Elastic Wave Resonator Frequency Tuning by Local Thickness Regions
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Solution Overview
Problem
The existing methods for manufacturing piezoelectric thin film resonators and filters require multiple frequency adjustments across a wafer surface, leading to increased process complexity and cost due to variability in film thickness, which can only be adjusted at a single location at a time.
Innovation Solution
A method involving a laminating step to form elastic wave devices with a measuring step to assess frequency distribution, followed by an adjusting step where an adjusting region with varying thickness is formed at each resonance portion to match the frequency distribution, allowing for frequency adjustments in a single patterning process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple frequency adjustments are performed across the wafer surface to compensate for film thickness variability, then the resonance frequency uniformity is improved, but the process complexity and manufacturing cost increase
Solution Approach 1:
The wafer surface is divided into multiple frequency adjustment regions, where each region corresponds to a specific film thickness range. This segmentation allows different frequency adjustment patterns to be applied to different regions, enabling parallel processing and reducing the overall number of adjustment steps required across the entire wafer surface
Solution Approach 2:
Different frequency adjustment patterns are applied to different regions of the wafer surface based on the local film thickness characteristics. Each region receives a customized adjustment pattern that matches its specific frequency deviation, allowing for precise local correction without affecting other regions, thereby improving overall frequency uniformity while streamlining the adjustment process
2Manufacturing precision
If multiple frequency adjustments are performed across the wafer surface, then the resonance frequency uniformity is improved, but the manufacturing cost increases
Solution Approach 1:
The wafer surface is divided into multiple frequency adjustment regions, where each region corresponds to a specific film thickness range. This segmentation allows different frequency adjustment patterns to be applied to different regions, enabling parallel processing and reducing the overall number of adjustment steps required across the entire wafer surface
Solution Approach 2:
Different frequency adjustment patterns are applied to different regions of the wafer surface based on the local film thickness characteristics. Each region receives a customized adjustment pattern that matches its specific frequency deviation, allowing for precise local correction without affecting other regions, thereby improving overall frequency uniformity while streamlining the adjustment process
3Manufacturing precision
If the film thicknesses of the electrode films and piezoelectric film are adjusted to compensate for frequency variability, then the resonance frequency is improved, but the structural integrity and device performance may deteriorate
Solution Approach 1:
Frequency adjustment patterns are applied locally to specific regions of the wafer surface rather than uniformly across the entire structure. This localized approach allows frequency compensation without significantly altering the overall film thickness and structural integrity of the piezoelectric resonator devices
Solution Approach 2:
Instead of adjusting frequency by changing the vertical dimension (film thickness), the invention applies frequency adjustment patterns in the horizontal dimension (surface area distribution). This dimensional shift allows frequency tuning while preserving the original film thickness and structural characteristics that ensure device reliability
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
This approach simplifies the frequency adjustment process, reducing the number of steps required to achieve uniform frequency characteristics across multiple elastic wave devices on a substrate, thereby improving yield and reducing costs.
Implementation Method 1
an elastic wave is generated as a result of a reverse piezoelectric effect in the piezoelectric film that is sandwiched between the upper electrode and the lower electrode
Implementation Method 2
a strain created by the elastic waves is converted into an electrical signal by the piezoelectric effect
Implementation Method 3
Because such elastic waves are totally reflected at the surfaces where the upper electrode film and the lower electrode film, respectively, are in contact with the air
Implementation Method 4
they become vertically oscillating waves with the main direction of displacement along the thickness direction of the piezoelectric film. It is possible to obtain an resonator (or a filter formed with a plurality of resonators that are connected) having prescribed frequency characteristics, by taking advantage of such resonance phenomenon
Data Source
AI summary
A method of manufacturing an elastic wave device is provided with a lamination step of forming, on a substrate (1), a plurality of elastic wave devices, each of which includes a lower electrode (2), a piezoelectric film (3), and an upper electrode (4); a measuring step for measuring the operation frequency distribution of the elastic wave devices on the substrate (1); and an adjusting step for forming an adjusting region, in which the thickness of the elastic wave device is different from the thicknesses of other portions in a resonance portion of each elastic wave device, corresponding with the distribution of the operation frequencies. The adjusting region is formed so that the size of the area of the adjusting region of the resonator portion of each elastic wave device is different in accordance with the operation frequency distribution that is measured. Thus, the frequency characteristics of the elastic wave devices are easily adjusted by a small number of steps.