Bulk Acoustic Resonator Thickness Deviation Control
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Solution Overview
Problem
As the size of film bulk acoustic resonators increases, their performance deteriorates due to thickness deviations in the substrate and membrane layers, leading to reduced resonance quality and overall performance degradation.
Innovation Solution
The bulk acoustic resonator design incorporates a substrate and membrane layer with a thickness deviation of 170 Å or less, using dielectric or metal layers such as magnesium oxide, zirconium oxide, and aluminum nitride, and a sacrificial layer removed by halide-based etching gas, maintaining a specific width-to-thickness ratio to prevent performance deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the size of film bulk acoustic resonator is increased, then the device can be used in more applications, but performance deteriorates due to thickness deviations
Solution Approach 1:
The patent applies parameter changes by strictly controlling the thickness of the substrate protection layer and membrane layer to be 170 Å or less. This precise parameter control maintains the resonance quality factor while allowing the resonator to operate across multiple frequency bands including personal communications and digital cordless systems, thereby resolving the contradiction between versatility and reliability
Solution Approach 2:
The patent implements local quality by ensuring uniform thickness distribution specifically in the substrate protection layer and membrane layer where acoustic resonance occurs. By maintaining consistent thickness of 170 Å or less in these critical regions while allowing other parts of the device to vary, the resonator achieves high performance across different applications without compromising resonance quality
2Reliability
If the thickness of substrate protection layer and membrane layer is reduced to 170 Å or less, then resonance quality is maintained, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by forming the substrate protection layer and membrane layer with controlled thickness of 170 Å or less before subsequent processing steps. This preliminary thickness control prevents cumulative deviations that would occur if thickness were adjusted later, thereby maintaining resonance quality while establishing clear manufacturing specifications upfront
Solution Approach 2:
The patent replaces mechanical thickness measurement and adjustment methods with precise deposition process control. By using controlled chemical vapor deposition or atomic layer deposition techniques to form layers of 170 Å or less, the manufacturing process achieves the required precision without relying on post-fabrication mechanical adjustments, thus maintaining resonance quality with feasible manufacturing precision
3Ease of manufacture
If sacrificial layer is removed by halide-based etching gas, then cavity is formed successfully, but etching damage may occur to surrounding layers
Solution Approach 1:
The patent applies the intermediary principle by using a sacrificial layer as a mediator between the etching process and the final cavity structure. The sacrificial layer is selectively removed by halide-based etching gas, and the subsequently formed membrane layer acts as a protective intermediary that prevents etching damage to the substrate protection layer and other surrounding structures, thereby enabling successful cavity formation without harmful effects
Solution Approach 2:
The patent applies preliminary anti-action by forming the membrane layer with thickness of 170 Å or less before the etching process. This pre-formed membrane layer serves as a protective barrier that counteracts the potential harmful effects of halide-based etching gas on the substrate protection layer and other sensitive structures, allowing cavity formation while preventing etching damage
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 design maintains high resonance quality and prevents performance degradation by minimizing thickness deviations and damage from etching, ensuring stable operation of the bulk acoustic resonator.
Implementation Method 1
The sacrificial layer may include a silicon-based material, and may be removed by a halide-based etching gas
Implementation Method 2
a piezoelectric layer configured to partially cover the lower electrode
Data Source
AI summary
A bulk acoustic resonator includes: a substrate including an upper surface on which a substrate protection layer is disposed; and a membrane layer forming a cavity together with the substrate, wherein a thickness deviation of either one or both of the substrate protection layer and the membrane layer is 170 Å or less.