WO2016032314A1 - An egfet phosphate sensor device - Google Patents
An egfet phosphate sensor device Download PDFInfo
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- WO2016032314A1 WO2016032314A1 PCT/MY2015/000069 MY2015000069W WO2016032314A1 WO 2016032314 A1 WO2016032314 A1 WO 2016032314A1 MY 2015000069 W MY2015000069 W MY 2015000069W WO 2016032314 A1 WO2016032314 A1 WO 2016032314A1
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- Prior art keywords
- phosphate
- egfet
- extended gate
- alloy membrane
- selective alloy
- Prior art date
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/403—Cells and electrode assemblies
- G01N27/414—Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS
Definitions
- This invention relates to an extended gate field effect transistor (EGFET), and more particularly to an EGFET phosphate sensor device for sensing phosphate ions in a solution.
- EGFET extended gate field effect transistor
- Sensors have been commonly used to measure many chemical properties including pH, conductivity, salinity, potassium, nitrate, and phosphate as sensors are generally more robust and versatile and they can achieve high sensitivity with short response time.
- Phosphate sensors typically use one of three main mechanisms; optical sensing, electrochemical sensing, or biological sensing. In brief, optical sensing uses reflectance spectroscopy to detect the level of energy absorbed or reflected by the ions in a solution.
- electrochemical sensing uses ion-selective electrodes to generate a voltage or current output in response to selected ions and their activity in the solution
- biological sensing uses a nutrient-sensitive layer of immobilised enzymes deposited on to an electrode or electrochemical cell to observe the reaction between the nutrient of interest and the enzymes in the solution.
- a field effect transistor may be used as a phosphate sensor by utilising the gate terminal of the FET as a sensor electrode.
- the gate terminal may be coated with a fluid analyte and becomes sensitive to the analytes in the solution.
- ISFET Ion sensitive field effect transistor
- EGFET Extended gate field effect transistor
- EGFET structure is also simpler than ISFET and it separates the sensing layer from the gate of the field transistor.
- the EGFET is able to transfer the interfacial potential formed from the ion sensing layer by a signal wire, and thus a conductive film with only low resistivity is needed to transfer the potential. It is necessary to have a sensor that is able to separate the gate terminal from the analyte to prevent contact between the analytes and the gate electrode in which if it happens, it would lead to chemical reactions between the analytes and the gate terminal and may irreparably damaging the FET device.
- the gate terminal in ISFET device is usually unselective towards other ions, thus it has to be chemically modified, for example by covering the gate terminal with a suitable membrane to transform the device into an ion selective sensor.
- the membranes containing uranyl salophene, organatin and bis-thiourea ionophores are usually used in potentiometric ion selective electrodes or membrane based ISFET.
- the ionophores containing membrane in the phosphate sensor used in ISFET or chemical ion sensitive field effect transistor (CHEMFET) are still having some application problems such as having low sensitivity towards the analytes in the sample solution, short life time span, and perform inconsistently when the sensor device is being used.
- Patent application EP 2522993 A1 mentioned an FET device with dual gate stack and extended gate layer. Although there is an extended gate feature in the sensor device, there is no phosphate selective membrane layer or any features for sensing and measuring phosphate ions, thus making the whole invention in EP 2522993 A1 not ideal as a phosphate sensor.
- patent application US 8,133,750 B2 one of the embodiments mentioned in the prior art is to have a calcium ion sensing membrane layer deposited on a sensing layer made of titanium element. Said feature is for detecting calcium ions in the solution. Thus, the US 8,133,750 B2 is not suitable to be used as a phosphate sensor.
- the conductive wire serves as the extended gate to the sensing film and allows the sensing film to be in contact with the sensing membrane which is in direct contact with the solution.
- the conductive wire itself may not be able to fully separate the analytes from the FET and therefore cause the FET structure to be more susceptible to damage as some chemical components leach away and come in contact with the FET structure through the sensing membrane.
- the invention intends to provide an extended gate field effect transistor (EGFET) sensor device that has low tendency of chemical components leaching away and further damaging the sensor device.
- EGFET extended gate field effect transistor
- the present invention also provides an EGFET sensor device that may sense phosphate ions based on mixed potential theory of corrosion. Furthermore, the invention provides an ion selective sensing membrane that improves corrosion rate and has a high sensitivity towards phosphate ions in a sample solution.
- the present invention relates to an extended gate field effect transistor (EGFET) for sensing phosphate ions in a sample solution, the EGFET comprising: a substrate; a source at one end of the substrate; a drain at the other end of the substrate; an outer circuit wire connecting the source and the drain; a container for holding the sample solution; a reference electrode connected to the outer circuit wire and in contact with the sample solution; and a gate terminal positioned in between the source and the drain; characterised by: an extended gate metallisation layer deposited on top of the gate terminal; a noise reducing layer covering the extended gate metallisation layer; a sensing pad area exposing a part of the extended gate metallisation layer, a phosphate selective alloy membrane deposited in the sensing pad area, wherein the phosphate selective alloy membrane is in contact
- an extended gate field effect transistor for sensing phosphate ions in a sample solution, comprising the steps of: preparing a field effect transistor (FET) wafer comprising: a substrate; a source at one end of the substrate; a drain at the other end of the substrate; and a gate terminal positioned in between the source and the drain characterised by the steps of: depositing an extended gate metallisation layer on the gate terminal; depositing a noise reducing layer covering the extended gate metallisation layer; patterning the noise reducing layer to form a sensing pad area; depositing a phosphate selective alloy membrane on the sensing pad area; and creating an epoxy dam by dispensing epoxy at the edge of the sensing pad for controlling the exposure of the phosphate selective alloy membrane.
- FET field effect transistor
- Figure 1 shows a drawing of an extended gate field effect transistor (EGFET) for sensing phosphate ions in a sample solution.
- Figure 2 shows a flowchart of a method for fabricating the EGFET for sensing phosphate ions.
- EGFET extended gate field effect transistor
- the present invention relates to an extended gate field effect transistor (EGFET) for sensing phosphate ions in a sample solution
- the EGFET comprising: a substrate (10); a source (20) at one end of the substrate (10); a drain (25) at the other end of the substrate (10); an outer circuit wire connecting the source (20) and the drain (25); a container (30) for holding the sample solution; a reference electrode (40) connected to the outer circuit wire and in contact with the sample solution; and a gate terminal (50) positioned in between the source (20) and the drain (25); characterised by: an extended gate metallisation layer (60) deposited on top of the gate terminal (50); a noise reducing layer (70) covering the extended gate metallisation layer (60); a sensing pad area exposing a part of the extended gate metallisation layer (60), a phosphate selective alloy membrane (80) deposited in the sensing pad area, wherein the phosphate selective alloy membrane (80) is in contact with the sample solution; and an extended gate metallisation
- the extended gate metallisation layer (60) is made of a metallic conductor or a non-metallic conductor.
- the metallic conductor may further include aluminium, platinum, or copper.
- the non-metallic conductor may further include graphite, graphene, carbon nanotubes, or conducting polymer.
- the noise reducing layer (70) can be made of any material that is able to prevent light effects, electrostatic discharge, and short circuit related to the use of a transistor.
- the noise reducing layer (70) may also function as a transistor passivation layer.
- the sensing pad area is an area exposing a part of the extended gate metallisation layer (60), so, the base of the sensing pad area is the exposed part of the extended gate metallisation layer (60).
- the sensing pad area allows the phosphate selective alloy membrane (80) to be in contact with the gate metallisation layer (60) and the sample solution.
- the phosphate selective alloy membrane (80) is made of a material comprising cobalt, iron, aluminium, vanadium, or chromium.
- the phosphate selective alloy membrane (80) is preferably made of binary, ternary, quaternary, or quinary alloy.
- the phosphate selective alloy membrane (80) may be considered as a solid state electrode in the present invention.
- the epoxy dam (90) of the present invention is used to control the exposure of the phosphate selective alloy membrane (80) to target analytes in the sample solution. Also shown in Figure 1 , the phosphate selective alloy membrane (80) is not placed directly above the gate terminal (50) which would therefore prevent any possible leaked chemical components from damaging the FET device.
- the EGFET sensor device utilises current versus voltage measuring system to measure the current and voltage curves for different phosphate ion concentrations in the sample solution.
- the present invention is also related to a method for fabricating an extended gate field effect transistor (EGFET) for sensing phosphate ions in a sample solution, comprising the steps of: preparing a field effect transistor (FET) wafer (100) comprising: a substrate (10); a source (20) at one end of the substrate (10); a drain (25) at the other end of the substrate (10); and a gate terminal (50) positioned in between the source (20) and the drain (25) characterised by the steps of: depositing an extended gate metallisation layer (60) on the gate terminal (50) (200); depositing a noise reducing layer (70) covering the extended gate metallisation layer (60) (300); patterning the noise reducing layer (70) to form a sensing pad area (400); depositing a phosphate selective alloy membrane (80) on the sensing pad area (500); and creating an epoxy dam (90) by dispensing epoxy at the edge of the sensing pad (600) for controlling the exposure of the phosphate selective alloy membrane (EGFET)
- the method of the present invention also includes the step of patterning the extended gate metallisation layer (60) to define the extended gate metallisation layer (60) from the gate terminal (50).
- the phosphate selective alloy membrane (80) is deposited during the FET wafer fabrication or at package stage, via hard metal coating process comprising sputtering, e-beam, chemical vapour deposition (CVD), physical vapour deposition (PVD), or electrochemical deposition.
- hard metal coating process comprising sputtering, e-beam, chemical vapour deposition (CVD), physical vapour deposition (PVD), or electrochemical deposition.
- the EGFET sensor device of the present invention is a potentiometric sensor.
- alloy is capable of sensing phosphate ion via mixed potential theory of corrosion.
- the mechanism of mixed potential theory of corrosion occurs when a non-equilibrium state exists at the surface of a working electrode involving two or more electrochemical reactions.
- the reference electrode (40) and the working electrode which is the phosphate selective alloy membrane (80).
- slow oxidation of alloy and simultaneous reduction of both oxygen and alloy ions occur on the surface of the working electrode.
- alloy dissolves and alloy oxide film is formed.
Abstract
The present invention relates to an extended gate field effect transistor (EGFET) with a phosphate selective alloy membrane (80) that has a high sensitivity towards phosphate ions in a solution and improves corrosion rate. The phosphate selective alloy membrane (80) can be made of a binary, ternary, quaternary, or quinary alloy. The EGFET also includes feature such as an extended gate metallisation layer (60) made of a metallic or a non-metallic conductor, which enables the phosphate selective alloy membrane (80) to be separated from the FET wafer of the EGFET. A method for fabricating said EGFET is also disclosed in the present invention. In order to ensure the reliability and accuracy of the EGFET phosphate sensor device when sensing phosphate ions in the solution, and preventing any chemical components from leaching away and further damaging the sensor device, the method emphasises on the steps of depositing the extended gate metallisation layer (60) on the gate terminal (50); depositing the phosphate selective alloy membrane (80) in sensing pad area so that the phosphate selective alloy membrane (80) is in contact with the solution; and creating an epoxy dam (90) for controlling the exposure of the phosphate selective alloy membrane (80) to target analyte in the solution.
Description
AN EGFET PHOSPHATE SENSOR DEVICE
TECHNICAL FIELD OF THE INVENTION
This invention relates to an extended gate field effect transistor (EGFET), and more particularly to an EGFET phosphate sensor device for sensing phosphate ions in a solution.
BACKGROUND OF THE INVENTION
Sensors have been commonly used to measure many chemical properties including pH, conductivity, salinity, potassium, nitrate, and phosphate as sensors are generally more robust and versatile and they can achieve high sensitivity with short response time. Phosphate sensors typically use one of three main mechanisms; optical sensing, electrochemical sensing, or biological sensing. In brief, optical sensing uses reflectance spectroscopy to detect the level of energy absorbed or reflected by the ions in a solution. On the other hand, electrochemical sensing uses ion-selective electrodes to generate a voltage or current output in response to selected ions and their activity in the solution, while biological sensing uses a nutrient-sensitive layer of immobilised enzymes deposited on to an electrode or electrochemical cell to observe the reaction between the nutrient of interest and the enzymes in the solution.
In electrochemical sensing, a field effect transistor (FET) may be used as a phosphate sensor by utilising the gate terminal of the FET as a sensor electrode. The gate terminal may be coated with a fluid analyte and becomes sensitive to the analytes in the solution. Ion sensitive field effect transistor (ISFET) is a device with a combination of electrochemical field with semiconductor technology. Extended gate field effect transistor (EGFET) is developed from ISFET device and involved a lower cost. EGFET structure is also simpler than ISFET and it separates the sensing layer from the gate of the field transistor. Therefore, by preferably choosing EGFET over ISFET, the EGFET is able to transfer the interfacial potential formed from the ion sensing layer by a signal
wire, and thus a conductive film with only low resistivity is needed to transfer the potential. It is necessary to have a sensor that is able to separate the gate terminal from the analyte to prevent contact between the analytes and the gate electrode in which if it happens, it would lead to chemical reactions between the analytes and the gate terminal and may irreparably damaging the FET device.
The gate terminal in ISFET device is usually unselective towards other ions, thus it has to be chemically modified, for example by covering the gate terminal with a suitable membrane to transform the device into an ion selective sensor. In phosphate sensor, the membranes containing uranyl salophene, organatin and bis-thiourea ionophores are usually used in potentiometric ion selective electrodes or membrane based ISFET. The ionophores containing membrane in the phosphate sensor used in ISFET or chemical ion sensitive field effect transistor (CHEMFET) are still having some application problems such as having low sensitivity towards the analytes in the sample solution, short life time span, and perform inconsistently when the sensor device is being used. Besides that, the chemical component tends to leach away and caused functional failure in the sensor device. The prolong exposure of the sensor device in such harsh environment will eventually cause delamination of the sensing membrane and the polymeric matrix to peel off from the surface of transducer electrode in the sensor device. Therefore, there is a need to have a phosphate sensor that overcomes said shortcomings.
Patent application EP 2522993 A1 mentioned an FET device with dual gate stack and extended gate layer. Although there is an extended gate feature in the sensor device, there is no phosphate selective membrane layer or any features for sensing and measuring phosphate ions, thus making the whole invention in EP 2522993 A1 not ideal as a phosphate sensor. In patent application US 8,133,750 B2, one of the embodiments mentioned in the prior art is to have a calcium ion sensing membrane layer deposited on a sensing layer made of titanium element. Said feature is for detecting calcium ions in the solution. Thus, the US 8,133,750 B2 is not suitable to be used as a
phosphate sensor. Furthermore, in US 8,133,750 B2, the conductive wire serves as the extended gate to the sensing film and allows the sensing film to be in contact with the sensing membrane which is in direct contact with the solution. The conductive wire itself may not be able to fully separate the analytes from the FET and therefore cause the FET structure to be more susceptible to damage as some chemical components leach away and come in contact with the FET structure through the sensing membrane.
The inventions in patent application WO 2012/074368 A1 and WO 2012/154028 A1 do not have an extended gate feature, which may increase the chance of the analytes in solution to leach away and make contact with the gate electrode in the FET device. Said occurrence would eventually cause further damage to the FET device. Accordingly, it can be seen in the prior arts that there exists a need to provide an EGFET sensor device that has high sensitivity towards phosphate ions and low tendency of allowing any chemical components to leach away and further damaging the sensor device.
SUMMARY OF THE INVENTION
The invention intends to provide an extended gate field effect transistor (EGFET) sensor device that has low tendency of chemical components leaching away and further damaging the sensor device.
The present invention also provides an EGFET sensor device that may sense phosphate ions based on mixed potential theory of corrosion. Furthermore, the invention provides an ion selective sensing membrane that improves corrosion rate and has a high sensitivity towards phosphate ions in a sample solution.
There is also a feature of the invention that controls the exposure of the ion selective sensing membrane when detecting or measuring phosphate ions in the sample solution.
Accordingly, these objectives may be achieved by following the teachings of the present invention. The present invention relates to an extended gate field effect transistor (EGFET) for sensing phosphate ions in a sample solution, the EGFET comprising: a substrate; a source at one end of the substrate; a drain at the other end of the substrate; an outer circuit wire connecting the source and the drain; a container for holding the sample solution; a reference electrode connected to the outer circuit wire and in contact with the sample solution; and a gate terminal positioned in between the source and the drain; characterised by: an extended gate metallisation layer deposited on top of the gate terminal; a noise reducing layer covering the extended gate metallisation layer; a sensing pad area exposing a part of the extended gate metallisation layer, a phosphate selective alloy membrane deposited in the sensing pad area, wherein the phosphate selective alloy membrane is in contact with the sample solution; and an epoxy dam for controlling the exposure of the phosphate selective alloy membrane.
There is also provided in accordance with an objective of the present invention a method for fabricating an extended gate field effect transistor (EGFET) for sensing phosphate ions in a sample solution, comprising the steps of: preparing a field effect transistor (FET) wafer comprising: a substrate; a source at one end of the substrate; a drain at the other end of the substrate; and a gate terminal positioned in between the source and the drain characterised by the steps of: depositing an extended gate metallisation layer on the gate terminal; depositing a noise reducing layer covering the extended gate metallisation layer; patterning the noise reducing layer to form a sensing pad area; depositing a phosphate selective alloy membrane on the sensing pad area; and creating an epoxy dam by dispensing epoxy at the edge of the sensing pad for controlling the exposure of the phosphate selective alloy membrane.
BRIEF DESCRIPTION OF THE DRAWINGS
The features of the invention will be more readily understood and appreciated from the following detailed description when read in conjunction with the accompanying drawings of the preferred embodiment of the present invention, in which:
Figure 1 shows a drawing of an extended gate field effect transistor (EGFET) for sensing phosphate ions in a sample solution. Figure 2 shows a flowchart of a method for fabricating the EGFET for sensing phosphate ions.
DETAILED DESCRIPTION OF THE INVENTION
The above mentioned and other features and objects of this invention will become more apparent and better understood by reference to the following detailed description. It should be understood that the detailed description made known below is not intended to be exhaustive or to limit the invention to the precise disclosed form as the invention may assume various alternative forms. On the contrary, the detailed description covers all the relevant modifications and alterations made to the present invention, unless the claims expressly state otherwise. The present invention will now be described with reference to Figures 1-2. Referring to Figure 1 , the present invention relates to an extended gate field effect transistor (EGFET) for sensing phosphate ions in a sample solution, the EGFET comprising: a substrate (10); a source (20) at one end of the substrate (10); a drain (25) at the other end of the substrate (10); an outer circuit wire connecting the source (20) and the drain (25); a container (30) for holding the sample solution; a reference electrode (40) connected to the outer circuit wire and in contact with the sample solution; and a gate terminal (50) positioned in between the source (20) and the drain (25); characterised by: an extended gate metallisation layer (60) deposited on top of the gate terminal (50); a noise
reducing layer (70) covering the extended gate metallisation layer (60); a sensing pad area exposing a part of the extended gate metallisation layer (60), a phosphate selective alloy membrane (80) deposited in the sensing pad area, wherein the phosphate selective alloy membrane (80) is in contact with the sample solution; and an epoxy dam (90) for controlling the exposure of the phosphate selective alloy membrane (80).
In an embodiment of the present invention, the extended gate metallisation layer (60) is made of a metallic conductor or a non-metallic conductor. The metallic conductor may further include aluminium, platinum, or copper. The non-metallic conductor may further include graphite, graphene, carbon nanotubes, or conducting polymer.
An embodiment of the present invention describes that the noise reducing layer (70) can be made of any material that is able to prevent light effects, electrostatic discharge, and short circuit related to the use of a transistor. The noise reducing layer (70) may also function as a transistor passivation layer.
In an embodiment of the present invention, the sensing pad area is an area exposing a part of the extended gate metallisation layer (60), so, the base of the sensing pad area is the exposed part of the extended gate metallisation layer (60). The sensing pad area allows the phosphate selective alloy membrane (80) to be in contact with the gate metallisation layer (60) and the sample solution. In another embodiment of the present invention, the phosphate selective alloy membrane (80) is made of a material comprising cobalt, iron, aluminium, vanadium, or chromium. The phosphate selective alloy membrane (80) is preferably made of binary, ternary, quaternary, or quinary alloy. The phosphate selective alloy membrane (80) may be considered as a solid state electrode in the present invention.
The epoxy dam (90) of the present invention is used to control the exposure of the phosphate selective alloy membrane (80) to target analytes in the sample solution. Also shown in Figure 1 , the phosphate selective alloy membrane (80) is not placed directly above the gate terminal (50) which would therefore prevent any possible leaked chemical components from damaging the FET device.
In a preferred embodiment of the present invention, the EGFET sensor device utilises current versus voltage measuring system to measure the current and voltage curves for different phosphate ion concentrations in the sample solution.
As shown in Figure 2, the present invention is also related to a method for fabricating an extended gate field effect transistor (EGFET) for sensing phosphate ions in a sample solution, comprising the steps of: preparing a field effect transistor (FET) wafer (100) comprising: a substrate (10); a source (20) at one end of the substrate (10); a drain (25) at the other end of the substrate (10); and a gate terminal (50) positioned in between the source (20) and the drain (25) characterised by the steps of: depositing an extended gate metallisation layer (60) on the gate terminal (50) (200); depositing a noise reducing layer (70) covering the extended gate metallisation layer (60) (300); patterning the noise reducing layer (70) to form a sensing pad area (400); depositing a phosphate selective alloy membrane (80) on the sensing pad area (500); and creating an epoxy dam (90) by dispensing epoxy at the edge of the sensing pad (600) for controlling the exposure of the phosphate selective alloy membrane (80).
The method of the present invention also includes the step of patterning the extended gate metallisation layer (60) to define the extended gate metallisation layer (60) from the gate terminal (50).
In another embodiment of the present invention, the phosphate selective alloy membrane (80) is deposited during the FET wafer fabrication or at package stage, via hard metal coating process comprising sputtering, e-beam, chemical
vapour deposition (CVD), physical vapour deposition (PVD), or electrochemical deposition.
In an embodiment of the present invention, the EGFET sensor device of the present invention is a potentiometric sensor. Further describing the mode of operation in a potentiometric manner, alloy is capable of sensing phosphate ion via mixed potential theory of corrosion. The mechanism of mixed potential theory of corrosion occurs when a non-equilibrium state exists at the surface of a working electrode involving two or more electrochemical reactions. There may be two electrodes in the present invention: the reference electrode (40) and the working electrode which is the phosphate selective alloy membrane (80). In said reaction, slow oxidation of alloy and simultaneous reduction of both oxygen and alloy ions occur on the surface of the working electrode. As a result, alloy dissolves and alloy oxide film is formed. When phosphate is present in the sample solution, alloy phosphate is formed on the surface of the working electrode, depending on the pH solution. These coupled reactions show a shift in the equilibrium potential that is dependent on oxidation of alloy, reduction of oxygen and precipitation of alloy phosphate on the surface of the working electrode. This leads to the mixed potential leaning towards negative shift, while keeping other factors constant. The shift will then be related to the phosphate concentration since equilibrium potentials are governed by Nernst equation. By combining with an FET transistor as per the embodiment of the present invention, the EGFET phosphate sensor device using mixed potential theory of corrosion may be realised.
Although the present invention has been described with reference to specific embodiments, it will be apparent for those skilled in the art that many variations and modifications can be done within the scope of the invention as described in the specification and defined in the following claims.
Claims
An extended gate field effect transistor (EGFET) for sensing phosphate ions in a sample solution, the EGFET comprising:
a) a substrate (10);
b) a source (20) at one end of the substrate (10);
c) a drain (25) at the other end of the substrate (10);
d) an outer circuit wire connecting the source (20) and the drain (25); e) a container (30) for holding the sample solution;
f) a reference electrode (40) connected to the outer circuit wire and in contact with the sample solution; and
g) a gate terminal (50) positioned in between the source (20) and the drain (25);
characterised by:
h) an extended gate metallisation layer (60) deposited on top of the gate terminal (50);
i) a noise reducing layer (70) covering the extended gate metallisation layer (60);
j) a sensing pad area exposing a part of the extended gate metallisation layer (60),
k) a phosphate selective alloy membrane (80) deposited in the sensing pad area, wherein the phosphate selective alloy membrane (80) is in contact with the sample solution; and
I) an epoxy dam (90) for controlling the exposure of the phosphate selective alloy membrane (80).
An extended gate field effect transistor (EGFET) according to claim 1 , wherein the extended gate metallisation layer (60) is made of a metallic conductor or a non-metallic conductor.
An extended gate field effect transistor (EGFET) according to claim 1 , wherein the phosphate selective alloy membrane (80) is made of a material comprising cobalt, iron, aluminium, vanadium, or chromium.
An extended gate field effect transistor (EGFET) according to claim 1 , wherein the phosphate selective alloy membrane (80) is made of binary, ternary, quaternary, or quinary alloy.
A method for fabricating an extended gate field effect transistor (EGFET) for sensing phosphate ions in a sample solution, comprising the steps of: a) preparing a field effect transistor (FET) wafer (100) comprising: i) a substrate (10);
ii) a source (20) at one end of the substrate (10);
iii) a drain (25) at the other end of the substrate (10); and iv) a gate terminal (50) positioned in between the source (20) and the drain (25);
characterised by the steps of:
b) depositing an extended gate metallisation layer (60) on the gate terminal (50) (200);
c) depositing a noise reducing layer (70) covering the extended gate metallisation layer (60) (300);
d) patterning the noise reducing layer (70) to form a sensing pad area (400);
e) depositing a phosphate selective alloy membrane (80) on the sensing pad area (500); and
f) creating an epoxy dam (90) by dispensing epoxy at the edge of the sensing pad (600) for controlling the exposure of the phosphate selective alloy membrane (80).
A method according to claim 5 further comprising the step of patterning the extended gate metallisation layer (60) to define the extended gate metallisation layer (60) from the gate terminal (50).
A method according to claim 5, wherein the extended gate metallisation layer (60) is made of a metallic conductor or a non-metallic conductor.
8) A method according to claim 5, wherein the phosphate selective alloy membrane (80) is made of a material comprising cobalt, iron, aluminium, vanadium, or chromium.
A method according to claim 5, wherein the phosphate selective alloy membrane (80) is made of binary, ternary, quaternary, or quinary alloy.
A method according to claim 5, wherein the phosphate selective alloy membrane (80) is deposited during the FET wafer fabrication or at package stage, via hard metal coating process comprising sputtering, e- beam, chemical vapour deposition (CVD), physical vapour deposition (PVD), or electrochemical deposition.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| MYPI2014702426 | 2014-08-28 | ||
| MYPI2014702426 | 2014-08-28 |
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| WO2016032314A1 true WO2016032314A1 (en) | 2016-03-03 |
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| CN108802125A (en) * | 2018-08-28 | 2018-11-13 | 长沙理工大学 | The detection method and sensor of L-cysteine based on seven (6- sulfydryls -6- deoxidations)-beta-cyclodextrins |
| CN109030583A (en) * | 2018-08-28 | 2018-12-18 | 长沙理工大学 | The detection method and sensor of L-cysteine based on 2-mercaptobenzimidazole |
| CN109115846A (en) * | 2018-08-28 | 2019-01-01 | 长沙理工大学 | A kind of detection method and sensor of the l-cysteine based on 3- mercaptopropionic acid modification grid gold electrode |
| WO2021050867A1 (en) * | 2019-09-13 | 2021-03-18 | University Of Florida Research Foundation | Combined electrochemical phosphate/ph sensors and systems |
| US11959875B2 (en) | 2017-08-11 | 2024-04-16 | Uwm Research Foundation, Inc. | Composition, electrode, and fabrication method for phosphate sensing |
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