Chemically Sensitive Sensor With Floating Gate And Lightly Doped Drains
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Solution Overview
Problem
Ion-sensitive field effect transistors (ISFETs) require additional amplification circuitry to process small electrical signals from chemical reactions, which occupies valuable semiconductor substrate space and is inefficient.
Innovation Solution
A chemically sensitive sensor with modified gain is fabricated using a substrate with lightly doped drains and a floating gate structure, which modifies capacitance and eliminates the need for additional amplification circuitry by adjusting parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional amplification circuitry is added to process small electrical signals from chemical reactions, then signal processing capability is improved, but semiconductor substrate space is consumed
Solution Approach 1:
The patent combines the sensing function and amplification function into a single integrated structure. The floating gate sensor merges the chemical sensing capability with the signal amplification capability, eliminating the need for separate amplification circuitry and thereby conserving substrate space while maintaining signal processing capability.
Solution Approach 2:
The floating gate structure serves multiple functions simultaneously: it acts as both the sensing element for detecting chemical reactions and the amplification element for processing the small electrical signals generated. This multi-functionality resolves the contradiction by eliminating dedicated amplification circuitry while preserving signal processing capability.
2Reliability
If additional amplification circuitry is added to process small electrical signals, then signal gain is improved, but device complexity increases
Solution Approach 1:
The patent merges the sensing function and amplification function into a single integrated structure. The floating gate sensor combines the chemical sensing capability with the signal amplification capability in one device, reducing the number of separate components and simplifying the overall circuit architecture while achieving the required signal gain.
Solution Approach 2:
The floating gate structure is self-amplifying, where the sensing mechanism inherently provides signal amplification through the floating gate effect. This self-service characteristic eliminates the need for external amplification circuitry, thereby reducing device complexity while maintaining signal gain.
3Ease of manufacture
If conventional ISFET structure is used, then fabrication simplicity is maintained, but signal gain is insufficient
Solution Approach 1:
The patent modifies the conventional ISFET structure by introducing a floating gate configuration, which changes the electrical parameters of the device. This parameter change enables inherent signal amplification through the floating gate effect, improving signal gain while maintaining compatibility with standard CMOS fabrication processes.
Solution Approach 2:
The floating gate structure uses a composite configuration combining insulating materials (oxide layers) with conductive elements, creating a structure that provides both the necessary electrical isolation and signal amplification. This composite approach achieves improved signal gain while remaining compatible with conventional fabrication methods.
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
The modified chemically sensitive sensor achieves enhanced signal gain without the need for additional amplification circuitry, optimizing substrate usage and improving signal processing efficiency.
Implementation Method 1
A chemically sensitive sensor with modified gain is fabricated using a substrate with lightly doped drains and a floating gate structure, which modifies capacitance and eliminates the need for additional amplification circuitry by adjusting parasitic capacitance.
Implementation Method 2
A chemically sensitive sensor with modified gain is fabricated using a substrate with lightly doped drains and a floating gate structure, which modifies capacitance and eliminates the need for additional amplification circuitry by adjusting parasitic capacitance.
Implementation Method 3
Like a MOSFET, the operation of an ISFET is based on the modulation of charge concentration (and thus channel conductance) caused by a MOS (Metal-Oxide-Semiconductor) capacitance.
Implementation Method 4
an ISFET is an impedance transformation device that operates in a manner similar to that of a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), and is particularly configured to selectively measure ion activity in a solution
Data Source
AI summary
A chemically sensitive sensor with a lightly doped region that affects an overlap capacitance between a gate and an electrode of the chemical sensitive sensor. The lightly doped region extends beneath and adjacent to a gate region of the chemical sensitive sensor. Modifying the gain of the chemically sensitive sensor is achieved by manipulating the lightly doped region under the electrodes.