Acoustic Device Fabrication With Sacrificial Layer Polishing Control
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Solution Overview
Problem
Conventional methods face challenges in depositing a piezoelectric layer with a desired crystallographic orientation in acoustic devices, making it difficult to achieve precise control over the properties that determine device performance.
Innovation Solution
A method involving the use of a sacrificial layer with controlled thickness and selective polishing to maintain surface roughness, followed by off-axis deposition of a seed layer and piezoelectric layer, ensuring precise crystallographic orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional polishing processes are used to remove the sacrificial layer, then the sacrificial layer is completely removed, but the surface roughness of the bottom electrode is altered and piezoelectric layer growth is compromised
Solution Approach 1:
The patent applies preliminary action by forming a planarization layer (CMP stop layer) before the sacrificial layer that is designed to be selectively removed during polishing. This pre-prepared layer protects the bottom electrode surface from excessive polishing that would alter its roughness, while still allowing complete removal of the sacrificial layer. The planarization layer acts as a sacrificial buffer that absorbs the polishing action, preserving the electrode surface for optimal piezoelectric layer growth.
Solution Approach 2:
The planarization layer serves as an intermediary element between the polishing process and the bottom electrode. It mediates the interaction by being the primary target of polishing removal, thereby protecting the bottom electrode from direct excessive polishing. This intermediary layer enables the polishing process to proceed without harming the electrode surface, resolving the contradiction between complete sacrificial layer removal and surface roughness preservation.
2Reliability
If the sacrificial layer is completely removed by polishing, then no remaining material interferes with device function, but the surface roughness of the bottom electrode is altered affecting piezoelectric layer growth
Solution Approach 1:
The planarization layer is formed in advance with specific material properties and thickness that enable selective removal during polishing. This preliminary structure ensures that when polishing occurs, the planarization layer is removed first, exposing the sacrificial layer for subsequent removal, while the bottom electrode surface remains protected. This pre-planned layer structure resolves the contradiction by providing a controlled removal sequence that preserves electrode surface roughness.
Solution Approach 2:
The patent utilizes parameter changes in material selection and layer thickness to achieve selective removal during polishing. By choosing materials with different polishing removal rates and controlling layer thicknesses, the process enables sequential removal: planarization layer first, then sacrificial layer, while maintaining bottom electrode surface integrity. This parameter control resolves the contradiction between complete sacrificial layer removal and surface roughness preservation.
3Manufacturing precision
If conventional deposition methods are used, then the process is simple, but the crystallographic orientation of the piezoelectric layer cannot be precisely controlled
Solution Approach 1:
The patent applies preliminary action by forming a seed layer with specific crystallographic orientation before depositing the piezoelectric layer. This pre-formed seed layer serves as a template that guides the crystal growth orientation of the subsequent piezoelectric layer. By preparing this oriented seed layer in advance, the process achieves precise crystallographic control without requiring complex in-situ deposition techniques, thus resolving the contradiction between precision and simplicity.
Solution Approach 2:
The seed layer acts as an intermediary between the bottom electrode and the piezoelectric layer, mediating the crystallographic orientation transfer. It provides a crystalline template that directs the growth orientation of the piezoelectric layer, enabling precise orientation control through a relatively simple deposition process. This intermediary approach resolves the contradiction by introducing a intermediate structure that simplifies the overall deposition complexity while achieving high precision orientation control.
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
The method enables improved performance of acoustic devices by maintaining surface roughness and controlling crystallographic orientation, enhancing properties such as inductance and sensitivity.
Implementation Method 1
polishing the sacrificial layer such that a portion of the sacrificial layer remains on the bottom electrode
Implementation Method 2
removing the remaining portion of the sacrificial layer via a cleaning process such that a surface roughness of the bottom electrode is maintained
Implementation Method 3
The resulting acoustic device may thus have improved performance in a number of different domains
Implementation Method 4
subsequent growth of a piezoelectric layer on the bottom electrode can be substantially improved
Data Source
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AI summary
A method for manufacturing an acoustic device includes providing a substrate, providing a bottom electrode over the substrate, providing a sacrificial layer on the bottom electrode, patterning the bottom electrode and the sacrificial layer, polishing the sacrificial layer such that a portion of the sacrificial layer remains on the bottom electrode, and removing the remaining portion of the sacrificial layer via a cleaning process such that a surface roughness of the bottom electrode is maintained. By performing the polishing such that a portion of the sacrificial layer remains on the bottom electrode and subsequently removing that portion of the sacrificial layer via a cleaning process that maintains the surface roughness of the bottom electrode, the subsequent growth of a piezoelectric layer on the bottom electrode can be substantially improved.