In2O3 nano material oriented growth method, device, sensor and electronic nose

Abstract

The invention discloses a directional growth method, device, sensor and electronic nose of an In2O3 nano material, and the method comprises the following steps: preparing a silicon substrate with a heating electrode and a test electrode as an In2O3 growth carrier; trimethyl indium is used as an indium gas source, oxygen is used as an oxygen source, and the In2O3 nano material grows in an oriented manner under the thermal induction of a micro-area formed by a heating electrode through chemical vapor deposition. And the height consistency of the gas sensitive materials in each micro-region on the wafer is realized, so that the high-consistency processing of the wafer-level sensor is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor metal oxide functional materials, and particularly relates to a method and device for the directional growth of In2O3 nanomaterials, a sensor, and an electronic nose. Background Art

[0002] Asthma, as a common chronic respiratory disease, seriously affects the health of hundreds of millions of people globally. To date, early diagnosis and precise treatment are crucial for controlling the development of asthma and improving the quality of life of patients. As a non-invasive detection technology, exhaled gas detection has become a hot research direction in asthma detection in recent years because it can conveniently and real-time obtain human physiological and pathological information. It has been found that exhaled gases of asthma patients contain various specific biomarkers, such as volatile organic compounds like nitric oxide. By detecting the concentration changes of these biomarkers, it is expected to achieve early non-invasive diagnosis of asthma. Among them, as a key device for exhaled gas detection, the electronic nose can give full play to its advantages by improving the consistency of the key performance requirements of each element in its internal sensor array after normalization, so that the accuracy and reliability of the detection results meet the clinical requirements. Therefore, developing high-performance and well-consistent sensors is the key to improving the detection performance of the electronic nose and breaking through the technical bottleneck of asthma exhaled gas detection.

[0003] Metal oxide semiconductor (MOS) nanomaterials have shown great application potential in the field of gas-sensing due to their unique size effect, surface effect, and quantum size effect, etc. As an important member of MOS nanomaterials, In2O3 has advantages such as a wide bandgap, good electrical properties, and chemical stability, and performs outstandingly in gas-sensing detection, especially suitable for the detection of specific VOCs in asthma exhaled gas. The prior art has the manufacturing problem that it is difficult to achieve both high sensitivity, high stability, and device consistency in micro-nano gas sensors.

[0004] The above information disclosed in the background art section is only used to enhance the understanding of the background of the present invention, and thus may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0005] The present invention provides a method, device, sensor and electronic nose for directional growth of In2O3 nanomaterials. In2O3 nanomaterials are prepared by a large-area wafer manufacturing process. The highly consistent directional growth of In2O3 nanomaterials solves the technical problem that high performance and high consistency cannot be taken into account when preparing large-area nano gas-sensitive materials. The wafer-level integration of micron-scale structures and nano gas-sensitive materials can be achieved, thereby solving the manufacturing problem that it is difficult to achieve high sensitivity, high stability and device consistency of micro-nano gas sensors. The uniform and consistent controllable growth of nanomaterials is achieved in the micron-scale area defined on the entire wafer, which ensures that each sensor chip has highly consistent micro-nano scale structural characteristics, including optimization of crystal structure, directional guidance of growth orientation, and precise regulation of size and morphology. It provides strong technical support for the electronic nose to detect and analyze trace complex gases.

[0006] A method for directional growth of In2O3 nanomaterials comprises: Step S1, preparing a silicon substrate with a heating electrode and a test electrode as an In2O3 growth carrier; Step S2, using trimethylindium as an indium gas source and oxygen as an oxygen source, chemical vapor deposition is performed to directionally grow In2O3 nanomaterials in a micro-area formed by a heating electrode under thermal induction.

[0007] In the method for directional growth of In2O3 nanomaterials, step S1 comprises: Step S11, pre-treating the silicon substrate, placing the silicon substrate in acetone and ethanol solutions for ultrasonic cleaning in turn; Step S12, using a MEMS process to form at least one MEMS micro-hotplate on a silicon substrate as an In2O3 growth carrier, wherein the MEMS micro-hotplate includes a plurality of groups of heating electrodes and test electrodes with consistent structures.

[0008] In the method for directional growth of In2O3 nanomaterials, step S2 comprises: Step S21, regulating the dual-temperature zone reactor, installing the MEMS micro-hotplate in the reaction deposition zone of the dual-temperature zone reactor, closing the reactor chamber, and evacuating the pressure in the reactor chamber to a predetermined pressure range; Step S22, In2O3 nanomaterial growth parameter control, adjust the flow rate of trimethyl indium vapor so that it is carried by the carrier gas into the reaction chamber, and at the same time adjust the O2 flow rate, connect the DC power supply to the positive and negative poles of the heating electrode of the MEMS micro-hotplate, adjust the current size according to the resistance of the heating electrode and the target heating temperature, so that the heating electrode is heated to form a micro-area thermal field on the silicon substrate, and the trimethyl indium vapor and oxygen react chemically under the high temperature environment in the reaction deposition area, and indium oxide nanomaterials are directionally grown in the heating area of ​​the silicon substrate.

[0009] In the described method for the directional growth of In2O3 nanomaterials, in step S11, the silicon substrate is successively placed in acetone and ethanol solution and ultrasonically cleaned for 15 - 20 minutes to remove surface oil stains and organic impurities. In step S12, the materials for depositing the heating electrode and the test electrode on the silicon substrate are Au, and the deposition thickness is between 100 - 400 nm. A layer of Cr with a thickness of 10 - 100 nm is deposited between Au and the silicon substrate to increase the adhesion between the electrode and the substrate.

[0010] In the described method for the directional growth of In2O3 nanomaterials, in step S12, the test electrode is isolated from the heating electrode through a dielectric layer and is within the microzone controlled by the temperature of the MEMS micro - hotplate.

[0011] In the described method for the directional growth of In2O3 nanomaterials, in step S21, the pressure in the chamber is pumped to a predetermined pressure range of 10 -1 - 10 -3 Pa by a vacuum pump. In step S22, the growth time of the In2O3 thin film, the microzone heating temperature on the silicon substrate, and the flow rates of trimethylindium vapor and O2 are controlled to directionally grow indium oxide nanomaterials.

[0012] In the described method for the directional growth of In2O3 nanomaterials, the same temperature in each microzone results in consistent In2O3 nanomaterials, or the temperature distribution and gradient change in each microzone enable the directional and controllable growth of In2O3 nanomaterials in each microzone.

[0013] A directional growth device for implementing the described method includes A tube furnace, which is provided with a reaction chamber and an air inlet communicating with the reaction chamber. The tube furnace is provided with a porcelain boat for loading trimethylindium to form trimethylindium vapor. A carrier gas source, which is provided with a carrier gas for transporting trimethylindium and is connected to the air inlet. An oxygen source, which is provided with oxygen and is connected to the air inlet. A flow controller, which is connected to the carrier gas source and the oxygen source to adjust the flow rates of trimethylindium vapor and O2 and their ratio. A vacuum pump, which is connected to the reaction chamber to evacuate the air. A pressure gauge, which is connected to the reaction chamber to detect pressure data. A MEMS micro - hotplate, which is arranged in the reaction chamber and in the reaction gas composed of trimethylindium vapor and O2. The MEMS micro - hotplate includes a heating electrode and a test electrode. A DC power supply device, which is connected to the heating electrode to heat and form a microzone. A temperature control console is connected to a DC power supply device to adjust the temperature of a micro-region. Indium oxide nanomaterials are directionally grown in the micro-region of a MEMS micro-hotplate.

[0014] An In2O3 sensor is fabricated by the method described above.

[0015] An electronic nose includes the In2O3 sensor.

[0016] Compared with the prior art, the present invention has the following advantages: Precise growth position control. By fabricating heating electrodes on a silicon substrate through MEMS technology and connecting an external power supply, local thermal field control can be achieved on the silicon substrate, accurately defining the growth region of In2O3 and meeting the strict requirements for the growth position of materials in different application scenarios. High-quality material growth: The independently controllable temperature environment of the double-temperature zone reaction furnace can optimize the ratio of indium source gas to O2, growth temperature, and time conditions respectively, effectively improving the crystallization quality, surface flatness, and electrical property consistency of indium oxide thin films, making it more suitable for high-performance semiconductor devices, sensors, and other fields. Good repeatability and stability: The MEMS technology and precise control parameters of each device adopted in the present invention make the entire In2O3 growth process have good repeatability and stability. In experiments of different batches, highly consistent In2O3 materials with similar performance can be prepared. Using the micro-region thermal field induction technology to prepare high-performance In2O3 sensors with good consistency in the same batch is expected to significantly improve the consistency among sensors of the electronic nose, providing strong technical support for accurately detecting biomarkers in asthma exhalation, improving the accuracy and reliability of asthma diagnosis, and promoting the asthma exhalation detection technology to a new stage of development. Description of the Drawings

[0017] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of showing the preferred embodiments and are not considered as limiting the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. Moreover, throughout the drawings, the same reference numerals are used to represent the same components.

[0018] In the drawings: Figure 1 is the preparation process flow of the MEMS micro-hotplate in the present invention; Figures 2(a) to 2(b) are schematic diagrams of the front test and heating pattern layout on the MEMS micro-hotplate in the present invention; Figure 3 is a schematic diagram of the circuit connection method between local micro-hotplates extracted from the wafer in the present invention; Figure 4 It is a schematic structural diagram of the In2O3 directional growth device based on MEMS technology and micro-region thermal field control in the present invention; Figure 5 It is a schematic diagram of the regulation parameters required for the directional growth of nano-gas sensitive materials in the micro-region at the wafer level in the present invention.

[0019] The present invention will be further explained below in conjunction with the drawings and embodiments. Specific embodiments

[0020] The specific embodiments of the present invention will be described in more detail below with reference to the drawings. Although specific embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0021] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different terms to refer to the same component. The specification and claims of the present invention do not use the difference in terms as a way to distinguish components, but use the difference in functions of components as the criterion for distinction. As used throughout the specification and claims, the terms "comprising" or "including" are open-ended terms and should be interpreted as "including but not limited to". The subsequent description of the specification is for the purpose of implementing the preferred embodiments of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the scope defined by the appended claims.

[0022] For the convenience of understanding the embodiments of the present invention, the following will further explain with specific embodiments as examples in conjunction with the drawings, and each drawing does not constitute a limitation to the embodiments of the present invention.

[0023] As Figures 1 to 5 shown, the method for the directional growth of In2O3 nano-materials includes the following steps: Step S1, preparing a silicon substrate with heating electrodes and test electrodes as the In2O3 growth carrier; Step S2, using trimethylindium as the indium gas source and oxygen as the oxygen source, and growing In2O3 nano-materials directionally under the micro-region thermal induction formed by chemical vapor deposition on the heating electrodes.

[0024] In a preferred embodiment of the method for the directional growth of In2O3 nano-materials described above, step S1 includes, Step S11, pre-treating the silicon substrate, and ultrasonically cleaning the silicon substrate in acetone and ethanol solutions in sequence; Step S12: Use the MEMS process to form at least one MEMS micro-hotplate on the silicon substrate as the growth carrier of In2O3. The MEMS micro-hotplate includes multiple groups of heating electrodes and test electrodes with the same structure.

[0025] In a preferred embodiment of the method for the directional growth of the In2O3 nanomaterial, step S2 includes: Step S21: Regulation of the double-temperature zone reaction furnace. Install the MEMS micro-hotplate in the reaction deposition zone of the double-temperature zone reaction furnace, close the reaction furnace chamber, and evacuate the pressure in the reaction furnace chamber to a predetermined pressure range. Step S22: Control of the growth parameters of the In2O3 nanomaterial. Adjust the flow rate of trimethylindium vapor so that it is carried by the carrier gas into the reaction chamber. At the same time, adjust the O2 flow rate. Connect the DC power supply to the positive and negative electrodes of the heating electrodes of the MEMS micro-hotplate. According to the resistance of the heating electrodes and the target heating temperature, adjust the current magnitude to heat up the heating electrodes and form a micro-thermal field on the silicon substrate. The trimethylindium vapor and oxygen undergo a chemical reaction in the high-temperature environment in the reaction deposition zone, and indium oxide nanomaterials are directionally grown in the heating area of the silicon substrate.

[0026] In a preferred embodiment of the method for the directional growth of the In2O3 nanomaterial, in step S11, the silicon substrate is sequentially placed in acetone and ethanol solutions and ultrasonically cleaned for 15 - 20 min to remove surface oil stains and organic impurities. In step S12, the materials of the heating electrodes and test electrodes deposited on the silicon substrate are Au, and the deposition thickness is between 100 - 400 nm. A Cr layer with a thickness of 10 - 100 nm is deposited between Au and the silicon substrate to increase the adhesion between the electrodes and the substrate. The core role of the Cr layer (10 - 100 nm) is to improve the adhesion between Au and Si through chemical bonding, and the role of the Au layer (100 - 400 nm) is to optimize electrical properties and enhance mechanical stability.

[0027] In a preferred embodiment of the method for the directional growth of the In2O3 nanomaterial, in step S12, the test electrodes are isolated from the heating electrodes by a dielectric layer and are within the microzone controlled by the temperature of the MEMS micro-hotplate.

[0028] In a preferred embodiment of the method for the directional growth of the In2O3 nanomaterial, in step S21, use a vacuum pump to evacuate the pressure in the chamber to a predetermined pressure range of 10 -1 - 10 -3 Pa. Controlling the chamber pressure within 10 -1 - 10 -3 Pa serves to regulate the gas-phase reaction rate and reduce impurity incorporation. In step S22, the growth time of the In2O3 thin film, the micro-region heating temperature on the silicon substrate, and the flow rates of trimethylindium vapor and O2 are controlled to directionally grow indium oxide nanomaterials.

[0029] In a preferred embodiment of the method for directionally growing In2O3 nanomaterials, the same temperature in each micro-region results in consistent In2O3 nanomaterials, or the temperature distribution and gradient change in each micro-region enable the directionally controllable growth of In2O3 nanomaterials in each micro-region.

[0030] Figure 4 The following is a schematic structural diagram of an In2O3 directional growth device based on MEMS technology and micro-region thermal field control provided by an example of the present invention. A directional growth device for implementing the method includes: A tube furnace 5, which is provided with a reaction chamber and an air inlet 4 communicating with the reaction chamber. The tube furnace is provided with a porcelain boat loaded with trimethylindium 6 for forming trimethylindium vapor. Trimethylindium can be regarded as an In2O3 precursor. A carrier gas source 1, which is provided with a carrier gas for transporting trimethylindium and is connected to the air inlet 4. An oxygen source 2, which is provided with oxygen and is connected to the air inlet 4. A flow controller 3, which is connected to the carrier gas source and the oxygen source to adjust the flow rates and their ratio of trimethylindium vapor and O2. A vacuum pump 12, which is connected to the reaction chamber to evacuate the air. A pressure gauge 11, which is connected to the reaction chamber to detect pressure data. A MEMS micro-heating plate 10, which is arranged in the reaction chamber and in the reaction gas 8 composed of trimethylindium vapor and O2. The MEMS micro-heating plate includes a heating electrode and a test electrode. A DC power supply device 9, which is connected to the heating electrode to heat and form a micro-region. A temperature control console 7, which is connected to the DC power supply device to adjust the micro-region temperature. Indium oxide nanomaterials are directionally grown in the micro-region of the MEMS micro-heating plate.

[0031] An In2O3 sensor is fabricated by the method described above.

[0032] An electronic nose includes the In2O3 sensor described above. In one embodiment, the mass flow controller controls the flow rates of trimethylindium vapor and O2, and the ratio between the two is between 5:1 and 40:1. The growth time of the In2O3 nanomaterials is 0.5 - 3 h, and the high-temperature environment is 300 - 600 °C.

[0033] In one embodiment, a wafer-level micro-hotplate is processed. A voltage is applied through the bonding pads on the wafer to achieve the temperature distribution and gradient change in the micro-regions of each micro-hotplate on the wafer. Under the action of the micro-region temperature distribution and gradient change, a reaction gas is introduced to achieve the directional and controllable growth of In2O3 nanomaterials in each micro-region. The structural characteristics and temperature fields of each micro-hotplate and micro-region are highly consistent, making the environments of each micro-region for the directional growth of In2O3 consistent, thereby achieving high consistency of the gas-sensitive materials in each micro-region on the wafer, and thus realizing the high-consistency processing of wafer-level sensors.

[0034] In one embodiment, each highly consistent MEMS micro-hotplate processed on the wafer is used as a thermal field control component. By taking the area where the heating electrode can provide temperature as the micro-region thermal field control, high-performance and highly consistent In2O3 nanomaterials are obtained through directional growth under the micro-region thermal induction of each micro-hotplate without a mask.

[0035] In one embodiment, a silicon substrate is prepared with many heating electrodes and test electrodes with consistent structural characteristics by using MEMS technology. The heating electrodes are the temperature control elements of the micro-hotplate. The test electrodes are isolated from the electrodes through a dielectric layer and are within the temperature control region of the micro-hotplate. The voltage-applied ends of all heating electrodes are connected together and share a bonding pad, while the grounds of the heating electrodes are connected together and share a bonding pad. The silicon substrate with heating electrodes and test electrodes prepared after cleaning and drying pretreatment is installed in the reaction deposition area of a two-temperature zone reaction furnace. The growth time of the In2O3 film, the micro-region heating temperature on the silicon substrate, and the precursor ratio parameters are controlled to grow highly consistent In2O3 materials in a specific area on the heating electrodes. The precursor ratio includes the flow ratio of trimethylindium vapor to O2.

[0036] In one embodiment, the method specifically includes the following steps: S1. Pretreatment of the silicon substrate: Select a silicon substrate and sequentially place it in acetone and ethanol solutions for ultrasonic cleaning for 15 - 20 minutes to remove surface oil and organic impurities; S2. Preparation of MEMS micro-hotplate: Use MEMS processes such as photolithography and thin film deposition to prepare heating and test electrodes, and release the silicon substrate to form a micro-hotplate composed of a large number of heating and test electrodes with consistent structural characteristics on the silicon substrate; S3. Regulation of the two-temperature zone reaction furnace: Install the pretreated silicon substrate in the reaction deposition area of the two-temperature zone reaction furnace, close the reaction furnace chamber, and start the vacuum system to pump the pressure in the chamber to a certain pressure range; S4. Growth parameter control of In2O3 nanomaterials: Adjust the flow rate of trimethylindium vapor through a mass flow controller so that it is carried by the carrier gas (N2) into the reaction chamber. At the same time, open the valve of the O2 supply device and adjust the O2 flow rate. Connect the DC power supply to the positive and negative electrodes of the heating electrode on the silicon substrate, and adjust the current magnitude according to the resistance of the heating electrode and the target heating temperature, so that the heating electrode part heats up and a local thermal field is formed on the silicon substrate. Trimethylindium vapor and oxygen undergo a chemical reaction in the high-temperature environment in the reaction deposition area, and indium oxide thin films are directionally grown in the heated area of the silicon substrate.

[0037] In one embodiment, the growth of In2O3 nanomaterials: Place trimethylindium powder in a porcelain boat and send it into the first temperature zone; place the silicon substrate in the tube furnace chamber and connect the heating electrode thereon to an external power supply; close the reaction furnace chamber and start the vacuum system to evacuate the reaction chamber; set the temperatures of each zone and use the carrier gas to carry trimethylindium gas and oxygen into the reaction chamber; trimethylindium vapor and oxygen undergo a chemical reaction, and In2O3 nanomaterials are deposited and formed in the heated area of the silicon substrate.

[0038] In one embodiment, all the heating electrode patterns are connected to a main bus through branch lines. When the DC power supply is connected, the current flows to each heating electrode, causing them to heat up simultaneously.

[0039] In one embodiment, the temperature of the precursor gasification zone is precisely set within the range suitable for trimethylindium gasification, generally 10 - 20 °C. The temperature range of the reaction deposition zone on the silicon substrate is set at 300 - 600 °C.

[0040] Example 1

[0041] The micro-region temperature on the silicon substrate is set within the range of 300 - 600 °C to prepare In2O3 nanomaterials.

[0042] S1. Use MEMS technology to fabricate heating electrodes and test electrodes with a width range of 10 - 200 μm, a thickness of 100 - 400 nm Au, and 10 - 100 nm Cr on a silicon wafer.

[0043] S2. Place the porcelain boat containing trimethylindium and the silicon substrate on the sample stage in the reaction deposition area, ensuring firm placement and accurate position. Evacuate the reaction chamber.

[0044] S3. Purge with N2, set the temperature of the trimethylindium vaporization zone to 15 °C. Adjust the trimethylindium vapor flow rate to 0.5 sccm, the oxygen flow rate to 50 sccm, and the carrier gas flow rate to 100 sccm. Apply an electric current to the heating electrode of the silicon substrate to bring the temperature of the heating area to the range of 300 - 600 °C. After the reaction continues for 0.5 h, stop the supply of indium source gas, purge, and cool down to obtain In2O3 nanomaterials with a specific orientation and complex morphology on the silicon wafer.

[0045] Example 2

[0046] The preparation of In2O3 nanomaterials with a growth time in the range of 0.5 - 3 h during the reaction is the same as that in Example 1. Select the optimal growth temperature in Example 1 and only change the growth time.

[0047] Example 3

[0048] The preparation of In2O3 nanomaterials with a ratio of trimethylindium gas to O2 flow rate between 5:1 and 40:1 during the reaction is the same as that in Example 1. Select the optimal growth temperature and time in Examples 1 and 2 and only change the ratio of trimethylindium gas to O2 flow rate.

[0049] Use a characterization instrument to observe the oriented growth of In2O3 nanomaterials in the heating area. Use a high-precision digital multimeter or four-probe tester to measure the resistance of micro-nano sensors at different positions on the wafer.

[0050] Figure 1 The process flow chart of the micro-hotplate provided by the examples of the present invention includes silicon wafer preparation, insulating layer preparation, front-side lithography of heating electrode and test electrode patterns, electron beam evaporation of Cr&Au, stripping, and heat treatment. The corresponding position where the heating electrode provides temperature is the micro-region where In2O3 nanomaterials grow directionally in the present invention.

[0051] Figures 2(a) to 2(b) are schematic diagrams of the front-side test and heating pattern layouts of the MEMS micro-hotplate provided by the examples of the present invention. The designed heating electrodes can obtain a more uniform temperature field and lower power consumption. The MEMS micro-hotplate includes, Silicon substrate 13, SiO2 support layer 14, which is laminated on the silicon substrate 13, Si3N4 support layer 15, which is laminated on the SiO2 support layer 14, Heating electrode 16, which is deposited on the Si3N4 support layer 15, Test electrode 17, which is deposited on the Si3N4 support layer 15 and is isolated from the heating electrode 16 through a dielectric layer.

[0052] Figure 3Schematic diagram of the circuit connection method between local micro-heating plates on a wafer provided for an example of the present invention. Taking a 2×5 micro-heating plate array as an example, a bus-type connection method is adopted. A main bus is set, and each heating electrode is connected to the main bus through a branch line. By reasonably designing the electrical conductivity and power-carrying capacity of the bus, simultaneous power supply and heating of numerous electrodes are achieved, and the temperature is ensured to be consistent at each micro-region.

[0053] Figure 5 Schematic diagram of the regulation parameters (growth temperature, growth time, gas ratio) required for the directional growth of nano gas-sensitive materials in a micro-region at the wafer level of the present invention. The present invention proposes a brand-new method for the directional growth of high-performance nano gas-sensitive materials in a large area of micro-regions. Micro-scale heating electrodes with specific patterns and sizes are fabricated using MEMS technology. By applying different voltages to the heating electrodes, the magnitude of the adjusted voltage can control the temperature of the micro-region thermal field generated by the heating electrodes. The ratio of trimethylindium vapor flow to O2 flow is adjusted through a mass flow controller, and the growth time is simultaneously regulated to achieve the controllable growth of the position and morphology of In2O3 nano materials.

[0054] In the present invention, the silicon substrate is ultrasonically cleaned in acetone and ethanol for 15 - 20 min in sequence to remove oil stains, organic substances, and particulate impurities on the silicon surface; improve the adhesion between the subsequent metal deposition layer (Cr / Au) and the substrate; Ensure the lithography accuracy during the patterning process of MEMS electrodes; reduce defects or heterogeneous nucleation caused by contamination during the growth of In2O3. Cr / Au electrodes are fabricated on the Si substrate using MEMS processes such as lithography, electron beam evaporation, and lift-off. Cr serves as an adhesion layer to enhance the bonding force between Au and the Si surface and prevent the electrode from falling off; Au has good electrical conductivity and thermal stability and is suitable as a heating element; it can achieve micron-scale electrode patterning to form a micro-region temperature control structure; the test electrodes are isolated by a dielectric layer to avoid current interference and ensure measurement accuracy; it supports wafer-level batch processing, improving the consistency and efficiency of sensor manufacturing. The chamber pressure is pumped to 10 -1 - 10 -3Pa, and set the temperatures of the precursor gasification zone and the deposition zone respectively. Control the gasification rate of trimethylindium and the carrier gas carrying efficiency; reduce the background gas concentration and impurity doping; achieve precise temperature zoning to ensure that In2O3 grows only in the target area; provide a stable chemical vapor deposition environment. Using trimethylindium as the In source and oxygen as the O source, a CVD reaction occurs in the microzone induced by the heating electrode. Utilize the local high temperature in the microzone to control the nucleation and growth direction; achieve the selective deposition of In2O3 in specific microzones; control the material morphology and crystallization quality by adjusting the precursor ratio and growth time; realize the growth of complex patterned nanostructures without a mask. The heating electrode and the test electrode are isolated structures, and a dielectric layer is provided between the heating electrode and the test electrode. Prevent the heating current from interfering with the test signal; allow simultaneous heating and in-situ electrical detection in the same microzone; improve the stability and reliability of the device operation; support the large-scale integration of multi-electrode arrays. The bus-type heating electrode connection method, all heating electrodes are connected to the main bus through branch lines and powered by a common power supply. Realize the simultaneous heating of multiple microzones; reduce the wiring complexity and improve the wafer utilization rate; Ensure the temperature consistency of each microzone; easy to expand to a larger array or a higher density sensor layout.

[0055] Generate a local high-temperature microzone through the heating electrode to guide the selective deposition of In2O3. Do not rely on traditional lithography masks, significantly simplify the process flow; achieve the controllable growth of nanomaterials in the microzone; support the design of complex geometries such as interdigitated and mesh-like; improve the consistency and repeatability of wafer-level devices. Arrange multiple MEMS microhotplates with consistent structures on the whole wafer and supply power for heating uniformly. Realize the synchronous growth of high-performance gas-sensitive materials at the wafer level; greatly improve the batch production efficiency and yield of sensors; support the large-scale and low-cost manufacturing of gas-sensitive chips; suitable for the large-scale application of future flexible and intelligent sensing systems.

[0056] Due to its high specific surface area, abundant oxygen vacancies, and excellent conductivity modulation ability, In2O3 nanomaterials can efficiently detect gases such as NO2, CO, and H2S; the microzone temperature control structure supports the dynamic adjustment of the operating temperature, improving the gas recognition ability and sensitivity. Based on In2O3 materials grown at multiple different microzone temperatures, a sensor array is formed; the different response modes of each sensor can be used for fingerprint-like odor analysis; applied to fields such as food safety, medical diagnosis, and environmental monitoring, by combining MEMS microhotplate technology with chemical vapor deposition (CVD), the directional growth of In2O3 nanomaterials with microzone positioning, controllable morphology, and wafer-level consistency is realized.

[0057] Although the embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields. The above specific embodiments are merely illustrative and guiding, rather than restrictive. Those of ordinary skill in the art can also make many forms under the inspiration of this specification and without departing from the scope protected by the claims of the present invention, and all of these are within the scope of protection of the present invention.

Claims

1. A method for the directional growth of In2O3 nanomaterials, characterized in that It includes the following steps: Step S1, preparing a silicon substrate with heating electrodes and test electrodes as the growth carrier of In2O3; Step S2, using trimethylindium as the indium gas source and oxygen as the oxygen source, and growing In2O3 nanomaterials directionally under the micro-region thermal induction formed by the heating electrodes through chemical vapor deposition.

2. The method for the directional growth of an In2O3 nanomaterial according to claim 1, characterized in that, Step S1 includes, Step S11, pre-treating the silicon substrate, and ultrasonically cleaning the silicon substrate in acetone and ethanol solutions in sequence; Step S12, forming at least one MEMS micro-hotplate on the silicon substrate by using MEMS technology as the growth carrier of In2O3, and the MEMS micro-hotplate includes multiple groups of heating electrodes and test electrodes with the same structure.

3. The directional growth method of an In2O3 nanomaterial according to claim 2, wherein Step S2 includes, Step S21, regulating the double-temperature zone reaction furnace, installing the MEMS micro-hotplate in the reaction deposition zone of the double-temperature zone reaction furnace, closing the reaction furnace chamber, and evacuating the pressure in the reaction furnace chamber to a predetermined pressure range; Step S22, controlling the growth parameters of In2O3 nanomaterials, adjusting the trimethylindium vapor flow rate to make it enter the reaction furnace chamber carried by the carrier gas, and at the same time adjusting the O2 flow rate, connecting the DC power supply to the positive and negative electrodes of the heating electrodes of the MEMS micro-hotplate, and adjusting the current magnitude according to the heating electrode resistance and the target heating temperature to heat up the heating electrodes, forming a micro-region thermal field on the silicon substrate, and the trimethylindium vapor and oxygen undergo a chemical reaction in the high-temperature environment in the reaction deposition zone, and indium oxide nanomaterials grow directionally in the heating area of the silicon substrate.

4. The method for the directional growth of an In2O3 nanomaterial according to claim 2, characterized in that, In Step S11, the silicon substrate is ultrasonically cleaned in acetone and ethanol solutions in sequence for 15 - 20 min to remove surface oil stains and organic impurities, In Step S12, the materials of the heating electrodes and test electrodes deposited on the silicon substrate are Au, and the deposition thickness is between 100 - 400 nm, and a layer of Cr with a thickness of 10 - 100 nm is deposited between Au and the silicon substrate to increase the adhesion between the electrodes and the substrate.

5. The method for the directional growth of an In2O3 nanomaterial according to claim 2, wherein In Step S12, the test electrodes are isolated from the heating electrodes through a dielectric layer and are within the micro-region controlled by the temperature of the MEMS micro-hotplate.

6. The method for the directional growth of an In2O3 nanomaterial according to claim 3, characterized in that, In step S21, the pressure in the chamber is pumped to a predetermined pressure range of 10 -1 - 10 -3 Pa by using a vacuum pump; In Step S22, controlling the growth time of the In2O3 thin film, the micro-region heating temperature on the silicon substrate, and the trimethylindium vapor and O2 flow rates to grow indium oxide nanomaterials directionally.

7. A method for the directional growth of an In2O3 nanomaterial according to claim 1, characterized in that, The same temperature in each micro-region results in consistent In2O3 nanomaterials, or the temperature distribution and gradient change in each micro-region realize the directionally controllable growth of In2O3 nanomaterials in each micro-region.

8. An oriented growth device for implementing the method according to any one of claims 1-7, characterized in that, It includes, A tube furnace, which is provided with a reaction furnace chamber and an air inlet communicating with the reaction furnace chamber, and the tube furnace is provided with a porcelain boat for loading trimethylindium to form trimethylindium vapor, A carrier gas source, which is provided with a carrier gas for transporting trimethylindium and is connected to the air inlet, An oxygen source, which is provided with oxygen and is connected to the air inlet, A flow controller, which is connected to the carrier gas source and the oxygen source to adjust the trimethylindium vapor and O2 flow rates and their ratios; A vacuum pump, which is connected to the reaction furnace chamber to evacuate; A pressure gauge, which is connected to the reaction furnace chamber to detect pressure data, A MEMS microhotplate is disposed in the reaction furnace chamber and in a reaction gas composed of trimethylindium vapor and O2. The MEMS microhotplate includes a heating electrode and a test electrode; A DC power supply device is connected to the heating electrode to heat and form a microzone. A temperature control console is connected to the DC power supply device to adjust the temperature of the microzone, and indium oxide nanomaterials are directionally grown in the microzone of the MEMS microhotplate.

9. An In2O3 sensor, characterized in that, It is made by the method according to any one of claims 1-7.

10. An electronic nose, characterized in that, It includes the In2O3 sensor according to claim 9.

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