance ratios of 83% or more and dielectric loss tangents of 0.20 or less, effectively addressing capacitance degradation issues.
Implementation Method 1
a thin polycrystalline TaO2F film having a relative permittivity of 60 at 1 MHz is described
Data Source
AI summary
A capacitor includes metallic tantalum, a solid electrolyte, and a tantalum oxide film. The tantalum oxide film is disposed between the metallic tantalum and the solid electrolyte. A first portion includes fluorine. A second portion is in contact with the first portion, the second portion being closer to the solid electrolyte than the first portion in a thickness direction of the tantalum oxide film. A fluorine concentration in the second portion is lower than a fluorine concentration in the first portion.