BAW Resonator Wafer Layout With Multiple kt2 Coupling Coefficients
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Solution Overview
Problem
Conventional methods for adjusting electromechanical coupling coefficients (kt2) in bulk acoustic wave (BAW) resonators on a die or wafer often require uniform treatment of piezoelectric material layers, leading to increased die size and reduced yield, as they lack the ability to efficiently create resonators with varying kt2 values without increasing footprint.
Innovation Solution
Differentially treat piezoelectric material layers of shunt and series resonators through trimming, etching, or doping to achieve distinct kt2 values, allowing for multiple filters with different performance parameters on a single die, reducing die size and optimizing component layout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If uniform treatment of piezoelectric material layers is applied to all resonators on a wafer, then manufacturing simplicity is maintained, but the ability to create resonators with varying kt2 values is lost, requiring increased die size to accommodate different filter requirements
Solution Approach 1:
The patent applies local quality by treating different regions of the piezoelectric material layer differently - some regions receive trimming/etching to reduce thickness and create lower kt2 values, while other regions maintain original thickness for higher kt2 values. This spatial variation in material properties enables multiple resonator types on a single die without increasing overall die size.
Solution Approach 2:
The patent changes the physical parameter of piezoelectric material thickness in different regions to control kt2 values. By selectively reducing thickness in certain areas through trimming or etching, the electromechanical coupling coefficient is modified, enabling creation of resonators with different electrical characteristics from the same base structure.
2Productivity
If multiple filters with different passbands are integrated on a single die, then filter density is enhanced and die size is minimized, but the manufacturing process complexity increases due to required selective treatments
Solution Approach 1:
The patent segments the piezoelectric material layer into different regions with distinct thicknesses and kt2 values. By dividing the uniform layer into zones that will form different resonator types, the manufacturing process can create multiple filter functionalities simultaneously without requiring separate fabrication runs for each filter type.
Solution Approach 2:
The patent performs preliminary trimming or etching of the piezoelectric material layer before completing the resonator fabrication process. This advance modification of material thickness in specific regions allows subsequent processing steps to create multiple resonator types from a single prepared substrate, improving manufacturing efficiency.
3Adaptability or versatility
If resonators with different kt2 values are created by adding separate piezoelectric layers, then kt2 variation is achieved, but die size increases and component layout becomes less efficient
Solution Approach 1:
The patent merges multiple resonator functionalities into a single integrated structure by creating lateral variations in the piezoelectric material layer. Instead of stacking separate layers for different kt2 values, the invention combines different thickness regions within the same layer plane, achieving kt2 diversity while maintaining a compact footprint.
Solution Approach 2:
The patent transitions from vertical layering (adding thickness in the Z-dimension) to lateral variation (changing thickness in the X-Y plane). By modifying the piezoelectric material thickness across different horizontal regions rather than adding separate vertical layers, the invention achieves kt2 diversity without increasing die area.
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
Enables the fabrication of multiple filters with diverse passbands on a single die, minimizing die size and enhancing filter density, while maintaining optimal component placement and reducing parasitics.
Implementation Method 1
each of the plurality of bulk acoustic wave resonators including a piezoelectric material film
Data Source
AI summary
Aspects and embodiments disclosed herein include a radio frequency filter comprising a plurality of series bulk acoustic wave resonators and a plurality of shunt bulk acoustic wave resonators, at least one of the plurality of shunt bulk acoustic wave resonators exhibiting a different electromechanical coupling coefficient than at least one of the plurality of series bulk acoustic wave resonators, at least one of the bulk acoustic wave resonators exhibiting a higher electromechanical coupling coefficient than another one of the bulk acoustic wave resonators having a thicker piezoelectric material layer stack than the another one of the bulk acoustic wave resonators.