Elastic Wave Device Electrode Diffusion Barrier
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Solution Overview
Problem
Elastic wave devices with interdigital transducer electrodes embedded in tapered grooves on piezoelectric substrates face challenges in improving electrical resistance and frequency characteristics due to reduced crystallinity on sloped electrode portions.
Innovation Solution
Incorporating a diffusion-preventing layer made of Ti or Cr oxide/nitride between conductive layers, specifically a first conductive layer of Al or its alloy and a second conductive layer of higher density metals like Pt, Au, or Cu, to prevent interdiffusion and enhance electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an interdigital transducer electrode is embedded in a tapered groove on a piezoelectric substrate, then the surface of the insulating layer can be planarized and insertion loss can be reduced, but the crystallinity of the electrode on sloped portions is reduced, making it difficult to improve electrical resistance and frequency characteristics
Solution Approach 1:
The electrode is divided into multiple conductive films with different functions: a first conductive layer (Al or Al alloy) for electrical conductivity, a diffusion-preventing layer (Ti or Cr oxide/nitride) to prevent interdiffusion and maintain crystallinity, and a second conductive layer (higher density metal) for additional electrical properties. This segmentation allows each layer to optimize its function, resolving the contradiction between surface planarization and maintaining electrode characteristics.
Solution Approach 2:
A diffusion-preventing layer made of Ti or Cr oxide/nitride is introduced as an intermediary between the first and second conductive layers. This intermediate layer prevents interdiffusion of metal atoms, especially on sloped portions of the tapered groove, thereby maintaining the crystallinity and electrical characteristics of the electrode while still allowing the tapered groove structure to provide surface planarization.
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 use of a Ti or Cr oxide/nitride diffusion-preventing layer effectively suppresses interdiffusion, improving the electric power handling capability and reducing electrical resistance of the interdigital transducer electrodes, even on sloped surfaces.
Implementation Method 1
a diffusion-preventing layer located between the first conductive layer and the second conductive layer... interdiffusion between the first conductive layer and the second conductive layer can be effectively suppressed
Implementation Method 2
elastic wave devices using elastic waves such as surface acoustic waves and boundary acoustic waves... piezoelectric substrate
Data Source
AI summary
An elastic wave device includes a piezoelectric substrate and an interdigital transducer electrode. The piezoelectric substrate includes a principal surface with a groove tapered in lateral cross section. The interdigital transducer electrode is arranged on the principal surface such that at least one portion thereof is located in the groove. The interdigital transducer electrode is a laminate including a first conductive layer, a second conductive layer, and a diffusion-preventing layer located between the first conductive layer and the second conductive layer and made of an oxide or nitride of Ti or Cr.