Piezoelectric Resonator Fabrication With Sacrificial Oxide Alignment
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Solution Overview
Problem
Existing methods for manufacturing piezoelectric MEMS resonators are costly and result in variations in layer thickness and structural variations among components, affecting electromechanical efficiency and conductivity.
Innovation Solution
A cost-effective MEMS process is developed, ensuring maximum overlap of the piezoelectric layer with electrodes, using a highly-doped silicon functional layer with a sacrificial oxide layer for precise layer deposition and ion beam trimming, along with specific metallization layers like gold and silicide layers to maintain conductivity and minimize mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional manufacturing methods are used for piezoelectric MEMS resonators, then the process is costly and results in variations in layer thickness and structural variations among components, but implementing a cost-effective highly parallel MEMS process with maximum overlap of piezoelectric layer with electrodes and high electrical conductivity of connection elements is achieved
Solution Approach 1:
A sacrificial oxide layer is deposited on the silicon functional layer before depositing the piezoelectric layer. This sacrificial layer serves as a preliminary structure that defines the precise location where the piezoelectric layer should be formed, ensuring uniform thickness and position. The sacrificial oxide layer is later removed to create the final structure with the piezoelectric layer positioned exactly where needed, achieving both cost-effectiveness through parallel processing and high manufacturing precision.
Solution Approach 2:
The sacrificial oxide layer acts as an intermediary element during the manufacturing process. It temporarily occupies the space where the piezoelectric layer will eventually be formed, allowing for precise control of the piezoelectric layer's position and thickness. After the piezoelectric layer is deposited with maximum overlap with electrodes, the sacrificial oxide is removed, leaving the desired final structure with high precision and uniformity across all components.
2Reliability
If soft metallization layers are added to ensure high electrical conductivity of connection elements, then electrical conductivity is improved, but stiffening or mechanical tensions with pronounced temperature dependence may be introduced
Solution Approach 1:
Soft metallization layers are applied selectively only in specific areas where high electrical conductivity is required, such as connection elements and supply lines, rather than across the entire resonator structure. This localized application ensures high electrical conductivity where needed while avoiding the introduction of mechanical tensions and stiffening in the oscillating structure, maintaining thermal stability of the resonator's mechanical properties.
Solution Approach 2:
The patent uses a sacrificial oxide layer that is temporarily present during manufacturing and then removed. This disposable sacrificial structure enables precise positioning of the piezoelectric layer and formation of clean interfaces without leaving residual mechanical stresses. The temporary nature of the sacrificial layer allows it to serve its function during fabrication and then be completely removed, avoiding any long-term mechanical tension issues.
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 process achieves high electromechanical efficiency with minimal layer thickness variations and structural uniformity, ensuring reliable electrical conductivity and stability under thermal stresses.
Implementation Method 1
The actuator which generates the conversion of an electrical signal into a mechanical oscillation is typically a piezoelectric layer here, which is situated as part of a sandwich structure between two electrodes and elastically deforms under the action of the field generated by the electrodes
Implementation Method 2
using a highly-doped silicon functional layer with a sacrificial oxide layer for precise layer deposition and ion beam trimming
Data Source
AI summary
A method for manufacturing a piezoelectric resonator. The method includes: depositing a piezoelectric layer and forming a recess in a lateral area in such a way that a silicon functional layer is exposed inside the recess, forming a silicide layer on a surface of the silicon functional layer exposed inside the recess, forming a diffusion barrier layer on the silicide layer, depositing and structuring a first and second metallization layer in such a way that a supply line and two connection elements are formed, forming the oscillating structure by structuring the silicon functional layer, the silicon functional layer of the oscillating structure being able to be electrically contacted via the first connection element and forming a lower electrode of the resonator, the first metallization layer of the oscillating structure being able to be electrically contacted via the second connection element and forming an upper electrode of the resonator.