阅读说明：本技术 内嵌式三维结构微加热板及制备方法、气体传感器 (Embedded three-dimensional structure micro-heating plate, preparation method and gas sensor ) 是由 李娜 安飞 金艳 姜慧芸 徐伟 姜杰 于 2020-04-10 设计创作，主要内容包括：本发明涉及气体传感器技术领域,公开一种内嵌式三维结构微加热板,包括硅基衬底和电极层,所述硅基衬底的表层设置有凹腔；所述电极层包括加热电极和测量电极,所述加热电极和所述测量电极嵌设于所述凹腔内。本发明的微加热板采用内嵌式电极层,通过凹腔结构为电极层提供支撑,机械稳定性好。由于加热电极嵌设于凹腔内,加热空间从完全暴露在环境中的平面结构优化为内嵌的腔体结构,其中心加热区域受环境气流影响小,热对流在腔体内进行,腔体内壁的热辐射恒定均匀,因此热量散失慢,热损耗低,能够降低微加热板的功耗。本发明的微加热板在降低功耗的情况下同时保证良好的机械稳定性。(The invention relates to the technical field of gas sensors and discloses an embedded three-dimensional structure micro-heating plate which comprises a silicon-based substrate and an electrode layer, wherein a concave cavity is formed in the surface layer of the silicon-based substrate; the electrode layer comprises a heating electrode and a measuring electrode, and the heating electrode and the measuring electrode are embedded in the concave cavity. The micro-heating plate adopts the embedded electrode layer, provides support for the electrode layer through the concave cavity structure, and has good mechanical stability. Because the heating electrode is embedded in the concave cavity, the heating space is optimized to be an embedded cavity structure from a plane structure which is completely exposed in the environment, the central heating area is slightly influenced by the environmental airflow, the heat convection is carried out in the cavity, and the heat radiation of the inner wall of the cavity is constant and uniform, so that the heat loss is slow, the heat loss is low, and the power consumption of the micro-heating plate can be reduced. The micro heating plate of the invention can ensure good mechanical stability under the condition of reducing power consumption.)

1. An embedded three-dimensional structure micro-heating plate comprises a silicon-based substrate and an electrode layer,

the surface layer of the silicon-based substrate is provided with a concave cavity;

the electrode layer comprises a heating electrode and a measuring electrode, and the heating electrode and the measuring electrode are embedded in the concave cavity.

2. The in-line three-dimensional micro-heating plate of claim 1, wherein the inner wall of the cavity has a curved surface, and the heating electrode and the measuring electrode are arranged along the inner wall of the cavity.

3. The in-line three-dimensional micro heating plate according to claim 1, wherein the cavity has a semi-elliptical or truncated cone shape, and the heating electrodes are arranged along an inner wall of the cavity in a regular shape.

4. The in-line three-dimensional micro-heating plate of claim 3, wherein the heating electrodes extend from the opening of the cavity to the bottom of the cavity in a stepped pattern.

5. The in-line three-dimensional structure micro heating plate according to claim 1, wherein a surface of the silicon-based substrate is provided with a heating electrode pad and a measuring electrode pad, the heating electrode is led out to the heating electrode pad, and the measuring electrode is led out to the measuring electrode pad.

6. The in-line three-dimensional micro-heating plate of claim 1, wherein the inner wall of the cavity is provided with a support layer, and the electrode layer is disposed on the support layer.

7. The in-line three-dimensional micro-heating plate of claim 6, wherein the material of the support layer is silicon oxide or silicon nitride.

8. The in-line three-dimensional micro-heating plate of claim 1, wherein an insulating layer is disposed between the heating electrode and the measuring electrode.

9. The in-line three-dimensional micro-heating plate of claim 1, wherein the cavity has a depth of 20-100 μm.

10. The in-line three-dimensional micro-heating plate of claim 1, wherein the heating electrode is made of any one of Pt, Au, and W.

11. A preparation method of an embedded three-dimensional structure micro-heating plate is characterized by comprising the following steps:

s1) providing a silicon-based substrate;

s2) manufacturing a concave cavity on the surface layer of the silicon-based substrate;

s3) forming an electrode layer in the cavity.

12. The method for preparing the micro heating plate with the embedded three-dimensional structure according to claim 10, wherein the step S3) of preparing the electrode layer in the cavity comprises the following steps:

s31) growing a supporting layer on the inner wall of the concave cavity;

s32) manufacturing a heating electrode on the supporting layer along the inner wall of the concave cavity;

s33) growing an insulating layer on the surface of the heating electrode;

s34) forming a measuring electrode on the heating electrode having the insulating layer.

13. The method for manufacturing an embedded three-dimensional micro heating plate according to claim 10, wherein step S2) is performed to form a cavity on the surface layer of the silicon-based substrate, wherein the cavity is formed by a method comprising:

and making a window pattern on the surface of the silicon-based substrate by adopting a photoetching process, and etching the cavity in the window pattern region by utilizing an ion etching process under the protection of photoresist.

14. The method of manufacturing an in-line three-dimensional micro heating plate according to claim 10, wherein the step S32) of manufacturing a heating electrode on the supporting layer along the inner wall of the cavity comprises:

and manufacturing a sacrificial layer on the inner wall of the cavity, forming an image of the heating electrode on the inner wall of the cavity through a photoetching process, and etching the heating electrode to the sacrificial layer through an etching process.

15. A gas sensor comprising the in-line three-dimensional structured micro-heating plate of any one of claims 1 to 10.

Technical Field

The invention relates to the technical field of gas sensors, in particular to an embedded three-dimensional structure micro-heating plate, a preparation method of the embedded three-dimensional structure micro-heating plate and a gas sensor.

Background

Gas sensors are mainly classified into electrochemical type, semiconductor type, thermal conduction type, optical type, and the like, and among them, semiconductor gas sensors are widely used because of high detection sensitivity, short response recovery time, small element size, and long life. In recent years, with the development of micromachining technology, semiconductor gas sensors are becoming more integrated and intelligent. The core of the micro gas sensor is a micro hot plate silicon-based structure with a heating electrode and a measuring electrode integrated on a substrate. The structure of the micro-hot plate is divided into two types, namely a closed film type and a cantilever beam type. The closed thin film structure is formed by hollowing out the silicon substrate from the back surface by utilizing the anisotropic corrosion of silicon, and the cantilever beam structure realizes thermal isolation by at least two suspended superfine cantilevers. The micro-hotplate with the closed film structure adopts a flat heating structure, and obvious heat loss can occur when the fluid speed on the surface of the micro-hotplate is too high or unstable; the cantilever beam structure reduces heat loss and reduces the power consumption of the micro-hotplate through the extremely fine cantilever with a high length-width ratio, but the mechanical strength is low easily caused by the overhigh length-width ratio of the cantilever, so that the mechanical strength of the micro-hotplate is reduced while the power consumption is reduced.

In addition, the electrode layer of the micro-hotplate with the closed thin film structure and the cantilever beam structure is of a planar structure, and when a sensing layer is integrated on the electrode layer by adopting a dripping method, a coffee ring effect is easily generated. The coffee ring effect refers to the phenomenon that when a colloidal droplet adheres to a solid surface, the colloidal particles suspended in the droplet are usually deposited in a ring shape. When the sensing layer is dripped on the micro-hotplate, the edge of the dripping area forms a dark ring which is much darker than the color of the middle area due to the coffee ring effect, the phenomenon of uneven deposition of the sensing material occurs, the sensing material cannot be heated uniformly, and the detection result is greatly influenced.

Disclosure of Invention

The invention aims to provide an embedded three-dimensional structure micro-heating plate and a preparation method thereof, which are used for reducing the power consumption of the micro-heating plate and solving the problem of uneven deposition of sensing materials caused by the coffee ring effect when a sensing layer is integrated by a drip method.

The invention provides an embedded three-dimensional structure micro-heating plate, which comprises a silicon-based substrate and an electrode layer, wherein a concave cavity is formed in the surface layer of the silicon-based substrate; the electrode layer comprises a heating electrode and a measuring electrode, and the heating electrode and the measuring electrode are embedded in the concave cavity.

Further, the inner wall of the cavity is of a curved surface structure, and the heating electrode and the measuring electrode are arranged along the inner wall of the cavity.

Further, the concave cavity is in a semi-elliptical shape or a frustum shape, and the heating electrodes are arranged along the inner wall of the concave cavity in a regular shape.

Further, the heating electrode extends from the opening of the concave cavity to the bottom of the concave cavity and is distributed in a step shape.

Furthermore, a heating electrode pad and a measuring electrode pad are arranged on the surface of the silicon-based substrate, the heating electrode is led out to the heating electrode pad, and the measuring electrode is led out to the measuring electrode pad.

Further, a supporting layer is arranged on the inner wall of the cavity, and the electrode layer is arranged on the supporting layer.

Further, the material of the support layer is silicon oxide or silicon nitride.

Further, an insulating layer is arranged between the heating electrode and the measuring electrode.

Further, the depth of the concave cavity is 20-100 μm.

Further, the material of the heating electrode is any one of Pt, Au and W.

The invention provides a preparation method of an embedded three-dimensional structure micro-heating plate, which comprises the following steps:

s1) providing a silicon-based substrate;

s2) manufacturing a concave cavity on the surface layer of the silicon-based substrate;

s3) forming an electrode layer in the cavity.

Further, step S3) of forming an electrode layer in the cavity includes the following steps:

s31) growing a supporting layer on the inner wall of the concave cavity;

s32) manufacturing a heating electrode on the supporting layer along the inner wall of the concave cavity;

s33) growing an insulating layer on the surface of the heating electrode;

s34) forming a measuring electrode on the heating electrode having the insulating layer.

Further, step S2) is to form a cavity on the surface layer of the silicon-based substrate, and the method for forming the cavity includes:

and making a window pattern on the surface of the silicon-based substrate by adopting a photoetching process, and etching the cavity in the window pattern region by utilizing an ion etching process under the protection of photoresist.

Further, step S32) of manufacturing a heating electrode on the support layer along the inner wall of the cavity includes:

and manufacturing a sacrificial layer on the inner wall of the cavity, forming an image of the heating electrode on the inner wall of the cavity through a photoetching process, and etching the heating electrode to the sacrificial layer through an etching process.

The invention provides a gas sensor, which comprises the embedded three-dimensional structure micro-heating plate.

The micro-heating plate adopts the embedded electrode layer, provides support for the electrode layer through the concave cavity structure, and has good mechanical stability. Because the heating electrode is embedded in the concave cavity, the heating space is optimized to be an embedded cavity structure from a plane structure which is completely exposed in the environment, the central heating area is slightly influenced by the environmental airflow, the heat convection is carried out in the cavity, and the heat radiation of the inner wall of the cavity is constant and uniform, so that the heat loss is slow, the heat loss is low, and the power consumption of the micro-heating plate can be reduced. The micro heating plate of the invention can ensure good mechanical stability under the condition of reducing power consumption.

In addition, because the measurement area of the micro-heating plate of the embodiment is the cavity structure, when the sensing layer is integrated by adopting a dripping method, sensing slurry only needs to be dripped into the concave area, so that the dripping positioning is convenient. In the drying and aging process of the sensing slurry, the sensing layer forms a flat surface attached to the wall surface based on the tension action between the inner wall of the cavity and the slurry, so that the coffee ring effect is avoided in the forming process of the sensing layer, and the problem of uneven deposition of the sensing material is solved. Moreover, the cavity structure is beneficial to completing the instillation operation by adopting a method for controlling the volume of the sensing slurry during instillation, simplifies the processing method and avoids the problem of low measurement precision caused by pollution caused by overflow of the slurry to a measurement area due to improper operation.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the embodiments of the invention without limiting the embodiments of the invention. In the drawings:

fig. 1 is a schematic structural diagram of an embedded three-dimensional micro-heating plate according to an embodiment of the present invention;

FIG. 2 is a top view of a cavity of an embedded three-dimensional micro-heating plate according to an embodiment of the present invention;

FIG. 3 is a cross-sectional view of an embedded three-dimensional micro-heating plate according to an embodiment of the present invention;

FIG. 4 is a top view of a cavity of an embedded three-dimensional micro-heating plate according to a second embodiment of the present invention;

FIG. 5 is a top view of a cavity of an embedded three-dimensional micro-heating plate according to a second embodiment of the present invention;

FIG. 6 is a cross-sectional view of an embedded three-dimensional micro-heating plate according to a second embodiment of the present invention;

fig. 7 is a flowchart of a method for manufacturing an embedded three-dimensional micro-heating plate according to a third embodiment of the present invention.

Description of the reference numerals

10-silicon based substrate, 20-cavity, 30-electrode layer, 31-heating electrode, 32-measuring electrode,

33-heating electrode pads, 34-measuring electrode pads, 40-support layer.

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

Example one

Fig. 1 is a schematic structural view of an embedded three-dimensional micro-heating plate according to an embodiment of the present invention, fig. 2 is a top view of a cavity of the embedded three-dimensional micro-heating plate according to an embodiment of the present invention, and fig. 3 is a cross-sectional view of the embedded three-dimensional micro-heating plate according to an embodiment of the present invention. Referring to fig. 1 to 3, the embedded three-dimensional micro-heating plate provided by the present embodiment includes a silicon-based substrate 10 and an electrode layer 30, wherein a cavity 20 is formed on a surface layer of the silicon-based substrate 10, and a depth of the cavity 20 is 20-100 μm. The electrode layer 30 includes a heating electrode 31 and a measuring electrode 32, and the heating electrode 31 and the measuring electrode 32 are embedded in the cavity 20. The inner wall of the cavity 20 is a curved surface structure, and the heating electrode 31 and the measuring electrode 32 are regularly arranged along the inner wall or the side wall of the cavity 20. In this embodiment, the cavity 20 has a semi-elliptical shape. As shown in fig. 2, the heating electrodes 31 are arranged in a circular ring shape along the inner wall of the cavity 20, and extend from the opening of the cavity 20 to the bottom of the cavity 20 in a stepped distribution, and the diameter of the circular ring-shaped heating electrode 31 gradually decreases from the opening to the bottom of the cavity 20. The silicon substrate 10 is a hexahedral structure, the cavity 20 is arranged on the upper surface of the silicon substrate 10, the heating electrode pad 33 and the measuring electrode pad 34 are arranged on the surface of the silicon substrate 10 adjacent to the outer edge of the cavity 20, the heating electrode 31 is led out to the heating electrode pad 33, and the measuring electrode 32 is led out to the measuring electrode pad 34. The measuring electrode 32 is a comb-shaped interdigital electrode, and an electrode pad of the interdigital electrode connected with an external circuit can be set to be a metal sheet pad with a wedge-shaped angle, so that the electrode pad is used for distinguishing a heating electrode pad from a measuring electrode pad, and the quick identification of an operator is facilitated.

Referring to fig. 3, the inner wall of the cavity 20 is provided with a support layer 40, and the electrode layer 30 is disposed on the support layer 40. The material of the support layer 40 is silicon oxide or silicon nitride with a low thermal conductivity, and the thickness of the support layer 40 is 300nm, so that the support layer has the effects of supporting and thermally isolating the electrode layer 30. An insulating layer (not shown in the drawings) is provided between the heating electrode 31 and the measuring electrode 32. The insulating layer is made of silicon oxide and has a thickness of 100-200 nm. For example, after the heating electrode 31 is formed on the support layer 40, a silicon oxide film with a thickness of 100nm is deposited on the surface of the heating electrode 31 as an insulating layer, and finally the measuring electrode 32 is fabricated. The insulating layer between the heating electrode 31 and the measuring electrode 32 isolates the heating electrode 31 and the measuring electrode 32 from each other, and avoids interference. The heating electrode and the measuring electrode are made of metal materials with high resistance temperature coefficients such as Pt, Au, W and the like.

Example two

Fig. 4 and 5 are top views of cavities of an embedded three-dimensional micro-heating plate according to a second embodiment of the present invention, and fig. 6 is a cross-sectional view of the embedded three-dimensional micro-heating plate according to the second embodiment of the present invention. Referring to fig. 4 to 6, the cavity 20 is disposed on the upper surface of the silicon-based substrate 10, and a heating electrode pad 33 is disposed on the surface of the silicon-based substrate 10 adjacent to the outer edge of the cavity 20, and the heating electrode 31 is led out to the heating electrode pad 33. The concave cavity 20 is in a frustum shape, and the heating electrodes 31 are regularly arranged along the side wall or the sunken bottom surface of the concave cavity 20. As shown in fig. 4, the heater electrode 31 is arranged along the side wall and the depressed bottom surface of the cavity 20 in an "S" shape, and extends from the opening of the cavity 20 to the depressed bottom surface of the cavity 20. As shown in fig. 5, the heating electrodes 31 are arranged in an inverted trapezoid along the side wall of the cavity 20, and extend from the opening of the cavity 20 to the depressed bottom surface of the cavity 20.

The micro-heating plate provided by the embodiment of the invention adopts the embedded electrode layer, and the concave cavity structure provides support for the electrode layer, so that the mechanical stability is good. Because the heating electrode is embedded in the concave cavity, the heating space is optimized to be an embedded cavity structure from a plane structure which is completely exposed in the environment, the central heating area is slightly influenced by the environmental airflow, the heat convection is carried out in the cavity, and the heat radiation of the inner wall of the cavity is constant and uniform, so that the heat loss is slow, the heat loss is low, and the power consumption of the micro-heating plate can be reduced.

In addition, because the measurement area of the micro-heating plate of the embodiment is the cavity structure, when the sensing layer is integrated by adopting a dripping method, sensing slurry only needs to be dripped into the concave area, so that the dripping positioning is convenient. In the drying and aging process of the sensing slurry, the sensing layer forms a flat surface attached to the wall surface based on the tension action between the inner wall of the concave cavity and the slurry, and the coffee ring effect is avoided in the forming process of the sensing layer. The sensing layer is formed after the sensing slurry is dried and aged, the sensing layer presents black shadow under a stereoscopic microscope, and the uniformity of the sensing material can be judged by observing the brightness of the shadow under the microscope. The sensing layer formed by dropping the sensing paste on the flat structure was observed under an optical microscope at a magnification of 50 times and a scale of 200 μm, and it was found that the shape of the sensing layer was not uniform and the edge thereof was deeper than the central region. However, the sensing layer formed by dripping the sensing paste in the cavity area is observed under an optical microscope, and the sensing layer is confined in the cavity and the color depth of the edge of the sensing layer and the color depth of the central area of the sensing layer are basically consistent. The observation shows that the micro heating plate with the concave cavity structure can avoid the coffee ring effect and solve the problem of uneven deposition of the sensing material.

Moreover, the cavity structure is beneficial to completing the instillation operation by adopting a method for controlling the volume of the sensing slurry during instillation, simplifies the processing method and avoids the problem of low measurement precision caused by pollution caused by overflow of the slurry to a measurement area due to improper operation.

EXAMPLE III

Fig. 7 is a flowchart of a method for manufacturing an embedded three-dimensional micro-heating plate according to a third embodiment of the present invention. Referring to fig. 7, the method for manufacturing an embedded three-dimensional micro-heating plate according to the embodiment includes the following steps:

s1) providing a silicon-based substrate.

The silicon substrate is preferably an n-type (100) silicon wafer of 4 inches and has a thickness of 200 to 550 μm.

S2) manufacturing a concave cavity on the surface layer of the silicon-based substrate.

And making a window pattern on the surface of the silicon-based substrate by adopting a photoetching process, and etching the cavity in the window pattern region by utilizing an ion etching process under the protection of photoresist. Specifically, a silicon oxide film with the thickness of 500nm is generated on the surface of a silicon wafer by adopting a chemical vapor deposition method, the front side is photoetched to form a window shape, the silicon oxide is exposed by adopting an RIE reactive ion etching method under the protection action of photoresist, and a corrosion window on the front side is etched; forming a cavity with a depth and width of 20-100 μm along the direction of the silicon wafer 110, and making a cavity structure with a semi-elliptical shape or an inverted trapezoid cross section by anisotropic etching.

S3) forming an electrode layer in the cavity.

Specifically, the manufacturing method of the electrode layer comprises the following steps:

s31) growing a supporting layer on the inner wall of the concave cavity.

In order to increase the supporting strength of the inner wall of the cavity, a silicon oxide film with the thickness of 200-600nm is grown on the inner wall of the cavity by using a chemical vapor deposition method as a supporting layer.

S32) forming a heating electrode on the support layer along the inner wall of the cavity.

And manufacturing a sacrificial layer on the inner wall of the cavity, forming an image of the heating electrode on the inner wall of the cavity through a photoetching process, and etching the heating electrode to the sacrificial layer through an etching process.

For example, a heating electrode lead and an electrode pad are formed in a cavity by means of photoetching and evaporation, a thin photoresist film is coated on the surface of a silicon wafer in a rotating mode, a photoresist solvent is partially evaporated by heating, then a pre-customized mask plate is used for accurate alignment, exposure is carried out on a specified area of the photoresist by using an ultraviolet photoetching technology, and metal evaporation with the thickness of 100-500nm is carried out on the exposed surface of the photoresist by using a vacuum evaporation mode. And putting the evaporated silicon wafer into an acetone solution to be soaked for 4-5 hours to dissolve the photoresist and wash away the redundant evaporated metal to form a heating electrode with the thickness of 0.2-1 mu m and two heating electrode leads. The heating electrode leads are arranged at the bottom and the side wall of the concave cavity, and the two heating electrode leads are respectively led out to the electrode bonding pad.

S33) growing an insulating layer on the surface of the heating electrode.

And depositing and growing a silicon oxide insulating layer with the thickness of 100-200nm on the surface of the heating electrode for preventing the interference between the heating electrode and the measuring electrode.

S34) fabricating a measuring electrode on the heating electrode having the insulating layer.

And manufacturing a measuring electrode, a measuring electrode lead and an electrode pad with the thickness of 0.2-1 mu m on the heating electrode along the concave cavity structure by adopting the same process as the process for manufacturing the heating electrode.

The embodiment of the invention also provides a gas sensor which comprises the embedded three-dimensional structure micro-heating plate.

Although the embodiments of the present invention have been described in detail with reference to the accompanying drawings, the embodiments of the present invention are not limited to the details of the above embodiments, and various simple modifications can be made to the technical solutions of the embodiments of the present invention within the technical idea of the embodiments of the present invention, and these simple modifications all fall into the protection scope of the embodiments of the present invention. The various features described in the foregoing detailed description may be combined in any suitable manner without departing from the scope of the invention. In order to avoid unnecessary repetition, the embodiments of the present invention will not be described separately for the various possible combinations.