Charge Detection Sensor Parasitic Capacitance Reduction
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Solution Overview
Problem
Conventional ion-sensitive FET sensors face reduced sensitivity due to parasitic capacitance and noise from wiring layers, which affects the detection of ions in solutions.
Innovation Solution
A charge detection sensor design where a detection element on one surface of a semiconductor substrate is electrically connected to a detection electrode on a different surface via a contact that penetrates the substrate, reducing parasitic capacitance and noise by eliminating the wiring layer between them, and utilizing a MOSFET with a gate connected to the detection electrode through a conductor or capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wiring layer is sandwiched between the ion sensitive film and the gate of the MOSFET, then electrical connection is achieved, but parasitic capacitance increases and sensitivity decreases
Solution Approach 1:
The patent removes the wiring layer from between the ion-sensitive film and the MOSFET gate, extracting the harmful element that causes parasitic capacitance. The detection electrode is directly connected to the gate through a contact hole, eliminating the intermediate wiring layer that was generating noise and reducing sensitivity.
Solution Approach 2:
The patent transitions from a planar wiring connection to a vertical through-substrate contact. The detection electrode is formed on the back surface of the semiconductor substrate and connects to the gate through a contact hole penetrating the substrate, changing the connection dimension from lateral to vertical, thereby eliminating parasitic capacitance from the wiring layer.
2Reliability
If a wiring layer is placed between the detection electrode and the ion sensitive film, then connectivity is provided, but noise from power supply lines or signal lines mixes into the detection signal
Solution Approach 1:
The harmful wiring layer that introduces noise from power supply and signal lines is completely removed from the detection path. The direct connection between the detection electrode and MOSFET gate through the contact hole eliminates the noise mixing problem that occurred with the intermediate wiring layer.
Solution Approach 2:
The patent introduces a fresh intermediary - the contact hole filled with conductive material - to replace the noisy wiring layer. This new intermediary provides electrical connection without introducing parasitic capacitance or noise from power supply lines, as it is a direct vertical path rather than a lateral wiring trace.
3Ease of manufacture
If the detection electrode and wiring layer are placed on the same surface, then manufacturing is simplified, but capacitive coupling between them reduces detection accuracy
Solution Approach 1:
The patent separates the detection electrode from the ion-sensitive film by placing them on opposite surfaces of the semiconductor substrate. The detection electrode is formed on the back surface while the ion-sensitive film is on the front surface, eliminating capacitive coupling between them while maintaining manufacturing feasibility through standard semiconductor processing techniques.
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 design enhances sensitivity and reduces noise by minimizing capacitive coupling, allowing for more accurate charge detection and potential measurement in solutions.
Implementation Method 1
a contact that penetrates the semiconductor substrate and electrically connects the detection electrode and the detection element
Implementation Method 2
ions in a solution are detected by connecting an ion sensitive film immersed in the solution and a gate of the MOSFET
Data Source
AI summary
To achieve decreased noise and improved sensitivity by reducing parasitic capacitance in a charge detection sensor. The charge detection sensor includes a detection element, a detection electrode, and a contact. The detection element is provided on one surface of a semiconductor substrate and detects a charge. The detection electrode is provided on another surface different from the one surface of the semiconductor substrate. The contact penetrates the semiconductor substrate and electrically connects the detection electrode and the detection element. Since no wiring layer is formed between the detection element and the detection electrode, the parasitic capacitance is reduced.