Getter Pad Encapsulation for Wet-Etch-Protected Thermal Detectors
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Solution Overview
Problem
Existing devices for detecting electromagnetic radiation, such as infrared or terahertz radiation, face challenges in protecting the getter material during the removal of mineral sacrificial layers via wet chemical etch while maintaining a small footprint on the substrate.
Innovation Solution
A process involving the production of a getter pad with a protective segment of amorphous carbon and a getter segment, where the mineral sacrificial layer is partially removed to free the protective segment, followed by the removal of the protective segment to expose the getter segment, and finally sealing the vents to create a hermetic cavity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thin carbon-containing sacrificial layer is used to protect the getter material during wet chemical etch, then the getter material is protected from degradation, but the protection may be insufficient and the footprint of the encapsulating structure increases
Solution Approach 1:
The encapsulating structure is divided into multiple segments: a peripheral wall segment that rests on the substrate and encircles the thermal detectors, and an upper wall segment that rests on the mineral sacrificial layer. This segmentation allows the structure to provide adequate protection for the getter material while maintaining a compact footprint by utilizing vertical space rather than lateral expansion.
Solution Approach 2:
The solution transitions from a two-dimensional planar protection approach to a three-dimensional vertical structure. The upper wall extends vertically above the mineral sacrificial layer to cover the getter material, providing protection without increasing the lateral footprint on the substrate. This vertical dimensionality change resolves the contradiction between protection adequacy and footprint size.
2Ease of manufacture
If the mineral sacrificial layer is completely removed via wet chemical etch, then the encapsulating structure can be properly formed, but the getter material becomes exposed and vulnerable to degradation
Solution Approach 1:
The upper wall of the encapsulating structure is formed preliminarily before the complete removal of the mineral sacrificial layer. This preliminary action creates a protective enclosure that will shelter the getter material once the sacrificial layer is fully removed, ensuring the getter material's integrity is maintained throughout the manufacturing process.
Solution Approach 2:
The upper wall of the encapsulating structure serves as an intermediary protective element between the getter material and the wet chemical etchant. It allows the mineral sacrificial layer to be removed while preventing direct contact between the etchant and the getter material, thus resolving the contradiction between ease of manufacture and getter material integrity.
3Area of stationary object
If the encapsulating structure is designed with a small footprint, then the device integration is improved, but the protection of the getter material during etching becomes insufficient
Solution Approach 1:
The encapsulating structure utilizes the vertical dimension by extending the upper wall above the mineral sacrificial layer. This provides adequate coverage and protection for the getter material while maintaining a minimal lateral footprint on the substrate, effectively resolving the contradiction between compact integration and sufficient protection.
Solution Approach 2:
The encapsulating structure employs a composite design combining the peripheral wall (resting on substrate) and the upper wall (resting on mineral sacrificial layer). This composite structure achieves both small footprint and adequate protection by strategically positioning different structural elements in space.
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 process effectively protects the getter material from degradation during the etching process and maintains a small encapsulating structure footprint, enhancing the reliability and efficiency of the detection device.
Implementation Method 1
removal of the mineral sacrificial layer via a wet chemical etch
Implementation Method 2
subsequently removed via a specific dry chemical etch
Data Source
AI summary
A process for fabricating a detecting device includes producing a getter pad based on amorphous carbon resting on a mineral sacrificial layer that covers a thermal detector and producing a thin encapsulating layer that rests on the mineral sacrificial layer and that covers an upper face and sidewalls of the getter pad. The mineral sacrificial layer is removed via a first chemical etch, and a protective segment of the getter pad is removed via a second chemical etch.