Capacitor Auxiliary Electrode Reduces ESR
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Solution Overview
Problem
Conventional thin-film capacitors with high dielectric constant materials like BST films have high equivalent series resistance (ESR) due to the low electrical conductivity of their electrodes, which affects the Q-factor and insertion loss in filter circuits.
Innovation Solution
The introduction of an auxiliary electrode connected in parallel to the lower electrodes reduces the effective sheet resistance, achieved through a specific configuration where the auxiliary electrode is connected to the lower electrodes at multiple locations and disposed along the outer side portions, using materials like Cu or Al for the connection electrodes and Pt for the lower electrodes, thereby reducing the ESR without increasing the device size or cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If Pt thin films are used as electrodes in thin-film capacitors, then the capacitor can withstand high firing temperatures (800-1000°C) required for BST dielectric layer formation, but the electrical conductivity of the electrodes becomes insufficient, resulting in high ESR
Solution Approach 1:
The patent employs a composite electrode structure consisting of a lower electrode layer (Pt) and an upper electrode layer (Cu or Al) with different material properties. The Pt lower electrode provides high-temperature stability and adhesion to the BST dielectric, while the Cu/Al upper electrode contributes superior electrical conductivity. This composite configuration resolves the contradiction between temperature resistance and electrical conductivity by combining materials that excel in each respective property.
2Ease of manufacture
If the lower electrode is designed as a single continuous layer, then the structure is simple and manufacturing is easy, but the sheet resistance in the in-plane direction is high, leading to high ESR
Solution Approach 1:
The patent segments the lower electrode into multiple independent electrode regions (first lower electrode, second lower electrode, third lower electrode) arranged in a matrix pattern rather than a single continuous layer. This segmentation creates multiple parallel current paths, effectively reducing the sheet resistance in the in-plane direction. The segmented structure maintains manufacturing simplicity while significantly improving electrical conductivity and reducing ESR.
3Area of moving object
If the capacitor size is reduced for compact design, then the device becomes more compact and suitable for miniaturization, but the electrode area decreases, increasing sheet resistance and ESR
Solution Approach 1:
The patent applies local quality optimization by concentrating electrode material and conductivity enhancement in specific regions where current density is highest. The segmented lower electrode structure with multiple regions allows current to be distributed through optimized local paths, reducing sheet resistance without requiring a larger overall footprint. This enables compact capacitor design while maintaining low ESR through strategic local electrode configuration.
Data Source
AI summary
A capacitor that includes a lower common electrode having a first region and a second region, a first upper electrode opposing the first region, a first dielectric layer between the first region and the first upper electrode, a second upper electrode located in a layer in which the first upper electrode is located and opposing the second region, a second dielectric layer between the second region and the second upper electrode, a first connection electrode electrically connected to the first upper electrode, a second connection electrode located in a layer in which the first connection electrode is located and electrically connected to the second upper electrode, and auxiliary electrodes located in a layer different from a layer in which the lower common electrode is located and that connect the first region and the second region of the lower common electrode.