Titanium Nitride Structural Support for MEMS Bolometer Fabrication
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Solution Overview
Problem
The use of alumina as a structural support and seed layer in MEMS bolometer fabrication is challenging due to its insulating nature, requiring slow and damaging etching processes, which decreases yield and can result in non-uniformity and residual material affecting electrical contact.
Innovation Solution
Titanium nitride (TiN) is used as both a structural support and functional layer, replacing alumina, allowing for faster patterning and electrical connectivity, and potentially enhancing the bolometer signal by acting as an active component in addition to structural support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If alumina is used as the structural support and seed layer, then structural strength and seed layer quality are improved, but patterning speed and manufacturing yield deteriorate
Solution Approach 1:
The patent changes the material parameter from alumina (insulator) to titanium nitride (conductor), which fundamentally alters the patterning approach. This material substitution enables faster etching rates while maintaining structural strength, directly resolving the contradiction between structural integrity and patterning speed.
Solution Approach 2:
The patent employs titanium nitride as a composite material that simultaneously provides structural support, electrical conductivity, and etchability. This multi-functional material replaces the separate structural layer and seed layer, improving both strength and manufacturing efficiency.
2Stability of the object's composition
If alumina is used as the structural support, then structural integrity is improved, but fabrication yield and process duration deteriorate
Solution Approach 1:
Changing the material from alumina to titanium nitride modifies key parameters including electrical conductivity, etch rate, and thermal properties. This enables shorter processing times and reduced damage to photoresist masks, thereby improving fabrication yield while maintaining structural integrity.
3Strength
If alumina is used as the structural support, then mechanical strength is improved, but electrical connectivity and manufacturing complexity deteriorate
Solution Approach 1:
Titanium nitride serves multiple functions simultaneously: it provides structural support like alumina, but also offers electrical conductivity to eliminate the need for separate contact holes, and acts as a seed layer for platinum deposition. This multi-functionality reduces manufacturing complexity while maintaining mechanical strength.
Solution Approach 2:
The patent merges the structural support function and the electrical connectivity function into a single titanium nitride layer, eliminating the need for separate insulating layers and contact hole etching steps. This consolidation simplifies the overall manufacturing process.
4Stability of the object's composition
If alumina is used as the structural support, then structural stability is improved, but process time and photoresist damage deteriorate
Solution Approach 1:
The material substitution from alumina to titanium nitride changes the etch rate parameter dramatically, enabling faster patterning processes. This reduces the time the photoresist mask is exposed to damaging conditions, minimizing mask degradation and reducing overall process time while maintaining structural stability.
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 use of TiN simplifies the fabrication process, increases yield, and enhances the bolometer's signal generation by providing electrical connectivity and thermal isolation, while maintaining structural integrity and IR absorption capabilities.
Implementation Method 1
The use of TiN simplifies the fabrication process, increases yield, and enhances the bolometer's signal generation by providing electrical connectivity and thermal isolation
Implementation Method 2
In operation, infrared radiation incident upon the bolometer will be absorbed by the absorber element of the bolometer
Data Source
AI summary
A method for fabricating a semiconductor device includes patterning a sacrificial layer on a substrate to define a bolometer, with trenches being formed in the sacrificial layer to define anchors for the bolometer, the trenches extending through the sacrificial layer and exposing conductive elements at the bottom of the trenches. A thin titanium nitride layer is then deposited on the sacrificial layer and within the trenches. The titanium nitride layer is configured to form a structural support for the bolometer and to provide an electrical connection to the conductive elements on the substrate.