SAW Electrode Contact Layer for Low-Resistance Wiring Interfaces

Solution Overview

Problem

Higher contact resistance between the interdigital transducer electrode and the wiring electrode in surface acoustic wave devices decreases their performance.

Innovation Solution

Incorporating a contact metal layer made of platinum, palladium, or gold between the pad portion of the interdigital transducer electrode and the aluminum-based layer of the wiring electrode to reduce contact resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a simple aluminum-based wiring electrode is used, then the device structure is simple and manufacturing is easier, but contact resistance increases and performance decreases

Engineering Contradiction:

Improvecontact resistanceVSAvoidwiring electrode structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The wiring electrode uses a composite structure combining aluminum-based layer and contact metal layer (platinum, palladium, or gold). The aluminum-based layer provides cost-effectiveness and basic conductivity, while the contact metal layer provides oxidation resistance and low contact resistance, achieving optimal performance through material composition

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The contact metal layer acts as an intermediary between the aluminum-based wiring electrode and the pad portion. This intermediate layer prevents direct oxidation of aluminum, maintains low contact resistance, and ensures reliable electrical connection without compromising the overall simple structure

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If aluminum-based wiring electrode is used without contact metal layer, then manufacturing is simpler and cost is lower, but oxidation occurs and contact resistance increases

Engineering Contradiction:

Improveoxidation resistanceVSAvoidwiring electrode fabrication

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The wiring electrode uses a composite structure combining aluminum-based layer and contact metal layer (platinum, palladium, or gold). The aluminum-based layer provides cost-effectiveness and basic conductivity, while the contact metal layer provides oxidation resistance and low contact resistance, achieving optimal performance through material composition

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The contact metal layer (platinum, palladium, or gold) creates an inert protective environment over the aluminum-based layer, preventing oxidation by acting as a barrier to oxygen exposure, similar to how inert atmospheres protect reactive materials

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

Data Source

PatentUS12308818B2Surface acoustic wave device

Publication Date: 2025.05.20 WIN SEMICON

AI summary

A surface acoustic wave (SAW) device includes: a substrate; a finger portion of an interdigital transducer (IDT) electrode disposed on the substrate; a pad portion of the interdigital transducer electrode electrically connected to the finger portion; and a wiring electrode disposed on the pad portion. The wiring electrode includes a contact metal layer and an aluminum-based layer. The contact metal layer is disposed between the pad portion and the aluminum-based layer. The contact metal layer includes platinum, palladium, or gold.