Hermetic Microelectronic Packaging via Fusible Plug
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Solution Overview
Problem
Current microelectronic device packaging methods, such as cap bonding and thin film capping, face challenges in achieving hermetic sealing with controlled atmospheres, particularly at pressures above 100 mbar, due to high temperature requirements, contamination issues, and limitations in managing cavity atmospheres independently.
Innovation Solution
A method involving the creation of a dedicated hole in the cap layer using a fusible material that is reflowed to hermetically seal the cavity, allowing independent atmosphere management without damaging the cap or generating particles, and avoiding the use of lasers or high-temperature processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cap bonding is used to create hermetic cavity, then hermetic sealing is achieved, but high temperature bonding process damages temperature-sensitive microelectronic devices
Solution Approach 1:
The process is divided into separate stages: first forming the cavity structure at low temperature, then creating the hermetic seal through a dedicated hole at a later stage. This segmentation allows temperature-sensitive devices to be packaged without exposing them to high bonding temperatures, while still achieving hermetic sealing when needed.
Solution Approach 2:
The cavity structure is formed in advance using thin film deposition and sacrificial layer release at low temperatures compatible with microelectronic devices. The hermetic sealing action is deferred until after the device is in place, allowing preliminary preparation without thermal damage.
2Adaptability or versatility
If laser is used to create dedicated hole for atmosphere management, then atmosphere control is enabled, but laser generates particles that damage the microelectronic device
Solution Approach 1:
The laser-based hole creation is replaced with a mechanical/electrical electrochemical deposition process. A conductive plug is deposited through the dedicated hole using electrochemical methods, providing hermetic sealing without the harmful particles generated by laser ablation, while still enabling atmosphere management functionality.
3Reliability
If PVD or CVD deposition is used to close release holes, then hermetic sealing is achieved, but deposition gases contaminate the cavity atmosphere
Solution Approach 1:
The hermetic sealing function is extracted from the release hole closure process. Instead of using PVD/CVD deposition through release holes (which introduces contamination gases), a separate dedicated hole is created and sealed with electrochemical deposition, extracting the sealing function to a process that does not contaminate the cavity atmosphere.
4Reliability
If PSG layer is used to close release holes, then hermetic sealing is achieved, but high temperature curing damages temperature-sensitive devices
Solution Approach 1:
The thermal curing process of PSG is replaced with electrochemical deposition of a conductive plug. This substitution eliminates the need for high temperature curing (900°C), using instead a low-temperature electrochemical process that is compatible with temperature-sensitive microelectronic devices while achieving hermetic sealing.
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
Enables hermetic sealing with controlled atmospheres between 10^-6 and 100 mbar, reducing contamination and maintaining device reliability while avoiding the drawbacks of existing methods, such as high temperature curing and laser-induced damage.
Implementation Method 1
reflowing the portion of fuse material with a controlled atmosphere, forming a bump of fuse material which hermetically plugs said dedicated hole
Implementation Method 2
a portion of which is made by an electrochemical deposition
Data Source
Figure 1A~1C
Figure 1D~1F
Figure 1G~1I
AI summary
Method for packaging a microelectronic device (100) in an hermetically sealed cavity (110) and managing an atmosphere of the cavity with a dedicated hole (130), comprising: - making said cavity between a support (102) and a cap layer (106) such that a sacrificial material and the device are arranged in the cavity; - removing the sacrificial material through at least one release hole (108), and hermetically sealing the release hole; - making a portion of wettable material (128) on the cap layer, around a blind hole or a part of said outside surface corresponding to a location of said dedicated hole; - making a portion of fuse material (126) on the portion of wettable material; - making the dedicated hole by etching the cap layer; - reflowing the portion of fuse material with a controlled atmosphere, forming a bump of fuse material (132) which hermetically plugs said dedicated hole.