Coupled Piezoelectric Resonator Trimming for Frequency Accuracy
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Solution Overview
Problem
Current manufacturing methods for coupled resonator filters (CRFs) face challenges in achieving precise frequency trimming due to inaccuracies in thin film deposition processes, leading to low manufacturing yield and increased production costs, especially for mobile phone applications where tight frequency specifications are required.
Innovation Solution
A method for frequency trimming of CRFs involves forming and trimming multiple layers, with a focus on adjusting the layer thicknesses of the top and bottom electrodes and coupling layers to achieve precise resonance frequencies and bandwidths, using a multi-step process that includes electrical measurements and simulations to determine target layer thicknesses and adjust the layers accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If thin film deposition processes are used to manufacture CRFs, then the manufacturing process is simple and efficient, but the frequency position accuracy is insufficient due to layer thickness variations
Solution Approach 1:
The patent applies preliminary action by performing frequency trimming during the manufacturing process. Specifically, the resonance frequency of each resonator is measured after deposition, and the layer thickness is adjusted (trimmed) before subsequent processing steps. This preliminary frequency correction ensures that despite variations in deposition accuracy, the final CRF meets the required frequency specifications, thereby resolving the contradiction between manufacturing efficiency and frequency position accuracy.
2Manufacturing precision
If frequency trimming is performed on each resonator individually, then the frequency position accuracy is improved, but the manufacturing yield decreases and production costs increase
Solution Approach 1:
The patent merges the trimming operations of multiple resonators into a single integrated process. By measuring the resonance frequencies of all resonators in a CRF and performing coordinated thickness adjustments to satisfy all frequency specifications simultaneously, the patent achieves high frequency accuracy while maintaining high manufacturing yield. This approach avoids the need for individual trimming of each resonator, thereby preventing yield loss and reducing production costs.
3Ease of manufacture
If CRFs are manufactured without frequency trimming, then the production cost is low and manufacturing is simple, but the manufacturing yield is low due to deposition accuracy limitations
Solution Approach 1:
The patent applies self-service by implementing an automated feedback control system in the manufacturing process. The resonance frequency of each resonator is measured, and this measurement is used to automatically determine the required thickness adjustment. This self-correcting mechanism ensures that high manufacturing yield is achieved without requiring complex manual intervention, thereby maintaining ease of manufacture while significantly improving productivity through enhanced yield.
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 allows for the production of high-quality CRFs with improved manufacturing yield and reduced production costs, enabling precise control over resonance frequencies and bandwidths, essential for demanding applications like mobile phones.
Implementation Method 1
a piezoelectric layer separating a top and a bottom electrode
Implementation Method 2
the piezo-layer and the further piezo-layer being acoustically coupled to each other
Data Source
AI summary
A method for manufacturing a coupled resonator device includes forming a first part of a plurality of layers, trimming an exposed layer of the first part and forming a remaining part of the plurality of layers. The coupled resonator device includes a stack of the plurality of layers, the plurality of layers including a first piezo-layer with a first and a second electrode layer sandwiching the first piezo-layer, a second piezo-layer with a first and a second electrode layer sandwiching the second piezo-layer, the first and second piezo-layers being acoustically coupled to each other.