Sensitive layer and preparation method thereof, MEMS gas sensor and preparation method thereof, and air conditioner

Abstract

The invention discloses a sensitive layer and a preparation method thereof, an MEMS gas sensor and a preparation method thereof, and an air conditioner, the preparation method of the sensitive layer comprises the following steps: dispersing a sensitive material in photoresist to obtain sensitive material slurry; the sensitive material slurry is coated on a substrate to form a slurry coating, the patterning of the slurry coating is realized by adopting a photoetching process, and then the sensitive layer is obtained through heat treatment. According to the preparation method of the sensitive layer, the compatibility of a photoetching process in the preparation method can be improved, the process flow is reduced, the consistency of products is improved, and the production cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of gas sensors, and in particular to a sensitive layer and a preparation method thereof, a MEMS gas sensor and a preparation method thereof, and an air conditioner. Background Art

[0002] In the related art, the production process of the gas sensor involves the production of a micro-electro-mechanical system (MEMS) micro-hotplate and the coating of the gas-sensitive material on the micro-hotplate. Specifically, the heating element and the measuring circuit are made on the silicon plane through sputtering, deposition, etching, photolithography, scribing and other process steps to obtain a MEMS micro-hotplate, and then the gas-sensitive material is coated on the micro-hotplate to obtain a gas sensor. Among them, the MEMS micro-hotplate has the advantages of small size, low power consumption, low cost, and easy integration. In the prior art, when the MEMS micro-hotplate is coated with gas-sensitive materials, inkjet printing, sputtering, physical vapor deposition (PVD) or spraying are generally used. However, the inkjet printing method is adopted, but its ink dots are difficult to control, and the requirements for the printed slurry are extremely high. It is only suitable for some slurries with lower viscosity and does not meet the needs of industrial production. However, the gas-sensing performance of the material will be reduced by sputtering, PVD or spraying, which will affect the gas-sensing performance of the material and is not suitable for high-sensitivity detection requirements. In addition, the prior art also discloses the use of dispensing technology to prepare the sensitive layer, but this process is similar to inkjet printing, and the uniformity of the sensitive coating produced is poor, the thickness is uneven, and single-point operation is required, which reduces production efficiency. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, one object of the present invention is to provide a method for preparing a sensitive layer, which is simple.

[0004] Another object of the present invention is to provide a sensitive layer.

[0005] Another object of the present invention is to provide a method for preparing a MEMS gas sensor.

[0006] Another object of the present invention is to provide a MEMS gas sensor.

[0007] Another object of the present invention is to provide an air conditioner.

[0008] According to a first aspect of an embodiment of the present invention, a method for preparing a sensitive layer comprises the following steps: dispersing a sensitive material in a photoresist to obtain a sensitive material slurry; coating the sensitive material slurry on a substrate to form a slurry coating, patterning the slurry coating by a photolithography process, and then subjecting the slurry coating to a heat treatment to obtain a sensitive layer.

[0009] According to the preparation method of the sensitive layer of the present invention, the sensitive material is dispersed in the photoresist to form a sensitive material slurry, and the slurry coating is patterned by photolithography, and then the sensitive layer is obtained by heat treatment. In this way, the compatibility of the photolithography in the preparation method of the present invention can be improved, the process flow can be reduced, the consistency of the product can be improved, and the production cost can be reduced. The accuracy of the patterning of the product is improved, a porous film structure with a larger specific surface area can be obtained, and the graphic design freedom can be improved. Here, the sensitive material can be a gas sensitive material, for example, a material that is sensitive to CO, formaldehyde gas, etc.

[0010] According to some embodiments of the present invention, in the sensitive material slurry, the material-liquid ratio of the sensitive material and the photoresist satisfies: sensitive material: photoresist = 2g~5.5g:8ml~10ml; preferably: 1g:3ml.

[0011] According to some embodiments of the present invention, the photolithography process includes: pre-baking, exposure and development, and hardening.

[0012] According to some embodiments of the present invention, the pre-baking temperature is 75° C. to 120° C., and the time is 1 min to 5 min; and / or the film hardening temperature is 200° C. to 300° C., and the film hardening time is 30 min to 60 min.

[0013] According to some embodiments of the present invention, the heat treatment is calcination at 400° C. to 600° C., and the calcination time is 1 h to 3 h.

[0014] According to some embodiments of the present invention, the sensitive material includes: SnO2 and / or W2O3.

[0015] According to some embodiments of the present invention, the sensitive material further includes: PdCl2 and / or PdO; the weight ratio of the PdCl2 and / or PdO to the SnO2 and / or W2O3 satisfies: 1:0.005 to 1:0.05.

[0016] According to some embodiments of the present invention, the sensitive material further includes: glass powder; and / or a weight ratio of the SnO2 and / or W2O3 to the glass powder satisfies: 1-2:0.1-0.2.

[0017] According to some embodiments of the present invention, the substrate is a wafer.

[0018] According to an embodiment of the second aspect of the present invention, the present invention provides a sensitive layer, and the sensitive layer is prepared by the preparation method described in the embodiment of the first aspect of the present invention.

[0019] According to some embodiments of the present invention, the thickness of the sensitive layer is d1, wherein d1 satisfies: 5um≤d1≤15um.

[0020] According to an embodiment of the third aspect of the present invention, the present invention provides a method for preparing a MEMS gas sensor, characterized in that it comprises the following steps:

[0021] dispersing the sensitive material into the photoresist to obtain a sensitive material slurry;

[0022] The sensitive material slurry is coated on the wafer to form a slurry coating, and the slurry coating is patterned by a photolithography process.

[0023] After back cavity etching and heat treatment, a MEMS gas sensor is obtained.

[0024] According to an embodiment of a fourth aspect of the present invention, the present invention provides a MEMS gas sensor, comprising:

[0025] a micro-hotplate having an active area;

[0026] A sensitive layer is formed in the active area, and the sensitive layer is prepared by the preparation method described in the embodiment of the first aspect of the present invention, or the sensitive layer is the sensitive layer described in the embodiment of the second aspect of the present invention.

[0027] According to some embodiments of the present invention, the micro-hotplate comprises:

[0028] substrate;

[0029] A first supporting layer, the first supporting layer being provided on surfaces of both sides of the substrate in a thickness direction;

[0030] A second supporting layer, a heating electrode, an isolation layer and a testing electrode are stacked in sequence on one side of the first supporting layer in a thickness direction away from the substrate in a direction away from the substrate.

[0031] According to some embodiments of the present invention, the thickness of the substrate is d2, wherein d2 satisfies: 350um≤d2≤650um; and / or

[0032] The thickness of the first supporting layer is d3, wherein d3 satisfies: 1um≤d3≤2.5um; and / or

[0033] The stress of the first supporting layer is P1, wherein P1 satisfies: -150Mpa≤P1≤-400Mpa; and / or

[0034] The thickness of the second supporting layer is d4, wherein d4 satisfies: 100nm≤d4≤300nm; and / or

[0035] The stress of the second supporting layer is P2, wherein P2 satisfies: 150Mpa≤P2≤400Mpa; and / or

[0036] The thickness of the heating electrode is d5, wherein d5 satisfies: 150nm≤d5≤300nm; and / or

[0037] The thickness of the isolation layer is d6, wherein d6 satisfies: 100nm≤d6≤200nm; and / or

[0038] The thickness of the test electrode is d7, wherein d7 satisfies: 150nm≤d7≤400nm.

[0039] According to an embodiment of the fifth aspect of the present invention, the present invention provides an air conditioner, comprising a MEMS gas sensor prepared by the preparation and release method described in the embodiment of the third aspect of the present invention, or a MEMS gas sensor described in the embodiment of the fourth aspect of the present invention.

[0040] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0042] Figure 1 is a process flow chart of a method for preparing a MEMS gas sensor according to an embodiment of the present invention;

[0043] Figure 2 According to the present invention Figure 1 A schematic diagram of a product structure of the operation step of step 01 in the process flow chart;

[0044] Figure 3 According to the present invention Figure 1 A schematic diagram of a product structure of an operation step of step 02 in the process flow chart;

[0045] Figure 4 According to the present invention Figure 1 A schematic diagram of a product structure of the operation step of step 03 in the process flow chart;

[0046] Figure 5 According to the present invention Figure 1 A schematic diagram of a product structure of the operation step of step 04 in the process flow chart;

[0047] Figure 6 According to the present invention Figure 1 A schematic diagram of a product structure of the operation step of step 05 in the process flow chart;

[0048] Figure 7 According to the present invention Figure 1 A schematic diagram of a product structure of the operation step of step 06 in the process flow chart;

[0049] Figure 8 According to the present invention Figure 1 A schematic diagram of a product structure of the operation step of step 07 in the process flow chart;

[0050] Fig. 9 According to the present invention Figure 1 A schematic diagram of a product structure of the operation step of step 08 in the process flow chart;

[0051] Fig.10 According to the present invention Figure 1 A schematic diagram of a product structure of the operation step of step 09 in the process flow chart;

[0052] Fig.11 According to the present invention Figure 1 A schematic diagram of a product structure of the operation step of step 010 in the process flow chart;

[0053] Fig.12 According to the present invention Figure 1 A schematic diagram of a product structure of the operation step of step 011 in the process flow chart;

[0054] Fig.13 According to the present invention Figure 1 A schematic diagram of a product structure of the operation step of step 012 in the process flow chart;

[0055] Fig.14 According to the present invention Figure 1 A schematic diagram of a product structure of the operation step of step 013 in the process flow chart;

[0056] Fig.15 According to the present invention Figure 1 A schematic diagram of a product structure of the operation step of step 014 in the process flow chart;

[0057] Fig.16 According to the present invention Figure 1A schematic diagram of a product structure of the operation step of step 015 in the process flow chart;

[0058] Fig.17 Response curves of the MEMS gas sensor obtained by the process of specific embodiment 1 of the present invention, the MEMS gas sensor obtained by the process of embodiment 2, and the MEMS gas sensor obtained by the process of embodiment 3 in a 10 ppm CO gas environment;

[0059] Fig.18 4 is a perspective diagram of a MEMS gas sensor structure according to a specific embodiment of the present invention.

[0060] 100: MEMS gas sensor;

[0061] 1: substrate; 2: first supporting layer; 3: second supporting layer; 4: heating electrode; 5: photoresist; 6: isolation layer; 7: test electrode; 8: photoresist containing sensitive material; 9: sensitive layer. DETAILED DESCRIPTION

[0062] The embodiments of the present invention are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. Figure 1 and Fig.14 , specifically describing the preparation method of the sensitive layer 9 of the first aspect of the present invention. The preparation method of the sensitive layer 9 of the first aspect of the present invention comprises: dispersing the sensitive material in the photoresist 5 to obtain a sensitive material slurry. In this way, the present invention uses the photoresist 5 as a dispersant for the sensitive material, and can achieve uniform dispersion of the sensitive material in the photoresist 5, thereby facilitating uniform dispersion and coating of the sensitive material slurry.

[0063] Furthermore, the sensitive material slurry is coated on the substrate to form a slurry coating, and the slurry coating is patterned by a photolithography process, and then subjected to heat treatment to obtain a sensitive layer 9. In this way, the photolithography process is applied to the preparation method of the sensitive layer 9 by utilizing the photosensitivity of the photoresist 5, thereby directly patterning the slurry coating with the photoresist. In this way, process steps can be saved. For example, the step of configuring adhesives with different viscosities and properties according to the process is omitted. Thereby, the compatibility of the photolithography process in the preparation method is improved. The photosensitivity of the slurry can be directly utilized to pattern the slurry coating in one step. Optionally, the photoresist 5 is an EUV photoresist. Specifically, it can be combined with Figure 1 Step 013 and Fig.14 As shown, the sensitive material slurry is coated on the substrate (silicon wafer). Figure 1 Step 014, Step 015 and Fig.15 , Fig.16After the photolithography process and the heat treatment, the sensitive layer 9 is obtained. That is, the photosensitive property of the photoresist 5 is combined with the heat treatment and the photolithography process to realize the patterning of the slurry coating. In this way, the compatibility of the coating process and the photolithography process is improved, the consistency of the product is improved, and the process of the coating process of the sensitive material is saved.

[0064] According to the preparation method of the sensitive layer 9 of the specific embodiment of the present invention, the sensitive material is dispersed in the photoresist 5 to form a sensitive material slurry, and the slurry coating is patterned by a photolithography process, and then the sensitive layer 9 is obtained by heat treatment. In this way, the compatibility of the photolithography process in the preparation method of the sensitive layer 9 of the present invention can be improved, the consistency of the product is improved, the process flow is reduced, and the production cost is reduced. The graphic accuracy of the product is improved, a porous film structure with a larger specific surface area can be obtained, and the freedom of graphic design can be improved. Among them, the photolithography process may include the use of uniform coating, exposure, and development technology. But it is not limited to this. In order to better understand the technical solution of the present invention, the photolithography process in the present invention is similar to the application of the photolithography process in semiconductors. Here, the sensitive material can be a gas sensitive material, such as a material sensitive to CO, formaldehyde gas, etc.

[0065] According to some embodiments of the present invention, in the sensitive material slurry, the material-liquid ratio of the sensitive material and the photoresist 5 satisfies: sensitive material: photoresist 5 = 2g-5.5g: 8ml-10ml. In this way, the sensitive material can be fully dispersed in the photoresist 5, and the sensitive slurry can have suitable viscosity and adhesiveness, avoiding the need to reconfigure adhesives with different viscosities and properties according to the process. Optionally, the material-liquid ratio of the sensitive material and the photoresist 5 satisfies: sensitive material: photoresist 5 is 1g:4ml, 2g:8.5ml, 2g:9ml, 2g:9.5ml, 1g:5ml, 3g:4ml, 3g:8.5ml, 1g:3ml, 3g:9.5ml, 3g:10ml, 1g:2ml, 4g:8.5ml, 4g:9ml, 4g:9.5ml, 2g:5ml, 5g:8ml, 5g:8.5ml, 5g:9ml, 5g:9.5ml, 1g:2ml, 5.5g:8ml, 5.5g:8.5ml, 5.5g:9ml, 5.5g:9.5ml or 5.5g:10ml, but is not limited to this.

[0066] According to some other embodiments of the present invention, in the sensitive material slurry, the liquid ratio of the sensitive material and the photoresist 5 satisfies: sensitive material: photoresist 5 = 1g: 2.5ml~4ml. With such a configuration, the viscosity and adhesiveness of the sensitive slurry are more suitable, avoiding the need to reconfigure adhesives with different viscosities and properties according to the process. The process compatibility of the photolithography process in the preparation method of the sensitive layer 9 of the present invention is further improved, and the production cost is reduced. The process compatibility is improved, the process flow is reduced, and the graphic accuracy and consistency of the product are improved. Optionally, the liquid ratio of the sensitive material and the photoresist 5 satisfies: sensitive material: photoresist 5 is 1g: 2.5ml, 1g: 3ml, 1g: 3.5ml, 1g: 4ml, but is not limited thereto.

[0067] According to some other embodiments of the present invention, in the sensitive material slurry, the material-liquid ratio of the sensitive material and the photoresist 5 satisfies: sensitive material: photoresist 5 = 1 g: 3 ml. With such a configuration, the viscosity and adhesiveness of the sensitive slurry are more suitable.

[0068] According to some embodiments of the present invention, the photolithography process includes: pre-baking, exposure and development, and hardening. In this way, the slurry coating is patterned.

[0069] According to some other embodiments of the present invention, the hardening temperature is 200°C to 300°C, and the hardening time is 30min to 60min. In this way, the photoresist in the functional area can be carbonized within the temperature and time range, thereby improving the adhesion between the sensitive material slurry and the micro-hotplate.

[0070] According to some embodiments of the present invention, the heat treatment is high temperature calcination at 400° C. to 600° C. for 1 h to 3 h. In this way, the temperature and time of high temperature calcination are suitable, which is conducive to removing organic matter in the photoresist and improving the conductivity of the sensitive layer 9.

[0071] According to some embodiments of the present invention, the sensitive material includes: SnO2 and / or W2O3. In this way, SnO2 and / or W2O3 as the substrate of the sensitive material have high sensitivity to gas, thereby ensuring the sensitivity of the MEMS gas sensor 100 to gas.

[0072] According to some embodiments of the present invention, the sensitive material further comprises: palladium oxide and / or palladium chloride. In this way, adding palladium oxide or palladium chloride as a catalyst into the dispersion system of the sensitive material photoresist can improve the selectivity of the metal oxide catalyst substrate (SnO2 and / or W2O3) to special gases.

[0073] According to some other embodiments of the present invention, the weight ratio of palladium oxide or palladium chloride to SnO2 and / or W2O3 satisfies: 1:0.005 to 1:0.05. In this way, the weight ratio of palladium oxide or palladium chloride to SnO2 and / or W2O3 is appropriate, which can ensure the sensitivity of the sensitive layer 9 and the selectivity to special gases.

[0074] According to some embodiments of the present invention, the sensitive material further comprises: glass powder. In this configuration, by adding glass powder, the bonding performance between the sensitive layer 9 and the micro-hotplate can be improved, thereby improving the reliability of the sensor structure.

[0075] According to other embodiments of the present invention, the weight ratio of SnO2 and / or W2O3 to glass powder satisfies: 1-2:0.1-0.2. In this way, the amount of glass powder added to the sensitive material is appropriate, which can not only improve the bonding performance between the sensitive layer 9 and the micro-hotplate, but also ensure the sensitive performance of the sensitive layer 9.

[0076] According to some other embodiments of the present invention, the substrate is a wafer. In this configuration, the sensitive material slurry can be coated on the wafer to prepare a gas sensor.

[0077] According to an embodiment of the second aspect of the present invention, the present invention provides a sensitive layer 9, and the sensitive layer 9 is prepared by using the preparation method according to an embodiment of the first aspect of the present invention.

[0078] The sensitive layer 9 according to the specific embodiment of the present invention has a simple preparation process and high sensitivity.

[0079] According to some embodiments of the present invention, the thickness of the sensitive layer 9 is d1, wherein d1 satisfies: 5um≤d1≤15um. In this way, if d1 is less than 5um, the thickness of the sensitive layer 9 is small, and the conductivity of the sensitive layer 9 may be poor. If d1 is greater than 15um, the thickness of the sensitive layer 9 is relatively large, and the reliability of the sensitive layer 9 may be poor, and it is easy to crack and fall off. By setting d1 to satisfy 5um≤d1≤15um, the reliability of the sensitive layer 9 is high and the conductivity is good.

[0080] According to an embodiment of the third aspect of the present invention, the present invention provides a method for preparing a MEMS gas sensor 100, comprising the following steps: dispersing a sensitive material into a photoresist 5 to obtain a sensitive material slurry;

[0081] The sensitive material slurry is coated on the wafer to form a slurry coating, and the slurry coating is patterned using a photolithography process.

[0082] After back cavity etching and heat treatment, the MEMS gas sensor 100 is obtained.

[0083] According to the method for preparing the MEMS gas sensor 100 of the specific embodiment of the present invention, the sensitive material is dispersed in the photoresist 5 to form a sensitive material slurry, and the slurry layer is patterned by a photolithography process, and then back cavity etching and heat treatment are performed to obtain the MEMS gas sensor 100. In this way, the compatibility of the photolithography process in the method for preparing the MEMS gas sensor 100 of the present invention can be improved, the consistency of the product is improved, the process flow is reduced, the production cost of the MEMS gas sensor 100 is reduced, and the MEMS gas sensor 100 is ensured to have excellent gas sensitivity.

[0084] According to an embodiment of the fourth aspect of the present invention, Fig.18 As shown, the present invention provides a MEMS gas sensor, comprising: a micro-hotplate and a sensitive layer 9, wherein the micro-hotplate has an active area, and the sensitive layer 9 is formed in the active area. The sensitive layer 9 is prepared by the preparation method according to the first embodiment of the present invention, or the sensitive layer 9 is the sensitive layer 9 according to the second embodiment of the present invention.

[0085] According to the MEMS gas sensor 100 of the specific embodiment of the present invention, the sensitive layer 9 is formed in the active area by a photolithography process with good compatibility, which improves the patterning accuracy and consistency of the product and can improve the patterning accuracy and design freedom.

[0086] According to other embodiments of the present invention, Fig.18 The micro hot plate includes a substrate 1, a first support layer 2 (silicon oxide support layer), a second support layer 3 (Si3N4 support layer), a heating electrode 4 (Pt electrode), an isolation layer 6 (silicon nitride isolation layer) and a test electrode 7 (Pt interdigital electrode). The first support layer 2 is arranged on the surfaces of both sides of the substrate 1 in the thickness direction, and the second support layer 3, the heating electrode 4, the isolation layer 6 and the test electrode 7 are sequentially stacked on one side of the first support layer 2 in the thickness direction away from the substrate 1 in the direction away from the substrate 1. In this way, a complete circuit structure of the MEMS gas sensor 100 is formed. Optionally, the substrate 1 is a substrate of silicon material.

[0087] According to some other embodiments of the present invention, the thickness of the substrate 1 is d2, wherein d2 satisfies: 350um≤d2≤650um. In this way, the thickness of the substrate 1 is appropriate and can provide a circuit substrate for the MEMS gas sensor 100.

[0088] According to some other embodiments of the present invention, the thickness of the first support layer 2 is d3, wherein d3 satisfies: 1 um≤d3≤2.5 um. In this way, the thickness of the first support layer 2 is appropriate and can provide support performance for the MEMS gas sensor 100.

[0089] According to some other embodiments of the present invention, the stress of the first support layer 2 is P1, wherein P1 satisfies: -150Mpa≤P1≤-400Mpa. In this way, the stress of the first support layer 2 is appropriate, so that the substrate 1 and the first support layer 2 can be fully combined.

[0090] According to some other embodiments of the present invention, the thickness of the second support layer 3 (Si3N4 silicon support layer) is d4, wherein d4 satisfies: 100nm≤d4≤300nm. In this way, the thickness of the second support layer 3 is appropriate and the supporting force is strong.

[0091] According to some other embodiments of the present invention, the stress of the second support layer 3 (Si3N4 silicon support layer) is P2, wherein P2 satisfies: 150Mpa≤P2≤400Mpa. In this way, the stress of the second support layer 3 is appropriate, so that the Si3N4 silicon support layer can be fully combined with the first support layer 2.

[0092] According to some other embodiments of the present invention, the thickness of the heating electrode 4 is d5, wherein d5 satisfies: 150nm≤d5≤300nm. In this way, the thickness of the heating electrode 4 is appropriate, and the height of the formed heating electrode 4 is appropriate.

[0093] According to some other embodiments of the present invention, the thickness of the isolation layer 6 is d6, wherein d6 satisfies: 100nm≤d6≤200nm. In this way, the thickness of the isolation layer 6 is appropriate and the isolation effect of the isolation layer 6 is good.

[0094] According to some other embodiments of the present invention, the thickness of the test electrode 7 is d7, wherein d7 satisfies: 150nm≤d7≤400nm. In this way, the thickness of the test electrode 7 is appropriate, and the height of the formed test electrode 7 is appropriate.

[0095] Specifically, combined Figure 1-Figure 16 The coating process of the sensitive material of the MEMS gas sensor 100 (including the preparation process of the micro-hotplate) includes the following steps:

[0096] Step 01: Combining Figure 1 Step 01 and Figure 2 , a silicon oxide film is formed by thermal oxidation on the surface of the substrate 1, which is the first support layer 2, and the thickness of the substrate 1 is 350um to 650um; the thickness of the first support layer 2 is 1um to 2.5um, and the stress of the first support layer 2 is -150Mpa to -400Mpa;

[0097] Step 02: Combining Figure 1 Step 02 and Figure 3On the basis of step 01, a layer of Si3N4 is deposited on the surface of the silicon oxide film by using a low pressure chemical vapor deposition [LPCVD (Low Pressure Chemical Vapor Deposition)] method, a plasma enhanced chemical vapor deposition [PECVD (Plasma Enhanced Chemical Vapor Deposition)] process, or a physical vapor deposition [PVD (Physical Vapor Deposition)] process, the second supporting layer 3 is formed, and the thickness of the second supporting layer 3 is 100nm-300nm, and the stress of the second supporting layer 3 is 150Mpa-400Mpa;

[0098] Step 03: Combining Figure 1 Step 03 and Figure 4 , perform photoresist 5 uniformly (development) on the basis of step 02, control the thickness of photoresist 5 to 0.5um-2um, set the hardening temperature to 75℃-120℃, and obtain the pattern after exposure and development;

[0099] Step 04: Combining Figure 1 Step 04 and Figure 5 , on the basis of step 03, electron beam induced deposition [EBID (Electron Beam-induced Deposition)] or PVD coating, or atomic layer deposition [ALD (Atomic Layer Deposition)] is used to deposit Pt thin film (to obtain Pt heating electrode 4), and the deposition thickness is 150nm ~ 300nm; in order to improve the adhesion between the Pt thin film and the substrate, 20nm ~ 50nm of other thin film materials can be plated on the substrate before plating Pt for primer, including Ni, Al, Ti, Cr, etc., but not limited to these;

[0100] Step 05: Combining Figure 1 Step 05 and Figure 6 , based on step 04, the photoresist 5 is removed (liftoff the photoresist 5), the photoresist 5 and the Pt film thereon are stripped off, and the Pt heating electrode 4 pattern and the pad (PAD) position are obtained;

[0101] Step 06: Combining Figure 1 Step 06 and Figure 7 , on the basis of step 05, depositing Si3N4 or SiO2 to form an isolation layer 6 (i.e., Si3N4 / SiO2 isolation layer), the thickness of the Si3N4 / SiO2 isolation layer is 100nm to 200nm;

[0102] Step 07: Optionally, combine Figure 1 Step 07 and Figure 8 , based on step 06, repeat step 03 to perform coating development;

[0103] Step 08: Combining Figure 1 Step 08 and Fig. 9 , based on step 07, PAD window opening (dielectric etching) is performed, and the window opening process can be dry etching or wet etching; the Si3N4 / SiO2 isolation layer deposited on the PAD is removed;

[0104] Step 09: Combining Figure 1 Step 09 and Fig.10 , based on step 08, removing the photoresist 5;

[0105] Step 010: Combine Figure 1 Step 010 and Fig.11 , based on step 09, repeat step 03 to perform coating development;

[0106] Step 011: Combine Figure 1 Step 011 and Fig.12 On the basis of step 010, a Pt layer is sputtered. For example, PVD coating can be used, and the coating thickness is 150nm to 400nm. Similar to step 04, in order to improve the adhesion between the Pt film and the substrate, 20nm to 50nm of other thin film materials can be plated on the substrate for primer before plating Pt. Other thin film materials include Ni, Al, Ti, Cr, etc., but are not limited thereto;

[0107] Step 012: Combine Figure 1 Step 012 and Fig.13 On the basis of step 011, on the basis of step 012, the photoresist 5 is stripped (lifted off the photoresist 5) to obtain a Pt interdigital electrode (ie, a test electrode 7);

[0108] Step 013: Combine Figure 1 Step 013 and Fig.14 On the basis of step 012, firstly, the configured photoresist 8 containing sensitive materials, i.e., the sensitive material slurry, is coated on the active area obtained in step 012 by spin coating or spray coating (the photoresist 8 containing sensitive materials is coated by coating and developing), and the thickness of the photoresist 8 containing sensitive materials is controlled to be 5um to 15um according to the process adjustment, and the pre-baking temperature is 75°C to 120°C, and the time is 1min to 5min; after exposure and development, the photoresist 88 containing sensitive materials is left on the interdigital electrodes; then, a hot plate is used for hardening, and the hardening temperature is 200°C to 300°C, and the hardening time is 30min to 60min. At the above temperature, the photoresist 8 containing sensitive materials in the functional area can be carbonized to improve the adhesion between the sensitive material and the micro-hot plate;

[0109] Step 014: Combine Figure 1 Step 014 and Fig.15 On the basis of step 013, performing photoresist development and back cavity etching, wherein the back cavity etching adopts a dry etching process;

[0110] Step 015: Combine Figure 1 Step 015 and Fig.16 The wafer obtained in step 014 is placed in a muffle furnace for high-temperature calcination at a temperature of 400° C. to 600° C. The calcination time is 1 hour to 24 hours. This step can further remove organic matter in the photoresist 5 and improve the conductive performance of the sensitive layer 9.

[0111] Among them, step 012 and step 013 can be exchanged, or the silicon cup can be etched first and then the sensitive material can be coated. However, in the implementation process after the exchange step, the suspended film structure is processed first. Adding operating steps in the subsequent process increases the risk of fragmentation, which is not conducive to yield assurance in the mass production process.

[0112] According to an embodiment of the fifth aspect of the present invention, the present invention provides an air conditioner, comprising a MEMS gas sensor 100 prepared by the preparation method according to an embodiment of the third aspect of the present invention, or comprising a MEMS gas sensor 100 according to an embodiment of the fourth aspect of the present invention.

[0113] According to the air conditioner of the specific embodiment of the present invention, the MEMS gas sensor 100 is sensitive to gas, so that the air conditioner has strong sensitivity to some gases (CO, formaldehyde gas, etc.) in the air and high purification efficiency.

[0114] The present invention is further described in detail below by taking several specific embodiments as examples and in conjunction with the accompanying drawings.

[0115] Example 1

[0116] A preparation process of a MEMS gas sensor includes the following steps:

[0117] Step 01: Combining Figure 1 Step 01 and Figure 2 The silicon oxide film formed by thermal oxidation on the surface of the substrate is the first support layer, and the thickness of the substrate is 350um; the thickness of the first support layer is 1um, and the stress of the first support layer is -150Mpa;

[0118] Step 02: Combining Figure 1 Step 02 and Figure 3On the basis of step 01, a layer of SiNx is deposited on the surface of the silicon oxide film by using a low pressure chemical vapor deposition [LPCVD (Low Pressure Chemical Vapor Deposition)] method, which is the second supporting layer. The thickness of the second supporting layer is 100 nm, and the stress of the second supporting layer is 150 MPa;

[0119] Step 03: Combine Figure 1 Step 03 and Figure 4 , perform photoresist coating on the basis of step 02, control the thickness of photoresist at 2um, set the hardening temperature at 75°C, and obtain the pattern after exposure and development;

[0120] Step 04: Combining Figure 1 Step 04 and Figure 5 On the basis of step 03, electron beam induced deposition [EBID (Electron Beam-induced Deposition)] is used to deposit Pt thin film with a deposition thickness of 150nm; in order to improve the adhesion between the Pt thin film and the substrate, 20nm of other thin film materials can be plated on the substrate for primer before plating Pt. Here, other thin film materials may include Ni, Al, Ti, Cr, etc., but are not limited to these.

[0121] Step 05: Combining Figure 1 Step 05 and Figure 6 , based on step 04, the photoresist is removed, the photoresist and the Pt film thereon are peeled off, and the Pt heating electrode pattern and the pad (PAD) position are obtained;

[0122] Step 06: Combining Figure 1 Step 06 and Figure 7 , on the basis of step 05, Si3N4 or SiO2 is deposited to form an isolation layer 6 (i.e., Si3N4 / SiO2 isolation layer), the thickness of the Si3N4 / SiO2 isolation layer is 100nm to 200nm;

[0123] Step 07: Optionally, combine Figure 1 Step 07 and Figure 8 , based on step 06, repeat step 03 to perform coating development;

[0124] Step 08: Combining Figure 1 Step 08 and Fig. 9 , based on step 07, PAD windowing is performed, and the windowing process can be performed by dry etching or wet etching; the Si3N4 / SiO2 isolation layer deposited on the PAD is removed;

[0125] Step 09: Combining Figure 1 Step 09 and Fig.10, based on step 08, removing the photoresist;

[0126] Step 010: Combine Figure 1 Step 010 and Fig.11 , based on step 09, repeat step 03 to perform coating development;

[0127] Step 011: Combine Figure 1 Step 011 and Fig.12 On the basis of step 010, a Pt layer is sputtered, and the coating thickness is 150nm. The same as step 4, in order to improve the adhesion between the Pt film and the substrate, 20nm of other thin film materials can be plated on the substrate for primer before plating Pt. Other thin film materials include Ni, Al, Ti, Cr, etc., but are not limited thereto;

[0128] Step 012: Combine Figure 1 Step 012 and Fig.13 , based on step 011, on the basis of step 012, the photoresist is stripped to obtain a Pt interdigital electrode (i.e., a test electrode);

[0129] Step 013: Combine Figure 1 Step 013 and Fig.14 On the basis of step 012, firstly, the configured photoresist containing sensitive materials, i.e., sensitive material slurry, is coated on the active area obtained in step 012 by spin coating or spray coating. According to the process adjustment, the thickness of the photoresist is controlled to be 5um, the pre-baking temperature is 75°C, and the time is 1min. After exposure and development, the photoresist containing sensitive (gas-sensitive) materials is left on the interdigital electrodes, and then a hot plate is used for hardening. The hardening temperature is 200°C and the hardening time is 30min. At the above temperature, the photoresist in the functional area can be carbonized to improve the adhesion between the sensitive material and the substrate.

[0130] Step 014: Combine Figure 1 Step 014 and Fig.15 On the basis of step 013, performing photoresist development and back cavity etching, wherein the back cavity etching adopts a dry etching process;

[0131] Step 015: Combine Figure 1 Step 015 and Fig.16 The wafer obtained in step 014 is placed in a muffle furnace for high-temperature calcination at 400° C. The calcination time is 1 hour. This step can further remove organic matter in the photoresist and improve the conductivity of the sensitive layer. The MEMS gas sensor of the specific embodiment of the present invention is obtained.

[0132] Among them, the raw materials and proportions of the sensitive material slurry are as follows: SnO2: 3g; EUV photoresist: 9ml.

[0133] The manufacturing process of the sensitive material slurry includes the following steps: stirring the raw materials of the above ratio at room temperature for 20 minutes; then ultrasonicating for 60 minutes to obtain the photoresist containing the sensitive material of this embodiment, that is, the sensitive material slurry. According to the above process flow, the above sensitive material slurry is added in step 013.

[0134] Example 2

[0135] Example 2 is basically the same as Example 1, except that the sensitive material contains more palladium oxide than the sensitive material in Example 1. The raw materials and proportions of the above-mentioned sensitive material slurry in this example are as follows: SnO2: 3g; EUV photoresist: 9ml; palladium oxide: 0.045g.

[0136] The manufacturing process of the sensitive material slurry includes the following steps: stirring the raw materials of the above ratio at room temperature for 20 minutes; then ultrasonicating for 60 minutes to obtain the photoresist containing the sensitive material of this embodiment, that is, the sensitive material slurry. The process is carried out according to the process flow of Example 1, and the above sensitive material slurry is added in step 013.

[0137] Example 3

[0138] Example 2 is basically the same as Example 1, except that the sensitive material contains more glass powder (including a mixed material of PbO, SiO2, and TiO2 in equal weight ratio) than that in Example 1.

[0139] The raw materials and proportions of the sensitive material slurry described in this embodiment are as follows: SnO2: 3g; EUV photoresist: 9ml; glass powder: 0.3g.

[0140] The manufacturing process of the sensitive material slurry includes the following steps: stirring the raw materials of the above ratio at room temperature for 20 minutes; then ultrasonicating for 60 minutes to obtain the photoresist containing the sensitive material of this embodiment, that is, the sensitive material slurry. The process is carried out according to the process flow of Example 1, and the above sensitive material slurry is added in step 013.

[0141] Performance Testing

[0142] The MEMS gas sensor obtained in the specific embodiment 1 of the present invention, the MEMS gas sensor obtained in the embodiment 2, and the MEMS gas sensor obtained in the embodiment 3 are placed in a test chamber for gas sensitive response test. Air and 10ppm of CO are circulated into the test chamber with a cycle period of 200s and a gas flow rate of 500sccm to perform a gas sensitive response test on the MEMS gas sensor. The MEMS gas sensor obtained in the embodiment 1, the MEMS gas sensor obtained in the embodiment 2, and the MEMS gas sensor obtained in the embodiment 3 are placed in the above-mentioned test chambers respectively, and the gas sensitive resistance value is measured by the pressure division method and then normalized to obtain the data of the MEMS gas sensor's gas response performance. Specifically, Fig.17 As shown in the figure, from the test results, it can be seen that the MEMS gas sensors obtained in Examples 1 to 3 all respond to CO gas. Among them, the MEMS gas sensor obtained in Example 2 has the best responsiveness, the MEMS gas sensor obtained in Example 1 has the second best responsiveness, and the MEMS gas sensor obtained in Example 3 has a relatively poor responsiveness.

[0143] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

[0144] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for preparing a sensitive layer, characterized in that: The following steps are involved: dispersing the sensitive material into the photoresist to obtain a sensitive material slurry; The sensitive material slurry is coated on a substrate to form a slurry coating, and the slurry coating is patterned by a photolithography process, and then subjected to a heat treatment to obtain a sensitive layer.

2. The preparation method according to claim 1, characterized in that: In the sensitive material slurry, the material-liquid ratio of the sensitive material and the photoresist satisfies: sensitive material: photoresist = 2g~5.5g:8ml~10ml; preferably: 1g:3ml.

3. The preparation method according to claim 1, characterized in that: The photolithography process includes: pre-baking, exposure and development, and hardening.

4. The preparation method according to claim 3, characterized in that: The pre-baking temperature is 75°C to 120°C and the time is 1min to 5min; and / or The film hardening temperature is 200° C. to 300° C., and the film hardening time is 30 min to 60 min.

5. The preparation method according to claim 1, characterized in that: The heat treatment is calcination at 400°C to 600°C, and the calcination time is 1h to 3h.

6. The preparation method according to claim 1, characterized in that: The sensitive material includes: SnO2 and / or W2O3.

7. The preparation method according to claim 6, characterized in that: The sensitive material also includes: PdCl2 and / or PdO; The weight ratio of the PdCl2 and / or PdO to the SnO2 and / or W2O3 satisfies: 1:0.005 to 1:0.

05.

8. The preparation method according to claim 6, characterized in that: The sensitive material further comprises: glass powder; and / or The weight ratio of the SnO2 and / or W2O3 to the glass powder satisfies: 1-2:0.1-0.

2.

9. The preparation method according to any one of claims 1 to 8, characterized in that: The substrate is a wafer.

10. A sensitive layer, characterized in that: The sensitive layer is prepared by the preparation method according to any one of claims 1-9.

11. The sensitive layer according to claim 10, characterized in that The thickness of the sensitive layer is d1, wherein d1 satisfies: 5um≤d1≤15um.

12. A method for preparing a MEMS gas sensor, characterized in that: The following steps are involved: dispersing the sensitive material into the photoresist to obtain a sensitive material slurry; The sensitive material slurry is coated on the wafer to form a slurry coating, and the slurry coating is patterned by a photolithography process. After back cavity etching and heat treatment, a MEMS gas sensor is obtained.

13. A MEMS gas sensor, characterized in that: include: a micro-hotplate having an active area; A sensitive layer, wherein the sensitive layer is formed in the active area, and the sensitive layer is prepared by the preparation method according to any one of claims 1 to 9, or the sensitive layer is the sensitive layer according to claim 10 or 11.

14. The MEMS gas sensor according to claim 13, characterized in that: The micro hot plate comprises: substrate; A first supporting layer, the first supporting layer being disposed on surfaces of both sides of the substrate in a thickness direction; A second supporting layer, a heating electrode, an isolation layer and a testing electrode are stacked in sequence on one side of the first supporting layer in a thickness direction away from the substrate in a direction away from the substrate.

15. The MEMS gas sensor according to claim 14, characterized in that: The thickness of the substrate is d2, wherein d2 satisfies: 350um≤d2≤650um; and / or The thickness of the first supporting layer is d3, wherein d3 satisfies: 1um≤d3≤2.5um; and / or The stress of the first supporting layer is P1, wherein P1 satisfies: -150Mpa≤P1≤-400Mpa; and / or The thickness of the second supporting layer is d4, wherein d4 satisfies: 100nm≤d4≤300nm; and / or The stress of the second supporting layer is P2, wherein P2 satisfies: 150Mpa≤P2≤400Mpa; and / or The thickness of the heating electrode is d5, wherein d5 satisfies: 150nm≤d5≤300nm; and / or The thickness of the isolation layer is d6, wherein d6 satisfies: 100nm≤d6≤200nm; and / or The thickness of the test electrode is d7, wherein d7 satisfies: 150nm≤d7≤400nm.

16. An air conditioner, characterized in that: include: The MEMS gas sensor is prepared by the preparation method according to claim 12, or the MEMS gas sensor according to any one of claims 13-15.

Images