In2o3 nanomaterial directional growth method and device, sensor and electronic nose

Abstract

The application discloses a method and device for directional growth of In2O3 nano material, a sensor and an electronic nose. In the method, a silicon substrate with a heating electrode and a testing electrode is prepared as an In2O3 growth carrier; trimethyl indium is used as an indium gas source, and oxygen is used as an oxygen source; and the In2O3 nano material is directionally grown under the micro-zone heat induction formed by the heating electrode through chemical vapor deposition. The method realizes the high consistency of the gas-sensitive material in each micro-zone on a wafer, thereby realizing the high-consistency processing of the wafer-level sensor.

Description

Technical Field

[0001] This invention relates to the field of semiconductor metal oxide functional materials technology, and in particular to a method, apparatus, sensor and electronic nose for the directional growth of In2O3 nanomaterials. Background Technology

[0002] Asthma, a common chronic respiratory disease, seriously affects the health of hundreds of millions of people worldwide. Today, early diagnosis and precision treatment are crucial for controlling asthma progression and improving patients' quality of life. Breath testing, as a non-invasive detection technology, has become a hot research area in asthma detection in recent years due to its convenient and real-time acquisition of physiological and pathological information. Studies have found that the exhaled breath of asthma patients contains various specific biomarkers, such as volatile organic compounds like nitric oxide. By detecting changes in the concentration of these biomarkers, early non-invasive diagnosis of asthma is expected. Electronic noses, as key devices in breath testing, can fully leverage their advantages by improving the consistency of the normalized key performance requirements of various components in their internal sensor array, ensuring the accuracy and reliability of test results meet clinical needs. Therefore, developing high-performance and highly consistent sensors is crucial for improving the performance of electronic noses and overcoming the bottlenecks in asthma breath testing technology.

[0003] Metal-oxide-semiconductor (MOS) nanomaterials, with their unique size, surface, and quantum size effects, have shown great application potential in the field of gas sensing. In₂O₃, as an important member of the MOS nanomaterial family, possesses advantages such as a wide bandgap, good electrical properties, and chemical stability, making it outstanding in gas sensing, particularly suitable for detecting specific VOCs in asthma exhalation. However, current technologies face the challenge of simultaneously achieving high sensitivity, high stability, and device consistency in micro / nano gas sensors.

[0004] The information disclosed in the background section is only for enhancing the understanding of the background of this invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] This invention provides a method, apparatus, sensor, and electronic nose for the directional growth of In2O3 nanomaterials. The In2O3 nanomaterials are prepared using large-area wafer fabrication processes. The highly consistent directional growth of In2O3 nanomaterials solves the technical problem of simultaneously achieving high performance and high consistency in the fabrication of large-area nanomaterial gas sensors. It enables wafer-level integration of micrometer-scale structures and nanomaterial gas sensors, thus resolving the manufacturing challenge of achieving high sensitivity, high stability, and device consistency in micro / nano gas sensors. The uniform and controllable growth of nanomaterials within a defined micrometer-scale region on the entire wafer ensures that each sensor chip possesses highly consistent micro / nano-scale structural characteristics, including optimized crystal structure, directional guidance of growth orientation, and precise control of size and morphology. This provides strong technical support for the detection and analysis of trace complex gases using electronic noses.

[0006] A method for directional growth of In2O3 nanomaterials includes:

[0007] Step S1: Prepare a silicon substrate with heating electrode and test electrode as an In2O3 growth support.

[0008] In step S2, using trimethylindium as the indium gas source and oxygen as the oxygen source, In2O3 nanomaterials are directionally grown by chemical vapor deposition in a micro-region formed by a heated electrode under thermal induction.

[0009] In the directional growth method of In2O3 nanomaterials, step S1 includes,

[0010] Step S11, silicon substrate pretreatment, the silicon substrate is placed in acetone and ethanol solutions in sequence for ultrasonic cleaning;

[0011] Step S12: At least one MEMS hot plate is formed on a silicon substrate using MEMS technology as an In2O3 growth carrier. The MEMS hot plate includes multiple sets of heating electrodes and test electrodes with consistent structure.

[0012] In the directional growth method of In2O3 nanomaterials, step S2 includes,

[0013] Step S21, control of the dual-temperature zone reactor: install the MEMS micro hot plate in the reaction deposition zone of the dual-temperature zone reactor, close the reactor chamber, and evacuate to bring the pressure inside the reactor chamber to a predetermined pressure range.

[0014] Step S22: Controlling the growth parameters of In2O3 nanomaterials. Adjusting the flow rate of trimethylindium vapor to allow it to be carried into the reaction chamber by the carrier gas. Simultaneously, adjusting the O2 flow rate. Connecting a DC power supply to the positive and negative terminals of the heating electrode of the MEMS micro-hot plate. Adjusting the current based on the resistance of the heating electrode and the target heating temperature to raise the temperature of the heating electrode and form a micro-thermal field on the silicon substrate. Trimethylindium vapor and oxygen undergo a chemical reaction in the high-temperature environment within the reaction deposition zone, resulting in the directional growth of indium oxide nanomaterials in the heated area of ​​the silicon substrate.

[0015] In the directional growth method of In2O3 nanomaterials, in step S11, the silicon substrate is sequentially immersed in acetone and ethanol solutions for ultrasonic cleaning for 15-20 minutes to remove surface oil and organic impurities.

[0016] In step S12, Au is deposited on the silicon substrate as the material for the heating electrode and the test electrode. 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.

[0017] In the directional growth method of In2O3 nanomaterials, in step S12, the test electrode is isolated from the heating electrode through a dielectric layer and is located within the temperature-controlled micro-region of the MEMS micro-hot plate.

[0018] In the directional growth method of In2O3 nanomaterials, in step S21, the pressure in the chamber is evacuated to 10 using a vacuum pump. -1 - 10 -3 The predetermined pressure range of Pa;

[0019] In step S22, the growth time of the In2O3 thin film, the micro-area heating temperature on the silicon substrate, and the flow rate of trimethylindium vapor and O2 are controlled to directionally grow indium oxide nanomaterials.

[0020] In the directional growth method of In2O3 nanomaterials, the temperature of each microregion is the same to obtain consistent In2O3 nanomaterials, or the temperature distribution and gradient change of each microregion realize the directional and controllable growth of In2O3 nanomaterials in each microregion.

[0021] An directional growth apparatus for implementing the method includes,

[0022] A tubular furnace, which includes a reaction chamber and an inlet connecting to the reaction chamber, and a ceramic boat loaded with trimethylindium to form trimethylindium vapor.

[0023] A carrier gas source, which contains a carrier gas for transporting trimethylindium, is connected to the air inlet.

[0024] An oxygen source, containing oxygen, is connected to the air inlet.

[0025] A flow controller that connects to a carrier gas source and an oxygen source to regulate the flow rate and ratio of trimethylindium vapor and O2;

[0026] A vacuum pump, which is connected to the reaction chamber to create a vacuum;

[0027] A pressure gauge, connected to the reaction chamber, is used to detect pressure data.

[0028] MEMS micro hot plate, which is located in the reaction chamber and in the reaction gas composed of trimethylindium vapor and O2, the MEMS micro hot plate includes heating electrode and test electrode;

[0029] A DC power supply device is connected to the heating electrode to heat and form the micro-region.

[0030] A temperature control console, connected to a DC power supply, is used to regulate the temperature of the micro-area. The MEMS micro-hot plate features micro-area directional growth of indium oxide nanomaterials.

[0031] An In2O3 sensor, which is made by the method described above.

[0032] An electronic nose comprising the aforementioned In2O3 sensor.

[0033] Compared with existing technologies, this invention has the following advantages: Precise growth position control: By fabricating heating electrodes on a silicon substrate using MEMS technology and connecting to an external power supply, local thermal field control can be achieved on the silicon substrate, precisely defining the In2O3 growth area and meeting the stringent requirements for material growth position in different application scenarios. High-quality material growth: The independently controllable temperature environment of the dual-temperature zone reactor allows for optimization of the indium source gas to O2 ratio, growth temperature, and time conditions, effectively improving the crystallinity, surface smoothness, and electrical performance consistency of the indium oxide thin film, making it more suitable for high-performance semiconductor devices and sensors. Good repeatability and stability: The MEMS process and precise control parameters of each device used in this invention ensure good repeatability and stability of the entire In2O3 growth process. In experiments across different batches, highly consistent In2O3 materials with similar performance were prepared. Using micro-region thermal field induction technology, high-performance In2O3 sensors with good consistency within the same batch were prepared. This is expected to significantly improve the consistency among sensors in electronic noses, providing strong technical support for accurately detecting biomarkers in asthma exhalation, improving the accuracy and reliability of asthma diagnosis, and promoting asthma exhalation detection technology to a new stage of development. Attached Figure Description

[0034] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0035] In the attached diagram:

[0036] Figure 1 This is the fabrication process flow of the MEMS micro hot plate in this invention;

[0037] Figures 2(a) to 2(b) are schematic diagrams of the front testing and heating pattern layout on the MEMS micro-hot plate in this invention;

[0038] Figure 3 This is a schematic diagram of the circuit connection between the local micro-hot plates removed from the wafer in this invention;

[0039] Figure 4 This is a schematic diagram of the In2O3 directional growth device based on MEMS technology and micro-area thermal field control in this invention.

[0040] Figure 5 This is a schematic diagram of the control parameters required for the directional growth of nano-gas-sensitive materials in a wafer-level micro-region in this invention.

[0041] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0042] Specific embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While specific embodiments of the invention are shown in the drawings, it should be understood that the invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0043] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0044] To facilitate understanding of the embodiments of the present invention, further explanations and descriptions will be provided below with reference to the accompanying drawings and specific embodiments. The accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0045] like Figures 1 to 5 As shown, the directional growth method of In2O3 nanomaterials includes the following steps:

[0046] Step S1: Prepare a silicon substrate with heating electrode and test electrode as an In2O3 growth support.

[0047] In step S2, using trimethylindium as the indium gas source and oxygen as the oxygen source, In2O3 nanomaterials are directionally grown by chemical vapor deposition in a micro-region formed by a heated electrode under thermal induction.

[0048] In a preferred embodiment of the method for directional growth of In2O3 nanomaterials, step S1 includes,

[0049] Step S11, silicon substrate pretreatment, the silicon substrate is placed in acetone and ethanol solutions in sequence for ultrasonic cleaning;

[0050] Step S12: At least one MEMS hot plate is formed on a silicon substrate using MEMS technology as an In2O3 growth carrier. The MEMS hot plate includes multiple sets of heating electrodes and test electrodes with consistent structure.

[0051] In a preferred embodiment of the method for directional growth of In2O3 nanomaterials, step S2 includes,

[0052] Step S21, control of the dual-temperature zone reactor: install the MEMS micro-hot plate in the reaction deposition zone of the dual-temperature zone reactor, close the reactor chamber, and evacuate to bring the pressure inside the reactor chamber to a predetermined pressure range.

[0053] Step S22: Controlling the growth parameters of In2O3 nanomaterials. Adjusting the flow rate of trimethylindium vapor to allow it to be carried into the reaction chamber by the carrier gas. Simultaneously, adjusting the O2 flow rate. Connecting a DC power supply to the positive and negative terminals of the heating electrode of the MEMS micro-hot plate. Adjusting the current based on the resistance of the heating electrode and the target heating temperature to raise the temperature of the heating electrode and form a micro-thermal field on the silicon substrate. Trimethylindium vapor and oxygen undergo a chemical reaction in the high-temperature environment within the reaction deposition zone, resulting in the directional growth of indium oxide nanomaterials in the heated area of ​​the silicon substrate.

[0054] In a preferred embodiment of the method for directional growth of In2O3 nanomaterials, in step S11, the silicon substrate is sequentially immersed in acetone and ethanol solutions for ultrasonic cleaning for 15-20 minutes to remove surface oil and organic impurities.

[0055] In step S12, Au is deposited on the silicon substrate as the material for the heating electrode and the test electrode. 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 electrode and the substrate. The core function of the Cr layer (10-100 nm) is to improve the adhesion between Au and Si through chemical bonding. The role of the Au layer (100-400 nm) is to optimize electrical performance and improve mechanical stability.

[0056] In a preferred embodiment of the directional growth method for In2O3 nanomaterials, in step S12, the test electrode is isolated from the heating electrode by a dielectric layer and is located within a temperature-controlled micro-region of the MEMS micro-hot plate.

[0057] In a preferred embodiment of the method for directional growth of In2O3 nanomaterials, in step S21, a vacuum pump is used to evacuate the pressure inside the chamber to 10. -1 - 10 -3 The predetermined pressure range of Pa will control the chamber pressure at 10 Pa. -1 - 10 -3 The role of Pa- is to regulate the gas-phase reaction rate and reduce the incorporation of impurities;

[0058] In step S22, the growth time of the In2O3 thin film, the micro-area heating temperature on the silicon substrate, and the flow rate of trimethylindium vapor and O2 are controlled to directionally grow indium oxide nanomaterials.

[0059] In a preferred embodiment of the method for directional growth of In2O3 nanomaterials, the temperature of each microregion is the same to obtain consistent In2O3 nanomaterials, or the temperature distribution and gradient change of each microregion achieves directional and controllable growth of In2O3 nanomaterials in each microregion.

[0060] Figure 4A schematic diagram of an In2O3 directional growth device based on MEMS technology and micro-area thermal field control is provided as an example of the present invention. One embodiment of the directional growth device includes...

[0061] The tubular furnace 5 has a reaction chamber and an air inlet 4 connected to the reaction chamber. The tubular furnace is equipped with a ceramic boat loaded with trimethylindium 6 to form trimethylindium vapor. Trimethylindium can be regarded as an In2O3 precursor.

[0062] Carrier gas source 1, which contains a carrier gas for transporting trimethylindium, is connected to the air inlet 4.

[0063] Oxygen source 2, which contains oxygen, is connected to the air inlet 4.

[0064] Flow controller 3 is connected to a carrier gas source and an oxygen source to regulate the flow rate and ratio of trimethylindium vapor and O2.

[0065] A vacuum pump 12 is connected to the reaction chamber to create a vacuum.

[0066] Pressure gauge 11, which is connected to the reaction chamber to detect pressure data,

[0067] MEMS micro hot plate 10 is disposed in the reaction chamber and in the reaction gas 8 composed of trimethylindium vapor and O2. The MEMS micro hot plate includes heating electrodes and test electrodes.

[0068] DC power supply device 9, which is connected to the heating electrode to heat and form the micro-region,

[0069] Temperature control console 7, which is connected to a DC power supply to regulate the micro-area temperature, is used for the micro-area directional growth of indium oxide nanomaterials in the MEMS micro-hot plate.

[0070] An In2O3 sensor, which is made by the method described above.

[0071] An electronic nose comprising the aforementioned In2O3 sensor

[0072] In one embodiment, the flow rates of trimethylindium vapor and O2 are controlled by a mass flow controller, with a ratio between 5:1 and 40:1. The growth time of the In2O3 nanomaterial is 0.5-3 hours, and the high-temperature environment is 300-600°C.

[0073] In one embodiment, wafer-level micro-hotplates are fabricated. Voltage is applied to the bonding pads on the wafer to achieve temperature distribution and gradient changes within micro-regions on each micro-hotplate. Under the influence of these temperature distribution and gradient changes, a reactive gas is introduced to achieve the directional and controllable growth of In₂O₃ nanomaterials within each micro-region. The structural characteristics and temperature fields of each micro-hotplate and micro-region remain highly consistent, ensuring a uniform environment for the directional growth of In₂O₃ within each micro-region. This results in a high degree of consistency in the gas-sensitive material within each micro-region on the wafer, thereby achieving highly consistent wafer-level sensor fabrication.

[0074] In one embodiment, highly consistent MEMS micro-hotplates fabricated on a wafer are used as thermal field control components. By controlling the field of the area where the heating electrode can provide temperature as a micro-region heat field, high-performance, highly consistent In2O3 nanomaterials can be obtained by directional growth under the micro-region thermal induction of each micro-hotplate without a mask template.

[0075] In one embodiment, a plurality of heating electrodes and test electrodes with identical structural features are fabricated on a silicon substrate using MEMS technology. The heating electrodes are micro-hotplate temperature control elements, and the test electrodes are isolated from the electrodes by a dielectric layer and are located within the temperature control region of the micro-hotplate. The voltages of all heating electrodes are connected together and share a common bonding pad, while the grounds of the heating electrodes are also connected together and share a common bonding pad. The silicon substrate with the heating and test electrodes, after being pretreated by cleaning and drying, is installed in the reaction deposition zone of a dual-temperature zone reactor. The growth time of the In2O3 thin film, the micro-area heating temperature on the silicon substrate, and the precursor ratio parameters are controlled to grow highly consistent In2O3 material in specific areas on the heating electrodes. The precursor ratio includes the ratio of trimethylindium vapor to O2 flow rate.

[0076] In one embodiment, the method specifically includes the following steps:

[0077] S1. Silicon substrate pretreatment: Select a silicon substrate and immerse it in acetone and ethanol solutions for ultrasonic cleaning for 15-20 minutes to remove surface oil and organic impurities;

[0078] S2. MEMS micro hot plate fabrication: Heating and testing electrodes are fabricated using MEMS processes such as photolithography and thin film deposition, and the silicon substrate is released to form a large number of micro hot plates composed of heating and testing electrodes with consistent structural features on the silicon substrate;

[0079] S3. Control of the dual-temperature zone reactor: Install the pretreated silicon substrate in the reaction deposition zone of the dual-temperature zone reactor, close the reactor chamber, and start the vacuum system to pump the pressure inside the chamber to a certain pressure range;

[0080] S4. In2O3 Nanomaterial Growth Parameter Control: The flow rate of trimethylindium vapor is adjusted using a mass flow controller, allowing it to be carried into the reaction chamber by a carrier gas (N2). Simultaneously, the O2 supply valve is opened, and the O2 flow rate is adjusted. A DC power supply is connected to the positive and negative terminals of the heating electrode on the silicon substrate. The current is adjusted according to the resistance of the heating electrode and the target heating temperature to partially heat the heating electrode, forming a localized thermal field on the silicon substrate. Trimethylindium vapor reacts chemically with oxygen in the high-temperature environment of the reaction deposition zone, resulting in the directional growth of an indium oxide thin film in the heated area of ​​the silicon substrate.

[0081] In one embodiment, In2O3 nanomaterial growth involves: placing trimethylindium powder into a ceramic boat and introducing it into a first temperature zone; placing a silicon substrate into a tubular furnace chamber and connecting its heating electrodes to an external power source; closing the reactor chamber and activating the vacuum system to evacuate the reaction chamber; setting the temperature of each zone and using a carrier gas to carry trimethylindium gas and oxygen into the reaction chamber; and reacting the trimethylindium vapor with oxygen to deposit In2O3 nanomaterials in the heated region of the silicon substrate.

[0082] In one embodiment, all heating electrode patterns are connected to a main bus via branch lines. When a DC power supply is connected, current flows to each heating electrode, causing them to heat up simultaneously.

[0083] In one embodiment, the temperature of the precursor vaporization zone is precisely set within a range suitable for the vaporization of trimethylindium, typically 10-20°C. The temperature range of the reaction deposition zone on the silicon substrate is set between 300-600°C.

[0084] Example 1

[0085] In₂O₃ nanomaterials were prepared by setting the temperature of the micro-regions on a silicon substrate in the range of 300-600 °C.

[0086] S1. Using MEMS technology, heating and testing electrodes with widths ranging from 10-200 μm and thicknesses of 100-400 nm Au and 10-100 nm Cr are fabricated on silicon wafers.

[0087] S2. Place the ceramic boat containing trimethylindium and the silicon substrate on the sample stage of the reaction deposition area, ensuring that they are firmly placed and accurately positioned. Evacuate the reaction chamber.

[0088] S3. Purge with N2 and set the temperature of the trimethylindium vaporization zone to 15℃. 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 current to the heating electrode of the silicon substrate to raise the temperature of the heating zone to the range of 300-600℃. After the reaction continues for 0.5 h, stop the indium source gas supply, purge, and cool down to obtain In2O3 nanomaterials with oriented positions and complex morphology on the silicon wafer.

[0089] Example 2

[0090] The preparation of In₂O₃ nanomaterials with a growth time ranging from 0.5 to 3 hours was the same as in Example 1. The optimal growth temperature from Example 1 was selected, and only the growth time was varied.

[0091] Example 3

[0092] The preparation of In₂O₃ nanomaterials with a trimethylindium gas to O₂ flow ratio between 5:1 and 40:1 was the same as in Example 1. The optimal growth temperature and time from Examples 1 and 2 were selected, and only the trimethylindium gas to O₂ flow ratio was changed.

[0093] The directional growth of In2O3 nanomaterials in the heated region was observed using characterization instruments. Resistance measurements of micro / nano sensors at different locations on the wafer were performed using a high-precision digital multimeter or a four-probe tester.

[0094] Figure 1 The flowchart illustrating the fabrication process of the micro hot plate provided in this invention includes silicon wafer preparation, insulating layer preparation, front-side etching of heating and testing electrode patterns, electron beam evaporation of Cr and Au, lift-off, and heat treatment. The heating electrode provides the temperature at a location corresponding to the micro-region where the In2O3 nanomaterial is directionally grown in this invention.

[0095] Figures 2(a) and 2(b) are schematic diagrams of the front testing and heating pattern layout of the MEMS micro-hotplate provided in this invention. The heating electrodes designed in this invention can achieve a more uniform temperature field and lower power consumption. The MEMS micro-hotplate includes...

[0096] Silicon substrate 13,

[0097] The SiO2 support layer 14 is stacked on the silicon substrate 13.

[0098] The Si3N4 support layer 15 is stacked on top of the SiO2 support layer 14.

[0099] Heating electrode 16, which is deposited on the Si3N4 support layer 15,

[0100] Test electrode 17 is deposited on the Si3N4 support layer 15 and isolated from the heating electrode 16 via a dielectric layer.

[0101] Figure 3 This is a schematic diagram illustrating the circuit connection method between localized micro-hotplates on a wafer, provided as an example of the present invention. Taking a 2×5 micro-hotplate array as an example, a bus-type connection method is adopted, with a main bus set up, and each heating electrode connected to the main bus through branch lines. By reasonably designing the conductivity and power carrying capacity of the bus, simultaneous power supply and heating of numerous electrodes can be achieved, while ensuring a consistent temperature in each micro-area.

[0102] Figure 5 This diagram illustrates the controllable parameters (growth temperature, growth time, gas ratio) required for the directional growth of nano-gas-sensitive materials in a wafer-level micro-region, as provided in this invention. This invention proposes a novel method for the directional growth of high-performance nano-gas-sensitive materials in a large-area micro-region. Microscale heating electrodes with specific patterns and sizes are fabricated using MEMS technology. By applying different voltages to the heating electrodes, the temperature of the micro-region thermal field generated by the heating electrodes can be controlled. The ratio of trimethylindium vapor flow to O2 flow is adjusted using a mass flow controller, and the growth time is simultaneously controlled, enabling controllable growth of the position and morphology of In2O3 nanomaterials.

[0103] This invention involves ultrasonically cleaning a silicon substrate sequentially in acetone and ethanol for 15-20 minutes to remove oil, organic matter, and particulate impurities from the silicon surface, thereby improving the adhesion between the subsequent metal deposition layer (Cr / Au) and the substrate.

[0104] To ensure photolithographic precision during MEMS electrode patterning and reduce defects or heterogeneous nucleation caused by contamination during In2O3 growth, Cr / Au electrodes are fabricated on a Si substrate using MEMS processes such as photolithography, electron beam evaporation, and lift-off. Cr acts as an adhesion layer, enhancing the bond between Au and the Si surface and preventing electrode detachment. Au possesses excellent conductivity and thermal stability, making it suitable as a heating element. Micrometer-level electrode patterning can be achieved, forming a micro-area temperature-controlled structure. The test electrodes are isolated by a dielectric layer to avoid current interference and ensure measurement accuracy. This supports wafer-level batch processing, improving the consistency and efficiency of sensor manufacturing. A vacuum pump is used to evacuate the chamber pressure to 10... -1 - 10 -3The temperature of the precursor vaporization zone and deposition zone is set separately. The vaporization rate and carrier gas carrying efficiency of trimethylindium are controlled; the background gas concentration is reduced to decrease impurity doping; precise temperature zoning is achieved to ensure that In₂O₃ grows only in the target region; and a stable chemical vapor deposition environment is provided. Using trimethylindium as the In source and oxygen as the O source, a CVD reaction occurs in a micro-region induced by a heating electrode. The nucleation and growth direction are controlled by the local high temperature of the micro-region; selective deposition of In₂O₃ in specific micro-regions is achieved; the morphology and crystal quality of the material are controlled by adjusting the precursor ratio and growth time; and the growth of complex patterned nanostructures can be achieved without a mask. An isolation structure is used between the heating electrode and the test electrode, with a dielectric layer between them. This prevents the heating current from interfering with the test signal; allows simultaneous heating and in-situ electrical detection within the same micro-region; improves the stability and reliability of the device; and supports large-scale integration of multi-electrode arrays. A bus-type heating electrode connection method is used, with all heating electrodes connected to the main bus via branch lines and sharing a power supply. Simultaneous heating of multiple micro-regions is achieved; wiring complexity is reduced and wafer utilization is improved;

[0105] Ensures temperature consistency across all micro-regions; easily expandable to larger arrays or higher density sensor layouts.

[0106] By generating localized high-temperature micro-regions through heated electrodes, selective deposition of In2O3 is guided. This significantly simplifies the process flow by eliminating reliance on traditional photolithography masks; enables controllable growth of nanomaterials within the micro-regions; supports complex geometries such as interdigitated and mesh-like structures; and improves the consistency and repeatability of wafer-level devices. Multiple MEMS micro-hotplates with identical structures are arranged on the entire wafer, with unified power supply and heating. This enables simultaneous growth of high-performance gas-sensitive materials at the wafer level; significantly improves sensor batch production efficiency and yield; supports large-scale, low-cost gas-sensitive chip manufacturing; and is suitable for the large-scale application of future flexible and intelligent sensing systems.

[0107] In2O3 nanomaterials, due to their high specific surface area, abundant oxygen vacancies, and excellent conductivity modulation capabilities, can efficiently detect gases such as NO2, CO, and H2S. The micro-region temperature-controlled structure supports dynamic adjustment of the operating temperature, enhancing gas recognition capabilities and sensitivity. A sensor array is constructed based on In2O3 materials grown at multiple different micro-region temperatures; the differences in response modes of each sensor can be used for fingerprint-based odor analysis. Applications include food safety, medical diagnostics, and environmental monitoring. By combining MEMS micro-hotplate technology with chemical vapor deposition (CVD), the directional growth of In2O3 nanomaterials—characterized by micro-region positioning, morphological control, and wafer-level consistency—is achieved.

[0108] Although embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of 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 directional growth of In203 nano-materials, characterized in that, The method comprises the following steps: Step S1, preparing a silicon substrate with heating electrodes and test electrodes as an In2O3 growth carrier, wherein Step S11, the silicon substrate is pretreated, and the silicon substrate is sequentially placed in acetone and ethanol solutions for ultrasonic cleaning; Step S12, at least one MEMS micro-hotplate is formed on the silicon substrate by using a MEMS process as the In2O3 growth carrier, and the MEMS micro-hotplate comprises a plurality of groups of heating electrodes and test electrodes with consistent structures; Step S2, In2O3 nanomaterial is directionally grown under the micro-area thermal induction of the heating electrodes by chemical vapor deposition with trimethyl indium as an indium gas source and oxygen as an oxygen source, wherein Step S21, the MEMS micro-hotplate is installed in a reaction deposition area of a double-temperature-zone reaction furnace, the reaction furnace chamber is closed, and the pressure in the reaction furnace chamber is extracted to a predetermined pressure range by vacuum extraction; Step S22, In2O3 nanomaterial growth parameter control, the trimethyl indium vapor flow is adjusted to be carried into the reaction furnace chamber by a carrier gas, O2 flow is adjusted at the same time, a direct current power source is connected to the positive and negative electrodes of the heating electrodes of the MEMS micro-hotplate, the current size is adjusted according to the resistance of the heating electrodes and the target heating temperature, the heating electrodes are heated, a micro-area thermal field is formed on the silicon substrate, the trimethyl indium vapor and the oxygen react in a high-temperature environment in the reaction deposition area, and In2O3 nanomaterial is directionally grown in the heating area of the silicon substrate, the ratio of the trimethyl indium vapor to O2 flow is controlled by a mass flow controller and is between 5:1 and 40:1, the growth time of the In2O3 nanomaterial is 0.5-3h, and the high-temperature environment is 300-600℃.

2. The method according to claim 1, wherein the In203 nano-material is grown in a direction of In step S11, the silicon substrate is sequentially placed in acetone and ethanol solutions for ultrasonic cleaning for 15-20 min to remove surface oil stains and organic impurities, .​ In step S12, the material of the heating electrodes and the test electrodes deposited on the silicon substrate is Au, the deposition thickness is between 100-400 nm, and a layer of Cr with a thickness of 10-100 nm is deposited between the Au and the silicon substrate to increase the adhesion between the electrodes and the substrate.

3. The method according to claim 1, wherein the In203 nano-material is grown in a direction of In step S12, the test electrodes are isolated from the heating electrodes by a dielectric layer and are in the micro-area of the temperature control of the MEMS micro-hotplate. .​ 4. The method according to claim 1, wherein the method is characterized by, In step S21, the pressure in the chamber is drawn to 10 -1 - 10 -3 Pa of the predetermined pressure range; In step S22, the growth time of the In2O3 thin film, the micro-area heating temperature on the silicon substrate and the trimethyl indium vapor and O2 flow are controlled to directionally grow In2O3 nanomaterial.

5. The method according to claim 1, wherein the method is characterized by: The temperatures of each micro-area are the same to obtain consistent In2O3 nanomaterial, or the temperature distribution and gradient change of each micro-area realize the directional and controllable growth of In2O3 nanomaterial in each micro-area.

6. A directed growth apparatus implementing the method of any one of claims 1-5, wherein, The method comprises, a tubular furnace, which is provided with a reaction furnace chamber and a gas inlet communicating with the reaction furnace chamber, and is provided with a porcelain boat for loading trimethyl indium to form trimethyl indium vapor, a carrier gas source, which is provided with a carrier gas for carrying trimethyl indium and is connected to the gas inlet, an oxygen source, which is provided with oxygen and is connected to the gas inlet, a flow controller, which is connected to the carrier gas source and the oxygen source to adjust the trimethyl indium vapor and O2 flow and their ratio; a vacuum pump, which is connected to the reaction furnace chamber to extract vacuum, a pressure gauge connected to the reaction furnace chamber to detect pressure data, a MEMS micro-hotplate provided in the reaction furnace chamber and in a reaction gas composed of trimethylindium vapor and O2, the MEMS micro-hotplate comprising a heating electrode and a test electrode; a direct current power supply device connected to the heating electrode to heat a micro-region, a temperature control console connected to the direct current power supply device to adjust the temperature of the micro-region, and the micro-region of the MEMS micro-hotplate is oriented to grow indium oxide nanomaterials.

7. An In203 sensor, characterized by which is made by the method of any one of claims 1-5.

8. An electronic nose characterized in that, which comprises the In2O3 sensor of claim 7. which comprises the In2O3 sensor of claim 7.

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