High-sensitivity MEMS hygrometer and manufacturing method thereof

Abstract

The invention provides a high-sensitivity MEMS (Micro Electro Mechanical System) hygrometer and a manufacturing method thereof, and relates to the technical field of micro electro mechanical systems and semiconductor chip manufacturing processes. The hygrometer comprises a supporting substrate layer, an insulating layer, a metal shielding layer, a first passivation layer, a dielectric layer, an electrode layer, a second passivation layer and a sensing layer, wherein the supporting substrate layer, the insulating layer, the metal shielding layer, the first passivation layer, the dielectric layer, the electrode layer and the second passivation layer are sequentially stacked, and the sensing layer is filled in the dielectric layer and the electrode layer and covers the first passivation layer, the dielectric layer, the electrode layer and the second passivation layer. And the sensing layer is filled in a gap between the dielectric layer and the electrode layer through a humidity sensing material and is used for sensing humidity. The metal shielding layer is arranged below the electrode layer, stray capacitance interference below the metal shielding layer is isolated, the space between the metal shielding layer and the electrode layer is filled with the humidity sensitive material to form an additional humidity sensing layer, stray capacitance in the area is converted into sensing capacitance, and the sensitivity of the sensor is greatly improved. The technology and materials involved in the invention are common technologies and materials in the CMOS technology, and the compatibility to the CMOS technology is high.

Description

Technical Field

[0001] The invention relates to the technical field of micro-electromechanical systems and semiconductor chip manufacturing processes, and in particular to a high-sensitivity MEMS hygrometer and a manufacturing method thereof. Background Art

[0002] In addition to daily applications such as air conditioners and humidifiers, humidity sensors are also widely used in industrial process control, medicine, food production, agriculture, meteorological monitoring and other fields. Compared with existing infrared humidity sensors, electronic humidity sensors are cheaper, lighter and smaller. Electronic humidity sensors can be divided into resistive and capacitive types. Among them, capacitive humidity sensors have the characteristics of simple structure, wide detection range, high reliability and high precision, so they are widely used.

[0003] Capacitive humidity sensors respond to changes in humidity by changing the relative dielectric constant of the sensing layer (e.g., polymer film) after water vapor absorption. Generally, based on the structure of the capacitor, they can be further divided into a planar interdigitated electrode capacitor structure and a vertical parallel plate capacitor structure. In the vertical parallel plate capacitor structure, there is a row of holes or parallel stripes on the upper plate to allow water molecules in the air to reach the sensing material below. This structure avoids the parasitic capacitance interference of the substrate and the air, but leads to a longer water vapor diffusion path. Therefore, the vertical parallel plate capacitor structure has a higher sensitivity but a longer response time. In the planar interdigitated electrode capacitor structure, the positive and negative plates are on the same horizontal plane, and the humidity sensing material is filled between the interdigitated electrodes and directly in contact with the external environment. Therefore, it has a larger humidity sensing area and a shorter water vapor diffusion, and a faster response speed, but it will be affected by parasitic capacitance interference, resulting in low sensitivity.

[0004] Based on this, the present invention is proposed. Summary of the invention

[0005] The object of the present invention is to provide a high-sensitivity MEMS hygrometer and a manufacturing method thereof, which are compatible with CMOS technology, have low manufacturing costs, and the hygrometer has high sensitivity.

[0006] To achieve the above object, the present invention provides the following technical solutions: In a first aspect, the present invention provides a method for manufacturing a high-sensitivity MEMS hygrometer, comprising the following steps: Step 1: preparing a supporting base layer, an insulating layer, a metal shielding layer and a first passivation layer: preparing a supporting base layer having an insulating layer, forming a metal shielding layer on the insulating layer of the supporting base layer, and forming a thin passivation layer on the surface of the metal shielding layer as the first passivation layer; Step 2: Making a dielectric layer and an electrode layer: forming a dielectric layer on the first passivation layer, and then making an electrode layer; Step 3: etching the dielectric layer, and then forming a thin passivation layer as a second passivation layer on the surface of the exposed electrode layer; Step 4: Coating a moisture-sensitive material on the second passivation layer of the electrode layer, wherein the moisture-sensitive material is filled inside the dielectric layer and inside and above the second passivation layer to obtain the moisture meter.

[0007] The present invention provides a preferred solution, in step 1, the metal shielding layer is formed by sputtering or electroplating, the metal shielding layer does not constitute a loop, and one end of the metal shielding layer is connected to a metal wire and grounded.

[0008] The present invention provides a preferred solution, in step 1, the first passivation layer on the surface of the metal shielding layer is formed by depositing a passivation layer or in-situ oxidation of the metal; and / or, the second passivation layer on the surface of the electrode layer is formed by depositing a passivation layer or in-situ oxidation of the metal.

[0009] The present invention provides a preferred solution, in step 2, the electrode layer is manufactured by one of the following methods: the first method is to sputter a layer of metal or semiconductor material on the dielectric layer, and then etch to form the electrode layer; the second method is to form the electrode layer by a lift-off process; the third method is to form a patterned groove by etching the dielectric layer, and then fill the groove with metal or semiconductor material by electroplating to form the electrode layer.

[0010] The present invention provides a preferred solution, in step 2, the electrode layer is manufactured by the second method, and the dielectric layer and the electrode layer are obtained by the following method: forming the dielectric layer by deposition on the first passivation layer; forming the electrode layer by sputtering metal or semiconductor material using a patterned photoresist as a mask and stripping off the photoresist.

[0011] The present invention provides a preferred solution, wherein the electrode layer also includes a heating resistor, the interdigitated electrodes have gaps inside, the heating resistors match the shape of the interdigitated electrodes, the heating resistors are arranged in the gaps of the interdigitated electrodes and are staggered with the interdigitated electrodes; a gap is left between the heating resistors and the interdigitated electrodes; and the second passivation layer is formed on the surfaces of the heating resistors and the interdigitated electrodes.

[0012] The present invention provides a preferred solution, for the thickness of each layer in the hygrometer, one or more of the following can be selected: the thickness of the metal shielding layer is 0.1 ~0.5 ; The thickness of the first passivation layer is 100 angstroms to 3000 angstroms; the thickness of the dielectric layer is 0.5 ~1.5 The thickness of the electrode layer is 0.1 ~1 The thickness of the second passivation layer is 100 angstroms to 1000 angstroms; the thickness of the sensing layer located above the electrode layer is 1 ~3 .

[0013] The present invention provides a preferred solution, for each layer of material in the hygrometer, one or more of the following can be selected: the material of the metal shielding layer is any one of aluminum, titanium, tungsten, copper, nickel, tantalum, and polycrystalline germanium silicon; the material of the electrode layer is any one of aluminum, titanium, tungsten, copper, nickel, tantalum, and polycrystalline germanium silicon; the humidity sensing material is a polymer or a porous medium material, and the polymer is any one of polyimide, polystyrene, fluorinated polyimide, photoresist, and polydimethylsiloxane.

[0014] In a second aspect, the present invention provides a high-sensitivity MEMS hygrometer obtained by the above-mentioned manufacturing method, comprising: a supporting base layer, an insulating layer, a metal shielding layer, a first passivation layer, a dielectric layer, an electrode layer and a second passivation layer stacked in sequence, and a sensing layer filled in the dielectric layer and the electrode layer and covering the first passivation layer, the dielectric layer, the electrode layer and the second passivation layer; the first passivation layer is formed on the surface of the metal shielding layer, and the second passivation layer is formed on the surface of the electrode layer; the dielectric layer has gaps inside, and the electrode layer has gaps inside, and the sensing layer is filled in the gaps of the dielectric layer and the gaps of the electrode layer with a moisture-sensitive material; the sensing layer formed by the moisture-sensitive material filling constitutes a humidity sensitive area for humidity sensing.

[0015] Compared with the prior art, the above technical solution has the following advantages: The present invention combines the advantages of a planar interdigitated electrode capacitor structure and a vertical parallel plate capacitor structure in view of their respective characteristics, and proposes a MEMS hygrometer with an interdigitated electrode capacitor structure with a metal shielding layer. The metal shielding layer is used to isolate the parasitic capacitance below, and the area between the metal shielding layer and the interdigitated electrode is converted into a sensing area by filling a moisture-sensitive material, so that the electric field lines bent by the interdigitated electrode to the bottom are effectively utilized, thereby improving the sensitivity of the hygrometer.

[0016] The materials and manufacturing method of the hygrometer of the present invention can be realized in the metallization process of the CMOS process, and are fully compatible with the CMOS process. The manufacturing method is simple and easy to integrate and process.

[0017] Therefore, the present invention is a MEMS capacitive hygrometer which has high sensitivity and is well compatible with CMOS technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] 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.

[0019] Figure 1 Schematic diagram of sensing capacitance and parasitic capacitance of planar interdigitated electrode capacitance structure; Figure 2 It is a schematic plan view of the staggered arrangement of the interdigital electrodes and the metal heating resistors in the electrode layer of the high-sensitivity MEMS hygrometer of Examples 1 to 3 of the present invention; Figure 3 This is a schematic diagram of the structure of a supporting substrate layer with an insulating layer in a high-sensitivity MEMS hygrometer according to Embodiments 1 to 3 of the present invention; Figure 4 It is a schematic diagram of the structure of forming a metal shielding layer and a first passivation layer on the insulating layer in the high-sensitivity MEMS hygrometer of Examples 1 to 3 of the present invention; Figure 5 It is a schematic diagram of the structure of forming a dielectric layer on the first passivation layer in the high-sensitivity MEMS hygrometer of Embodiment 1 and Embodiment 2 of the present invention; Figure 6 This is a schematic diagram of the structure of a high-sensitivity MEMS hygrometer in Example 1 of the present invention by sputtering a metal layer on a dielectric layer; Figure 7 This is a schematic diagram of the structure of forming an electrode layer by a lift-off process in a high-sensitivity MEMS hygrometer according to Embodiment 2 of the present invention (without stripping off the photoresist); Figure 8 It is a schematic diagram of the structure of etching a metal layer or stripping off a photoresist to form an electrode layer in the high-sensitivity MEMS hygrometer of Embodiment 1 and Embodiment 2 of the present invention; Fig. 9 It is a schematic diagram of the structure after etching the dielectric layer using the electrode layer as a patterned mask in the high-sensitivity MEMS hygrometer of Examples 1 to 3 of the present invention; Fig.10 This is a schematic structural diagram of a high-sensitivity MEMS hygrometer in Example 1 of the present invention in which a second passivation layer is formed on the surface of an electrode layer by in-situ oxidation of metal; Fig.11 This is an overall structural diagram of the high-sensitivity MEMS hygrometer after the hygroscopic material is coated in Example 1 of the present invention; Fig.12 It is a structural schematic diagram of forming a dielectric layer on the first passivation layer in the high-sensitivity MEMS hygrometer of Example 3 of the present invention; Fig.13 This is a schematic structural diagram of etching patterned grooves on a dielectric layer and then filling the grooves with metal to form interdigital electrodes and a heating resistor in a high-sensitivity MEMS hygrometer according to Embodiment 3 of the present invention; Fig.14 It is a schematic diagram of the structure in which a second passivation layer is formed on the surface of the electrode layer by deposition in the high-sensitivity MEMS hygrometer of Examples 2 and 3 of the present invention; Fig.15 This is a diagram of the overall structure of the high-sensitivity MEMS hygrometer after the hygroscopic material is coated in Examples 2 and 3 of the present invention.

[0020] Reference numerals: photoresist mask 01 , supporting base layer 11 , insulating layer 21 , metal shielding layer 31 , first passivation layer 41 , dielectric layer 51 , electrode layer 52 , interdigital electrodes 521 , heating resistor 522 , second passivation layer 53 , sensing layer 61 . DETAILED DESCRIPTION

[0021] 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.

[0022] Embodiment 1

[0023] This embodiment first provides a high-sensitivity MEMS hygrometer, the hierarchical structure of which is as follows: the hygrometer includes a supporting base layer 11, an insulating layer 21, a metal shielding layer 31, a first passivation layer 41, a dielectric layer 51, an electrode layer 52, and a second passivation layer 53 stacked in sequence, and a sensing layer 61 filled in the dielectric layer 51 and the electrode layer 52 and covering the first passivation layer 41, the dielectric layer 51, the electrode layer 52, and the second passivation layer 53; the first passivation layer 41 is formed on the surface of the metal shielding layer 31, and the second passivation layer 53 is formed on the surface of the electrode layer 52; the dielectric layer 51 has a gap inside, and the electrode layer 52 has a gap inside, and the sensing layer 61 is filled in the gap of the dielectric layer 51 and the gap of the electrode layer 52 by a moisture-sensitive material; the sensing layer 61 formed by the moisture-sensitive material constitutes a humidity sensitive area for humidity sensing. Among them, the metal shielding layer 31 is composed of a metal shielding electrode, and the electrode layer 52 has a planar interdigitated electrode 521.

[0024] Please refer to Figure 1 , a simplified capacitance model of the existing planar interdigitated electrode capacitor structure is given. The planar interdigitated electrode capacitor structure has a sensing capacitor , non-sensing parasitic capacitance from the dielectric layer and substrate , The parasitic capacitance from the air can be reduced by increasing the thickness of the moisture-sensitive material, which is not shown here. Different from the traditional parallel plate capacitor structure, the planar interdigitated electrode has a more significant edge effect due to the small distance between the plates, which produces an uneven divergent electric field. Since the electric field is divergent, it will produce interlayer parasitic capacitance.

[0025] The high-sensitivity MEMS hygrometer provided in this embodiment isolates the parasitic capacitance below through the metal shielding layer 31, and converts the area between the metal shielding layer 31 and the interdigital electrodes 521 into a sensing area by filling the moisture-sensitive material, thereby improving the sensitivity of the sensor.

[0026] Please refer to Figure 2 In addition to the interdigital electrodes 521, the electrode layer 52 of this embodiment is also provided with a heating resistor 522. The positive and negative plates of the interdigital electrodes 521 are arranged alternately, and there is a gap between the positive and negative plates. The heating resistor 522 matches the shape of the interdigital electrodes 521. The heating resistor 522 is arranged in the gap of the interdigital electrodes 521 and is arranged alternately with the interdigital electrodes 521. From the figure, a serpentine heating resistor 522 is arranged in the gap of the interdigital electrodes 521, but there is a gap between the heating resistor 522 and the interdigital electrodes 521. Among them, the interdigital electrodes 521 are used for humidity sensing, and the heating resistor 522 is used for temperature sensing to perform temperature compensation, and can help the moisture-sensitive material to quickly dehumidify.

[0027] This embodiment also provides a method for manufacturing a high-sensitivity MEMS hygrometer, please refer to Figures 3 to 6 , Figures 8 to 11 , mainly includes the following steps: Step 1: Prepare a supporting base layer 11, an insulating layer 21, a metal shielding layer 31 and a first passivation layer 41: Prepare a supporting base layer 11 having an insulating layer 21, form a metal shielding layer 31 above the insulating layer 21 of the supporting base layer 11, and form a thin passivation layer as a first passivation layer 41 on the surface of the metal shielding layer 31. Optionally, the material used for the metal shielding layer 31 can be a metal or semiconductor material commonly used in CMOS processes such as aluminum, titanium, tungsten, copper, nickel, tantalum, polycrystalline germanium silicon, etc. Optionally, the first passivation layer 41 on the surface of the metal shielding layer 31 is formed by depositing a passivation layer or in-situ oxidation of the metal. As an example, aluminum metal is selected in this embodiment, and the first passivation layer 41 is formed by in-situ oxidation of the metal. More detailed steps are as follows: Please refer to Figure 3 and Figure 4 The supporting base layer 11 has an insulating layer 21 formed thereon by sputtering. A thick metal shielding layer 31 (aluminum metal shielding layer) is formed, and the metal shielding layer 31 does not constitute a loop and is grounded. Since aluminum can form a dense oxide film on the surface to prevent water vapor from invading, that is, an aluminum oxide film is formed on the surface of the metal shielding layer 31 of aluminum material, therefore, in this embodiment, the first passivation layer 41 on the surface of the metal shielding layer 31 is formed by in-situ oxidation of the metal, and the main method is: heating the top of the metal shielding layer 31 at 200°C to 450°C in an oxygen environment to form a 200 angstrom thick aluminum oxide film on the surface of the aluminum metal as the first passivation layer 41.

[0028] Step 2: Making a dielectric layer 51 and an electrode layer 52: A dielectric layer 51 is formed on the first passivation layer 41, and then an electrode layer 52 is made. A layer of metal or semiconductor material can be sputtered on the dielectric layer 51, and then etched to form the electrode layer 52. Optionally, the material of the electrode layer 52 can be aluminum, titanium, tungsten, copper, nickel, tantalum, polycrystalline germanium silicon, and other metal or semiconductor materials commonly used in CMOS processes. As an example, aluminum metal is selected in this embodiment. More detailed steps are as follows: Please refer to Figure 5 A 0.5 μm thick silicon dioxide dielectric layer 51 is formed on the first passivation layer 41 by deposition, see Figure 6 Then, a 0.5 mm thick layer is sputtered on the silicon dioxide dielectric layer 51. For thick aluminum, please refer to Figure 8 , aluminum metal is etched to form interdigital electrodes 521 and heating resistors 522 , thereby forming an electrode layer 52 .

[0029] Step 3: Etch the dielectric layer 51, and then form a thin passivation layer as the second passivation layer 53 on the surface of the exposed electrode layer 52; wherein, optionally, the second passivation layer 53 on the surface of the electrode layer 52 is formed by depositing a passivation layer or in-situ oxidation of metal. In this embodiment, since the material of the electrode layer 52 is aluminum, the second passivation layer 53 on the surface of the electrode layer 52 is formed by in-situ oxidation of metal. More detailed steps are as follows: Please refer to Fig. 9 Then, the silicon dioxide dielectric layer 51 is etched using the interdigital electrodes 521 and the heating resistors 522 as patterned masks to remove the dielectric not covered by the electrode layer 52. Since the electrode layer 52 of this embodiment has the interdigital electrodes 521 and the heating resistors 522, in this step, the surfaces of the interdigital electrodes 521 and the heating resistors 522 are both oxidized in situ by metal to form a layer of aluminum oxide film to form the second passivation layer 53. Please refer to Fig.10 The second passivation layer 53 is formed by in-situ oxidation of the metal. The main method is: heating the electrode layer 52 at 200°C to 450°C in an oxygen environment to form a 100 angstrom thick aluminum oxide film on the aluminum surface as the second passivation layer 53.

[0030] Step 4: Please refer to Fig.11 , a moisture-sensitive material is coated on the second passivation layer 53 of the electrode layer 52, and the moisture-sensitive material is filled inside the dielectric layer 51, and inside and above the second passivation layer 53, to obtain the high-sensitivity MEMS hygrometer of this embodiment. Optionally, the moisture-sensitive material can be a polymer or a porous dielectric material, and the polymer can be any one of polyimide, polystyrene, fluorinated polyimide, photoresist, and polydimethylsiloxane. As an example, the moisture-sensitive material of this embodiment is polyimide. More specifically, this embodiment forms the sensing layer 61 by spin-coating the moisture-sensitive material polyimide, and the thickness of the polyimide above the interdigitated electrode 521 is 2 .

[0031] Considering that some existing MEMS capacitive humidity sensors are difficult to be compatible with CMOS technology, compatibility with CMOS technology can enable MEMS sensors and CMOS to be integrated on the same chip, which has great advantages in terms of cost, power consumption, etc. The processes and materials involved in the above embodiments are all commonly used processes and materials in CMOS technology, and can all be implemented in the CMOS metallization process, so the compatibility with CMOS technology is very high. At the same time, the MEMS hygrometer provided in the above embodiments has the advantages of high sensitivity, fast response time, high reliability, high precision, etc.

[0032] Embodiment 2

[0033] The device structure of the second embodiment is the same as that of the first embodiment, and the only difference is in the manufacturing process or the materials used, especially in the process of manufacturing the electrode layer 52, the lift-off process is adopted. Figures 3 to 5 , Figures 7 to 9 , Fig.14 , Fig.15 , including the following steps: Step 1: Prepare a supporting base layer 11, an insulating layer 21, a metal shielding layer 31 and a first passivation layer 41: Prepare a supporting base layer 11 having an insulating layer 21, form a metal shielding layer 31 above the insulating layer 21 of the supporting base layer 11, and form a thin passivation layer as a first passivation layer 41 on the surface of the metal shielding layer 31. Optionally, the material used for the metal shielding layer 31 can be a metal or semiconductor material commonly used in CMOS processes such as aluminum, titanium, tungsten, copper, nickel, tantalum, polycrystalline germanium silicon, etc. Optionally, the first passivation layer 41 on the surface of the metal shielding layer 31 is formed by depositing a passivation layer or in-situ oxidation of the metal. As an example, titanium metal is selected in this embodiment, and the first passivation layer 41 is formed by depositing a passivation layer. More detailed steps are as follows: Please refer to Figure 3 and Figure 4The supporting base layer 11 has an insulating layer 21 formed thereon by sputtering. A thick titanium metal is used as the metal shielding layer 31. The metal shielding layer 31 does not constitute a loop and is grounded. A 3000 angstrom thick silicon nitride passivation layer is formed by deposition on the metal shielding layer 31 as the first passivation layer 41. Forming the passivation layer by deposition makes the material selection of the metal shielding electrode very flexible.

[0034] Step 2: Making a dielectric layer 51 and an electrode layer 52: A dielectric layer 51 is formed on the first passivation layer 41, and interdigital electrodes 521 and heating resistors 522 are formed on the dielectric layer 51 by a lift-off process. The more detailed steps are as follows: Please refer to Figure 5 , a 1 is formed on the first passivation layer 41 by deposition A thick dielectric layer 51 of silicon oxynitride. The lift-off process mainly includes: Figure 7 , by sputtering titanium metal using a patterned photoresist as a mask (photoresist mask 01 in the figure), and then stripping the photoresist to form 1 Thick interdigitated electrodes 521 and heating resistors 522, please refer to Figure 8 Optionally, the electrode layer material may be aluminum, titanium, tungsten, copper, nickel, tantalum, polycrystalline germanium silicon or other metal or semiconductor materials commonly used in CMOS processes. As an example, titanium metal is selected in this embodiment. The lift-off process can simplify the process flow, and the deposition of the first passivation layer 41 can make the material selection of the metal shielding layer 31 more flexible.

[0035] Step 3: Etch the dielectric layer 51, and use the titanium metal (electrode layer 52) as a patterned template to etch the silicon oxynitride dielectric layer 51, and then form a thin passivation layer as the second passivation layer 53 on the surface of the exposed electrode layer 52; wherein, optionally, the second passivation layer 53 on the surface of the electrode layer 52 is formed by depositing a passivation layer or in-situ oxidation of the metal. In this embodiment, because the metal of the electrode layer 52 is titanium, the second passivation layer 53 on the surface of the electrode layer 52 is formed by depositing a passivation layer. More detailed steps are as follows: Use the titanium metal as a patterned mask to etch the silicon oxynitride to form the electrode layer 52, please refer to Fig. 9 Then, a 1000 angstrom thick silicon nitride film passivation layer is deposited as the second passivation layer 53. Please refer to Fig.14 .

[0036] Step 4: Coat the moisture-sensitive material on the second passivation layer 53 of the electrode layer 52. The moisture-sensitive material is filled inside the dielectric layer 51 and inside and above the second passivation layer 53 to obtain the high-sensitivity MEMS hygrometer of this embodiment. Please refer to Fig.15Optionally, the moisture sensing material may be a polymer or a porous medium material, and the polymer may be any one of polyimide, polystyrene, fluorinated polyimide, photoresist, and polydimethylsiloxane. As an example, the moisture sensing material of this embodiment is polystyrene. More specifically, in this embodiment, the sensing layer 61 is formed by spin coating the moisture sensing material polystyrene, and the thickness of the polystyrene above the interdigital electrode 521 is 1 .

[0037] Embodiment 3

[0038] The device structure of the third embodiment is the same as that of the first embodiment, and the only difference is in the manufacturing process or the materials used, especially in the process of making the electrode layer 52, the electroplating process is used. The third embodiment provides a method for manufacturing a high-sensitivity MEMS hygrometer, please refer to Figure 3 , Figure 4 , Fig.12 , Fig.13 , Fig. 9 , Fig.14 , Fig.15 , including the following steps: Step 1: Prepare a supporting base layer 11, an insulating layer 21, a metal shielding layer 31 and a first passivation layer 41: Prepare a supporting base layer 11 having an insulating layer 21, form a metal shielding layer 31 above the insulating layer 21 of the supporting base layer 11, and form a thin passivation layer as a first passivation layer 41 on the surface of the metal shielding layer 31. Optionally, the material used for the metal shielding layer 31 can be a metal or semiconductor material commonly used in CMOS processes such as aluminum, titanium, tungsten, copper, nickel, tantalum, polycrystalline germanium silicon, etc. Optionally, the first passivation layer 41 on the surface of the metal shielding layer 31 is formed by depositing a passivation layer or in-situ oxidation of the metal. As an example, copper metal is selected in this embodiment, and the first passivation layer 41 is formed by depositing a passivation layer. More detailed steps are as follows: Please refer to Figure 3 and Figure 4 The supporting base layer 11 has an insulating layer 21 formed thereon by electroplating to form a 0.1 A thick copper metal is used as the metal shielding layer 31, which does not constitute a loop and is grounded. A 100 angstrom thick silicon nitride passivation layer is formed by deposition on the metal shielding layer 31 as the first passivation layer 41. Forming the passivation layer by deposition makes the material selection of the metal shielding electrode very flexible.

[0039] Step 2: Making a dielectric layer 51 and an electrode layer 52: A dielectric layer 51 is formed on the first passivation layer 41, a groove is formed by etching the dielectric layer 51, and an electrode is filled in the groove to form an electrode layer 52 having interdigitated electrodes 521. Optionally, the electrode layer 52 may be formed by sputtering or depositing metal in the groove. As an example, the present embodiment adopts a sputtering process. More detailed steps are as follows: Please refer to Fig.12 , a 1.5 A 0.1 thick silicon oxynitride dielectric layer 51 is formed on the dielectric by photolithography. A deep patterned groove is then formed in the groove by electroplating a metal or semiconductor material to form an interdigitated electrode 521 and a heating resistor 522. Fig.13 Optionally, the electrode layer material may be aluminum, titanium, tungsten, copper, nickel, tantalum, polycrystalline germanium silicon or other metal or semiconductor materials commonly used in CMOS processes. As an example, the electrode layer material of this embodiment is copper metal.

[0040] Step 3: Etch the dielectric layer 51, and then form a thin passivation layer as the second passivation layer 53 on the surface of the exposed electrode layer 52; wherein, optionally, the second passivation layer 53 on the surface of the electrode layer 52 is formed by depositing a passivation layer or in-situ oxidation of the metal. In this embodiment, because the material of the electrode layer 52 is copper, the second passivation layer 53 on the surface of the electrode layer 52 is formed by depositing a passivation layer. More detailed steps are as follows: Then, the dielectric layer of silicon oxynitride is etched using the copper metal as a patterned mask to form the electrode layer 52, and the dielectric not covered by the electrode layer 52 is removed, please refer to Fig. 9 Then, a 100 angstrom thick silicon nitride film passivation layer is deposited as the second passivation layer 53. Please refer to Fig.14 .

[0041] Step 4: Coat the moisture-sensitive material on the second passivation layer 53 of the electrode layer 52. The moisture-sensitive material is filled inside the dielectric layer 51 and inside and above the second passivation layer 53 to obtain the high-sensitivity MEMS hygrometer of this embodiment. Please refer to Fig.15 Optionally, the moisture sensing material may be a polymer or a porous dielectric material, and the polymer may be any one of polyimide, polystyrene, fluorinated polyimide, photoresist, and polydimethylsiloxane. As an example, the moisture sensing material of this embodiment is fluorinated polyimide. More specifically, this embodiment forms the sensing layer 61 by spin coating the fluorinated polyimide, a moisture sensing material, and the thickness of the fluorinated polyimide above the interdigital electrode 521 is 3 .

[0042] The selection of materials, dimensions and process parameters for the key structural layers of the above-mentioned embodiments 1 to 3 are respectively shown in Tables 1 to 3 below.

[0043] Table 1: Key structural layer parameters of Example 1

[0044] Table 2: Key structural layer parameters of Example 2

[0045] Table 3: Key structural layer parameters of Example 3

[0046] In summary, through the above embodiments, the present invention sets a metal shielding layer under the interdigital electrode to isolate the parasitic capacitance interference from under the shielding electrode, and fills the humidity sensitive material between the metal shielding electrode and the interdigital electrode to form an additional humidity sensing layer, which converts the parasitic capacitance of the area into a sensing capacitance. Therefore, the sensitivity of the sensor is greatly improved, and the metal of the electrode layer is passivated to play an insulating protection role, which can effectively improve the reliability of the sensor. At the same time, the processes and materials involved in the above embodiments are all commonly used processes and materials in CMOS processes, and can be implemented in the CMOS metallization process, so the compatibility with CMOS processes is very high.

[0047] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0048] The above-described embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A method for manufacturing a high-sensitivity MEMS hygrometer, comprising: Step 1: preparing a supporting base layer, an insulating layer, a metal shielding layer and a first passivation layer: preparing a supporting base layer having an insulating layer, forming a metal shielding layer on the insulating layer of the supporting base layer, and forming a thin passivation layer on the surface of the metal shielding layer as the first passivation layer; Step 2: Making a dielectric layer and an electrode layer: forming a dielectric layer on the first passivation layer, and then making an electrode layer; Step 3: etching the dielectric layer, and then forming a thin passivation layer as a second passivation layer on the surface of the exposed electrode layer; Step 4: Coating a moisture-sensitive material on the second passivation layer of the electrode layer, wherein the moisture-sensitive material is filled inside the dielectric layer and inside and above the second passivation layer to obtain the moisture meter.

2. The method for manufacturing a high-sensitivity MEMS hygrometer according to claim 1, characterized in that: In step 1, the metal shielding layer is formed by sputtering or electroplating. The metal shielding layer does not constitute a loop, and one end of the metal shielding layer is connected to a metal wire and grounded.

3. The method for manufacturing a high-sensitivity MEMS hygrometer according to claim 1, characterized in that: In step 1, the first passivation layer on the surface of the metal shielding layer is formed by depositing a passivation layer or in-situ oxidation of the metal; and / or, the second passivation layer on the surface of the electrode layer is formed by depositing a passivation layer or in-situ oxidation of the metal.

4. The method for manufacturing a high-sensitivity MEMS hygrometer according to claim 3, characterized in that: The metal in-situ oxidation comprises: heating the surface of the metal shielding layer / electrode layer in an oxygen environment to oxidize the surface to form a first passivation layer / a second passivation layer.

5. The method for manufacturing a high-sensitivity MEMS hygrometer according to claim 1, characterized in that: In step 2, the electrode layer is made by one of the following methods: the first method is to sputter a layer of metal or semiconductor material on the dielectric layer and etch it to form an electrode layer; the second method is to form the electrode layer by a lift-off process; the third method is to form a patterned groove by etching the dielectric layer, and fill the groove with metal or semiconductor material by electroplating to form an electrode layer.

6. The method for manufacturing a high-sensitivity MEMS hygrometer according to claim 5, characterized in that: In step 2, the electrode layer is made by the second method, and the dielectric layer and the electrode layer are obtained by the following method: forming a dielectric layer by deposition on the first passivation layer; forming the electrode layer by sputtering a metal or semiconductor material using a patterned photoresist as a mask and stripping the photoresist.

7. The method for manufacturing a high-sensitivity MEMS hygrometer according to claim 1, characterized in that: The electrode layer also includes a heating resistor. There is a gap inside the interdigital electrode. The heating resistor matches the shape of the interdigital electrode. The heating resistor is arranged in the gap of the interdigital electrode and is staggered with the interdigital electrode. A gap is left between the heating resistor and the interdigital electrode. The second passivation layer is formed on the surface of the heating resistor and the interdigital electrode.

8. The method for manufacturing a high-sensitivity MEMS hygrometer according to claim 1, characterized in that: For the thickness of each layer in the hygrometer, select one or more of the following: the thickness of the metal shielding layer is 0.1 ~0.5 ; The thickness of the first passivation layer is 100 angstroms to 3000 angstroms; the thickness of the dielectric layer is 0.5 ~1.5μm The thickness of the electrode layer is 0.1 ~1 The thickness of the second passivation layer is 100 angstroms to 1000 angstroms; the thickness of the sensing layer located above the electrode layer is 1 ~3 .

9. The method for manufacturing a high-sensitivity MEMS hygrometer according to claim 1, characterized in that: For the materials of each layer in the hygrometer, one or more of the following can be selected: the material of the metal shielding layer is any one of aluminum, titanium, tungsten, copper, nickel, tantalum, and polycrystalline germanium silicon; the material of the electrode layer is any one of aluminum, titanium, tungsten, copper, nickel, tantalum, and polycrystalline germanium silicon; the humidity sensing material is a polymer or a porous dielectric material, and the polymer is any one of polyimide, polystyrene, fluorinated polyimide, photoresist, and polydimethylsiloxane.

10. A high-sensitivity MEMS hygrometer, obtained by the manufacturing method according to any one of claims 1 to 9, characterized in that: include: A supporting base layer, an insulating layer, a metal shielding layer, a first passivation layer, a dielectric layer, an electrode layer, and a second passivation layer are stacked in sequence, and a sensing layer is filled in the dielectric layer and the electrode layer and covers the first passivation layer, the dielectric layer, the electrode layer, and the second passivation layer; the first passivation layer is formed on the surface of the metal shielding layer, and the second passivation layer is formed on the surface of the electrode layer; the dielectric layer has gaps inside, and the electrode layer has gaps inside, and the sensing layer is filled in the gaps of the dielectric layer and the gaps of the electrode layer with a moisture-sensitive material; the sensing layer formed by the moisture-sensitive material constitutes a humidity sensitive area for humidity sensing.

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