CN114894856B

CN114894856B - MEMS gas sensor based on wafer level packaging and manufacturing method thereof

Info

Publication number: CN114894856B
Application number: CN202210473821.1A
Authority: CN
Inventors: 王琛; 张思勉; 邓晓楠; 柯声贤; 李正操
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2022-04-29
Filing date: 2022-04-29
Publication date: 2024-04-23
Anticipated expiration: 2042-04-29
Also published as: CN114894856A

Abstract

The present disclosure relates to a wafer-level package-based MEMS gas sensor and a method of manufacturing the same. The sensor comprises: the dielectric layer covers the first surface of the first substrate; each through silicon via penetrates through the first substrate and the dielectric layer; the first insulating layer covers the second surface of the first substrate and exposes each through silicon via; each electrode is positioned on the second surface of the first substrate and connected with the through silicon via; the heating electrode of the sensor main body is arranged on the dielectric layer and connected with the corresponding silicon through hole, and the second insulating layer at least covers the heating electrode; the test electrode is above the second insulating layer, and the target area is overlapped with the heating electrode and is covered on the target area by being connected to the corresponding through silicon vias and the gas sensitive material layer; the second substrate of the cap layer is provided with a containing groove for containing at least part of the sensor main body and a vent hole connected with the containing groove; the bonding ring of the cap layer fixedly connects the base body and the cap layer. The manufactured sensor has the advantages of good impact resistance, good pollution resistance, low cost, good uniformity and high industrial production efficiency.

Description

MEMS gas sensor based on wafer level packaging and manufacturing method thereof

Technical Field

The disclosure relates to the technical field of integrated circuit packaging, in particular to a wafer-level packaging-based MEMS gas sensor and a manufacturing method thereof.

Background

With the continuous development of AI technology and intelligent equipment, gas sensors have been developed in great extent as important media for sensing environment, and are widely applied to important fields such as environment, medical treatment, chemical industry, national defense, etc., and become one of important directions for the development of microelectronic devices. With the continuous progress of micro-nano processing technology, gas sensors are also gradually moving to advanced degree and miniaturization.

As the level of fabrication increases, microelectromechanical systems (Micro Electro MECHANICAL SYSTEM, MEMS) technology is increasingly being applied in the field of gas sensors. Compared with the traditional sensor, the MEMS sensor has smaller volume, lighter weight, lower power consumption and lower cost, and is more suitable for integration on intelligent equipment and wearable equipment. Therefore, MEMS gas sensors are becoming one of the important directions in this field.

While pushing MEMS gas sensors to high integration and small size, miniaturization also leads to the following problems with MEMS gas sensors: the distance between the test area and the electrode area is reduced, and in some corrosive gas test environments, the metal electrode and the interconnection line are severely corroded due to long-term exposure to the environment, so that the service time of the sensor is greatly shortened.

In addition, miniaturization of devices places higher demands on bonding accuracy. In the related art, the single-device bonding process has low efficiency in production, is difficult to ensure the uniformity of bonding precision, and is not beneficial to industrial production.

Therefore, how to provide a MEMS gas sensor and a method for manufacturing the same that can solve the above problems is a highly desirable problem.

Disclosure of Invention

In view of this, the present disclosure proposes a MEMS gas sensor based on wafer level packaging and a method of manufacturing the same.

According to an aspect of the present disclosure, there is provided a MEMS gas sensor based on wafer level packaging, the sensor comprising: the sensor comprises a substrate, a sensor main body for detecting external gas, a cap layer and a plurality of electrodes;

The substrate comprises: the semiconductor device comprises a first substrate, a dielectric layer, a first insulating layer and a plurality of silicon through holes, wherein the dielectric layer covers at least part of the area of the first surface of the first substrate; each through silicon via penetrates through the first substrate and the dielectric layer; the first insulating layer covers the second surface of the first substrate and at least exposes the through hole area corresponding to each through silicon hole, and the first substrate comprises a silicon substrate;

Each electrode is arranged in the corresponding through hole area and is electrically connected with the corresponding through silicon hole;

The sensor main body comprises a heating electrode, a second insulating layer, a testing electrode and a gas-sensitive material layer, wherein the heating electrode is positioned above the dielectric layer and connected with each corresponding silicon through hole; the second insulating layer is positioned above the dielectric layer and at least covers the heating electrode; the test electrode is positioned above the second insulating layer, the target area is overlapped with the heating electrode, and the test electrode is connected to each corresponding through silicon via through holes in the second insulating layer; the gas sensitive material layer is positioned above the second insulating layer and covers the target area of the test electrode;

The cap layer comprises a second substrate and a bonding ring, wherein a first surface of the second substrate is provided with a containing groove, and at least part of the sensor main body is positioned in the containing groove; the second surface of the second substrate is provided with a vent hole which is connected with the accommodating groove and the position of which corresponds to the target area; the bonding ring is arranged on the first surface of the second substrate and is used for closing and encircling the accommodating groove and fixedly connecting the base body and the cap layer together.

In one possible implementation, the cap layer further includes:

And the ventilation film layer is positioned above the second surface of the second substrate and at least covers the ventilation holes.

In one possible implementation, the cap layer further includes:

and the dustproof net layer is positioned on the second surface of the second substrate and at least covers the region of the breathable film layer corresponding to the vent holes, and a plurality of through holes are formed in the part of the dustproof net layer corresponding to the vent holes.

In one possible implementation, the dielectric layer covers an area of the first face of the first substrate corresponding to the accommodating recess and the second insulating layer also covers at most the exposed dielectric layer, the bonding ring being fixedly connected to the first face of the first substrate such that the base body and the cap layer are fixedly connected together, the sensor body and the dielectric layer being located within the accommodating recess; or alternatively

The dielectric layer covers the whole area of the first surface of the first substrate, the second insulating layer also at most covers the exposed area of the dielectric layer, which corresponds to the accommodating groove, and the bonding ring is fixedly connected with the dielectric layer, so that the base body and the cap layer are fixedly connected together, and the sensor main body is positioned in the accommodating groove; or alternatively

The dielectric layer covers the whole area of the first surface of the first substrate, the second insulating layer also covers the whole area of the exposed dielectric layer, and the bonding ring is fixedly connected with the second insulating layer, so that the base body and the cap layer are fixedly connected together, and at least the gas-sensitive material layer in the sensor main body is positioned in the accommodating groove.

In one possible implementation, the shape of the heating electrode comprises a malleable shape including any of a serpentine shape, an S-shape; and/or

The test electrode comprises an interdigital electrode, the target area is a periodic pattern area of the interdigital electrode, and the ductile-shaped area of the heating electrode and the target area are matched in size and overlapped in position.

According to another aspect of the present disclosure, there is provided a method for manufacturing a MEMS gas sensor based on wafer level packaging, characterized in that it is used for manufacturing the above sensor, the method comprising: a base body manufacturing step, a sensor body manufacturing step, a cap layer manufacturing step, a fixed connection step, and an electrode manufacturing step,

The substrate manufacturing step includes: preparing a dielectric layer on a first surface of a first substrate; etching the first substrate and the dielectric layer, and thinning the first substrate to form a plurality of silicon through holes; preparing a first insulating layer on the second surface of the first substrate, and etching the first insulating layer to at least expose a through hole area corresponding to each silicon through hole to obtain a matrix of the sensor;

The sensor body manufacturing step includes: sequentially manufacturing a heating electrode and a second insulating layer above the dielectric layer, and enabling the second insulating layer to at least cover the heating electrode; etching the second insulating layer to expose a through silicon via for connecting with the test electrode; manufacturing a test electrode with a target area overlapped with the heating electrode on the second insulating layer, and connecting the test electrode with the through silicon via exposed by the second insulating layer; manufacturing a gas-sensitive material layer above the target area to obtain a sensor main body;

The cap layer manufacturing step includes: preparing a bonding ring on a first side of a second substrate; etching the second substrate to form a vent hole penetrating through the second substrate and corresponding to the target area; etching the first surface of the second substrate to form a containing groove connected with the vent hole, and obtaining a cap layer of the sensor;

and (3) fixedly connecting: fixedly connecting the bonding ring and the matrix together in a bonding mode so as to enable at least part of the sensor main body to be positioned in the accommodating groove;

Electrode manufacturing steps: and implanting balls in the through hole areas to form electrodes of the sensor, thereby completing the preparation of the sensor.

In one possible implementation, the capping layer manufacturing step further includes:

and attaching a prefabricated breathable film on the second surface of the second substrate and at least covering the vent holes to form a breathable film layer.

And preparing a dust screen layer above the breathable film layer to form the dust screen layer with a plurality of through holes at least covering part of the breathable film layer.

In one possible implementation manner, the bonding ring is fixedly connected with the substrate by a bonding mode, and the method comprises any one of the following steps:

If the dielectric layer covers the area of the first surface of the first substrate corresponding to the accommodating groove and the second insulating layer also covers at most the exposed dielectric layer, fixedly connecting the bonding ring with the first surface of the first substrate in a bonding manner so as to fixedly connect the base body and the cap layer together, and positioning the sensor body and the dielectric layer in the accommodating groove;

If the dielectric layer covers the whole area of the first surface of the first substrate and the second insulating layer also at most covers the exposed area of the dielectric layer corresponding to the accommodating groove, the bonding ring is fixedly connected with the dielectric layer in a bonding manner, so that the substrate and the cap layer are fixedly connected together, and the sensor main body is positioned in the accommodating groove;

If the dielectric layer covers the whole area of the first surface of the first substrate and the second insulating layer also covers the whole area of the exposed dielectric layer, the bonding ring is fixedly connected with the second insulating layer in a bonding manner, so that the base body and the cap layer are fixedly connected together, and at least the gas-sensitive material layer in the sensor main body is positioned in the accommodating groove.

The test electrode comprises an interdigital electrode, the target area is a periodic pattern area of the interdigital electrode, and the extensible shape area of the heating electrode is matched with the target area in size and overlapped in position; and/or

The gas-sensitive material layer is a self-assembled cluster of spherical gas-sensitive material.

According to the MEMS gas sensor based on wafer level packaging and the manufacturing method thereof, the manufactured sensor sensitive material area is separated from the interconnection line area, and the core structure of the sensor main body is protected, so that the impact resistance and pollution resistance of the sensor are enhanced, the manufacturing cost is reduced, the wafer level manufacturing process is better compatible, the packaging quality and the packaging precision uniformity are improved through the wafer level packaging technology, and the industrial production efficiency is improved.

Other features and aspects of the present disclosure will become apparent from the following detailed description of exemplary embodiments, which proceeds with reference to the accompanying drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments, features and aspects of the present disclosure and together with the description, serve to explain the principles of the disclosure.

Fig. 1A shows a schematic structural diagram of a wafer level package based MEMS gas sensor according to an embodiment of the present disclosure.

FIG. 1B illustrates a schematic cross-sectional view of a wafer level package based MEMS gas sensor in accordance with an embodiment of the present disclosure.

Fig. 2A shows a schematic structural diagram of a wafer level package based MEMS gas sensor according to an embodiment of the present disclosure.

Fig. 2B illustrates a schematic cross-sectional view of a wafer level package based MEMS gas sensor according to an embodiment of the present disclosure.

Fig. 3-5 illustrate schematic structural diagrams of a wafer level package based MEMS gas sensor according to an embodiment of the present disclosure.

Fig. 6 illustrates a schematic structure of a heating electrode according to an embodiment of the present disclosure.

Fig. 7 shows a schematic structural view of a test electrode according to an embodiment of the present disclosure.

Fig. 8 shows a schematic structural view of a gas-sensitive material layer according to an embodiment of the present disclosure.

FIG. 9 illustrates a schematic diagram of the relative positions of a heater electrode, a test electrode, and a layer of gas sensitive material according to an embodiment of the present disclosure.

Fig. 10 illustrates a top view of a cap layer according to one embodiment of the present disclosure.

Fig. 11 shows a flowchart of a method of manufacturing a wafer level package based MEMS gas sensor according to an embodiment of the present disclosure.

Fig. 12 illustrates a schematic diagram of a manufacturing process of a method of manufacturing a wafer level package based MEMS gas sensor according to an embodiment of the present disclosure.

Fig. 13 is a schematic view illustrating a process of fabricating a cap layer in a method of fabricating a wafer level package-based MEMS gas sensor according to an embodiment of the present disclosure.

Detailed Description

Various exemplary embodiments, features and aspects of the disclosure will be described in detail below with reference to the drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. Although various aspects of the embodiments are illustrated in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

The word "exemplary" is used herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

In addition, numerous specific details are set forth in the following detailed description in order to provide a better understanding of the present disclosure. It will be understood by those skilled in the art that the present disclosure may be practiced without some of these specific details. In some instances, methods, means, elements, and circuits well known to those skilled in the art have not been described in detail in order not to obscure the present disclosure.

In order to solve the technical problems, the embodiments of the present disclosure provide a MEMS gas sensor based on wafer level packaging and a method for manufacturing the same, where a sensor sensitive material area is separated from an interconnection line area, and a core structure of a sensor main body is protected, so that impact resistance and pollution resistance of the sensor are enhanced, manufacturing cost is reduced, wafer level manufacturing process is better compatible, packaging quality and uniformity of packaging precision are improved through wafer level packaging technology, and industrial production efficiency is improved.

Fig. 1A, 2A, 3-5 illustrate schematic structural diagrams of a wafer level package based MEMS gas sensor according to an embodiment of the present disclosure. Fig. 1B, 2B illustrate schematic cross-sectional views of a wafer level package based MEMS gas sensor according to an embodiment of the present disclosure. Fig. 1B and 2B are schematic cross-sectional views of any cross-section of the first insulating layer 16 parallel to the first surface of the first substrate 11. As shown in fig. 1A-3, the sensor includes: the sensor includes a base body, a sensor body for detecting an external gas, a cap layer, and a plurality of electrodes 41. The substrate may include: a first substrate 11, a dielectric layer 12, a first insulating layer 16, and a plurality of through silicon vias 15. The sensor body comprises a heating electrode 18, a second insulating layer 19, a test electrode 20 and a layer of gas sensitive material 21. The cap layer includes a second substrate 31 and a bond ring 32.

As shown in fig. 1A, 2A, and3, the substrate may include: a first substrate 11, a dielectric layer 12, a first insulating layer 16, and a plurality of through silicon vias 15. The dielectric layer 12 covers at least a part of the area of the first surface of the first substrate 11. Each through silicon via 15 penetrates through the first substrate 11 and the dielectric layer 12. The first insulating layer 16 covers the second surface of the first substrate 11 and exposes at least via regions 15' (as shown in fig. 1B) corresponding to the respective through-silicon vias 15.

In this embodiment, the dielectric layer is used to isolate the first substrate from the heating electrode in the sensor body, and the dielectric layer may be an ONO dielectric layer, and the ONO dielectric layer may be a silicon oxide (SiO ₂)/silicon nitride (SiN _x)/silicon oxide layer, and may be prepared by a process such as a plasma enhanced chemical Vapor Deposition (PLASMA ENHANCED CHEMICAL Vapor Deposition (PECVD). Since silicon nitride and silicon oxide have opposite thermal expansion characteristics, additional stress due to thermal expansion can be reduced in a high temperature process, so that the dielectric layer can be provided as an ONO dielectric layer. For example, as shown in fig. 5, the dielectric layer 12 may include a silicon oxide layer 121, a silicon nitride layer 122, and a silicon oxide layer 123. The through silicon vias 15 may have a diameter of 1 μm to 50 μm and an aspect ratio of 5:1 to 10:1. The material of the first insulating layer may be an insulating material such as silicon oxide, and the thickness of the first insulating layer may be 300nm to 1000nm. The materials and dimensions of the dielectric layer, the first insulating layer and the through silicon via can be set by those skilled in the art according to actual needs, and the disclosure is not limited thereto.

As shown in fig. 1A, 2A, and 3, each electrode 41 is disposed in the corresponding through hole region 15' and is electrically connected to the corresponding through silicon via 15.

In this embodiment, the electrode 41 may be a metal ball manufactured by a ball-implanting method such as laser ball-implanting, and the material of the metal ball may be lead-tin alloy (PbSn) or the like. As shown in fig. 2A, 2B, 3-5, the sensor may further comprise a metal electrodeposited layer 17. The metal electrode deposition layer 17 is located at each via region 15 'and covers each via region 15'. The material of the metal electrode deposition layer 17 may be a metal such as titanium (Ti), platinum (Pt), or gold (Au). The thickness of the metal electrode deposition layer 17 may be 550nm. The electrode 41 can be conveniently prepared in a ball implantation mode by the metal electrode deposition layer, so that the ball implantation is ensured to be carried out smoothly. Those skilled in the art may set the materials and dimensions of the metal electrode deposition layer and the electrode according to actual needs, and the present disclosure is not limited thereto.

As shown in fig. 1A, 2A, 3-5, the sensor body comprises a heating electrode 18, a second insulating layer 19, a test electrode 20, and a layer of gas sensitive material 21. The heater electrode 18 is located above the dielectric layer 12 and connected to each corresponding through silicon via 15. The second insulating layer 19 is located above the dielectric layer 12 and covers at least the heating electrode 18. The test electrode 20 is located above the second insulating layer 19 and the target area of the test electrode 20 overlaps the heating electrode 18 and is connected to the corresponding each through silicon via 15 through a via 191 in the second insulating layer 19. The layer of gas sensitive material 21 is located over the second insulating layer 19 and overlies the target area of the test electrode 20.

In this embodiment, the heating electrode 18 is used to generate heat when energized, and these heat can heat the gas-sensitive material layer 21 in the sensor main body, so as to adjust the temperature of the gas-sensitive material layer 21, so that the gas-sensitive material layer 21 is at the working temperature during the working process of the sensor, and ensure that the gas-sensitive material layer 21 can be specifically combined with gas molecules. The second insulating layer 19 serves to insulate the test electrode 20 and the heating electrode 18 so that the test electrode 20 and the heating electrode 18 are not communicated with each other. The material of the second insulating layer 19 may be an insulating material such as silicon oxide, silicon nitride, or the like, which is not limited in the present disclosure. The gas in the environment is different in kind and concentration, the specific combination of the gas sensitive material layer and the gas molecule is different, so that the resistance of the gas sensitive material layer 21 is different, a constant voltage is applied to the test electrode 20 in the monitoring process, and the current value flowing through the test electrode 20 is measured, and the detected current value of the test electrode 20 is changed due to the difference of the resistance of the gas sensitive material layer 21 caused by the specific combination of the gas molecule, so that the change of the resistance of the gas sensitive material layer 21 can be determined based on the change of the current value, and the kind and concentration of the gas combined with the gas sensitive material layer 21 can be further identified. The gas-sensitive material may be set according to the kind and concentration of the gas detection, which is not limited by the present disclosure.

Fig. 6 illustrates a schematic structure of a heating electrode according to an embodiment of the present disclosure. Fig. 7 shows a schematic structural view of a test electrode according to an embodiment of the present disclosure. Fig. 8 shows a schematic structural view of a gas-sensitive material layer according to an embodiment of the present disclosure. FIG. 9 illustrates a schematic diagram of the relative positions of a heater electrode, a test electrode, and a layer of gas sensitive material according to an embodiment of the present disclosure. Wherein the second insulating layer 19 is not shown in fig. 9 for more clearly illustrating the relative positional relationship of the heating electrode 18, the test electrode 20, and the gas-sensitive material layer 21 in space.

In one possible implementation, the shape of the heater electrode 18 may comprise a malleable shape, which may comprise a serpentine, S-shaped, etc. malleable shape as shown in fig. 6. In this way, the length of the heating electrode can be increased. The heating electrode 18 may include an ductile-shape region M1, a first connection region 181 for connecting the through-silicon via 15, and a first wire region 182 for realizing connection between the ductile-shape region M1 and the first connection region 181.

In one possible implementation, as shown in fig. 7, the test electrodes 20 may be interdigitated electrodes. The fingers of the interdigital electrodes which are not communicated with each other can be communicated through the gas-sensitive material layer 21 covered on the fingers. The test electrode 20 may include a periodic pattern region M2, a second connection region 201 for connecting the through silicon via 15, and a second wire region 202 for realizing connection between the periodic pattern region M2 and the second connection region 201. The target area may be a periodic pattern area M2.

Wherein the width w1 of the ductile shaped region M1 and the first wire region 182 in the heating electrode 18 is equal to the width w2 of the interdigital electrode (i.e., the width of the periodic pattern region M2 and the second connection region 201), i.e., w1=w2. The distance s1 between the strip-shaped metals in the ductile-shape region M1 is the same as the distance s2 between the fingers in the interdigitated electrodes (i.e., the distance between the strip-shaped metals in the periodic pattern region M2), i.e., s1=s2. And w1 and s1 may be equal. The malleable shape region M1 is the same size as the periodic pattern region M2. The number of cycles of the extendable shape area M1 and the periodic pattern area M2 may be the same, wherein the number of cycles of the extendable shape area M1 is 4 as shown in fig. 6, and the number of cycles of the periodic pattern area M2 is 4 as shown in fig. 7. The thickness of the heating electrode 18 and the thickness of the test electrode 20 may be the same, and the thickness may be 80nm to 150nm, for example, the thicknesses of the heating electrode 18 and the test electrode 20 are set to 110nm.

In this implementation, the materials of the heating electrode 18 and the test electrode 20 may be titanium (Ti), platinum (Pt), or the like, which is not limited by the present disclosure.

In one possible implementation, as shown in fig. 8, the layer of gas sensitive material 21 may be self-assembled clusters of spherical gas sensitive material 211. The size of the gas-sensitive material layer 21 may be slightly smaller than or equal to the size of the periodic pattern area M2, so that the gas-sensitive material layer 21 may completely cover the periodic pattern area M2, ensuring the electrical conduction of the sensor.

In the present embodiment, the dimensions of the gas-sensitive material layer 21, the test electrode 20, and the heating electrode 18 may be set according to the size setting requirements of the sensor. Assuming that the dimensions of the gas-sensitive material layer 21 are determined to be 100 μm×100 μm to 300 μm×300 μm according to the size setting of the sensor, s1, s2, w1, w2 may be 5 μm to 20 μm, and the lengths of the test electrode 20, the heater electrode 18 may be 35 μm to 380 μm. It will be appreciated by those skilled in the art that the dimensions, materials, etc. of the various parts of the sensor body may be set as desired, and this disclosure is not limited thereto.

In this embodiment, each through silicon via 15 is disposed below the first connection region 181 of the heating electrode 18 or the second connection region 201 of the test electrode 20, the filler metal in each through silicon via 15 contacts the heating electrode 18 or the test electrode 20 on the first surface of the first substrate 11, and the filler metal in the through silicon via 15 is connected to the electrode 41 on the second surface of the first substrate 11 through the metal electrode deposition layer 17, and can be connected to an external signal input processing circuit for enabling detection. Thus, through-silicon vias 15 serve as interconnect lines to achieve three-dimensional packaging of the wafer, spatially isolating the interconnect lines from the circuit region and the test region.

Wherein fig. 10 illustrates a top view of a cap layer according to an embodiment of the present disclosure. As shown in fig. 1A, 2A, 3, and 10, the cap layer may include a second substrate 31 and a bonding ring 32. The first surface of the second substrate 31 is provided with a receiving groove 312, and at least part of the sensor body is located in the receiving groove 312. The second surface of the second substrate 31 is provided with a vent hole 311 connected to the receiving groove 312 at a position corresponding to the target area. The bonding ring 32 is disposed on the first surface of the second substrate 31 and surrounds the accommodating groove 312 in a closed manner, so as to fixedly connect the base body and the cap layer together.

In this embodiment, the thickness of the cap layer may be 200 micrometers to 400 micrometers, and the first substrate and the second substrate may be silicon or other materials, so that the first substrate and the second substrate have higher compatibility with the device layer manufacturing process, and the matching of the contact strength among the first substrate, the substrate and the bonding ring is ensured. The material of the cap layer may also be glass or the like, which is not limited by the present disclosure.

In this embodiment, the cap layer and the base may be the same size, similar thickness, or the same structure. Therefore, the substrate and the cap layer can be ensured to have equivalent mechanical properties, and problems caused by mismatch of expansion coefficient, compressive strength and the like in bonding and subsequent operation can be avoided. The material of the bonding ring 32 may be a material that is easily bonded to a substrate, and for example, the material of the bonding ring 32 may be a metal such as gold (Au). In order to ensure the reliability of the fixed connection between the cap layer and the substrate, the width w3 and the thickness h of the bonding ring may be set, for example, w3 may be 100 μm to 150 μm, and h may be 150nm. As shown in fig. 10, the bonding ring 32 may surround the receiving groove 312 and be located at an edge of the first side of the second substrate.

In this embodiment, the bonding ring 32 may be secured to the base by bonding to fixedly connect the base and the cap together. The structure of the bond connection with the bond ring 32 is different due to the difference in structure between the substrate and the sensor body, and is schematically illustrated by the bonding means one, two and three.

Bonding mode one:

As shown in fig. 3, if the dielectric layer 12 covers the area of the first surface of the first substrate 11 corresponding to the accommodating groove 312 and the second insulating layer 19 also covers at most the exposed dielectric layer 12, the bonding ring 32 is fixedly connected to the first surface of the first substrate 11 by bonding, so that the base body and the cap layer are fixedly connected together, and the sensor body and the dielectric layer 12 are located in the accommodating groove 312.

Bonding mode II:

As shown in fig. 2A, if the dielectric layer 12 covers the entire area of the first surface of the first substrate 11, and the second insulating layer 19 also covers at most the exposed area of the dielectric layer 12 corresponding to the accommodating groove 312, the bonding ring 32 is fixedly connected to the dielectric layer 12 by bonding, so that the base body and the cap layer are fixedly connected together, and the sensor body is located in the accommodating groove 312.

And a bonding mode III:

As shown in fig. 1A, if the dielectric layer 12 covers the entire area of the first surface of the first substrate 11 and the second insulating layer also covers the entire area of the exposed dielectric layer 12, the bonding ring 32 is fixedly connected to the second insulating layer 19 by bonding, so that the base body and the cap layer are fixedly connected together, and at least the gas-sensitive material layer 21 of the sensor body is located in the accommodating groove 312.

In this embodiment, the accommodating groove 312 is disposed above the sensor body, and the accommodating groove 312 and the vent hole 311 are both above the gas-sensitive material layer 21, so as to ensure that gas molecules can diffuse into the gas-sensitive material layer 21 through the vent hole 311, so that the gas can fully contact with the gas-sensitive material layer 21. The position, size, and shape of the receiving groove 312 may be set according to the position, size, and shape of the sensor body such that at least the gas-sensitive material layer 21 of the sensor body is in the receiving groove 312 and in a position corresponding to the vent hole 311. The depth of the receiving groove 312 may be 100 micrometers to 300 micrometers. For example, if the sensor is configured as shown in fig. 5, and the size of the gas sensitive material layer 21 is 100 μm×100 μm to 300 μm×300 μm, the accommodating groove 312 may be a rectangular parallelepiped structure having a size of 500 μm×500 μm×100 μm (100 μm is depth).

In one possible implementation, through silicon vias 15 connecting heating electrode 18 with test electrode 20 may be symmetrically located at the four corners of receiving cavity 312 and inside receiving cavity 312. The depth of the receiving groove 312 (the distance between the top of the receiving groove 312 and the top of the sensor body) should be more than 100 μm to provide a certain stable gas layer on the surface of the sensor body so that the gas-sensitive material layer 21 can be sufficiently contacted with gas molecules.

In one possible implementation, as shown in fig. 4 and 10, the capping layer may further include: and a breathable film layer 33 located above the second surface of the second substrate 31 and covering at least the ventilation holes 311.

In this embodiment, the breathable film layer 33 may cover the entire area of the second surface of the second substrate 31 (as shown in fig. 4), or may cover only the area of the second surface of the second substrate 31 corresponding to the ventilation holes 311. The gas permeable membrane layer 33 has a selective passage that allows gas to enter the vent holes 311, blocking contaminants on the order of ten microns from entering the vent holes 311. For example, the material of the breathable film layer 33 may be a polymer. In this way, contamination and damage of the gas sensitive material layer in the sensor by contaminants can be avoided. The material and thickness of the breathable film layer can be set by those skilled in the art according to actual needs, and the present disclosure is not limited thereto.

In one possible implementation, as shown in fig. 5 and 10, the capping layer may further include: and a dust-proof mesh layer 34 disposed on the second surface of the second substrate 31 and covering at least a region of the air-permeable film layer 33 corresponding to the air holes 311, wherein a plurality of through holes 341 are provided in a portion of the dust-proof mesh layer 34 corresponding to the air holes 311.

In this embodiment, the dust-proof mesh layer 34 may cover the entire region of the air-permeable membrane layer 33 (as shown in fig. 5), or may cover only the region of the air-permeable membrane layer 33 corresponding to the ventilation holes 311. The size of the dust-proof mesh layer 34 and the ventilation film layer 33 may be the same or different, and the present disclosure is not limited thereto. The dust screen layer 34 is used for preventing large particle dirt such as dust from falling into the sensor through the vent hole 311, so that pollution and mechanical damage to the gas-sensitive material layer in the sensor caused by the large particle dirt are avoided. The material of the dust-proof mesh layer 34 may be a material such as metal that can resist corrosion by corrosive gas to improve the reliability of the sensor. For example, the material of the dust-proof mesh layer 34 may be Pt. The thickness of the dust-proof mesh layer 34 may be 100nm to 300nm. The material and thickness of the dust-proof mesh layer can be set according to actual needs by those skilled in the art, and the present disclosure is not limited thereto.

In a possible implementation manner, the capping layer may further include only a dust-proof layer (i.e. not including a breathable film layer), the dust-proof layer is located on the second surface of the second substrate 31 and covers at least a region corresponding to the ventilation hole 311, and a region of the dust-proof layer that covers at least the ventilation hole 311 is provided with a plurality of through holes 341.

In one possible implementation, the sensor may further include a processing module for controlling the energization of the heater electrode 18 and the test electrode 20 such that the heater electrode is energized to heat the layer of gas sensitive material to an operating temperature during operation of the sensor. In the working process of the sensor, the processing module monitors the current flowing through the testing electrode or controls the corresponding detecting module, and the type and/or concentration of the gas sensed by the gas-sensitive material layer are determined according to the monitoring result.

Fig. 11 shows a flowchart of a method of manufacturing a wafer level package based MEMS gas sensor according to an embodiment of the present disclosure. Fig. 12 illustrates a schematic diagram of a manufacturing process of a method of manufacturing a wafer level package based MEMS gas sensor according to an embodiment of the present disclosure. Fig. 13 is a schematic view illustrating a process of fabricating a cap layer in a method of fabricating a wafer level package-based MEMS gas sensor according to an embodiment of the present disclosure. The method provided by the disclosure can save the cost for manufacturing the sensor, so that the efficiency and the speed for manufacturing the sensor are obviously improved.

As shown in fig. 11 to 13, the method includes: a base body manufacturing step, a sensor body manufacturing step, a cap layer manufacturing step, a fixed connection step, and an electrode manufacturing step. Wherein the substrate manufacturing step includes steps S501 to S503. The sensor body manufacturing steps include steps S504 to S508. The cap layer manufacturing step includes steps S509 to S513. The fixed connection step includes step S514. The electrode manufacturing step includes step S515. In fig. 12 and 13, the sensor shown in fig. 5 is schematically manufactured, and a flow of the manufacturing method is shown. It is understood that the substrate fabrication steps may be performed before, after, or simultaneously with the cap layer fabrication steps. The sensor body manufacturing step is performed after the base manufacturing step, the fixing connecting step is performed after the base manufacturing step, the sensor body manufacturing step, and the cap layer manufacturing step are performed, and the electrode manufacturing step is performed after the fixing connecting step.

And (3) a substrate manufacturing step: including steps S501 to S503.

In step S501, a dielectric layer 12 is prepared on the first surface of the first substrate 11, where the dielectric layer 12 may be a silicon oxide layer 121, a silicon nitride layer 122, and a silicon oxide layer 123. The dielectric layer 12 may be prepared using a PECVD process.

In step S502, the first substrate 11 and the dielectric layer 12 are etched, and the first substrate 11 is thinned to form a plurality of through silicon vias 15.

As shown in fig. 12, step S502 may include:

Etching the first substrate 11 and the dielectric layer 12 to form a plurality of blind holes 13 required for preparing the sensor; preparing a silicon oxide insulating layer (the insulating layer can be prevented from being damaged by subsequent high temperature) on the surface of the blind hole 13 through thermal oxidation, and then sequentially preparing a TiN barrier layer and a Cu seed layer on the surface of the insulating layer by adopting an atomic layer deposition (Atomic layer deposition, ALD) process or a physical vapor deposition (Physical Vapor Deposition, PVD) process; the blind via 13 may be filled with metal using an electroplating process to form a metal structure 14 as shown in fig. 12, which may then be annealed to partially relieve the stress from the filled metal; because the metal structure 14 is also electroplated on the dielectric layer 12, the metal structure 14 on the dielectric layer 12 can be polished by adopting the processes such as chemical mechanical Polishing (CHEMICAL MECHANICAL Polishing); the second side of the first substrate 11 is thinned after polishing until the blind holes 13 are exposed, resulting in through silicon vias 15. Wherein the insulating layer, tiN barrier layer and Cu seed layer in the through silicon via are not shown in fig. 12 for simplicity. The insulating layer is used to electrically insulate the metal pillars in the through-silicon via 15 from the first substrate 11. The barrier layer is used to prevent electrode metal in the metal pillars in the through-silicon via 15 from diffusing into the insulating layer and the first substrate 11.

The dielectric layer 12 may be etched by using an inductively coupled plasma (Inductively Coupled Plasma, ICP) dry etching process, and the first substrate 11 may be etched by using a Bosch process, so as to finally form a plurality of blind holes 13.

In step S503, a first insulating layer 16 is prepared on the second surface of the first substrate 11, and the first insulating layer 16 is etched to expose at least the via areas corresponding to the through-silicon vias 15, thereby completing the manufacture of the substrate.

Wherein the first insulating layer 16 can be prepared by PECVD, metal diffusion in the through silicon via at high temperature can be avoided. The via areas may then be patterned using a photolithographic process, and the first insulating layer 16 may then be etched using an ICP process until the via areas are exposed. Then, a metal electrode deposition layer 17 can be deposited in the through hole area by a metal deposition mode such as magnetron sputtering or evaporation coating, and the metal electrode deposition layer is used as a contact area for subsequent ball implantation (the manufacturing step of the contact area is an optional step). Through polishing in the process of preparing the through silicon vias and thinning in the step S503, wafer warpage caused by film stress can be eliminated, and smooth implementation of subsequent processes is ensured.

The manufacturing steps of the sensor main body are as follows: including steps S504 to S508.

In step S504, the heating electrode 18 is prepared on the surface of the dielectric layer 12.

The surface of the dielectric layer 12 may be coated with photoresist, after patterning the photoresist based on the structure and the size of the heating electrode 18, the area of the surface of the dielectric layer 12 where the heating electrode 18 needs to be manufactured is exposed, and then the heating electrode is formed by performing metal deposition in a metal deposition manner such as magnetron sputtering or evaporation coating, and then the redundant photoresist on the surface of the dielectric layer 12 is removed.

In step S505, a second insulating layer 19 is formed on the heater electrode 18 and the exposed dielectric layer 12. The second insulating layer may be deposited using a PECVD process.

In step S506, the second insulating layer 19 is etched to form a via 191, so that a through-silicon via of the plurality of through-silicon vias 15 for connection with the test electrode 20 is exposed through the via 191.

The surface of the second insulating layer 19 may be coated with photoresist, after patterning the photoresist based on the position and the size of the through silicon vias 15 connected to the test electrode 20, the second insulating layer 19 is etched by ICP process, exposing the through silicon vias 15 used for connecting to the test electrode 20, and then removing the excess photoresist on the surface of the second insulating layer 19.

In step S507, a test electrode 20 having a target region overlapping the heating electrode 18 is fabricated on the second insulating layer 19, and the test electrode 20 is connected to the through-silicon via 15 exposed by the second insulating layer 19.

The surface of the second insulating layer 19 may be coated with a photoresist, after patterning the photoresist based on the structure and the size of the test electrode 20, the area of the surface of the second insulating layer 19 where the test electrode 20 needs to be prepared is exposed, and then the test electrode 20 is formed by performing metal deposition in a metal deposition manner such as magnetron sputtering or evaporation coating, and then removing the redundant photoresist on the surface of the second insulating layer 19.

In step S508, the gas-sensitive material layer 21 is manufactured over the target area, completing the manufacture of the sensor body.

The patterning is performed above the target area of the test electrode 20 by adopting a photolithography mode, the second insulating layer 19 and the area, where the gas sensitive material layer 21 needs to be prepared, of the surface of the test electrode 20 are exposed, then the gas sensitive material is coated by adopting a coating mode, and the gas sensitive material layer 21 is obtained after photoresist is stripped, so that the sensor main body is obtained.

And (3) a cap layer manufacturing step: including steps S509 to S513.

In step S509, a bonding ring 32 is prepared on the first side of the second substrate 31.

The bonding ring region may be patterned by photolithography, then deposited by metal deposition such as magnetron sputtering or evaporation plating, and then stripped of the excess glue layer to obtain the bonding ring 32.

In step S510, the second substrate 31 is etched to form a vent hole 311 penetrating the second substrate 31 and corresponding to the target region. Wherein the second substrate 31 may be etched using a BOSCH process to form the vent holes 311.

In step S511, the first surface of the second substrate 31 is etched to form a receiving groove 312 connected to the vent hole 311.

The first surface of the second substrate 31 may be patterned by photolithography in a region corresponding to the receiving groove, and the second substrate 31 in the patterned region is etched by a BOSCH process to form the receiving groove 312.

In step S512, a pre-prepared breathable film is attached to the second surface of the second substrate 31 and covers at least the vent holes 311, thereby forming a breathable film layer 33. Wherein, step S512 may be omitted, i.e., in the case where the capping layer does not include a breathable film layer, step S512 may be omitted.

In step S513, a dust-proof layer is prepared over the air-permeable film layer 33, and a dust-proof layer 34 having a plurality of through holes 341 is formed to cover at least a portion of the air-permeable film layer 33. Wherein step S513 may be omitted, i.e., in the case where the capping layer does not include the dust-proof layer 34, step S513 may be omitted.

The dust-proof layer may be patterned by photolithography, exposing the area above the air-permeable film layer 33 and the area above the second surface of the second substrate where the dust-proof layer needs to be prepared, forming the dust-proof layer by metal deposition by magnetron sputtering or evaporation plating, and removing the excessive photoresist, thereby completing the preparation of the dust-proof layer 34.

In one possible implementation, if the capping layer includes a dust-proof mesh layer but does not include a gas-permeable film layer, the following operations may be directly performed after step S511: the dust-proof layer can be patterned in a photoetching mode, a region, above the second surface of the second substrate, of which the dust-proof layer needs to be prepared is exposed, the dust-proof layer is formed by metal deposition in a metal deposition mode such as magnetron sputtering or evaporation coating, and then redundant photoresist is removed, so that the dust-proof layer is prepared, and the dust-proof layer with a plurality of through holes at least covering the part of the vent holes is obtained.

And (3) fixedly connecting: including step S514.

In step S514, the bonding ring 32 and the base are fixedly connected together by bonding, so that at least part of the sensor body is located in the receiving groove 312.

Wherein, reverse compressive stress can be applied to the substrate during bonding to further alleviate warpage.

According to the difference between the substrate and the sensor main body structure, step S514 includes any one of the following implementation manners:

If the dielectric layer 12 covers the area of the first surface of the first substrate 11 corresponding to the accommodating groove 312 and the second insulating layer 19 also covers at most the exposed dielectric layer 12, the bonding ring 32 is fixedly connected to the first surface of the first substrate 11 by bonding, so that the base body and the cap layer are fixedly connected together, and the sensor body and the dielectric layer 12 are located in the accommodating groove 312. That is, a sensor in which the base and the cap layer are connected as shown in fig. 3 is finally obtained. Or alternatively

If the dielectric layer 12 covers the entire area of the first surface of the first substrate 11, and the second insulating layer 19 also covers at most the exposed area of the dielectric layer 12 corresponding to the accommodating groove 312, the bonding ring 32 is fixedly connected to the dielectric layer 12 by bonding, so that the base body and the cap layer are fixedly connected together, and the sensor body is located in the accommodating groove 312. That is, a sensor in which the base and the cap layer are connected as shown in fig. 2A is finally obtained. Or alternatively

If the dielectric layer 12 covers the whole area of the first surface of the first substrate 11 and the second insulating layer 19 also covers the whole area of the exposed dielectric layer 12, the bonding ring 32 is fixedly connected to the second insulating layer 19 by bonding, so that the base body and the cap layer are fixedly connected together, and at least the gas-sensitive material layer 21 is located in the accommodating groove 312. That is, a sensor in which the base and the cap layer are connected as shown in fig. 1A is finally obtained.

Or alternatively

Electrode manufacturing steps: including step S515.

In step S515, balls are implanted in the through hole areas to form the electrodes 41 of the sensor, thereby completing the preparation of the sensor. Wherein, the ball can be planted by adopting a laser ball planting mode.

It should be noted that, although the MEMS gas sensor based on the wafer level package and the manufacturing method thereof are described above by way of example in the above embodiments, those skilled in the art will understand that the present disclosure should not be limited thereto. In fact, the user can flexibly set each structure and each step of the method of the sensor according to personal preference and/or actual application scene, so long as the technical scheme of the disclosure is met.

The foregoing description of the embodiments of the present disclosure has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the various embodiments described. The terminology used herein was chosen in order to best explain the principles of the embodiments, the practical application, or the technical improvements in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A wafer level package based MEMS gas sensor, the sensor comprising: the sensor comprises a substrate, a sensor main body for detecting external gas, a cap layer and a plurality of electrodes;

The cap layer comprises a second substrate and a bonding ring, wherein a first surface of the second substrate is provided with a containing groove, and at least part of the sensor main body is positioned in the containing groove; the second surface of the second substrate is provided with a vent hole which is connected with the accommodating groove and the position of which corresponds to the target area; the bonding ring is arranged on the first surface of the second substrate and is closed to encircle the accommodating groove and is used for fixedly connecting the base body and the cap layer together;

the dielectric layer covers the area of the first surface of the first substrate corresponding to the accommodating groove, the second insulating layer also covers at most the exposed dielectric layer, and the bonding ring is fixedly connected with the first surface of the first substrate, so that the base body and the cap layer are fixedly connected together, and the sensor main body and the dielectric layer are positioned in the accommodating groove; or alternatively

2. The sensor of claim 1, wherein the cap layer further comprises:

3. The sensor of claim 2, wherein the cap layer further comprises:

4. A sensor according to claim 1, wherein,

The shape of the heating electrode comprises a malleable shape, and the malleable shape comprises any one of a snake shape and an S shape; and/or

5. A method of manufacturing a MEMS gas sensor based on wafer level packaging, for manufacturing the sensor of any of claims 1-4, the method comprising: a base body manufacturing step, a sensor body manufacturing step, a cap layer manufacturing step, a fixed connection step, and an electrode manufacturing step,

Electrode manufacturing steps: ball implantation is carried out in each through hole area, electrodes of the sensor are formed, and the preparation of the sensor is completed;

wherein, the bonding ring and the basal body are fixedly connected together in a bonding way, and the method comprises any one of the following steps:

6. The method of claim 5, wherein the cap layer manufacturing step further comprises:

7. The method of claim 6, wherein the cap layer manufacturing step further comprises:

8. The method of claim 6, wherein the step of providing the first layer comprises,