CMOS-Compatible BioFET Back-Gate Layout for Label-Free Sensing
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Solution Overview
Problem
Challenges in the fabrication and operation of BioFETs arise due to compatibility issues between semiconductor fabrication processes and biological applications, integration of electrical signals and biological interactions, and limitations in large-scale integration, particularly in constructing devices like ISFETs and those with multi-layer interconnects that affect sensitivity and reliability.
Innovation Solution
A BioFET device is fabricated using complementary metal oxide semiconductor (CMOS) compatible processes, where a gate structure is replaced by a bio-compatible layer with immobilized probe molecules, allowing label-free detection of biomolecules through conductance modulation, and a back gate configuration to control the channel electron distribution without bulk substrate effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional semiconductor fabrication processes are used for BioFET fabrication, then manufacturing precision is improved, but compatibility with biological applications deteriorates
Solution Approach 1:
The patent modifies fabrication parameters by using CMOS-compatible processes with specific adjustments: forming the gate structure on the backside of the substrate, using thinning processes to expose the channel region, and controlling oxide layer thickness (50-200nm) to achieve both manufacturing precision and biological compatibility. This allows standard semiconductor processes to be adapted for bio-sensing applications.
Solution Approach 2:
The patent inverts the conventional BioFET fabrication approach by forming the gate structure on the backside of the substrate rather than the frontside. This inversion allows the channel region to be exposed on the front surface for biological interaction while maintaining CMOS fabrication compatibility, resolving the contradiction between manufacturing precision and biological compatibility.
2Adaptability or versatility
If multi-layer interconnect structures are added to BioFET, then device functionality is improved, but sensitivity deteriorates due to increased parasitic capacitance
Solution Approach 1:
The patent moves the gate structure to the backside dimension of the substrate, creating a three-dimensional configuration where the gate is spatially separated from the front surface biological interaction area. This dimensional change allows multi-layer interconnects to be added on the front surface without increasing parasitic capacitance at the sensing interface, thus maintaining sensitivity while improving functionality.
Solution Approach 2:
The patent segments the device into distinct functional regions: the backside gate structure for electrical control and the front surface channel region for biological interaction. This segmentation allows independent optimization of each region, enabling multi-layer interconnects to be added for functionality without compromising the sensitivity of the biological sensing region.
3Measurement precision
If labeling operations are performed for biomolecule detection, then detection capability is improved, but cost and complexity increase
Solution Approach 1:
The BioFET device performs label-free detection by directly measuring the electrical properties (conductance, threshold voltage) of biomolecules as they interact with the channel region. The device serves itself by using its inherent transistor characteristics to detect biomolecular presence, binding, and concentration without requiring external labels or markers, thus reducing complexity while maintaining detection capability.
Solution Approach 2:
The patent replaces the mechanical/chemical labeling system with an electrical field-based detection system. Instead of using physical labels or chemical markers to detect biomolecules, the device uses the electrical field in the channel region to directly sense biomolecular properties, substituting a complex labeling mechanism with a simpler electrical measurement approach.
4Productivity
If BioFET is used for large-scale integration, then productivity is improved, but fabrication challenges increase due to process compatibility issues
Solution Approach 1:
The patent creates a universal fabrication platform using CMOS-compatible processes that can produce both standard electronic devices and BioFET sensors using the same manufacturing line. The backside gate structure and thinning process are universal techniques that work for both conventional and bio-sensing applications, enabling large-scale integration without requiring separate fabrication facilities or complex process adjustments.
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 CMOS-compatible BioFET enables efficient, sensitive, and reliable detection of various biomolecules and bio-entities by avoiding costly labeling operations and minimizing parasitic capacitances, enhancing detection capabilities through array configurations and differential sensing.
Implementation Method 1
a gate structure disposed on a first surface of the substrate... a channel region interposing the source and drain regions and underlying the gate structure
Implementation Method 2
an interface layer formed on the second surface of the substrate in the opening... operable to provide a binding interface for at least one of a biomolecule and a bio-entity
Data Source
AI summary
The present disclosure provides a bio-field effect transistor (BioFET) and a method of fabricating a BioFET device. The method includes forming a BioFET using one or more process steps compatible with or typical to a complementary metal-oxide-semiconductor (CMOS) process. The BioFET device may include a substrate; a gate structure disposed on a first surface of the substrate and an interface layer formed on the second surface of the substrate. The interface layer may allow for a receptor to be placed on the interface layer to detect the presence of a biomolecule or bio-entity.