Implantable Optical Sensor Hermetic Cap for Wafer-Scale Packaging
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Solution Overview
Problem
Existing optical assemblies, particularly those intended for implantable use, face challenges in protecting electronic and optoelectronic components from harsh environments, such as body fluids, while maintaining optical and electrical functionality, and current manufacturing methods are costly and not suitable for wafer-scale production.
Innovation Solution
An optical assembly with a hermetically sealed cover cap and integrated optical and electrical feedthroughs, manufactured using wafer-scale processes, ensures that electronic components are sealed within a cavity, allowing optical and electrical communication without exposure to fluids, and uses wafer-to-wafer bonding for sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a titanium box is used to protect optical assemblies, then hermetic protection is achieved, but the approach is not suitable for wafer scale production and each device needs to be processed separately, making it costly
Solution Approach 1:
The device is segmented into distinct functional layers: an optical layer with optical interaction areas exposed to fluid, and a sealed layer with hermetically sealed cavities containing electronic components. This segmentation allows different parts to be optimized for their specific functions while enabling wafer-scale fabrication through standard semiconductor processes.
Solution Approach 2:
The semiconductor substrate serves multiple functions: it provides the structural platform for optical components, acts as a barrier layer for hermetic sealing, and enables wafer-scale production through compatibility with standard semiconductor manufacturing processes. This multi-functionality eliminates the need for separate titanium housing and enables scalable production.
2Ease of manufacture
If feedthroughs are made through wafer scale cap, then manufacturing is simplified, but these feedthroughs are weak points especially when regarded in relation to a desired long life time
Solution Approach 1:
The design extracts the need for traditional feedthroughs by using a layered architecture where the optical layer is exposed to fluid and the sealed layer contains electronics. The substrate itself acts as the hermetic barrier, eliminating the need for additional feedthrough structures that would compromise long-term reliability.
Solution Approach 2:
The device uses composite material structures with the substrate serving as both structural support and hermetic barrier. The combination of optical materials in the optical layer and sealed cavity structures in the sealed layer creates a composite system that maintains hermeticity while enabling wafer-scale production without traditional feedthroughs.
3Ease of operation
If the cover cap protrudes to communicate with electronic components, then electrical connection is achieved, but the electronic components are exposed to fluid contact
Solution Approach 1:
The sealed cavity containing electronic components is nested within the substrate structure, with the substrate itself serving as the hermetic enclosure. This nested architecture allows electrical connections to be made through the substrate using standard semiconductor interconnection techniques while the substrate barrier prevents fluid contact with electronics.
4Ease of manufacture
If parylene-c coating is used for hermetic protection, then coating process is simple, but it is not possible to test a device for a successful hermetic packaging
Solution Approach 1:
The hermetic sealing structure is built into the device architecture during fabrication through the sealed layer with hermetically sealed cavities, rather than applying a coating afterward. This preliminary action during manufacturing allows for proper hermetic sealing that can be verified through standard semiconductor testing methods, eliminating the limitations of post-fabrication coating approaches.
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 provides a reliable, cost-effective, and efficiently manufactured optical assembly that maintains functionality in harsh environments by shielding components from fluids and enabling long-term operation without the need for protruding cover caps or metal rims, suitable for applications like sensing body fluids and chemical processes.
Implementation Method 1
sealing the cover cap to the substrate by wafer-to-wafer bonding technology
Implementation Method 2
at least one optical feedthrough extending from the hermetically sealed cavity to the optical interaction area
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
An implantable optical sensor comprises a photonic integrated circuit comprising a substrate (2) and an optical microstructure (3) integrated with the substrate (2). The optical microstructure is positioned to form an exposed optical interaction area (4) on a part of a surface (5) of the substrate (2). A cover cap (6) is sealed onto a part of the substrate (2) adjacent to the optical interaction area (4) and by wafer-to-wafer bonding technology or another wafer-level hermetic packaging technique. At least one active component (8) is positioned in a sealed cavity (9) which is formed between the surface (5) and the cover cap (6). The substrate (2) comprises at least one optical feedthrough (10), which is an embedded waveguide extending from the sealed cavity (9) to the optical interaction area (4).