Resonator Electrode Layout for Thin Excitation and Strong Extraction Paths
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Solution Overview
Problem
Existing piezoelectric resonator elements face issues with the fragility of extraction electrodes due to their thin thickness, which can lead to breakage and increased sheet resistance, particularly when formed over steps in the substrate.
Innovation Solution
A method of manufacturing a resonator element with a substrate having thin-wall and thick-wall parts, where the electrode part includes a first electrode layer and a second electrode layer, with the second electrode layer being thicker and used for both pad and extraction electrodes, and a metal layer etching process to reduce the wall thickness of the metal layer in the excitation electrode area, preventing breakage and controlling sheet resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the extraction electrode is made thinner to achieve higher frequency, then the frequency is improved, but the electrode becomes easy to break and sheet resistance increases
Solution Approach 1:
The invention transitions from a single-layer electrode structure to a multi-layer electrode structure. The extraction electrode is divided into a first extraction electrode layer and a second extraction electrode layer with different thicknesses, allowing different portions of the electrode to have different thicknesses optimized for different functions.
Solution Approach 2:
Different portions of the extraction electrode are given different thicknesses to optimize local properties. The first extraction electrode layer has a first thickness in the excitation electrode placement area and a second thickness in the pad electrode placement area, where the first thickness is smaller than the second thickness. This allows the electrode to be thin where high frequency is needed and thick where structural strength is needed.
2Speed
If the extraction electrode thickness is reduced for higher frequency, then the frequency response is improved, but the sheet resistance increases
Solution Approach 1:
The invention adds a vertical dimension to the electrode design by creating multiple layers with different thicknesses. The first extraction electrode layer provides low sheet resistance in the pad electrode placement area where thick coverage is needed, while the second extraction electrode layer provides thin profile in the excitation electrode placement area for high frequency response.
Solution Approach 2:
The extraction electrode is segmented into two distinct layers: a first extraction electrode layer and a second extraction electrode layer. Each layer serves different functional purposes - the first layer provides electrical connection and low resistance, while the second layer provides the thin profile needed for high frequency operation.
3Ease of manufacture
If a single-layer thin extraction electrode is formed, then the manufacturing process is simple, but the electrode is fragile and prone to breakage
Solution Approach 1:
The invention solves the fragility problem by adding a vertical dimension with multiple layers. The first extraction electrode layer acts as a structural support layer that prevents breakage, while the second extraction electrode layer provides the thin profile needed for high frequency operation. This layered approach maintains manufacturing simplicity while dramatically improving durability.
4Strength
If the extraction electrode is made thicker to prevent breakage, then the mechanical strength is improved, but the frequency response deteriorates
Solution Approach 1:
The invention applies local quality by making the extraction electrode thick in the pad electrode placement area for mechanical strength and low sheet resistance, while keeping it thin in the excitation electrode placement area for high frequency response. This is achieved by forming the first extraction electrode layer with different thicknesses in different areas.
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 solution enhances the mechanical strength and vibration characteristics of the resonator element by preventing electrode breakage and minimizing sheet resistance, resulting in improved electrical reliability and reduced manufacturing costs.
Implementation Method 1
a metal layer etching step of etching the metal layer arranged in the excitation electrode placement area via the protective film to thereby reduce a wall thickness of the metal layer
Implementation Method 2
JP-A-2014-7693 (Document 1) discloses a piezoelectric resonator element having a so-called inverted mesa structure
Data Source
AI summary
A method of manufacturing a resonator element including a substrate having a thin-wall part and a thick-wall part, and an electrode part having an excitation electrode arranged in an excitation electrode placement area of the thin-wall part, a pad electrode arranged in a pad electrode placement area of the thick-wall part, and an extraction electrode which is configured to couple the excitation electrode and the pad electrode to each other, and which is arranged in an extraction electrode placement area of the substrate, includes a metal layer formation step of forming a metal layer on the substrate, a protective film formation step of forming a protective film in an area overlapping at least a part of the extraction electrode placement area in a plan view on the metal layer, and a metal layer etching step of etching the metal layer arranged in the excitation electrode placement area via the protective film to thereby reduce a wall thickness of the metal layer.