Ion Concentration Sensor With Backside Wiring
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional FET ion sensors require a thick multilayer wiring structure due to exposed silicon nitride films, which is undesirable and limits the production process, especially for digital signal output sensors, and they lack a system-on-chip configuration with integrated ion-sensing arrays and circuit sections.
Innovation Solution
An ion concentration sensor is designed with a semiconductor layer between a supporting substrate and sensing sections, featuring transistors for reading analog signals and an analog-to-digital conversion circuit above the substrate, allowing for a system-on-chip structure with reduced wiring complexity and the use of alternative insulating films like aluminum oxide or tantalm oxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional FET ion sensor uses an exposed silicon nitride film as the sensing film, then the sensor can detect hydrogen ion concentration through surface electric potential change, but a thick multilayer wiring structure must be provided around the ion-sensing array, increasing device complexity and limiting production process
Solution Approach 1:
The patent applies dimensionality change by moving the transistor gates from the same plane as the sensing array to the opposite surface of the semiconductor substrate. This spatial reconfiguration allows wiring to be routed on the backside of the chip, separating the sensing plane from the wiring plane and eliminating the need for thick multilayer wiring structures around the sensing array.
Solution Approach 2:
The patent inverts the conventional architecture by placing the transistor gates on the opposite surface of the semiconductor substrate rather than on the same surface as the sensing elements. This inversion allows the wiring structure to be positioned away from the sensitive sensing region, reducing wiring complexity and enabling more efficient production processes.
2Productivity
If a system-on-chip configuration integrates the ion-sensing array and circuit section on a single chip, then productivity and integration are improved, but basic configuration elements must be provided outside the ion-sensing array region, requiring additional wiring layers
Solution Approach 1:
The patent utilizes the third dimension (depth) by routing wiring on the opposite surface of the chip from the sensing array. This allows the circuit section to be integrated on the same chip without requiring additional wiring layers between the sensing array and circuit elements, as the wiring can pass through or around the chip substrate.
Solution Approach 2:
The patent segments the chip into two functional surfaces: the front surface contains the ion-sensing array with exposed silicon nitride film, while the back surface contains the transistor gates and wiring structure. This segmentation allows each surface to be optimized for its specific function without interference from the other.
3Extent of automation
If digital signal output is implemented, then signal processing capability is improved, but a wiring structure consisting of four to six layers is needed, significantly increasing device complexity
Solution Approach 1:
The patent resolves the wiring complexity issue for digital output by routing all necessary wiring on the opposite surface of the sensing array. This allows multiple wiring layers to be stacked on the backside of the chip without increasing the lateral footprint or interfering with the front-side sensing elements, enabling digital signal processing capability without proportionally increasing overall device complexity.
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 configuration enables a compact, high-sensitivity ion concentration sensor with improved signal-to-noise ratio and faster signal readout, capable of simultaneous measurement of multiple cells, and allows for the use of alternative ion-sensitive films beyond silicon nitride, facilitating downsizing and enhanced ion sensitivity.
Implementation Method 1
detect a hydrogen ion concentration through the use of change in surface electric potential of a semiconductor substrate, which change is caused by a reaction of (i) dangling bonds and (ii) hydrogen ions on a surface of the silicon nitride film
Data Source
AI summary
Provided is an ion sensor including a supporting substrate, a plurality of cells, a silicon substrate, a plurality of transistors, and an analog-digital conversion circuit. The plurality of cells, the plurality of transistors, and the analog-digital conversion circuit are provided above the supporting substrate. Each of the plurality of transistors has a corresponding gate provided on a first surface of the silicon substrate. The analog-digital conversion circuit is provided on the silicon substrate. The ion-sensing surface is provided on a second surface of the silicon substrate. The second surface is opposite to the first surface.