Lateral Control Electrode Humidity Sensor Design
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Solution Overview
Problem
Existing moisture sensors require additional manufacturing steps and material restrictions due to the need for porous metallization that adheres to the sensor and passivation layers, limiting material choices and increasing production costs.
Innovation Solution
The control electrode is positioned laterally or underneath the sensor layer, allowing for a non-porous material choice and direct atmospheric contact, with an insulation layer to reduce contamination sensitivity and enable capacitive charge detection, using a field effect transistor with a semiconductor substrate and polymethyl methacrylate sensor layer for enhanced sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a porous metallization is applied as control electrode to the sensor layer, then the control electrode can be adhered to the sensor layer and passivation layer, but the material selection is restricted and production cost increases
Solution Approach 1:
The patent introduces an intermediary layer (insulation layer or direct contact interface) between the control electrode and sensor layer that enables adhesion without requiring the control electrode material to be porous or specially adapted. This intermediary structure mediates the bonding requirement, allowing standard non-porous metallization materials to be used while maintaining secure attachment to the sensor layer and passivation layer.
2Strength
If a porous metallization is applied as control electrode, then adhesion is achieved, but only porous gas-permeable layers can be used
Solution Approach 1:
The patent employs an intermediary arrangement where the control electrode does not directly require porous structure for adhesion. The sensor layer itself serves as the gas-permeable pathway while the control electrode can be made from non-porous materials, thus eliminating the harmful restriction that only porous metallization layers could be used.
3Ease of manufacture
If control electrode covers the sensor layer, then manufacturing is simplified, but contamination sensitivity increases
Solution Approach 1:
The patent positions the control electrode in a different spatial dimension - laterally adjacent to or underneath the sensor layer rather than directly covering it. This dimensional repositioning maintains manufacturing simplicity while reducing the control electrode's exposure to atmospheric contamination, as it is either shielded by the sensor layer or positioned at the periphery where contamination accumulation is minimized.
4Speed
If sensor layer is in direct contact with atmosphere, then humidity response is quick, but contamination occurs
Solution Approach 1:
The patent positions the control electrode underneath or laterally adjacent to the sensor layer, creating a protective spatial arrangement. The sensor layer maintains direct atmospheric contact for quick humidity response, while the control electrode is positioned in a protected dimension where it is shielded from direct contamination exposure by the sensor layer itself.
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 design simplifies and cost-reduces sensor production, maintains high measurement sensitivity, and is less affected by contamination, while allowing for compact dimensions and quick humidity response.
Implementation Method 1
a moisture-permeable sensor layer 12 is arranged on the control electrode 7, the dielectric constant of which depends on the moisture
Implementation Method 2
The thickness of the insulation layer or the distance between the control electrode and the sensor layer is chosen so that the electric field generated by the control voltage has a capacitive effect through the insulation layer on the sensor layer
Implementation Method 3
A potential sensor, in particular a field effect transistor, is integrated into the substrate 2
Data Source
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AI summary
A humidity sensor on a substrate (2) comprises at least one potential sensor with a sensor area (5, 5') and at least one control electrode (7). The control electrode (7) is connected to a signal source configured such that a variable control voltage can be applied to the control electrode (7). A moisture-permeable sensor layer (12) is arranged on the sensor area (5, 5'), the dielectric constant of which depends on the humidity. The control electrode (7) is adjacent to the sensor layer (12) such that the potential sensor's signal depends on the control voltage and the humidity. The potential sensor is connected to an evaluation unit for determining the humidity based on the potential signal. The control electrode (7) is arranged laterally next to the sensor area (5) when viewed from the plane of the substrate (2) (Fig. 1).