Acoustic Resonator Buried Temperature Compensation Layer
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Solution Overview
Problem
Existing acoustic resonator devices face challenges with frequency shifts due to temperature changes and power fluctuations, leading to increased power absorption and battery drain in cellular phones, and current temperature compensation methods compromise the acoustic coupling coefficient.
Innovation Solution
Incorporating a buried temperature compensating layer with a positive temperature coefficient, such as silicon dioxide, between the electrode and conductive interposer layer, and using interlayers to prevent oxygen diffusion and enhance piezoelectric layer growth, while maintaining a high acoustic coupling coefficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If oxide material is added to the piezoelectric layer for temperature compensation, then temperature stability is improved, but acoustic coupling coefficient is greatly compromised
Solution Approach 1:
The device is divided into distinct functional layers: a piezoelectric layer for acoustic coupling and a separate temperature compensation layer for thermal stability. This segmentation allows each layer to perform its specific function without compromising the other, resolving the contradiction between temperature stability and acoustic coupling coefficient.
Solution Approach 2:
An interlayer is introduced as an intermediary between the piezoelectric layer and the temperature compensation layer. This interlayer prevents oxygen diffusion from the compensation layer into the piezoelectric layer, thereby protecting the piezoelectric properties while allowing the compensation layer to provide thermal stability.
2Stability of the object's composition
If oxide material is placed in the piezoelectric layer for temperature compensation, then frequency shift is reduced, but piezoelectric layer quality is compromised due to oxygen diffusion
Solution Approach 1:
The interlayer serves as a protective barrier between the oxide material and the piezoelectric layer, preventing oxygen diffusion that would degrade the piezoelectric layer quality. This allows the oxide layer to provide frequency stability without compromising the piezoelectric material integrity.
Solution Approach 2:
The interlayer is deposited beforehand to create a protective barrier before the piezoelectric layer is formed or exposed to oxygen-containing environments. This preliminary protective action prevents oxygen diffusion and maintains piezoelectric layer quality throughout the device lifecycle.
3Stability of the object's composition
If temperature compensation is implemented using conventional methods, then frequency drift is reduced, but device complexity increases due to additional layers
Solution Approach 1:
The temperature compensation layer serves multiple functions: it provides thermal compensation for frequency stability, acts as a diffusion barrier when combined with the interlayer, and maintains a planar structure for subsequent processing. This multi-functionality reduces the need for additional separate layers, managing device complexity while achieving frequency drift reduction.
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 solution effectively stabilizes the resonator's frequency response to temperature changes, reducing power absorption and extending battery life by maintaining a high acoustic coupling coefficient and preventing contamination of the piezoelectric layer.
Implementation Method 1
The oxide material has a positive temperature coefficient of elastic modulus over a certain temperature range. The positive temperature coefficient of the oxide material at least partially offsets the negative temperature coefficients of the metal electrodes and the piezoelectric material, respectively.
Implementation Method 2
A BAW resonator, for example, is an acoustic stack that generally includes a layer of piezoelectric material between two electrodes. Acoustic waves achieve resonance across the acoustic stack
Implementation Method 3
the interlayer prevents oxygen diffusion from the temperature compensating layer to the piezoelectric layer
Implementation Method 4
Acoustic waves achieve resonance across the acoustic stack, with the resonant frequency of the waves being determined by the materials in the acoustic stack and the thickness of each layer
Data Source
AI summary
An acoustic resonator comprises: an acoustic resonator device comprises: a composite first electrode disposed over a substrate, the composite first electrode comprising: a first electrically conductive layer provided over the substrate; a first interlayer disposed on the first electrical conductive layer; a buried temperature compensation layer disposed over the first interlayer; a second interlayer disposed over the temperature compensation layer; a second electrically conductive layer disposed over the second interlayer, a piezoelectric layer disposed over the composite first electrode; and a second electrode disposed over the piezoelectric layer.