MEMS Acoustic Resonator Passivation for Liquid-Phase Biosensing
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Solution Overview
Problem
Existing bulk acoustic wave resonators face challenges in stable operation in liquid environments due to corrosion of reactive metal electrodes and compatibility issues with functionalization materials, leading to degraded performance.
Innovation Solution
A micro-electromechanical system (MEMS) resonator device with a passivation structure comprising a hermeticity layer with low water vapor transmission and an interface layer, enabling the deposition of a self-assembled monolayer and functionalization material, which protects the electrodes from corrosive liquids while allowing proper chemical binding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reactive metal electrodes are used in bulk acoustic wave resonators, then electrical conductivity and acoustic performance are improved, but corrosion resistance in liquid environments deteriorates
Solution Approach 1:
A hermeticity layer is introduced as an intermediary between the reactive metal electrodes and the liquid environment. This layer acts as a protective barrier that prevents direct contact between the corrosive liquid and the metal electrodes, thereby maintaining both the electrical conductivity of the electrodes and their corrosion resistance in liquid environments.
Solution Approach 2:
A thin film hermeticity layer is deposited over the metal electrodes to provide protection against corrosion. This thin film structure maintains the electrical functionality of the electrodes while providing a flexible barrier against the liquid environment, enabling stable operation of the resonator in liquid.
2Object-affected harmful factors
If hermeticity layer is deposited over electrodes, then corrosion resistance is improved, but chemical binding capability deteriorates
Solution Approach 1:
The passivation structure is segmented into multiple functional layers: a hermeticity layer for corrosion protection and an interface layer for chemical binding. This segmentation allows each layer to perform its specific function independently - the hermeticity layer protects the electrodes while the interface layer enables functionalization material binding.
Solution Approach 2:
Different regions of the passivation structure are given different properties. The hermeticity layer provides corrosion resistance, while the interface layer provides chemical reactivity for binding functionalization materials. This local differentiation of properties allows the structure to simultaneously achieve both protection and functionality.
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 solution enables stable operation of bulk acoustic wave resonators in liquid environments by preventing corrosion and ensuring effective chemical binding, thereby maintaining device performance and sensitivity for biosensing applications.
Implementation Method 1
a hermeticity layer with low water vapor transmission rate
Implementation Method 2
enabling the deposition of a self-assembled monolayer
Implementation Method 3
functionalization material capable of binding to the self-assembled monolayer
Data Source
Figure 1~2A
Figure 2B~2D
Figure 2E~3B
AI summary
A micro-electrical-mechanical system (MEMS) resonator device includes a top side electrode overlaid with a low water permeability hermeticity layer and an interface layer including a material (e.g., gold or a hydroxylated oxide surface) suitable for receiving a self-assembled monolayer (SAM) that may be functionalized with a functionalization (e.g., specific binding) material, with the foregoing layers being designed to have insubstantial impact on sensor performance. Atomic layer deposition may be used for deposition of the hermeticity and/or interface layers. The hermeticity layer protects the electrode material from attack in corrosive liquid environments, and the interface layer facilitates proper chemical binding of the SAM. Sensors and microfluidic devices incorporating MEMS resonator devices are also provided.