A selectively enhanced semiconductor gas sensor and method of manufacture thereof

Abstract

The application belongs to the technical field of sensors, and particularly relates to a selectively enhanced semiconductor gas sensor and a manufacturing method thereof. The method deposits a molecular sieve filter layer on a semiconductor gas-sensitive material layer, and realizes selective improvement of the gas sensor by regulating the pores and pore diameters of the molecular sieve filter layer. The deposition method comprises the following steps: self-assembling and adsorbing inhibitor and promoter monolayers on the surface of the gas-sensitive material particles; removing the promoter monolayer and retaining the inhibitor monolayer; self-assembling and adsorbing molecular sieve precursor monolayers on the surface of the gas-sensitive material particles in the inhibitor-free areas; forming molecular sieve material monolayers from the molecular sieve precursor monolayers; repeating the above-mentioned processes of adsorbing the molecular sieve precursor monolayers and forming the molecular sieve material monolayers to form the molecular sieve material; and removing the inhibitor monolayer to form the molecular sieve filter layer with certain pores and pore diameters. The application improves the poor selectivity of the semiconductor gas sensor by introducing the molecular sieve filter layer.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology, specifically relating to a selectively enhanced semiconductor gas sensor and its manufacturing method. Background Technology

[0002] There are many types of gas sensors, including semiconductor, optical, electrochemical, catalytic combustion, and thermal conductivity types. Semiconductor gas sensors are a type of chemical sensor that has been widely used due to their high sensitivity, low cost, and simple application circuits. However, the detection principle of semiconductor gas sensors determines that their selectivity is often poor, and interfering gases in the environment can easily have an adverse effect on the detection accuracy, which limits the further expansion of their application range. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a semiconductor gas sensor with a molecular sieve filter layer.

[0004] The technical solution provided by this invention is as follows:

[0005] A method for manufacturing a selectively enhanced semiconductor gas sensor includes first fabricating a semiconductor gas sensor body with a semiconductor gas-sensitive material layer, then depositing a molecular sieve filter layer on the semiconductor gas-sensitive material layer of the body, and adjusting the selectivity of the gas sensor by controlling the pore size and channels of the molecular sieve filter layer. The deposition method of the molecular sieve filter layer includes the following steps:

[0006] 1) A mixed layer of adsorption inhibitors and promoters monomolecules is self-assembled on the surface of gas-sensitive nanoparticles;

[0007] 2) Remove the promoter monomolecule from the mixed layer of inhibitor and promoter monomolecules obtained in step 1), and retain the inhibitor monomolecule to obtain an inhibitor monolayer;

[0008] 3) Self-assemble adsorbed molecular sieve precursor monomolecules in the region without inhibitor on the surface of gas-sensitive material nanoparticles to obtain a mixed layer of inhibitor and adsorbed molecular sieve precursor monomolecules.

[0009] 4) The molecular sieve precursor monomolecules in the mixed layer of the inhibitor and the adsorbed molecular sieve precursor monomolecules obtained in step 3) are converted into molecular sieve material monomolecules to obtain a mixed layer of inhibitor and molecular sieve material monomolecules.

[0010] 5) The molecular sieve precursor molecules are self-assembled and adsorbed on the molecular sieve material monomolecules in the mixed layer of the inhibitor and molecular sieve material monomolecules obtained in step 4), resulting in a new layer of molecular sieve precursor monomolecules.

[0011] 6) The new molecular sieve precursor monolayer obtained in step 5) is converted into a new molecular sieve material monolayer.

[0012] 7) Repeat steps 5) and 6) to obtain a molecular sieve material layer with a certain thickness;

[0013] 8) Remove inhibitor molecules to form a molecular sieve filter layer with certain channels and pore size.

[0014] In the above technical solution:

[0015] In the resulting selectively enhanced semiconductor gas sensor, based on the filtering effect of the pores in the molecular sieve filter layer, molecules smaller than the pore size can reach the surface of the semiconductor gas-sensitive material to react and be detected, while molecules larger than the pore size are blocked by the molecular sieve, thereby improving the selectivity of the semiconductor gas sensor.

[0016] During the manufacturing process, the gas sensor is placed in a sealed chamber. At a certain temperature, a certain concentration of inhibitor and promoter molecules are introduced into the gas phase of the chamber. The inhibitor and promoter molecules can self-assemble and adsorb at different positions on the surface of the gas-sensitive material particles. After the adsorption is saturated, an inert gas is purged to remove excess gas molecules in the gas phase, thus forming a mixed layer of inhibitor and promoter monomolecules self-assembled on the surface of the gas-sensitive material particles.

[0017] Specifically, in step 1), by adjusting the type of inhibitor molecules, the ratio and concentration of inhibitor and promoter molecules, and the adsorption temperature conditions, the molecular sieve pore size of 0.4-2 nm and the uniformity of distribution can be controlled.

[0018] Preferred:

[0019] In step 1), the inhibitor is selected from any one of phosphonate or alkyl thiol self-assembled monomolecule materials, with a concentration of 0.1%-20% and an adsorption temperature of ≤100℃;

[0020] In step 1), the promoter is selected from any one of fatty acids or their derivatives, alkyl thiols self-assembled monomolecules or volatile organic solvents, with a concentration of 80%-99.9% and an adsorption temperature of ≤100℃.

[0021] In step 1), the ratio of inhibitor to promoter molecules is (0.001-0.25):1.

[0022] Specifically, in step 2), the inhibitor monolayer can be obtained by changing the temperature conditions and applying the different desorption temperatures of the inhibitor and promoter molecules, retaining the inhibitor monomolecule and removing the promoter monomolecule.

[0023] Preferably, the desorption temperature is ≤150℃.

[0024] Specifically, in step 2), a first reactive gas can be introduced into the gas phase of a sealed chamber. The reactive gas reacts with the promoter molecules but does not react with the inhibitor molecules, thereby removing the promoter monomolecule and retaining the inhibitor monomolecule to obtain the inhibitor monolayer.

[0025] Preferably, the first selective reaction gas is selected from either water vapor or O3.

[0026] Specifically, in step 3), the gas sensor is placed in a sealed chamber, and a certain concentration of molecular sieve precursor molecules are introduced into the gas phase of the chamber at a certain temperature. The molecular sieve precursor molecules are self-assembled and adsorbed in the region of the gas-sensitive material particles without inhibitors. After the adsorption is saturated, an inert gas is purged to remove excess gas molecules in the gas phase, and self-assembled molecular sieve precursor monomolecules are formed in the region of the gas-sensitive material particles without inhibitors, thus obtaining a mixed layer of inhibitor and adsorbed molecular sieve precursor monomolecules.

[0027] Preferred:

[0028] The molecular sieve precursor molecule is selected from any one of trimethylaluminum, silicon tetrachloride, or trimethylgallium;

[0029] Operating temperature ≤150℃.

[0030] Specifically, in step 4), by changing the temperature conditions and applying the different decomposition temperatures of the molecular sieve precursor molecules, the inhibitor monomolecules are retained, causing the molecular sieve precursor monolayer to decompose and form molecular sieve material monomolecules, thus obtaining a mixed layer of the inhibitor and molecular sieve material monomolecules.

[0031] Preferably, the decomposition temperature is 150-200℃.

[0032] Specifically, in step 4), a second reactive gas can be introduced into the gas phase of a closed chamber. The reactive gas reacts with the molecular sieve precursor molecules but does not react with the inhibitor molecules, thereby converting the molecular sieve precursor monolayer into a molecular sieve material monomolecule, resulting in a mixed layer of the inhibitor and the molecular sieve material monomolecule.

[0033] Preferably, the second selective reaction gas is selected from any one of O2 plasma, water vapor, or O3.

[0034] Specifically, the process of adsorption of the molecular sieve precursor monolayer and formation of the molecular sieve material monolayer is repeated repeatedly, with the thickness of the formed molecular sieve preferably in the range of 3-50 nm.

[0035] Preferably, in step 7), the number of repetitions is 10-500.

[0036] Specifically, in step 8), the inhibitor molecules can be removed by changing the temperature conditions to form a molecular sieve filter layer with certain channels and pore sizes.

[0037] Preferably, the removal temperature is ≥200℃.

[0038] Specifically, in step 8), a third reaction gas can be introduced into the gas phase of a closed chamber to remove inhibitor molecules under certain temperature conditions, forming a molecular sieve filter layer with certain channels and pore sizes.

[0039] Preferably, the third selective reaction gas is selected from O2 plasma, and the reaction temperature is 100-200℃.

[0040] Specifically, the molecular sieve filter layer material obtained by the above method is aluminum oxide, silicon dioxide, or gallium oxide.

[0041] The present invention also provides a selectively enhanced semiconductor gas sensor manufactured according to the above method.

[0042] The semiconductor gas sensor of this invention improves the poor selectivity of semiconductor gas sensors by introducing a molecular sieve filter layer. It has low manufacturing costs and is easy to mass-produce. The molecular sieve pores in the filter layer can reach a size of 0.4-2 nm and are uniformly distributed. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the selective molecular layer growth process of the molecular sieve filter layer in the manufacturing method of the selectively enhanced semiconductor gas sensor provided by the present invention.

[0044] Figure 2 The diagram shows the gas sensor's gas-sensing performance before and after molecular sieve deposition in this embodiment.

[0045] Appendix Figure 1 The list of substances represented by each character in the text is as follows:

[0046] I, inhibitor molecule; P, promoter molecule; S, molecular sieve precursor molecule; F, molecular sieve material. Detailed Implementation

[0047] The principles and features of the present invention are described below. The embodiments given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] Example:

[0050] A method for manufacturing a selectively enhanced semiconductor gas sensor includes first manufacturing a semiconductor gas sensor body having a semiconductor gas-sensitive material layer, and then depositing an alumina molecular sieve filter layer on the semiconductor gas-sensitive material layer of the body. The alumina molecular sieve filter layer deposition method includes the following steps:

[0051] 1. The manufactured gas sensor body is placed in a sealed chamber, and a mixture of 20 SCCM octadecylphosphonic acid and biphenyl (molar ratio of 1:10) is introduced into the gas phase of the chamber at 75°C for 10 minutes, with nitrogen as the carrier gas. Then, the chamber is purged with nitrogen for 3 minutes to form a self-assembled mixed monolayer of octadecylphosphonic acid and biphenyl on the surface of the gas-sensitive material particles.

[0052] 2. Raise the temperature of the sealed chamber to 150°C and maintain it for 10 minutes to remove biphenyl self-assembled monomers.

[0053] 3. Maintain the temperature of the sealed chamber at 150℃, use 20 SCCM nitrogen as the carrier gas, introduce trimethylaluminum gas into the chamber for 10 seconds, and then purge with nitrogen for 5 seconds to form self-assembled trimethylaluminum monomolecules in the region of the gas-sensitive material particles without inhibitors.

[0054] 4. Maintain the temperature of the sealed chamber at 150℃, use 20 SCCM nitrogen as the carrier gas, introduce water vapor into the chamber for 10 seconds, and then purge with nitrogen for 5 seconds. Water molecules react with trimethylaluminum molecules to obtain aluminum oxide. A self-assembled monomolecular mixed layer of inhibitor and aluminum oxide is formed in the region of the gas-sensitive material particles without inhibitor. The thickness of the monomolecular mixed layer is 0.15 nm.

[0055] 5. Maintain the temperature of the sealed chamber at 150℃, and alternately introduce trimethylaluminum and water vapor into the chamber for 200 cycles to obtain aluminum oxide with a thickness of 30nm.

[0056] 6. Raise the temperature of the sealed chamber to 200℃, and introduce 20 SCCM of oxygen into the chamber. The inhibitor octadecylphosphonic acid molecules react with the oxygen and are converted into phosphorus pentoxide and water, which are then volatilized and discharged in the gas phase, forming a molecular sieve filter layer with a pore diameter of about 0.5 nm and a thickness of 30 nm.

[0057] In this embodiment, by introducing an alumina molecular sieve filter layer with a pore diameter of approximately 0.5 nm into the semiconductor gas sensor, the response of the gas sensor to volatile organic compounds (VOCs) such as benzene rings is suppressed, while the response to small molecule gases such as hydrogen and methane is not significantly affected. This improves the selectivity of the semiconductor gas sensor, and its process cost is low and it is easy to mass-produce.

[0058] In other implementation examples, using a diphenylsulfide inhibitor, a molecular sieve filter layer with a pore diameter of approximately 1 nm can be introduced; using a 1,3-propanedithiol inhibitor, a molecular sieve filter layer with a pore diameter of approximately 0.7 nm can be introduced. The molecular sieve filter layer can be aluminum oxide, silicon dioxide, or gallium oxide.

[0059] The gas-sensing performance of the gas sensor before and after molecular sieve deposition in the above examples was tested using ethanol (molecular diameter approximately 0.47 nm) and xylene (molecular diameter approximately 0.56 nm) gases. The results are as follows: Figure 2 The figure shows the gas-sensing characteristic curves of the molecular sieve for the gas sensor. Part a represents the gas sensor sensitivity before molecular sieve deposition, and part b represents the gas sensor sensitivity after molecular sieve deposition. It can be seen from the figure that:

[0060] Molecular ethanol can pass through the pores of the molecular sieve. After the molecular sieve is deposited, the sensitivity of the gas sensor to small molecule ethanol does not change much.

[0061] Larger molecules like m-xylene have difficulty passing through the pores of molecular sieves. After the molecular sieves deposit, the sensitivity of the gas sensor to small molecule ethanol is drastically reduced.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for manufacturing a selectively enhanced semiconductor gas sensor, comprising depositing a molecular sieve filter layer on a semiconductor gas-sensitive material layer, and adjusting the selectivity of the gas sensor by controlling the pore size and channel of the molecular sieve filter layer, characterized in that... The deposition method of its molecular sieve filter layer includes the following steps: 1) A mixed layer of adsorption inhibitors and promoters monomolecules is self-assembled on the surface of gas-sensitive nanoparticles; 2) Remove the promoter monomolecule from the mixed layer of inhibitor and promoter monomolecules obtained in step 1), and retain the inhibitor monomolecule to obtain an inhibitor monolayer; 3) Self-assemble adsorbed molecular sieve precursor monomolecules in the region without inhibitor on the surface of gas-sensitive material nanoparticles to obtain a mixed layer of inhibitor and adsorbed molecular sieve precursor monomolecules. 4) The molecular sieve precursor monomolecules in the mixed layer of the inhibitor and the adsorbed molecular sieve precursor monomolecules obtained in step 3) are converted into molecular sieve material monomolecules to obtain a mixed layer of inhibitor and molecular sieve material monomolecules. 5) The molecular sieve precursor molecules are self-assembled and adsorbed on the molecular sieve material monomolecules in the mixed layer of the inhibitor and molecular sieve material monomolecules obtained in step 4), resulting in a new layer of molecular sieve precursor monomolecules. 6) The new molecular sieve precursor monolayer obtained in step 5) is converted into a new molecular sieve material monolayer. 7) Repeat steps 5) to 6) several times to obtain a molecular sieve material layer with a certain thickness; 8) Remove inhibitor molecules to form a molecular sieve filter layer with certain channels and pore size.

2. The method for manufacturing a selectively enhanced semiconductor gas sensor according to claim 1, characterized in that: In step 1), the size and / or uniformity of molecular sieve channels are controlled by adjusting any one or more of the following conditions: the type of inhibitor molecule, the ratio of inhibitor to promoter molecules, the inhibitor concentration, the promoter concentration, the inhibitor adsorption temperature, or the promoter adsorption temperature.

3. The method for manufacturing a selectively enhanced semiconductor gas sensor according to claim 1, characterized in that: In step 2), by setting temperature conditions and taking advantage of the different desorption temperatures of inhibitor and promoter molecules, promoter monomolecules are removed while inhibitor monomolecules are retained to obtain the inhibitor monolayer.

4. The method for manufacturing a selectively enhanced semiconductor gas sensor according to claim 1, characterized in that: In step 2), a first selective reactive gas is introduced into the gas phase of a sealed chamber. The selective reactive gas reacts with the promoter molecules but does not react with the inhibitor molecules, thereby removing the promoter monomolecules and retaining the inhibitor monomolecules to obtain the inhibitor monolayer.

5. The method for manufacturing a selectively enhanced semiconductor gas sensor according to claim 1, characterized in that: In step 4), by setting temperature conditions, the molecular sieve precursor single molecules are decomposed into molecular sieve material single molecules by applying different decomposition temperatures, while the inhibitor single molecules are retained, thus obtaining a mixed layer of inhibitor and molecular sieve material single molecules.

6. The method for manufacturing a selectively enhanced semiconductor gas sensor according to claim 1, characterized in that: In step 4), a second selective reactive gas is introduced into the gas phase of a sealed chamber. The reactive gas reacts with the molecular sieve precursor molecules but does not react with the inhibitor molecules, thereby converting the molecular sieve precursor monomolecules into molecular sieve material monomolecules, resulting in a mixed layer of inhibitor and molecular sieve material monomolecules.

7. The method for manufacturing a selectively enhanced semiconductor gas sensor according to claim 1, characterized in that: In step 8), by setting temperature conditions, inhibitor molecules are removed to form a molecular sieve filter layer with certain channels and pore sizes.

8. The method for manufacturing a selectively enhanced semiconductor gas sensor according to claim 1, characterized in that: In step 8), a third reaction gas is introduced into the gas phase of a closed chamber to remove the inhibitor monolayer and form a molecular sieve filter layer with certain channels and pore sizes.

9. A method for manufacturing a selectively enhanced semiconductor gas sensor according to any one of claims 1 to 8, characterized in that: The material of the molecular sieve filter layer is aluminum oxide, silicon dioxide, or gallium oxide.

10. A selectively enhanced semiconductor gas sensor obtained by the manufacturing method according to any one of claims 1 to 9.

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