Patent Application
20100072976
The present invention relates to a sensing element, and more particularly to a sensing element that includes a transistor with a surface-modified ultra-thin channel and a microchannel. The present invention also relates to a method of manufacturing the sensing element and a biological detection system employing the sensing element.
A field-effect transistor (FET) is a semiconductor device that utilizes electric field effect to control the current. Due to its advantages of small size, light weight, low power consumption, long lifetime, high input impedance, low noise, good thermal stability, enhanced anti-radiation ability, and simple manufacturing procedures, the FET has a variety of applications, and has particularly been widely used in large-scale integrated circuit (LSI) and very-large-scale integrated circuit (VLSI).
Moreover, since a nano-scale FET has extremely high electric sensitivity, it has also been used as a basic framework of biological sensors to be applied in the biological detection field. However, such FET comprises a channel made of carbon nanotubes, and it is therefore difficult to align nanotubes to makes the device, separate metal from the co-existing carbon tubes that have semiconductor properties, modify the surfaces of the nano carbon tubes, and scale to large area manufacture. As to silicon-nanowire FETs, while manufacturing with a top-down process, expensive manufacturing equipments are required and thus leads to undesirable increase of the manufacturing cost. On the other hand, while the silicon-nanowire FET is manufactured with a bottom-up process, different problems, such as difficult to fabricate the silicon nanowires as devices, control of the radius uniformity of silicon nanowires, and low yield in large-area process, etc., will be encountered.
A sensing element, a manufacturing method thereof, and a biological detection system employing such sensing element for use in the detection of biological or chemical species are therefore proposed in this invention. The thickness of an FET forming the sensing element may be reduced to nano scale through a conventional semiconductor manufacturing process, so that the sensing element may possess superior electrical sensitivity in application to the detection of biological and chemical species.
A primary object of the present invention is to provide a sensing element, a manufacturing method thereof, and a biological detection system employing such sensing element, so as to solve the problems of difficult manufacturing process and high manufacturing cost as found in conventional sensing elements.
Another object of the present invention is to provide a sensing element, a manufacturing method thereof, and a biological detection system employing such sensing element, so as to increase the sensitivity of the sensing element.
To achieve the above and other objects, the sensing element according to the present invention includes a field-effect transistor (FET), a reference electrode, a first passivation layer, a second passivation layer, and a microchannel. The FET has an ultra-thin channel, the first passivation layer encloses a first portion of the FET, the second passivation layer encloses a second portion of the FET, and the microchannel is bonded to the first and the second passivation layer to extend across the channel of the ultra-thin channel FET. The ultra-thin channel has a modified surface. The FET correspondingly generates an electric signal when an analyte to be tested passes through the microchannel to get inteact chemically or physically with the modified surface of the ultra-thin channel.
Preferably, the analyte to be tested is a biological material, such as the ribonucleic acid (RNA), deoxyribonucleic acid (DNA), enzymes, proteins, viruses or lipids, or a chemical substance.
The method of manufacturing the aforementioned sensing element according to the present invention includes the following steps:
(a) providing an FET having an ultra-thin channel, and the ultra-thin channel having a thickness smaller than 50 nm;
(b) defining a reference electrode, a source electrode, and a drain electrode;
(c) depositing a passivation layer;
(d) heat bonding a microchannel to the passivation layer; and
(e) modifying a surface of the ultra-thin channel to complete the sensing element.
The surface of the ultra-thin channel may be chemically or physically modified. In the case of chemical surface modification, chemicals used for this purpose may be silane coupling agents with amino group, carboxyl group, aldehyde group, or thiol group; or metallic complexes with nickel, iron, gold, silver, or platinum. Alternatively, in the case of physical surface modification, it may be achieved through non-covalent bonding.
To achieve the above and other objects, the biological detection system for detecting a biological material according to the present invention includes a sensing element of the present invention and a signal output device. The sensing element may detect an electric signal, and the signal output device outputs and records the electric signal. High-sensitive detection may be implemented on the biological material by observing changes in the electric signal.
Preferably, the signal output device is a semiconductor parameter analyzer.
Preferably, the electric signal is a current signal, a voltage signal, or a conductance signal.
With the above arrangements, the sensing element, the manufacturing method thereof, and the biological detection system employing the sensing element according to the present invention provide at least one or more of the following advantages:
The structure and the technical means adopted by the present invention to achieve the above and other objects may be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings, wherein
Please refer to
The FET 10 includes a substrate 11, an insulating layer 12, an active layer 13, a source 14, and a drain 15. The insulating layer 12 is deposited atop the substrate 11. The substrate 11 is preferably made of a monocrystalline silicon material or a glass material, and the insulating layer 12 is preferably made of a silicon compound, such as silica (SiO2) or silicon nitride (Si3N4).
The active layer 13 includes an ultra-thin channel, and is deposited atop the insulating layer 12. The source 14 is an electrically conductive body and is in electric contact with the active layer 13. The drain 15 is another electrically conductive body and is also in electric contact with the active layer 13. The drain electrode 141 and the drain electrode 151 are deposited atop the source 14 and the drain 15, respectively. The active layer 13 is preferably made of a monocrystalline silicon material, a polycrystalline silicon material, or an amorphous silicon material, and preferably has a thickness smaller than 50 nm.
The ultra-thin channel of the FET 10 is chemically or physically surface-modified. In the case of chemical surface modification, chemicals used for this purpose may be silane coupling agents with amino group, carboxyl group, aldehyde group, or thiol group; or metallic complexes with nickel, iron, gold, silver, or platinum. Alternatively, in the case of physical surface modification, it may be achieved through non-covalent bonding.
The first passivation layer 17 is used to enclose the source electrode 141 of the FET 10, and the second passivation layer 18 is used to enclose the drain electrode 151 of the FET 10. The microchannel 19 is bonded to the first passivation layer 17 and the second passivation layer 18. The reference electrode 16 is provided on the FET 10. The first and the second passivation layer 17, 18 are preferably made of an insulating material, such as silica (SiO2), silicon nitride (Si3N4), or aluminum oxide (Al2O3). The reference electrode 16 is preferably a gold, a platinum, or a silver chloride/chloride (AgCl/Cl) reference electrode. And, the microchannel 19 is preferably made of silicon, SiO2, or other organic materials, such as polydimethylsiloxane (PDMS), polymeric material SU-8, polymethylmethacrylate (PMMA), or cyclic olefin copolymers (COC).
When an analyte is to be tested, which may be a biological material, such as the ribonucleic acid (RNA), deoxyribonucleic acid (DNA), enzymes, proteins, viruses or lipids, or a chemical substance, the analyte firstly passes through the microchannel 19 to be contact with the modified surface of the ultra-thin channel by bonding or adsorbing, the FET 10 would correspondingly generate an electric signal, such as a current signal, a voltage signal, or a conductance signal. Since the sensing element of the present invention has a Debye length larger than a thickness of the ultra-thin channel, the sensing element may have a sensitivity superior to other sensors of prior art. And, a user may select a proper substance for use in the surface modification according to the properties of the analyte to be tested.
Please refer to
Please further refer to
From the above description, it is understood that the thickness of the channel for the sensing element of the present invention may be reduced through repeated oxidation and wet etching, and the channel thickness may be highly accurately controlled through chemical vapor deposition to thereby achieve the purpose of reducing the manufacturing cost of the sensing element.
Please refer to
Step S1, in which an FET with an ultra-thin channel is provided. To do so, boron ions are implanted into an active layer 31 of an ultra-thin channel chip; then the chip is activated in a furnace at approximately 950° C. for about 30 minutes. Thereafter, lithography technique is employed to define a source 32 and a drain 33 on the chip; and heavy doping is performed by ion implantation. The chip is then activated in a rapid thermal annealing furnace at approximately 1050° C. for about 30 seconds. Finally, a sub-micro channel pattern is defined on the chip by etching to thereby obtain an ultra-thin channel FET, as shown by the illustrations (A) and (B) of
Step S2, in which a source electrode 321 and a drain electrode 331 are defined using lithography technique, as shown by the illustration (C) of
Step S3, in which a passivation layer 35 is deposited to protect the source electrode 321 and the drain electrode 331, as shown by the illustration (D) of
Step S4, in which a microchannel chip 36 is connected to the passivation layer 35 by heat bonding. To do so, first use ultraviolet-ozone plasma treatment to clean the microchannel chip 36 and the passivation layer 35, and then bond the microchannel chip 36 to the passivation layer 35. The structure is then heated on a hotplate at 80˜100° C. for about 4 hours; and,
Step S5, in which the surface of the ultra-thin channel is chemically or physically modified to complete the preparation of the sensing element, as the illustration (E) of
Preferably, the signal output device 52 is a semiconductor parameter analyzer or other measuring device adapted to detect electric signals. And, the electric signal 53 is preferably a current signal, a voltage signal, or a conductance signal.
Please refer to
Those skilled in the art would readily appreciate that all parameters listed herein are meant to be exemplary and that actual parameters will depend upon the specific application for which the methods, elements and systems of the present invention are used. It is, therefore, to be understood that the embodiments herein are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described.
| Number | Date | Country | Kind |
|---|---|---|---|
| 097136557 | Sep 2008 | TW | national |
