Micro-electromechanical sensing device and sensing module thereof

Abstract

A micro-electro-mechanical sensing device and a sensing module thereof are disclosed. The micro-electro-mechanical sensing device includes a substrate, a heater, and a sensing electrode. The heater is disposed on the substrate and has a heating working portion. The sensing electrode has a sensing working portion. The heater and the sensing electrode are disposed at different layers along a stacking direction, and the sensing electrode is electrically insulated from the heater. On a reference surface in the stacking direction, a projection of the heating working portion of the heater covers a projection of the sensing working portion of the sensing electrode.

Description

TECHNICAL FIELD

[0001] The present application relates to a micro-electro-mechanical sensing device and a sensing module. BACKGROUND

[0002] For public safety and public health, it is very important to efficiently detect industrial toxic gases, flammable and explosive gases, dangerous gases in chemical laboratories, and disease-related harmful gases. Developing a gas sensing device with high sensitivity, high selectivity, fast response rate, and long service life is also one of the goals of the industry.

[0003] The excellent gas sensing characteristics of some semiconductor materials and metal oxides have been discovered and further applied to the manufacture of micro-electro-mechanical gas sensing devices. Generally speaking, semiconductor materials and metal oxides must be at a certain temperature to have gas sensing characteristics that meet application requirements, so such gas sensing devices often have a heating element installed to allow the gas sensing device to be at the proper operating temperature.

[0004] With the development trend of miniaturization of gas sensing devices, the internal sensing electrode usually adopts a finger electrode structure to reduce resistance. In existing gas sensing devices, the finger electrode structure is formed on the heater, but since the circuit pattern of the finger electrode structure crosses the heater, it causes problems such as disconnection or incomplete etching of the finger electrode structure during manufacturing, ultimately resulting in reduced sensitivity of the gas sensing device or even becoming a defective product. In addition, the design of the finger electrode structure crossing the heater also has the problem of uneven heating of the finger electrode structure and local thermal stress accumulation, and the finger electrode structure is prone to deformation after long-term use. SUMMARY

[0005] In view of the above problems, the present application provides a micro-electro-mechanical sensing device and a sensing module in which the electrode can be uniformly heated by the heater and has a high manufacturing yield.

[0006] The micro-electro-mechanical sensing device disclosed in an embodiment of the present application includes a substrate, a heater, and a sensing electrode. The heater is disposed on the substrate, and the heater has a heating working portion. The sensing electrode has a sensing working portion. The heater and the sensing electrode are disposed at different layers along a stacking direction, and the sensing electrode is electrically insulated from the heater. On a reference surface in the stacking direction, the projection of the heating working portion of the heater covers the projection of the sensing working portion of the sensing electrode.

[0007] The sensing module disclosed in an embodiment of the present application comprises a heater and a sensing electrode. The heater has a heating working portion, and the sensing electrode has a sensing working portion. The heater and the sensing electrode are arranged at different layers along a stacking direction, and the sensing electrode is electrically insulated from the heater. On a reference surface in the stacking direction, the projection of the heating working portion of the heater covers the projection of the sensing working portion of the sensing electrode.

[0008] According to the micro-electro-mechanical sensing device and the sensing module disclosed in the present application, the projections of the heating working portion and the sensing working portion on the reference surface overlap, and the projection of the heating working portion covers the projection of the sensing working portion. Such a structural design helps to avoid the occurrence of height difference when manufacturing the sensing electrode, and thus helps to avoid the breakage of the weak structure part or incomplete etching caused by the height difference, and helps to improve the manufacturing yield. In addition, such a structural design allows all parts of the sensing working portion to be uniformly heated by the heater, and helps to avoid the deformation of the sensing electrode caused by the local thermal stress accumulation, and thus helps to increase the service life of the micro-electro-mechanical sensing device.

[0009] The above description of the present application and the following description of the embodiments are used to demonstrate and explain the principles of the present application, and provide further explanation of the claims of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 FIG. 1 is a perspective view of a micro-electro-mechanical sensing device according to an embodiment of the present application;

[0011] Figure 2 FIG. 2 is an exploded view of the micro-electro-mechanical sensing device of FIG. 1; Figure 1

[0012] Figure 3 FIG. 3 is a sectional view of the micro-electro-mechanical sensing device of FIG. 1; Figure 1

[0013] Figure 4 FIG. 4 is a perspective view of a sensing module in the micro-electro-mechanical sensing device of FIG. 1; Figure 1

[0014] Figure 5 FIG. 5 is a top view of the sensing module of FIG. 4; Figure 4

[0015] Figure 6 FIG. 6 is a view of the sensing module of FIG. 4 and a prior art sensing module; Figure 5

[0016] Figure 7 FIG. 7 is a perspective view of a sensing module according to another embodiment of the present application.

[0017] LIST OF SYMBOLS

[0018] 1 micro-electro-mechanical sensing device​​​​​

[0019] 10 substrate

[0020] 20, 20b sensing module

[0021] 110 substrate

[0022] 120 insulating film

[0023] 121 protrusion

[0024] 100 thermal insulation cavity

[0025] 20 sensing module

[0026] 210 heater

[0027] 211 heating working portion

[0028] 2111 outer frame area

[0029] 2111b bending structure

[0030] 2112 connecting area

[0031] 2113 disc area

[0032] 212 heater connecting arm

[0033] 220 sensing electrode

[0034] 221 sensing working portion

[0035] 2211 fork structure

[0036] 2211b working electrode

[0037] 222 electrode connecting arm

[0038] 230 electrically insulating layer

[0039] D stacking direction

[0040] d distance

[0041] S reference surface

[0042] P1, P2 projection

[0043] CR position of sensing electrode across heater DETAILED DESCRIPTION

[0044] The specific features and advantages of the present application are described in detail in the following embodiments, which are sufficient to enable a person of ordinary skill in the art to understand the technical content of the present application and to implement the same, and any person of ordinary skill in the art can easily understand the related purposes and advantages of the present application according to the content disclosed in the specification, claims and drawings. The following embodiments are further detailed to illustrate the present application, but do not limit the scope of the present application in any way.

[0045] Please refer to Figures 1 to 3 , wherein Figure 1 is a perspective view of a micro-electro-mechanical sensing device according to an embodiment of the present application, Figure 2 is Figure 1 an exploded view of the micro-electro-mechanical sensing device of Figure 3 is Figure 1 a sectional view of the micro-electro-mechanical sensing device of In this embodiment, the micro-electro-mechanical sensing device 1 comprises a substrate 10 and a sensing module 20.

[0046] The substrate 10 comprises a substrate 110 and an insulating film 120 disposed on the substrate 110. The substrate 110 is, for example but not limited to, a silicon substrate or a glass substrate, and the insulating film 120 is, for example but not limited to, silicon oxide. The insulating film 120 has a protruding portion 121, and a thermal isolation cavity 100 is formed between the substrate 110 and the protruding portion 121. In more detail, a sacrificial layer (not shown separately) can be first formed on a predetermined region on the surface of the substrate 110, then the insulating film 120 is formed above the substrate 110 and the sacrificial layer, and then the sacrificial layer is removed, so that the space originally occupied by the sacrificial layer becomes the thermal isolation cavity 100.

[0047] The sensing module 20 comprises a heater 210, a sensing electrode 220 and an electrically insulating layer 230. Please refer to Figure 4 and Figure 5 , wherein Figure 4 is Figure 1 a perspective view of the sensing module in the micro-electro-mechanical sensing device of Figure 5 is Figure 4FIG. 2 is a top view of a sensing module according to an embodiment of the present application. A heater 210, such as but not limited to a resistive heater, is disposed on a substrate 10, and the heater 210 has a heating working portion 211. More specifically, the heater 210 includes the heating working portion 211 and a heater connecting arm 212, and the heating working portion 211 corresponds to the thermal insulation cavity 100. The thermal insulation cavity 100 can reduce the heat energy transferred to the substrate 110 to decrease heat loss. The heating working portion 211 of the heater 210 includes an outer frame region 2111, a linking region 2112, and a disc region 2113. The outer frame region 2111 surrounds the linking region 2112 and the disc region 2113, and the disc region 2113 is connected to the outer frame region 2111 via the linking region 2112. The heating working portion 211 is connected to an external power source (not shown) via the heater connecting arm 212 to provide current to allow the heater 210 to increase in temperature.

[0048] A sensing electrode 220, such as but not limited to a semiconductor or a metal oxide with good gas sensing properties, is disposed on a different layer than the heater 210 along the stacking direction D. More specifically, the sensing electrode 220 is disposed above the heater 210 along the stacking direction D, and the sensing electrode 220 includes a sensing working portion 221 and an electrode connecting arm 222. The sensing working portion 221 has a finger structure 2211 corresponding to the heating working portion 211. The sensing working portion 221 is connected to an external readout circuit (not shown) via the electrode connecting arm 222 to generate an electrical signal. The sensing electrode 220 of the present embodiment is stacked above the heater 210, but the present application is not limited thereto. In other embodiments, the sensing electrode can be disposed on the substrate first, and then the heater is stacked above the sensing electrode.

[0049] In the present embodiment, the heating working portion 211 of the heater 210 refers to the portion of the heater 210 that substantially increases in temperature when the heater 210 is powered. The sensing working portion 221 of the sensing electrode 220 refers to the portion of the sensing electrode 220 that is substantially affected by the heater 210, or the portion that substantially has the gas sensing properties required for the application. In addition, in some embodiments, the sensing working portion 221 preferably refers to all portions of the heater 210 that are substantially heated or have the specified gas sensing properties, such as the sensing working portion 221 described in FIG. 1, which encompasses all of the branch electrodes in the finger structure 2211 and all regions of each branch electrode, rather than only some of the branch electrodes or only some of the regions of each branch electrode. Figure 5

[0050] ​An electrically insulating layer 230, such as, but not limited to, a non-conductive heat-resistant plastic or oxide, is disposed between the heater 210 and the sensing electrode 220 to electrically insulate the sensing electrode 220 from the heater 210. Specifically, the electrically insulating layer 230 is disposed on the heater 210 to cover the sensing electrode 220, thereby spatially separating the heater 210 and the sensing electrode 220. The sensing electrode 220 is disposed on the electrically insulating layer 230.

[0051] like Figure 4 As shown, on the virtual projection reference plane S in the stacking direction D, the projection of the heating working portion 211 of the heater 210 covers the projection of the sensing working portion 221 of the sensing electrode 220. Furthermore, on the reference plane S, the projections of the heating working portion 211 and the heater connecting arm 212 respectively cover the projections of the sensing working portion 221 and the electrode connecting arm 222. That is, the projection P1 of the heater 210 completely covers the projection P2 of the sensing electrode 220, and the area of ​​projection P1 can be larger than the area of ​​projection P2. The ratio of the projected area of ​​the heater 210 (including the portion overlapping with the projection of the sensing electrode 220 and the portion not overlapping) to the projected area of ​​the sensing electrode 220 can be 2:1, in other embodiments it can be 3:1, and in other embodiments it can be 4:1. Furthermore, as... Figure 5 As shown, the distance d between the outermost edge of the outer frame region 2111 of the heating working part 211 and the outermost edge of the finger structure 2211 of the sensing working part 221 (i.e. the outermost edge of the outermost ring branch electrode) is 0.1 to 0.3 micrometers (μm) to ensure the production yield of the sensing module 20.

[0052] The temperature of the heating working part 211 of the heater 210 can be adjusted to maintain the temperature of the sensing working part 221 of the sensing electrode 220 at a suitable operating temperature. When the sensing working part 221 adsorbs gas and generates a change in resistance, the external reading circuit can obtain the change in voltage or current, and thus determine the type and concentration of the gas.

[0053] In this embodiment, the sensing electrode 220 is disposed above the heater 210, and the sensing working portion 221 of the sensing electrode 220 extends in conjunction with the heating working portion 211 of the heater 210. That is, the projections of the heating working portion 211 and the sensing working portion 221 on the same reference plane S overlap, and the projection of the heating working portion 211 covers the projection of the sensing working portion 221. This means that the sensing working portion 221 of the sensing electrode 220 will not protrude laterally from the heater 210, nor will it cross between any two of the outer frame area 2111, the connecting area 2112, and the disk area 2113 of the heating working portion 211. This avoids the topography phenomenon during the manufacturing of the sensing electrode 220, thereby avoiding the breakage or incomplete etching of structurally fragile parts caused by the topography phenomenon, which helps to improve the manufacturing yield.

[0054] Furthermore, since the sensing working part 221 does not cross the structure in the heating working part 211, all parts of the sensing working part 221 can be uniformly heated by the heater 210, which helps to avoid the problem of deformation of the finger structure 2211 due to local thermal stress accumulation, and helps to increase the service life of the microelectromechanical sensing device 1.

[0055] Figure 6 for Figure 5 A schematic diagram comparing the new sensing module with existing sensing modules. Figure 5 Sensing module 20 ( Figure 6 (a) and the sensing module in existing resistive gas sensing devices where the sensing electrode spans the heater ( Figure 6 The comparison is made between (b) and (c). Under the same heater temperature, it can be observed that the existing sensing module has a higher temperature at the location CR where the sensing electrode crosses the heater than other areas of the sensing electrode. Therefore, local thermal stress accumulation is prone to occur at the location CR where the sensing electrode crosses the heater. In contrast, the sensing working part 221 of the sensing module 20 in this embodiment has a more uniform temperature, thus alleviating the problem of local thermal stress accumulation.

[0056] Furthermore, in this embodiment, the heater 210 and the sensing electrode 220 are disposed on different layers along the stacking direction D. For example, the heater 210 and the sensing electrode 220 are formed separately in two different steps of the manufacturing process, and the heater 210 and the sensing electrode 220 are not on the same horizontal plane. As a result, a sufficiently large gap can be provided between the outer frame region 2111, the connecting region 2112, and the disk region 2113 of the heating working part 211 of the heater 210 to fill the electrically insulating layer 230, and the problem of short circuits caused by the heating working part 211 and the sensing working part 221 being too close is avoided.

[0057] Figure 7FIG. 6 is a perspective view of a sensing module according to another embodiment of the present application. In this embodiment, the sensing module 20b of the micro-electro-mechanical sensing device comprises a heater 210 and a sensing electrode 220. The heating working portion 211 of the heater 210 comprises a bending structure 2111b, which is in an S shape in the embodiment shown in FIG. 6. The sensing working portion 221 of the sensing electrode 220 comprises a pair of working electrodes 2211b, which extend along the bending structure 2111b and are arranged in parallel. Similar to the previous embodiments, the heater 210 and the sensing electrode 220 are arranged in different layers along the stacking direction D. In the virtual projection reference surface S of the stacking direction D, the projection of the heating working portion 211 of the heater 210 covers the projection of the sensing working portion 221 of the sensing electrode 220. Figure 7

[0058] In summary, according to the micro-electro-mechanical sensing device and the sensing module disclosed in the present application, the projection of the heating working portion and the projection of the sensing working portion overlap on the reference surface, and the projection of the heating working portion covers the projection of the sensing working portion, which helps to avoid the high-low difference phenomenon during the manufacturing of the sensing electrode, and further avoid the structure weak part broken line or incomplete etching caused by the high-low difference phenomenon, and helps to improve the manufacturing yield. All parts of the sensing working portion can be uniformly heated by the heater, which helps to avoid the problem of the sensing electrode deformation caused by the local thermal stress accumulation, and further increases the service life of the micro-electro-mechanical sensing device.​

Claims

1. A micro-electro-mechanical sensing device, comprising: a substrate; a heater disposed on the substrate, the heater having a heater active portion; and a sensing electrode having a sensing active portion, the heater and the sensing electrode being disposed at different layers along a stacking direction, and the sensing electrode being electrically insulated from the heater; wherein a projection of the heater completely covers a projection of the sensing electrode on a reference plane of the stacking direction, wherein the heater comprises the heater active portion and a heater connecting arm connected to the heater active portion, and the sensing electrode comprises the sensing active portion and an electrode connecting arm connected to the sensing active portion, wherein the projection of the heater active portion of the heater covers the projection of the sensing active portion of the sensing electrode, and the projection of the heater connecting arm covers the projection of the electrode connecting arm on the reference plane.

2. The micro-electro-mechanical sensing device of claim 1, wherein the substrate comprises a substrate plate and an insulating film disposed on the substrate plate, a thermally insulating cavity is formed between the substrate plate and the insulating film, and the heater active portion of the heater corresponds to the thermally insulating cavity.

3. The micro-electro-mechanical sensing device of claim 1, wherein the sensing active portion of the sensing electrode has a finger structure.

4. The micro-electro-mechanical sensing device of claim 1, wherein the heater active portion of the heater comprises an outer frame region, a linking region, and a disc region, the outer frame region surrounds the linking region and the disc region, and the disc region is connected to the outer frame region via the linking region.

5. The micro-electro-mechanical sensing device of claim 1, wherein the heater active portion of the heater comprises a bending structure.

6. The micro-electro-mechanical sensing device of claim 5, wherein the sensing active portion of the sensing electrode comprises a pair of active electrodes extending along the bending structure and arranged in parallel.

7. The micro-electro-mechanical sensing device of claim 1, further comprising an electrically insulating layer between the heater and the sensing electrode.

8. The micro-electro-mechanical sensing device of claim 1, wherein a projected area of the heater active portion is greater than a projected area of the sensing active portion.

9. The micro-electro-mechanical sensing device of claim 1, wherein a distance between an outermost edge of the heater active portion and an outermost edge of the sensing active portion is 0.1 to 0.3 micrometers.

10. A sensing module for detecting a gas concentration, comprising: a heater having a heater active portion; and a sensing electrode having a sensing active portion, the heater and the sensing electrode being disposed at different layers along a stacking direction, and the sensing electrode being electrically insulated from the heater; wherein a projection of the heater completely covers a projection of the sensing electrode on a reference plane of the stacking direction, wherein the heater comprises the heater active portion and a heater connecting arm connected to the heater active portion, and the sensing electrode comprises the sensing active portion and an electrode connecting arm connected to the sensing active portion, wherein the projection of the heater active portion of the heater covers the projection of the sensing active portion of the sensing electrode, and the projection of the heater connecting arm covers the projection of the electrode connecting arm on the reference plane.

11. The sensing module of claim 10, wherein the sensing active portion has a finger structure.

12. The sensing module of claim 10, wherein the heating working part comprises a frame region, a linking region, and a disc region, the frame region surrounds the linking region and the disc region, and the disc region is connected to the frame region via the linking region.

13. The sensing module of claim 10, wherein the heating working part comprises a bent structure.

14. The sensing module of claim 13, wherein the sensing working part comprises a pair of working electrodes extending along the bent structure and arranged in parallel.

15. The sensing module of claim 10, further comprising an electrically insulating layer between the heater and the sensing electrode.

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