Integrated Circuit Sensing Electrodes with Upward Extensions
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Solution Overview
Problem
Existing integrated circuits (ICs) for DNA sequencing require a large number of processing steps, leading to increased costs and limited sensitivity due to the use of passivation layers that restrict material choices and electrode surface area, which affects signal-to-noise ratio and miniaturization.
Innovation Solution
The integration of ion-sensitive electrodes with upwardly extending portions into the metallization stack of the IC, allowing for increased electrode area and reduced well dimensions, combined with a modified manufacturing process that incorporates a patterned metal layer for high-resolution etching and reduced processing steps, uses Ta2O5 as a pH-sensitive material for improved linearity and moisture protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the passivation layer is used as the pH sensitive material on the extended gate electrodes, then the underlying structures of the IC are protected from external influences, but the sensitivity of the FETs is limited due to the minimum thickness requirement of the passivation layer and the restricted material choices
Solution Approach 1:
The solution segments the protective and sensing functions into separate layers: a thick passivation layer (50-200 nm) for protection and a thin ion-sensitive layer (5-50 nm) for sensing. This segmentation allows each layer to be optimized independently - the passivation layer provides sufficient thickness for protection while the ion-sensitive layer provides high sensitivity with minimal thickness requirements.
Solution Approach 2:
The solution uses composite material structure combining a standard passivation material (such as silicon oxide) with an ion-sensitive material (such as Ta2O5, Al2O3, or Si3N4). This composite approach allows the system to benefit from both the protective properties of the passivation layer and the sensing properties of the ion-sensitive material, resolving the contradiction between protection and sensitivity.
2Area of moving object
If the surface area of the sensor electrode is decreased, then the IC can be miniaturized, but the signal to noise ratio decreases
Solution Approach 1:
The solution extends the electrode surface area into the vertical dimension by creating upwardly extending portions that protrude into the sample well. This dimensional transformation allows the electrode to maintain a small footprint in the planar direction (enabling IC miniaturization) while increasing the effective sensing surface area vertically (maintaining signal-to-noise ratio).
3Manufacturing precision
If a large number of additional process steps are used to manufacture the IC, then the pH-sensitive electrodes can be formed with proper structure, but the cost of the IC increases
Solution Approach 1:
The solution merges the formation of the ion-sensitive layer with the existing passivation layer deposition process. Both layers are deposited using the same atomic layer deposition (ALD) process, allowing the ion-sensitive layer to be formed concurrently with or immediately following the passivation layer without requiring additional process equipment or significant process steps, thereby reducing manufacturing cost while maintaining structural precision.
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 the miniaturization of sample wells to sub-micron dimensions, enhances the signal-to-noise ratio, reduces manufacturing costs, and allows for a higher density of sensing electrodes while maintaining sensitivity and protection against environmental influences.
Implementation Method 1
each sensing electrode comprises an ion-sensitive layer such as a pH-sensitive layer... Ta2O5 as this also is particularly moisture impenetrable, and moreover has very good linearity of electrical response in a large pH range
Implementation Method 2
by extending the area of the electrodes upwards into the wells, e.g. as part of, on, or substantially adjacent to the sidewalls of the sample wells, the area of the electrode can be significantly increased
Implementation Method 3
the passivation layer is required to have a minimum thickness in order to effectively protect the underlying structures of the IC from external influences
Data Source
AI summary
Disclosed is an integrated circuit comprising a substrate (10) carrying plurality of circuit elements (20); a plurality of sensing electrodes (34) over said substrate, each sensing electrode being electrically connected to at least one of said circuit elements; and a plurality of wells (50) for receiving a sample, each sensing electrode defining the bottom of one of said wells, wherein each sensing electrode comprises at least one portion (34′) extending upwardly into said well. A method of manufacturing such an IC is also disclosed.