TWI903545B - Biosensor device and method of manufacturing the same - Google Patents

Abstract

A biosensor device is provided in the present invention, including a first insulating layer on a substrate, a conductive layer on the first insulating layer and including multiple small first conductive parts and a large second conductive part, a second insulating layer covering on the conductive layer, an electrode layer on the second insulating layer and including multiple small first electrodes and a large second electrode, and each of the first electrodes corresponds to one of the first conductive parts, and multiple vias in the second insulating layer between the conductive layer and the electrode layer, and each of the first electrodes is electrically connected with one of the corresponding first conductive parts through one of the vias.

Description

Biosensing elements and their manufacturing methods

This invention relates generally to a biosensing element and a method for manufacturing the same, and more specifically, to a biosensing element using nanoelectrodes and an electrochemical reaction mechanism and a method for manufacturing the same.

A biosensor is a device used to detect various biomarkers produced by living organisms, such as nucleic acids, cells/bacteria, antibodies/antigens, enzymes, or metal ions carried in blood or bodily fluids. Its sensing principle involves using specific bioreceptors to bind and react with their corresponding bioactive substances. The biomarker is detected by analyzing the physical and/or chemical reactions that occur during the sensing process. Common biosensing methods include electrochemical sensing, optical sensing, and surface acoustic wave sensing, which are widely used in pharmaceuticals, biotechnology, food, agriculture, and environmental monitoring.

Biosensors contain transducers (or sensors) or components that convert the sensed biosignals/energy into the signals to be detected. Taking a blood glucose meter as an example, glucose in the blood reacts with enzyme receptors on the sensor to produce a biochemical reaction. The electrodes, acting as transducers, convert these biochemical reactions into corresponding electrical signals. These electrical signals can be transmitted to external electronic interfaces such as sensing circuits for data analysis, thus obtaining the blood glucose value to be measured.

Today, the industry has combined microelectromechanical systems (MEMS) and semiconductor technology to develop revolutionary biosensor chips using nanoelectrodes (such as nanowires or microparticles). These chips offer advantages such as low sample requirements, fast mass transfer, and low interfacial capacitance, particularly in molecular and cellular diagnosis and treatment, and have significant application potential in the medical field. However, stability is a crucial consideration for biosensors. The sensitivity of the sensing system to internal and external environmental interference determines whether signal instability during sensing will lead to misreadings, thus affecting the accuracy of the measurement. In particular, nanoelectrodes are highly sensitive to the electric field within the system during sensing, and the sensing results are easily affected by the concentration and uneven distribution of the electric field. Therefore, those skilled in the art must improve the electrode design of existing biosensors to solve the above problems.

In view of the shortcomings of the existing technology, the present invention proposes a novel biosensing element and its manufacturing method. The feature is that there is a certain distance between the electrode of the sensing end and the power supply line. This can avoid the influence of electric field concentration or uneven distribution on the electrode, making the sensing more stable and accurate. In addition, it can also avoid the corrosion of the conductive line below due to etching in the manufacturing process.

One aspect of this invention is to provide a biosensing element, the structure of which includes: a substrate; a first insulating layer disposed on the substrate; a conductive layer disposed on the first insulating layer, the conductive layer including a plurality of first conductive portions and a second conductive portion, wherein the area of the second conductive portion is larger than the area of each of the first conductive portions; a second insulating layer covering the conductive layer; and an electrode layer disposed on the second insulating layer, the electrode layer covering... It includes multiple first electrodes and a second electrode, the area of the second electrode being larger than the area of each of the first electrodes, and each of the first electrodes corresponding to a second conductive portion; and multiple vias located in the second insulating layer between the conductive layer and the electrode layer, the second electrodes being electrically connected to the second conductive portion through the vias, and each of the first electrodes being electrically connected to a corresponding first conductive portion through a via.

Another aspect of this invention is to provide a method for manufacturing a biosensing element, the steps of which include: providing a substrate; sequentially forming a first insulating layer and a conductive layer on the substrate; performing a first photolithography process to pattern the conductive layer, forming a plurality of first conductive portions and a second conductive portion, wherein the area of the second conductive portion is larger than the area of each of the first conductive portions; and forming a second insulating layer on the first insulating layer and the conductive layer. A plurality of vias are formed in the second insulating layer, the vias being exposed from the second insulating layer, and each of the first conductive portions is electrically connected to a via; and an electrode layer is formed on the second insulating layer, wherein the electrode layer includes a plurality of first electrodes and a second electrode, the area of the second electrode being larger than the area of each of the first electrodes, and each of the first electrodes being electrically connected to a corresponding first conductive portion through a via.

These and other purposes of the present invention should become more apparent to the reader after reading the details of the preferred embodiments described below with various illustrations and diagrams.

Exemplary embodiments of the present invention will now be described in detail below, with reference to the accompanying drawings illustrating the described features to enable the reader to understand and achieve the technical effects. The reader will understand that the descriptions herein are by way of illustration only and are not intended to limit the scope of the invention. Various embodiments of the invention and the non-conflicting features thereof can be combined or rearranged in various ways. Modifications, equivalents, or improvements to the invention are understandable to those skilled in the art without departing from the spirit and scope of the invention and are intended to be included within the scope of the invention.

Readers should easily understand that the meanings of "on," "above," and "above" in this case should be interpreted broadly, so that "on" not only means "directly on" something but also includes something with an intermediary feature or layer, and "above" or "above" not only means "above" or "above" something but can also include something "above" or "above" without an intermediary feature or layer (i.e., directly on something). In addition, for ease of description, spatial terms such as "below," "under," "lower part," "above," and "upper part" may be used in this article to describe the relationship between one element or feature and one or more other elements or features, as shown in the accompanying figure.

As used herein, the term "substrate" refers to the material on which subsequent materials are added. The substrate itself can be patterned. The material added on top of the substrate can be patterned or left unpatterned. Furthermore, the substrate can include a wide range of semiconductor materials, such as silicon, germanium, gallium arsenide, indium phosphide, etc. Alternatively, the substrate can be made of non-conductive materials such as glass, plastic, or sapphire wafers.

As used herein, the term "layer" refers to a portion of material comprising a region of thickness. A layer may extend over the entirety of a structure below or above it, or may have a range smaller than that of the structure below or above. Furthermore, a layer may be a region of a homogeneous or heterogeneous continuous structure with a thickness less than the thickness of the continuous structure. For example, a layer may be located between the top and bottom surfaces of a continuous structure or between any horizontal planes at the top and bottom surfaces. A layer may extend horizontally, vertically, and/or along an inclined surface. A substrate may be a layer, which may include one or more layers, and/or may have one or more layers on, above, and/or below it. A layer may include multiple layers. For example, an interconnect layer may include one or more conductor and contact layers (where contacts, interconnects and/or vias are formed) and one or more dielectric layers.

Readers can generally understand terms at least partially from their usage in context. For example, depending at least partially on the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in a singular sense, or to describe a combination of features, structures, or characteristics in a plural sense. Similarly, depending at least partially on the context, terms such as "a," "an," "the," or "the" can also be understood to convey either a singular or a plural usage. Furthermore, the term "based on" can be understood not necessarily to convey an exclusive set of factors, but rather to allow for additional factors that are not necessarily explicitly described, which also depends at least partially on the context.

Readers will further understand that when words such as "comprising" and/or "containing" are used in this specification, they expressly define the presence of the stated features, areas, wholes, steps, operations, elements, and/or components, but do not preclude the possibility of the presence or addition of one or more other features, areas, wholes, steps, operations, elements, components, and/or combinations thereof.

In the following embodiments, the present invention provides a detailed structure and related manufacturing method of a biosensing element for use in a biosensor, particularly focusing on the electrode as a transducer component. It should be noted that although the embodiments use an electrochemical biosensing mechanism as an example, the present invention is not limited thereto. Any biosensor with a sensing electrode component can apply the concepts and ideas of the present invention, the scope of which will be defined by the appended patent claims.

The following embodiments will now describe the steps for manufacturing the biosensing element 100 of the present invention with reference to the cross-sectional schematic diagrams in Figures 1 to 9.

First, please refer to Figure 1. At the beginning of the manufacturing process, a substrate 102 is provided as the basis for the entire biosensor 100. The substrate 102 may be a silicon substrate, and may also contain, but is not limited to, other semiconductor materials, such as gallium nitride (GaN), silicon carbide (SiC), silicon germanium (SiGe), germanium, or combinations thereof. Next, a first insulating layer 104 is formed on the substrate 102 to give the biosensor subsequently fabricated thereon good insulating properties. In this embodiment of the invention, the first insulating layer 104 can be formed by atomic layer deposition (ALD), physical vapor deposition (PVD), chemical vapor deposition (CVD), chemical oxidation, thermal oxidation, and/or other suitable methods. The material may include, but is not limited to, oxides, nitrides, oxynitrides, or combinations thereof, such as silicon oxide, silicon nitride, silicon oxynitride, or low-k dielectric materials. The thickness of the first insulating layer 104 is approximately 6000 angstroms (Å).

Please refer to Figure 2. After the first insulating layer 104 is formed, a lower barrier layer 106, an intermediate conductive layer 108, and an upper barrier layer 110 are sequentially formed on the first insulating layer 104 to serve as conductive lines for the biosensing element 100, collectively referred to as conductive layers. The lower barrier layer 106, the intermediate conductive layer 108, and the upper barrier layer 110 can be formed by PVD, CVD, electron beam evaporation, sputtering, electroplating, and/or other suitable methods. The intermediate conductive layer 108 may be made of materials with good conductivity, including but not limited to titanium (Ti), nickel (Ni), silver (Ag), aluminum (Al), copper-aluminum alloy (AlCu), copper-aluminum-silicon alloy (AlSiCu), or combinations thereof. It serves as the main body of the conductive path and has a thickness of approximately 4000 angstroms (Å). The lower barrier layer 106 and the upper barrier layer 110 may be made of titanium nitride (TiN) and have a thickness of approximately 200 Å, which can prevent the metal components in the intermediate conductive layer 108 from diffusing and contaminating the surrounding dielectric layer. It should be noted that in other embodiments, the above-described conductive path may not have a lower barrier layer 106 and/or an upper barrier layer 110, depending on the requirements of the invention.

Referring again to Figure 2, after the lower barrier layer 106, the intermediate conductive layer 108, and the upper barrier layer 110 are formed, a first photolithography process is performed to pattern the above-mentioned layer structure, thus forming multiple smaller first conductive portions 112a and a larger second conductive portion 112b. It should be noted that in this embodiment of the invention, the first conductive portions 112a and the second conductive portions 112b are not actual electrodes in contact with the biological receptor and the test object, but rather the conductive lines corresponding to these electrodes, which are also the locations of the high-intensity electric field during sensing. In this embodiment of the invention, the aforementioned first conductive portions 112a and second conductive portions 112b can be integrated into a typical back-end semiconductor process (BEOL) and fabricated together with interconnect metal layers. The first conductive part 112a and the second conductive part 112b are further connected to the sensing circuit (not shown) of the biosensor to transmit the sensed electrical signal to the signal processing unit in the external electronic device or interface for matching and amplification processing, thus converting it into an interface that can be read by humans.

Please refer to Figure 3. After the first conductive portion 112a and the second conductive portion 112b are formed, a second insulating layer 114 is then formed on the first insulating layer 104, the first conductive portion 112a, and the second conductive portion 112b. The second insulating layer 114 covers the first conductive portion 112a and the second conductive portion 112b and fills the gaps between them. In this embodiment of the invention, the second insulating layer 114 can be a metal intermetallic dielectric (IMD) layer in a typical back-end semiconductor process (BEOL), which can be formed by PECVD, CVD, and/or other suitable methods. Its material can include, but is not limited to, silicon oxide, silicon nitride, silicon oxynitride, or tetraethoxysilane (TEOS). After the second insulating layer 114 is formed, a chemical mechanical planarization (CMP) process can be performed to provide a flat process surface.

Please refer to Figure 4. After the second insulating layer 114 is formed, a plurality of vias 116 are then formed in the second insulating layer 114. As shown in the figure, these vias 116 are exposed from the second insulating layer 114, and each first conductive portion 112a is electrically connected to a corresponding via 116, while the second conductive portion 112b can be electrically connected to the plurality of vias 116. In this embodiment of the invention, the via 116 can be an interconnecting metal part in a typical semiconductor back-end process (BEOL). Its material can be tungsten (W) or copper (Cu). The via can be formed by filling a pre-formed via with the material through PVD, CVD, electron beam evaporation, sputtering, electroplating, and/or other suitable methods, followed by a CMP process to remove the portion of the via located on the surface of the second insulating layer 114. Thus, the top surface of the formed via 116 is substantially flush with the surrounding surface of the second insulating layer 114. The length of the via 116 can be 6000 Å, approximately the same as the thickness of the surrounding second insulating layer 114.

Please refer to Figure 5. After the via 116 is formed, an electrode layer 118a, 118b is then formed on the second insulating layer 114 and the vias 116 to serve as the electrode terminals of the biosensing element 100. The electrode layers 118a, 118b can also be formed by PVD, CVD, electron beam evaporation, sputtering, electroplating and/or other suitable methods, with a thickness of approximately 2000 angstroms (Å), and the material may include, but is not limited to, titanium nitride (TiN), silver (Ag), gold (Au), platinum (Pt), carbon (C), calomel, etc. In this embodiment of the invention, after the electrode layer is formed, a photolithography process is performed to pattern it into multiple smaller first electrodes 118a and a larger second electrode 118b. Each of the first electrodes 118a can be connected to a corresponding lower first conductive portion 112a through a via 116, and each of the second electrodes 118b can be connected to a corresponding lower second conductive portion 112b through at least one via 116.

In this embodiment of the invention, the first electrode 118a is preferably a working electrode, such as a nanoelectrode, which can be neatly and uniformly arranged on the surface of the measurement area of the second insulating layer 114 in the form of nanodots or nanowires. The second electrode 118b is preferably a counter electrode (also known as an auxiliary electrode) or a reference electrode, and is not limited to a two-electrode or three-electrode sensing system. In this embodiment of the invention, taking electrochemical sensing as an example, the first electrode 118a can act as an electron provider or electron receiver under appropriate voltage conditions in an electrolyte environment, and preferably has a high signal-to-noise ratio and a wide potential window range. In practice, the first electrode 118a is designed to connect to the corresponding bioreceptor of the analyte to receive the electrical signal generated during its reaction, while the second electrode 118b plays a corresponding role to the first electrode 118a. For example, in a redox detection system, when the first electrode 118a undergoes an oxidation reaction, the second electrode 118b undergoes a reduction reaction, and vice versa. The second electrode 118b generally does not participate in the electrochemical reaction, but only provides a charge balancing function. Its characteristics are superior, exhibiting high stability and high conductivity, thereby completing the reaction electron circuit. In this embodiment of the invention, the horizontal area of the second electrode 118b is much larger than that of the first electrode 118a, for example, more than 10 times larger, to ensure the complete functionality and rapid operation of the electronic circuit as much as possible. Furthermore, in this embodiment of the invention, the aforementioned electrode layers preferably correspond to the conductive layer portion below them. More specifically, each first electrode 118a corresponds to and overlaps with a first conductive portion 112a below it. The second electrode 118b corresponds to and overlaps with a second conductive portion 112b below it. Similar to the electrode layers 118a and 118b, the horizontal area of the second conductive portion 112b is much larger than the horizontal area of the first conductive portion 112a.

The advantage of the above design of this invention is that the electrode terminals that contact the object under test, such as the first electrode 118a and the second electrode 118b, are far from the conductive layer that provides the electric field, such as the first conductive portion 112a and the second conductive portion 112b, and the two are connected through the via 116. In this way, when the sensor is operating, the sensitive nanoelectrodes can avoid being affected by the uneven electric field near the conductive layer, especially the electric field concentration at the corner of the conductive layer, which could lead to misreading and affect the accuracy and stability of the sensing. This is an effect that cannot be achieved by the prior art approach of directly placing the electrode layer on the conductive layer. In addition, the above design can also avoid damaging the underlying conductive layer when defining the electrode pattern in the photolithography process, causing its metal material to be exposed and damaged, or even corroded.

Furthermore, this invention uses semiconductor manufacturing processes to pattern the conductive layer into first conductive portions 112a and second conductive portions 112b corresponding to the first electrode 118a and the second electrode 118b above. In this way, each electrode can be provided with an independent electric field and perform specific detection actions. This design is beneficial for dividing the sensing area into multiple independent sensing zones in the same sensing system, and setting the function of each zone as needed to achieve multiplexing detection. For example, in diagnosing diarrhea, common causes of diarrhea may include pathogens such as bacteria, rotavirus, norovirus, adenovirus, and enterovirus. By dividing the detection area into different independent detection zones to detect these pathogens, and placing corresponding biological receptors on the electrodes in these zones, the effect of simultaneous multiplexing can be achieved using only the same pathogen sample. This is something that is difficult to achieve in conventional techniques where all electrodes share a single conductive layer.

Please refer to Figure 6. After the first electrode 118a and the second electrode 118b are formed, a first protective layer 120 and a second protective layer 122 are sequentially formed on the electrodes and the second insulating layer 114 to protect the electrodes. In this embodiment of the invention, the first protective layer 120 and the second protective layer 122 can be formed by ALD, PVD, CVD and/or other suitable methods. The material of the first protective layer 120 can be silicon nitride, with a thickness of about 1000 Å, and it is conformally formed on the electrode. The material of the second protective layer 122 preferably has a significant etch selectivity ratio with the material of the first protective layer 120, such as silicon oxide, which covers and fills the space between the electrodes. It should be noted that, as shown in the figure, because the second electrode 118b is a bulk electrode, the top height of the second protective layer 122 deposited on it will be higher than the top height of the second protective layer 122 on the first electrode 118a.

Please refer to Figure 7. After the first protective layer 120 and the second protective layer 122 are formed, a photolithography process is performed to pattern the second protective layer 122 to define the pattern of the second electrode to be exposed later. In this step, the second protective layer 122 directly above the second electrode 118b is removed, exposing part of the first protective layer 120. Because the height of the second protective layer 122 on the second electrode 118b is greater than the height of the second protective layer 122 on the first electrode 118a, after this step, the second protective layer 122 will have a protrusion 122a at the boundary between the edge of the second electrode 118b and the adjacent edge of the first electrode 118a.

Please refer to Figure 8. After exposing the first protective layer 120 on the second electrode 118b, an etching process is then performed to remove a certain thickness of the second protective layer 122 and the first protective layer 120, thus exposing the first electrode 118a and the second electrode 118b. In this step, the first protective layer 120 exposed on the second electrode 118b is completely removed, and the second protective layer 122 and the first protective layer 120 on the top surface of the first electrode 118a are also completely removed, thus exposing the first electrode 118a. In the space between the electrodes, portions of the first protective layer 120 and the second protective layer 122 remain to protect the electrode sidewalls. The via 116 exposed below the first electrode 118a is also protected by the first protective layer 120. Furthermore, after this step, the first protective layer 120 and the second protective layer 122 will also have a protrusion 123 at the boundary where the edge of the second electrode 118b is adjacent to the first electrode 118a. It should be noted that in this embodiment, the first electrode 118a, serving as the working electrode, is designed to slightly protrude from the surrounding surfaces of the first protective layer 120 and the second protective layer 122, for example, by a height of 30 nm. The protruding first electrode 118a allows for a wider electric field coverage, which helps improve the efficiency of electrochemical reactions, thereby increasing signal strength and sensitivity. This enables the nanoelectrode to have better three-dimensional biosensing capabilities.

Please refer to Figure 9. After exposing the first electrode 118a and the second electrode 118b, a bioreceptor 124, such as an enzyme, antibody/antigen, nucleic acid, bacteria, or cell, is then placed on the first electrode 118a, which serves as the working electrode. This bioreceptor can be in the form of a bioprobe, and its main function is to provide a specific binding or reaction between the sensor and the analyte 126. The analyte 126 can be a bioactive substance, and the bioreceptor 124 will have a specific affinity for the specific active analyte 126. Taking blood glucose measurement as an example, the analyte 126 is glucose. By measuring the concentration of glucose in the blood, it can be determined whether the subject's blood glucose level is within the normal range. The test uses enzymes specific to glucose as biological acceptors, such as glucose oxidase (GOx), which binds to glucose in the blood sample. In the glucose catalysis process, oxygen is the co-matrix for glucose oxidase, allowing GOx to catalyze glucose, leading to the formation of gluconolactone and the production of hydrogen peroxide as a byproduct. Thus, the first electrode 118a and the second electrode 118b can play the roles of oxidation/reduction electrodes respectively during the detection process. For example, the cathode terminal will undergo dissolved oxygen reduction reaction. The reduction current signal during dissolved oxygen can be detected through the electrode, and the measured current signal is transmitted to the external sensing circuit and electronic equipment through the via 116 and the conductive layers 112a and 112b for signal matching, amplification and calculation processing. In this way, the blood glucose concentration can be determined.

It should be noted that the detection mechanism described above is only an example. In practice, different reaction mechanisms and/or different bioreceptors 124 may be used for the measurement of the same or different analytes 126. Therefore, the electrode design of this invention can be applied to any biochemical reaction that is generated or triggered in the sensing process, which can cause the electrode part in the biosensor to generate a corresponding electronic signal, including current-based, potential-based, or impedance-based sensing methods.

Based on the above description of the embodiments, the present invention provides a biosensing element, the structure of which includes a substrate 102, a first insulating layer 104 disposed on the substrate 102, a conductive layer disposed on the first insulating layer 104, the conductive layer including a plurality of first conductive portions 112a and a second conductive portion 112b, the area of the second conductive portion 112b being larger than the area of each of the first conductive portions 112a, a second insulating layer 114 covering the conductive layer, and an electrode layer disposed on the second insulating layer 114, the electrode layer including a plurality of first conductive portions 112a and a second conductive portion 112b covering the conductive layer. An electrode 118a and a second electrode 118b are provided, the area of the second electrode 118b being larger than the area of each of the first electrodes 118a. Each of the first electrodes 118a corresponds to a first conductive portion 112a. A plurality of vias 116 are located in a second insulating layer 114 between the conductive layer and the electrode layer. The second electrode 118b is electrically connected to the second conductive portion 112b through the vias 116, and each first electrode 118a is electrically connected to its corresponding first conductive portion 112a through a via 116. The above description is merely a preferred embodiment of the present invention. All equivalent variations and modifications made within the scope of the patent application of this invention shall fall within the scope of the present invention.

100: Biosensor 102: Substrate 104: First Insulation Layer 106: Lower Barrier Layer 108: Intermediate Conductive Layer 110: Upper Barrier Layer 112a: First Conductive Part 112b: Second Conductive Part 114: Second Insulation Layer 116: Through-hole 118a: First Electrode 118b: Second Electrode 120: First Protective Layer 122: Second Protective Layer 122a: Protrusion 124: Bioreceptor 126: Analyte

This specification includes accompanying drawings, which form part of the document and provide the reader with a further understanding of the embodiments of the invention. These drawings illustrate some embodiments of the invention and, together with the description herein, explain its principles. In these drawings: Figures 1 through 9 are schematic cross-sectional views of the fabrication process of a biosensing element according to embodiments of the invention. It should be noted that all figures in this specification are illustrative in nature. For clarity and ease of explanation, the dimensions and scale of the components in the figures may be exaggerated or reduced. Generally, the same reference symbols in the figures are used to indicate corresponding or similar component features in modified or different embodiments.

100: Biosensor Element

102: Base

104: First Desperate Layer

112a: First conductive part (conductive layer)

112b: Second conductive part (conductive layer)

114: Second Insulation Layer

116: Guide hole component

118a: First electrode (electrode layer)

118b: Second electrode (electrode layer)

120: First layer of protection

122: Second protective layer

124: Biological receptors

126: Item to be tested

Claims (20)

A biosensing element includes: a substrate; a first insulating layer disposed on the substrate; a conductive layer disposed on the first insulating layer, the conductive layer including a plurality of first conductive portions and a second conductive portion, the area of the second conductive portion being larger than the area of each of the first conductive portions; a second insulating layer covering the conductive layer; an electrode layer disposed on the second insulating layer, the electrode layer including a plurality of first electrodes and a second electrode, the area of the second electrode being larger than the area of each of the first electrodes, and each of the first electrodes corresponding to a first conductive portion; and Multiple vias are located in the second insulating layer between the conductive layer and the electrode layer. The second electrode is electrically connected to the second conductive portion through the vias, and each first electrode is electrically connected to a corresponding first conductive portion through one of the vias. The biosensing element as described in claim 1 further includes a first protective layer located on the electrode layer and the second insulating layer and exposing the first electrode and the second electrode. The biosensing element as described in claim 2 further includes a second protective layer located on the first protective layer and exposing the first electrodes and the second electrodes. The biosensing element as described in claim 3, wherein the exposed top surfaces of the first electrodes are higher than the top surfaces of the first protective layer and the second protective layer surrounding the first electrodes. The biosensing element as described in claim 3, wherein the first protective layer and the second protective layer have a protrusion at the edge of the second electrode. The biosensing element as described in claim 1, wherein the conductive layer comprises an intermediate conductive layer and an upper barrier layer and a lower barrier layer located on the upper and lower surfaces of the intermediate conductive layer. The biosensing element as described in claim 1, wherein the second electrode is a counter electrode. The biosensing element as described in claim 1, wherein the first electrode is a working electrode. The biosensing element as described in claim 1, wherein the first electrode and the first conductive portion overlap in a direction perpendicular to the substrate. The biosensing element as described in claim 1, wherein the second electrode and the second conductive portion overlap in a direction perpendicular to the substrate. The biosensing element as described in claim 1 further includes at least one bioreceptor connected to each of the first electrodes. A method for fabricating a biosensor includes: providing a substrate; sequentially forming a first insulating layer and a conductive layer on the substrate; patterning the conductive layer using a first photolithography process to form a plurality of first conductive portions and a second conductive portion, wherein the area of the second conductive portion is larger than the area of each of the first conductive portions; forming a second insulating layer on the first insulating layer and the conductive layer; forming a plurality of vias in the second insulating layer, the vias being exposed from the second insulating layer, and each of the first conductive portions being electrically connected to a via; and An electrode layer is formed on the second insulation layer, wherein the electrode layer includes a plurality of first electrodes and a second electrode, the area of the second electrode being larger than the area of each of the first electrodes, and each of the first electrodes being electrically connected to a corresponding first conductive portion through a via. The method for manufacturing a biosensor as described in claim 12 further comprises: After the electrode layer is formed, sequentially forming a first protective layer and a second protective layer on the electrode layer and the second insulating layer; performing a second photolithography process to pattern the second protective layer, thereby removing the portion of the second protective layer directly above the second electrode, exposing a portion of the first protective layer; performing an etch-back process to remove portions of the first and second protective layers, thereby exposing the first and second electrodes. As described in the method for manufacturing a biosensing element according to claim 13, the top surface of the second protective layer on the second electrode is higher than the top surface of the second protective layer on the first electrodes, so that after the second photolithography process is performed, the second protective layer will have a protrusion at the edge of the second electrode. The method of manufacturing a biosensing element as described in claim 13, wherein the exposed top surfaces of the first electrodes are higher than the top surfaces of the first protective layer and the second protective layer surrounding the first electrodes. The method for manufacturing a biosensing element as described in claim 12, wherein the conductive layer comprises an intermediate conductive layer and an upper barrier layer and a lower barrier layer located on the upper and lower surfaces of the intermediate conductive layer. The method of manufacturing a biosensing element as described in claim 12, wherein the second electrode is a counter electrode. The method for manufacturing a biosensing element as described in claim 12, wherein the first electrode is a working electrode. The method of manufacturing a biosensing element as described in claim 12, wherein the first electrode and the first conductive portion overlap in a direction perpendicular to the substrate. The method of manufacturing a biosensing element as described in claim 12, wherein the second electrode and the second conductive portion overlap in a direction perpendicular to the substrate.