A semiconductor gas sensor excited by pulsed ultraviolet light and its preparation method

Abstract

The present invention discloses a pulsed ultraviolet light-excited semiconductor gas sensor and its preparation method, belonging to the field of semiconductor gas sensor technology. The sensor comprises, from bottom to top, a substrate, a gate electrode, a gate dielectric layer, a sensitive material layer, and a top electrode. A pulsed light excitation device is positioned above the top electrode. The sensitive material layer comprises a P / N or N / N lateral heterojunction metal oxide semiconductor. The lateral heterojunction structure of the metal oxide increases the interface area between the two sensitive materials. Ultraviolet light is pulsed onto the metal electrode and the sensitive material layer. Detection of the target gas is achieved by measuring changes in the threshold voltage and drain current parameters of the semiconductor gas sensor device. This method increases the number of photogenerated free electron-hole pairs in the sensitive material, eliminating the need for high-temperature heating during sensor operation, effectively reducing power consumption and expanding the application range of gas sensors.

Description

Technical Field

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

[0002] With the advancement of science and technology, gas sensors, as devices that can detect the composition and concentration of specific gases in the environment, have been widely used in industrial safety monitoring, air quality monitoring, disease diagnosis, and smart wearable devices. Currently, sensors used for gas detection primarily include electrochemical, solid dielectric, and semiconductor types. Semiconductor gas sensors, among others, have been widely researched due to their small size, high sensitivity, and excellent physical and chemical stability.

[0003] Semiconductor gas sensors primarily consist of a substrate, sensitive material, heating element, and detection electrodes. As the core component of a gas sensor, the selection, structure, and preparation process of the sensitive material are crucial to the sensor's sensitivity, stability, and selectivity. 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 typically require high-temperature heating to overcome the activation energy barrier of surface redox reactions. Consequently, gas sensors based on these sensitive materials suffer from high power consumption, poor stability, and reliability, and limited application scenarios.

[0004] Since both light energy and thermal energy can provide the required energy for metal oxide semiconductor materials, photoexcitation-type semiconductor gas sensors that use light energy instead of thermal energy have received widespread attention in recent years. Depending on the wavelength of the excitation light, there are currently two main types of photoexcitation-type semiconductor gas sensors: visible light excitation and ultraviolet light excitation. Compared to visible light, the photon energy of ultraviolet light is relatively high. After irradiating the surface of metal oxide sensitive materials, it can excite photogenerated carriers and then catalyze the surface reaction of the material, thereby improving the sensitivity response of the metal oxide semiconductor sensitive material to the gas to be measured under low temperature conditions. However, ultraviolet light excitation-type gas sensors are still in the preliminary stage of research, and there are still problems such as low detection sensitivity and poor stability, which are still far from practical application. Summary of the Invention

[0005] In response to the above problems existing in the prior art, the present invention proposes a pulsed ultraviolet light excited semiconductor gas sensor and a preparation method thereof, which has a reasonable design, solves the deficiencies of the prior art, and has good effects.

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

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

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

[0009] Furthermore, 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] Furthermore, the pulsed light excitation device is used to emit pulsed ultraviolet light, and the pulsed ultraviolet light is irradiated to the surface of the device to excite electron-hole pairs in the sensitive film.

[0011] A method for preparing the semiconductor gas sensor excited by pulsed ultraviolet light as described above comprises the following steps:

[0012] 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;

[0013] S2. The silicon substrate is cleaned with acetone, isopropyl alcohol and deionized water respectively and then dried. The surface of the silicon substrate is then cleaned again with a plasma cleaner to improve the hydrophilicity of the surface.

[0014] S3. Prepare a multi-channel flexible mold with several linear microchannels. Press the mold onto the gate dielectric layer. Drop a selected N-type or P-type metal oxide precursor solution onto one side of the mold, allowing it to flow into the linear microchannels under the capillary force of the microchannels. Then, place the mold on a hot plate for pre-baking. After removing the mold, perform low-temperature annealing with pulsed ultraviolet light to obtain a linear N-type or P-type semiconductor layer.

[0015] S4. Using a spin coating method, the sample obtained in S3 is placed in a spin coater and coated with an N-type metal oxide precursor solution by spin coating. The sample is then placed on a heating table for pre-baking, and then low-temperature annealing is performed 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.

[0016] S5. Forming a gate electrode, a source electrode, and a drain electrode by vacuum deposition, thereby finally obtaining a semiconductor gas sensor based on a lateral heterojunction semiconductor material;

[0017] 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.

[0018] Furthermore, the linear microchannel has a linear width of <5 μm, a length of <15 μm, a line spacing of <1 μm, and a pattern height of <50 nm.

[0019] Furthermore, 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.

[0020] Furthermore, 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.

[0021] Beneficial technical effects brought about by the present invention:

[0022] Compared with existing high-temperature annealed metal oxide sensitive materials, the sensitive material described in the present invention, which utilizes the optimization technology and low-temperature annealing technology of metal oxide semiconductor materials, has, on the one hand, a low material forming temperature, which can reduce the sensitive material's dependence on high-temperature thermal 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, thereby enhancing the sensing characteristics of the sensitive material while giving the sensitive material rich material selectivity and diverse combinations.

[0023] Compared to existing photoexcited gas sensors, the pulsed UV-light-excited gas sensor structure described in this invention utilizes pulsed UV light to illuminate the device surface, enhancing the provided light energy and increasing the number of photogenerated free electron-hole pairs in the sensitive material. This eliminates the need for high-temperature heating during sensor operation, effectively reducing power consumption and expanding the application range of gas sensors. This invention provides a novel approach to the development of a new generation of UV-light-excited gas sensors, effectively promoting their practical application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic structural diagram of a pulsed ultraviolet light excited semiconductor gas sensor provided by the present invention.

[0025] Figure 2 1 is a flow chart for preparing a P / N or N / N type lateral heterojunction metal oxide material in an embodiment of the present invention.

[0026] Figure 3 3 is a comparison diagram of the carrier concentration and resistivity of the sensitive material before and after pulsed ultraviolet light irradiation in an embodiment of the present invention.

[0027] 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 DESCRIPTION

[0028] The specific implementation of the present invention will be further described below with reference to specific embodiments:

[0029] A semiconductor gas sensor excited by pulsed ultraviolet light, such as Figure 1 As shown, the structure includes, from bottom to top, a substrate 1 , a gate electrode 2 , a gate dielectric layer 3 , a sensitive material layer and a top electrode 6 , and a pulse light excitation device 7 is provided above the top electrode 6 .

[0030] The substrate 1 is a rigid substrate or a flexible substrate. The rigid substrate is made of ceramic or silicon board, and the flexible substrate is made of polyimide or polyester substrate.

[0031] The top electrode 6 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.

[0032] 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 horizontal alternating arrangement of P-type or N-type metal oxide semiconductor layers 4 and N-type metal oxide semiconductor layers 5. The two metal oxide sensitive material layers are respectively made of doped or undoped N-type or P-type metal oxide semiconductor materials, forming a sensitive material layer with a P / N-type or N / N-type lateral heterojunction structure.

[0033] The pulsed light excitation device is used to emit pulsed ultraviolet light, which irradiates the surface of the device from top to bottom and can excite electron-hole pairs in the sensitive film.

[0034] A method for preparing a semiconductor gas sensor excited by pulsed ultraviolet light comprises the following steps:

[0035] S1, respectively prepare N-type and P-type metal oxide precursor solutions containing metal ions, and a silicon substrate with a silicon nitride gate dielectric layer (Si / SiN x );

[0036] S2. The silicon substrate is cleaned with acetone, isopropyl alcohol and deionized water respectively and then dried. The surface of the silicon substrate is then cleaned again with a plasma cleaner to improve the hydrophilicity of the surface.

[0037] S3. Prepare a multi-channel flexible mold 9, which has a plurality of linear microchannels. The linear length of the linear microchannels is less than 5 μm, the width is less than 15 μm, the line spacing is less than 1 μm, and the pattern height / depth is less than 50 nm. Press the mold onto the gate dielectric layer, and drop the selected N-type or P-type metal oxide precursor solution 8 on one side of the mold. The solution flows into the linear microchannels under the capillary force of the microchannels. Figure 2 As shown, it is then placed on a hot plate for pre-baking, and after the mold is removed, low-temperature annealing is performed in combination with pulsed ultraviolet light to obtain an N-type or P-type semiconductor layer with a linear structure;

[0038] S4, using the spin coating method, placing the sample obtained in S3 in a spin coater, and coating the N-type metal oxide precursor solution 10 by spin coating, then placing the substrate on a heating table for pre-baking, and then combining pulsed ultraviolet light for low-temperature annealing to obtain a horizontal lateral heterojunction structure of P / N type or N / N type metal oxide sensitive material layer, such as Figure 2 As shown;

[0039] S5. Forming a gate electrode, a source electrode, and a drain electrode by vacuum deposition, thereby finally obtaining a semiconductor gas sensor based on a lateral heterojunction semiconductor material;

[0040] 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 parameters such as the threshold voltage and the drain electrode current of the gas sensor.

[0041] Example 1:

[0042] A method for preparing a semiconductor gas sensor excited by pulsed ultraviolet light comprises the following steps:

[0043] S1, respectively prepare N-type and P-type metal oxide precursor solutions containing zinc ions and indium ions, and a silicon substrate with a silicon nitride gate dielectric layer (Si / SiN x ), the thickness of the gate dielectric layer is 50~100 nm;

[0044] S2, use acetone, isopropyl alcohol and deionized water to carry out ultrasonic cleaning for 15, 30 and 60 minutes respectively to make SiN x The surface is clean and free of organic matter. It is dried with nitrogen and then dried to remove the residual moisture and oxidizing or reducing gases on the surface of the silicon substrate. Finally, a plasma cleaning machine is used to perform a secondary cleaning treatment on the surface of the silicon substrate to improve the hydrophilicity of the surface.

[0045] S3. Prepare a multi-channel flexible replication mold with a mold line length <5 μm; width <15 μm; line spacing <1 μm; pattern height / depth <50 nm; press the multi-channel mold onto the gate dielectric layer, drop the selected zinc oxide precursor solution on one side of the mold, and allow the semiconductor solution to flow into the microchannel under the action of the microchannel capillary force, as shown in FIG. Figure 2 As shown, it was placed on a hot plate and pre-baked at 120 ° C for 10 minutes, and then the mold was removed and annealed at 200 ° C for 20 minutes under pulsed ultraviolet light to obtain a linear N-type zinc oxide semiconductor layer with a thickness of 20~50 nm;

[0046] S4. Place the sample obtained in S3 in a spin coater and spin coat at 5000 rpm for 35 s to obtain a sample coated with an N-type indium oxide precursor solution. Then, place the sample on a heating table and pre-bake it at 120 °C for 10 min. Then, anneal it at 200 °C for 5 min using pulsed ultraviolet light to obtain an N / N-type metal oxide sensitive material layer with a horizontal lateral heterojunction structure, as shown in FIG. Figure 2 As shown, the thickness is 20~50 nm;

[0047] S5. Prepare metal electrodes: Use vacuum deposition to form gate, source, and drain electrodes, ultimately producing a semiconductor gas sensor. The thickness of the three metal electrodes ranges from 10 to 200 nm, and the conductive channel has a length of 80 μm and a width of 2000 μm.

[0048] S6. Finally, a pulsed ultraviolet light is applied to the surface of the semiconductor gas sensor. The power of the light source is 500 W, the frequency is 15 Hz, and the distance from the sensor device is 10 cm.

[0049] like Figure 3 As shown, the carrier concentration and resistivity of the sensitive material before and after the device was irradiated with pulsed ultraviolet light were tested based on the Hall effect measurement system. It can be seen that the carrier concentration of the embodiment increased significantly and the resistivity decreased significantly, indicating that exciting the sensitive material with ultraviolet light in the form of pulses can greatly increase the number of photogenerated free electron-hole pairs, and semiconductor materials with high carrier concentration can respond to the adsorption and desorption of gas molecules more quickly, thereby shortening the response time of the sensor and achieving the purpose of improving the performance of the gas sensor.

[0050] Of course, 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 technicians in this technical field within the essential scope of the present invention should also fall within the scope of protection of the present invention.

Claims

1. A semiconductor gas sensor excited by pulsed ultraviolet light, characterized in that: From bottom to top, it includes a substrate, a gate electrode, a gate dielectric layer, a sensitive material layer and a top electrode, and a pulse light excitation device is provided above the top electrode; The sensitive material layer is a P / N type or N / N type lateral heterojunction metal oxide semiconductor, which is composed of P type or N type metal oxide semiconductor layers and N type metal oxide semiconductor layers arranged horizontally and alternately, including doped and undoped metal oxide materials; The preparation method of the semiconductor gas sensor comprises the following steps: 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. The silicon substrate is cleaned with acetone, isopropyl alcohol and deionized water respectively and then dried. The surface of the silicon substrate is then cleaned again with a plasma cleaner to improve the hydrophilicity of the surface. S3. Prepare a multi-channel flexible mold with several linear microchannels. Press the mold onto the gate dielectric layer. Drop a selected N-type or P-type metal oxide precursor solution onto one side of the mold, allowing it to flow into the linear microchannels under the capillary force of the microchannels. Then, place the mold on a hot plate for pre-baking. After removing the mold, perform low-temperature annealing with pulsed ultraviolet light to obtain a linear N-type or P-type semiconductor layer. S4. Using a spin coating method, the sample obtained in S3 is placed in a spin coater and coated with an N-type metal oxide precursor solution by spin coating. The sample is then placed on a heating table for pre-baking, and then low-temperature annealing is performed 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, thereby finally obtaining a semiconductor gas sensor based on a lateral heterojunction semiconductor material; S6. Irradiating the top electrode and the sensitive material layer with ultraviolet light in a pulsed form, and detecting the target gas by detecting the changes in the threshold voltage and drain electrode current parameters of the semiconductor gas sensor; 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.

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

3. The semiconductor gas sensor excited by pulsed ultraviolet light according to claim 1, 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. The semiconductor gas sensor excited by pulsed ultraviolet light according to claim 1, characterized in that: The pulse light excitation device is used to emit pulsed ultraviolet light, and the pulsed ultraviolet light is irradiated to the surface of the device to excite electron-hole pairs in the sensitive film.

5. The semiconductor gas sensor excited by pulsed ultraviolet light according to claim 1, 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.

6. The semiconductor gas sensor excited by pulsed ultraviolet light according to claim 1, 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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