A high-sensitivity MEMS hygrometer and its manufacturing method

Abstract

The present invention provides a high-sensitivity MEMS hygrometer and a manufacturing method thereof, which relate to the technical fields of microelectromechanical systems and semiconductor chip manufacturing processes. The hygrometer includes a support substrate 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 sensing layer is filled in the gaps between the dielectric layer and the electrode layer with a humidity-sensitive material for humidity sensing. The present invention provides a metal shielding layer below the electrode layer to isolate the parasitic capacitance interference below it, and fills a humidity-sensitive material between the metal shielding layer and the electrode layer to form an additional humidity sensing layer, converting the parasitic capacitance in this area into a sensing capacitance, greatly improving the sensitivity of the sensor. Moreover, the processes and materials involved in the present invention are all common processes and materials in the CMOS process, and have a high compatibility with the CMOS process.

Description

Technical Field

[0001] The present invention relates to the technical fields of microelectromechanical systems and semiconductor chip manufacturing processes, and particularly relates 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 humidity changes by sensing the change in the relative dielectric constant of the sensing layer (such as a polymer film) after water vapor absorption. Usually, according to the structure of the capacitor, they can be further divided into planar interdigital electrode capacitor structures and vertical parallel plate capacitor structures. 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 lower sensing material. This structure avoids the parasitic capacitance interference between the substrate and the air, but results in a longer water vapor diffusion path. Therefore, the vertical parallel plate capacitor structure has higher sensitivity but longer response time. For the planar interdigital electrode capacitor structure, the positive and negative plates are on the same horizontal plane, and the humidity sensing material is filled between the interdigital electrodes and directly contacts the external environment, so it has a larger humidity sensing area and shorter water vapor diffusion, and the response speed is faster, 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 purpose of the present invention is to provide a high-sensitivity MEMS hygrometer and a manufacturing method thereof, which can be compatible with the CMOS process, have low manufacturing cost, and high sensitivity of the hygrometer.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a manufacturing method of a high-sensitivity MEMS hygrometer in the first aspect, including the following:

[0008] Step 1: Fabricate a support base layer, an insulating layer, a metal shielding layer and a first passivation layer: Prepare a support base layer with an insulating layer, form a layer of metal shielding layer above the insulating layer of the support base layer, and form a thin passivation layer on the surface of the metal shielding layer as the first passivation layer;

[0009] Step 2: Fabricate the dielectric layer and the electrode layer: Form a layer of dielectric layer above the first passivation layer, and then fabricate the electrode layer;

[0010] Step 3: Etch the dielectric layer, and then form a thin passivation layer on the surface of the exposed electrode layer as the second passivation layer;

[0011] Step 4: Coat a humidity-sensitive material above the second passivation layer of the electrode layer, and the humidity-sensitive material forms a filling inside the dielectric layer, as well as inside and above the second passivation layer, to obtain the hygrometer.

[0012] The present invention provides a preferred solution. In Step 1, the metal shielding layer is formed by sputtering or electroplating, and the metal shielding layer does not form a loop. One end of it is connected to a metal wire and grounded.

[0013] 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.

[0014] The present invention provides a preferred solution. In Step 2, the electrode layer is fabricated by one of the following methods: The first method, sputter a layer of metal or semiconductor material on the dielectric layer and etch to form the electrode layer; The second method, form the electrode layer by the lift-off process; The third method, form a patterned trench by etching the dielectric layer, and electroplate and fill the trench with a metal or semiconductor material to form the electrode layer.

[0015] The present invention provides a preferred solution. When the electrode layer is fabricated by the second method in Step 2, the dielectric layer and the electrode layer are obtained by the following method: Form the dielectric layer by deposition on the first passivation layer; Sputter a metal or semiconductor material using a patterned photoresist as a mask and strip the photoresist to form the electrode layer.

[0016] The present invention provides a preferred solution. The electrode layer further includes a heating resistor. There are voids inside the interdigital electrodes. The heating resistor matches the shape of the interdigital electrodes and is arranged in the voids of the interdigital electrodes in an interleaved manner with the interdigital electrodes; There is a gap between the heating resistor and the interdigital electrodes; The second passivation layer is formed on the surfaces of both the heating resistor and the interdigital electrodes.

[0017] The present invention provides a preferred solution. For the thicknesses of each layer in the hygrometer, any 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 Å to 3000 Å; 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 Å to 1000 Å; the thickness of the partial sensing layer of the sensing layer located above the electrode layer is 1 ~3 .

[0018] The present invention provides a preferred solution. For each layer of materials in the hygrometer, any one or more of the following are 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 selected from any one of aluminum, titanium, tungsten, copper, nickel, tantalum, and polycrystalline germanium silicon; the humidity-sensitive material is selected from a polymer or a porous medium material, and the polymer is selected from any one of polyimide, polystyrene, fluorinated polyimide, photoresist, and polydimethylsiloxane.

[0019] In a second aspect, the present invention provides a high-sensitivity MEMS hygrometer obtained by the above manufacturing method, including: a support substrate 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 interior of the dielectric layer has voids, the interior of the electrode layer has voids, and the sensing layer is filled with a humidity-sensitive material in the voids of the dielectric layer and the voids of the electrode layer; the sensing layer formed by filling the humidity-sensitive material constitutes a humidity-sensitive region for humidity sensing.

[0020] Compared with the prior art, the above technical solution has the following advantages:

[0021] In view of the respective characteristics of the planar interdigital electrode capacitor structure and the vertical parallel-plate capacitor structure, the present invention combines the advantages of the two structures and proposes a MEMS hygrometer with an interdigital electrode capacitor structure with a metal shielding layer. The metal shielding layer is used to isolate the parasitic capacitance below, and the region between the metal shielding layer and the interdigital electrodes is converted into a sensing region by filling with a humidity-sensitive material, so that the bent electric field lines below the interdigital electrodes are effectively utilized, improving the sensitivity of the hygrometer.

[0022] The materials and manufacturing method used in the hygrometer of the present invention can be realized in the metallization process of the CMOS process, are fully compatible with the CMOS process, and the manufacturing method is simple and easy to integrate and process.

[0023] Therefore, the present invention is a MEMS capacitive hygrometer with high sensitivity and good compatibility with the CMOS process. Description of the Drawings

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0025] Figure 1 Schematic diagram of the sensing capacitance and parasitic capacitance of the planar interdigital electrode capacitance structure;

[0026] Figure 2 Schematic plan view of the staggered arrangement of the interdigital electrodes and metal heating resistors in the electrode layer of the high-sensitivity MEMS humidity meter according to Embodiments 1 to 3 of the present invention;

[0027] Figure 3 Schematic diagram of the support substrate layer with an insulating layer in the high-sensitivity MEMS humidity meter according to Embodiments 1 to 3 of the present invention;

[0028] Figure 4 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 humidity meter according to Embodiments 1 to 3 of the present invention;

[0029] Figure 5 Schematic diagram of the structure of forming a dielectric layer on the first passivation layer in the high-sensitivity MEMS humidity meter according to Embodiments 1 and 2 of the present invention;

[0030] Figure 6 Schematic diagram of the structure of sputtering a metal layer on the dielectric layer in the high-sensitivity MEMS humidity meter according to Embodiment 1 of the present invention;

[0031] Figure 7 Schematic diagram of the structure of forming an electrode layer by the lift-off process (photoresist not peeled off) in the high-sensitivity MEMS humidity meter according to Embodiment 2 of the present invention;

[0032] Figure 8 Schematic diagram of the structure of etching the metal layer or peeling off the photoresist to form an electrode layer in the high-sensitivity MEMS humidity meter according to Embodiments 1 and 2 of the present invention;

[0033] Figure 9 Schematic diagram of the structure after etching the dielectric layer using the electrode layer as a patterning mask in the high-sensitivity MEMS humidity meter according to Embodiments 1 to 3 of the present invention;

[0034] Figure 10 Schematic diagram of the structure of forming a second passivation layer on the surface of the electrode layer by in-situ metal oxidation in the high-sensitivity MEMS humidity meter according to Embodiment 1 of the present invention;

[0035] Figure 11 It is the overall structure diagram after coating the humidity-sensitive material in the high-sensitivity MEMS humidity meter of Embodiment 1 of the present invention;

[0036] Figure 12 It is the schematic structural diagram of forming a dielectric layer on the first passivation layer in the high-sensitivity MEMS humidity meter of Embodiment 3 of the present invention;

[0037] Figure 13 It is the schematic structural diagram of etching patterned trenches on the dielectric layer and filling the trenches with metal to form interdigital electrodes and heating resistors in the high-sensitivity MEMS humidity meter of Embodiment 3 of the present invention;

[0038] Figure 14 It is the schematic structural diagram of forming a second passivation layer on the surface of the electrode layer by deposition in the high-sensitivity MEMS humidity meters of Embodiment 2 and Embodiment 3 of the present invention;

[0039] Figure 15 It is the overall structure diagram after coating the humidity-sensitive material in the high-sensitivity MEMS humidity meters of Embodiment 2 and Embodiment 3 of the present invention.

[0040] Reference numerals: photoresist mask 01, support base layer 11, insulating layer 21, metal shielding layer 31, first passivation layer 41, dielectric layer 51, electrode layer 52, interdigital electrode 521, heating resistor 522, second passivation layer 53, sensing layer 61. Detailed implementation manners

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0042] Embodiment 1

[0043] This embodiment first provides a high-sensitivity MEMS hygrometer, and its hierarchical structure is as follows: The hygrometer includes a support substrate 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 that are stacked in sequence, and a sensing layer 61 that fills the dielectric layer 51 and the electrode layer 52 and covers 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; there are voids inside the dielectric layer 51, there are voids inside the electrode layer 52, and the sensing layer 61 is filled with a humidity-sensitive material in the voids of the dielectric layer 51 and the voids of the electrode layer 52; the sensing layer 61 formed by filling the humidity-sensitive material constitutes a humidity-sensitive region for humidity sensing. Among them, the metal shielding layer 31 is composed of metal shielding electrodes, and the electrode layer 52 has planar interdigital electrodes 521.

[0044] Please refer to Figure 1 , which gives a simplified capacitance model of the existing planar interdigital electrode capacitance structure. The planar interdigital electrode capacitance structure has a sensing capacitance , a non-sensing parasitic capacitance from the dielectric layer and the substrate , , and the parasitic capacitance from the air can be reduced by increasing the thickness of the humidity-sensitive material, which is not shown here. Different from the traditional parallel-plate capacitance structure, due to the small plate spacing of the planar interdigital electrodes, the edge effect is more significant, generating a non-uniform and divergent electric field. Since the electric field is divergent, an interlayer parasitic capacitance will be generated.

[0045] The high-sensitivity MEMS hygrometer provided by this embodiment isolates the parasitic capacitance below through the metal shielding layer 31, and fills the region between the metal shielding layer 31 and the interdigital electrodes 521 with a humidity-sensitive material to convert this region into a sensing region, thereby improving the sensor sensitivity.

[0046] 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 in an alternating manner, and there are voids between the positive and negative plates. The heating resistor 522 matches the shape of the interdigital electrodes 521, and the heating resistor 522 is arranged in the voids of the interdigital electrodes 521 and arranged in an alternating manner with the interdigital electrodes 521. From the figure, a serpentine heating resistor 522 is arranged at the voids 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 for temperature compensation and can help the humidity-sensitive material quickly dehumidify.

[0047] This embodiment also provides a manufacturing method for a high-sensitivity MEMS hygrometer. Please refer toFigures 3 to 6 , Figures 8 to 11 , which mainly includes the following steps:

[0048] Step 1: Fabricate the support base layer 11, insulation layer 21, metal shielding layer 31 and first passivation layer 41: Prepare the support base layer 11 with the insulation layer 21, form a layer of metal shielding layer 31 above the insulation layer 21 of the support base layer 11, and form a thin passivation layer on the surface of the metal shielding layer 31 as the first passivation layer 41. Optionally, the material used for the metal shielding layer 31 can be aluminum, titanium, tungsten, copper, nickel, tantalum, polycrystalline germanium silicon and other common metals or semiconductor materials in CMOS processes. 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, in this embodiment, aluminum metal is selected, and the first passivation layer 41 is formed by in-situ oxidation of the metal. The more detailed steps are as follows:

[0049] Please refer to Figure 3 and Figure 4 , the support base layer 11 has a layer of insulation layer 21 thereon, and a 0.5 -thick metal shielding layer 31 (aluminum metal shielding layer) is formed by sputtering. The metal shielding layer 31 does not form 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 alumina thin film is formed on the surface of the metal shielding layer 31 made 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. The main method is: heating the upper part of the metal shielding layer 31 at 200 °C to 450 °C in an oxygen environment to form a 200-angstrom-thick alumina thin film on the surface of the aluminum metal as the first passivation layer 41.

[0050] Step 2: Fabricate the dielectric layer 51 and electrode layer 52: Form a layer of dielectric layer 51 above the first passivation layer 41, and then fabricate the electrode layer 52. A layer of metal or semiconductor material can be sputtered on the dielectric layer 51 and etched to form the electrode layer 52. Optionally, the material of the electrode layer 52 can be selected from aluminum, titanium, tungsten, copper, nickel, tantalum, polycrystalline germanium silicon and other common metals or semiconductor materials in CMOS processes. As an example, aluminum metal is selected in this embodiment. The more detailed steps are as follows:

[0051] Please refer to Figure 5 , a 0.5-μm-thick silicon dioxide dielectric layer 51 is formed by deposition on the first passivation layer 41. Please refer to Figure 6 , and then a 0.5 -thick aluminum metal is sputtered on the silicon dioxide dielectric layer 51. Please refer to Figure 8 , and the aluminum metal is etched to form the interdigital electrode 521 and the heating resistor 522, thus forming the electrode layer 52.

[0052] Step 3: Etch the dielectric layer 51, and then form a thin passivation layer on the surface of the exposed electrode layer 52 as the second passivation layer 53. 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, 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 the metal. The more detailed steps are as follows:

[0053] Please refer to Figure 9 , and then use the interdigital electrode 521 and the heating resistor 522 as the patterning mask to etch the silicon dioxide dielectric layer 51, and remove the dielectric not covered by the electrode layer 52. Since the electrode layer 52 in this embodiment has the interdigital electrode 521 and the heating resistor 522, in this step, a layer of aluminum oxide film is formed on the surfaces of the interdigital electrode 521 and the heating resistor 522 by in-situ oxidation of the metal to form the second passivation layer 53. Please refer to Figure 10 , the second passivation layer 53 is formed by in-situ oxidation of the metal. The main method is: heat the upper part of the electrode layer 52 in an oxygen environment at 200°C to 450°C to form a 100-angstrom-thick aluminum oxide film on the aluminum surface as the second passivation layer 53.

[0054] Step 4: Please refer to Figure 11 , coat a humidity-sensitive material on the second passivation layer 53 of the electrode layer 52. The humidity-sensitive material fills the inside of the dielectric layer 51, as well as the inside and above the second passivation layer 53, to obtain the high-sensitivity MEMS humidity sensor of this embodiment. Optionally, the humidity-sensitive material can be selected from polymer or porous dielectric materials, and the polymer can be any one of polyimide, polystyrene, fluorinated polyimide, photoresist, and polydimethylsiloxane. As an example, the humidity-sensitive material in this embodiment is polyimide. More specifically, in this embodiment, the sensing layer 61 is formed by spin-coating the humidity-sensitive material polyimide. The thickness of the polyimide above the interdigital electrode 521 is 2 .

[0055] Considering that some existing MEMS capacitive humidity sensors are difficult to be compatible with the CMOS process, and being compatible with the CMOS process can integrate the MEMS sensor and the CMOS 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 common processes and materials in the CMOS process, and can be realized during the CMOS metallization process. Therefore, the compatibility with the CMOS process is very high. At the same time, the MEMS humidity sensor provided by the above embodiments has the advantages of high sensitivity, fast response time, high reliability, high precision, etc.

[0056] Embodiment 2

[0057] The device structure of Example 2 is the same as that of Example 1, with differences only in the manufacturing process or the materials used. In particular, in the process of fabricating the electrode layer 52, the lift-off process is adopted. For the manufacturing method of a high-sensitivity MEMS hygrometer provided by Example 2, please refer to Figures 3 to 5 , Figures 7 to 9 , Figure 14 , Figure 15 , including the following steps:

[0058] Step 1: Fabricate the support substrate layer 11, insulation layer 21, metal shielding layer 31 and the first passivation layer 41: Prepare a support substrate layer 11 with an insulation layer 21, form a layer of metal shielding layer 31 above the insulation layer 21 of the support substrate layer 11, and form a thin passivation layer on the surface of the metal shielding layer 31 as the first passivation layer 41. Optionally, the material used for the metal shielding layer 31 can be common metals or semiconductor materials 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, in this embodiment, titanium metal is selected, and the first passivation layer 41 is formed by depositing a passivation layer. The more detailed steps are as follows:

[0059] Please refer to Figure 3 and Figure 4 , the support substrate layer 11 has an insulation layer 21 thereon, and 0.3 thick titanium metal is formed by sputtering as the metal shielding layer 31, and the metal shielding layer 31 does not form a loop and is grounded. A 3000 Å thick silicon nitride passivation layer is formed by deposition above 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.

[0060] Step 2: Fabricate the dielectric layer 51 and the electrode layer 52: Form a layer of dielectric layer 51 above the first passivation layer 41, and form the interdigital electrode 521 and the heating resistor 522 on the dielectric layer 51 by the lift-off process. The more detailed steps are as follows:

[0061] Please refer to Figure 5 , a 1 thick silicon oxynitride dielectric layer 51 is formed by deposition on the first passivation layer 41. The lift-off process mainly is: Please refer to Figure 7 , titanium metal is sputtered with a patterned photoresist as a mask (the photoresist mask 01 in the figure), and the photoresist is stripped to form a 1 thick interdigital electrode 521 and heating resistor 522. Please refer to Figure 8Optionally, the electrode layer material can be selected from common metals or semiconductor materials in CMOS processes such as aluminum, titanium, tungsten, copper, nickel, tantalum, polycrystalline germanium silicon, etc. As an example, titanium metal is selected in this embodiment. The lift-off process can simplify the process flow, and forming the first passivation layer 41 by deposition allows for more flexible selection of the metal shielding layer 31 material.

[0062] Step 3: Etch the dielectric layer 51. Using this titanium metal (electrode layer 52) as a patterning template, etch the silicon oxynitride dielectric layer 51, and then form a thin passivation layer on the surface of the exposed electrode layer 52 as the second passivation layer 53. 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, since 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. The more detailed steps are as follows: Use this titanium metal as a patterning mask to etch silicon oxynitride to form the electrode layer 52. Please refer to Figure 9 Then deposit a 1000-angstrom-thick silicon nitride thin film passivation layer as the second passivation layer 53. Please refer to Figure 14 。

[0063] Step 4: Coat a humidity-sensitive material above the second passivation layer 53 of the electrode layer 52. The humidity-sensitive material fills the inside of the dielectric layer 51, as well as the inside and above the second passivation layer 53, to obtain the high-sensitivity MEMS humidity sensor of this embodiment. Please refer to Figure 15 Optionally, the humidity-sensitive material can be selected from polymer or porous dielectric materials. The polymer can be any one of polyimide, polystyrene, fluorinated polyimide, photoresist, and polydimethylsiloxane. As an example, polystyrene is selected as the humidity-sensitive material in this embodiment. More specifically, in this embodiment, the humidity-sensitive material polystyrene is spin-coated to form the sensing layer 61, and the thickness of the polystyrene above the interdigital electrode 521 is 1 。

[0064] Embodiment III

[0065] The device structure of Embodiment III is the same as that of Embodiment I, with only differences in the manufacturing process or materials used, especially in the process of fabricating the electrode layer 52, where an electroplating process is adopted. A manufacturing method of a high-sensitivity MEMS humidity sensor provided by Embodiment III. Please refer to Figure 3 、 Figure 4 、 Figure 12 、 Figure 13 、 Figure 9 、 Figure 14 、 Figure 15 , including the following steps:

[0066] Step 1: Fabricate the support base layer 11, insulating layer 21, metal shielding layer 31 and first passivation layer 41: Prepare a support base layer 11 with an insulating layer 21, form a layer of metal shielding layer 31 above the insulating layer 21 of the support base layer 11, and form a thin passivation layer on the surface of the metal shielding layer 31 as the first passivation layer 41. Optionally, the material used for the metal shielding layer 31 can be common metals or semiconductor materials 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, in this embodiment, copper metal is selected, and the first passivation layer 41 is formed by depositing a passivation layer. The more detailed steps are as follows:

[0067] Please refer to Figure 3 and Figure 4 , the support base layer 11 has an insulating layer 21 thereon, and a 0.1 -thick copper metal is formed as the metal shielding layer 31 by electroplating. The metal shielding layer 31 does not form a loop and is grounded. A 100-angstrom-thick silicon nitride passivation layer is formed by deposition above 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.

[0068] Step 2: Fabricate the dielectric layer 51 and electrode layer 52: Form a layer of dielectric layer 51 above the first passivation layer 41, etch the dielectric layer 51 to form trenches, and fill the trenches with electrodes to form an electrode layer 52 with interdigital electrodes 521. Optionally, the electrode layer 52 can be formed by sputtering or depositing metal in the trenches. As an example, in this embodiment, the sputtering process is used. The more detailed steps are as follows:

[0069] Please refer to Figure 12 , a 1.5 -thick silicon oxynitride dielectric layer 51 is formed by deposition on the first passivation layer 41. A 0.1 -deep patterned trench is formed on the dielectric by photolithography, and then the trenches are filled with metal or semiconductor materials by electroplating to form interdigital electrodes 521 and heating resistors 522. Please refer to Figure 13 . Optionally, the electrode layer material can be selected from common metals or semiconductor materials in CMOS processes such as aluminum, titanium, tungsten, copper, nickel, tantalum, polycrystalline germanium silicon, etc. As an example, in this embodiment, the electrode layer material is copper metal.

[0070] Step 3: Etch the dielectric layer 51, and then form a thin passivation layer on the surface of the exposed electrode layer 52 as the second passivation layer 53; 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 a metal. In this embodiment, since 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. The more detailed steps are as follows: Subsequently, etch the silicon oxynitride dielectric layer using the copper metal as a patterning mask to form the electrode layer 52, and remove the dielectric not covered by the electrode layer 52. Please refer to Figure 9 . Then deposit a 100 Å thick silicon nitride thin film passivation layer as the second passivation layer 53. Please refer to Figure 14 .

[0071] Step 4: Coat a humidity-sensitive material above the second passivation layer 53 of the electrode layer 52. The humidity-sensitive material forms a filling inside the dielectric layer 51, as well as inside and above the second passivation layer 53, to obtain the high-sensitivity MEMS humidity sensor of this embodiment. Please refer to Figure 15 . Optionally, the humidity-sensitive material can be selected from polymer or porous medium materials. The polymer can be any one of polyimide, polystyrene, fluorinated polyimide, photoresist, and polydimethylsiloxane. As an example, the humidity-sensitive material in this embodiment is fluorinated polyimide. More specifically, in this embodiment, a sensing layer 61 is formed by spin-coating the humidity-sensitive material fluorinated polyimide. The thickness of the fluorinated polyimide above the interdigital electrode 521 is 3 .

[0072] For the key structural layers in the above Embodiments 1 to 3, the selections of the material itself, size, and process parameters are as shown in Tables 1 to 3 below.

[0073] Table 1: Parameters of the key structural layers in Embodiment 1

[0074]

[0075] Table 2: Parameters of the key structural layers in Embodiment 2

[0076]

[0077] Table 3: Parameters of the key structural layers in Embodiment 3

[0078]

[0079] In summary, through the above embodiments, the present invention provides a metal shielding layer under the interdigital electrodes to isolate the parasitic capacitance interference from below the shielding electrodes, and a humidity-sensitive material is filled between the metal shielding electrodes and the interdigital electrodes to form an additional humidity sensing layer. This humidity sensing layer converts the parasitic capacitance in this area into a sensing capacitance. Therefore, the sensitivity of the sensor is greatly improved, and the metal of the electrode layer is passivated, playing an insulating and protective 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 common processes and materials in the CMOS process, and can be realized during the CMOS metallization process. Therefore, the compatibility with the CMOS process is very high.

[0080] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0081] The above embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended 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; The electrode layer has planar interdigitated electrodes; 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.

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: 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 0.1μm to 0.5μm; the thickness of the first passivation layer is 100 angstroms to 3000 angstroms; the thickness of the dielectric layer is 0.5μm to 1.5μm; the thickness of the electrode layer is 0.1μm to 1μm; the thickness of the second passivation layer is 100 angstroms to 1000 angstroms; the thickness of the portion of the sensing layer located above the electrode layer in the sensing layer is 1μm to 3μm.

8. 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.

9. A high-sensitivity MEMS hygrometer, obtained by the manufacturing method according to any one of claims 1 to 8, 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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