Monolithic BAW Resonator Fabrication for Multi-Frequency Integration
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Solution Overview
Problem
Current methods for fabricating bulk acoustic wave (BAW) resonators with multiple frequencies on a single chip face challenges in miniaturization and cost-effectiveness, as they require complex processes and multiple photolithography steps, limiting their scalability and efficiency.
Innovation Solution
A monolithic integrated BAW resonator production method using an imprint template with varying die heights to create grooves of different depths on a substrate, allowing for the sequential stacking of bottom, piezoelectric, and top electrode layers with varying thicknesses, enabling the formation of resonators with distinct frequencies without the need for extensive photolithography, thus simplifying the process and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple photolithography processes are used to form resonators with different piezoelectric layer thicknesses, then resonators of different frequencies can be formed on a single chip, but the production process becomes complex and costs increase
Solution Approach 1:
The patent divides the substrate into multiple regions with different groove depths using an imprint template with multiple imprint dies of varying heights. Each groove depth corresponds to a specific resonator frequency, allowing simultaneous formation of multiple frequency resonators in a single process cycle without requiring sequential photolithography steps.
Solution Approach 2:
The patent performs preliminary action by pre-forming grooves of different depths in the substrate before depositing the piezoelectric layers. The imprint template creates depth-varying structures that serve as physical masks, determining the final piezoelectric layer thickness for each resonator region before any photolithography occurs, thus simplifying subsequent processing.
2Manufacturing precision
If traditional methods are used to form resonators with different piezoelectric layer thicknesses, then frequency selectivity can be achieved, but the number of photolithography steps increases production time and cost
Solution Approach 1:
The substrate is segmented into multiple regions with different groove depths using an imprint template with multiple imprint dies of varying heights. Each groove depth corresponds to a specific resonator frequency, allowing simultaneous formation of multiple frequency resonators in a single process cycle without requiring sequential photolithography steps.
Solution Approach 2:
The patent replaces the optical photolithography system with a mechanical imprinting system. The imprint template with varying die heights mechanically defines the groove depths directly, eliminating the need for multiple photolithography exposure and development cycles to create depth-varying structures, thus significantly reducing production time.
3Volume of moving object
If resonators of different frequencies are formed on a single chip, then miniaturization and integration are achieved, but the production process requires multiple photolithography steps increasing costs
Solution Approach 1:
The patent merges the formation of multiple resonator types with different frequencies into a single integrated process. The imprint template combines multiple imprint dies of different heights into one tool, allowing simultaneous creation of all groove patterns in a single imprinting operation, thereby integrating multi-frequency resonator production without requiring separate photolithography steps for each frequency.
Solution Approach 2:
The patent performs preliminary action by pre-forming grooves of different depths in the substrate before depositing the piezoelectric layers. The imprint template creates depth-varying structures that serve as physical masks, determining the final piezoelectric layer thickness for each resonator region before any photolithography occurs, thus simplifying subsequent processing.
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 method enables the production of multi-band BAW resonators with improved frequency selectivity and miniaturization, reducing production costs and complexity by using a single photolithography process for multiple resonators, thereby addressing the limitations of existing technologies.
Implementation Method 1
Press the mask material layer in a direction of the substrate by using the imprint template, to form, on the mask material layer through imprinting, a plurality of mask grooves with depths consistent with heights of the imprint dies
Implementation Method 2
Perform plasma etching on the substrate by using the mask material layer as a mask, to form, on a surface of the substrate, grooves that one-to-one correspond to positions of the several mask grooves
Implementation Method 3
Form, in the several grooves, bottom electrode layers, piezoelectric layers, and top electrode layers that are sequentially stacked, to form resonators of different frequencies
Data Source
Figure 1~2
Figure 3~4a
Figure 4b~5
AI summary
This application provides a monolithic integrated BAW resonator production method, including: preparing an imprint template (S1); forming a mask material layer on a substrate (S2); pressing the mask material layer by using the imprint template in a direction of the substrate, to form a mask groove (S3); performing plasma etching on the substrate by using the mask material layer, as a mask, that is used to form the mask groove (S4), to form, on the substrate, grooves that one-to-one correspond to positions of several mask grooves; and forming, in the several grooves, bottom electrode layers, piezoelectric layers, and top electrode layers that are sequentially stacked, to form resonators of different frequencies (S5), where thicknesses of several bottom electrode layers are the same and are all less than depths of the grooves, and piezoelectric layer thicknesses of at least two resonators in several resonators are different, or top electrode layer thicknesses of at least two resonators are different.