CN116008228A

CN116008228A - Chip integrated type NDIR gas sensor and preparation method thereof

Info

Publication number: CN116008228A
Application number: CN202310142649.6A
Authority: CN
Inventors: 宏宇; 武斌
Original assignee: Shenzhen Meisi Xianrui Electronic Co ltd
Current assignee: Shenzhen Meisi Xianrui Electronic Co ltd
Priority date: 2023-02-21
Filing date: 2023-02-21
Publication date: 2023-04-25

Abstract

The invention discloses a chip integrated NDIR gas sensor, which comprises a top cover assembly, a first wafer and a second wafer which are sequentially connected in a bonding way; an air chamber is formed between the top cover assembly and the first wafer, an air vent is arranged on the top cover assembly, an MEMS infrared light source and a thermopile assembly are arranged on the first wafer, and an optical filter is arranged on the upper cover of the thermopile assembly; and one side of the second wafer, which is bonded with the first wafer, is provided with an ASIC circuit for controlling the MEMS infrared light source and processing the electric signal generated by the thermopile assembly, and a pin for exchanging signals with the outside. According to the invention, the MEMS infrared light source and the thermopile component for sensing infrared signals are integrated on the first wafer, so that the volume of the sensor is reduced, and the ASIC circuit for processing signals generated by the thermopile component is integrated inside the sensor, so that the transmission noise is effectively reduced, and the detection precision is improved.

Description

Chip integrated type NDIR gas sensor and preparation method thereof

Technical Field

The invention belongs to the technical field of NDIR gas sensors, and particularly relates to a chip integrated type NDIR gas sensor and a preparation method thereof.

Background

A non-dispersive infrared (NDIR) gas sensor is a sensing device that selects absorption characteristics based on near infrared spectra of different gas molecules, determines a gas composition according to lambert-beer's law using a relationship of gas concentration to absorption intensity, and determines its concentration. The NDIR gas sensor is generally mainly composed of an infrared light source, a gas chamber, an optical filter and an infrared detector. The gas molecules in the gas cell cause absorption at specific wavelengths, the filter filters out light at other wavelengths, and the gas species and concentration are determined by detecting the attenuation of these wavelengths.

However, most NDIR gas sensors are currently formed by combining discrete devices, which results in low integration and large size of the sensor, and when detecting multiple gases, more detectors are required to be added, so that the volume of the NDIR gas sensor is further increased.

Disclosure of Invention

The invention mainly aims to provide a chip integrated type NDIR gas sensor so as to solve the problems of low integration degree and large size of the traditional NDIR gas sensor.

In order to solve the technical problems, the invention adopts the following technical scheme:

a chip integrated NDIR gas sensor comprises a top cover component, a first wafer and a second wafer which are sequentially connected in a bonding way;

an air chamber is formed between the top cover assembly and the first wafer, an air vent is arranged on the top cover assembly, an MEMS infrared light source and a thermopile assembly are arranged on the first wafer, and an optical filter is arranged on the upper cover of the thermopile assembly;

and one side of the second wafer, which is bonded with the first wafer, is provided with an ASIC circuit for controlling the MEMS infrared light source and processing the electric signal generated by the thermopile assembly, and a pin for exchanging signals with the outside.

In a possible embodiment, the thermopile assembly comprises a plurality of thermopile units arranged in a linear array, and the MEMS infrared light source is arranged perpendicular to the thermopile array.

In a possible implementation manner, the thermopile assembly comprises a plurality of thermopile units arranged in a circumferential array, and the MEMS infrared light source is arranged in the center of the thermopile array.

In a possible implementation manner, the optical filter is a linear gradient optical filter, and areas of different wave bands on the linear gradient optical filter respectively correspond to the thermopile units.

In a possible implementation manner, the optical filters are independent narrowband optical filters, and a plurality of narrowband optical filters with different wave bands respectively correspond to a plurality of thermopile units.

In one possible implementation mode, the top cover assembly comprises a frame and a cover plate arranged on the frame, the frame is connected with the first wafer in a bonding mode, the vent hole is formed in the cover plate, and a reflection inclined plane is arranged on the inner side of the cover plate, so that infrared light emitted by the MEMS infrared light source can be reflected to the optical filter to the greatest extent.

In a possible implementation manner, the inner surface of the cover plate and the surface of one side of the first wafer, on which the thermopile assembly is arranged, are respectively provided with a high-reflectivity film layer for improving the reflectivity of infrared rays.

In one possible embodiment, the vent hole is provided with a waterproof and breathable film.

Based on the same inventive concept, the invention also provides a preparation method of the chip integrated NDIR gas sensor, which comprises the following steps:

preparing an ASIC circuit on a wafer through a CMOS process, and then cutting to obtain a second wafer;

preparing a thermopile assembly and an MEMS infrared light source on a wafer by utilizing a semiconductor technology, and then cutting to obtain a first wafer;

evaporating a filter layer on a wafer by using a film evaporation technology, and cutting to obtain a filter;

preparing a cavity on the wafer by using an anisotropic wet etching process, etching a vent hole at the bottom of the cavity, and then cutting to obtain a top cover assembly;

the second wafer, the first wafer, the filter and the cover plate assembly are assembled using TSV technology, a multi-wafer bonding technology.

In a possible embodiment, the method further includes: and evaporating a high-reflectivity film layer on the inner surface of the top cover assembly by using a vacuum evaporation process.

The beneficial effects of adopting above-mentioned technical scheme to produce lie in: according to the invention, the MEMS infrared light source and the thermopile component for sensing infrared signals are integrated on the first wafer, so that the volume of the sensor is reduced, and the ASIC circuit for processing signals generated by the thermopile component is integrated inside the sensor, so that the transmission noise is effectively reduced, and the detection precision is improved.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention, illustrate and explain the invention and are not to be construed as limiting the invention.

FIG. 1 is a schematic diagram of the overall structure of a chip-integrated NDIR gas sensor according to embodiment 1 of the present invention;

FIG. 2 is an exploded view of the chip-integrated NDIR gas sensor according to embodiment 1 of the present invention;

FIG. 3 is a schematic diagram of a first wafer in a chip-integrated NDIR gas sensor according to embodiment 1 of the present invention;

FIG. 4 is a schematic diagram of a second wafer in the chip-integrated NDIR gas sensor according to embodiment 1 of the present invention;

FIG. 5 is a cross-sectional view of a chip-integrated NDIR gas sensor provided in embodiment 1 of the invention;

FIG. 6 is a schematic diagram of the structure of the chip-integrated NDIR gas sensor according to embodiment 1 of the present invention when a narrow band filter is used;

fig. 7 is a flowchart of a method for manufacturing a chip-integrated NDIR gas sensor according to embodiment 2 of the present invention.

Wherein:

1. a first wafer; 11. a TSV structure; 10. a gas chamber; 2. a second wafer; 21. an ASIC circuit; 22. pins; 23. welding spots; 3. a top cover assembly; 31. a cover plate; 311. a vent hole; 312. a reflective bevel; 32. a frame; 4. a MEMS infrared light source; 5. a thermopile assembly; 6. a light filter; 7. waterproof breathable films.

Detailed Description

The present invention will be described in further detail with reference to the following examples in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

In the description of the present invention, it should be clearly understood that terms such as "vertical", "horizontal", "longitudinal", "front", "rear", "left", "right", "upper", "lower", "horizontal", and the like indicate an orientation or a positional relationship based on that shown in the drawings, and are merely for convenience of describing the present invention, and do not mean that the apparatus or element referred to must have a specific orientation or position, and thus should not be construed as limiting the present invention. The "number" is not to be construed as limiting the invention.

In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

It is understood that each element of the apparatus or each step of the method may be described by an apparatus term or a method term. Such terms may be substituted as needed so that the underlying broad scope of the invention authority is clear. As just one example, it is to be understood that all steps of a method may be disclosed as an action, a means for taking the action, or an element that causes the action. Similarly, each element of a device may be disclosed as a physical element or an action facilitated by the physical element. As just one example, the disclosure of "connector" should be understood to cover the disclosure of "connect" action, whether or not explicitly discussed-and conversely, if a "connect" action is disclosed, this disclosure should be understood to cover the disclosure of "connector" and even "means for connecting. These alternative terms for each element or step should be understood to be expressly included in the description.

Example 1

The embodiment 1 of the invention provides a chip integrated NDIR gas sensor, as shown in fig. 1 to 5, comprising a top cover assembly 3, a first wafer 1 and a second wafer 2 which are sequentially bonded and connected;

an air chamber 10 is formed between the top cover assembly 3 and the first wafer 1, an air vent 311 is arranged on the top cover assembly 3, an MEMS infrared light source 4 and a thermopile assembly 5 which are positioned in the air chamber 10 are arranged on the first wafer 1, and an optical filter 6 is arranged on the upper cover of the thermopile assembly 5;

the second wafer 2 is provided with an ASIC circuit 21 on the side bonded to the first wafer 1 for controlling the MEMS infrared light source 4 and processing the electrical signal generated by the thermopile assembly 5, and a pin 22 for exchanging signals with the outside.

After the technical scheme is adopted, the MEMS infrared light source 4 and the thermopile assembly 5 for sensing infrared signals are integrated on the first wafer 1, so that the size of the sensor is reduced, and the ASIC circuit 21 for processing signals generated by the thermopile assembly 5 is integrated inside the sensor, so that transmission noise is effectively reduced, and detection precision is improved.

Specifically, as shown in fig. 4, the second wafer 2 is provided with a solder joint 23 for connecting the ASIC circuit 21 and the first wafer 1, and correspondingly, as shown in fig. 3, a TSV structure 11 is provided on the first wafer 1 corresponding to the solder joint 23 of the second wafer 2 (the TSV structure 11 includes an electroplated copper pillar, an insulating layer and a barrier layer in sequence from inside to outside in a through hole on the first wafer 1, and the insulating layer is used for isolating and insulating the first wafer 1 from the filled conductive material, and the material is usually silicon dioxide), and the TSV structure 11 is electrically connected with the thermopile assembly 5 and the MEMS infrared light source 4.

Specifically, as shown in fig. 2, the top cover assembly 3 includes a frame 32 and a cover plate 31, the cover plate 31 is disposed on the frame 32, the frame 32 is of a hollow frame structure, and the frame 32 is bonded to the first wafer 1, so that a cavity is defined among the cover plate 31, the frame 32 and the first wafer 1, and is used as the air chamber 10.

The vent hole 311 is provided on the cover plate 31, and a reflection inclined plane 312 is provided on the inner side of the cover plate 31, so that the infrared light emitted by the MEMS infrared light source 4 passes through the gas to be measured, and then can be reflected to the optical filter 6 to the greatest extent, and enters the thermopile assembly 5.

Further, the inner surface of the cover plate 31 and the surface of the side of the first wafer 1 on which the thermopile assembly 5 is disposed are respectively provided with a high reflectivity film layer, so as to improve the reflection efficiency of infrared rays and reduce reflection attenuation.

Further, in order to prevent the influence of components other than gas (particularly, water vapor) on the sensor, the accuracy of the detection result and the service life are improved, and therefore, the waterproof and breathable film 7 is provided on the vent hole 311.

In one possible embodiment, as shown in fig. 3, the thermopile assembly 5 includes a plurality of thermopile units arranged in a linear array, and the MEMS infrared light source 4 is disposed perpendicular to the thermopile array, that is, a line connecting the MEMS infrared light source 4 and the thermopile assembly 5 is perpendicular to the linear array formed by the plurality of thermopile units.

In one possible embodiment, the thermopile assembly 5 comprises a plurality of thermopile units arranged in a circumferential array, and the MEMS infrared light source 4 is disposed in the center of the thermopile array.

In one possible embodiment, as shown in fig. 2, the optical filter 6 is a linear graded optical filter 6, and areas of different wavebands on the linear graded optical filter 6 respectively correspond to a plurality of thermopile units, and the linear graded optical filter 6 linearly filters the infrared radiation so that the infrared radiation with different wavelengths irradiates different thermopile units of the thermopile array. For different thermopile units, infrared rays with different wave bands can be received through the linear filter 6, and the linear gradient filter 6 is adjusted, so that the thermopile units can receive the required infrared rays.

In one possible embodiment, as shown in fig. 6, the filter 6 is an independent narrowband filter 6, and a plurality of narrowband filters 6 with different wavebands respectively correspond to a plurality of thermopile units.

The working process of the chip integrated NDIR gas sensor provided by the invention is as follows:

the gas to be measured enters the gas chamber 10 through the vent holes 311;

the pin 22 receives an external signal, and controls the MEMS infrared light source 4 through the ASIC circuit 21 to emit the broad spectrum infrared radiation with fixed frequency to irradiate the gas to be detected in the gas chamber 10;

after the infrared radiation is absorbed by the gas to be detected in the gas chamber 10, the infrared radiation is reflected to the optical filter 6 for multiple times, the optical filter 6 filters the infrared radiation, so that the infrared radiation with different wavelengths irradiates different thermopile units in the thermopile assembly 5;

the thermopile unit generates an electric signal and transmits the electric signal to the ASIC circuit 21, and the ASIC circuit 21 processes the received thermopile unit signal based on the lambert law to calculate the gas component and concentration of the gas to be detected; the calculated gas composition and concentration are transmitted to an external circuit through the pin 22.

Example 2

Embodiment 2 of the present invention provides a method for preparing a chip-integrated NDIR gas sensor in embodiment 1, as shown in fig. 7, comprising the following steps:

s1, preparing an ASIC (application specific integrated circuit) circuit 21 on a wafer through a CMOS (complementary metal oxide semiconductor) process, and then cutting to obtain a second wafer 2;

s2, preparing a thermopile assembly 5 and an MEMS infrared light source 4 on a wafer by utilizing a semiconductor technology, and then cutting to obtain a first chip 1;

the semiconductor technology used in this embodiment is a well-established process.

For example, the MEMS infrared light source 4 is composed of a substrate, a support film, a heating layer, and a radiation layer. The substrate is used for supporting the whole supporting film, the heating layer and the radiation layer. The support film is a support structure for the heating layer and the radiation layer. The heating layer is made of conductive metal, and electricity is converted into heat energy by applying a certain voltage. Since the infrared spectrum produced by blackbody radiation depends on the radiation temperature, the light source heats up to several hundred degrees celsius in the thin film region during normal operation. And then the broad-spectrum infrared light is radiated outwards by the principle of heat radiation. In the preparation of the MEMS infrared light source 4, a supporting thin film structure is deposited on a wafer (substrate) and then a heating layer and a radiation layer are formed on the thin film.

For example, in preparing a thermopile unit in the thermopile assembly 5, first, a first heat conduction layer is formed on a wafer; then, depositing and patterning a first thermocouple material on the first heat conducting layer to form a first thermocouple layer; forming a second heat conduction layer and a thermocouple vertical part on the first thermocouple layer; next, forming a second thermal couple layer on the thermal couple vertical part, wherein the connection part of the second thermal couple layer and the first vertical part is a hot end of the thermocouple, and the connection part of the second vertical part and the first thermal couple layer is a cold end of the thermocouple; thirdly, forming a heat absorption layer on the hot end; and finally, performing a release process to remove the second heat conduction layer around the first vertical part and the first heat conduction layer below the first vertical part to form the MEMS thermopile unit.

S3, evaporating a filter layer on the wafer by using a film evaporation technology, and cutting to obtain a filter 6;

s4, preparing a cavity on the wafer by using an anisotropic wet etching process, etching a vent hole 311 at the bottom of the cavity, and then cutting to obtain a top cover assembly 3;

s5, assembling the second wafer 2, the first wafer 1, the optical filter 6 and the top cover assembly 3 by using TSV technology and multi-wafer bonding technology.

Further, the manufacturing method further comprises the following steps: before step S5, a high-reflectivity film layer is evaporated on the inner surface of the top cap assembly 3 using a vacuum evaporation process.

The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the 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. The chip integrated NDIR gas sensor is characterized by comprising a top cover assembly, a first wafer and a second wafer which are sequentially connected in a bonding mode;

2. The chip-integrated NDIR gas sensor according to claim 1, wherein said thermopile assembly comprises a plurality of thermopile units arranged in a linear array, said MEMS infrared light source being disposed perpendicular to the thermopile array.

3. The chip-integrated NDIR gas sensor according to claim 1, wherein the thermopile assembly comprises a plurality of thermopile units arranged in a circumferential array, and the MEMS infrared light source is disposed at the center of the thermopile array.

4. The chip-integrated NDIR gas sensor according to claim 2, wherein said filter is a linear graded filter, and regions of different wavelength bands on said linear graded filter correspond to a plurality of said thermopile units, respectively.

5. The chip-integrated NDIR gas sensor according to claim 2 or 3, wherein said filter is an independent narrowband filter, and a plurality of narrowband filters of different wavelength bands respectively correspond to a plurality of said thermopile units.

6. The integrated chip NDIR gas sensor according to claim 1, wherein the top cover assembly comprises a frame and a cover plate disposed on the frame, the frame is connected with the first wafer in a bonding manner, the vent hole is disposed on the cover plate, and a reflection inclined plane is disposed on the inner side of the cover plate, so that infrared light emitted by the MEMS infrared light source can be reflected to the optical filter to the greatest extent.

7. The chip integrated NDIR gas sensor according to claim 6, wherein the inner surface of the cover plate and the surface of the side of the first wafer where the thermopile assembly is disposed are respectively provided with a high reflectivity film layer.

8. The chip-integrated NDIR gas sensor according to claim 1, wherein a waterproof and breathable film is disposed on the vent hole.

9. A method of manufacturing a chip-integrated NDIR gas sensor according to any of claims 1-8, comprising the steps of:

10. The method of manufacturing according to claim 9, further comprising: and evaporating a high-reflectivity film layer on the inner surface of the top cover assembly by using a vacuum evaporation process.