Mo-Ta Electrode Bulk Acoustic Resonator for Oxidation Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Bulk acoustic wave resonators face issues with electrode oxidation and reduced crystal orientation of the piezoelectric layer, leading to reliability problems and defects in connection and contact, especially when exposed to moisture.
Innovation Solution
The use of a molybdenum-tantalum alloy for the electrodes in the bulk acoustic wave resonator, with a tantalum content of 0.1 to 50 at%, which provides low specific resistance, facilitates easy etching, and enhances crystal orientation of the piezoelectric layer, thereby preventing oxidation and improving environmental reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrodes are used, then manufacturing cost is low, but electrode oxidation occurs leading to reliability problems
Solution Approach 1:
The patent applies composite materials by forming a multi-layer electrode structure consisting of a first electrode layer (oxidation-resistant material such as molybdenum, tungsten, or their alloys) and a second electrode layer (conductive material such as aluminum or copper). This composite structure combines the oxidation resistance of the first layer with the high conductivity and ease of manufacturing of the second layer, thereby resolving the contradiction between reliability and ease of manufacture.
2Manufacturing precision
If conventional electrodes are used, then manufacturing process is simple, but crystal orientation of piezoelectric layer is reduced
Solution Approach 1:
The patent applies parameter changes by carefully controlling the thickness parameters of the electrode layers. The first electrode layer has a thickness of 10-100 nm and the second electrode layer has a thickness of 50-200 nm. These specific thickness parameters optimize both the crystal orientation promotion (achieved by the thin first layer with specific material properties) and the etching ease (achieved by the thicker second layer that serves as a protective and etchable layer), thereby resolving the contradiction between manufacturing precision and ease of manufacture.
3Reliability
If electrodes are protected from oxidation, then reliability improves, but sheet resistance increases
Solution Approach 1:
The patent applies composite materials to resolve the contradiction between oxidation protection and sheet resistance. The first electrode layer (10-100 nm thick) made of oxidation-resistant materials like molybdenum or tungsten provides the necessary oxidation protection, while the second electrode layer (50-200 nm thick) made of highly conductive materials like aluminum or copper compensates for the higher resistance of the first layer. The combined structure achieves both oxidation protection and low sheet resistance, resolving the contradiction between reliability and manufacturing precision.
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 molybdenum-tantalum alloy electrodes effectively prevent oxidation, maintain low sheet resistance, and enhance crystal orientation, ensuring robust resonance characteristics and reliability of the bulk acoustic wave resonator even in high temperature and humidity environments.
Implementation Method 1
When an electric field is maintained in the piezoelectric layer by applying electrical energy to the lower and upper electrodes, the electric field causes a piezoelectric phenomenon in the piezoelectric layer, thereby causing the resonating part to be vibrated in a predetermined direction.
Implementation Method 2
at least one of a plurality of electrodes of a bulk acoustic wave resonator may be formed using an alloy of molybdenum and tantalum... The molybdenum-tantalum alloy electrodes effectively prevent oxidation
Data Source
AI summary
A bulk acoustic wave resonator includes a substrate, a first electrode and a second electrode disposed on the substrate, and a piezoelectric layer disposed between the first electrode and the second electrode. At least one of the first electrode and the second electrode includes an alloy of molybdenum and tantalum.