Ion-sensitive thin-film transistor and biosensor chip
By designing an ion-sensitive thin-film transistor with a dual-gate structure and using an etch-blocking layer as the top gate insulating layer, the gate capacitance coupling ratio is improved, solving the problem of low sensitivity in traditional thin-film transistors. This enables rapid and highly sensitive detection of low-concentration target nucleic acid sequences, making it suitable for various biological detection methods.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI JIAOTONG UNIV
- Filing Date
- 2023-07-06
- Publication Date
- 2026-06-19
Smart Images
Figure CN116936640B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electronic device technology, specifically to an ion-sensitive thin-film transistor and a biosensor chip. Background Technology
[0002] Ion-sensitive field-effect transistors (ISFETs), as a type of traditional field-effect transistor (FET), have an ion-sensitive film covering the surface of the dielectric layer. The sensitive film of an ISFET is in contact with the electrolyte and is highly sensitive to the ion concentration of the solution. ISFET-based biosensors are sensitive to the amount of charge accumulated at the semiconductor-dielectric interface, causing a modulation effect on the transistor's threshold voltage. This ion sensitivity allows ISFETs to convert and amplify pH changes resulting from biochemical reactions in the electrolyte into electrical signals. The development of field-effect sensors based on IGZO (In-Ga-Zn-O) thin-film transistors (TFTs) has attracted attention due to their ease of fabrication and compatibility with flexible substrates, making them a promising alternative to traditional silicon-based ISFETs.
[0003] Due to the nature of the reaction process causing pH changes in the solution environment, loop-mediated isothermal amplification (LAMP) technology has been used to construct ISFET-based biosensing platforms. Based on the sensor's high sensitivity to pH, target nucleic acid sequences can be detected indirectly. The specificity of detection is determined by the specific amplification of the target sequence by LAMP. Immobilization methods in transistor-based biosensors simplify the biofunctionalization process, reduce costs, and provide label-free and real-time monitoring capabilities for biochemical reactions, making them a promising universal platform for biosensing.
[0004] Existing thin-film transistor structures such as Figure 1 As shown, although ISFET-based pH sensors have been on the market for a long time, the commercialization of this type of biosensor is limited by its low pH sensitivity, with a maximum pH value of 59 mV / pH (Nernst limit). Since the pH change caused by the LAMP reaction is small, the low pH sensitivity hinders the need for rapid, low-concentration sample detection in biosensors. Therefore, it is necessary to propose a new device solution. The IGZO TFTs used in traditional display panels can be designed as dual-gate devices, utilizing an etch-stop / passivation layer (ESL / PA) as the top gate insulating layer. However, its capacitance is smaller than that of bottom-gate devices, thus reducing sensitivity. Furthermore, the passivation layer (PA) is placed above the relatively thick source / drain electrodes, and its locally formed microstructure contains steep sidewalls, which can easily cause solution leakage upon contact with the test solution, leading to device failure. Summary of the Invention
[0005] In view of the deficiencies in the prior art, the purpose of this invention is to provide an ion-sensitive thin-film transistor and a biosensor chip to solve at least one of the above-mentioned problems.
[0006] According to one aspect of the present invention, an ion-sensitive thin-film transistor is provided, comprising:
[0007] Substrate;
[0008] A first gate electrode is disposed on the substrate;
[0009] A first gate insulating layer is disposed on the first gate electrode and the substrate;
[0010] A semiconductor layer is disposed on the first gate insulating layer opposite to the first gate electrode;
[0011] A second gate insulating layer is disposed on the semiconductor layer and is shorter than the semiconductor layer. The second gate insulating layer is recessed on both sides to expose the electrode contact area.
[0012] Source and drain electrodes are disposed on both sides of the semiconductor layer, and the source and drain electrodes are respectively in contact with the first gate insulating layer, the semiconductor layer and the second gate insulating layer;
[0013] The second gate electrode is disposed above the second gate insulating layer and is kept at a distance from the source and drain electrodes on both sides;
[0014] The second gate contact electrode is connected to the upper surface of the second gate electrode;
[0015] The first gate electrode, the first gate insulating layer, the source and drain electrodes, and the semiconductor layer constitute a bottom-gate transistor located at the bottom, serving as a switching device;
[0016] The source / drain electrodes, the semiconductor layer, the second gate insulating layer, the second gate electrode, and the second gate contact electrode constitute a top-gate transistor, serving as an ion-sensitive element. The second gate insulating layer is an etch barrier layer.
[0017] The top-gate transistor and the bottom-gate transistor constitute an ion-sensitive thin-film transistor with a dual-gate structure.
[0018] Optionally, the gate capacitance of the top gate transistor is greater than the gate capacitance of the bottom gate transistor.
[0019] Optionally, the transistor further includes a passivation layer disposed above the transistor, wherein the passivation layer has a first via in the region corresponding to the second gate contact electrode.
[0020] Optionally, the transistor further includes an interlayer dielectric layer disposed above the passivation layer; the portion of the second gate contact electrode on the interlayer dielectric layer is an ion-sensitive electrode.
[0021] The interlayer dielectric layer has a second via in the region directly opposite the first via, and the second gate contact electrode is connected to the upper surface of the second gate electrode through the second via.
[0022] Optionally, the transistor further includes a reference electrode, which is disposed on the same layer as the ion-sensitive electrode.
[0023] Optionally, the transistor further includes a packaging layer disposed above the transistor.
[0024] Optionally, the encapsulation layer has a working electrode through-hole in the region corresponding to the ion-sensitive electrode, and the encapsulation layer has a reference electrode through-hole in the region corresponding to the reference electrode; the working electrode through-hole and the reference electrode through-hole are used to directly contact the solution in the microfluidic channel.
[0025] Optionally, the second gate contact electrode is a tin indium oxide electrode.
[0026] Optionally, the material of the second gate insulating layer is SiO2.
[0027] According to another aspect of the present invention, a biosensor chip is provided, the chip comprising:
[0028] The aforementioned ion-sensitive thin-film transistor serves as the ion-sensitive element of the chip;
[0029] A microfluidic channel is located directly above the ion-sensitive thin-film transistor, and the microfluidic channel serves as the ring-mediated isothermal amplification reaction cell of the chip.
[0030] Compared with the prior art, the present invention has at least one of the following beneficial effects:
[0031] 1. This invention constructs a bottom-gate transistor, which serves as a reference device, by comprising a first gate electrode, a first gate insulating layer, source / drain electrodes, and a semiconductor layer; and a top-gate transistor, which serves as a sensing device, by comprising source / drain electrodes, a semiconductor layer, a second gate insulating layer, a second gate electrode, and a second gate contact electrode; the bottom-gate transistor and the top-gate transistor form a low-voltage dual-gate ISFET; the top-gate transistor and the bottom-gate transistor have significantly different gate capacitance values, and using an etch stop layer (ESL) instead of ESL / PA as the top-gate dielectric can improve the top-gate / bottom-gate capacitance coupling ratio and significantly improve the sensitivity of the ion-sensitive field-effect transistor to ion response.
[0032] 2. The biochip provided by this invention includes a transistor chip and a microfluidic channel; the microfluidic channel serves as a loop-mediated isothermal amplification reaction cell; this invention solves the problem of low sensitivity in traditional ISFETs, enabling real-time, highly sensitive online monitoring of pH changes generated during loop-mediated isothermal amplification, thereby achieving rapid and highly sensitive analysis of low-concentration target nucleic acid sequences. The biochip of this invention has advantages such as low operating voltage, high sensitivity, low cost, and diverse detection targets, and is expected to become a universal sensing platform compatible with various biological detection methods. Attached Figure Description
[0033] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:
[0034] Figure 1 This is a schematic diagram of a transistor structure in the prior art;
[0035] In the figure: 101 is the substrate, 102 is the first gate electrode, 103 is the first gate insulating layer, 104 is the semiconductor layer, 105 is the second gate insulating layer, 106 is the source / drain electrode, 107 is the passivation layer, 108 is the interlayer dielectric, 109 is the second gate contact electrode, and 110 is the encapsulation layer.
[0036] Figure 2 This is a schematic diagram of the structure of an ion-sensitive thin-film transistor in one embodiment of the present invention;
[0037] In the figure: 101 is the substrate, 102 is the first gate electrode, 103 is the first gate insulating layer, 104 is the semiconductor layer, 105 is the second gate insulating layer, 106 is the source / drain electrode, 107 is the passivation layer, 108 is the interlayer dielectric layer, 109 is the second gate contact electrode, 110 is the encapsulation layer, 111 is the second gate electrode, 112 is the reference electrode, 113 is the reference electrode via, 114 is the working electrode via, 122 is the first via, and 223 is the second via.
[0038] Figure 3 This is a schematic diagram of a process for nucleic acid detection using a biosensor chip in one embodiment of the present invention. Detailed Implementation
[0039] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.
[0040] It should be noted that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in a sequence other than that illustrated or described herein.
[0041] One embodiment of the present invention provides an ion-sensitive thin-film transistor, as shown in the figure. Figure 2The transistor, from bottom to top, includes a substrate 101, a first gate electrode 102, a first gate insulating layer (first gate dielectric) 103, a semiconductor layer 104, a second gate insulating layer (second gate dielectric) 105, a second gate electrode 111, source / drain electrodes 106 disposed on both sides of the second gate electrode 111, a passivation layer 107, an interlayer dielectric layer 108, a second gate contact electrode 109, a reference electrode 112, a packaging layer 110, a reference electrode via 113, and a working electrode via 114. The transistor structure is disposed on the substrate 101, wherein: the first gate electrode 102 is disposed on the substrate 101; the first gate insulating layer 103 is disposed on the first gate contact electrode 104, the first gate dielectric layer 105, the second gate contact electrode 106, the second gate contact electrode 107, the second gate contact electrode 108, the second gate contact electrode 109, the second gate contact electrode 100, the second gate contact electrode 101, the second gate contact electrode 102, the second gate dielectric layer 103, the second gate contact electrode 104, the second gate contact electrode 105, the second gate contact electrode 106 ... The transistor is positioned above the gate electrode 102 and the substrate 101. A semiconductor layer 104 is disposed on the first gate insulating layer 103 facing the first gate electrode 102. A second gate insulating layer 105 is disposed on the semiconductor layer 104 and is shorter than the semiconductor layer 104, with a portion recessed on each side to expose the electrode contact area. Source and drain electrodes 106 are located on both sides of the semiconductor layer 104, contacting the first gate insulating layer 103, the semiconductor layer 104, and the second gate insulating layer 105, respectively. A second gate electrode 111 is disposed above the second gate insulating layer 105 and maintains a certain distance from the source and drain electrodes 106 on both sides. A passivation layer 107 is disposed above the entire transistor component and is positioned in conjunction with the substrate 101. A first via 122 is provided in the area corresponding to the second gate contact electrode 109; an interlayer dielectric layer 108 is provided above the passivation layer 107, and a second via 223 is provided in the area directly opposite the first via 122; the second gate contact electrode 109 is connected to the upper surface of the second gate electrode 111 through the second via 223, and the portion of the second gate contact electrode 109 on the interlayer dielectric layer 108 is an ion-sensitive electrode, which can be used as a working electrode; a reference electrode 112 is provided in the same layer as the ion-sensitive electrode; an encapsulation layer 110 is provided above the entire component, and a working electrode via 114 is provided at the ion-sensitive electrode, and a reference electrode via 112 is provided at the reference electrode 112. The electrode via 113; the first gate electrode 102, the first gate insulating layer 103, the source / drain electrode 106, and the semiconductor layer 104 constitute a bottom-gate transistor, serving as a switching device; the source / drain electrode 106, the semiconductor layer 104, the second gate insulating layer 105, the second gate electrode 111, and the second gate contact electrode 109 constitute a top-gate transistor, serving as an ion-sensitive element; since the second gate contact electrode 109 is ion-sensitive, it can respond sensitively to changes in solution pH; the second gate insulating layer 105 is an etch barrier layer; the top-gate transistor and the bottom-gate transistor constitute a dual-gate ion-sensitive thin-film transistor.
[0042] In this embodiment of the invention, the top-gate transistor and the bottom-gate transistor constitute a dual-gate transistor structure. The bottom-gate transistor serves as a switching device, and the top-gate transistor serves as an ion-sensitive element. Using an etch barrier layer as the top-gate dielectric, instead of the top-gate dielectric composed of an etch barrier layer / interlayer dielectric layer in the conventional technology, can improve the top-gate / bottom-gate capacitance coupling ratio and significantly improve the sensitivity of the ion-sensitive field-effect transistor to ion response.
[0043] In this embodiment of the invention, the transistor structure composed of semiconductor layer 104, second gate insulating layer 105, source / drain electrode 106, and second gate electrode 111 is a novel structure compatible with transistor mass production processes. The top-gate transistor uses the second gate insulating layer 105 as the gate insulating layer, which is thinner than the insulating layer composed of the traditional gate insulating layer and passivation layer. Due to the use of a thinner top-gate dielectric, the gate capacitance of the bottom-gate transistor is greater than that of the bottom-gate transistor, and the capacitance ratio is higher than 1, thereby realizing capacitive coupling amplification. The amplification effect formed by the capacitive coupling effect improves the sensitivity of the ion response of the ion-sensitive field-effect transistor.
[0044] In some embodiments, a working electrode via 114 is provided in the encapsulation layer 110 above the second gate contact electrode 109, and a reference electrode via 113 is provided in the encapsulation layer 110 above the reference electrode 112; the working electrode via 114 and the reference electrode via 113 are used for direct contact with the solution in the microfluidic channel. Preferably, the working electrode is an electrode that is sensitive to ion concentration.
[0045] In some embodiments, the second gate contact electrode 109 is an indium tin oxide (ITO) electrode. By using an extended ITO electrode positioned at the top as a pH-sensitive electrode, the second gate contact electrode 109 avoids electrical stability problems caused by solution leakage in conventional transistor structures using ESL / PA as the gate dielectric layer.
[0046] In some embodiments, the material of the first gate electrode 102 can be Al / Mo; the material of the first gate insulating layer 103 can be SiO2; the material of the semiconductor layer 104 can be IGZO; the material of the second gate insulating layer 105, i.e., the etch stop layer (ESL), can be SiO2; the material of the source / drain electrode 106 can be Mo / Al / Mo; the material of the second gate electrode 111 can be Mo / Al / Mo; the material of the passivation layer (PA) 107 can be SiO2 / SiN4; the material of the second gate contact electrode 109 can be ITO; and the material of the encapsulation layer 110 can be SiN4.
[0047] To fabricate the aforementioned transistor, starting from the upper surface of the substrate 101, the transistor structure can be sequentially arranged from bottom to top, namely: first gate electrode 102, first gate insulating layer 103, semiconductor layer 104, second gate insulating layer 105, source / drain electrode 106, second gate electrode 111, passivation layer 107, first via 122, interlayer dielectric layer 108, second via 223, and second gate contact electrode 109; after the main components are set, a reference electrode 112 and an encapsulation layer 110 are then arranged on top, and necessary reference electrode vias 113 and working electrode vias 114 are formed to contact the solution to be tested.
[0048] The dual-gate ion-sensitive thin-film transistor based on IGZO (In-Ga-Zn-O) provided in the above embodiments uses an etch stop layer (ESL) as the top gate dielectric layer, which can improve the top gate / bottom gate capacitance coupling ratio and provide sensitivity exceeding the Nernst limit, thereby solving the problem of low sensitivity when traditional ESL / PA is used as the gate dielectric layer.
[0049] Another embodiment of the present invention provides a biosensor chip, which includes an ion-sensitive thin-film transistor as described in the above embodiment and a microfluidic channel. The ion-sensitive thin-film transistor serves as the ion-sensitive element of the chip; the microfluidic channel is located directly above the ion-sensitive thin-film transistor and serves as the ring-mediated isothermal amplification reaction cell of the chip. Because the second gate contact electrode 109 is ion-sensitive, it can respond to pH changes in the solution within the microfluidic channel, thereby achieving biological detection.
[0050] In some embodiments, the microfluidic channel structure is disposed above the encapsulation layer 110, and the material of the microfluidic channel can be polydimethylsiloxane (PDMS). The solution flowing through the microfluidic channel is in direct contact with the working electrode through-hole 114, and the reference electrode 112 and the second gate contact electrode 109 are both located in the microfluidic channel. In the embodiments of the present invention, the top gate capacitance of the biosensor chip based on the transistor structure is greater than the bottom gate capacitance, thus exhibiting a capacitive coupling effect. This results in a sensitivity exceeding the theoretical limit defined by the Nernst formula, enabling real-time, highly sensitive monitoring of pH changes during loop-mediated isothermal amplification, thereby achieving rapid analysis of low-concentration target nucleic acid sequences.
[0051] Reference Figure 3 The procedure for nucleic acid detection using the biosensor chip in this embodiment of the invention is as follows:
[0052] By injecting the nucleic acid extract and loop-mediated isothermal amplification reaction system into the microfluidic channel of the chip, the target sequence can be amplified under constant temperature conditions. As the amplification process occurs, the pH of the solution in the microfluidic channel changes accordingly, and the electrical signal changes continuously with the reaction process. By testing the pH, it can be determined whether the corresponding nucleic acid to be tested is present in the solution. In the absence of the target sequence, the specific amplification process will not occur, so the pH of the solution hardly changes, and the electrical signal remains relatively stable.
[0053] The chip provided in the above embodiments of the present invention has advantages such as high stability, high sensitivity, low cost, and diverse detection targets. It provides a universal online monitoring platform for biological processes based on changes in ion concentration and has broad application prospects in fields such as health monitoring, disease screening, and biosafety. It is expected to become a universal sensing platform compatible with multiple biological detection methods.
[0054] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention. The above preferred features can be used in any combination without conflict.
Claims
1. An ion-sensitive thin-film transistor, characterized by, include: Substrate; A first gate electrode is disposed on the substrate; A first gate insulating layer is disposed on the first gate electrode and the substrate; A semiconductor layer is disposed on the first gate insulating layer opposite to the first gate electrode; A second gate insulating layer is disposed on the semiconductor layer and is shorter than the semiconductor layer. The second gate insulating layer is recessed on both sides to expose the electrode contact area. Source and drain electrodes are disposed on both sides of the semiconductor layer, and the source and drain electrodes are respectively in contact with the first gate insulating layer, the semiconductor layer and the second gate insulating layer; The second gate electrode is disposed above the second gate insulating layer and is kept at a distance from the source and drain electrodes on both sides; The second gate contact electrode is connected to the upper surface of the second gate electrode; The first gate electrode, the first gate insulating layer, the source and drain electrodes, and the semiconductor layer constitute a bottom-gate transistor located at the bottom, serving as a switching device; The source / drain electrodes, the semiconductor layer, the second gate insulating layer, the second gate electrode, and the second gate contact electrode constitute a top-gate transistor, serving as an ion-sensitive element. The second gate insulating layer is an etch barrier layer. The top-gate transistor and the bottom-gate transistor constitute an ion-sensitive thin-film transistor with a dual-gate structure.
2. The ion-sensitive thin-film transistor according to claim 1, characterized in that The gate capacitance of the top-gate transistor is greater than that of the bottom-gate transistor.
3. The ion-sensitive thin-film transistor according to claim 1, characterized in that, It also includes a passivation layer, which is disposed above the transistor, and the passivation layer has a first through-hole in the region corresponding to the second gate contact electrode.
4. The ion-sensitive thin-film transistor according to claim 3, characterized in that, It also includes an interlayer dielectric layer, which is disposed above the passivation layer; the portion of the second gate contact electrode on the interlayer dielectric layer is an ion-sensitive electrode; The interlayer dielectric layer has a second via in the region directly opposite the first via, and the second gate contact electrode is connected to the upper surface of the second gate electrode through the second via.
5. The ion-sensitive thin-film transistor according to claim 4, wherein It also includes a reference electrode, which is disposed on the same layer as the ion-sensitive electrode.
6. The ion-sensitive thin-film transistor according to claim 5, wherein It also includes a packaging layer disposed above the transistor.
7. The ion-sensitive thin-film transistor according to claim 6, wherein The encapsulation layer has a working electrode through-hole in the region corresponding to the ion-sensitive electrode, and a reference electrode through-hole in the region corresponding to the reference electrode; the working electrode through-hole and the reference electrode through-hole are used to directly contact the solution in the microfluidic channel.
8. The ion-sensitive thin-film transistor according to claim 1, wherein The second gate contact electrode is a tin indium oxide electrode.
9. The ion-sensitive thin-film transistor according to claim 1, wherein The material of the second gate insulating layer is SiO2.
10. A biosensor chip, characterized by, include: The ion-sensitive thin-film transistor according to any one of claims 1-9, as the ion-sensitive element of the chip; A microfluidic channel is located directly above the ion-sensitive thin-film transistor, and the microfluidic channel serves as the ring-mediated isothermal amplification reaction cell of the chip.