Carbon Nanotube Sensor Electrical Connection via TSVs
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Solution Overview
Problem
Existing methods for creating electrical connections to small sensors, such as wire bonding and encapsulation, are challenging due to mechanical fragility and interference from ionic liquids, making it difficult to maintain sensor sensitivity and reliability, especially for devices like chemical or biological sensors.
Innovation Solution
The use of Through Substrate Vias (TSVs) and carbon nanotube sensors with embedded contact pads to establish electrical connections through the substrate, reducing contact resistance and enhancing sensitivity by embedding carbon nanotube ends within metal contact pads, which are connected to TSVs for improved conductivity and insulation from aqueous environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonding is used to create electrical connections to sensors, then electrical contact can be established, but the wire bonds are mechanically fragile and difficult to encapsulate without exposing the sensor area
Solution Approach 1:
The patent extracts the electrical connection function from traditional wire bonding and relocates it to the substrate level through TSVs. The connections are made at the substrate level rather than on the sensor surface, eliminating the fragile wire bonds that extend over the sensor area and complicating encapsulation.
Solution Approach 2:
The patent transitions from planar wire bonding on the sensor surface to vertical through-substrate connections. TSVs provide electrical pathways in the vertical dimension through the substrate, eliminating the need for horizontal wire bonds that interfere with encapsulation and sensor exposure.
2Strength
If encapsulation is used to protect wire bonds, then mechanical damage is prevented, but the sensor area must remain uncovered which is difficult to achieve reliably
Solution Approach 1:
The patent removes wire bonds from the sensor area entirely by routing connections through the substrate via TSVs. This eliminates the need for selective encapsulation of wire bonds while preserving sensor exposure, as the connections are now located at the substrate level rather than on the sensor surface.
Solution Approach 2:
The patent segments the device into distinct functional layers: the sensor area on the first substrate that remains exposed, and the TSV connection region on the second substrate that receives encapsulation. This spatial segmentation allows full encapsulation of connection regions without compromising sensor access.
3Productivity
If sensors are made smaller to increase sensors per wafer, then cost is reduced, but wire bonding and encapsulation become nearly impossible
Solution Approach 1:
The patent uses vertical TSV connections through the substrate to provide electrical access to miniaturized sensors. This vertical connection approach eliminates the need for lateral wire bonding, enabling sensor sizes small enough to have multiple sensors per wafer while maintaining manufacturability through standard TSV and flip-chip processes.
Solution Approach 2:
The patent replaces the mechanical wire bonding process with a semiconductor manufacturing process using TSVs and flip-chip bonding. This substitution enables scaling to smaller sensor dimensions and higher density per wafer, as the connection process is compatible with automated semiconductor fabrication rather than manual or semi-automated wire bonding.
4Reliability
If electrical connections are made to sensors in ionic liquid buffer, then electrical contact is established, but ionic conduction occurs reducing or disabling sensitivity
Solution Approach 1:
The patent introduces an insulating layer as an intermediary between the electrical connection structures and the ionic liquid buffer. This dielectric barrier prevents ionic conduction paths from forming between electrical contacts, allowing sensors to maintain sensitivity while remaining electrically connected in aqueous or ionic environments.
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 enables reliable and scalable production of sensitive sensors with reduced contact resistance, increased conductivity, and improved detection capabilities, overcoming the limitations of traditional methods by maintaining sensor sensitivity and reliability in aqueous environments.
Implementation Method 1
Each of a plurality of contact pads is positioned on the first substrate and on one of the carbon nanotube sensors such that each contact pad is electrically connected to one of the TSVs and the one of the carbon nanotube sensors
Implementation Method 2
embedding carbon nanotube ends within metal contact pads, which are connected to TSVs for improved conductivity
Implementation Method 3
Through Substrate Vias (TSVs) as used herein refer to an alternative to wire bonding, and provide connections to the device vertically through the substrate itself
Data Source
AI summary
A sensing device includes a first substrate having a plurality of TSVs extending therethrough, and a second substrate positioned adjacent the first substrate, with the TSVs being electrically connected to the second substrate. At least one carbon nanotube sensor is positioned on the first substrate. Each of a plurality of contact pads is positioned on the first substrate and on one of the carbon nanotube sensors such that each contact pad is electrically connected to one of the TSVs and the one of the carbon nanotube sensors, and such that an end of the one of the carbon nanotube sensors is embedded in the contact pad.