Thin-Film Capacitor Electrode Structure for High-Temperature Reliability

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Solution Overview

Problem

Thin-film capacitors face reliability issues under high temperature loads due to degradation of insulation resistance when exposed to temperatures above room temperature and subjected to voltage over time.

Innovation Solution

A thin-film capacitor design featuring a pair of electrode layers with different metallic materials, where the second electrode layer has a lower melting point main electrode layer and a higher melting point sub-electrode layer sandwiched between the dielectric layer, enhancing reliability by preventing material diffusion and improving adhesion with vias.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a thin-film capacitor uses a single-material electrode layer, then the structure is simple, but reliability under high temperature load deteriorates due to material diffusion

Engineering Contradiction:

Improvereliability with respect to high temperature loadVSAvoidelectrode layer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The electrode layer is segmented into multiple sub-electrode layers (first sub-electrode layer, first main electrode layer, second main electrode layer, second sub-electrode layer) with different metallic materials. Each layer serves a specific function: outer layers (Cu) provide adhesion with vias, while inner layers (Ni, Pd, Pt) prevent material diffusion into the dielectric layer under high temperature conditions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The electrode structure uses composite materials with different properties arranged in specific layers. Cu layers provide excellent adhesion to vias, while Ni/Pd/Pt layers provide diffusion barrier properties. This composite structure combines the advantages of different materials to simultaneously achieve good adhesion and high temperature reliability.

Inventive Principle:

Principle #40Composite materials

2Reliability

If the electrode layer uses materials with high melting points, then resistance to material diffusion improves, but adhesion with copper vias deteriorates

Engineering Contradiction:

Improveresistance to material diffusionVSAvoidadhesion with vias

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

Different regions of the electrode structure have different material compositions optimized for their specific functions. The outer sub-electrode layers are made of Cu for excellent adhesion with copper vias, while the inner main electrode layers use Ni/Pd/Pt with high melting points for diffusion resistance. This local optimization resolves the contradiction between adhesion and diffusion resistance.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The electrode structure acts as an intermediary between the copper vias and the dielectric layer. The Cu sub-electrode layers provide direct adhesion to the vias, while the Ni/Pd/Pt main electrode layers serve as intermediate diffusion barriers that prevent copper atoms from migrating into the dielectric under high temperature conditions.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Duration of action of moving object

If the thin-film capacitor is exposed to high temperature and voltage for long periods, then operational experience is gained, but insulation resistance deteriorates due to material diffusion

Engineering Contradiction:

Improveoperational lifespanVSAvoidinsulation resistance

Core Design Contradiction:

Duration of action of moving objectVSReliability

Solution Approach 1:

The multi-layer electrode structure is designed in advance with diffusion barrier layers (Ni/Pd/Pt) positioned between the copper vias and the dielectric layer. This preliminary protective structure prevents material diffusion before it can occur during long-term high temperature operation, thereby maintaining insulation resistance throughout the operational lifespan.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The electrode structure provides beforehand cushioning against the harmful effects of high temperature operation. The Ni/Pd/Pt main electrode layers act as pre-positioned diffusion barriers that cushion the dielectric layer from copper atom migration, ensuring that insulation resistance is maintained even after prolonged exposure to high temperature and voltage conditions.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS10085343B2Thin-film capacitor and electronic component embedded substrate

Publication Date: 2018.09.25 TDK CORP

AI summary

A thin-film capacitor includes a pair of electrode layers composed of a first electrode layer configured to store positive charges and a second electrode layer configured to store negative charges; and a dielectric layer sandwiched between the pair of electrode layers along a lamination direction. The first electrode layer includes a first main electrode layer in contact with the dielectric layer. The second electrode layer includes a second main electrode layer and a second sub-electrode layer, both of which are formed of different metallic materials. The second sub-electrode layer is sandwiched between the dielectric layer and the second main electrode layer along the lamination direction. The second main electrode layer is formed of a material having a melting point lower than both a melting point of a material of the first electrode layer, or the first main electrode layer, and that of a material of the second sub-electrode layer.