Direct Bonding Getter Placement in Thermal Detector Fabrication
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Solution Overview
Problem
Existing methods for fabricating electromagnetic radiation detection devices require protecting getter materials from degradation during wet chemical etching, which complicates the process and may affect the mechanical strength of the device, especially when adding optical components like filters.
Innovation Solution
A method involving the formation of a first stack with thermal detectors and a thin encapsulation layer, including a lateral vent, followed by chemical etching to remove sacrificial layers, and then assembling a second stack with a transparent sealing layer to directly bond and block the vent, placing the getter portion inside, thus avoiding the need for protective layers and simplifying the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer is applied to cover the getter material during wet chemical etching, then the getter material is protected from degradation, but the device complexity increases and mechanical strength may be affected
Solution Approach 1:
The getter material is positioned in the sealed cavity before the wet chemical etching step, and the encapsulation structure is sealed before etching. This preliminary arrangement eliminates the need for protective layers during etching, as the getter is already in its final protected position within the sealed cavity.
Solution Approach 2:
The getter material is extracted from the stack structure and placed inside the sealed cavity formed by the encapsulation layers. By removing the getter from the etching zone and placing it within the sealed cavity, the need for protective layers is eliminated while maintaining getter integrity.
2Reliability
If a protective layer is applied to cover the getter material, then degradation is prevented, but the mechanical strength of the stack is compromised
Solution Approach 1:
The encapsulation structure is assembled and sealed before the wet chemical etching step. The getter material is positioned within the sealed cavity in advance, allowing the stack to maintain its full mechanical strength without compromising protective layers.
Solution Approach 2:
The sealed encapsulation structure acts as an intermediary barrier that protects the getter material during etching. The encapsulation layers (first and second encapsulation layers) form a sealed cavity that shields the getter from etching agents while maintaining mechanical integrity.
3Reliability
If copper is used for bonding the encapsulation structure, then sealing is achieved, but the fabrication method is complicated due to material availability constraints
Solution Approach 1:
The bonding material is changed from copper to aluminum. This parameter change in material selection eliminates the availability constraints associated with copper while maintaining the sealing function. Aluminum is more compatible with standard semiconductor fabrication processes and is more readily available.
4Reliability
If the encapsulation structure is formed early in the process, then thermal detectors are protected, but the upper surface is not flat making optical component integration difficult
Solution Approach 1:
The encapsulation process is segmented into multiple stages: first encapsulation layer formation, thermal detector fabrication, second encapsulation layer formation, and final sealing. This segmentation allows the upper surface to be planarized in stages, achieving both detector protection and surface flatness for optical component integration.
Solution Approach 2:
The first encapsulation layer is formed preliminarily to protect thermal detectors during fabrication, then the upper surface is planarized, and finally the second encapsulation layer is added to achieve the desired flat surface for optical components while maintaining detector protection.
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 allows for the production of devices with a flat upper surface, enhances mechanical strength, and simplifies the fabrication by eliminating the need for protective layers, while ensuring the getter material is not degraded during etching, facilitating the integration of optical components.
Implementation Method 1
these layers being subsequently eliminated by wet chemical etching
Implementation Method 2
by bringing the thin sealing layer into contact with the upper part of the thin encapsulation layer and directly bonding it thereto
Implementation Method 3
a detection device comprising an array of thermal detectors encapsulated in a sealed cavity in which a getter material is also located
Data Source
AI summary
The invention relates to a method for fabricating a thermal detector (1), comprising the following steps:forming a first stack (10), comprising a thermal detector (20), a mineral sacrificial layer (15) and a thin encapsulation layer (16) having a lateral vent (17.1);forming a second stack (30), comprising a thin sealing layer (33) and a getter portion (34);eliminating the mineral sacrificial layer (15);assembling by direct bonding the thin sealing layer (33), brought into contact with the thin encapsulation layer (16) and blocking the lateral vent (17.1), the getter portion (34) being located in the lateral vent (17.1).