A ceramic-based micro-hotplate and a method for preparing the same

Abstract

The present invention discloses a ceramic-based micro-hotplate and a preparation method thereof. A ceramic film and a heating layer are sequentially formed on the first surface of a silicon substrate. The ceramic film is formed by sintering a set ceramic slurry, and the heating layer is sintered by a set conductive slurry. It can be seen that the ceramic film and the heating layer are both formed by a high-temperature sintering process and have good high-temperature resistance. Therefore, compared with the prior art of forming a heating layer by physical vapor deposition under low-temperature process conditions, the heating layer has better high-temperature resistance and can improve stability and reliability. Moreover, the composition of the ceramic slurry can be adjusted to adjust the thermal conductivity of the ceramic film, thereby avoiding the problem of rapid heat dissipation and reducing heating power consumption. At the same time, the equipment for forming the ceramic film and the heating layer by sintering the corresponding slurry has a lower equipment cost than the chemical vapor deposition and physical vapor deposition equipment, thereby reducing the production cost.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic device manufacturing, and more particularly to a ceramic-based micro-hotplate and a preparation method thereof. Background Art

[0002] Micro hotplate (MHP) based on silicon micromachining technology is a commonly used heating platform in micro-electromechanical systems (MEMS). It has been widely used in micro devices such as micro gas sensors, micro thermal flow meters, micro infrared detectors and barometers. The basic structure of a micro hotplate includes a suspended dielectric film and a resistor bar. When current passes through the resistor bar, part of the Joule heat generated by the resistor is used to heat the micro hotplate, and the other part is dissipated in the suspended structure in the surrounding environment by conduction, convection and radiation, so that the micro hotplate has very small thermal inertia and very high electrothermal coupling efficiency. Milliwatt-level thermal power can quickly heat up the central temperature zone within a few milliseconds. Therefore, the micro hotplate has a very fast thermal response time and low thermal power consumption.

[0003] At present, there are three main processing technologies for silicon-based micro-hotplates prepared based on MEMS technology: back-side bulk silicon processing, front-side bulk silicon processing and surface processing. The main process flow is to use chemical vapor deposition technology to deposit a certain thickness of silicon nitride film and silicon oxide film on the silicon wafer substrate, and then use physical vapor deposition technology to prepare a patterned resistive heating film. Then, a deep silicon etching process is used to etch away the silicon wafer substrate under the silicon nitride and silicon oxide films, so that the silicon nitride and silicon oxide films are suspended in the air, thereby obtaining a micro-hotplate with good thermal insulation performance. However, the resistive heating film prepared by physical vapor deposition of micro-hotplates is usually platinum, tungsten, molybdenum or polycrystalline silicon with a thickness of several hundred nanometers. These materials are thin and have small film grains. When subjected to high-temperature heat treatment (above 600°C), the heating resistance usually undergoes irreversible changes. Moreover, after high-temperature treatment, due to surface oxidation, the resistance will also change when the gold wire ball welding process is usually carried out or when heated to a certain high temperature (above 600°C). For example, the catalytic combustion gas sensor based on silicon-based micro-hotplate, when the sensor is exposed to high-concentration combustible gas, the temperature of the micro-hotplate may reach 700 to 800 degrees Celsius due to the catalytic combustion of the combustible gas. If the micro-hotplate cannot withstand this temperature, the reliability of the micro-hotplate will be a problem, which restricts the use environment of the micro-hotplate and tests the robustness of the product. Secondly, the silicon dioxide material used still has a high thermal conductivity (7W / m·K), which is not conducive to further reducing the power consumption of the micro-hotplate. Furthermore, silicon nitride films, silicon dioxide films and resistive heating films are all prepared by chemical or physical vapor deposition processes, and the required equipment is relatively expensive and the preparation process cost is also high, which is not conducive to further reducing the cost of micro-hotplates.

[0004] From the above description, it can be seen that in the prior art, the micro-hotplate mainly has the following problems: the resistance heating film formed by physical vapor deposition has poor high temperature resistance, resulting in poor product stability and reliability; moreover, the silicon dioxide film has a high thermal conductivity. Due to the rapid heat dissipation, in order to maintain the set operating temperature, a large input power is required, which is not conducive to further reducing the power consumption of the micro-hotplate; at the same time, physical vapor deposition equipment and chemical vapor deposition equipment are expensive, resulting in high production costs, which is not conducive to further reducing the cost of the micro-hotplate. Summary of the invention

[0005] In order to solve the above problems, the technical solution of the present invention provides a ceramic-based micro-hotplate, which has good stability and reliability, simple manufacturing process, low manufacturing cost, and low heating power consumption.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A ceramic-based micro-hotplate, comprising:

[0008] A silicon substrate, wherein the silicon substrate has a first surface and a second surface opposite to each other; the first surface has a central heating area and a peripheral supporting area, and the central heating area has an air insulation cavity penetrating the first surface and the second surface;

[0009] A ceramic film disposed on a first surface of the silicon substrate;

[0010] A heating layer is arranged on the surface of the ceramic film on the side away from the silicon substrate; the heating layer comprises an electrically connected heating electrode and a heating resistor; the heating resistor is located in the central heating area;

[0011] Wherein, the ceramic membrane is formed by sintering a predetermined ceramic slurry formed on the surface of the silicon substrate; and the heating layer is formed by sintering a predetermined conductive slurry formed on the surface of the ceramic membrane.

[0012] Preferably, in the above ceramic-based micro-hotplate, the silicon substrate is a double-sided oxidized, single-sided oxidized or unoxidized single-crystalline silicon wafer, and the crystal orientation of the single-crystalline silicon wafer is 100 or 111;

[0013] Alternatively, the silicon substrate is a double-sided oxidized, single-sided oxidized or unoxidized polycrystalline silicon wafer.

[0014] Preferably, in the above ceramic-based micro-hotplate, the thickness of the silicon substrate is 50 μm-700 μm, including end points.

[0015] Preferably, in the above-mentioned ceramic-based micro-hotplate, the ceramic slurry is a mixed material of glass and ceramic system;

[0016] Or, the ceramic slurry is a glass-ceramic system;

[0017] Alternatively, the ceramic slurry is a single-phase ceramic.

[0018] Preferably, in the above ceramic-based micro-hotplate, the thickness of the ceramic film is 1 μm-50 μm, including end points.

[0019] Preferably, in the above ceramic-based micro-hotplate, the resistivity of the ceramic film is greater than 10 13 Ω·cm.

[0020] Preferably, in the above ceramic-based micro-hotplate, the thermal expansion coefficient of the ceramic film is 0.5×10 -6 / ℃-10×10 -6 / ℃, including the endpoint values.

[0021] Preferably, in the above ceramic-based micro-hotplate, the dielectric constant of the ceramic film is 3-10, including endpoint values.

[0022] Preferably, in the above ceramic-based micro-hotplate, the thermal conductivity of the ceramic film is 0.5 W / (m·K)-10 W / (m·K), including endpoint values.

[0023] Preferably, in the above ceramic-based micro-hotplate, the stress of the ceramic membrane is 100 MPa-1000 MPa, including endpoint values.

[0024] Preferably, in the above ceramic-based micro-hotplate, the ceramic membrane is polished so that the roughness of the ceramic membrane is 0.5 nm-1 μm, including end points.

[0025] Preferably, in the above ceramic-based micro-hotplate, the ceramic film completely covers the first surface, or covers a portion of the first surface.

[0026] Preferably, in the above ceramic-based micro-hotplate, the ceramic-based micro-hotplate comprises multiple layers of the ceramic membranes, the ceramic slurries of the ceramic membranes are different and the thicknesses of the ceramic membranes are different.

[0027] Preferably, in the above-mentioned ceramic-based micro-hotplate, when the ceramic slurry is a mixed material of glass and ceramic system, in the ceramic slurry, the ceramic phase material includes one or more of aluminum oxide ceramics, magnesium oxide ceramics, beryllium oxide ceramics, zirconium oxide ceramics, aluminum nitride ceramics, silicon nitride ceramics, boron nitride ceramics, titanium nitride ceramics, silicon carbide ceramics, titanium carbide ceramics, and boron carbide ceramics, and the glass phase material is an amorphous solid with an irregular structure made of a variety of inorganic minerals as the main raw materials and auxiliary raw materials, and the grains of the ceramic phase material are melted into the amorphous grid of the glass phase material to form the ceramic film.

[0028] Preferably, in the above-mentioned ceramic-based micro-hotplate, when the ceramic slurry is a glass-ceramic system, in the ceramic slurry, the glass-ceramic is a solid composite material containing crystal orientation and glass phase formed by heating base glass;

[0029] The base glass comprises multi-component oxides, and under set conditions, a portion of the base glass forms a regular arrangement, forming a microcrystalline glass phase in the glass phase.

[0030] Preferably, in the above ceramic-based micro-hotplate, the base glass includes one or more of silicate glass, aluminosilicate glass, borate glass, borosilicate glass, fluorosilicate glass, and phosphosilicate glass.

[0031] Preferably, in the above-mentioned ceramic-based micro-hotplate, in the ceramic slurry, the microcrystalline glass phase includes MgO-Al2O3-SiO2 cordierite system, Li2O-Al2O3-SiO2 spodumene system, Li2O-ZnO-Al2O3-SiO2 spodumene system, BaO-Al2O3-SiO2 barium feldspar system, BaO-Al2O3-SiO2-TiO2 barium feldspar system, CaO-Al2O3-Si Any one or more of the O2 calcium feldspar system, CaO-B2O3-SiO2 calcium borosilicate glass system, Li2O-ZnO-MgO-Al2O3-SiO2β quartz system, F-K2O-Na2O-CaO-SiO2 alkali silicate system, FX-MgO-SiO2 fluoroamphibolite system, FX-MgO-Al2O3-SiO2 fluoromica system, and P2O5-Li2O-SiO2 lithium silicate system.

[0032] Preferably, in the above ceramic-based micro-hotplate, when the ceramic slurry is a single-phase ceramic, in the ceramic slurry, the single-phase ceramic is barium tin borate ceramic or barium zirconium borate ceramic.

[0033] Preferably, in the above ceramic-based micro-hotplate, the thickness of the heating electrode is 0.5um-50um, including the end value;

[0034] The material of the heating electrode is any one of Pt, Au, Ag, Cu, Al, Ni, W, Ag / Pd alloy and Pt / Au alloy.

[0035] Preferably, in the above ceramic-based micro-hotplate, the thickness of the heating resistor is 0.5um-50um, including the endpoint values;

[0036] The heating resistor is a resistor trace of a preset shape formed by patterning the conductive film layer;

[0037] The material of the heating resistor is any one of Pt, Au, Ag, Cu, Al, Ni, W, Mo, Ni / Cr alloy, Mo / Mn alloy, Cu / Zn alloy, Ag / Pd alloy, Pt / Au alloy, Fe / Co alloy, RuO2 and SnO2:Sb2O3.

[0038] The present invention also provides a method for preparing a ceramic-based micro-hotplate, using any of the ceramic-based micro-hotplates described above, characterized in that the preparation method comprises:

[0039] A silicon substrate is provided, wherein the silicon substrate has a first surface and a second surface opposite to each other; the first surface has a central heating area and a peripheral supporting area;

[0040] forming a film layer of a predetermined ceramic slurry on the first surface;

[0041] Forming a ceramic film attached to the first surface through a drying and sintering process in sequence;

[0042] forming a conductive film layer of a predetermined conductive slurry on the surface of the ceramic film;

[0043] Forming a heating layer attached to the surface of the ceramic membrane through drying and sintering processes in sequence;

[0044] The second surface is etched to form an air insulation cavity that penetrates the first surface and the second surface corresponding to the central heating area.

[0045] Preferably, in the above preparation method, the process temperature during drying is 40°C-200°C, including endpoint values;

[0046] The process temperature during sintering is 500°C-1400°C, both inclusive.

[0047] It can be known from the above description that in the ceramic-based micro-hotplate and its preparation method provided by the technical solution of the present invention, a ceramic film and a heating layer are sequentially formed on the first surface of the silicon substrate, the ceramic film is formed by sintering a set ceramic slurry, and the heating layer is sintered by a set conductive slurry. It can be seen that the ceramic film and the heating layer are both formed by a high-temperature sintering process and have good high-temperature resistance. Therefore, compared with the existing technology of forming a heating layer by physical vapor deposition under low-temperature process conditions, the heating layer formed by a high-temperature sintering process has better high-temperature resistance and can improve stability and reliability. Moreover, the thermal conductivity of the ceramic film can be adjusted by adjusting the composition of the ceramic slurry to avoid the problem of rapid heat dissipation, thereby reducing the heating power consumption. At the same time, the equipment for forming a ceramic film and a heating layer by sintering the corresponding slurry has a lower equipment cost than the chemical vapor deposition and physical vapor deposition equipment, thereby reducing the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0049] Figure 1 A schematic diagram of the structure of a ceramic-based micro-hotplate provided in an embodiment of the present invention;

[0050] Figure 2 A top view of a ceramic membrane micro-hotplate provided in an embodiment of the present invention;

[0051] Figure 3 A schematic diagram of the structure of another ceramic membrane micro-hotplate provided in an embodiment of the present invention;

[0052] Figure 4 A schematic diagram of the structure of a heating layer provided by an embodiment of the present invention;

[0053] Figure 5 A schematic diagram of a preparation method provided by an embodiment of the present invention;

[0054] Figure 6 A top view of a ceramic-based micro-hotplate provided in an embodiment of the present invention;

[0055] Figure 7 A schematic flow chart of another preparation method provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0056] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] As described in the prior art, the existing micro-hotplate forms a silicon nitride film and a silicon dioxide film in sequence on one side of a silicon wafer substrate by chemical vapor deposition, and then forms a resistance heating film on the silicon dioxide surface by physical vapor deposition.

[0058] The temperature of the physical vapor deposition process is low, and the high-temperature resistance of the formed resistance heating film is poor. The micro-hotplate has a higher temperature in the subsequent gold wire ball welding process or when used as a catalytic combustion gas sensor. The poor high-temperature resistance of the resistance heating film will lead to poor product reliability and stability, affecting product quality.

[0059] Moreover, silicon dioxide has a high thermal conductivity, which will lead to a faster heat dissipation speed. Thus, when the micro-hot plate is used for heating work, such as in a catalytic combustion sensor, the micro-hot plate needs to be used to heat the gas to the combustion temperature. A higher power consumption is required to overcome the heat loss caused by the faster heat dissipation speed, which will result in a higher power consumption when the product is working.

[0060] At the same time, since physical vapor deposition equipment and chemical vapor deposition equipment are relatively expensive, the preparation cost of the product is relatively high.

[0061] The inventors have found that if the mature processing technology of silicon substrates and the excellent electrical, mechanical and thermal properties of ceramic substrates are combined, a ceramic film can be prepared on a silicon substrate to meet the needs of specific products. In other words, by forming a ceramic film on a silicon substrate with a set ceramic slurry, a ceramic substrate with good electrical, mechanical and thermal properties can be formed, and the production cost is low. Then, by setting a conductive slurry on the surface of the ceramic base to form a high-temperature resistant heating layer through sintering, the production cost can be greatly reduced while improving the reliability and stability of the product.

[0062] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0063] refer to Figure 1 , Figure 1 A structural schematic diagram of a ceramic-based micro-hotplate provided in an embodiment of the present invention, the ceramic-based micro-hotplate 10 includes: a silicon substrate 11, the silicon substrate 11 has a first surface 111 and a second surface 112 opposite to each other; the first surface has a central heating area A and a peripheral supporting area B, the central heating area A has an air insulation cavity 15 that runs through the first surface and the second surface; a ceramic film 12 arranged on the first surface of the silicon substrate 11; a heating layer arranged on the side surface of the ceramic film 12 away from the silicon substrate 11; the heating layer includes an electrically connected heating electrode 13 and a heating resistor 14; the heating resistor 14 is located in the central heating area A.

[0064] The heating electrode 13 and the heating resistor 14 can be prepared by the same heating layer formed by the same conductive paste. In other ways, the two can be prepared separately by different resistor pastes and electrode pastes. At this time, the heating electrode 13 is a conductive pad with a certain area, and the external circuit can be electrically connected to the heating electrode 13 by welding methods such as pressure welding, ball welding, and spot welding. The heating electrode 13 mainly provides the micro-hotplate with an external applied electrical signal, and the heating resistor 14 is the main heating element of the micro-hotplate. When the external current is transmitted to the heating resistor through the heating electrode, the heating resistor generates Joule heat, thereby providing a heat source for the micro-hotplate. In order to make the micro-hotplate have a smaller heat capacity and a faster thermal response, the ceramic film in contact with the heating resistor is set as a suspended film, and the silicon in contact with the substrate 11 and the ceramic film is completely etched away by etching technology to form an air insulation cavity 15. Since air has a lower thermal conductivity, it has good insulation. The shape of the heating resistor 14 is appropriately adjusted according to the different shapes of the heating layer. However, no matter what shape it is, the heating electrode 13 and the heating resistor 14 are electrically connected. The heating resistor 14 is set to a specific shape as needed to provide a specific temperature for the operation of the micro-hotplate after heating.

[0065] The ceramic film 12 is formed by sintering a predetermined ceramic slurry formed on the surface of the silicon substrate 11; the heating layer is formed by sintering a predetermined conductive slurry formed on the surface of the ceramic film 12. The heating electrode 13 is used to obtain an electrical signal input from an external circuit to provide a working voltage for the heating resistor.

[0066] The set ceramic slurry is used to form a ceramic film 12 on the surface of the silicon substrate 11 using a thick film printing process. After high-temperature sintering, a dense ceramic film 12 can be formed, which can make the ceramic film 12 stably and reliably combined with the silicon substrate 11, with good bonding force, and dense and hard.

[0067] Compared with the prior art, the ceramic film 12 and the heating layer of the ceramic-based micro-hotplate 10 provided in the embodiment of the present invention are respectively prepared by setting the slurry film-forming and high-temperature sintering. Moreover, after high-temperature heat treatment or heating to a certain high temperature, the heating layer and the ceramic film 12 both have good high-temperature resistance, the resistance value of the heating resistor 14 of the heating layer is stable, and the product is more robust. The ceramic film 12 has a lower thermal conductivity and better thermal insulation performance, which is conducive to further reducing the power consumption of the ceramic-based micro-hotplate 10. Furthermore, the ceramic film 12 and the heating layer can all be formed by thick film printing technology, without using expensive physical vapor deposition or chemical vapor deposition equipment, and using a low-cost film-forming process, which is more conducive to reducing product costs.

[0068] The silicon substrate 11 is a double-sided oxidized, single-sided oxidized or unoxidized single-crystalline silicon wafer, and the crystal orientation of the single-crystalline silicon wafer is 100 or 111, which can make the ceramic film 12 and the silicon substrate 11 have a stable contact effect. Alternatively, the silicon substrate is a double-sided oxidized, single-sided oxidized or unoxidized polycrystalline silicon wafer. Using a single-crystalline silicon wafer or a polycrystalline silicon wafer can make the ceramic film 12 and the silicon substrate 11 have a stable contact effect.

[0069] The thickness of the silicon substrate 11 is 50 μm-700 μm, including the end value. Specifically, the thickness of the silicon substrate 11 can be 100 μm, 200 μm, 300 μm, 50 μm or 600 μm. The silicon substrate 11 with the above thickness value ensures that the ceramic membrane micro-hotplate 10 has a thin thickness while making the ceramic membrane micro-hotplate 10 have good mechanical strength.

[0070] In the embodiments of the present application, the ceramic slurry may be a mixed material of glass and ceramic system; or, the ceramic slurry may be a microcrystalline glass system; or, the ceramic slurry may be a single-phase ceramic.

[0071] When the ceramic slurry is a mixed material of glass and ceramic system, the ceramic slurry includes two crystalline phases, namely glass phase and ceramic phase. Among them, the ceramic phase material includes one or more of aluminum oxide ceramics, magnesium oxide ceramics, beryllium oxide ceramics, zirconium oxide ceramics, aluminum nitride ceramics, silicon nitride ceramics, boron nitride ceramics, titanium nitride ceramics, silicon carbide ceramics, titanium carbide ceramics, and boron carbide ceramics; the glass phase material is a variety of inorganic minerals (including quartz sand, borax, boric acid, barite, barium carbonate, limestone, potassium feldspar, sodium feldspar, soda ash, zinc oxide, bismuth oxide, lead oxide, copper oxide, and chromium oxide, etc.) as the main raw material. The amorphous solid with an irregular structure is made by adding auxiliary raw materials, and has an amorphous grid structure. A small amount of auxiliary raw materials is added to the main raw materials, and the ratio of the main raw materials to the auxiliary raw materials can be set according to the needs. Under high temperature conditions, the grains of the ceramic phase material melt into the amorphous grid of the glass phase material to form the ceramic film.

[0072] When the ceramic slurry is a glass-ceramic system, in the ceramic slurry, the glass-ceramic is a solid composite material formed by heating a base glass and containing a crystal orientation and a glass phase. The base glass includes multi-component oxides, and under set conditions, a portion of the base glass forms a regular arrangement to form a glass-ceramic phase in the glass phase. Specifically, the base glass includes one or more of silicate glass, aluminosilicate glass, borate glass, borosilicate glass, fluorosilicate glass, and phosphosilicate glass.

[0073] When the ceramic slurry is a microcrystalline glass system, the crystal orientation of the ceramic slurry has a microcrystalline glass phase. Optionally, the microcrystalline glass phase includes a MgO-Al2O3-SiO2 cordierite system, a Li2O-Al2O3-SiO2 spodumene system, a Li2O-ZnO-Al2O3-SiO2 spodumene system, a BaO-Al2O3-SiO2 barium feldspar system, a BaO-Al2O3-SiO2-TiO2 barium feldspar system, a CaO-Al2O3-SiO2 calcium ... BaO-Al2O3-SiO2 Any one or more of the O-B2O3-SiO2 calcium borosilicate glass system, Li2O-ZnO-MgO-Al2O3-SiO2β quartz system, F-K2O-Na2O-CaO-SiO2 alkali silicate system, FX-MgO-SiO2 fluoroamphibolite system (X is oxides such as Li, Na, K, Ca, etc.), FX-MgO-Al2O3-SiO2 fluoromica system (X is alkali metal and alkaline earth metal oxides), and P2O5-Li2O-SiO2 lithium silicate system.

[0074] When the ceramic slurry is a single-phase ceramic, in the ceramic slurry, the single-phase ceramic is barium tin borate ceramic or barium zirconium borate ceramic.

[0075] The thickness of the ceramic film 12 can be 1 μm-50 μm, including the end values. Specifically, the thickness of the ceramic film 12 can be 10 μm, 20 μm, 30 μm or 40 μm. The ceramic film 12 with the above thickness is formed on the surface of the silicon substrate 11, while ensuring that the thickness of the ceramic film 12 is relatively thin, the ceramic film 12 can have better electrical, mechanical and thermal properties.

[0076] The resistivity of the ceramic film 12 is greater than 10 13 Ω·cm. The silicon-based ceramic film 10 described in the embodiment of the present invention has a relatively large resistivity and good insulation performance.

[0077] The thermal expansion coefficient of the ceramic membrane 12 is 0.5×10 -6 / ℃-10×10 -6 / °C, including endpoint values. Specifically, the thermal expansion coefficient of the ceramic membrane 12 may be 1×10 -6 / ℃、4×10 -6 / ℃、6×10 -6 / ℃ or 8×10 -6 / °C. A ceramic film 12 with the above thermal expansion coefficient is formed on the surface of the silicon substrate 11, so that the thermal expansion coefficient of the ceramic film 12 is adapted to the thermal expansion coefficient of the silicon substrate 11, which can avoid the problems of the ceramic film warping or breaking caused by the different thermal expansion degrees of the ceramic film 12 and the silicon substrate 11 due to temperature changes, thereby ensuring the reliability and stability of the ceramic film micro-hotplate 10.

[0078] The dielectric constant of the ceramic film 12 is 3-10, including end values. Specifically, the dielectric constant of the ceramic film 12 can be 4, 5, 6, 7 or 9. The ceramic film 12 with the above dielectric constant values ​​is formed on the surface of the silicon substrate 11, so that the ceramic film 12 has excellent electrical properties.

[0079] The thermal conductivity of the ceramic film 12 is 0.5W / (m·K)-10W / (m·K), including endpoint values. Specifically, the thermal conductivity of the ceramic film 12 is 2W / (m·K), 4W / (m·K), 6W / (m·K) or 8W / (m·K). The ceramic film 12 with the above thermal conductivity value is formed on the surface of the silicon substrate 11, so that the ceramic film 12 has excellent thermal properties and a moderate thermal conductivity rate. In this way, when the ceramic film micro-hotplate 10 is used for the micro-hotplate of a catalytic combustion sensor, since the catalytic combustion sensor needs to perform gas detection at the optimal working temperature of the catalyst, the technical solution of the present application can avoid the problem of poor catalyst activity due to excessive heat dissipation, and the need to increase the current for heat compensation. At the same time, it can avoid the problem of slow heat dissipation causing the temperature to exceed the optimal working temperature of the catalyst. It can be seen that the technical solution of the present application can make the silicon-based ceramic membrane have a moderate thermal conductivity rate and excellent thermal properties. When used for a micro-hotplate, the temperature is maintained at the optimal working temperature of the catalyst to avoid the occurrence of excessively high and low temperatures.

[0080] The stress of the ceramic film 12 is 100MPa-1000MPa, including endpoint values. Specifically, the stress of the ceramic film 12 is 200Mpa, 500Mpa, 800Mpa or 900Mpa. The ceramic film 12 with the above stress values ​​is formed on the surface of the silicon substrate 11, so that the ceramic film 12 has excellent mechanical properties, can withstand greater stress, and avoid the problem of warping or falling off of the ceramic film due to stress changes.

[0081] The ceramic film 12 is polished so that the roughness of the ceramic film 12 is 0.5nm-1μm, including the end value. Specifically, the roughness of the ceramic film 12 can be 10nm, 100nm, 500nm or 800nm. The ceramic film 12 with the above roughness value is formed on the surface of the silicon substrate 11, so that the ceramic film 12 has good flatness, which is convenient for making other structures on its surface.

[0082] In the ceramic membrane micro-hotplate provided in the embodiment of the present invention, the ceramic membrane 12 completely covers the first surface, or covers part of the first surface. When the ceramic membrane 12 covers part of the first surface, it has multiple regions, and there are gaps between adjacent regions. By adjusting the size and number of regions divided by the ceramic membrane 12 in the first surface region and the gap distance, the stress of the silicon substrate 11 and the stress of the ceramic membrane 12 are adjusted to match, thereby ensuring the stability and reliability of the ceramic membrane micro-hotplate.

[0083] refer to Figure 2 , Figure 2 A top view of a ceramic membrane micro-hotplate provided in an embodiment of the present invention, Figure 2 In the manner shown in the left figure, the ceramic film 121 completely covers the first surface of the silicon-based substrate 11. Figure 2 In the manner shown in the right figure, the ceramic film 123 partially covers the silicon-based substrate 11. Figure 2 In the manner shown in the middle figure, the ceramic film 122 partially covers the silicon-based substrate 11.

[0084] The ceramic membrane micro-hotplate 10 can be configured to include multiple layers of the ceramic membrane 12, with different ceramic slurries and different thicknesses of the ceramic membrane 12, so that the stress of the silicon substrate 11 and the stress of the ceramic membrane 12 can be better matched to avoid warping of the ceramic-based micro-hotplate.

[0085] refer to Figure 3 , Figure 3 A schematic diagram of the structure of another ceramic membrane micro-hotplate provided in an embodiment of the present invention, Figure 3 In the ceramic membrane micro-hotplate 20 shown, the silicon substrate 21 also has a first surface and a second surface opposite to each other, which is the same as the silicon substrate in the above embodiment. Figure 3 The method shown is Figure 2 The difference between the methods shown is that Figure 3 In the illustrated embodiment, the surface of the silicon substrate 21 has two layers of ceramic films, namely, ceramic film 221 and ceramic film 222. Ceramic film 221 is located on the surface of the silicon substrate 21, and ceramic film 222 is located on the surface of ceramic film 221. It should be noted that the number of layers of ceramic films can be set according to the stress matching requirements, including but not limited to Figure 3 A heating layer is arranged on the surface of the outermost ceramic film 222 , and the heating layer is implemented in the same manner as above, including a heating electrode 23 and a heating resistor 24 .

[0086] Optionally, the thickness of the heating electrode 13 is 0.5um-50um, including end values, such as 10μm, 20μm or 30μm, etc. The material of the heating electrode 13 is any one of Pt, Au, Ag, Cu, Al, Ni, W, Ag / Pd alloy and Pt / Au alloy, including but not limited to the above materials.

[0087] The thickness of the heating resistor 14 is 0.5um-50um, including end values, such as 10μm, 20μm or 30μm. The heating resistor 14 is a resistor trace of a preset shape formed by patterning the conductive film layer. The conductive film layer pattern structure can be as follows: Figure 4 shown.

[0088] refer to Figure 4 , Figure 4 A schematic diagram of the structure of a heating layer provided in an embodiment of the present invention, Figure 4 middle, Figure 4 The heating layer shown in a has a heating resistor 141 and a heating electrode 131, and the heating resistor 141 is a special-shaped curve; Figure 4 The heating layer shown in b has a heating resistor 142 and a heating electrode 132, and the heating resistor 142 is a mosquito coil type curve; Figure 4 The heating layer shown in c has a heating resistor 143 and a heating electrode 133, the heating resistor 143 is a serpentine curve, and the line width of the heating resistor 143 is uniform; Figure 4 The heating layer shown in d has a heating resistor 144 and a heating electrode 134, the heating resistor 144 is a serpentine curve, and the line width of the heating resistor 144 is uneven; Figure 4 e has a heating resistor 144 and a heating electrode 134, and the heating resistor 144 is rectangular. The pattern structure of the heating layer is not limited to Figure 4 The four methods are not limited to one graphic structure, but can also be a combination of multiple graphic structures. For example, a heating layer can include a combination of at least two of the above four methods.

[0089] The shape of the heating resistor can be changed according to the uniformity of the thermal field of the micro-hotplate, the line width of the heating resistor can be controlled, and the resistance value of the heating resistor can be adjusted. Figure 4 In the figure, the line width of the heating resistor 143 is the same, and the resistance value of each line is also the same. However, the line width of the heating resistor 144 is inconsistent, thick in the middle and thin on both sides. The resistance of the line in the middle is smaller than the resistance of the lines on both sides. When the same current passes through, the Joule heat generated by the lines on both sides is greater than the Joule heat generated by the resistance of the middle line. Since the lines on both sides are closer to the edge of the insulation cavity, the heat conduction is higher, resulting in a low temperature of the lines on both sides. Through the variable line width design, the thermal field can be made more uniform. Similarly, the heating resistor 142 of the mosquito coil curve also has a variable line width design.

[0090] The material of the heating resistor 14 is any one of Pt, Au, Ag, Cu, Al, Ni, W, Mo, Ni / Cr alloy, Mo / Mn alloy, Cu / Zn alloy, Ag / Pd alloy, Pt / Au alloy, Fe / Co alloy, RuO2 and SnO2:Sb2O3, including but not limited to the above materials.

[0091] In the embodiment of the present invention, the ceramic film 12 is different from the traditional ceramic film layer that is intended to achieve ferroelectric, piezoelectric or magnetoelectric coupling effects. The ceramic film layer of the traditional ceramic film layer is a functional ceramic that needs to have excellent conversion performance between force and electromagnetism. The ceramic film 12 of the embodiment of the present invention is a structural ceramic that can achieve mechanical parameters such as stress strain and elastic modulus, so that it has reliable and stable adhesion with adjacent film layers.

[0092] Therefore, the ceramic membrane 12 described in the embodiment of the present application is a structural ceramic, and the traditional ceramic membrane layer is a functional ceramic, which is essentially different. The functional ceramics of the silicon substrate are different from the silicon-based ceramic membrane of the present application. Functional ceramics mainly utilize ceramic materials with non-mechanical properties. Such ceramic materials usually have one or more functions, such as electricity, magnetism, light, heat, chemistry and biology, or have coupling functions, such as piezoelectricity, piezomagnetic, thermoelectricity, electro-optics, acousto-optics, magneto-optics, etc. And with the development of semiconductor technology, functional ceramics are deposited on silicon substrates in the form of thin films and metal electrodes are evaporated. The main research and utilization is the functionality of ceramic materials. The ceramic membrane material of the embodiment of the present invention can make the ceramic membrane and the silicon substrate have matching good mechanical properties, and it is not required to have the above-mentioned non-mechanical properties of traditional ceramic membranes.

[0093] There are many types of structural ceramics, but generally structural ceramics are used in an independent single form, and are large-sized structures in terms of dimension. The ceramic membrane in the embodiment of the present invention can combine a microscopic-sized ceramic membrane with a silicon substrate that is easy to micro-process, and can be used in the field of MEMS microheaters.

[0094] As mentioned above, based on the difference from traditional functional ceramics, the ceramic membrane in the embodiment of the present invention can achieve specific mechanical properties and needs to have specific stress and thermal expansion coefficient, while some electrical performance parameters, such as the dielectric constant range is only 3-10. Traditional functional ceramics, such as piezoelectric ceramics and ferroelectric ceramics, usually require the dielectric constant to be as high as possible. A higher dielectric constant will make its functionality better. The dielectric constants of piezoelectric ceramics and ferroelectric ceramics are usually several thousand to tens of thousands. Therefore, the technical solution of the present invention focuses on excellent mechanical properties in the selection of ceramic membrane materials, and the mechanical properties of most functional ceramic materials do not meet the requirements of the technical solution of the present invention. The technical solution of the present invention does not include functional layer ceramic materials with poor mechanical properties. For example, the ceramic membrane in the embodiment of the present invention has certain elasticity and deformation when heated. If piezoelectric materials are used, the intelligent deformation will generate charges at both ends, which will inevitably affect the subsequent application expansion of the ceramic membrane.

[0095] In the technical solution described in the embodiment of the present invention, after a set ceramic slurry is formed on the surface of a silicon substrate through thick film printing technology, a ceramic film with target characteristics can be formed through high-temperature sintering at a set temperature. The ceramic film with target characteristics has excellent resistivity, thermal expansion coefficient, dielectric constant, thermal conductivity and stress characteristics. Its resistivity, thermal expansion coefficient, dielectric constant, thermal conductivity and stress meet the set numerical range, and it has excellent electrical, thermal and mechanical properties, so that the ceramic film micro-hotplate has good stability and reliability.

[0096] Compared with the prior art, the ceramic membrane micro-hotplate provided in the embodiment of the present invention combines the mature micro-machining technology of the silicon substrate with the excellent electrical, mechanical and thermal properties of ceramics, and can form functional circuits on the ceramic membrane and realize micro-structure processing on the silicon substrate. The ceramic membrane micro-hotplate can be used to prepare micro-mechanical systems, micro-opto-mechanical systems, micro-hotplates, micro-fluidic and other micro-structure systems with excellent performance. In addition, the ceramic membrane can be formed by a low-cost thick film printing process, without the need for expensive physical vapor deposition or chemical vapor deposition equipment, which is more conducive to reducing product costs.

[0097] After a set conductive paste is formed on the surface of the ceramic film through thick film printing technology, a heating layer can be formed by high-temperature sintering at a set temperature. Compared with traditional physical vapor deposition, the heating layer in the ceramic-based micro-hotplate of the embodiment of the present invention has better high-temperature resistance, ensuring the stability and reliability of the product. In the heating layer, the heating resistor and the heating electrode can be prepared at the same time using the same conductive paste. In other methods, different resistor pastes and electrode pastes can also be used to prepare them separately. For example, the heating resistor can be prepared by screen printing the resistor paste and sintering at high temperature, and the heating electrode can be prepared by screen printing the electrode paste and sintering at high temperature.

[0098] Based on the ceramic-based micro-hotplate described in the above embodiment, another embodiment of the present invention further provides a preparation method for preparing the ceramic-based micro-hotplate. The preparation method is as follows: Figure 5 As shown, Figure 5 A schematic flow chart of a preparation method provided in an embodiment of the present invention, the preparation method comprising:

[0099] Step S11: providing a silicon substrate, wherein the silicon substrate has a first surface and a second surface opposite to each other; the first surface has a central heating area and a peripheral supporting area.

[0100] The material and thickness of the silicon substrate can refer to the above description and will not be repeated here.

[0101] Step S12: forming a film layer of a predetermined ceramic slurry on the first surface.

[0102] Ceramic slurry is prepared according to the target characteristics of the ceramic membrane required. Ceramic slurry can be composed of ceramic powder and organic carrier. Specifically, there are three ways to realize ceramic powder, one is a mixed material of glass and ceramic system, one is composed of microcrystalline glass system, and one is single-phase ceramic. The realization method of setting the ceramic slurry can refer to the above description, which will not be repeated here.

[0103] The ceramic slurry may be formed into a film on a silicon substrate by any of screen printing, lithography, gravure printing, relief printing, casting, doctor blade coating and spray coating.

[0104] Step S13: forming a ceramic film attached to the first surface through a drying and sintering process in sequence.

[0105] The target characteristics of the ceramic membrane can be referred to the above description, and will not be repeated here. Through high temperature sintering at a set temperature, a ceramic membrane of a certain thickness can be formed on the surface of the silicon substrate, and the ceramic membrane is dense and hard and has good adhesion to the silicon substrate.

[0106] Optionally, the drying temperature is 40°C-200°C, such as 50°C, 80°C, 100°C or 150°C. Using this temperature value for drying can ensure a good drying effect, avoid poor film drying quality caused by too high or too low temperature, affect the subsequent sintering quality, and ensure the reliability and stability of the ceramic membrane.

[0107] Optionally, the sintering temperature is 500°C-1400°C, including endpoint values, such as 550°C, 800°C, 1000°C or 1200°C. Sintering at this temperature value can ensure a good sintering effect, a dense ceramic film, good hardness characteristics, and strong adhesion to the silicon substrate, avoiding poor sintering of the film layer due to excessively high or low temperatures, and ensuring the reliability and stability of the ceramic film. After the set slurry is formed on the surface of the silicon substrate through a thick film printing process, after sintering, a ceramic film with a large thickness, denseness and good adhesion can be formed. The contact surfaces of the ceramic film and the silicon substrate are in stable contact with each other. Compared with expensive physical vapor deposition or chemical vapor deposition equipment, the contact structure between the two is different, the contact structure is more reliable and stable, and the production cost is low.

[0108] After sintering, the preparation method further comprises a grinding and polishing process to make the roughness of the ceramic film be 0.5 nm-1 μm, including end values.

[0109] Step S14: forming a conductive film layer of a predetermined conductive paste on the surface of the ceramic film.

[0110] Step S15: forming a heating layer attached to the surface of the ceramic membrane through drying and sintering processes in sequence.

[0111] A conductive film layer of a conductive slurry can be formed on the surface of the ceramic membrane by a screen printing process, and a heating layer with good adhesion to the ceramic membrane can be obtained by a drying and sintering process. The temperature range of drying and sintering is the same as above. The drying temperature of the ceramic membrane and the heating layer can be the same or different, and the sintering temperature can be the same or different. In this step, after sintering is completed, the roughness of the heating layer can also be made to be 0.5nm-1μm, including the endpoint value, by a grinding and polishing process. The heating layer has a set pattern structure by setting the screen printing screen pattern to form a heating resistor and a heating electrode with a specific structure.

[0112] Step S16: etching the second surface to form an air insulation cavity that penetrates the first surface and the second surface, corresponding to the central heating area.

[0113] The air insulation cavity can be formed by a deep silicon etching process. Specifically, a photoresist layer is formed on the second surface, and the photoresist layer can be formed by a spin coating process. The photoresist layer is patterned and developed to form a photoresist layer with a preset pattern structure, and the photoresist facing the peripheral support area is retained, and the photoresist facing the central heating area is removed. Then, the silicon substrate is etched using the patterned photoresist layer as a mask to form the air insulation cavity, so that the ceramic film in the central heating area is suspended, and finally the photoresist in the edge support area is removed to form a ceramic-based micro-hotplate with good insulation performance. The photoresist can be a positive photoresist or a negative photoresist. The thickness of the photoresist layer is 1μm-30μm, including the end value.

[0114] refer to Figure 6 , Figure 6 A top view of a ceramic-based micro-hotplate provided in an embodiment of the present invention. In the preparation method described in the embodiment of the present invention, multiple ceramic-based micro-hotplates can be prepared simultaneously through a large-size wafer, and then divided into multiple single-grain ceramic-based micro-hotplates through a cutting process. After cutting, each ceramic micro-hotplate has a silicon substrate 11, a ceramic film 12 and a heating layer. Figure 6 As shown, a ceramic film 12 is formed on the wafer. The heating layer pattern on the ceramic film 12 includes multiple sub-regions, each of which includes a heating electrode 13 and a heating resistor 14. After an air insulation cavity is formed in the central heating area of ​​each sub-region, the large-sized wafer is divided into multiple small-sized silicon substrates 11 through a cutting process, and each small-sized silicon substrate 11 corresponds to a sub-region to form a single-grain ceramic-based micro-hotplate.

[0115] refer to Figure 7 , Figure 7 A schematic flow chart of another preparation method provided in an embodiment of the present invention, the preparation method comprising:

[0116] Step S21: providing a silicon substrate and cleaning the silicon substrate.

[0117] The silicon substrate may be a double-sided oxidized single crystal silicon substrate 11 with a 100 crystal orientation, and may be ultrasonically cleaned with acetone for 10 minutes, then ultrasonically cleaned with isopropanol for 5 minutes, then cleaned with deionized water for 5 minutes, and then blown dry with nitrogen.

[0118] Step S22: preparing ceramic slurry, forming a film on the surface of the silicon substrate with the slurry, and then performing a drying process.

[0119] Ceramic powder of appropriate specifications is selected, and an organic carrier is added to prepare a ceramic slurry, which can be printed on the substrate 11 by screen printing and dried at a certain temperature.

[0120] Step S23: placing the dried silicon substrate into a muffle furnace for sintering to form a ceramic film.

[0121] A dense and hard ceramic membrane 12 with a thickness of 10 μm is obtained, and the surface of the ceramic membrane 12 is processed by grinding and polishing so that the surface roughness of the ceramic membrane 12 is controlled at 0.2 μm.

[0122] Step S24: using a conductive paste to form a graphic structure of a heating electrode and a heating resistor on the surface of the ceramic film through a screen printing process.

[0123] The heating electrode and the heating resistor can use the same conductive paste to form a corresponding pattern structure through a single screen printing. In other methods, the heating electrode paste and the heating resistor paste are respectively printed on the ceramic film by screen printing to form a corresponding heating electrode pattern structure and heating resistor pattern structure.

[0124] After the screen printing is completed, drying and sintering are performed to obtain the heating electrode and the heating resistor, and then the heating electrode and the heating resistor are polished so that the surface roughness of the heating electrode and the heating resistor is 100nm.

[0125] Step S25: etching the other side of the silicon substrate to form an air insulation cavity in the central heating area directly facing the heating resistor.

[0126] Photoresist is spin-coated on the back of the substrate, dried on a hot stage, and patterned exposure and patterned development are performed. The silicon dioxide on the back is removed by reactive ion etching technology, and then the silicon unprotected by the photoresist under the ceramic film is etched away by deep silicon etching technology to form an insulating air cavity 15 to obtain a ceramic-based micro-hotplate. The ceramic-based micro-hotplate chip is obtained by cutting technology.

[0127] In the prior art, the materials used to prepare the ceramic film layer have a relatively high sintering temperature. For example, the sintering temperature of zirconium oxide ceramic materials is required to be no less than 1350°C. The relatively high sintering temperature makes it impossible to use silicon wafers as substrates. This is because silicon wafers cannot withstand such a high sintering temperature, which is close to the melting point of silicon wafers (1400°C). Moreover, the stress of the ceramic film layer prepared by traditional ceramic materials cannot match that of silicon wafers (the overall stress is less than 500MPa). At the same time, the ceramic film layer prepared by traditional ceramic materials cannot form a dense ceramic film, which may cause the ceramic substrate to break when the deep silicon etching process is used later.

[0128] In an embodiment of the present invention, a specific ceramic slurry is used to form a silicon-based ceramic film, which has excellent mechanical properties and can have a good adhesion effect with a silicon substrate. Moreover, the sintering temperature of the material for preparing the ceramic film is lower than the melting point of the silicon wafer. For example, for a mixed material of a glass and ceramic system, the sintering temperature is lower than 1200°C, which is suitable for printing and sintering on a silicon wafer. Moreover, by adjusting the composition and shielding of the ceramic slurry, the thermal expansion coefficient of the prepared ceramic film can be matched with that of the silicon wafer, forming a reliable mechanical contact and avoiding warping and falling off problems caused by thermal deformation.

[0129] In order to better illustrate the present invention, some specific examples of the preparation method of ceramic-based micro-hotplate are provided below.

[0130] Example 1

[0131] A double-sided polished and double-sided oxidized 4-inch single crystal silicon wafer with a crystal orientation of 100 is provided, and then ultrasonically cleaned with acetone for 15 minutes, ultrasonically cleaned with isopropyl alcohol for 5 minutes, and then cleaned with deionized water for 5 minutes, and blown dry with nitrogen; ceramic powder of suitable specifications is selected, an organic carrier is added, and a ceramic slurry is configured, which is printed on the wafer by screen printing, and dried at 120°C for 10 minutes; the dried wafer is placed in a muffle furnace, sintered at 1000°C for 30 minutes, and a dense and hard ceramic film with a thickness of 10um is obtained, and the surface of the ceramic film is processed by grinding and polishing, so that the surface roughness of the ceramic film is controlled at 0.2um.

[0132] A serpentine heating resistor array and a heating electrode array with a length and width of 300um×300um are printed on a ceramic film by screen printing, and the film is dried at 120°C for 5min and sintered at 850°C for 15min to obtain a heating electrode and a heating resistor, and then the heating electrode and the heating resistor are polished to make the surface roughness of the heating electrode and the heating resistor 100nm; positive photoresist is spin-coated on the back of the substrate, dried at 100°C for 5min, and patterned exposure and patterned development are performed to obtain an unprotected area of ​​the photoresist with a thickness of 10um and a length and width of 500um×500um, and the silicon dioxide in the unprotected area is removed by reactive ion etching technology, and then the unprotected silicon of the photoresist is etched away by deep silicon etching technology to form an insulating air cavity to obtain a ceramic-based micro-hotplate, and a ceramic-based micro-hotplate chip with a length and width of 1.0mm×1.0mm is obtained by cutting technology.

[0133] Example 2

[0134] A double-sided polished, double-sided unoxidized 6-inch single crystal silicon wafer with a crystal orientation of 100 is provided, and then ultrasonically cleaned with acetone for 10 minutes, ultrasonically cleaned with isopropanol for 10 minutes, and then cleaned with deionized water for 5 minutes, and blown dry with nitrogen; ceramic powder of appropriate specifications is selected, an organic carrier is added, and a ceramic slurry is configured, and the ceramic slurry is formed on the wafer by a casting method, and dried at 150°C for 10 minutes; the dried wafer is placed in a muffle furnace, sintered at 1000°C for 30 minutes, and a dense and hard ceramic film with a thickness of 20um is obtained, and the surface of the ceramic film is processed by grinding and polishing, so that the surface roughness of the ceramic film is controlled at 0.2um.

[0135] A variable line width serpentine heating resistor array and a heating electrode array with a length and width of 400um×400um are printed on a ceramic film by screen printing, dried at 130°C for 5min, and sintered at 900°C for 30min to obtain a heating electrode and a heating resistor, and then the heating electrode and the heating resistor are polished to make the surface roughness of the heating electrode and the heating resistor 50nm; positive photoresist is spin-coated on the back of the substrate, dried at 100°C for 5min, and patterned exposure and patterned development are performed to obtain an unprotected area of ​​the photoresist with a thickness of 15um and a length and width of 500um×500um, and the silicon dioxide in the unprotected area is removed by reactive ion etching technology, and then the unprotected silicon of the photoresist is etched away by deep silicon etching technology to form an insulating air cavity to obtain a ceramic-based micro-hotplate, and a ceramic-based micro-hotplate chip with a length and width of 1.0mm×1.0mm is obtained by cutting technology.

[0136] Example 3

[0137] A double-sided polished, single-sided oxidized 2-inch single-crystalline silicon wafer with a crystal orientation of 100 is provided, and then ultrasonically cleaned with acetone for 10 minutes, ultrasonically cleaned with isopropanol for 10 minutes, and then cleaned with deionized water for 5 minutes, and blown dry with nitrogen; ceramic powder of appropriate specifications is selected, an organic carrier is added, and a ceramic slurry is configured, and the ceramic slurry is formed into a film on the unoxidized side of the wafer by a scraping method, and is dried at 100°C for 10 minutes; the dried wafer is placed in a muffle furnace, sintered at 1200°C for 30 minutes, and a dense and hard ceramic film with a thickness of 6um is obtained, and the surface of the ceramic film is processed by grinding and polishing, so that the surface roughness of the ceramic film is controlled at 0.1um.

[0138] A mosquito coil-shaped heating resistor array and a heating electrode array with a length and width of 500um×500um are printed on a ceramic film by screen printing, and the heating electrodes and heating resistors are obtained. The heating electrodes and heating resistors are then polished to make the surface roughness of the heating electrodes and heating resistors 10nm. Negative photoresist is spin-coated on the back of a substrate, dried at 150℃ for 5min, and patterned exposure and patterned development are performed to obtain an unprotected area of ​​the photoresist with a thickness of 25um and a length and width of 700um×700um. The silicon dioxide in the unprotected area is removed by reactive ion etching technology, and then the unprotected silicon of the photoresist is etched away by deep silicon etching technology to form an insulating air cavity to obtain a ceramic-based micro-hotplate. A ceramic-based micro-hotplate chip with a length and width of 1.0mm×1.0mm is obtained by cutting technology.

[0139] Example 4

[0140] A double-sided polished and double-sided oxidized 8-inch single crystal silicon wafer with a crystal orientation of 100 is provided, and then ultrasonically cleaned with acetone for 10 minutes, ultrasonically cleaned with isopropyl alcohol for 5 minutes, and then cleaned with deionized water for 5 minutes, and blown dry with nitrogen; ceramic powder of appropriate specifications is selected, an organic carrier is added, and a ceramic slurry is configured, and the ceramic slurry is formed on the wafer by screen printing, and dried at 150°C for 10 minutes; the dried wafer is placed in a muffle furnace, sintered at 1200°C for 60 minutes, and a dense and hard ceramic film with a thickness of 8um is obtained, and the surface of the ceramic film is processed by grinding and polishing, so that the surface roughness of the ceramic film is controlled at 0.5um.

[0141] A special-shaped heating resistor array and a heating electrode array with a length and width of 500um×500um are printed on a ceramic film by screen printing, and the layers are dried at 150°C for 5min and sintered at 1100°C for 10min to obtain heating electrodes and heating resistors. The heating electrodes and heating resistors are then polished to make the surface roughness of the heating electrodes and heating resistors 100nm. Positive photoresist is spin-coated on the back of the substrate, dried at 150°C for 5min, and patterned exposure and patterned development are performed to obtain an unprotected area of ​​the photoresist with a thickness of 10um and a length and width of 800um×800um. The silicon dioxide in the unprotected area is removed by reactive ion etching technology, and then the unprotected silicon of the photoresist is etched away by deep silicon etching technology to form an insulating air cavity to obtain a ceramic-based micro-hotplate. A ceramic-based micro-hotplate chip with a length and width of 1.5mm×1.5mm is obtained by cutting technology.

[0142] Example 5

[0143] A double-sided polished, double-sided unoxidized 12-inch single crystal silicon wafer with a crystal orientation of 100 is provided, and then ultrasonically cleaned with acetone for 10 minutes, ultrasonically cleaned with isopropyl alcohol for 5 minutes, and then cleaned with deionized water for 5 minutes, and blown dry with nitrogen; ceramic powder of appropriate specifications is selected, an organic carrier is added, and a ceramic slurry is configured, which is divided into four mutually spaced quadrants centered on the center of the wafer, and the ceramic slurry is formed on the wafer by gravure printing, and dried at 150°C for 10 minutes; the dried wafer is placed in a muffle furnace, sintered at 1300°C for 20 minutes, and a dense and hard ceramic film with a thickness of 25um is obtained, and the surface of the ceramic film is processed by grinding and polishing, so that the surface roughness of the ceramic film is controlled at 0.5um.

[0144] A square heating resistor array and a heating electrode array with a length and width of 300um×300um are printed on a ceramic film by screen printing, dried at 130°C for 5min, and sintered at 800°C for 60min to obtain heating electrodes and heating resistors, and then the heating electrodes and heating resistors are polished to make the surface roughness of the heating electrodes and heating resistors 100nm; positive photoresist is spin-coated on the back of the substrate, dried at 150°C for 5min, and patterned exposure and patterned development are performed to obtain an unprotected area of ​​the photoresist with a thickness of 12um and a length and width of 600um×600um, the silicon dioxide in the unprotected area is removed by reactive ion etching technology, and then the unprotected silicon of the photoresist is etched away by deep silicon etching technology to form an insulating air cavity to obtain a ceramic-based micro-hotplate, and a ceramic-based micro-hotplate chip with a length and width of 1.5mm×1.5mm is obtained by cutting technology.

[0145] Example 6

[0146] A double-sided polished and double-sided oxidized 10-inch single crystal silicon wafer with a 111 crystal orientation is provided, and then ultrasonically cleaned with acetone for 10 minutes, ultrasonically cleaned with isopropyl alcohol for 5 minutes, and then cleaned with deionized water for 5 minutes, and blown dry with nitrogen; ceramic powder of appropriate specifications is selected, an organic carrier is added, and a ceramic slurry is configured, which is divided into 16 mutually spaced areas with the center of the wafer as the center, and the ceramic slurry is formed on the wafer by screen printing, and dried at 150°C for 10 minutes; the dried wafer is placed in a muffle furnace, sintered at 1100°C for 20 minutes, and a dense and hard ceramic film with a thickness of 15um is obtained, and the surface of the ceramic film is processed by grinding and polishing, so that the surface roughness of the ceramic film is controlled at 0.8um.

[0147] A rectangular heating resistor array and a heating electrode array with a length and width of 500um×400um are printed on a ceramic film by screen printing, and the film is dried at 150℃ for 5min and sintered at 850℃ for 60min to obtain a heating electrode and a heating resistor. The heating electrode and the heating resistor are then polished to make the surface roughness of the heating electrode and the heating resistor 100nm. Positive photoresist is spin-coated on the back of the substrate, dried at 150℃ for 5min, and patterned exposure and patterned development are performed to obtain an unprotected area of ​​the photoresist with a thickness of 8um and a length and width of 600um×600um. The silicon dioxide in the unprotected area is removed by reactive ion etching technology, and then the unprotected silicon of the photoresist is etched away by deep silicon etching technology to form an insulating air cavity to obtain a ceramic-based micro-hotplate. A ceramic-based micro-hotplate chip with a length and width of 1.2mm×1.2mm is obtained by cutting technology.

[0148] From the above description, it can be seen that the preparation method of the embodiment of the present invention is used to prepare the ceramic-based micro-hotplate described in the above embodiment. It does not require expensive physical vapor deposition equipment and chemical vapor deposition equipment. The ceramic film and the heating layer can be formed through low-cost thick film printing process, drying and sintering process. The production cost is low, and a high-temperature resistant heating layer can be formed, thereby improving the stability and reliability of the product.

[0149] Each embodiment in this specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the preparation method disclosed in the embodiment, since it corresponds to the ceramic-based micro-hotplate disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the corresponding part of the ceramic-based micro-hotplate.

[0150] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A ceramic-based micro-hotplate, characterized in that: The ceramic-based micro-hotplate comprises: A silicon substrate, wherein the silicon substrate has a first surface and a second surface opposite to each other; the first surface has a central heating area and a peripheral supporting area, and the central heating area has an air insulation cavity penetrating the first surface and the second surface; A ceramic film disposed on a first surface of the silicon substrate; A heating layer is arranged on the surface of the ceramic film on the side away from the silicon substrate; the heating layer comprises an electrically connected heating electrode and a heating resistor; the heating resistor is located in the central heating area; Among them, the ceramic membrane is formed by sintering a set ceramic slurry formed on the surface of the silicon substrate; the heating layer is formed by sintering a set conductive slurry formed on the surface of the ceramic membrane; the ceramic-based micro-hotplate includes multiple layers of the ceramic membrane, the ceramic slurries of the ceramic membranes are different and the thicknesses of the ceramic membranes are different; the ceramic membrane completely covers the first surface, or covers part of the first surface.

2. The ceramic-based micro-hotplate according to claim 1, characterized in that: The silicon substrate is a double-sided oxidized, single-sided oxidized or unoxidized single-crystalline silicon wafer, and the crystal orientation of the single-crystalline silicon wafer is 100 or 111; Alternatively, the silicon substrate is a double-sided oxidized, single-sided oxidized or unoxidized polycrystalline silicon wafer.

3. The ceramic-based micro-hotplate according to claim 1, characterized in that: The thickness of the silicon substrate is 50 μm-700 μm, including end points.

4. The ceramic-based micro-hotplate according to claim 1, characterized in that: The ceramic slurry is a mixed material of glass and ceramic system; Or, the ceramic slurry is a glass-ceramic system; Alternatively, the ceramic slurry is a single-phase ceramic.

5. The ceramic-based micro-hotplate according to claim 1, characterized in that: The ceramic film has a thickness of 1 μm to 50 μm, both inclusive.

6. The ceramic-based micro-hotplate according to claim 1, characterized in that: The resistivity of the ceramic film is greater than 10 13 Ω·cm.

7. The ceramic-based micro-hotplate according to claim 1, characterized in that: The thermal expansion coefficient of the ceramic membrane is 0.5×10 -6 / ℃-10×10 -6 / ℃, including the endpoint values.

8. The ceramic-based micro-hotplate according to claim 1, characterized in that: The dielectric constant of the ceramic film is 3-10, including endpoint values.

9. The ceramic-based micro-hotplate according to claim 1, characterized in that: The thermal conductivity of the ceramic film is 0.5 W / (m·K)-10 W / (m·K), including endpoint values.

10. The ceramic-based micro-hotplate according to claim 1, characterized in that: The stress of the ceramic membrane is 100 MPa-1000 MPa, including endpoint values.

11. The ceramic-based micro-hotplate according to claim 1, characterized in that: The ceramic membrane is polished so that the roughness of the ceramic membrane is 0.5nm-1μm, including end points.

12. The ceramic-based micro-hotplate according to claim 4, characterized in that: When the ceramic slurry is a mixed material of glass and ceramic system, in the ceramic slurry, the ceramic phase material includes one or more of aluminum oxide ceramics, magnesium oxide ceramics, beryllium oxide ceramics, zirconium oxide ceramics, aluminum nitride ceramics, silicon nitride ceramics, boron nitride ceramics, titanium nitride ceramics, silicon carbide ceramics, titanium carbide ceramics, and boron carbide ceramics; the glass phase material is an amorphous solid with an irregular structure made of a variety of inorganic minerals as main raw materials and auxiliary raw materials; the grains of the ceramic phase material melt into the amorphous grid of the glass phase material to form the ceramic film.

13. The ceramic-based micro-hotplate according to claim 4, characterized in that: When the ceramic slurry is a glass-ceramic system, in the ceramic slurry, the glass-ceramic is a solid composite material formed by heating a base glass and containing a crystal orientation and a glass phase; The base glass comprises multi-component oxides, and under set conditions, a portion of the base glass forms a regular arrangement, forming a microcrystalline glass phase in the glass phase.

14. The ceramic-based micro-hotplate according to claim 13, characterized in that: The basic glass includes one or more of silicate glass, aluminosilicate glass, borate glass, borosilicate glass, fluorosilicate glass, and phosphosilicate glass.

15. The ceramic-based micro-hotplate according to claim 13, characterized in that: In the ceramic slurry, the microcrystalline glass phase includes any one or more of the MgO-Al2O3-SiO2 cordierite system, Li2O-Al2O3-SiO2 spodumene system, Li2O-ZnO-Al2O3-SiO2 spodumene system, BaO-Al2O3-SiO2 barium feldspar system, BaO-Al2O3-SiO2-TiO2 barium feldspar system, CaO-Al2O3-SiO2 calcium feldspar system, CaO-B2O3-SiO2 calcium borosilicate glass system, Li2O-ZnO-MgO-Al2O3-SiO2β-quartz system, F-K2O-Na2O-CaO-SiO2 silicate calcium system, FX-MgO-SiO2 fluoride amphibole system, FX-MgO-Al2O3-SiO2 fluorine mica system, and P2O5-Li2O-SiO2 lithium silicate system.

16. The ceramic-based micro-hotplate according to claim 4, characterized in that: When the ceramic slurry is a single-phase ceramic, in the ceramic slurry, the single-phase ceramic is barium tin borate ceramic or barium zirconium borate ceramic.

17. The ceramic-based micro-hotplate according to claim 1, characterized in that: The thickness of the heating electrode is 0.5um-50um, including the end value; The material of the heating electrode is any one of Pt, Au, Ag, Cu, Al, Ni, W, Ag / Pd alloy and Pt / Au alloy.

18. The ceramic-based micro-hotplate according to claim 1, characterized in that: The thickness of the heating resistor is 0.5um-50um, including the endpoint value; The heating resistor is a resistor trace of a preset shape formed by patterning the conductive film layer; The material of the heating resistor is any one of Pt, Au, Ag, Cu, Al, Ni, W, Mo, Ni / Cr alloy, Mo / Mn alloy, Cu / Zn alloy, Ag / Pd alloy, Pt / Au alloy, Fe / Co alloy, RuO2 and SnO2:Sb2O3.

19. A method for preparing a ceramic-based micro-hotplate, for preparing the ceramic-based micro-hotplate according to any one of claims 1 to 18, characterized in that: The preparation method comprises: A silicon substrate is provided, wherein the silicon substrate has a first surface and a second surface opposite to each other; the first surface has a central heating area and a peripheral supporting area; forming a film layer of a predetermined ceramic slurry on the first surface; Forming a ceramic film attached to the first surface through a drying and sintering process in sequence; forming a conductive film layer of a predetermined conductive slurry on the surface of the ceramic film; Forming a heating layer attached to the surface of the ceramic membrane through drying and sintering processes in sequence; Etching the second surface to form an air insulation cavity that penetrates the first surface and the second surface, corresponding to the central heating area; Wherein, the ceramic-based micro-hotplate comprises multiple layers of the ceramic membranes, the ceramic slurries of the ceramic membranes are different and the thicknesses of the ceramic membranes are different; the ceramic membranes completely cover the first surface or partially cover the first surface.

20. The preparation method according to claim 19, characterized in that: The process temperature during drying is 40°C-200°C, including the endpoint values; The process temperature during sintering is 500°C-1400°C, both inclusive.

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