Buried Chamber Microfluidic MEMS Device Monolithic Silicon Fabrication
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Solution Overview
Problem
Current microfluidic MEMS devices, such as fluid ejection devices, face challenges in manufacturing due to the need for high accuracy alignment of multiple wafers, which is costly and prone to yield problems, and the materials used may not ensure repeatability or compatibility with all liquids, especially at extreme temperatures.
Innovation Solution
A microfluidic device with a buried cavity and a membrane layer comprising non-permeable and permeable polycrystalline portions, where the membrane is between the substrate and the actuator, and a cap over the actuator, with through openings in fluidic communication, is manufactured using a process that involves forming a sacrificial layer, a carrying layer, and a permeable layer to create a buried cavity, which is then sealed and etched to form a monolithic body using only two wafers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple wafers are coupled with high accuracy alignment, then device functionality is achieved, but manufacturing cost increases and yield problems occur
Solution Approach 1:
The patent combines multiple functional layers (nozzle layer, chamber layer, distribution layer) into a single monolithic silicon wafer structure. The buried cavity integrates the fluid containment chamber and actuator chamber that were previously separate, eliminating the need for multiple wafer bonding steps and high-precision alignment while reducing manufacturing complexity and cost.
Solution Approach 2:
The patent segments the single wafer into distinct functional regions: a nozzle portion with ejection channels, a chamber portion with the buried cavity, and a distribution portion with supply channels. This segmentation allows each region to be optimized independently during processing while maintaining monolithic integration, avoiding the need for multiple separate wafers.
2Reliability
If multiple wafers are coupled, then device functionality is achieved, but manufacturing complexity and yield problems increase
Solution Approach 1:
The patent merges multiple discrete components into a single monolithic structure where the nozzle portion, chamber portion, and distribution portion are all formed in one silicon wafer. The buried cavity serves both as the fluid containment chamber and actuator chamber, eliminating the need for multiple wafer bonding operations and reducing manufacturing process complexity while maintaining full device functionality.
3Ease of manufacture
If polymeric material is used for nozzle plate, then manufacturing is simplified, but repeatability and uniformity are compromised
Solution Approach 1:
The patent uses a homogeneous monocrystalline silicon material for the entire device structure, including the nozzle portion, chamber portion, and distribution portion. This eliminates the heterogeneity introduced by combining silicon wafers with polymeric nozzle plates, ensuring uniform material properties, thermal conductivity, and chemical compatibility while maintaining manufacturing simplicity through single-wafer processing.
4Ease of manufacture
If polymeric material is used for nozzle plate, then manufacturing is simplified, but temperature compatibility is reduced
Solution Approach 1:
The patent employs homogeneous silicon material throughout the device structure, which possesses superior thermal stability and compatibility with extreme temperatures compared to polymeric materials. The monolithic silicon construction eliminates the thermal expansion mismatch and degradation issues associated with polymer-silicon composites, enabling operation in high-temperature environments while maintaining manufacturing simplicity.
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 simplifies the manufacturing process, reduces costs, and improves the structural integrity and compatibility of the device with various liquids, while maintaining high yield and alignment precision.
Implementation Method 1
the piezoelectric actuator 15 is controlled through the electrodes 21, 22 (suitably biased) in such a way as to generate a deflection of the membrane 7 towards the inside of the fluid containment chamber 11 and a movement of the fluid towards the nozzle 10
Data Source
AI summary
Process for manufacturing a microfluidic device, wherein a sacrificial layer is formed on a semiconductor substrate; a carrying layer is formed on the sacrificial layer; the carrying layer is selectively removed to form at least one release opening extending through the carrying layer; a permeable layer of a permeable semiconductor material is formed in the at least one release opening; the sacrificial layer is selectively removed through the permeable layer to form a fluidic chamber; the at least one release opening is filled with non-permeable semiconductor filling material, forming a monolithic body having a membrane region; an actuator element is formed on the membrane region and a cap element is attached to the monolithic body and surrounds the actuator element.