Monolithic Humidity Sensor With Passivation Barriers
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Solution Overview
Problem
Integrated circuit (IC) humidity sensors are susceptible to degradation due to moisture ingress, which affects their reliability and accuracy in monitoring ambient humidity levels.
Innovation Solution
The development of monolithic humidity sensor devices with a primary passivation barrier, conductive vias, a capacitor with metal fingers, and a secondary passivation barrier, along with a hygroscopic material layer, which limits moisture exposure to the circuitry and enhances signal responsiveness to humidity changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If IC circuitry is exposed to moisture for humidity sensing, then humidity detection capability is achieved, but circuitry degradation occurs
Solution Approach 1:
The device is segmented into distinct functional regions: a first region containing the capacitive sensor structure exposed to moisture for humidity detection, and a second region containing the IC circuitry protected from moisture by the passivation barrier. This spatial segmentation allows the sensor portion to interact with moisture while isolating the circuitry from harmful exposure.
Solution Approach 2:
A passivation barrier layer acts as an intermediary between the moisture environment and the IC circuitry. This barrier selectively permits the capacitive sensor structure to detect humidity while preventing moisture from reaching and degrading the underlying circuitry components.
2Reliability
If passivation barrier is added to protect circuitry, then reliability is improved, but device complexity increases
Solution Approach 1:
The passivation barrier layer is merged with the interlayer dielectric structure of the IC fabrication process. The barrier is integrated into the existing multi-layer dielectric stack that already forms part of the capacitive sensor structure, combining protection functionality with the sensor architecture rather than adding a separate protective component.
Solution Approach 2:
The passivation barrier layer serves multiple functions simultaneously: it acts as a moisture barrier to protect the IC circuitry, serves as an interlayer dielectric for the capacitive structure, and provides mechanical support. This multi-functionality reduces the need for additional separate protective layers.
3Measurement precision
If capacitor is formed with metal fingers for sensing, then measurement precision is improved, but manufacturing complexity increases
Solution Approach 1:
The capacitive sensing mechanism replaces mechanical humidity sensing methods with an electrical field-based measurement system. The interdigitated metal fingers create an electric field that interacts with moisture through dielectric constant changes, enabling precise humidity measurement without mechanical moving parts.
Solution Approach 2:
The capacitive sensor utilizes thin film metal finger structures formed through standard semiconductor deposition processes. These thin film structures provide the necessary capacitive sensing capability while being compatible with IC fabrication methods, avoiding the need for complex three-dimensional metal structures.
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 effectively isolates the circuitry from moisture, reducing the risk of degradation and improving the accuracy and reliability of humidity sensing while maintaining a compact sensor size.
Implementation Method 1
A hygroscopic material layer is then formed over the secondary passivation barrier, wherein the capacitor is operable to exhibit a capacitance value responsive to moisture present in the hygroscopic material layer
Implementation Method 2
A primary passivation barrier is formed over the circuitry with conductive vias therethrough
Data Source
AI summary
Monolithic humidity sensor devices, and methods of manufacture. The devices include circuitry on or over a silicon substrate. A primary passivation barrier is formed over the circuitry with conductive vias therethrough; a capacitor, comprising metal fingers with spaces therebetween, is formed above said primary passivation barrier and electrically coupled by the conductive vias to the circuitry. A secondary passivation barrier is formed over the capacitor. A hygroscopic material layer is formed over the secondary passivation barrier, wherein the capacitor is operable to exhibit a capacitance value responsive to moisture present in the hygroscopic material layer and the circuitry is operable to generate a signal responsive to said capacitance value.