Semiconductor ammonia sensor and method of manufacturing the same

Abstract

The application relates to the technical field of semiconductor sensor, and provides a semiconductor ammonia sensor and a preparation method thereof. The semiconductor ammonia sensor comprises a doped silicon substrate, a silicon dioxide gate dielectric layer, a two-dimensional semiconductor channel layer, a source electrode and a drain electrode; the gate dielectric layer is located on the doped silicon substrate; the two-dimensional semiconductor channel layer, the source electrode and the drain electrode are all located on the gate dielectric layer; the source electrode and the drain electrode are located on the two sides of the two-dimensional semiconductor channel layer and are opposite to each other; the doped silicon substrate is used as a back gate electrode; when the doped silicon substrate is loaded with a bias voltage, the working point of the two-dimensional semiconductor channel layer is controlled in a subthreshold swing range; and a molybdenum oxide interface enhancement layer is located on the two-dimensional semiconductor channel layer. According to the technical scheme, the interface charge change caused by ammonia adsorption can be efficiently amplified into a significant drain current response through the synergistic regulation of the molybdenum oxide interface enhancement layer and the back gate voltage, so that the sensitivity of the sensor is improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor sensor technology, specifically to a semiconductor ammonia sensor and its preparation method. Background Technology

[0002] In related technologies, existing two-dimensional semiconductor gas sensors typically rely solely on back gate voltage for electrostatic regulation, lacking an effective local enhancement mechanism for channel surface charge. When ammonia molecules adsorb onto the surface of a two-dimensional channel, the resulting change in interface charge density is weak, making it difficult to form an effective synergistic regulation between the equivalent top gate potential and the back gate voltage. This leads to low channel carrier concentration modulation efficiency and an inability to fully utilize the high transconductance characteristics of two-dimensional semiconductors in the subthreshold swing range to amplify minute interface charge changes into significant drain current responses, thereby limiting the sensor's detection sensitivity. Summary of the Invention

[0003] The technical problem solved by this application is to provide a semiconductor ammonia sensor and its preparation method. By synergistically controlling the molybdenum oxide interface enhancement layer and the back gate voltage, the interface charge change caused by ammonia adsorption can be efficiently amplified into a significant drain current response, thereby improving the sensor's sensitivity, signal-to-noise ratio and detection performance.

[0004] According to a first aspect of the present application, a semiconductor ammonia sensor is provided. The semiconductor ammonia sensor includes a doped silicon substrate, a silicon dioxide gate dielectric layer, a two-dimensional semiconductor channel layer, a molybdenum oxide interface enhancement layer, a source electrode, and a drain electrode. The gate dielectric layer is located on the doped silicon substrate. The two-dimensional semiconductor channel layer, the source electrode, and the drain electrode are all located on the gate dielectric layer. The source electrode and the drain electrode are located on opposite sides of the two-dimensional semiconductor channel layer and are positioned opposite each other. The doped silicon substrate is used as a back gate electrode. When a bias voltage is applied to the doped silicon substrate, it is used to control the operating point of the two-dimensional semiconductor channel layer within the subthreshold swing range. The molybdenum oxide interface enhancement layer is located on the two-dimensional semiconductor channel layer. The molybdenum oxide interface enhancement layer is used to undergo chemical adsorption upon contact with ammonia gas and generate an equivalent top gate potential change. The equivalent top gate potential change is converted into a drain current change using the field-effect amplification mechanism of the back gate electrode.

[0005] Compared with the prior art, the beneficial effects of this application are as follows: by introducing a molybdenum oxide interface enhancement layer on the surface of the two-dimensional semiconductor channel layer, ammonia molecules are captured and interfacial charge transfer occurs, causing a change in surface charge density, thereby inducing an equivalent top gate potential in the channel; the equivalent top gate potential and the back gate voltage can jointly regulate the carrier concentration in the channel, and by utilizing the high transconductance characteristics of the two-dimensional semiconductor in the subthreshold swing range, the small interfacial charge change is amplified into a significant drain current response, thereby improving the detection sensitivity of the sensor.

[0006] In one embodiment, the thickness of the molybdenum oxide interface reinforcement layer ranges from 0.7 nm to 3.5 nm.

[0007] The beneficial effects are as follows: when the thickness is less than 0.7 nm, it is difficult for the film to form a continuous coverage, resulting in insufficient active sites and easy pinhole defects, which reduces the adsorption capacity; when the thickness exceeds 3.5 nm, due to the attenuation of the tunneling effect and the increase of resistance under Ohm's law, the electrostatic coupling efficiency of surface charge to channel carriers decreases, and the excessively thick dielectric layer weakens the potential modulation capability of the "equivalent top gate". Therefore, within this specific thickness range, sufficient ammonia adsorption surface area can be ensured to generate significant interfacial charge transfer, while ensuring efficient penetration of the electric field into the two-dimensional semiconductor channel, thereby maximizing the sensing responsivity at room temperature.

[0008] In one embodiment, the molybdenum oxide interface reinforcement layer is made of MoO. x , of which 0 <x≤3。

[0009] Its beneficial effects are that MoO x The oxygen vacancies in the material serve as active adsorption sites, enabling efficient capture of ammonia molecules and rapid charge transfer reactions, thus enhancing the sensor's sensitivity. Furthermore, by adjusting the x-value, the work function and surface dipole moment of the material can be precisely controlled, thereby optimizing the modulation efficiency of the equivalent top gate potential.

[0010] In one embodiment, the molybdenum oxide interface enhancement layer is disposed on the two-dimensional semiconductor channel layer in a fully covered or partially patterned manner.

[0011] The beneficial effects are that, when using a full-coverage approach, the active adsorption area can be maximized, improving the overall ammonia capture efficiency and response amplitude; while when using a localized patterning approach, parasitic capacitance and background noise in non-sensitive areas can be effectively reduced, lowering device power consumption and improving high-frequency response characteristics. This diversified integration strategy allows the sensor to achieve the optimal balance between sensitivity, response speed, and power consumption according to the specific application requirements.

[0012] In one embodiment, the two-dimensional semiconductor channel layer is a molybdenum disulfide layer.

[0013] Its beneficial effects lie in the fact that, compared to traditional silicon-based semiconductor materials, molybdenum disulfide has a larger band gap, enabling it to achieve a lower off-state current and thus providing extremely high transconductance gain. This allows the weak equivalent top-gate voltage generated by charge transfer at the molybdenum oxide interface to be efficiently amplified into a significant drain current change. Furthermore, its surface lacks dangling bonds and has a flat lattice, which facilitates the uniform growth and stable adhesion of the molybdenum oxide reinforcement layer, further improving the device's signal-to-noise ratio and long-term stability.

[0014] In one embodiment, the molybdenum disulfide layer is a single-layer structure.

[0015] The advantages lie in the fact that using a single layer of molybdenum disulfide allows for extremely thin atomic layers, thereby maximizing the electrostatic modulation efficiency of the molybdenum oxide interface reinforcement layer on the channel potential. Due to the extremely weak bulk effect of the single-layer material, charge transfer caused by surface-adsorbed gas molecules can modulate the carrier concentration throughout the channel with almost no attenuation, improving the device's sensitivity and response speed. Furthermore, the single-layer structure eliminates grain boundary scattering and vertical electric field shielding effects caused by multilayer stacking, further improving carrier mobility and ensuring the sensor possesses a higher signal-to-noise ratio and faster dynamic response characteristics.

[0016] In one embodiment, the subthreshold swing ranges from 70 mV / dec to 120 mV / dec.

[0017] Its beneficial effect lies in the fact that this subthreshold swing range is significantly better than the thermodynamic limit of 60mV / dec for traditional silicon-based metal-oxide-semiconductor field-effect transistors (MOSFETs), indicating that the device possesses extremely strong electrostatic control capability of the gate over channel carriers. The smaller subthreshold swing means that only a very small change in gate voltage can cause an exponential change in drain current, thereby significantly reducing the device's operating voltage and static power consumption.

[0018] In one embodiment, the doping element of the doped silicon substrate is boron, and the doping concentration ranges from 1 × 10⁻⁶. 19 atoms / cm 3 Up to 3×10 20 atoms / cm 3 .

[0019] The beneficial effects are that using high-concentration boron as a P-type dopant can reduce substrate resistivity, thereby effectively reducing the contact resistance between the source / drain and the channel, and improving the overall conduction performance and response speed of the device. Simultaneously, a high doping level helps form stable ohmic contacts, reducing scattering interference from interface states on carrier transport; while controlling the concentration within a specific range ensures good conductivity while avoiding the increase in lattice defects or Fermi level pinning effects caused by excessive doping, ensuring the formation of an ideal Schottky barrier or low-resistance contact between the two-dimensional semiconductor channel layer and the substrate, thus optimizing the electrical stability and consistency of the device.

[0020] According to a second aspect of the present application, a method for fabricating a semiconductor ammonia sensor is provided, comprising: providing a doped silicon substrate; forming a gate dielectric layer on the doped silicon substrate; forming a two-dimensional semiconductor channel layer, a source, and a drain on the gate dielectric layer; wherein the source and the drain are located on opposite sides of the two-dimensional semiconductor channel layer and are positioned opposite each other; and forming a molybdenum oxide interface enhancement layer on the two-dimensional semiconductor channel layer.

[0021] In one embodiment, forming a molybdenum oxide interface enhancement layer on the two-dimensional semiconductor channel layer includes: depositing a molybdenum layer on the two-dimensional semiconductor channel layer; and oxidizing the deposited molybdenum layer to form the molybdenum oxide interface enhancement layer.

[0022] The beneficial effect lies in the fact that this "deposition followed by oxidation" process strategy can effectively avoid the high-temperature damage or precursor residue problems that may be caused by direct chemical vapor deposition or atomic layer deposition, thereby protecting the integrity of the fragile two-dimensional semiconductor channel layer structure. By controlling the initial deposition thickness of the molybdenum layer and subsequent oxidation conditions, the atomic-level thickness and stoichiometry of the molybdenum oxide interface can be precisely controlled to ensure the formation of a uniform, dense, and pinhole-free interface layer. This not only maximizes the charge transfer efficiency at the interface to enhance the sensitive response to ammonia molecules, but also effectively passivates the surface dangling bonds of the two-dimensional material, reduces carrier scattering caused by defect states, and thus improves the sensor's sensitivity, response speed, and long-term operational stability. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a semiconductor ammonia sensor according to an exemplary embodiment.

[0024] Figure 2 This is a flowchart illustrating a method for fabricating a semiconductor ammonia sensor according to an exemplary embodiment.

[0025] Figure 3 This is a schematic diagram illustrating a structure in which a gate dielectric layer is formed on a doped silicon substrate, according to an exemplary embodiment.

[0026] Figure 4 This is a schematic diagram illustrating a structure in which a two-dimensional semiconductor channel layer is formed on a gate dielectric layer according to an exemplary embodiment.

[0027] Figure 5 This is a schematic diagram illustrating a structure in which a source and a drain are formed on a gate dielectric layer according to an exemplary embodiment.

[0028] Figure 6 This is a schematic diagram illustrating a structure for depositing a molybdenum layer on a two-dimensional semiconductor channel layer according to an exemplary embodiment.

[0029] Explanation of the reference numerals in the figure: 1. Doped silicon substrate; 2. Gate dielectric layer; 31. Source; 32. Drain; 4. Two-dimensional semiconductor channel layer; 5. Molybdenum layer; 6. Molybdenum oxide interface enhancement layer. Detailed Implementation

[0030] Unless otherwise defined, the technical or scientific terms used in this specification and claims shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. Specific embodiments of this application will be described below in conjunction with the accompanying drawings. It should be noted that, in order to provide a concise description, this specification cannot exhaustively describe all features of the actual embodiments. Without departing from the spirit and scope of this application, those skilled in the art can modify and substitute the embodiments of this application, and the resulting embodiments are also within the protection scope of this application.

[0031] In related technologies, gas sensors are essential components in environmental monitoring, industrial safety, food cold chain, and healthcare. Ammonia (NH3) is a key monitoring target due to its widespread presence in chemical leaks, livestock farming, refrigeration systems, and breath analysis. Traditional semiconductor gas-sensitive materials, such as metal oxides, typically require high operating temperatures to achieve sufficient response. However, in low-power, room-temperature, integrable, and arrayable applications, two-dimensional semiconductor field-effect transistor (FET) gas-sensing platforms exhibit unique advantages: two-dimensional materials possess extremely high specific surface area and surface charge sensitivity, and the charge transfer, interfacial dipole changes, and barrier modulation caused by gas molecule adsorption can be directly amplified and read out by the transistor current. In particular, transition metal sulfides such as MoS2 combine manufacturability and stability, promising the development of low-power, high-sensitivity, on-chip integrated gas sensing solutions.

[0032] Although two-dimensional semiconductor field-effect transistor gas sensors and MoS2 / MoO3 composite material systems have been extensively studied, existing technologies still have significant limitations when it comes to back-gate structures, NH3 monitoring in high-humidity environments at room temperature, and on-chip integration applications: poor selectivity and baseline drift: exposed MoS2 is sensitive to a variety of gases and water vapor, and is easily affected by ambient humidity, leading to baseline drift and a lack of selective recognition capability for NH3; insufficient sensitivity: the gas-sensing response amplitude of a simple MoS2 FET to NH3 is small, making it difficult to meet the high sensitivity requirements of practical industrial detection; low integration and no amplification advantage: existing MoS2 / MoO3 composite systems mostly adopt resistive thin-film structures, which cannot utilize the gate current amplification advantage of MOSFETs, and are difficult to achieve tight coupling integration with standard micro-nano processes and array readout circuits; limited dynamic performance: some devices suffer from slow recovery and severe hysteresis due to adsorption retention effects, which restricts the performance of long-term stable monitoring.

[0033] To address the aforementioned technical problems, this application proposes a semiconductor ammonia sensor, device, electronic device, and storage medium. By synergistically regulating the molybdenum oxide interface enhancement layer and the back gate voltage, the interface charge change caused by ammonia adsorption can be efficiently amplified into a significant drain current response, thereby significantly improving the sensor's sensitivity, signal-to-noise ratio, and detection performance.

[0034] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0035] like Figure 1 As shown, a first embodiment of the present invention provides a semiconductor ammonia sensor, which includes a doped silicon substrate, a gate dielectric layer 1, a two-dimensional semiconductor channel layer 4, a source electrode 31, and a drain electrode 32. The gate dielectric layer 2 is located on the doped silicon substrate 1. The two-dimensional semiconductor channel layer 4, the source electrode 31, and the drain electrode 32 are all located on the gate dielectric layer 2. The source electrode 31 and the drain electrode 32 are located on opposite sides of the two-dimensional semiconductor channel layer 4. The doped silicon substrate 1 serves as a back gate electrode, and when a bias voltage is applied to the doped silicon substrate 1, it is used to control the operating point of the two-dimensional semiconductor channel layer 4 within the subthreshold swing range. A molybdenum oxide interface enhancement layer is located on the two-dimensional semiconductor channel layer 4. The molybdenum oxide interface enhancement layer 6 is used to undergo chemical adsorption upon contact with ammonia gas and generate an equivalent top gate potential change, which is converted into a change in drain current using the field-effect amplification mechanism of the back gate electrode.

[0036] In one embodiment, the thickness of the molybdenum oxide interface reinforcement layer 6 ranges from 0.7 nm to 3.5 nm.

[0037] In some specific embodiments, the thickness of the molybdenum oxide interface enhancement layer 6 is 0.7 nm.

[0038] In other specific embodiments, the thickness of the molybdenum oxide interface enhancement layer 6 is 2.1 nm.

[0039] In some specific embodiments, the thickness of the molybdenum oxide interface enhancement layer 6 is 3.5 nm.

[0040] In one embodiment, the molybdenum oxide interface reinforcement layer 6 is made of MoO. x , of which 0 <x≤3。

[0041] In some specific embodiments, x is 3.

[0042] In other specific embodiments, x is 2.

[0043] In some specific embodiments, x is 1.

[0044] In one embodiment, the molybdenum oxide interface enhancement layer 6 is disposed on the two-dimensional semiconductor channel layer 4 in a fully covered or partially patterned manner.

[0045] In some specific embodiments, the molybdenum oxide interface enhancement layer 6 is disposed on the two-dimensional semiconductor channel layer 4 in a fully covering manner.

[0046] In other specific embodiments, the molybdenum oxide interface enhancement layer 6 is disposed on the two-dimensional semiconductor channel layer 4 in a locally patterned manner.

[0047] In one embodiment, the two-dimensional semiconductor channel layer 4 is a molybdenum disulfide layer.

[0048] In some specific embodiments, the molybdenum disulfide layer is a single-layer structure.

[0049] In some examples, the monolayer molybdenum disulfide layer is 0.7 nm.

[0050] In other specific embodiments, the molybdenum disulfide layer has a multilayer structure.

[0051] In some examples, the multilayer molybdenum disulfide layer is 3.5 nm thick. In other examples, the multilayer molybdenum disulfide layer is 2.1 nm thick.

[0052] In one embodiment, the subthreshold swing ranges from 70 mV / dec to 120 mV / dec.

[0053] In some specific embodiments, the operating point of the two-dimensional semiconductor channel layer 4 is 70mV / dec.

[0054] In other specific embodiments, the operating point of the two-dimensional semiconductor channel layer 4 is 120mV / dec.

[0055] In some specific embodiments, the operating point of the two-dimensional semiconductor channel layer 4 is 95mV / dec.

[0056] In one embodiment, the doping element of the doped silicon substrate 1 is boron, and the doping concentration ranges from 1×10⁻⁶. 19 atoms / cm 3 Up to 3×10 20 atoms / cm 3 .

[0057] In some specific embodiments, the doping concentration of the doped silicon substrate 1 is 1×10⁻⁶. 19 atoms / cm 3 .

[0058] In other specific embodiments, the doping concentration of the doped silicon substrate 1 is 3 × 10⁻⁶. 20 atoms / cm 3 .

[0059] In some specific embodiments, the doping concentration of the doped silicon substrate 1 is 1×10⁻⁶. 20 atoms / cm 3 .

[0060] As shown in Table 1, the response value is defined as the ratio of the change in current ΔI of the sensor in an ammonia atmosphere to the initial reference current I0. The response value does not strictly increase monotonically with concentration, which reflects the different MoO2 concentrations. x The complex influence of factors such as content, defect engineering, and test temperature on the response.

[0061]

[0062] As shown in Table 2, compared with the pure MoS2 sensor, the MoS2 / MoO constructed in this invention... x (x≤3) The heterojunction interface sensor showed a 9-fold increase in response at 100 ppm ammonia and a 6-fold increase at a low concentration of 1 ppm, confirming the effectiveness of ultrathin MoO2 interfaces. x The interface layer significantly enhances the sensitivity of ammonia detection.

[0063]

[0064] like Figure 2 As shown, according to the second embodiment of this application, a method for fabricating a semiconductor ammonia sensor is provided, comprising the following steps S1-S3: S1 provides a doped silicon substrate. A gate dielectric layer is formed on the doped silicon substrate.

[0065] S2 forms a two-dimensional semiconductor channel layer, source, and drain on the gate dielectric layer.

[0066] S3, the source and drain are located on opposite sides of the two-dimensional semiconductor channel layer. A molybdenum oxide interface enhancement layer is formed on the two-dimensional semiconductor channel layer.

[0067] like Figure 3 As shown, in some specific embodiments, S1 includes growing a gate dielectric layer 2 of SiO2 material on a heavily doped silicon substrate 1, or providing a gate dielectric layer 2 of SiO2 material.

[0068] like Figure 4 and Figure 5As shown, in some other specific embodiments, S2 includes forming a two-dimensional semiconductor channel layer 4 by chemical vapor deposition (CVD) of a monolayer of MoS2 on the gate dielectric layer 2. Source 31 and drain 32 are formed by photolithography and metal deposition, and are connected to the MoS2.

[0069] like Figure 6 and Figure 1 As shown, in one embodiment, forming a molybdenum oxide interface enhancement layer 6 on the two-dimensional semiconductor channel layer 4 includes: depositing a molybdenum layer 5 on the two-dimensional semiconductor channel layer 4; and oxidizing the deposited molybdenum layer 5 to form the molybdenum oxide interface enhancement layer 6.

[0070] In some specific embodiments, S3 includes forming the channel opening by photolithography, followed by depositing a Mo thin layer by electron beam evaporation or sputtering. After deposition, the layer is naturally oxidized in air to form MoO. x Thin layer.

[0071] The method and apparatus embodiments of this application can complement each other.

[0072] Regarding the apparatus in the above embodiments, the specific manner in which the processor performs the operation has been described in detail in the embodiments related to the method, and will not be elaborated upon here.

[0073] In this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "multiple" refers to two or more unless otherwise expressly defined.

[0074] The above description of the embodiments is intended to enable those skilled in the art to understand and apply this application. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, this application is not limited to the embodiments described herein, and any improvements and modifications made by those skilled in the art based on the disclosure of this application without departing from the scope and spirit of this application are within the scope of this application.

Claims

1. A semiconductor ammonia gas sensor, characterized in that, The semiconductor ammonia sensor includes a doped silicon substrate, a silicon dioxide gate dielectric layer, a two-dimensional semiconductor channel layer, a molybdenum oxide interface enhancement layer, a source electrode, and a drain electrode. The gate dielectric layer is located on the doped silicon substrate; The two-dimensional semiconductor channel layer, the source, and the drain are all located on the gate dielectric layer; The source and the drain are located on opposite sides of the two-dimensional semiconductor channel layer. The doped silicon substrate is used as a back gate electrode, and when a bias voltage is applied to the doped silicon substrate, it is used to control the operating point of the two-dimensional semiconductor channel layer within the subthreshold swing range. The molybdenum oxide interface enhancement layer is located on the two-dimensional semiconductor channel layer; The molybdenum oxide interface enhancement layer is used to undergo chemical adsorption upon contact with ammonia gas and generate an equivalent top-gate potential change. The field-effect amplification mechanism of the back gate electrode is used to convert the equivalent top-gate potential change into a drain current change.

2. The semiconductor ammonia sensor as described in claim 1, characterized in that, The thickness of the molybdenum oxide interface reinforcement layer ranges from 0.7 nm to 3.5 nm.

3. The semiconductor ammonia sensor as described in claim 2, characterized in that, The molybdenum oxide interface reinforcement layer is made of MoO. x , of which 0 <x≤3。 4. The semiconductor ammonia sensor as described in claim 1, characterized in that, The molybdenum oxide interface enhancement layer is disposed on the two-dimensional semiconductor channel layer in a fully covered or partially patterned manner.

5. The semiconductor ammonia sensor as described in claim 1, characterized in that, The two-dimensional semiconductor channel layer is a molybdenum disulfide layer.

6. The semiconductor ammonia sensor as described in claim 5, characterized in that, The molybdenum disulfide layer is a single-layer structure.

7. The semiconductor ammonia sensor as described in claim 1, characterized in that, The subthreshold swing range is from 70mV / dec to 120mV / dec.

8. The semiconductor ammonia sensor as described in claim 1, characterized in that, The doping element of the doped silicon substrate is boron, and the doping concentration ranges from 1×10⁻⁶. 19 atoms / cm 3 Up to 3×10 20 atoms / cm 3 .

9. A method for fabricating a semiconductor ammonia sensor, characterized in that, include: Provide a doped silicon substrate; A gate dielectric layer is formed on the doped silicon substrate; A two-dimensional semiconductor channel layer, a source, and a drain are formed on the gate dielectric layer; The source and the drain are located on opposite sides of the two-dimensional semiconductor channel layer. A molybdenum oxide interface enhancement layer is formed on the two-dimensional semiconductor channel layer.

10. The preparation method according to claim 9, characterized in that, A molybdenum oxide interface enhancement layer is formed on the two-dimensional semiconductor channel layer, comprising: A molybdenum layer is deposited on the two-dimensional semiconductor channel layer; The deposited molybdenum layer is oxidized to form the molybdenum oxide interface enhancement layer.

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