Microelectronic Encapsulation Using Sacrificial Material Extraction
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Solution Overview
Problem
Existing encapsulation methods for microelectronic components, such as MEMS and NEMS, face challenges including significant thickness, complexity, and potential damage to fragile microstructures due to the use of sacrificial materials, especially when dealing with components of significant thickness or complex topologies.
Innovation Solution
A method involving the production of a sacrificial material on a front face of a substrate, followed by etching from the rear face to create a cavity, allowing for the secure encapsulation of microelectronic components with a thin cover, facilitating the removal of the sacrificial material and reducing the risk of damage, suitable for components of varying thickness and complex geometries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cover is transferred onto the substrate to encapsulate microelectronic components, then hermetic sealing is achieved, but the thickness of the encapsulation structure becomes significant (approximately 750 μm)
Solution Approach 1:
The patent extracts the sacrificial material from the encapsulation structure after the cover is formed and attached to the substrate. By removing this intermediate material, the cover can be positioned closer to the substrate, reducing the overall thickness from approximately 750 μm to less than 200 μm while maintaining hermetic sealing through the eutectic bond between the cover and substrate
Solution Approach 2:
The sacrificial material is deposited on the substrate before the cover is formed and attached. This preliminary placement allows the cover to be precisely positioned and hermetically sealed to the substrate, and then the sacrificial material is removed through etch access holes, achieving both hermetic sealing and reduced thickness
2Length of stationary object
If sacrificial material is dispensed directly onto mobile microstructures for thin layer encapsulation, then encapsulation thickness is reduced, but the microstructures may be deteriorated
Solution Approach 1:
The patent segments the sacrificial material into two distinct functional layers: a first layer that serves as the sacrificial material for cavity formation, and a second layer that acts as a protective layer during the etching process. This segmentation allows the sacrificial material to be removed while protecting the mobile microstructures from damage by preventing direct contact between the etchant and the sensitive structures
Solution Approach 2:
The protective layer acts as an intermediary between the etchant and the mobile microstructures. It is deposited over the sacrificial material and mobile structures, allowing the etchant to remove the sacrificial material while the protective layer prevents deterioration of the microstructures. The protective layer is later removed to complete the encapsulation process
3Length of stationary object
If the cover thickness is reduced to less than 200 μm, then the encapsulation structure becomes thinner, but mechanical strength is compromised
Solution Approach 1:
The patent changes the material composition and structural parameters of the encapsulation system. By using a eutectic sealing mechanism and optimizing the bond between the cover and substrate, the system achieves sufficient mechanical strength with a cover thickness of less than 200 μm, overcoming the traditional limitation that required thicker covers for structural integrity
4Manufacturing precision
If photolithography is used to structure sacrificial material, then encapsulation precision is improved, but the process complexity increases
Solution Approach 1:
The patent employs photolithography to perform multiple functions: structuring the sacrificial material, defining the cavity geometry, and creating alignment features for the cover. This multi-functional use of photolithography achieves high encapsulation precision while minimizing the number of separate process steps required
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 the production of a microelectronic encapsulation structure with a small footprint, minimizing the risk of component deterioration and facilitating the deposition and removal of sacrificial materials, making it suitable for components of significant thickness and complex topologies, while maintaining the integrity of the cover and allowing for hermetic sealing.
Implementation Method 1
depositing a first layer of sacrificial material on the protective layer
Implementation Method 2
etching the first layer of sacrificial material from a rear face of the microelectronic component
Implementation Method 3
securing the cover to the microelectronic component, hermetically sealing the cavity
Data Source
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AI summary
A method for encapsulating a microelectronic component (100) comprising the implementation of the following steps: - making a portion of sacrificial material on a front face of a first substrate in which the component is suitable to be made, then - making a cover (116) encapsulating the portion of sacrificial material, then - making the component by etching the first substrate from its rear face such that a part of the component is positioned facing the portion of sacrificial material and the portion of sacrificial material is accessible from a rear face (127) of the component, then - removing the portion of sacrificial material by etching from the rear face of the component, then - bonding the rear face of the component with a second substrate (128).