Pulse ultraviolet light excited semiconductor gas sensor and preparation method thereof

Abstract

The invention discloses a pulsed ultraviolet light excited semiconductor gas sensor and a preparation method, and belongs to the technical field of semiconductor gas sensors, the pulsed ultraviolet light excited semiconductor gas sensor sequentially comprises a substrate, a gate electrode, a gate dielectric layer, a sensitive material layer and a top electrode from bottom to top, and a pulsed light excitation device is arranged above the top electrode; the sensitive material layer is a P / N type or N / N type transverse heterojunction metal oxide semiconductor, the transverse heterojunction structure of the metal oxide can increase the interface area between the two sensitive materials, and ultraviolet light irradiates the metal electrode and the sensitive material layer in a pulse mode. The target gas is detected by detecting the threshold voltage of the semiconductor gas sensor device and the current parameter change of the drain electrode. The number of photo-generated free electron-hole pairs in the sensitive material is increased, so that the sensor does not need to be heated at a high temperature during working, the power consumption can be effectively reduced, and the application range of the gas sensor is expanded.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor gas sensors, and particularly relates to a semiconductor gas sensor excited by pulsed ultraviolet light and a preparation method thereof. Background Art

[0002] With the development of science and technology, gas sensors, as devices that can detect specific gas components and concentrations in the environment, are widely used in industrial safety monitoring, air quality detection, disease diagnosis, and intelligent wearable devices. Currently, the sensors available for gas detection mainly include electrochemistry types, solid dielectrics types, and semiconductor types. Among them, semiconductor gas sensors have been widely studied due to their advantages such as small volume, high sensitivity, and good physical and chemical stability.

[0003] A semiconductor gas sensor mainly consists of a substrate, a sensitive material, a heating element, and a detection electrode. And the sensitive material, as the core part of the gas sensor, the selection of its material, structure, and preparation process are crucial for aspects such as the sensitivity, stability, and selectivity of the sensor. Metal oxides, as sensitive materials, largely meet the performance requirements of gas sensors due to their excellent electrochemical properties. However, traditional metal oxide semiconductor materials usually require high-temperature heating to overcome the activation energy barrier of surface redox reactions. Therefore, gas sensors based on such sensitive materials not only have high power consumption, poor stability and reliability, but also have limited application scenarios.

[0004] Based on the fact that both light energy and heat energy can provide the required energy for metal oxide semiconductor materials, in recent years, photo-excited semiconductor gas sensors that use light energy instead of heat energy have received wide attention. According to the different wavelengths of the excitation light, currently, photo-excited semiconductor gas sensors mainly include visible light excitation and ultraviolet light excitation. Compared with visible light, the photon energy of ultraviolet light is relatively high. After irradiating the surface of the metal oxide sensitive material, it can excite photo-generated carriers and then catalyze the surface reaction of the material, achieving an improvement in the sensitivity response of the metal oxide semiconductor sensitive material to the gas to be detected under low-temperature conditions. However, currently, ultraviolet light-excited gas sensors are still in the initial stage of research, and there are still problems such as low detection sensitivity and poor stability, and there is still a large gap from actual applications. Summary of the Invention

[0005] Aiming at the above problems existing in the prior art, the present invention proposes a semiconductor gas sensor excited by pulsed ultraviolet light and a preparation method thereof, with reasonable design, solving the deficiencies of the prior art and having good effects.

[0006] A semiconductor gas sensor excited by pulsed ultraviolet light includes a substrate, and successively includes a substrate, a gate electrode, a gate dielectric layer, a sensitive material layer, and a top electrode from bottom to top. A pulsed light excitation device is provided above the top electrode.

[0007] Further, the substrate is any one of ceramic, silicon plate, polyimide, and polyester substrate.

[0008] Further, the top electrode includes a source electrode and a drain electrode, and the gate electrode, source electrode, and drain electrode are metal electrodes made of Ag, Au, Cu, or Pt.

[0009] Further, the sensitive material layer is a P / N-type or N / N-type lateral heterojunction metal oxide semiconductor, including doped and undoped metal oxide materials.

[0010] Further, the pulsed light excitation device is used to emit pulsed ultraviolet light, and when the pulsed ultraviolet light irradiates the surface of the device, it can excite electron-hole pairs in the sensitive film.

[0011] A preparation method of a semiconductor gas sensor excited by pulsed ultraviolet light as described above includes the following steps: S1. Respectively prepare N-type and P-type metal oxide precursor solutions containing indium metal ions, and a silicon substrate with a silicon nitride gate dielectric layer; S2. Clean the silicon substrate with acetone, isopropyl alcohol, and deionized water respectively and then dry it, and perform secondary cleaning treatment on the surface of the silicon substrate with a plasma cleaner to improve the surface hydrophilicity; S3. Prepare a multi-channel flexible mold with several linear micro-channels, press the mold on the gate dielectric layer, drop the selected N-type or P-type metal oxide precursor solution on one side of the mold, and make it flow into the linear micro-channels under the capillary force of the micro-channels, and then place it on a hot stage for pre-baking. After removing the mold, perform low-temperature annealing combined with pulsed ultraviolet light to obtain an N-type or P-type semiconductor layer with a linear structure; S4. Using the spin coating method, place the sample obtained in S3 in a spin coater, spin coat the N-type metal oxide precursor solution, then place it on a heating stage for pre-baking, and then perform low-temperature annealing combined with pulsed ultraviolet light to obtain a P / N-type or N / N-type metal oxide sensitive material layer with a horizontal lateral heterojunction structure; S5. Form the gate electrode, source electrode, and drain electrode by vacuum deposition to finally obtain a semiconductor gas sensor based on a lateral heterojunction semiconductor material; S6. Irradiate the top electrode and the sensitive material layer with ultraviolet light in a pulsed form, and realize the detection of the target gas by detecting the changes in the threshold voltage and drain electrode current parameters of the semiconductor gas sensor.

[0012] Further, the linear width of the linear micro-channel is <5 μm, the length is <15 μm, the row spacing is <1 μm, and the pattern height is <50 nm.

[0013] Further, the thickness of the sensitive material layer is 20-50 nm, the thickness of the gate dielectric layer is 50-100 nm, and the thicknesses of the gate electrode, source electrode, and drain electrode are 10-200 nm.

[0014] Further, the pulsed light excitation device is disposed at a distance of 0-30 cm from the sensitive material layer, with a power of 300-800 W and a frequency of 5-20 Hz.

[0015] The beneficial technical effects brought by the present invention: Compared with the existing metal oxide sensitive materials annealed at high temperature, the sensitive material of the present invention using the optimized technology of metal oxide semiconductor materials and low-temperature annealing technology has, on the one hand, a low material forming temperature, which can reduce the dependence of the sensitive material on high-temperature heat energy, improve the sensitivity to the gas to be measured under low-temperature conditions, and enhance the stability of the gas sensor; on the other hand, the lateral heterojunction structure of the metal oxide can increase the interface area between the two sensitive materials, while strengthening the sensing characteristics of the sensitive material, making the sensitive material have rich material selectivity and diverse combinability.

[0016] Compared with the existing photo-excited gas sensors, the device structure of the pulsed ultraviolet light-excited gas sensor of the present invention irradiates ultraviolet light in the form of pulses onto the device surface, enhancing the provided light energy, increasing the number of photo-generated free electron-hole pairs in the sensitive material, enabling the sensor to operate without high-temperature heating, effectively reducing its power consumption, and expanding the application range of the gas sensor. The present invention provides a new method for the development of a new generation of ultraviolet light-excited gas sensors, effectively promoting the practical application of gas sensors. Description of the Drawings

[0017] Figure 1 It is a schematic structural diagram of a pulsed ultraviolet light-excited semiconductor gas sensor provided by the present invention.

[0018] Figure 2 It is a preparation flow chart of the P / N type or N / N type lateral heterojunction metal oxide material in the embodiment of the present invention.

[0019] Figure 3 It is a comparison chart of the carrier concentration and resistivity of the sensitive material before and after pulsed ultraviolet light irradiation in the embodiment of the present invention.

[0020] Among them, 1 - substrate; 2 - gate electrode; 3 - gate dielectric layer; 4 - P-type or N-type metal oxide semiconductor layer; 5 - N-type metal oxide semiconductor layer; 6 - top electrode; 7 - pulsed light excitation device; 8 - N-type or P-type metal oxide precursor solution; 9 - flexible mold; 10 - N-type metal oxide precursor solution. Detailed Embodiments

[0021] The following further describes the specific implementation manners of the present invention in conjunction with specific embodiments: A semiconductor gas sensor excited by pulsed ultraviolet light, as Figure 1 shown, sequentially includes a substrate 1, a gate electrode 2, a gate dielectric layer 3, a sensitive material layer, and a top electrode 6 from bottom to top. A pulsed light excitation device 7 is provided above the top electrode 6.

[0022] The substrate 1 is a rigid substrate or a flexible substrate. The rigid substrate is made of ceramic or silicon plate, and the flexible substrate is made of polyimide or polyester substrate.

[0023] The top electrode 6 includes a source electrode and a drain electrode. The gate electrode, source electrode, and drain electrode are metal electrodes, made of Ag, Au, Cu, or Pt.

[0024] The sensitive material layer is a P / N-type or N / N-type lateral heterojunction metal oxide semiconductor, including doped and undoped metal oxide materials. The sensitive material layer is composed of a P-type or N-type metal oxide semiconductor layer 4 and an N-type metal oxide semiconductor layer 5 arranged horizontally and alternately. The two metal oxide sensitive material layers respectively adopt doped or undoped N-type or P-type metal oxide semiconductor materials to form a sensitive material layer with a P / N-type or N / N-type lateral heterojunction structure.

[0025] The pulsed light excitation device is used to emit pulsed ultraviolet light, and the pulsed ultraviolet light irradiates the device surface from top to bottom, which can excite electron-hole pairs in the sensitive film.

[0026] A preparation method of a semiconductor gas sensor excited by pulsed ultraviolet light includes the following steps: S1. Respectively prepare N-type and P-type metal oxide precursor solutions containing metal ions, and a silicon substrate (Si / SiN x ) with a silicon nitride gate dielectric layer; S2. Clean the silicon substrate with acetone, isopropyl alcohol, and deionized water respectively, then dry it, and perform secondary cleaning treatment on the surface of the silicon substrate with a plasma cleaner to improve the surface hydrophilicity; S3. Prepare a multi-channel flexible mold 9. The mold is provided with several linear micro-channels. The linear length of the linear micro-channels is <5 μm, the width is <15 μm, the row spacing is <1 μm, and the pattern height / depth is <50 nm. Press the mold on the gate dielectric layer, drop the selected N-type or P-type metal oxide precursor solution 8 on one side of the mold, and let it flow into the linear micro-channels under the capillary force of the micro-channels, as Figure 2 shown. Then place it on a hot stage for pre-baking. After removing the mold, perform low-temperature annealing combined with pulsed ultraviolet light to obtain a linear N-type or P-type semiconductor layer; S4. Using the spin-coating method, place the sample obtained in S3 in a spin coater and coat the N-type metal oxide precursor solution 10 in a spin-coating manner. Then, place the substrate on a heating stage for pre-baking, and then perform low-temperature annealing in combination with pulsed ultraviolet light to obtain a P / N-type or N / N-type metal oxide sensitive material layer with a horizontal heterojunction structure, such as Figure 2 shown; S5. Form the gate electrode, source electrode, and drain electrode by vacuum deposition, and finally obtain a semiconductor gas sensor based on a lateral heterojunction semiconductor material; S6. Irradiate the top electrode and the sensitive material layer with ultraviolet light in the form of pulses, and detect the target gas by detecting changes in parameters such as the threshold voltage and drain electrode current of the gas sensor.

[0027] Example 1: A preparation method of a semiconductor gas sensor excited by pulsed ultraviolet light, comprising the following steps: S1. Respectively prepare N-type and P-type metal oxide precursor solutions containing zinc ions and indium ions, and a silicon substrate (Si / SiN x ) with a silicon nitride gate dielectric layer, and the thickness of the gate dielectric layer is 50 - 100 nm; S2. Use acetone, isopropyl alcohol, and deionized water to perform ultrasonic cleaning on the silicon substrate for 15, 30, and 60 minutes respectively, so that the surface of SiN x is clean and free of organic substances. After drying with nitrogen and baking, remove the moisture and oxidizing or reducing gases remaining on the surface of the silicon substrate. Finally, use a plasma cleaner to perform secondary cleaning on the surface of the silicon substrate to improve its hydrophilicity; S3. Prepare a multi-channel flexible replication mold with a mold linear length < 5 μm; width < 15 μm; row spacing < 1 μm; pattern height / depth < 50 nm. Press the multi-channel mold on the gate dielectric layer, drop the selected zinc oxide precursor solution on one side of the mold, and let the semiconductor solution flow into the microchannels under the action of microchannel capillary force, as Figure 2 shown. Place it on a heating stage for pre-baking at 120 °C for 10 minutes, and then remove the mold and perform annealing at 200 °C for 20 minutes in combination with pulsed ultraviolet light to obtain an N-type zinc oxide semiconductor layer with a linear structure, with a thickness of 20 - 50 nm; S4. Place the sample obtained in S3 in a spin coater and spin-coat it at 5000 rpm for 35 s to obtain a sample coated with an N-type indium oxide precursor solution. Then, place it on a heating stage for pre-baking at 120 °C for 10 minutes, and then perform annealing at 200 °C for 5 minutes in combination with pulsed ultraviolet light to obtain an N / N-type metal oxide sensitive material layer with a horizontal heterojunction structure, as Figure 2 shown, with a thickness of 20 - 50 nm; S5. Fabricate metal electrodes: By means of vacuum deposition, form the gate electrode, source electrode and drain electrode, and finally obtain the semiconductor gas sensor. The thickness of the three metal electrodes is 10 - 200 nm, the length of the conductive channel is L = 80 μm, and the width is W = 2000 μm; S6. Finally, irradiate the surface of the device with pulsed ultraviolet light above the semiconductor gas sensor. Among them, the power of the light source is 500 W, the frequency is 15 Hz, and the distance from the sensor device is 10 cm.

[0028] As Figure 3 shown, based on the Hall effect measurement system, the carrier concentration and resistivity of the sensitive material before and after irradiating the device with pulsed ultraviolet light were measured. It can be seen that the carrier concentration in the embodiment increased significantly, and the resistivity decreased significantly, indicating that exciting the sensitive material in the form of pulses with ultraviolet light can significantly increase the number of photo-generated free electron-hole pairs. And a semiconductor material with a high carrier concentration can respond to the adsorption and desorption of gas molecules faster, thereby shortening the response time of the sensor and achieving the purpose of improving the performance of the gas sensor.

[0029] Certainly, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the essence of the present invention should also fall within the protection scope of the present invention.

Claims

1. A semiconductor gas sensor excited by pulsed ultraviolet light, characterized in that: The invention comprises, from bottom to top, a substrate, a gate electrode, a gate dielectric layer, a sensitive material layer and a top electrode, and a pulse light excitation device is arranged above the top electrode.

2. A pulsed ultraviolet light excited semiconductor gas sensor according to claim 1, characterized in that: The substrate is any one of ceramic, silicon, polyimide and polyester substrates.

3. A pulsed ultraviolet light excited semiconductor gas sensor according to claim 2, characterized in that: The top electrode includes a source electrode and a drain electrode. The gate electrode, the source electrode and the drain electrode are metal electrodes, and are made of Ag, Au, Cu or Pt.

4. A pulsed ultraviolet light excited semiconductor gas sensor according to claim 3, characterized in that: The sensitive material layer is a P / N type or N / N type lateral heterojunction metal oxide semiconductor, including doped and undoped metal oxide materials.

5. A pulsed ultraviolet light excited semiconductor gas sensor according to claim 4, characterized in that: The pulse light excitation device is used to emit pulse ultraviolet light, and the pulse ultraviolet light is irradiated to the surface of the device to excite the electron-hole pairs in the sensitive film.

6. A method for preparing a semiconductor gas sensor excited by pulsed ultraviolet light according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, respectively preparing N-type and P-type metal oxide precursor solutions containing metal indium ions, and a silicon substrate having a silicon nitride gate dielectric layer; S2, using acetone, isopropanol and deionized water to clean the silicon substrate respectively and then drying it, and using a plasma cleaning machine to perform a secondary cleaning treatment on the surface of the silicon substrate to improve the hydrophilicity of the surface; S3. Prepare a multi-channel flexible mold, the mold is provided with a plurality of linear microchannels, press the mold on the gate dielectric layer, drop the selected N-type or P-type metal oxide precursor solution on one side of the mold, so that it flows into the linear microchannel under the action of the microchannel capillary force, and then place it on a hot plate for pre-baking. After removing the mold, low-temperature annealing is performed in combination with pulsed ultraviolet light to obtain a linear structured N-type or P-type semiconductor layer; S4, using a spin coating method, placing the sample obtained in S3 in a coater, coating it with an N-type metal oxide precursor solution by spin coating, and then placing it on a heating table for pre-baking, and then performing low-temperature annealing with pulsed ultraviolet light to obtain a P / N-type or N / N-type metal oxide sensitive material layer with a horizontal lateral heterojunction structure; S5, forming a gate electrode, a source electrode and a drain electrode by vacuum deposition, and finally obtaining a semiconductor gas sensor based on a lateral heterojunction semiconductor material; S6. Irradiate the top electrode and the sensitive material layer with ultraviolet light in the form of pulses, and detect the target gas by detecting the changes in the threshold voltage and drain electrode current parameters of the semiconductor gas sensor.

7. The method for preparing a semiconductor gas sensor excited by pulsed ultraviolet light according to claim 6, characterized in that: The linear microchannel has a linear width of less than 5 μm, a length of less than 15 μm, a line spacing of less than 1 μm, and a pattern height of less than 50 nm.

8. The method for preparing a semiconductor gas sensor excited by pulsed ultraviolet light according to claim 7, characterized in that: The thickness of the sensitive material layer is 20-50 nm, the thickness of the gate dielectric layer is 50-100 nm, and the thickness of the gate electrode, source electrode and drain electrode is 10-200 nm.

9. The method for preparing a semiconductor gas sensor excited by pulsed ultraviolet light according to claim 8, characterized in that: The pulse light excitation device is set at a distance of 0-30 cm from the sensitive material layer, with a power of 300-800 W and a frequency of 5-20 Hz.

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