阅读说明：本技术 基于负电容效应的碳基场效应晶体管传感器 (Carbon-based field effect transistor sensor based on negative capacitance effect ) 是由 刘逸为 曹觉先 张志勇 赵为 于 2020-12-08 设计创作，主要内容包括：本发明提供一种基于负电容效应的碳基场效应晶体管传感器,包括：位于底层的栅极；位于栅极的一侧的底栅介质层；位于底栅介质层背离栅极一侧表面的碳纳米管沟道层；位于碳纳米管沟道层背离底栅介质层一侧表面的顶栅介质层；位于顶栅介质层背离碳纳米管沟道层一侧表面的铁电材料层、源极与漏极,铁电材料层设置在源极与漏极之间、并与源极与漏极分别电连接；以及位于铁电材料层背离顶栅介质层一侧表面的敏感层,敏感层作为传感器探针,被设置成包括用于探测待测对象的敏感材料；其中,铁电材料层被设置成通过底层的栅极施加外部电场至铁电材料的矫顽电压区间,使得铁电材料工作在负电容效应区间,提高低浓度检测的灵敏度。(The invention provides a carbon-based field effect transistor sensor based on a negative capacitance effect, which comprises: a gate electrode on the bottom layer; the bottom gate dielectric layer is positioned on one side of the gate; the carbon nano tube channel layer is positioned on the surface of one side, away from the grid, of the bottom grid dielectric layer; the top gate dielectric layer is positioned on the surface of one side, away from the bottom gate dielectric layer, of the carbon nano tube channel layer; the ferroelectric material layer is arranged between the source electrode and the drain electrode and is respectively and electrically connected with the source electrode and the drain electrode; the sensitive layer is positioned on the surface of one side, away from the top gate dielectric layer, of the ferroelectric material layer, serves as a sensor probe and is arranged to comprise a sensitive material for detecting an object to be detected; the ferroelectric material layer is set to apply an external electric field to a coercive voltage interval of the ferroelectric material through a grid electrode of the bottom layer, so that the ferroelectric material works in a negative capacitance effect interval, and the sensitivity of low-concentration detection is improved.)

1. A carbon-based field effect transistor sensor based on a negative capacitance effect, comprising:

a gate electrode on the bottom layer;

the bottom gate dielectric layer is positioned on one side of the gate;

the carbon nano tube channel layer is positioned on the surface of one side, away from the grid, of the bottom grid dielectric layer;

the top gate dielectric layer is positioned on the surface of one side, away from the bottom gate dielectric layer, of the carbon nano tube channel layer;

the ferroelectric material layer is arranged on the surface of one side, away from the carbon nanotube channel layer, of the top gate dielectric layer, and is arranged between the source electrode and the drain electrode and is respectively and electrically connected with the source electrode and the drain electrode; and

the sensitive layer is positioned on the surface of one side, away from the top gate dielectric layer, of the ferroelectric material layer, serves as a sensor probe and is arranged to comprise a sensitive material for detecting an object to be detected;

wherein the ferroelectric material layer is arranged to apply an external electric field to a coercive voltage interval of the ferroelectric material through a grid of the bottom layer, so that the ferroelectric material works in a negative capacitance effect interval.

2. The negative-capacitance-effect-based carbon-based field effect transistor sensor of claim 1, wherein the bottom gate dielectric layer and the top gate dielectric layer are both high-k thin film dielectric layers.

3. The negative-capacitance-effect-based carbon-based field effect transistor sensor of claim 2, wherein the thickness of the ferroelectric material layer is between 6nm and 12 nm.

4. The negative-capacitance-effect-based carbon-based field effect transistor sensor of claim 2, wherein the thickness of the ferroelectric material layer is 8nm to 10 nm.

5. The negative-capacitance-effect-based carbon-based field effect transistor sensor as claimed in claim 1, wherein the source and drain electrodes are symmetrically disposed on opposite sides of the ferroelectric material layer and are respectively disposed at opposite positions on one side surface of the top gate dielectric layer, and the ferroelectric material layer and the top gate dielectric layer are sandwiched between the source and drain electrodes in an overlapping manner.

6. The carbon-based field effect transistor sensor based on the negative capacitance effect as claimed in any one of claims 1 to 5, wherein the carbon-based field effect transistor sensor is applied with a gate voltage to the coercive voltage interval during use, such that the bulk factor of the carbon-based field effect transistor is less than 1 and the surface potential of the carbon nanotube channel layer is greater than the gate voltage.

7. The negative-capacitance-effect-based carbon-based field effect transistor sensor as claimed in claim 6, wherein the sensitive layer amplifies the electrical disturbance introduced by the trapped target during the detection process when the ferroelectric material layer is operating in the negative-capacitance-effect region.

8. The negative-capacitance-effect-based carbon-based field effect transistor sensor of claim 1, wherein the negative-capacitance-effect-based carbon-based field effect transistor sensor is a gas sensor.

Technical Field

The invention relates to the technical Field of transistors, in particular to a Field Effect Transistor (FET), and particularly relates to a carbon-based FET sensor based on a negative capacitance Effect.

Background

A carbon nanotube field effect transistor (CNT-FET) is a novel transistor based on a carbon-based field effect and formed by a carbon nanotube as a channel material, utilizes the characteristics of small size, high carrier mobility and high gate-channel coupling efficiency of the carbon nanotube and is very sensitive to external electrical disturbance, based on the characteristics, a sensitive material is modified on a gate as a probe to form semiconductor sensors with different functions, namely the carbon-based field effect transistor sensor, as shown in figure 1, has excellent gate regulation and control capability, physicochemical information of an object to be detected can be converted into an electrical disturbance signal through the probe, the channel material of the CNT-FET, namely the carbon nanotube is very sensitive to external electrical disturbance and is represented as channel carrier concentration change (which can be approximately P-doped or N-doped), and finally reflected as the change of working current of the sensor, so that the physicochemical index of the object to be detected is obtained, as shown in fig. 2, which is a schematic diagram of a response signal of a conventional carbon-based FET biosensor, along with the increase of the concentration of an analyte, the working current of the device in a saturation region gradually increases, and the concentration information of biomolecules can be obtained through an electrical signal.

Referring to fig. 2, it can be seen that the carbon-based FET biosensor operates in the saturation region, and the response sensitivity is much lower than that of the sub-threshold region, whereas the factors causing the current variation in the sub-threshold region of the carbon-based FET biosensor are complicated based on the conventional FET device structure, and the response signal can hardly be obtained by the current variation.

Prior art documents:

patent document 1: CN109742235A flexible ferroelectric field effect transistor and preparation method thereof

Patent document 2: CN110034181A iron-piezoelectric field effect tube and preparation method thereof

Patent document 3: CN111312829A high-sensitivity negative-capacitance field-effect tube photoelectric detector and preparation method thereof

Disclosure of Invention

The invention aims to provide a carbon-based field effect transistor sensor based on a negative capacitance effect, which is beneficial to improving the detection sensitivity of the carbon-based field effect transistor sensor by the negative capacitance effect of a ferroelectric material.

According to an improvement of the present invention, a carbon-based field effect transistor sensor based on a negative capacitance effect is proposed, comprising:

a gate electrode on the bottom layer;

the bottom gate dielectric layer is positioned on one side of the gate;

the carbon nano tube channel layer is positioned on the surface of one side, away from the grid, of the bottom grid dielectric layer;

the top gate dielectric layer is positioned on the surface of one side, away from the bottom gate dielectric layer, of the carbon nano tube channel layer;

the ferroelectric material layer is arranged on the surface of one side, away from the carbon nanotube channel layer, of the top gate dielectric layer, and is arranged between the source electrode and the drain electrode and is respectively and electrically connected with the source electrode and the drain electrode; and

the sensitive layer is positioned on the surface of one side, away from the top gate dielectric layer, of the ferroelectric material layer, serves as a sensor probe and is arranged to comprise a sensitive material for detecting an object to be detected;

wherein the ferroelectric material layer is arranged to apply an external electric field to a coercive voltage interval of the ferroelectric material through a grid of the bottom layer, so that the ferroelectric material works in a negative capacitance effect interval.

Preferably, the bottom gate dielectric layer and the top gate dielectric layer both adopt high-k thin film dielectric layers.

Wherein the thickness of the ferroelectric material layer is 6nm-12 nm. Preferably, the thickness of the ferroelectric material layer is 8nm to 10 nm.

The source electrode and the drain electrode are symmetrically distributed on two sides of the ferroelectric material layer and are respectively positioned at opposite positions on one side surface of the top gate dielectric layer, and the ferroelectric material layer and the top gate dielectric layer are overlapped and clamped between the source electrode and the drain electrode.

In the using process of the carbon-based field effect transistor sensor, the gate voltage is applied to the coercive voltage interval, so that the body factor of the carbon-based field effect transistor is smaller than 1, and the surface potential of the carbon nanotube channel layer is larger than the gate voltage.

Preferably, the sensitive layer amplifies the electric disturbance introduced by the capture target object when the ferroelectric material layer works in a negative capacitance effect interval in the detection process.

Therefore, according to the carbon-based field effect transistor sensor, the ferroelectric material layer is deposited on the carbon nano tube channel layer, the voltage applied to the ferroelectric material is adjusted to the coercive voltage interval through the bottom gate electrode, the ferroelectric material has the negative capacitance effect along with the continuous increase of the gate voltage, at the moment, the electric disturbance introduced by the top gate probe for capturing the target object is amplified, the sensor can respond under the condition of smaller concentration of the detected object, and the detection sensitivity is correspondingly improved.

It should be understood that all combinations of the foregoing concepts and additional concepts described in greater detail below can be considered as part of the inventive subject matter of this disclosure unless such concepts are mutually inconsistent. In addition, all combinations of claimed subject matter are considered a part of the presently disclosed subject matter.

The foregoing and other aspects, embodiments and features of the present teachings can be more fully understood from the following description taken in conjunction with the accompanying drawings. Additional aspects of the present invention, such as features and/or advantages of exemplary embodiments, will be apparent from the description which follows, or may be learned by practice of specific embodiments in accordance with the teachings of the present invention.

Drawings

The drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures may be represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. Embodiments of various aspects of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

fig. 1 is a schematic diagram of a carbon nanotube field effect transistor in the prior art.

FIG. 2 is a schematic diagram of the response signal of a carbon nanotube FET sensor.

FIG. 3 is a schematic diagram of a carbon-based field effect transistor sensor based on a negative capacitance effect in accordance with an exemplary embodiment of the present invention.

Fig. 4(a) -4(b) are schematic views of PE-Loop curves of a ferroelectric material layer in a carbon-based field effect transistor sensor based on a negative capacitance effect according to an exemplary embodiment of the present invention, where (a) represents PE-Loop (i.e., hysteresis curve), and (b) represents PE-Loop and IV (current voltage).

Fig. 5 is a schematic diagram illustrating the energy landscapes of the negative capacitance effect of the ferroelectric material according to an exemplary embodiment of the present invention.

Fig. 6 is a schematic diagram of the voltage and charge of a ferroelectric material as a function of time in accordance with an exemplary embodiment of the present invention.

Detailed Description

In order to better understand the technical content of the present invention, specific embodiments are described below with reference to the accompanying drawings.

In this disclosure, aspects of the present invention are described with reference to the accompanying drawings, in which a number of illustrative embodiments are shown. Embodiments of the present disclosure are not necessarily intended to include all aspects of the invention. It should be appreciated that the various concepts and embodiments described above, as well as those described in greater detail below, may be implemented in any of numerous ways, as the disclosed concepts and embodiments are not limited to any one implementation. In addition, some aspects of the present disclosure may be used alone, or in any suitable combination with other aspects of the present disclosure.

According to the improvement of the invention, a carbon-based field effect transistor (CNT-FET) sensor based on a negative capacitance effect is provided, a sensitive layer probe is utilized to detect a target object to form an electrical disturbance signal, and the characteristic that a channel material of the CNT-FET, namely a carbon nano tube, is very sensitive to external electrical disturbance is utilized to express the change of the concentration of a channel carrier, and finally the change of the working current of the sensor is reflected, so that the physicochemical index of an object to be detected is obtained. On the basis, through intensive research, a carbon-based field effect transistor sensor based on a ferroelectric material negative capacitance effect is provided, a ferroelectric material layer is added on a carbon nano tube channel layer (CNT), an external electric field is applied to a coercive voltage interval, so that the ferroelectric material works in the negative capacitance effect interval, a grid voltage amplification function is realized by utilizing the negative capacitance effect, the electric disturbance at a probe is amplified, and the effect of improving the response sensitivity of the sensor is achieved.

To this end, the invention proposes a carbon-based field effect transistor sensor based on the negative capacitance effect, comprising:

a gate G on the bottom layer;

the bottom gate dielectric layer is positioned on one side of the gate electrode and is High-K-1;

the carbon nano tube channel layer CNT is positioned on the surface of one side, away from the grid, of the bottom grid dielectric layer;

the top gate dielectric layer High-K-2 is positioned on the surface of one side, away from the bottom gate dielectric layer, of the carbon nano tube channel layer;

the ferroelectric material Layer is arranged between the source electrode and the drain electrode and is respectively and electrically connected with the source electrode and the drain electrode; and

the sensitive layer PROBE is positioned on the surface of the ferroelectric material layer, which is far away from the side of the top gate dielectric layer, is used as a sensor PROBE and is arranged to comprise a sensitive material for detecting an object to be detected;

wherein the ferroelectric material layer is arranged to apply an external electric field to a coercive voltage interval of the ferroelectric material through the grid of the bottom layer, so that the ferroelectric material works in a negative capacitance effect interval.

Therefore, the sensitive material is contacted with the detected object, the attribute information of the object to be detected is converted into an electrical disturbance signal, and the carbon nano tube channel layer serving as the channel responds to the electrical disturbance sensitively, so that the concentration of the channel carrier changes, the change of the working current of the sensor is reflected, the attribute of the object to be detected is obtained, and the detection process is realized. In the process, if the object to be detected is a gas, the sensor of the invention is a gas sensor, and under the condition of relatively low gas concentration, the change of the working current is relatively small or basically does not show change, so that the detection fails or is inaccurate. Therefore, how to solve the detection under the condition of low concentration is the key to be solved by the invention to realize a sensor with high sensitivity.

Therefore, on the basis of the negative capacitance effect, the invention provides the carbon-based field effect transistor sensor based on the negative capacitance effect, the ferroelectric material layer is arranged on the carbon nano tube channel layer (the top gate dielectric layer is arranged in the middle to be beneficial to deposition), the voltage applied to the ferroelectric material is adjusted to be close to the coercive voltage through the bottom gate electrode, the negative capacitance effect occurs to the ferroelectric material along with the continuous increase of the gate voltage, at the moment, the electric disturbance introduced by the top gate probe for capturing the target object is amplified, the sensor can respond under the condition of smaller concentration of the detected object, and the detection sensitivity is correspondingly improved.

Referring to fig. 4(a), a plurality of domain units (domains) are present in the ferroelectric material, and each domain unit has a spontaneous polarization direction, which is shown by an increase in polarization strength along a direction parallel to an electric field and a decrease in polarization strength along a direction parallel to an electric field when being influenced by an applied electric field. A PE-loop curve is formed between the polarization P and an externally applied electric field E, and the polarization P is later than the electric field intensity. In a typical hysteresis curve (PE-Loop curve), as the applied electric field increases, the polarization strength P rises along the OAB curve with the increase of E, and after the point B, P shows a linear characteristic (BC section) with the change of E, and after the point B falls, P does not fall along the original curve but falls along the CBD. When E is zero, the polarization is not equal to zero, but equal to Pr, i.e. the remanent polarization. When the applied electric field continues to weaken the polarization of the ferroelectric and continuously decreases, i.e. the DF section, when the polarization of the ferroelectric is 0, the voltage at this time is called coercive voltage (corresponding to point F). At the coercive voltage, the polarization direction of the ferroelectric is reversed, as shown in fig. 5.

At the moment of inversion the capacitance of the ferroelectric material appears negative and a large amount of charge accumulates on its surface, as shown by the dashed line in fig. 4(b), and the current reaches a maximum, if viewed from the voltage V and charge Q versus time curve, as shown in fig. 6, we find that as the voltage decreases, the amount of charge increases, which is called negative capacitance effect.

In the transistor, based on a positive feedback mechanism, the expression of the dielectric layer capacitance is as follows:

the body factor (the ratio of gate voltage to channel potential) of a transistor is:

when the negative capacitance effect occurs, the bulk factor is smaller than 1, and the surface potential of the CNT channel material is larger than the grid voltage, so that the surface can realize the function of a grid voltage amplifier through the negative capacitance effect. When the ferroelectric material works in a negative capacitance effect interval, the electric disturbance introduced by the target object captured by the sensitive layer is amplified, so that the sensor can respond under the condition of smaller concentration of the detected object, and the detection sensitivity is improved.

Preferably, the bottom gate dielectric layer and the top gate dielectric layer are both used as gate dielectric layers, and high-k dielectric layers (i.e. dielectric layers formed of high-k dielectric materials) are used to maintain the driving current and reduce the leakage current density. Optionally, the high-k dielectric layer is made of metal oxide (such as La)₂O₃、HfO₂、Al₂O₃、Y₂O₃Etc.) or nitride. Preferably, the bottom gate dielectric layer and the top gate dielectric layer are both thin film dielectric layers, and the thickness of the thin film dielectric layers is less than 10 nm.

The bottom gate dielectric layer is used for isolating the gate from the channel (namely the carbon nanotube channel layer), and the top gate dielectric layer is used for isolating the carbon nanotube channel layer from the ferroelectric material layer, and is favorable for preparing the ferroelectric material layer after the carbon nanotube channel layer is acted by the dielectric layer, so that the FE layer is prevented from being directly prepared on the carbon nanotube channel layer.

Optionally, the ferroelectric material layer has a thickness of 6nm to 12 nm. It is particularly preferred that the thickness of the layer of ferroelectric material is between 8nm and 10 nm. Wherein the ferroelectric material layer is arranged to operate in a crystal polarization saturation region.

Wherein, the ferroelectric material layer adopts Y: HfO₂(i.e., Y-doped HfO)₂)、Si：HfO₂Or Zr: HfO₂A material. In an alternative embodiment, Y: HfO₂And the material layer is prepared in a magnetron sputtering mode.

As shown in fig. 3, the source and the drain are symmetrically distributed on two sides of the ferroelectric material layer and are respectively located at opposite positions on one side surface of the top gate dielectric layer to form a symmetrical structure.

It should be understood that in the present invention, the source, the drain and the gate, which are described correspondingly, all refer to electrodes that can conduct electricity. The source electrode and the drain electrode can be made of metal with high power function or metal with low power factor correspondingly, so that the P-type or N-type field effect transistor sensor is prepared.

Preferably, the carbon nanotube channel layer includes a grid-shaped carbon nanotube film, which may be prepared in an existing manner or purchased through a market, and in particular, carbon nanotubes with a purity of 99.99% are obtained to improve carrier mobility.

As an alternative example, the carbon-based field effect transistor sensor proposed by the present invention may be fabricated by a semiconductor device fabrication process in an actual fabrication process, for example, based on ALD, PLD or MBE, and in another embodiment, a part of the layered structure may be fabricated by evaporation.

Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, the protection scope of the present invention should be determined by the appended claims.