Polymeric Membrane Adhesion via Silicon Dioxide Trenches
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Solution Overview
Problem
Chemical sensors with polymeric membranes face adhesion issues on silicon nitride surfaces, leading to poor reliability and shorter lifetimes, as these membranes do not adhere well and can leak, causing errors in ion-selective measurements.
Innovation Solution
The formation of adhesion trenches in the silicon nitride passivation layer to expose silicon dioxide, allowing for better adhesion of polymeric membranes using polyimide rings and adhesion promoters, ensuring full circumferential adhesion and preventing leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon nitride is used as the passivation layer, then the sensor can protect the silicon and conducting layers from solution, but the polymeric membrane does not adhere well to the surface
Solution Approach 1:
The passivation layer is segmented into two distinct layers: a silicon nitride layer for protection and a silicon dioxide layer for adhesion. This segmentation allows each layer to perform its specialized function - the silicon nitride provides chemical and mechanical protection while the silicon dioxide provides a high-adhesion surface for the polymeric membrane, thereby resolving the contradiction between protection and adhesion.
Solution Approach 2:
The silicon dioxide layer acts as an intermediary between the silicon nitride passivation layer and the polymeric membrane. It mediates the interaction by providing a surface that both the silicon nitride structure and the polymeric membrane can interface with effectively, enabling strong adhesion while maintaining the protective function of the underlying silicon nitride layer.
2Reliability
If silicon dioxide is used as the passivation layer, then the polymeric membrane adheres better, but it absorbs water and cannot protect electronics
Solution Approach 1:
The passivation structure is divided into functional segments where silicon dioxide provides adhesion and silicon nitride provides water barrier protection. This segmentation allows the system to benefit from the high adhesion of silicon dioxide without suffering from its water absorption drawback, as the silicon nitride layer prevents water from reaching the electronics.
Solution Approach 2:
The passivation system uses a composite structure of silicon nitride and silicon dioxide layers. This composite material approach combines the advantageous properties of both materials - the water barrier properties of silicon nitride and the high adhesion properties of silicon dioxide - creating a passivation system that achieves both protection and adhesion simultaneously.
3Volume of moving object
If the membrane is made small for miniaturization, then calibration and storage volumes are reduced, but adhesion problems become more critical
Solution Approach 1:
The passivation layer is segmented into silicon nitride and silicon dioxide layers, with the silicon dioxide specifically positioned to provide adhesion at the membrane interface. This segmentation ensures that even in miniaturized sensors where the membrane-substrate interface is more critical, the adhesion function is optimized independently of the overall sensor size reduction.
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 solution enhances the adhesion of polymeric membranes to the sensor substrate, improving the reliability and longevity of chemical sensors by preventing osmotic pressure-induced leaks and maintaining electrical integrity.
Implementation Method 1
Silicon dioxide provides a higher level of adhesion for the polymeric membranes than silicon nitride
Implementation Method 2
preventing osmotic pressure-induced leaks
Data Source
AI summary
Sensor devices and systems can include a silicon substrate comprising a sensor-side and a backside. The backside can include a backside electrode. The sensor-side can include a chemical sensor. The chemical sensor can include a chemical sensor electrode, the chemical sensor electrode can be electrically coupled to the backside electrode by a through-silicon via (TSV), the TSV being physically and electrically connected to the chemical sensor electrode and extending from the chemical sensor electrode through the silicon substrate towards the backside. The TSV can electrically connect the chemical sensor to the backside electrode. A printed circuit board can surround the sensor device and can include a metal contact pad. The metal contact pad can be electrically coupled to the backside electrode by a wire bond. The sensor-side can include a polymeric membrane covering the chemical sensor.