Multi-Piezo Acoustic Wave Resonators With Seamless Material Interfaces
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Solution Overview
Problem
Existing methods struggle to integrate different piezoelectric materials on the same die for acoustic wave devices, leading to challenges in high volume manufacturing while maintaining consistent performance and electrical parameters.
Innovation Solution
A method involving a sacrificial etch stop layer and optimized layout design is used to form a smooth interface between different piezoelectric materials, ensuring a sloped and seamless integration of these layers on the same die.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If different piezoelectric materials are integrated on the same die, then device performance and size are improved, but manufacturing complexity and process variation increase
Solution Approach 1:
The patent divides the die into distinct regions with different piezoelectric materials (e.g., AlN in first region, ScAlN in second region) that can be independently optimized. This segmentation allows each material to be tailored for specific resonator functions while maintaining a unified manufacturing process flow, thereby reducing overall device size without proportionally increasing process complexity.
Solution Approach 2:
The patent employs preliminary patterning steps to define regions for different piezoelectric materials before deposition. By pre-defining the spatial layout and using sacrificial layers to guide material placement, the complex integration of multiple materials is simplified into a sequential process that can be executed in high-volume manufacturing without excessive complexity.
2Reliability
If different piezoelectric materials are formed on the same die, then resonator performance is improved, but die-to-die variation increases
Solution Approach 1:
The patent implements local quality by assigning different piezoelectric materials to specific regions of the die based on resonator type and performance requirements. Each region is optimized locally (e.g., high-coupling ScAlN for band-edge resonators, low-loss AlN for stopband resonators) while maintaining consistent manufacturing parameters across the entire die, thereby improving overall resonator performance without significantly increasing die-to-die variation.
Solution Approach 2:
The patent controls die-to-die variation by maintaining consistent deposition parameters, layer thicknesses, and processing conditions across all regions of the die. By standardizing the manufacturing parameters while varying only the material composition in different regions, the patent achieves local performance optimization without compromising global manufacturing precision and consistency.
3Reliability
If multiple piezoelectric layers are stacked, then device performance is improved, but manufacturing cycle time increases
Solution Approach 1:
The patent merges the fabrication of multiple piezoelectric layers into a single integrated process flow. By depositing different piezoelectric materials in sequence within the same process run and using common patterning and etching steps, the patent achieves multi-layer device performance without proportionally increasing cycle time. The process consolidates what would otherwise be separate manufacturing operations into one efficient workflow.
Solution Approach 2:
The patent maintains continuous useful action by implementing a seamless process flow where deposition of one piezoelectric layer transitions directly into deposition of the next layer without interrupting the manufacturing cycle. The use of sacrificial layers and in-situ patterning ensures that each step builds upon the previous one continuously, maximizing equipment utilization and minimizing idle time while achieving complex multi-layer structures.
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 enables high volume manufacturing of acoustic wave devices with improved performance by optimizing each resonator, achieving both high Q factor and coupling bandwidth without degrading die-to-die variation.
Implementation Method 1
different piezoelectric layers for different resonators on a same die
Data Source
AI summary
One aspect of the present disclosure pertains to a method of forming an acoustic wave device. The method includes forming a reflector stack structure over a substrate, forming a bottom electrode over the reflector stack structure, depositing a first piezoelectric layer over the bottom electrode, patterning the first piezoelectric layer to form a trench exposing a top surface of the bottom electrode and a sloped side surface of the patterned first piezoelectric layer, depositing a second piezoelectric layer in the trench and over the exposed top surface of the bottom electrode and over the first piezoelectric layer, and patterning the second piezoelectric layer to remove portions of the second piezoelectric layer not within the trench.