A method for enhancing the gas-sensing properties of gallium oxide polycrystalline thin films using wet etching

Abstract

A method for enhancing the gas-sensing performance of gallium oxide polycrystalline thin films using wet etching, belonging to the field of semiconductor gas sensors. The fabrication method includes the following steps: Step 1. Sputtering a gallium oxide thin film on a silicon dioxide wafer using a magnetron sputtering machine; Step 2. Transforming the gallium oxide thin film into a polycrystalline thin film using thermal annealing; Step 3. Forming nano-pits and grafting high-energy dangling bonds on the gallium oxide polycrystalline thin film using wet etching; Step 4. Generating interdigitated electrode regions on the gallium oxide thin film using photolithography; Step 5. Sputtering Ti / Pt electrodes on the gallium oxide thin film using a magnetron sputtering machine; Step 6. Removing photoresist by ultrasonic immersion in acetone solution. A gallium oxide gas-sensing element prepared using this material as the sensing material achieves a sensitivity of 25% at a 300 ppm ammonia concentration, and exhibits high selectivity for ammonia.

Description

Technical Field

[0001] This invention belongs to the field of gas sensor and its fabrication technology, specifically relating to a method for enhancing the gas-sensing performance of gallium oxide polycrystalline thin films using wet etching, and a method for fabricating gallium oxide thin film gas sensors. Background Technology

[0002] Breathing is a primary indicator of human physiological state. Detecting the concentration of certain components in exhaled breath can provide a preliminary assessment of an individual's potential health conditions. Kidney disease, in particular, urgently needs early screening for detection. The concentration of ammonia in exhaled breath can indicate whether a person has kidney disease. Healthy individuals exhale ammonia at a concentration of 0.4-1.8 ppm, while patients with kidney disease exhale ammonia at a concentration of 0.8-14.7 ppm. Therefore, breath analysis plays a crucial role in the early screening and assessment of potential diseases.

[0003] Traditional respiratory component monitoring primarily relies on methods such as gas chromatography, which can accurately record various functional indicators of patients in clinical practice. However, due to their high testing costs, complex testing processes, and the need for professional data analysis and processing, they are difficult to use for timely detection and intervention of kidney disease in daily life. In recent years, facing the urgent need for screening and monitoring kidney disease patients, people have been seeking a low-barrier, real-time respiratory analysis method.

[0004] Using gallium oxide (GaO) as a sensing material to detect ammonia is a feasible method. Its gas-sensing mechanism involves gas molecules in the environment taking or releasing electrons from GaO, causing a change in the thin-film resistance. The concentration of the gas in the environment is then calculated based on this change in resistance. Ammonia, as a reducing gas, transfers electrons to GaO upon contact, leading to a decrease in GaO resistance and an increase in conductivity. GaO offers several advantages as a gas-sensing material: its simple structure, low cost, and ease of fabrication without expensive equipment, coupled with its ability to be easily integrated and miniaturized into portable devices. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a method for enhancing the gas-sensing properties of gallium oxide polycrystalline thin films using wet etching, comprising the following steps: Step 1. A gallium oxide thin film is grown on the substrate using magnetron sputtering; Step 2. The gallium oxide thin film is treated by thermal annealing; Step 3. The gallium oxide polycrystalline thin film is treated using a wet etching method; Step 4. Perform patterning photolithography on the gallium oxide polycrystalline thin film; Step 5. Growing electrodes on a gallium oxide polycrystalline thin film using magnetron sputtering; Step 6. Remove the photoresist from the gallium oxide polycrystalline thin film.

[0006] Furthermore, in step 1, the magnetron sputtering power is 30-200 W, the introduced gas is argon, the gas flow rate is 30-100 sccm, the pressure in the chamber during magnetron sputtering is 0.5±0.2 Pa, and the sputtering time is 10-60 min.

[0007] Furthermore, in step 2, the gas atmosphere during the thermal annealing process is nitrogen, air, or oxygen, the thermal annealing temperature is 600-900 ℃, and the annealing time is 30-120 min.

[0008] Furthermore, in step 3, the gallium oxide wet etching process uses a 5 wt% to 50 wt% potassium hydroxide (KOH) aqueous solution, and the etching is carried out at a temperature of 25 to 100°C for 10 to 120 minutes.

[0009] Furthermore, in step 5, titanium (Ti) or chromium (Cr) electrodes are first grown by magnetron sputtering, and then platinum (Pt) or gold (Au) electrodes are grown by magnetron sputtering. The width of the electrodes is 10~100μm and the spacing between the electrodes is 2~20μm.

[0010] A gas sensor device with enhanced gas-sensing properties of gallium oxide polycrystalline thin films by wet etching is prepared by the above-described method.

[0011] An application of a gas sensor device that enhances the gas-sensing performance of a gallium oxide polycrystalline thin film using wet etching is disclosed. The gallium oxide polycrystalline thin film after wet etching is used for the detection of ammonia gas and is applied to the monitoring of ammonia concentration in human exhaled gas.

[0012] The beneficial effects of this invention are as follows: This invention solves the performance problems of gallium oxide gas sensors in ammonia sensing or kidney disease screening, reducing the detection limit and selectivity of the gas sensors among multi-component similar target gas molecules. Through high-temperature annealing for a certain period, the amorphous gallium oxide film is transformed into α-Ga₂O₃ and β-Ga₂O₃, giving it directional gas molecule adsorption capabilities. Furthermore, by using a KOH solution of a certain concentration to wet-etch the surface of the polycrystalline gallium oxide film, nano-pits are formed while high-energy dangling bonds are grafted, which to some extent increases the specific surface area of ​​the Ga₂O₃ gas-sensitive material and reduces the adsorption energy of ammonia molecules with Ga₂O₃, thereby improving the sensitivity, selectivity, and detection limit of the gallium oxide gas sensor. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the fabrication process of the gas-sensitive device described in this invention.

[0014] Figure 2This is a layout of the interdigitated electrodes of the gas-sensitive device described in this invention.

[0015] Figure 3 This is a schematic diagram of the interdigitated electrodes of the gas-sensitive device described in this invention.

[0016] Figure 4 This is the X-ray diffraction spectrum of the gallium oxide polycrystalline material in the gas-sensitive device of the present invention.

[0017] Figure 5 This is a schematic diagram of the gas-sensitive device described in this invention responding to 50 ppm ammonia gas. Detailed Implementation

[0018] To overcome the shortcomings of existing technologies, the technical problem to be solved by this invention is to provide a gas-sensitive material that operates at room temperature and simultaneously achieves a low detection limit, thereby providing a method for accurately detecting the concentration of ammonia gas in the air. To achieve the above objective, the technical solution adopted by this invention is as follows: A method for enhancing the gas-sensing properties of gallium oxide polycrystalline thin films using wet etching includes the following steps: Step 1: Magnetron sputtering of gallium oxide thin film: A gallium oxide thin film is sputtered on a clean substrate. The sputtering power is 80 W, the argon flow rate is 30 sccm, and the background pressure is 8 × 10⁻⁶. -4 Pa, the chamber pressure during sputtering is 0.5 Pa, and the sputtering time is 20 minutes.

[0019] Step 2: Thermal Annealing: Place the sample from Step 1 into an RTP annealing furnace and anneal it in an oxygen atmosphere for 30 minutes. This step is to make the gallium oxide film more resistant to wet etching.

[0020] Step 3: Wet etching treatment: Immerse the sample from Step 2 in a 20% KOH solution and etch it at 60℃ for 30 min. After etching, rinse the sample with deionized water.

[0021] Step 4: Photolithography on the sample: Photolithography is performed on the surface of the gallium oxide thin film, and the lithographic pattern is an interdigitated electrode.

[0022] Step 5: Electrode fabrication: Ti / Pt electrodes are grown on the sample using magnetron sputtering.

[0023] Step Six: Resin Removal: Use NMP to remove the adhesive from the sample from Step Five to complete the fabrication of the gas-sensitive element.

[0024] Furthermore, in the above technical solution, the substrate in step one is either alumina or silicon dioxide. The magnetron sputtering power is 30-200 W, the introduced gas is argon, the gas flow rate is 30-100 sccm, and the background pressure is 1×10⁻⁶. -4Pa ~ 1×10 -3 Pa.

[0025] Furthermore, in the above technical solution, the gas atmosphere in step two is nitrogen, air, or oxygen. The annealing temperature is 600-900 ℃, and the annealing time is 30-120 min.

[0026] Furthermore, in the above technical solution, the gallium oxide wet etching in step three uses either potassium hydroxide (KOH) aqueous solution or sodium hydroxide (NaOH) aqueous solution, with a mass fraction of 5 wt%~50 wt%, and is etched at a temperature of 25~100℃ for 10 min~120 min.

[0027] Furthermore, in the above technical solution, in step five, a titanium (Ti) or chromium (Cr) electrode is first grown by magnetron sputtering, and then a platinum (Pt) or gold (Au) electrode is grown by magnetron sputtering.

[0028] Furthermore, in the above technical solution, NMP or acetone is used to remove the adhesive in step six.

[0029] To make the technical means and objectives of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0030] Example 1 A gas sensor device for enhancing the gas-sensing performance of a gallium oxide polycrystalline thin film by wet etching is disclosed. The device structure includes a 500 μm thick silicon layer, a 300 nm thick silicon oxide layer, a 75 nm thick gallium oxide layer, and a Ti / Pt electrode.

[0031] The specific steps are as follows (e.g.) Figure 1 (as shown) Step 1: Surface pretreatment of silicon dioxide wafers: Place the cut silicon dioxide wafers in acetone solution and ultrasonically clean for 10 minutes. Remove the silicon dioxide wafers and ultrasonically clean them in anhydrous ethanol for 10 minutes. Then, ultrasonically clean the silicon dioxide wafers in deionized water for 10 minutes to remove metal ions and attached organic matter from the surface of the silicon dioxide wafers. Dry the surface of the silicon dioxide wafers with a nitrogen gun and set aside for later use.

[0032] Step 2: Sputter a gallium oxide thin film onto a cleaned silicon dioxide wafer using magnetron sputtering. The sputtering power is 80 W, the argon flow rate is 30 sccm, and the background pressure is 8 × 10⁻⁶. -4 Pa, the chamber pressure during sputtering is 0.5 Pa, and the sputtering time is 20 min.

[0033] Step 3: Place the sample in an RTP annealing furnace and anneal at 800°C for 30 min in an oxygen atmosphere.

[0034] Step 4: Immerse the sample in a 20% KOH solution at 60°C for 30 minutes.

[0035] Step 5: After photolithography and development, interdigitated electrode regions are formed on the sample. Ti / Pt metal is then sputtered onto these regions using magnetron sputtering. Excess metal is removed by ultrasonic removal after immersion in acetone.

[0036] The gas-sensing performance of the fabricated gallium oxide polycrystalline thin film was tested using planar interdigitated electrodes. The obtained gallium oxide polycrystalline gas-sensing material exhibits high sensitivity and high gas-sensing selectivity to ammonia. At room temperature, the sensitivity of the gallium oxide polycrystalline gas-sensing material to 50 ppm ammonia is approximately 30%.

[0037] Example 2 The performance testing of the sensitive element was conducted according to methods disclosed in the art. Specifically, the gas-sensitive element was tested using a Keithley 2450 SourceMeter. Different ammonia concentrations were prepared by evaporating 28% ammonia solution in 1 L narrow-mouthed bottles. The current of the element prepared in Example 1 under different ammonia concentration equilibrium states was read under 1 V DC. Figure 5 As shown, the current-time curves of the test element when switching between air and 50 ppm ammonia concentrations have response recovery times of 27.6 seconds and 1.8 seconds, respectively.

[0038] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for enhancing the gas-sensing properties of gallium oxide polycrystalline thin films using wet etching, characterized in that, Includes the following steps: Step 1. A gallium oxide thin film is grown on the substrate using magnetron sputtering; Step 2. The gallium oxide thin film is treated by thermal annealing. The gas atmosphere during the thermal annealing process is nitrogen, air or oxygen, the thermal annealing temperature is 600-900 ℃, and the gallium oxide thin film is annealed for 30-120 min to obtain a gallium oxide polycrystalline thin film. Step 3. The gallium oxide polycrystalline thin film is treated by wet etching. The gallium oxide wet etching uses a 5 wt%~50 wt% potassium hydroxide (KOH) aqueous solution and is etched at a temperature of 25~100℃ for 10 min~120 min. Step 4. Perform patterning photolithography on the gallium oxide polycrystalline thin film; Step 5. Growing electrodes on a gallium oxide polycrystalline thin film using magnetron sputtering; Step 6. Remove the photoresist from the gallium oxide polycrystalline thin film.

2. The method for enhancing the gas-sensing properties of gallium oxide polycrystalline thin films by wet etching according to claim 1, characterized in that, In step 1, the magnetron sputtering power is 30-200 W, the introduced gas is argon, the gas flow rate is 30-100 sccm, the pressure in the chamber during magnetron sputtering is 0.5±0.2 Pa, and the sputtering time is 10-60 min.

3. The method for enhancing the gas-sensing properties of gallium oxide polycrystalline thin films by wet etching according to claim 1, characterized in that, In step 5, titanium (Ti) or chromium (Cr) electrodes are first grown by magnetron sputtering, and then platinum (Pt) or gold (Au) electrodes are grown by magnetron sputtering. The width of the electrodes is 10~100μm and the spacing between the electrodes is 2~20μm.

4. A gas sensor device for enhancing the gas-sensing performance of gallium oxide polycrystalline thin films using wet etching, characterized in that, It is prepared by the method described in any one of claims 1 to 3.

5. An application of a gas sensor device with enhanced gas-sensing performance of gallium oxide polycrystalline thin film by wet etching as described in claim 4, characterized in that, Gallium oxide polycrystalline thin films after wet etching are used for ammonia detection and applied to monitor ammonia concentration in human exhaled gas.

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