Absolute humidity sensor and preparation method thereof

Abstract

The invention discloses an absolute humidity sensor and a preparation method thereof. The sensor comprises a substrate, a cap and a substrate, the cap covers one end face of the substrate, and the base is fixedly arranged on the end face of the side, facing the cap, of the substrate. The cap and the base enclose to form a sealed cavity; the two side faces of the substrate are recessed inwards to form grooves, supporting films are arranged at openings of the grooves in the two sides of the substrate respectively, and thermistor films are arranged on the supporting films. The supporting film is provided with a plurality of supporting arms extending outwards, and the tail ends of the supporting arms are fixed to the end face of the base. The substrate is of a double-face symmetrical structure. The end face, facing the base, of the base plate is provided with an inwards-concave receding groove, the position, opposite to the groove, of the base plate is provided with a vent hole, and the vent hole is communicated with the groove, close to one side of the base plate, of the base plate. The sensor is provided with the single cavity and the substrate with the symmetrical structure, so that the measurement precision and the temperature interference resistance are improved; moreover, the size of the sensor is reduced, the processing and manufacturing cost is saved, and the production efficiency and the product consistency are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and in particular to an absolute humidity sensor and a preparation method thereof. Background Art

[0002] Absolute humidity sensors are currently widely used in multiple fields to detect the true degree of dryness in a specific environment. Generally, an absolute humidity sensor mainly consists of two thermistor elements with the same physical properties. By detecting the resistance values of the two thermistors, the change value of the open thermistor compared to the closed thermistor is obtained to calculate the absolute humidity in the environment. However, it is difficult for the two thermistor elements to exist in exactly the same temperature field, and the resistance change amplitudes caused by the influence of the ambient temperature are not exactly the same, which leads to problems such as low precision, large interference, and poor stability of the sensor. In addition, the two thermistor elements are often separately manufactured to obtain two sensitive probes, resulting in problems such as large volume, high manufacturing cost, complex processes, and poor product consistency after device packaging. Therefore, the humidity sensors in the existing technical methods have the problem of poor detection accuracy. Summary of the Invention

[0003] Embodiments of the present invention provide an absolute humidity sensor and a preparation method thereof, aiming to solve the problem of poor detection accuracy of the humidity sensors in the existing technical methods.

[0004] In a first aspect, an embodiment of the present application provides an absolute humidity sensor, which includes a substrate, a cap, and a base; The cap covers one end face of the substrate, and the base is fixedly arranged on the end face of the substrate facing the cap; a sealed chamber is formed by enclosing the cap and the base; Both side faces of the base are respectively recessed inward to form grooves, support membranes are respectively arranged at the openings of the grooves on both sides of the base, and thermistor films are arranged on the support membranes; the support membranes are provided with a plurality of arms extending outward, and the ends of the arms are fixed on the end face of the base; the base is a double-sided symmetric structure; The end face of the substrate facing the base is recessed inward to form an avoidance groove, and a ventilation hole is arranged at a position of the substrate opposite to the groove, and the ventilation hole is communicated with the groove on the side of the base close to the substrate.

[0005] For the absolute humidity sensor described above, the support membrane is a single-layer SiO2, single-layer Si3N4, or single-layer SiN x , or a composite film layer formed by combining at least two of the film layers of SiO2, Si3N4, and SiN x .

[0006] The absolute humidity sensor described above, wherein the thermistor film is a metal film composed of one or more of Pt, Ni, Ag, and Al.

[0007] The absolute humidity sensor described above, wherein the vent hole is a single through hole or a through hole array; the vent array is composed of a plurality of through holes arranged in a matrix.

[0008] The absolute humidity sensor described above, wherein the outer contour projection of the vent hole is larger than the contour of the suspended support film at the opening of the groove and smaller than the outer contour of the substrate.

[0009] The absolute humidity sensor described above, wherein the cross-section of the groove is an inverted trapezoidal geometric structure.

[0010] The absolute humidity sensor described above, wherein the material of the cap is cold-rolled steel, stainless steel, kovar alloy or aluminum.

[0011] The absolute humidity sensor described above, wherein the substrate is a single-crystalline silicon substrate or an SOI silicon wafer substrate.

[0012] The absolute humidity sensor described above, wherein the material of the substrate plate is a high-temperature ceramic plate, a glass plate or a silicon substrate.

[0013] In a second aspect, an embodiment of the present application further provides a method for manufacturing an absolute humidity sensor. The manufacturing method is used to manufacture the absolute humidity sensor described in the first aspect above. The manufacturing method includes: Select a wafer with a suitable size to make the substrate; Deposit a film on the end face of the substrate through a semiconductor coating process to form the support film; Deposit a thermistor material on the surface layer of the support film formed by coating, and fabricate the thermistor film through photolithography and stripping processes; Etch the substrate with the thermistor film using a dry etching process and a wet etching process with TMAH or KOH to form a sensitive chip with a single-sided groove or a sensitive chip with a double-sided groove; Perform silicon-silicon bonding on two sensitive chips with single-sided grooves so that the bottoms of the substrates of the two sensitive chips are combined to form an integrated chip; Fasten and attach the bonded integrated chip or the sensitive chip with a double-sided groove to the substrate and perform a fixed edge sealing process so that the center of the avoidance groove of the substrate is aligned with the center of the thermistor film; Fasten the cap to the end face of the substrate where the chip is disposed and seal it to obtain the absolute humidity sensor.

[0014] An embodiment of the present invention provides an absolute humidity sensor and a preparation method thereof. The sensor includes a substrate, a cap, and a base; the cap is covered on one end face of the substrate, and the base is fixedly arranged on the end face of the substrate facing the cap; the cap and the base enclose a sealed chamber; grooves are respectively recessed inwardly on both side faces of the base, support membranes are respectively arranged at the openings of the grooves on both sides of the base, and thermistor films are arranged on the support membranes; the support membranes are provided with a plurality of arms extending outwardly, and the ends of the arms are fixed on the end face of the base; the base has a double-sided symmetric structure; the end face of the substrate facing the base is provided with a recessed avoidance groove, and a ventilation hole is arranged at a position of the substrate opposite to the groove, and the ventilation hole is communicated with the groove on the side of the base close to the substrate. The above-mentioned sensor is provided with a single chamber and a base with a symmetric structure to improve the measurement accuracy and anti-temperature interference; and reduces the volume of the sensor, saves the processing and manufacturing cost, and improves the production efficiency and product consistency. Description of the Drawings

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0016] Figure 1 Overall structure diagram of the absolute humidity sensor provided by the embodiment of the present invention; Figure 2 Exploded structure diagram of the absolute humidity sensor provided by the embodiment of the present invention; Figure 3 Another exploded structure diagram of the absolute humidity sensor provided by the embodiment of the present invention; Figure 4 Cross-sectional structure diagram of the absolute humidity sensor provided by the embodiment of the present invention; Figure 5 Another cross-sectional structure diagram of the absolute humidity sensor provided by the embodiment of the present invention; Figure 6 Flow chart of the preparation method of the absolute humidity sensor provided by the embodiment of the present invention; Reference numerals: 1. Substrate; 2. Cap; 3. Sealed chamber; 4. Ventilation hole; 5. Base; 6. Groove; 7. Support membrane; 8. Thermistor film; 9. Avoidance groove. Detailed Embodiments

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to 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. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0018] It should be understood that when used in this specification and the appended claims, the terms "comprises" and "comprising" indicate the presence of the described features, wholes, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or their combinations.

[0019] It should also be understood that the terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include the plural forms. It should be further understood that the term " / and / " used in the specification of the present invention and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0020] Please refer to Figure 1 , as shown in the figure, an absolute humidity sensor, wherein the absolute humidity sensor includes a substrate 1, a cap 2 and a base 5; the cap 2 covers one end face of the substrate 1, and the base 5 is fixedly arranged on the end face of the substrate 1 on the side facing the cap 2; the cap 2 and the base 5 enclose a sealed chamber 3; both side faces of the base 5 are recessed inward to form grooves 6, and support membranes 7 are respectively arranged at the openings of the grooves 6 on both sides of the base 5, and thermistor films 8 are arranged on the support membranes 7; the support membranes 7 are provided with a plurality of arms extending outward, and the ends of the arms are fixed on the end face of the base 5; the base 5 has a double-sided symmetric structure; the end face of the substrate 1 facing the base 5 is provided with a recessed avoidance groove 9, and a ventilation hole 4 is arranged at a position of the substrate 1 opposite to the groove 6, and the ventilation hole 4 is communicated with the groove 6 on the side of the base 5 close to the substrate 1.

[0021] A ventilation hole 4 is arranged on the substrate 1, and the position where the ventilation hole 4 is arranged corresponds to the avoidance groove 9; a thermistor film 8 is deposited at the central position of the support membrane 7. The base 5 can be formed by silicon-silicon bonding two silicon substrate materials with single-sided grooves 6 so that the two silicon substrate materials are "back-to-back" bonded and combined to form an integrated silicon-based base 5. The specific structure is as Figure 2 and Figure 4As shown; silicon-silicon bonding processing is to bond two components both made of silicon materials. This process involves bonding two parts of silicon materials, that is, "silicon-silicon" bonding. The substrate 5 can also be a silicon-based substrate 5 with double-sided grooves 6 obtained by direct etching. The specific structure is as Figure 3 and Figure 5 shown. The substrate 5 is fixedly arranged on the substrate 1, and the substrate 5 and the cap 2 are arranged on the same end face of the substrate 1. The groove 6 of the substrate 5 is facing the vent hole 4 and the avoidance groove 9. The substrate 5 is accurately attached and the die bonding process is carried out; the side of the cap 2 facing the substrate 5 is recessed inward, and the cap 2 is buckled on the substrate 1 and then sealed.

[0022] Among them, the substrate 5 is a silicon-based material. Two silicon substrates 1 with single-sided grooves 6 can be "back-to-back" attached through semiconductor bonding technology. The substrate 5 is attached and die bonded on the substrate 1, so that a sealed chamber 3 is formed between the substrate 5 and the cap 2. The specific structure of the obtained device is as Figure 2 and Figure 4 shown. Using a silicon-based substrate 5 with double-sided grooves 6 obtained by direct etching, the silicon-based substrate 5 with double-sided grooves 6 is directly attached and die bonded on the substrate 1, and a sealed chamber 3 is also formed. The specific structure of the obtained device is as Figure 3 and Figure 5 shown.

[0023] Furthermore, the setting position of the vent hole 4 corresponds to the avoidance groove 9. By setting the avoidance groove 9, it can prevent the support film 7 and the thermistor film 8 from cracking during manufacturing and sensor operation.

[0024] By setting a single sealed chamber 3 and a substrate 5 with a symmetric structure (the substrate 5 is symmetric along the horizontal center line), the grooves 6 on both sides of the substrate 5 are not connected; then two thermistor films 8 (thermistor elements) with the same physical properties are arranged on both sides of the substrate 5, and it is ensured that the two thermistor films 8 are in exactly the same temperature field; among them, the thermistor film 8 located in the sealed chamber 3 senses the change signal of the thermal conductivity of dry air in the sealed environment, and the thermistor film 8 on one side of the vent hole 4 senses the change signal of the thermal conductivity of air containing water vapor in the environment. The two signals are collected and processed by the signal acquisition and processing circuit, so as to obtain the corresponding absolute humidity data. Specifically, two thermistor films 8 with the same physical properties can be combined with a fixed-value resistor to form a Wheatstone bridge and connected to a CMOS microprocessor, thus forming a humidity signal acquisition circuit; when detecting the absolute humidity of the environment, since the enclosed thermistor element is in dry air, its resistance is only affected by the environmental temperature; and the two thermistor elements are in the same temperature environment, so the collected humidity signal is only affected by the water vapor content in the environment. The change of the humidity signal can directly reflect the change of the water vapor content in the environment, and further achieve the purpose of quickly and accurately measuring the absolute humidity of the environment.

[0025] Since the two thermistor films 8 are in the same temperature field, the amplitude of the resistance change generated can be ensured to be almost the same when detecting temperature changes in the environment, thereby ensuring that the absolute humidity sensor has the characteristics of high precision, strong resistance to temperature interference, and high stability.

[0026] The support film 7 is suspended at the opening of the groove 6, and the support film 7 is fixed to the end face of the substrate 5 through a support arm; the support film 7 can be circular, rectangular or triangular, and there can be one or more support arms. The material of the cap 2 can be one of cold-rolled steel, stainless steel, kovar alloy, and aluminum metal.

[0027] In a more specific embodiment, the support film 7 is a single layer of SiO2, a single layer of Si3N4 or a single layer of SiN x , or a composite film layer formed by combining at least two of the film layers of SiO2, Si3N4 and SiN x . Among them, the thermistor film 8 is a metal film composed of one or more of Pt, Ni, Ag, and Al.

[0028] Specifically, the support film 7 can be a single layer of SiO2 or a single layer of Si3N4, or a single layer of SiN x ; it can also be a composite film layer composed of SiO2, Si3N4 and SiN x , and the composite film layer includes at least two of the film layers of SiO2, Si3N4 and SiN x . The thermistor film 8 is a metal film composed of one of Pt, Ni, Ag, and Al, or an alloy metal film formed by combining multiple metals among Pt, Ni, Ag, and Al.

[0029] In a more specific embodiment, the ventilation hole 4 is a single through hole or a through hole array; the through hole array is composed of a plurality of through holes arranged in a matrix. Specifically, the outer contour projection of the ventilation hole 4 is larger than the contour of the suspended support film 7 at the opening of the groove 6 and smaller than the outer contour of the substrate 5. Among them, the outer contour of the ventilation hole 4 is rectangular, and the cross section of the groove 6 is an inverted trapezoidal geometric structure.

[0030] The ventilation hole 4 can be just a single through hole, or the ventilation hole 4 can be a through hole array, and the through hole array is composed of a plurality of through holes arranged in a matrix, as shown in Figures 1-3 . The coverage area of the ventilation hole 4 is slightly larger than the contour size of the suspended support film 7 at the opening of the groove 6 and smaller than the outer contour size of the substrate 5; that is, the outer contour projection of the ventilation hole 4 is larger than the contour of the suspended support film 7 at the opening of the groove 6 and smaller than the outer contour of the substrate 5.

[0031] The outer contour of the vent hole 4 can be set as a rectangle, and similarly, the groove 6 can be set as a rectangular groove 6. In a more specific embodiment, the size of the opening of the groove 6 is larger than the size of the bottom surface of the groove 6. By setting the size of the opening of the groove 6 to be larger than the size of the bottom surface of the groove 6, the transverse cross-section and the longitudinal cross-section of the groove 6 are both in an inverted trapezoidal geometric structure.

[0032] In a more specific embodiment, the substrate 5 is a single-crystalline silicon substrate or an SOI silicon wafer substrate. Among them, the material of the substrate 1 is a high-temperature ceramic plate, a glass plate or a silicon substrate 1.

[0033] The substrate 5 can be a single-crystalline silicon substrate or an SOI silicon wafer substrate, and the material of the substrate 1 can be a high-temperature ceramic plate resistant to high temperatures, or a glass plate or a silicon substrate 1.

[0034] An embodiment of the present invention further provides a method for manufacturing an absolute humidity sensor. This manufacturing method can be used to manufacture the absolute humidity sensor described in the above embodiments, such as Figure 6 as shown, this manufacturing method includes steps S1 - S7.

[0035] S1. Select a wafer with a suitable size to fabricate the substrate.

[0036] First, select a wafer with a suitable size to fabricate the substrate.

[0037] S2. Deposit a film on the end face of the substrate through a semiconductor film coating process to form the support film.

[0038] Deposit a film on the end face of the substrate through a semiconductor film coating process, thereby obtaining the corresponding support film.

[0039] S3. Deposit a thermistor material on the surface layer of the support film formed by film coating, and fabricate the thermistor film through photolithography and lift-off processes.

[0040] First, apply a negative photoresist evenly on the surface layer of the support film for photolithography, and then deposit a thermistor material on the surface layer of the support film. The thermistor material can be a metal material such as Pt, Ni, Ag, Al, etc. Finally, fabricate the thermistor film through a lift-off process. Steps S2 and S3 can be operated on one side of the substrate, or can be operated simultaneously on both sides of the substrate.

[0041] S4. Etch the substrate with the thermistor film using a dry etching process and a wet etching process with TMAH or KOH to form a sensitive chip with a single-sided groove or a sensitive chip with double-sided grooves.

[0042] The support film is further etched by a dry process to form a wet etching window for the next step of grooves. Then, the substrate material under the support film is etched by a wet etching process, so as to form grooves under the support film. Here, only one side of the substrate can be etched (the support film and the thermistor film are coated on only one side of the substrate), so as to form a sensitive chip with single-sided grooves; or both sides of the substrate can be etched simultaneously (the support film and the thermistor film are coated on both sides of the substrate), so as to obtain a sensitive chip with double-sided grooves.

[0043] S5. Two sensitive chips with single-sided grooves are processed by silicon-silicon bonding, so that the bottoms of the substrates of the two sensitive chips are combined to form an integrated chip.

[0044] If only one side of the substrate is etched, the sensitive chips with single-sided grooves can be processed by silicon-silicon bonding. This process is to combine the bottoms of the substrates of the two sensitive chips, that is, to bond the two sensitive chips "back to back", so as to obtain an integrated chip. If both sides of the substrate are etched, step S5 is not required.

[0045] S6. The bonded integrated chip or the sensitive chip with double-sided grooves is buckled and attached to the substrate and fixed and edge-sealed, so that the center of the avoidance groove of the substrate is aligned with the center of the thermistor film.

[0046] The integrated chip or the sensitive chip with double-sided grooves is buckled and attached to the substrate. At this time, the sensitive chip is attached to the end face of the substrate provided with the avoidance groove, and the center of the avoidance groove of the substrate is aligned with the center of the thermistor film. The integrated chip or the sensitive chip is fixed and edge-sealed, so that the chip is firmly fixed on the substrate and the edge of the chip is kept sealed.

[0047] S7. A cap is buckled on the end face of the substrate provided with the chip and sealed to obtain the absolute humidity sensor.

[0048] The cap is further buckled on the end face of the substrate provided with the chip, and the contact surface between the cap and the substrate is also sealed, so as to form a sealed cavity between the cap and the substrate, and finally obtain the absolute humidity sensor.

[0049] Most of the absolute humidity sensors in the prior art adopt the form of separate packaging of two components, which have problems such as large sensor volume, high manufacturing cost, complex processes and poor product consistency. However, the preparation method in the present application only needs to fix and assemble the chip on the substrate, and the corresponding sensor product can be prepared by one-time packaging, reducing the required steps for preparation and saving the manufacturing and processing cost. This preparation method increases the integration degree of the sensitive components, reduces the preparation and processing procedures, improves the production efficiency and product consistency, and avoids the change of the internal structure of the device affecting the measurement accuracy.

[0050] An embodiment of the present invention provides an absolute humidity sensor and a preparation method thereof. The sensor includes a substrate, a cap, and a base; the cap is covered on one end face of the substrate, and the base is fixedly arranged on the end face of the substrate facing the cap; the cap and the base enclose a sealed chamber; grooves are respectively formed by inward recesses on both side faces of the base, support membranes are respectively arranged at the openings of the grooves on both sides of the base, and thermistor membranes are arranged on the support membranes; the support membranes are provided with a plurality of arms extending outward, and the ends of the arms are fixed on the end face of the base; the base is a double-sided symmetric structure; the end face of the substrate facing the base is provided with an inward recessed avoidance groove, and a ventilation hole is arranged at a position of the substrate opposite to the groove, and the ventilation hole is communicated with the groove on the side of the base close to the substrate. The above-mentioned sensor is provided with a single chamber and a symmetrically structured base to improve the measurement accuracy and anti-temperature interference; and reduces the volume of the sensor, saves the processing and manufacturing cost, and improves the production efficiency and product consistency.

[0051] As described above, the above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. An absolute humidity sensor, characterized in that, It includes a substrate, a cap and a base; The cap is covered on one end face of the substrate, and the base is fixedly arranged on the end face of the substrate facing the cap; a sealed chamber is formed by enclosing the cap and the base; Both side faces of the base are respectively recessed inward to form grooves, support membranes are respectively arranged at the openings of the grooves on both sides of the base, and thermistor films are arranged on the support membranes; the support membranes are provided with a plurality of arms extending outward, and the ends of the arms are fixed on the end face of the base; the base is a double-sided symmetric structure; The end face of the substrate facing the base is provided with a recessed avoidance groove, and a ventilation hole is arranged at a position of the substrate opposite to the groove, and the ventilation hole is communicated with the groove on the side of the base close to the substrate.

2. The absolute humidity sensor according to claim 1, characterized in that, The support film is a single-layer SiO2, single-layer Si3N4 or single-layer SiN x , or a composite film layer formed by combining at least two of the film layers of SiO2, Si3N4 and SiN x .

3. The absolute humidity sensor according to claim 2, characterized in that, The thermistor film is a metal film composed of one or more of Pt, Ni, Ag, and Al.

4. The absolute humidity sensor according to claim 1, characterized in that, The ventilation hole is a single through hole or a through hole array; the through hole array is composed of a plurality of through holes arranged in a matrix.

5. The absolute humidity sensor according to claim 4, characterized in that, The outer contour projection of the ventilation hole is larger than the contour of the suspended support membrane at the opening of the groove and smaller than the outer contour of the base.

6. The absolute humidity sensor according to any one of claims 1-5, characterized in that, The cross section of the groove is an inverted trapezoid geometric structure.

7. The absolute humidity sensor according to claim 6, characterized in that, The material of the cap is cold-rolled steel, stainless steel, kovar alloy or aluminum.

8. The absolute humidity sensor according to claim 7, characterized in that, The base is a single-crystal silicon substrate or an SOI silicon wafer substrate.

9. The absolute humidity sensor according to claim 8, characterized in that, The material of the substrate is a high-temperature ceramic plate, a glass plate or a silicon substrate.

10. A method for preparing an absolute humidity sensor, the preparation method being used to manufacture the absolute humidity sensor according to any one of claims 1-9, characterized in that, The preparation method includes: Select a wafer with appropriate size to make the base; Deposit a film on the end face of the base through a semiconductor coating process to form the support membrane; Deposit thermistor material on the surface layer of the support membrane formed by coating, and fabricate the thermistor film through photolithography and stripping processes; Etch the base with the thermistor film by using a dry etching process and a wet etching process with TMAH or KOH to form a sensitive chip with a single-sided groove or a sensitive chip with double-sided grooves; Perform silicon-silicon bonding on two sensitive chips with single-sided grooves so that the bottoms of the bases of the two sensitive chips are combined to form an integrated chip; Fasten and attach the above-mentioned bonded integrated chip or the sensitive chip with double-sided grooves to the substrate and perform fixed edge sealing treatment so that the center of the avoidance groove of the substrate is aligned with the center of the thermistor film; Fasten the cap on the end face of the substrate provided with the chip and seal it to obtain the absolute humidity sensor.

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