1. A MEMS gas sensor, comprising:

a substrate, a first electrode and a second electrode,

a dielectric layer formed on the substrate;

the insulating layer is formed on the dielectric layer;

and the gas-sensitive electrode is embedded into the insulating layer, and the upper surface of the gas-sensitive electrode and the upper surface of the insulating layer are positioned on the same horizontal plane.

2. The method of claim 1, wherein the gas-sensitive electrodes comprise gas-sensitive interdigitated electrodes;

the sensor further comprises:

and the gas-sensitive film is formed on the gas-sensitive interdigital electrode.

3. The method according to claim 2, wherein a cavity is provided in the substrate, said cavity being provided in a corresponding region of the gas-sensitive interdigitated electrodes.

4. The method of claim 3, wherein the sensor further comprises:

and the release through hole is formed outside the gas-sensitive interdigital electrode, penetrates through the dielectric layer and the insulating layer and is communicated with the cavity.

5. The method of claim 1, wherein the sensor further comprises:

a heating electrode disposed in the insulating layer.

6. A method of making a MEMS gas sensor, comprising:

forming a dielectric layer on a substrate;

forming an insulating layer on the dielectric layer;

forming a gas-sensitive electrode groove in the insulating layer;

and forming a gas-sensitive electrode embedded in the insulating layer in the gas-sensitive electrode groove, wherein the upper surface of the gas-sensitive electrode and the upper surface of the insulating layer are in the same horizontal plane.

7. The method of claim 6, wherein the gas-sensitive electrodes comprise gas-sensitive interdigitated electrodes;

after the forming the gas sensing electrode embedded in the insulating layer, further comprising:

and forming a gas-sensitive film on the gas-sensitive interdigital electrode through a gas-sensitive electrode hard mask.

8. The method of claim 7, further comprising, after the forming the gas sensing electrode embedded in the insulating layer:

forming a release through hole outside the gas-sensitive interdigital electrode by using a thick photoresist as a mask and a dry etching process;

enabling corrosive liquid to flow into the substrate through the release through hole to form a cavity;

the release through hole penetrates through the dielectric layer and the insulating layer and is communicated with the cavity.

9. The method of claim 1, further comprising, after forming a dielectric layer on the substrate:

and forming a heating electrode above the dielectric layer by using the thick photoresist as a mask and a dry etching process.

10. The method of claim 9, wherein forming an insulating layer on the dielectric layer comprises:

forming the insulating layer on the heating electrode, wherein the heating electrode is disposed in the insulating layer.

Background

Evaporation (Evaporation) combined with lift-off process (lift-off) is a common method for making gas-sensitive interdigital electrodes. The method can form a platinum interdigital electrode or a gas-sensitive interdigital electrode which is also called a convex interdigital electrode and protrudes out of the insulating layer. And depositing a three-dimensional columnar gas-sensitive film layer on the convex interdigital electrode by adopting a Glancing Angle Deposition (GLAD for short), wherein the gas-sensitive layer can fluctuate along with fluctuation of the convex interdigital electrode, so that the gas-sensitive film layer is uneven, namely the thickness and the density of the gas-sensitive film layer cannot be uniformly distributed. Meanwhile, the glancing angle deposition mode can cause the gas-sensitive material to form a strong edge growth effect at the periphery of the interdigital strip, so that the porosity of the gas-sensitive film is uneven, and the specific surface area of the gas-sensitive film is reduced.

Disclosure of Invention

The embodiment of the application provides an MEMS gas sensor and a manufacturing method, solves the technical problems that in the prior art, the thickness and density distribution of a gas-sensitive film layer formed on a gas-sensitive interdigital electrode are uneven, and the specific surface area of the gas-sensitive film is low, realizes that the gas-sensitive film deposited on the gas-sensitive interdigital electrode has a good forward growth effect, obviously improves the thickness uniformity and density uniformity of the gas-sensitive film layer, and increases the technical effect of the surface area of the gas-sensitive film.

In a first aspect, an embodiment of the present invention provides a MEMS gas sensor, including:

a substrate, a first electrode and a second electrode,

a dielectric layer formed on the substrate;

the insulating layer is formed on the dielectric layer;

and the gas-sensitive electrode is embedded into the insulating layer, and the upper surface of the gas-sensitive electrode and the upper surface of the insulating layer are positioned on the same horizontal plane.

Preferably, the gas-sensitive electrode comprises a gas-sensitive interdigital electrode;

the sensor further comprises:

and the gas-sensitive film is formed on the gas-sensitive interdigital electrode.

Preferably, a cavity is arranged in the substrate, and the cavity is arranged in a region corresponding to the gas-sensitive interdigital electrode.

Preferably, the sensor further comprises:

and the release through hole is formed outside the gas-sensitive interdigital electrode, penetrates through the dielectric layer and the insulating layer and is communicated with the cavity.

Preferably, the sensor further comprises:

a heating electrode disposed in the insulating layer.

Based on the same inventive concept, in a second aspect, the present invention further provides a method for manufacturing a MEMS gas sensor, including:

forming a dielectric layer on a substrate;

forming an insulating layer on the dielectric layer;

forming a gas-sensitive electrode groove in the insulating layer;

and forming a gas-sensitive electrode embedded in the insulating layer in the gas-sensitive electrode groove, wherein the upper surface of the gas-sensitive electrode and the upper surface of the insulating layer are in the same horizontal plane.

Preferably, the gas-sensitive electrode comprises a gas-sensitive interdigital electrode;

after the forming the gas sensing electrode embedded in the insulating layer, further comprising:

and forming a gas-sensitive film on the gas-sensitive interdigital electrode through a gas-sensitive electrode hard mask.

Preferably, after the forming of the gas sensing electrode embedded in the insulating layer, the method further includes:

forming a release through hole outside the gas-sensitive interdigital electrode by using a thick photoresist as a mask and a dry etching process;

enabling corrosive liquid to flow into the substrate through the release through hole to form a cavity;

the release through hole penetrates through the dielectric layer and the insulating layer and is communicated with the cavity.

Preferably, after forming the dielectric layer on the substrate, the method further includes:

and forming a heating electrode above the dielectric layer by using the thick photoresist as a mask and a dry etching process.

Preferably, the forming an insulating layer on the dielectric layer includes:

forming the insulating layer on the heating electrode, wherein the heating electrode is disposed in the insulating layer.

One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

the invention provides an MEMS gas sensor and a manufacturing method thereof. Therefore, when the gas-sensitive film is deposited subsequently, the thickness and the density of the gas-sensitive film can be uniformly distributed, the surface area of the formed gas-sensitive film is increased, and the sensitivity of the gas sensor is improved.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:

FIG. 1 shows a schematic structural diagram of a MEMS gas sensor in an embodiment of the invention;

fig. 2 shows a schematic structural diagram of a gas-sensitive interdigital electrode in an embodiment of the present invention;

FIG. 3 is a flow chart illustrating steps of a method of fabricating a MEMS gas sensor in an embodiment of the invention.

Detailed Description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

Example one

A first embodiment of the present invention provides a MEMS gas sensor, as shown in fig. 1, including: a substrate 101 having a cavity 107, a dielectric layer 102, an insulating layer 103, a heater electrode 104, a gas sensing electrode 105, a gas sensing film 108, and a release via 106.

The substrate 101 is a silicon semiconductor material.

A dielectric layer 102 formed on the substrate 101 and mainly composed of silicon dioxide SiO₂。

An insulating layer 103 is formed on the dielectric layer 102, and the main element thereof is silicon nitride SiN.

After the dielectric layer 102 is formed, a heating electrode 104 is formed over the dielectric layer 102 by using a thick photoresist as a mask and a dry etching process. Specifically, a layer of photoresist is spin-coated on the upper surface of the dielectric layer 102, and light is passed through a mask to expose the photoresist and develop to expose the micro-heater pocket. A layer of metal is then deposited on the photoresist by an evaporation technique, wherein the metal also needs to be deposited in the micro-heater pocket. Then, a heating electrode 104 is formed over the dielectric layer 102 by a stripping and stripping process.

After the heating electrode 104 is formed, the insulating layer 103 is formed on the heating electrode 104. Thus, the heating electrode 104 is provided in the insulating layer 103.

After the insulating layer 103 is formed, a gas-sensitive electrode groove is formed in the insulating layer 103 by using the thick photoresist praseodymium Pr as a mask and a dry etching process. Specifically, a layer of photoresist is spin-coated on the upper surface of the insulating layer 103, the gas-sensitive electrode groove is exposed through exposure and development, and then a gas-sensitive electrode groove is etched in the insulating layer 103 according to the gas-sensitive electrode groove through a dry etching technology. The thickness of the gas-sensitive electrode groove can be determined according to the etching speed of the dry etching equipment. For example, the etching speed is 5 microns/second, and the etching speed is 1 second, so that the thickness of the groove of the gas sensing electrode is 5 microns.

After the gas-sensitive electrode groove is formed, photoresist exists in the gas-sensitive electrode groove, and the photoresist needs to be exposed and developed again to expose the gas-sensitive electrode groove. And depositing metals, mainly titanium (Ti) and platinum (Pt), in the groove of the gas sensing electrode to form a gas sensing electrode 105 embedded in the insulating layer 103, wherein the upper surface of the gas sensing electrode 105 is at the same level with the upper surface of the insulating layer 103. Specifically, in the gas sensing electrode groove, Ti and Pt are deposited by an evaporation or sputtering method, wherein Ti and Pt are also required to be deposited in the gas sensing electrode groove. Then, by a resist stripping and stripping process, the gas sensing electrode 105 embedded in the insulating layer 103 is formed.

If the photoresist in the gas-sensitive electrode groove is thick, the gas-sensitive electrode groove cannot be exposed after exposure again, and the photoresist in the gas-sensitive electrode groove and on the insulating layer 103 needs to be removed by using a photoresist solution. A thin layer of photoresist is coated again, and then the gas-sensitive electrode groove is exposed by exposure and development. Then, metal is deposited in the groove of the gas sensing electrode to form the gas sensing electrode 105.

In this embodiment, the gas sensing electrode 105 is embedded in the insulating layer 103, and the upper surface of the gas sensing electrode 105 and the upper surface of the insulating layer 103 are in the same horizontal plane, which provides a basis for forming the gas sensing film 108 in the following step and improves the forming efficiency of the gas sensing film 108.

In addition, in an actual process, a portion of the gas sensing electrode 105 embedded in the insulating layer 103 protrudes from the insulating layer 103, and after the gas sensing electrode 105 is formed, a Chemical Mechanical Polishing (CMP) technique is used to polish the portion of the gas sensing electrode 105 and the portion of the insulating layer 103 at the same level.

When the gas sensing electrode 105 embedded in the insulating layer 103 is formed, the gas sensor has been substantially partitioned into an active region and a non-active region. The gas-sensitive electrodes 105 in the active region are gas-sensitive interdigital electrodes, and the gas-sensitive interdigital electrodes in the active region are electrodes having a periodic pattern in a plane, such as a finger or comb, as shown in fig. 2. While the gas sensing electrode 105 in the non-active region is a conventional gas sensing electrode.

Aiming at the gas-sensitive interdigital electrode in the activation area, the method for forming the gas-sensitive interdigital electrode comprises the following steps: after the gas sensing electrode groove is formed, the photoresist is removed. In the activation area, fixing the gas sensor with the hard mask plate with the pores according to a certain angle, or fixing the hard mask plate and the equipment; ti and Pt are deposited by adopting an evaporation or sputtering method, the Ti is used as an adhesion layer, the thickness is about 50 angstroms, and the Ti and the Pt can penetrate through the pores of the hard mask to deposit in the grooves of the gas-sensitive electrode to form the gas-sensitive interdigital electrode.

Outside the activation region, namely outside the gas-sensitive interdigital electrode, the through hole 106 is etched and released by using a thick photoresist as a mask and a dry etching process. The etching solution is then flowed into the substrate 101 through the relief via 106, and reacts with the substrate to form a cavity 107. Wherein, the etching liquid is silicon etching liquid with special components. At this time, the release via 106 penetrates the dielectric layer 102 and the insulating layer 103 and communicates with the cavity 107. And the formed cavity is arranged in the substrate and is arranged in the area corresponding to the gas-sensitive interdigital electrode, namely the area corresponding to the activation area.

In the present embodiment, the formation of the relief via 106 and the cavity 107 is to prevent the rapid heat transfer of the micro-heater and reduce the loss of the device. Among them, the insulating layer 103, the heating electrode 104, and the gas-sensitive electrode 105 are referred to as a micro-heater.

After the formation of the relief through-holes 106 and the cavities 107, the deposited gas sensor of the gas-sensitive interdigital electrodes is annealed. The gas-sensitive film 108 is deposited by Glancing Angle Deposition (GLAD for short) by placing a hard mask with pores on the active region, i.e. on the gas-sensitive interdigital electrode. The gas-sensitive membrane 108 thus formed is a fluffy membrane, with a smooth surface, good height consistency, and uniform membrane layer density and thickness distribution. When the gas-sensitive film 108 is formed, the method also increases the surface area of the film, and improves the reaction sensitivity of the gas-sensitive film 108 and the detected gas.

One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

in this embodiment, the gas sensing electrode is sunk in the insulating layer, and the upper surface of the gas sensing electrode and the upper surface of the insulating layer are at the same level. Therefore, when the gas-sensitive film is deposited subsequently, the thickness and the density of the gas-sensitive film can be uniformly distributed, the surface area of the formed gas-sensitive film is increased, and the sensitivity of the gas sensor is improved.

Example two

Based on the same inventive concept, a second embodiment of the present invention further provides a method for manufacturing a MEMS gas sensor, as shown in fig. 3, including:

s201: forming a dielectric layer on a substrate;

s202: forming an insulating layer on the dielectric layer;

s203: forming a gas-sensitive electrode groove in the insulating layer;

s204: and forming a gas-sensitive electrode embedded in the insulating layer in the groove of the gas-sensitive electrode, wherein the upper surface of the gas-sensitive electrode and the upper surface of the insulating layer are positioned at the same horizontal plane.

After step S202, that is, after forming a dielectric layer on the substrate, the method further includes:

and forming a heating electrode above the dielectric layer by using the thick photoresist as a mask and a dry etching process. Specifically, a layer of photoresist is coated on the upper surface of the dielectric layer in a spinning mode, light passes through a mask plate, the photoresist is exposed, and the micro-heater groove is exposed through development. A layer of metal is then deposited on the photoresist by an evaporation technique, wherein the metal also needs to be deposited in the micro-heater pocket. Then, a heating electrode is formed on the dielectric layer through a photoresist stripping process.

After the heating electrode is formed, an insulating layer is formed on the heating electrode. Thus, the heating electrode is disposed in the insulating layer.

After the insulating layer is formed, a gas-sensitive electrode groove is formed in the insulating layer by taking the thick photoresist praseodymium Pr as a mask and adopting a dry etching process. Specifically, a layer of photoresist is coated on the upper surface of the insulating layer in a spinning mode, the gas-sensitive electrode groove is exposed through exposure and development, and then the gas-sensitive electrode groove is etched in the insulating layer according to the gas-sensitive electrode groove through a dry etching technology. The thickness of the gas-sensitive electrode groove can be determined according to the etching speed of the dry etching equipment.

After the gas-sensitive electrode groove is formed, photoresist exists in the gas-sensitive electrode groove, and the photoresist needs to be exposed and developed again to expose the gas-sensitive electrode groove. And depositing metal in the groove of the gas-sensitive electrode, wherein the metal mainly comprises titanium (Ti) and platinum (Pt) to form the gas-sensitive electrode embedded in the insulating layer, and the upper surface of the gas-sensitive electrode and the upper surface of the insulating layer are positioned on the same horizontal plane. Specifically, in the gas sensing electrode groove, Ti and Pt are deposited by an evaporation or sputtering method, wherein Ti and Pt are also required to be deposited in the gas sensing electrode groove. Then, a gas sensing electrode embedded in the insulating layer is formed through a stripping and stripping process.

When forming the gas sensing electrode embedded in the insulating layer, the gas sensor has been substantially partitioned into an active region and a non-active region. The gas-sensitive electrodes in the activation region are gas-sensitive interdigital electrodes, and the gas-sensitive interdigital electrodes in the activation region are electrodes with periodic patterns in the plane, such as fingers or combs, as shown in fig. 2. And the gas-sensitive electrode in the non-activation region is a common gas-sensitive electrode.

And outside the activation region, namely outside the gas-sensitive interdigital electrode, etching to release the through hole by using a thick photoresist as a mask and a dry etching process. And then, the corrosive liquid flows into the substrate through the release through hole to form a cavity. At this time, the release via penetrates the dielectric layer and the insulating layer and communicates with the cavity.

In this embodiment, the formation of the relief through hole and the cavity is to ensure that heat is not dissipated in the substrate, thereby preventing the current in the gas sensor from flowing too fast and causing loss.

And after forming the release through hole and the cavity, annealing the deposited gas sensor of the gas-sensitive interdigital electrode with the alloy. The gas-sensitive film is deposited by a Glancing Angle Deposition (GLAD for short) method by arranging a hard mask plate with pores on an activation area, namely on a gas-sensitive interdigital electrode. The gas-sensitive membrane formed in this way is a fluffy membrane, the surface is flat, the height consistency is good, and the density and the thickness distribution of the membrane layer are uniform. When the method forms the gas-sensitive film, the surface area of the film is also increased, and the reaction sensitivity of the gas-sensitive film and the detected gas is improved.

As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.