Vertically Integrated Micro-Bolometer Using SiGe Sensing Layer
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Solution Overview
Problem
Current micro-bolometer manufacturing processes face challenges with vanadium oxide, which has low resistivity but difficult process control and incompatibility with semiconductor processes, and polysilicon, which has higher resistivity and requires high temperatures that can damage integrated circuit elements.
Innovation Solution
A vertically integrated micro-bolometer is developed using a silicon germanium alloy (SiGe) or silicon carbide (SiC) sensing layer, compatible with semiconductor manufacturing processes, and a low-temperature wafer metal bonding method to integrate the infrared sensing film with the integrated circuit chip, preventing damage to circuit elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vanadium oxide is used as sensing material, then resistivity is reduced, but manufacturing process control becomes difficult and compatibility with semiconductor manufacturing process is lost
Solution Approach 1:
The patent changes the material parameter from vanadium oxide to polysilicon, which has different electrical properties. This parameter change resolves the contradiction by selecting a material that balances resistivity requirements with manufacturability and process compatibility, allowing the sensing layer to be produced using standard semiconductor fabrication processes while maintaining acceptable electrical characteristics for infrared detection
Solution Approach 2:
The patent employs a composite structure consisting of multiple layers including the polysilicon sensing layer, absorbing layers, and supporting substrate. This composite approach allows optimization of each layer's properties independently - the polysilicon layer provides process compatibility while the overall composite structure achieves the desired electrical and thermal characteristics for infrared sensing
2Ease of manufacture
If polysilicon is used to manufacture sensing layer, then manufacturing process compatibility is improved, but resistivity increases and measurement sensitivity is reduced
Solution Approach 1:
The patent optimizes the polysilicon material parameters including doping concentration, layer thickness, and crystalline structure to reduce resistivity. By carefully controlling these parameters during fabrication, the sensing layer achieves lower resistivity values that improve measurement sensitivity while maintaining the advantages of polysilicon process compatibility
Solution Approach 2:
The patent applies different processing conditions to different regions or aspects of the polysilicon sensing layer. For example, selective doping profiles or varying deposition parameters in different zones of the layer allow optimization of local electrical properties to enhance overall sensitivity while maintaining global process compatibility
3Ease of manufacture
If high process temperature is used for manufacturing infrared sensing layer by polysilicon, then sensing layer formation is achieved, but circuit elements in integrated circuit chip are damaged
Solution Approach 1:
The patent separates the manufacturing process into distinct stages: the infrared sensing layer is fabricated on a separate supporting substrate using high-temperature polysilicon deposition, then the completed sensing layer assembly is bonded to the integrated circuit chip at lower temperatures. This segmentation allows the high-temperature step to occur without exposing the temperature-sensitive circuit elements to damaging conditions
Solution Approach 2:
The patent introduces an intermediary supporting substrate that serves as a temporary platform for fabricating the infrared sensing layer. This intermediary allows high-temperature processing to be performed on the sensing layer without directly heating the integrated circuit chip, as the sensing layer and chip are processed separately and then combined through low-temperature bonding
4Ease of manufacture
If infrared sensing layer is integrated with integrated circuit chip by current semiconductor manufacturing process, then integration is achieved, but manufacturing yield is reduced and measurement sensitivity is reduced
Solution Approach 1:
The patent divides the integration process into modular stages where the infrared sensing layer is completely fabricated and tested as a separate unit on its supporting substrate, then bonded as a complete module to the integrated circuit chip. This segmentation isolates potential failure modes, allows independent optimization of each subsystem, and simplifies quality control, thereby improving overall manufacturing yield
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 improves measurement sensitivity and reduces production costs by using low-resistivity materials and a low-temperature bonding process, making the micro-bolometer suitable for applications like smartphones and smartwatches.
Implementation Method 1
a metal bonding layer connects the dielectric layer and the bottom absorbing layer so that the infrared sensing film is vertically integrated on the integrated circuit chip
Data Source
AI summary
A vertically integrated micro-bolometer includes an integrated circuit chip, an infrared sensing film, and a metal bonding layer. The integrated circuit chip includes a silicon substrate, a circuit element, and a dielectric layer disposed on the silicon substrate. The infrared sensing film includes a top absorbing layer, a sensing layer, and a bottom absorbing layer. The sensing layer is disposed between the top absorbing layer and the bottom absorbing layer. Materials of the top absorbing layer, the sensing layer, and the bottom absorbing layer are materials compatible with a semiconductor manufacturing process. The metal bonding layer connects the dielectric layer on the silicon substrate in the integrated circuit chip and the bottom absorbing layer of the infrared sensing film to form a vertically integrated micro-bolometer. In one embodiment, the infrared sensing film is divided into a central sensing film, a surrounding sensing film, and a plurality of connecting portions by a plurality of slots. The surrounding sensing film surrounds the central sensing film. Each of the connecting portions connects the surrounding sensing film and the central sensing film. A central distance from the bottom absorbing layer of the central sensing film to the silicon substrate is substantially equal to a surrounding distance from the bottom absorbing layer of the surrounding sensing film to the silicon substrate.