Humidity Sensor Interdigital Electrode Single-Phase Etching
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Solution Overview
Problem
Existing humidity sensors face manufacturing inefficiencies due to two-phase production processes, leading to thermal stresses and parasitic capacitances caused by imperfect etching of passivation layers, which impair sensor performance.
Innovation Solution
A humidity sensor with a silicon base plate and interlaced metallic electrodes, where the passivation layer is etched to extend into the dielectric layer, reducing parasitic capacitances and allowing a single manufacturing phase, and an oxynitride or polyimide layer is used for protection and detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two-phase manufacturing process is used, then sensor can be produced with protective layers, but thermal stresses appear and manufacturing complexity increases
Solution Approach 1:
The patent merges the two separate manufacturing phases into a single integrated phase. The interdigital comb is etched first, then the passivation layer is deposited and etched in the same manufacturing cycle without removing the comb structure. This eliminates the need for a second phase, reducing thermal cycles and manufacturing complexity while maintaining sensor performance.
Solution Approach 2:
The patent performs preliminary action by depositing the passivation layer immediately after comb formation without removing the comb. The passivation layer is then etched through the comb arms in the same manufacturing phase, preventing subsequent corrosion and eliminating the need for a second manufacturing phase.
2Reliability
If passivation layer is etched in second phase, then protective coverage is achieved, but parasitic capacitances appear due to imperfect etching
Solution Approach 1:
The passivation layer is deposited and etched in the same manufacturing phase as the comb formation. This preliminary action ensures that the passivation layer is properly positioned and etched before any subsequent processing, eliminating the need for a second phase and reducing parasitic capacitances from imperfect etching.
3Ease of manufacture
If multiple thermal cycles are applied, then manufacturing steps can be completed, but thermal stresses impair sensor performance
Solution Approach 1:
The patent combines multiple manufacturing steps that would normally require separate thermal cycles into a single continuous process. The comb etching, passivation layer deposition, and passivation layer etching are all performed in one manufacturing phase, eliminating supplementary thermal cycles and the associated thermal stresses.
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 reduces thermal stresses and parasitic capacitances, enhancing sensor sensitivity and efficiency by integrating all manufacturing steps into a single phase and using protective layers to minimize corrosion and improve detection accuracy.
Implementation Method 1
a metallic layer (20) are arranged, said metallic layer being etched in order to form two electrodes, each comprising one armature provided with a multitude of arms, these armatures being mounted so that the arms of each armature are interlaced in order to have arms placed opposite each other
Implementation Method 2
said passivation layer is etched so that the gaps between the arms placed opposite each other are hollowed out, extending into the dielectric layer on which the metallic layer is deposited
Implementation Method 3
an anticorrosion protective layer which protects the metallic layer from corrosion
Implementation Method 4
a polyimide layer which serves as detection dielectric
Data Source
AI summary
The present invention relates to a humidity sensor comprising a silicon base plate on which at least a plurality of dielectric layers, each provided with a metallic zone, and a metallic layer are arranged, said metallic layer being etched in order to form two electrodes, each comprising one armature provided with a multitude of arms, these armatures being mounted so that the arms of each armature are interlaced in order to have arms placed opposite each other and separated by gaps.