SENSOR DEVICE FOR DETECTING A TARGETED MOLECULE

Abstract

A sensor device (100) for detecting a targeted moleculeis provided.The sensor device (100) comprises a field-effect transistor (FET) structure (102), which includes a gate stack region (104) that serves as the sensing surface. The gate stack region (104) contains a metal gate (106), a gate dielectric (108), and a channel region (110). A nanocavity (302) is formed in the gate stack region (104), enabling the adsorption of target molecules, such as gases, liquids, biomolecules, or chemical molecules. The adsorption of the target molecule causes a change in the work function (WF) of the gate stack region (104), resulting in a significant variation in the threshold voltage (VT) of the sensor device (100). This VT variation induces a corresponding change in the drain current and the on-state current (ION), enabling detection of the target molecule. The sensor device (100) identifies the type of molecule based on measured current variations in the FET structure (102). FIG. 1

Specification

Description:[0001] The embodiments herein generally relateto sensors, biosensors, transistors and manufacturing process technology and fabrication of semiconductor devices and electronic nose, more particularly to a sensor device for detecting a targeted molecule.
Description of the Related Art
[0002] Field-effect transistor (FET)-based sensor devices have seen increasing applications in food, biomedical, and chemical industries due to their accurate detection of nano molecules. Their integration with CMOS technology, coupled with high sensitivity, makes them precise, fast, and ideal for miniaturized on-chip systems. Unlike traditional ion-sensitive FET sensors that show good sensitivity to charged biomolecules, they struggle to detect neutral molecules. This limitation has prompted the development of alternative FET structures, such as CombFET and Fishbone FET designs, which offer improved electrostatic control in the channel region and increased drive current (ION). These MOS-based designs enhance the detection of both neutral and charged molecules, expanding the functionality and applicability of FET-based sensors.
[0003] Several prior patents and publications have contributed to advancements in FET-based sensors, addressing various aspects of molecular sensing:An existing system (US 7,868,399 B2) focuses on pH level/ion concentration detection using a nitride active structure in the sensing layer.Another existing system (US 7,918,123 B2) introduces a FET-based gas sensor with a gas-sensitive layer, where the work function is dependent on the concentration of target gases, separated from the channel by an air gap.Yet another existing system (US 12/937,243) proposes a sub-threshold CapFET sensor with a VO2 channel, enabling superior speed and device density improvements over conventional MOSFETs.Yet another existing system (US 2569347A) uses a semiconductive material where the presence of an analyte modulates the work function of the gate, with the FET biased in the sub-threshold region for enhanced sensitivity.
[0004] Additionally, research publications have further explored FET structures. For example, the GAA-NSFET biosensor shows high sensitivity for neutral and charged biomolecules, outperforming traditional TFET sensors. Similarly, a tunnel FET biosensor based on III-V stacked gate-oxide heterostructures demonstrates improved charge carrier mobility and leakage current reduction, enhancing overall sensing capabilities.
[0005] Hence, there remains a need for enhanced FET-based sensors that can address the limitations of ion-sensitive sensors, particularly in detecting neutral molecules. SUMMARY
[0006] In view of the foregoing, an embodiment herein provides a sensor device for detecting a targeted molecule. The sensor device includesa field-effect transistor (FET) structure. The FET structure includes a gate stack region serving as a sensing surface. The gate stack region includesa metal gate, a gate dielectric, and a channel region. The gate stack region forms a nanocavity for adsorption of a target molecule which causes a change in work function (WF) of the gate stack region. The target molecule includesa gas, a liquid, a biomolecule or a chemical molecule, which come in contact with the gate stack region. The sensor device detects a change in the work function (WF) of the gate stack region due to the adsorption of the target molecule in the nanocavity, resulting in a significant change in a threshold voltage (VT) of the sensor device. The threshold voltage variation (VT) in the sensor device induces a corresponding variation in a drain current of the sensor device and a minor change in the threshold voltage (VT) due to the presence of the target molecule leading to variations in the on-state current (ION) of the sensor device. The sensor device is configured to detect the target molecule by determining a type of target molecule that corresponds to the measure current variation in the FET structure.
[0007] The FET structure, particularly the nanocavity in the gate stack region, allows for highly sensitive detection of target molecules. Even small changes in the work function (WF) caused by adsorption result in noticeable variations in threshold voltage (VT) and current, enabling the detection of low concentrations of target molecules.The sensor device is capable of detecting a wide range of target molecules, including gases, liquids, biomolecules, and chemical molecules. This versatility makes it suitable for applications across various fields, such as environmental monitoring, medical diagnostics, and chemical detection.The changes in threshold voltage and current occur in real-time when the target molecule adsorbs onto the gate stack region. This allows for rapid detection and response, making the sensor device suitable for applications requiring immediate feedback.The sensor device does not require external labelling or chemical modifications of the target molecules. The direct interaction between the target molecule and the gate stack region simplifies the detection process and reduces operational complexity. The FET-based sensors are known for their low power consumption, making this sensor device energy-efficient. This is especially beneficial for portable or battery-operated applications.
[0008] The FET structure can be scaled down to nanoscale dimensions, making it suitable for integration into compact, miniaturized systems. This allows for the development of small, portable sensor devices for various applications.By engineering the nanocavity and surface properties of the gate stack region, the sensor device can be tailored to preferentially adsorb specific target molecules, enhancing the specificity of detection and reducing false positives.The use of a metal gate and gate dielectric materials provides robustness and stability in different environments, ensuring reliable performance even under varying operational conditions. The sensor device highly effective for a wide range of molecular detection applications, offering a combination of sensitivity, versatility, and practicality.
[0001] In some embodiments, the gate stack region includes a high-k dielectric material and a metal gate, andthe nanocavity is created by etching a portion of the gate metal and dielectric material.In some embodiments,the sensor device operates based on effective work function (EWF) modulation, caused by the adsorption of the target molecule, leading to changes in the threshold voltage (VT) and the on-state current (ION).
[0002] In some embodiments,the nanocavity is filled with biomolecules, gases, or chemicals that alter the dielectric constant of the gate dielectric, further modulating the threshold voltage and drive current of the sensor device.In some embodiments,the FET structure includes aCombFET or a Fishbone FET having an extended gate stack region for enhanced sensitivity to the target molecule through the work function variation mechanism.In some embodiments, the gate width of the CombFET or Fishbone FET is adjusted through a layout design, thereby providing flexibility in optimizing sensor performance for different materials or gases.
[0003] The CombFET and Fishbone FET, utilizing effective work function-based mechanismsby offering enhanced electrostatic control and increased drive current, making them highly effective for detecting a broader range of molecules. The CombFET and Fishbone FET are well-suited for on-chip integration and are fully compatible with existing CMOS process technologies, providing a robust solution across various industries.
[0004] In one aspect, a method for detecting a target molecule using a sensor device is provided. The method includes (i) providing a field-effect transistor (FET) structure, wherein the FET structure includes a gate stack region serving as a sensing surface, the gate stack including a metal gate, a gate dielectric, and a channel region;(ii) forming a nanocavity within the gate stack region for the adsorption of a target molecule, wherein the target molecule includesa gas, a liquid, a biomolecule, or a chemical;(iii) exposing the gate stack region to the target molecule, allowing the target molecule to come into contact with and be adsorbed into the nanocavity;(iv) detecting a change in the work function (WF) of the gate stack region due to the adsorption of the target molecule, wherein the change in WF results in a variation in the threshold voltage (VT) of the sensor device;(v) measuring the corresponding variation in the drain current of the sensor device, wherein a minor variation in the threshold voltage (VT) due to the presence of the target molecule induces a change in the on-state current (ION); and(vi) identifying the type of target molecule by determining the measured current variation in the FET structure that corresponds to the detected threshold voltage (VT) change.
[0005] In some embodiments, the nanocavity is formed by anisotropic etching of the gate metal and the gate dielectric.In some embodiments, the method includes extracting electrical characteristics, including threshold voltage (VT), on-state current (ION), off-state current (IOFF), and subthreshold swing (SS), to determine the sensitivity and signal strength of the detected target molecule.In some embodiments, the dielectric constant of the gate dielectric is modulated by the presence of biomolecules, leading to electrical characteristic changes in the FET sensor device.
[0006] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings.It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation.Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which:
[0008] FIG. 1 illustrates a block diagram of a sensor device for detecting a targeted moleculeaccording to an embodiment herein;
[0009] FIG. 2 illustrates an exemplary sensor device of FIG. 1 according to an embodiment herein;
[0010] FIGS. 3A & 3B illustrate exemplary sensor devicesof FIG. 1 illustrating the working principle of sensor applicationsaccording to an embodiment herein;
[0011] FIG. 4illustratesa 3-dimensional (3D) exemplary sensor device of FIG. 1 according to an embodiment herein;
[0012] FIGS. 5A-5Cillustrate cross-section profiles of an exemplary sensor device of FIG. 1 according to an embodiment herein;
[0013] FIGS. 6A & 6Billustrate a process for fabricating aCombFET-based sensor deviceaccording to an embodiment herein;
[0014] FIGS. 7A & 7Billustrate a 2-Dimensional(2D) cross-section profile and a top view of a CombFET-based sensor devicefor illustrating the trench configuration in the sensor device according to an embodiment herein;
[0015] FIG. 8 illustrates a process for fabricating aFishbone FET-based sensor deviceaccording to an embodiment herein;
[0016] FIG. 9 is a flow diagram that illustratesa method for detecting a target molecule using a sensor deviceaccording to an embodiment herein;
[0017] FIGS. 10A& 10Billustrate a Transfer (Id-Vgs) characteristics of the CombFET-based sensor device according to an embodiment herein;and
[0018] FIGS. 11A & 11B illustratea plot showing athreshold voltage (VT) variation of the CombFET-based sensor device according to an embodiment herein.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0019] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0020] As mentioned, there remains a need for a sensor device for detecting a targeted moleculeand a method for detecting a targeted moleculeusing a sensor device.Various embodiments disclosed herein providea sensor device for detecting a targeted moleculeand a method for detecting a targeted moleculeusing a sensor device. Referring now to the drawings, and more particularly to FIGS. 1 through11B, where similar reference characters denote corresponding features consistently throughout the figures, preferred embodiments are shown.
[0009] FIG. 1 illustrates a block diagram of a sensor device 100 for detecting a targeted molecule according to an embodiment herein.The sensor device 100 includesa field-effect transistor (FET) structure 102. The FET structure 102 includes a gate stack region 104 serving as a sensing surface. The gate stack region 104 includes a metal gate 106, a gate dielectric 108, and a channel region 110. The gate stack region 104 forms a nanocavity for adsorption of a target molecule which causes a change in work function (WF) of the gate stack region 104. The target molecule includes a gas, a liquid, a biomolecule or a chemical molecule, which come in contact with the gate stack region 104. The sensor device 100 detects a change in the work function (WF) of the gate stack region 104 due to the adsorption of the target molecule in the nanocavity, resulting in a significant change in a threshold voltage (VT) of the sensor device 100. The threshold voltage variation (VT) in the sensor device 100 induces a corresponding variation in a drain current of the sensor device 100 and a minor change in the threshold voltage (VT) due to the presence of the target molecule leading to variations in the on-state current (ION) of the sensor device 100. The sensor device is configured to detect the target molecule by determining a type of target molecule that corresponds to the measured current variation in the FET structure 102.
[0010] The FET structure 102, particularly the nanocavity in the gate stack region 104, allows for highly sensitive detection of target molecules. Even small changes in the work function (WF) caused by adsorption result in noticeable variations in threshold voltage (VT) and current, enabling the detection of low concentrations of target molecules.The sensor device 100is capable of detecting a wide range of target molecules, including gases, liquids, biomolecules, and chemical molecules. This versatility makes it suitable for applications across various fields, such as environmental monitoring, medical diagnostics, and chemical detection.The changes in threshold voltage and current occur in real-time when the target molecule adsorbs onto the gate stack region 104. This allows for rapid detection and response, making the sensor device 100suitable for applications requiring immediate feedback.The sensor device 100does not require external labeling or chemical modifications of the target molecules. The direct interaction between the target molecule and the gate stack region 104 simplifies the detection process and reduces operational complexity. The FET-based sensors are known for their low power consumption, making this sensor device 100 energy-efficient. This is especially beneficial for portable or battery-operated applications.
[0011] The FET structure 102 can be scaled down to nanoscale dimensions, making it suitable for integration into compact, miniaturized systems. This allows for the development of small, portable sensor devices for various applications.By engineering the nanocavity and surface properties of the gate stack region 104, the sensor device 100can be tailored to preferentially adsorb specific target molecules, enhancing the specificity of detection and reducing false positives.The use of a metal gate and gate dielectric materials provides robustness and stability in different environments, ensuring reliable performance even under varying operational conditions. The sensor device 100 highly effective for a wide range of molecular detection applications, offering a combination of sensitivity, versatility, and practicality.
[0021] In some embodiments, the gate stack region 104includes a high-k dielectric material and a metal gate 106, andthe nanocavity is created by etching a portion of the gate metal and dielectric material.In some embodiments,the sensor device 100 operates based on effective work function (EWF) modulation, caused by the adsorption of the target molecule, leading to changes in the threshold voltage (Vt) and the on-state current (ION).
[0022] In some embodiments,the nanocavity is filled with biomolecules, gases, or chemicals that alter the dielectric constant of the gate dielectric 108, further modulating the threshold voltage and drive current of thesensor device 100.In some embodiments, the FET structure 102 includes aCombFET or a Fishbone FET having an extended gate stack region 104 for enhanced sensitivity to the target molecule through the work function variation mechanism. In some embodiments, the gate width of the CombFET or Fishbone FET is adjusted through a layout design, thereby providing flexibility in optimizing sensor performance for different materials or gases.
[0023] The CombFET and Fishbone FET, utilizing effective work function-based mechanismsby offering enhanced electrostatic control and increased drive current, making them highly effective for detecting a broader range of molecules. The CombFET and Fishbone FET are well-suited for on-chip integration and are fully compatible with existing CMOS process technologies, providing a robust solution across various industries.
[0024] Table 1: Extraction of the electrical characteristics of the CombFET-based sensor device 100. The variation in the WF may cause VT and ION shifts in the sensor device 100, which can be used to sense the sensitivity and detection of signals for the targeted gas, liquid, and chemical. The study is performed on the Sentaurus TCAD device simulator in saturation region.
[0025] Table 1:
WF (eV) VT (V) ION (µA) IOFF (pA) SS (mV/dec)
4.23 0.102 148.10 40492 139.01
4.33 0.106 143.93 45939 70.91
4.39 0.149 139.10 7519.51 63.44
4.46 0.202 127.71 1015.63 61.38
4.48 0.216 123.46 585.04 61.14
4.53 0.251 112.60 1548.01 60.76
4.62 0.311 92.37 15.84 60.40
4.66 0.342 80.86 4.76 60.27
[0012] Table 2: Extraction of the key electrical characteristics of the CombFET-based sensor devices in the presence of biomolecules with different dielectric constants. VT and ION variations in the sensor device 100 can be used in the detection of the signal and sensitivity of the target.
[0013] Table 2:
Dielectric Constant VT (V) ION (µA) IOFF (pA) SS (mV/dec)
1.5 0.318 83.52 10.65 59.88
2.1 0.317 85.25 10.91 59.92
2.63 0.316 86.45 11.21 59.99
5.0 0.315 89.71 12.46 60.15
7.0 0.313 90.94 13.43 60.22
10.0 0.312 91.97 14.94 60.33
11.7 0.311 92.37 15.84 60.40
[0014] FIG. 2 illustrates an exemplary sensor device 100of FIG. 1 according to an embodiment herein.The sensor device 100 includesa field-effect transistor (FET) structure 102. The FET structure 102includes a gate stack region 104 serving as a sensing surface. The gate stack region 104 includes a metal gate 106, a gate dielectric 108, and a channel region 110. The gate stack region 104 forms a nanocavity for adsorption of a target molecule which causes a change in work function (WF) of the gate stack region 104. The target molecule includes a gas, a liquid, a biomolecule or a chemical molecule, which come in contact with the gate stack region 104. The sensor device 100 detects a change in the work function (WF) of the gate stack region 104 due to the adsorption of the target molecule in the nanocavity, resulting in a significant change in a threshold voltage (VT) of the sensor device 100. The threshold voltage variation (VT) in the sensor device 100 induces a corresponding variation in a drain current of the sensor device 100 and a minor change in the threshold voltage (VT) due to the presence of the target molecule leading to variations in the on-state current (ION) of the sensor device 100. The sensor device 100 is configured to detect the target molecule by determining a type of target molecule that corresponds to the measure current variation in the FET structure 102. The FET structure 102 includes aCombFET or a Fishbone FET having an extended gate stack region 104 for enhanced sensitivity to the target molecule through the work function variation mechanism.
[0015] The sensor device 100operates based on variations in the work function (WF) within the gate stack region 104. The channel width of the CombFET and the Fishbone FET can be flexibly adjusted through a layout design, offering a wider optimization range for sensor performance. The gate metal functions as a sensing surface, where targeted atoms or molecules interact. This interaction leads to a change in the WF, which in turn causes variations in the threshold voltage (VT) and the ON current (ION) of the sensor device 100.
[0016] In some embodiments, the nanocavity is used to detect target atoms and molecules, as the deposition of these molecules within the nanocavity alters the WF of the sensor device 100. The electrical characteristics of the sensor device 100, including threshold voltage (VT), switching ratio (ION/IOFF), and subthreshold swing (SS), can also be modulated. By analyzing changes in these electrical properties, the sensor device 100detects the sensitivity and signal strength of the target molecule/material.
[0017] The FET-based sensor devices outperform traditional ion-based sensor (IoS) devices by offering superior sensing accuracy and the ability to detect a wider range of signal strengths, largely due to their compatibility with existing CMOS technology. Unlike IoS devices, FET-based sensor devices are capable of detecting both neutral and charged biomolecules.
[0018] In some embodiments, the nanocavity is created within the gate stack region 104 by etching portions of the metal gate 106 and oxide. This nanocavity, located between the gate metal and the channel region 110, enables the detection of target gases, biomolecules, and chemicals. Each material, with its unique dielectric constant, modulates key electrical characteristics such as threshold voltage (VT), subthreshold swing (SS), on-state current (ION), and off-state current (IOFF). By analyzing these modulations, the sensor device 100 accurately identifies target molecules.
[0019] The CombFET and the Fishbone FET-based sensors are fully compatible with existing process technologies, making them suitable for on-chip integration.
[0026] FIGS. 3A & 3B illustrate exemplary sensor devicesof FIG. 1 illustrating the working principle of sensor applicationsaccording to an embodiment herein.The exemplary sensor device 100in FIG. 3A illustrates the working principle of the sensor applications.The sensor device 100 includesa field-effect transistor (FET) structure 102. The FET structure 102may be a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET).The FET structure 102includes a gate stack region 104. The gate stack region 104 includes a metal gate 106, a gate dielectric 108, and a channel region 110. The gate metal may be used as a sensor surface, and threshold voltage (VT)in the sensor device 100 shifts based on the effective work function (EWF) modulationvariations in the gate stack region 104.
[0027] The working principle of the sensor device 100relies on variations in the threshold voltage (VT). In this exemplary sensor device 100, a large cross-section of the gate metal acts as the sensing material. The gate material itself can be used directly as a sensor, or a nanocavity can be created within the gate material, which is filled by the gas or chemicals being detected. The deposition of different materials in the gate stack region 104causes a change in the work function (WF) of the sensor device 100, leading to variations in VT and the on-state current (ION)of the sensor device 100.
[0028] The working mechanism of the FET-based gas and chemical sensor device 100is as follows: (i) measure the operating threshold voltage (VT) of the sensor device 100 in the absence of target atoms or molecules, and repeat the measurement when target atoms/molecules are present in the gate stack (VT'), (ii) to detect the presence of target atoms/molecules, set the gate voltage to a value between VT and VT', when the target atoms/molecules enter the gate stack: (a) the drain current (ID) significantly increases from 0 A for VT' < VT and the drain current (ID) goes to 0 A for VT' > VT, (iii) work function modulation occurs due to the adsorption of the target gases on the gate stack or due to the air gap in the gate stack, and (iv) the sensing mechanism is based on the shift in VT due to changes in the work function (WF).
[0029] FIG. 3B illustratesexemplary sensor device 100of FIG. 1 illustrating the working principle of sensor applicationsaccording to an embodiment herein. The working principle of a dielectric constant-based sensor device 100 is explained in FIG. 3Busing the basic MOS devices. In FIG. 3B(a), a bulk profile of the exemplary sensor device 100(e.g., 3D MOSFET) is shown.FIG. 3B(b) shows ananocavity 302 which is created in the gate metal and the gate stack region 104 (i.e., high-K oxide region), and FIG. 3B(c) shows the nanocavity 302which is filled by the biomolecules having different dielectric values.
[0030] The working principle of the CombFET and the FishboneFETis based on threshold voltage (VT) variations caused by the presence of materials with different dielectric constants in the gate stack region 104. Thenanocavity 302 is created between the gate stack region 104and channel region 110 by anisotropically etching part of the gate metal and oxide, leaving the channel region 110 exposed. External atoms and biomolecules, such as Streptavidin (k = 2.1), Biotin (k = 2.63), APTES (k = 3.57), Gluten (k = 5), Zenin (k = 7), Keratin (k = 10), and Gelatin (k = 12), can interact with the exposed channel region 110 either through absorption or deposition. These interactions alter the dielectric constant of the oxide. The changes in the dielectric constant of the gate oxide lead to variations in the performance of the sensor device 100, including threshold voltage (VT), on-state current (ION), and the ION/IOFF ratio. These variations are essential for detecting the sensitivity and signal strength of the target gases or chemicals.
[0031] FIG. 4 illustratesa 3-dimensional (3D) exemplary sensor device 100 of FIG. 1 according to an embodiment herein. The sensor device 100 includes the FET structures such as CombFET and Fishbone FET.The CombFET and Fishbone FETfeature a large effective width in the gate stack region 104, which serves as the sensing surface. In FIG. 4, the gate metal of the CombFET and Fishbone FET can serve as the sensor surface, where the target atoms or molecules can get deposited.When specific gases, liquids, or chemical atoms/molecules come into contact with the sensing surface (comprising thin films made of one or more materials), a significant shift in the threshold voltage (VT) of the sensor device 100 occurs.Ab initio and TCAD-based simulations demonstrate that the presence or adsorption of even a few atoms of different materials on the sensor films results in a change in the work function (WF) of the gate stack region 104. The WF shift can range from several tens to a few hundred meV, leading to a corresponding variation in VT.The presence of target atoms can be detected by monitoring changes in VT, on-state current (ION), and the device's switching ratio (ION/IOFF).
[0032] The CombFET and Fishbone FET may be used to evaluate material sensitivity and signal measurement.The sensitivity to target gases, chemicals, and liquids is determined by observing the variation in threshold voltage (VT), which occurs due to changes in the device's work function (WF) when exposed to different materials.Variations in threshold voltage (VT) within the sensor device 100 result in significant changes in the drain current (ID). Even minor shifts in VT caused by the presence of target atoms can induce notable variations in the on-state current (ION), allowing the sensor device 100to effectively detect gases and chemicals on its surface.
[0033] FIGS. 5A-5C illustrate cross-section profiles of an exemplary sensor device 100 of FIG. 1 according to an embodiment herein. FIG. 5A a cross-section profile of an exemplary sensor device 100. The sensor device 100 includesa field-effect transistor (FET) structure 102. The FET structure 102includes a gate stack region 104 serving as a sensing surface. The gate stack region 104 includes a metal gate 106, a gate dielectric 108, and a channel region 110. The gate stack region 104 forms a nanocavity 302 for adsorption of a target molecule which causes a change in work function (WF) of the gate stack region 104. The target molecule includes a gas, a liquid, a biomolecule or a chemical molecule, which come in contact with the gate stack region 104. FIG. 5B illustrates a 2-Dimensional (2D) cross-section profile of the sensor device 100, and thenanocavity 302 created for the deposition of the target atoms and molecules that is filled with the targeted atoms or molecules, which can alter the work function (WF) of the gate stack region 104.The sensor device 100 detects a change in the WF of the gate stack region 104 due to the adsorption of the target molecule in the nanocavity 302, resulting in a significant change in a threshold voltage (VT) of the sensor device 100. The threshold voltage variation (VT) in the sensor device 100 induces a corresponding variation in a drain current of the sensor device 100 and a minor change in the threshold voltage (VT) due to the presence of the target molecule leading to variations in the on-state current (ION) of the sensor device 100. The sensor device 100 is configured to detect the target molecule by determining a type of target molecule that corresponds to the measured current variation in the FET structure 102.In some embodiments, the gate stack region 104includes a high-k dielectric material and a metal gate 106, andthe nanocavity 302 is created by etching a portion of the gate metal and dielectric material.In some embodiments, the FET structure 102 includes aCombFET or a Fishbone FET having an extended gate stack region 104 for enhanced sensitivity to the target molecule through the work function variation mechanism. In some embodiments, the gate width of the CombFET or Fishbone FET is adjusted through a layout design, thereby providing flexibility in optimizing sensor performance for different materials or gases. FIG. 5C illustrates a2D cross-section profile of the Fishbone FET, the nanocavity 302 is created and deposited with the targeted atoms and molecules, the working principle of the Fishbone FET-based sensor device 100 is similar to the CombFET-based sensor described in FIGS. 3A-3B.
[0034] FIGS. 6A & 6Billustrate a process for fabricating aCombFET-based sensor device 100according to an embodiment herein. The sensor device 100 includesa field-effect transistor (FET) structure 102. The FET structure 102includes a gate stack region 104 serving as a sensing surface. The gate stack region 104 includes a metal gate 106, a gate dielectric 108, and a channel region 110. The gate stack region 104 forms a nanocavity 302 for adsorption of a target molecule which causes a change in work function (WF) of the gate stack region 104. The target molecule includes a gas, a liquid, a biomolecule or a chemical molecule, which come in contact with the gate stack region 104. The FET structure 102 includes aCombFET or a Fishbone FET having an extended gate stack region 104 for enhanced sensitivity to the target molecule through the work function variation mechanism. In some embodiments, the gate width of the CombFET or Fishbone FET is adjusted through a layout design, thereby providing flexibility in optimizing sensor performance for different materials or gases.
[0035] At step 602, the process begins with a silicon wafer, which serves as the substrate for the subsequent layers and structures.At step 604, a silicon-germanium (SiGe) layer is grown on the silicon wafer through epitaxial growth. This layer is crucial for forming the strained silicon channel, which enhances carrier mobility.At step 606, a mandrel pattern is created on the SiGe/Si layer. The mandrel acts as a template for defining the subsequent structures.At step 608, the spacer is patterned and defined around the mandrel. This step also involves forming an inter-bridge layer that acts as a fin, which is essential for the fin field-effect transistor (FET) structure 102.At step 610, selective epitaxial growth is performed on the sides of the fin. This step helps in forming the source and drain regions with precise control over their dimensions and doping profiles.At step 612, the mandrel and the sacrificial SiGe layer are removed to reveal the silicon channel. This step is critical for exposing the channel region 110 where the current will flow.At step 614, shallow trench isolation (STI) is created in the substrate to electrically isolate the n-type and p-type regions. Alternatively, a buried oxide layer may be deposited for isolation purposes.At step 616, polysilicon is patterned to form the dummy gate structure. This dummy gate will later be replaced with the actual gate material.At step 618, silicon nitride is deposited to form spacers around the dummy gate. These spacers help in defining the gate length and isolating the gate from the source and drain regions.At step 620, a doped silicon layer is deposited to form the source and drain regions. This step ensures that the source and drain have the required electrical properties for device operation.
[0036] At step 622, an interfacial layer and gate dielectric 108 are formed to complete the gate stack region 104. The interfacial layer improves the quality of the gate dielectric 108, which is crucial for the device's performance.At step 624, Titanium nitride (TiN) is deposited as the metal gate 106 in the high-k metal gate (HKMG) process. Selective etching is performed in the high-k and metal gate regions to form the gate stack region 104. A nanocavity 302 is formed in the gate stack region 104. This nanocavity 302is essential for the subsequent adsorption of target atoms or molecules. The target atoms or molecules are adsorbed into the nanocavity 302formed in the gate stack region 104. This step is crucial for achieving the desired electrical properties of the gate.At step 626, contacts are formed to connect the source, drain, and gate regions to the external circuitry. This step involves depositing and patterning metal layers to ensure proper electrical connections.
[0037] FIG. 6B shows the proposed schematic steps for fabricatingCombFET-based sensor device 100(2D cross-section or XZ plane cut). FIG. 6B (a-c) represents the deposition of the silicon substrate, buried oxide layer, and epitaxial stacking of the Si-SiGe layer in the vertical direction. FIG. 6B(d) depicts the dummy gate pattering Figures. FIG. 6B(e-g) is for revealing the vertical fin channel, deposition of interfacial layer-high κ gate oxide, and deposition of the metal gate 106. FIG. 6B(h) shows the etching which is performed on the gate stack and creating the cavity. The trench is created for the adsorption of the target atoms and molecules.FIG. 6B (i) showsthe contacts that are formed to connect the source, drain, and gate regions to the external circuitry.
[0038] FIGS. 7A & 7B illustrate a 2-Dimensional(2D) cross-section profile and a top view of a CombFET-based sensor device 100for illustrating the trench configuration in the sensor device 100according to an embodiment herein.FIG. 7A illustratesa 2D cross-section profile view of the CombFET-based sensor device 100for illustrating the trench configuration in the sensor device 100 as described in FIG. 6A. FIG. 7B illustrates a top view of the CombFET-based sensor device 100for illustrating the trench configuration in the sensor device 100as described in FIG. 6A.
[0039] FIG. 8 illustrates a process for fabricating aFishbone FET-based sensor device 100according to an embodiment herein.At step 802,begin with the deposition of alternating layers of silicon (Si) and silicon-germanium (SiGe) on the silicon wafer using epitaxial growth techniques. This multi-layer structure is essential for creating strained silicon channels, which enhance carrier mobility. At step 804,lithography and etching techniques are used to pattern the multi-layer Si/SiGe structure into fins. These fins may form the core of the FinFET devices, providing the necessary geometry for the transistor channels. At step 806,shallow trench isolation (STI) regions are created by etching trenches around the fins and filling them with an insulating material, typically silicon dioxide (SiO₂). Alternatively, for silicon-on-insulator (SOI) technology, deposit a buried oxide layer to isolate the active silicon layer from the substrate.At step 808, selectively etch away the sacrificial SiGe layers from the multi-layer structure. This step exposes the silicon fins and prepares them for subsequent processing steps.At step 810, deposit and pattern polysilicon to form the dummy gate structure. This temporary gate will be used to define the gate length and will be replaced later with the actual gate material.At step 812, deposit a layer of silicon nitride (Si₃N₄) around the dummy gate to form the spacer. This spacer helps in defining the gate length and isolating the gate from the source and drain regions.
[0040] At step 814, pattern the source and drain regions using lithography. Implant or deposit dopants to form the source and drain regions, ensuring proper electrical characteristics for the transistor operation.At step 816, deposit an interfacial layer, typically a thin oxide, to improve the quality of the gate dielectric 108. Perform chemical mechanical polishing (CMP) to planarize the surface and ensure uniformity.At step 818, remove the dummy polysilicon gate using selective etching. Deposit a high-k gate dielectric material, followed by the deposition of the metal gate 106, typically titanium nitride (TiN), to form the final gate stack region 104.At step 820, deposit metal contacts to connect the source, drain, and gate regions to the external circuitry. Perform CMP to planarize the surface and ensure proper contact formation. At step 822, create a trench in the gate stack region 104 by selectively etching the metal gate 106 and gate dielectric 108. This trench will be used for the subsequent deposition of target atoms or molecules.At step 824, deposit the target atoms or molecules into the trench formed in the gate stack region 104. This step is crucial for achieving the desired electrical properties of the gate.
[0041] FIG. 9 is a flow diagram that illustratesa method for detecting a target molecule using a sensor device 100 according to an embodiment herein.At step 902, a field-effect transistor (FET) structure 102 is provided. The FET structure 102includes a gate stack region 104 serving as a sensing surface, the gate stack including a metal gate 106, a gate dielectric 108, and a channel region 110. At step 904, a nanocavity 302is formed within the gate stack region 104 for the adsorption of a target molecule. The target molecule includes a gas, a liquid, a biomolecule, or a chemical.At step 906, the gate stack region 104is exposed to the target molecule, allowing the target molecule to come into contact with and be adsorbed into the nanocavity 302. At step 908, a change in the work function (WF) of the gate stack region 104is detected due to the adsorption of the target molecule. The change in WF results in a variation in the threshold voltage (VT) of the sensor device 100.At step 910, the corresponding variation in the drain current of the sensor device 100 is measured.A minor variation in the threshold voltage (VT) due to the presence of the target molecule induces a change in the on-state current (ION).At step 912, the type of target molecule is identifiedby determining the measured current variation in the FET structure 102 that corresponds to the detected threshold voltage (VT) change.
[0042] FIGS. 10A & 10B illustrate a Transfer (Id-Vgs) characteristics of the CombFET-based sensor device 100according to an embodiment herein.FIG. 10A shows a variation in the threshold voltage (VT) and the drive current (ION). The targeted atoms or molecules of the gas, vapor, and liquid may alter the WF of the gate stack, which causes the VT variation.FIG. 10B shows the Transfer (Id-Vgs) characteristics of the CombFET-based sensor devices. The variation in the dielectric constant is considered in the study.
[0043] FIGS. 11A & 11B illustrate a plot showing athreshold voltage (VT) variation of the CombFET-based sensor device 100according to an embodiment herein.FIG. 11Aillustrates a plot showing the VT variation of the CombFET-based sensor device 100due to the fluctuation in the WF of the gate stack region 104.FIG. 11B illustrates the impact of the deposition of biomolecules with different dielectric constant in the (a) threshold voltage (VT), (b) drain current (Id) of the CombFET-based sensor devices. It can be observed that the presence of the target atoms, and biomolecules in the sensor device 100 can alter the dielectric constant of the gate oxide. The variation in VT and ION in the sensor device 100mayprovide about the sensitivity and the signal strength.
[0044] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the scope of appended claims.
, Claims:I/We claim:
1.A sensor device (100) for detecting a targeted molecule, comprising:
a field-effect transistor (FET) structure (102), wherein the FET structure (102)comprises a gate stack region (104)serving as a sensing surface, wherein the gate stack region (104)comprisesa metal gate (106), a gate dielectric (108), and a channel region (110);
characterized in that, wherein the gate stack region (104)formsa nanocavity (302)for adsorption of a target moleculewhichcauses a change in work function (WF) of the gate stack region (104), wherein the target molecule comprises a gas, a liquid, a biomolecule or a chemical molecule, which come in contact with the gate stack region (104),
wherein the sensor device (100) detects a change in the work function (WF) of the gate stack region (104) due to the adsorption of the target moleculein the nanocavity (302),resulting ina significant change in a threshold voltage (VT) of the sensor device (100), wherein the threshold voltage variation (VT) in the sensor device (100)induces a corresponding variation in a drain current of the sensor device (100) and a minor change in the threshold voltage (VT) due to the presence of the target molecule leading to variations in the on-state current (ION) of the sensor device (100), wherein the sensor device (100) is configured to detect the target moleculeby determining a type of target molecule that corresponds to the measure current variation in the FETstructure (102).


2. The sensor device (100)as claimed in claim 1, wherein the gate stack region (104)comprises a high-k dielectric material and a metal gate (106), and wherein the nanocavity (302) is created by etching a portion of the gate metal and dielectric material.

3. The sensor device (100)as claimed in claim 1, wherein the sensor device (100)operates based on effective work function (EWF) modulation, caused by the adsorption of the target molecule, leading to changes in the threshold voltage (VT) and the on-state current (ION).

4. The sensor device (100)as claimed in claim 1, wherein the nanocavity (302) is filled with biomolecules, gases, or chemicals that alter the dielectric constant of the gate dielectric (108), further modulating the threshold voltage and drive current of thesensor device (100).

5. The sensor device (100)as claimed in claim 1, wherein the FET structure (102) comprises aCombFET or a Fishbone FET having an extended gate stack region (104) for enhanced sensitivity to the targetmolecule through the work function variation mechanism.

6. The sensor device (100)as claimed in claim 5, wherein the gate width of the CombFET or Fishbone FET is adjusted through a layout design, thereby providingflexibility in optimizing sensor performance for different materials or gases.

7. A method for detecting a target molecule using a sensor device (100), the method comprising:
providing a field-effect transistor (FET) structure (102), wherein the FET structure (102) comprises a gate stack region (104) serving as a sensing surface, the gate stack comprising a metal gate (106), a gate dielectric (108), and a channel region (110);
forming a nanocavity (302) within the gate stack region (104) for the adsorption of a target molecule, wherein the target molecule comprises a gas, a liquid, a biomolecule, or a chemical;
exposing the gate stack region (104) to the target molecule, allowing the target molecule to come into contact with and be adsorbed into the nanocavity (302);
detecting a change in the work function (WF) of the gate stack region (104) due to the adsorption of the target molecule, wherein the change in WF results in a variation in the threshold voltage (VT) of the sensor device (100);
measuring the corresponding variation in the drain current of the sensor device (100), wherein a minor variation in the threshold voltage (VT) due to the presence of the target molecule induces a change in the on-state current (ION); and
identifying the type of target molecule by determining the measured current variation in the FET structure (102) that corresponds to the detected threshold voltage (VT) change.

8. The method as claimed in claim 7, wherein the nanocavity (302) is formed by anisotropic etching of the gate metal and the gate dielectric (108).

9. The method as claimed in claim 7, wherein the method comprises extracting electrical characteristics, including threshold voltage (VT), on-state current (ION), off-state current (IOFF), and subthreshold swing (SS), to determine the sensitivity and signal strength of the detected target molecule.

10. The method as claimed in claim 7, wherein the dielectric constant of the gate dielectric (108) is modulated by the presence of biomolecules, leading to electrical characteristic changes in the FET sensor device (100).

Dated this October25, 2024

Arjun Karthik Bala
(IN/PA 1021)
Agent for Applicant

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