KR100792165B1 - Gas sensor and manufactutring method thereof - Google Patents

Abstract

A gas sensor and a manufacturing method thereof are provided to increase supply and discharge speed of gas by using a micro-piezoelectric pump to improve gas sensing speed. A gas sensor includes a substrate(100), an insulation film(110), a sensing electrode(211), a heater electrode(212), a sensing film(251), a through-hole(101), a covering substrate(500), and a micro-pump(400). The insulation film, the sensing electrode and the heater electrode are sequentially disposed on the substrate. The sensing film is disposed on the insulation film, covering the sensing electrode and the heater electrode. The through-hole is disposed in a portion of the substrate corresponding to the sensing film, allowing a lower part of the insulation film to be exposed. The covering substrate is in contact with the insulation film, and has a gas communication channel(510), and first and second grooves which are disposed on a lower surface of the covering substrate. The micro-pump is disposed on an upper surface of the covering substrate corresponding to the second groove.

Description

 Gas sensor and its manufacturing method {Gas sensor and manufactutring method

1 is a cross-sectional view of a gas sensor according to the prior art

2 is a schematic cross-sectional view showing a state in which gas sensors are arrayed according to the prior art

3 is a schematic cross-sectional view of a gas sensor according to the present invention;

4A to 4D are schematic cross-sectional views illustrating a method of manufacturing a gas sensor according to the present invention.

5A and 5B are a plan view and a cross-sectional view showing a single device region of a gas sensor according to the present invention.

6 is a cross-sectional view showing a state in which a micro pump is mounted on a gas sensor according to another embodiment of the present invention.

7 is a cross-sectional view showing a substrate on which a micropump is installed according to another embodiment of the present invention.

8 is a plan view showing a substrate on which a micropump is installed according to another embodiment of the present invention.

9A and 9B are schematic cross-sectional views for explaining the micropump operation of the gas sensor according to the present invention.

10 is a cross-sectional view showing a state in which a plurality of sensing films are positioned inside a first groove of a gas sensor according to the present invention.

<Description of the symbols for the main parts of the drawings>

100: substrate 101,102: through hole

110, 111, 112: insulating film 210, 220, 230: electrode for a single device

211,221 sensing electrode 212,222 heater electrode

300: mask layer 311,312: opening

251,252,253: detection membrane 400: micro pump

410: lower electrode 420: piezoelectric body

430: upper electrode 510: gas distribution channel

521,522: home

The present invention relates to a gas sensor and a method for manufacturing the same. More specifically, the integration degree can be improved by vertically forming a through hole forming a membrane, and a micro pump is provided to smoothly supply gas. It relates to a gas sensor and a method of manufacturing the same that can improve the gas detection speed.

At present, the environmental problem, which is a global concern, can be divided into air environment, water environment, and soil environment according to the object.

Among these, air pollution, which is a cause of air pollution, can cause fatal harm to an unspecified number of people in a short time, as well as cause abnormal weather phenomena in the long term.

Therefore, it is necessary to actively monitor the air pollution source and to actively regulate the pollution source.

In addition, indoor air quality is also considered to be an important concern in the coming ubiquitous era, and thus the development of a portable gas sensor is required.

Such portable gas sensors require low power consumption and a small size structure due to the development and miniaturization of the electronics industry.

1 is a cross-sectional view of a gas sensor according to the prior art, which includes a silicon substrate 20 having a through hole 11 formed in a central region thereof; A membrane film 30 formed on the silicon substrate 20; A sensing electrode 40 and a heater electrode 50 formed on the membrane film 30 on which the through hole 11 is present; It surrounds the sensing electrode 40 and the heater electrode 50, and consists of a sensing film 60 formed on the membrane film 30.

Here, the metal oxides used as the sensing film are materials such as SnO ₂ , TiO ₂ , WO ₃ , ZnO, and the like, and in order to increase the sensitivity of gas detection to the base metal or measure various kinds of gases. In order to increase the selectivity, additives such as Pt, Pd, and Au are added.

In addition, a sensing electrode is formed to measure a change in electrical resistance of the sensing film.

When the sensing film heated to a predetermined temperature by the heater electrode is exposed to the gas, the gas sensor may react with the gas by adsorbing to the metal oxide of the sensing film, thereby increasing or decreasing the resistance of the metal oxide.

Therefore, the concentration of the gas is measured by measuring the resistance change of the metal oxide generated by gas adsorption using a sensing electrode.

On the other hand, the membrane (Membrane) is anisotropic wet etching of the silicon substrate with an etching solution of KOH or Tetra-methyl ammonium-hydroxide (TMAH), the back surface of the silicon substrate is removed in a trapezoidal cavity (cavity) structure, the silicon substrate Through-holes are formed, and the membrane film on the silicon substrate is floated by the through-holes to form a membrane.

As the membrane film, silicon nitride film (Si ₃ N ₄ ) or silicon oxynitride film (SiON _x ), which has a much lower etch rate than silicon during anisotropic wet etching, is used. These materials include low pressure chemical vapor deposition (LPCVD) processes. The technique is used to deposit and deposit on a silicon substrate.

FIG. 2 is a schematic cross-sectional view illustrating a state in which gas sensors are arrayed according to the related art. In the structure of FIG. 1, a plurality of sensing layers 61 and 62 are formed on the membrane layer 30. The films 61 and 62 surround the sensing electrodes and the heater electrodes, and through holes 11a and 11b are formed in the silicon substrate 20 corresponding to the sensing films 61 and 62.

As described above, the through holes 11a and 11b are formed by anisotropic wet etching, and thus are formed in a trapezoidal shape. In this case, as shown in FIG. 2, the through holes 11a and 11b have a membrane membrane ( 30, there are unnecessary 'A', 'B', 'C', 'D' areas that do not play a role to rise, there is a limit to improve the density.

In addition, it takes a long time of about 10 hours to form a trapezoidal through hole by silicon anisotropic wet etching, and breakage of a gas sensor element is easily caused by breakage of one gas sensor element in an anisotropic wet etching manufacturing process. .

In addition, in the conventional anisotropic wet etching method, a thin membrane of a rectangular or polygonal shape is formed when viewed from the top, and when such a membrane is continuously used at a high operating temperature, the thermal stress is concentrated on the edge of the polygonal membrane. There is a problem that can be structurally vulnerable.

In order to solve the problems described above, the present invention can improve the degree of integration by vertically forming a through hole forming a membrane, and is provided with a micro pump to facilitate the supply of gas to speed gas detection. An object of the present invention is to provide a gas sensor and a method of manufacturing the same.

A first preferred aspect for achieving the above objects of the present invention is

A substrate;

An insulating film formed on the substrate;

A plurality of single element electrodes formed on the insulating film, each of which comprises a sensing electrode and a heater electrode;

A plurality of sensing films surrounding the single device electrodes and formed on the insulating film;

A gas sensor is formed in the substrate region corresponding to the sensing film, and is formed of a plurality of through holes exposing a lower portion of the insulating film and having sidewalls perpendicular to the insulating film.

A second preferred aspect for achieving the above objects of the present invention is

A substrate;

An insulating film formed on the substrate;

A sensing electrode and a heater electrode formed on the insulating film;

A sensing film surrounding the sensing electrode and the heater electrode and formed on the insulating film;

A through hole formed in the substrate region corresponding to the sensing layer and exposing a lower portion of the insulating layer;

A gas distribution channel joined to the insulating film and connected from one side to the other side is formed in the lower surface, and first and second grooves connected to the gas distribution channel are formed in the lower surface, and the first groove is formed. A cover substrate having a sensing film positioned therein;

There is provided a gas sensor comprising a micropump formed on an upper surface of a cover substrate corresponding to the second groove.

A third preferred aspect for achieving the above objects of the present invention is

Sequentially forming a first insulating film and a second insulating film on the substrate;

Forming a plurality of electrodes for a single element including a sensing electrode and a heater electrode on the substrate;

Forming a plurality of sensing layers respectively surrounding the single device electrodes on the second insulating layer;

Forming a mask layer having an opening corresponding to each of the plurality of sensing layers under the substrate;

Masking the substrate with the mask layer to etch the substrate to form a plurality of through holes in the substrate to expose the lower portion of the first insulating layer;

There is provided a method of manufacturing a gas sensor comprising the step of removing the mask layer.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

3 is a schematic cross-sectional view of a gas sensor according to the present invention, comprising: a substrate 100; An insulating film 110 formed on the substrate 100; A plurality of single element electrodes 210 and 220 formed on the insulating layer 110 and formed of a sensing electrode and a heater electrode, respectively; A plurality of sensing layers 251 and 252 surrounding the single element electrodes 210 and 220, respectively, and formed on the insulating layer 110; A plurality of through holes 101 and 102 are formed in a region of the substrate 100 corresponding to the sensing layers 251 and 252, and expose a lower portion of the insulating layer 110 and have sidewalls perpendicular to the insulating layer 110. .

Here, the single element electrodes 210 and 220 are defined as electrodes required to detect gas in one sensing layer.

Accordingly, the gas sensor of the present invention has the advantage of forming through holes 101 and 102 having sidewalls perpendicular to the insulating film 110, thereby improving the degree of integration of the arrayed gas sensors.

Therefore, more gas sensors can be arrayed per unit area.

Here, the substrate 100 is a silicon substrate, and the insulating film 110 is preferably formed in a structure in which a silicon oxide film and a silicon nitride film are laminated by a manufacturing method described later.

4A to 4D are schematic cross-sectional views illustrating a method of manufacturing a gas sensor according to the present invention. First, as shown in FIG. 4A, a first insulating film 111 and a second insulating film 112 are formed on an upper portion of a substrate 100. Form sequentially.

Here, an insulating film made of a single material may be formed on the substrate 100.

The substrate 100 is a silicon substrate, the first insulating film 111 is a silicon oxide film, and the second insulating film 112 is preferably a silicon nitride film.

At this time, a silicon oxide film is formed on the silicon substrate by using a LPCVD deposition or a silicon wet thermal oxidation process, and a silicon nitride film is deposited to a thickness of 1 to 2 μm by an LPCVD deposition process on the silicon oxide film.

Thereafter, a plurality of single element electrodes 210 and 220 including a sensing electrode and a heater electrode are formed on the substrate 100 (FIG. 4B).

Here, the single element electrodes 210 and 220 include sensing electrodes 211 and 221 and heater electrodes 212 and 222, respectively.

Subsequently, a plurality of sensing layers 251 and 252 are formed on the second insulating layer 112 to surround the single device electrodes 210 and 220, respectively.

Subsequently, a mask layer 300 having openings 311 and 312 corresponding to each of the plurality of sensing layers 251 and 252 is formed under the substrate 100 (FIG. 4D).

Subsequently, the substrate 100 is etched by masking with the mask layer 300 to form a plurality of through holes 101 and 102 in the substrate 100 to expose the lower portion of the first insulating layer 111. 4e)

Here, if the substrate 100 is a silicon substrate, the first insulating film 111 is a silicon oxide film, and the second insulating film 112 is a silicon nitride film, a reactive ion etching (RIE) technique may be used. The backside of the silicon is etched vertically to where the silicon oxide film is located.

At this time, since the etching rate of the silicon oxide film is 100: 1 or more and the etching rate of the silicon oxide film is low, the silicon oxide film can be sufficiently used as an etching prevention film of the silicon nitride film.

Finally, the mask layer 300 is removed (FIG. 4F).

5A and 5B are a plan view and a cross-sectional view showing a single element region of a gas sensor according to the present invention. First, in FIG. 5A, a sensing electrode 211 and a heater electrode 212 are formed on an insulating layer 110. The sensing film 251 surrounding the sensing electrode 211 and the heater electrode 212 is formed on the insulating film 110.

In this case, as shown in FIG. 5B, a through hole 101 is formed in a region of the substrate 100 positioned below the sensing layer 251, and an insulating layer 110 corresponding to the through hole 101 is formed in a membrane. Becomes

In addition, the inside of the circular dotted line of FIG. 5A is a membrane, and the shape of the membrane is preferably manufactured in a circle in order to uniformly disperse thermal stress to the periphery.

6 is a cross-sectional view showing a state in which a micro pump is mounted to a gas sensor according to another embodiment of the present invention. In the gas sensor according to another embodiment of the present invention, the micro pump may be configured to smoothly supply gas to a sensing film. To install.

The gas sensor includes a substrate 100; An insulating film 110 formed on the substrate 100; A sensing electrode 211 and a heater electrode 212 formed on the insulating layer 110; A sensing film 251 surrounding the sensing electrode 211 and the heater electrode 212 and formed on the insulating film 110; A through hole formed in an area of the substrate 100 corresponding to the sensing layer 251 and exposing a lower portion of the insulating layer 110; First and second grooves 521 and 522, which are bonded to the insulating layer 110 and connected from one side to the other side, are formed on a lower surface thereof and are connected to the gas distribution channel 510. A cover substrate 500 formed on the lower surface and having a sensing film 251 positioned in the first groove 521; It consists of a micro-pump 400 formed on the upper surface of the cover substrate 500 corresponding to the second groove 522.

Here, the through hole 101 preferably has sidewalls perpendicular to the insulating film 110.

The first and second grooves 521 and 522 are more concave than the gas distribution channel 510, and the first and second grooves 521 and 522 are bonded to each other when the substrate 100 and the cover substrate 500 are bonded to each other. ) Is gas circulated only to the gas distribution channel 510.

More specifically, as shown in FIGS. 7 and 8, the lower surface of the cover substrate 500 on which the micro pump 400 is formed is connected to one side of the cover substrate 500 from the other side to a gas distribution channel ( 510; First and second grooves 521 and 522 connected to the gas distribution channel 510 are formed.

In addition, a micro pump 400 is formed on an upper surface of the cover substrate 500 corresponding to the second groove 522.

The micro pump 400 is formed by sequentially stacking the lower electrode 410, the piezoelectric body 420, and the upper electrode 430.

That is, by applying alternating current to the piezoelectric body 420 through the lower and upper electrodes 410 and 430, the micropump 400 performs a pumping process of gas by contracting and expanding the piezoelectric body 420.

In this case, as shown in FIG. 8, the gas distribution channel 510 connected to the second groove 522 and the first groove 521 is in the direction of the first groove 521 in the direction of the second groove 522. Therefore, it is preferable that the channel width is gradually widened.

If the channel groove width is narrow in one side and gradually widened to the other side, gas is sucked into the second groove 521 when the second groove 522 is expanded by the micro pump during the pumping action of the micro pump. The net gas amount can be increased, and the net gas amount discharged to the first groove 521 can be increased when the second groove 522 is contracted by the micropump. As a result, the external gas may be sucked into the sensor located in the first groove 521 and rapidly supplied.

Therefore, the gas sensor of the present invention is provided with a micro piezoelectric pump to increase the supply and discharge speed of the gas, there is an advantage that can improve the gas detection speed.

9A and 9B are schematic cross-sectional views for explaining the micropump operation of the gas sensor according to the present invention. When an alternating current is applied to the piezoelectric body 420 of the micropump 400, the piezoelectric element according to the positive and negative components of the alternating current is shown. 420 repeats contraction and expansion, and the micro pump 400 repeatedly performs a pumping process in which gas is sucked into and discharged from the second groove 522.

That is, as shown in FIG. 9A, due to the contracting action of the piezoelectric body 420, the area of the cover substrate 500 in which the micropump is formed rises to the upper portion so that the external gas passes through the gas distribution channel 510 to form the second groove ( 522.

As shown in FIG. 9B, when the piezoelectric body 420 expands, the area of the cover substrate 500 in which the micropump is formed is lowered so that the gas in the second groove 522 becomes the first groove. To be discharged.

FIG. 10 is a cross-sectional view illustrating a state in which a plurality of sensing films are positioned inside a first groove of a gas sensor according to the present invention, that is, the gas sensor includes a sensing electrode and a heater electrode in the gas sensor structure of FIG. 6. A plurality of single element electrodes 210, 220, and 230 are formed on the insulating film 110; A plurality of sensing films (251, 252, 253) formed on the insulating film (110) surrounding each of the plurality of single device electrodes (210, 220, 230) are formed; The plurality of sensing layers 251, 252, and 253 are positioned inside the first groove 521.

Therefore, a micropump can also be installed in the gas sensor which arrayed the sensing film.

The plurality of single element electrodes 210, 220, and 230 may include sensing electrodes 211, 221, 231 and heater electrodes 212, 222, 232.

As a result, there are a plurality of sensing layers surrounding the sensing electrodes 211, 221, 231 and the heater electrodes 212, 222, 232.

Then, after the process of FIG. 4F is completed, the cover substrate shown in FIG. 7 is bonded to the upper portion of the insulating film of FIG. 4F.

In this case, the plurality of sensing films is positioned inside the first groove of the cover substrate.

As described above, the present invention can form a through hole having sidewalls perpendicular to the membrane, thereby improving the degree of integration of the arrayed gas sensors, thereby having the effect of arranging more gas sensors per unit area.

The present invention is equipped with a micro piezoelectric pump to increase the supply and discharge speed of the gas, there is an effect that can improve the gas detection speed.

Although the invention has been described in detail only with respect to specific examples, it will be apparent to those skilled in the art that various modifications and variations are possible within the spirit of the invention, and such modifications and variations belong to the appended claims.

Claims (13)

delete A substrate; An insulating film formed on the substrate; A sensing electrode and a heater electrode formed on the insulating film; A sensing film surrounding the sensing electrode and the heater electrode and formed on the insulating film; A through hole formed in the substrate region corresponding to the sensing layer and exposing a lower portion of the insulating layer; A gas distribution channel joined to the insulating film and connected from one side to the other side is formed in the lower surface, and first and second grooves connected to the gas distribution channel are formed in the lower surface, and the first groove is formed. A cover substrate having a sensing film positioned therein; The gas sensor consisting of a micro pump formed on the upper surface of the cover substrate corresponding to the second groove. The method of claim 2, The micro pump, Gas sensor, characterized in that the lower electrode, the piezoelectric body and the upper electrode is formed by sequentially stacking. The method of claim 2, The through hole, And a sidewall perpendicular to the insulating film. The method of claim 2, The sensing film, Gas sensor, characterized in that a plurality. The method of claim 2, The gas distribution channel connected to the second groove and the first groove, And a channel width gradually widens from the second groove direction to the first groove direction. The method of claim 2, The substrate is a silicon substrate, And the insulating film is formed by stacking a silicon oxide film and a silicon nitride film. Sequentially forming a first insulating film and a second insulating film on the substrate; Forming a plurality of electrodes for a single element including a sensing electrode and a heater electrode on the substrate; Forming a plurality of sensing layers respectively surrounding the single device electrodes on the second insulating layer; Forming a mask layer having an opening corresponding to each of the plurality of sensing layers under the substrate; Masking the substrate with the mask layer to etch the substrate to form a plurality of through holes in the substrate to expose the lower portion of the first insulating layer; Removing the mask layer; The gas distribution channel, which is joined to and connected from one side to the other side, is formed in the lower surface, and the first and second grooves connected to the gas distribution channel are formed in the lower surface, and correspond to the second groove. Preparing a cover substrate having a micropump formed on an upper surface of the cover substrate; Bonding the cover substrate to an upper portion of the second insulating film so that the plurality of sensing films are positioned inside the first groove of the cover substrate. delete The method of claim 8, The micro pump, A method of manufacturing a gas sensor, characterized in that the lower electrode, the piezoelectric body and the upper electrode are sequentially stacked. The method according to claim 8 or 10, The substrate is a silicon substrate, The first insulating film is a silicon oxide film, And the second insulating film is a silicon nitride film. The method of claim 11, Etching the silicon substrate, And etching the back surface of the silicon substrate vertically to the place where the silicon oxide film is located by using reactive ion etching (RIE). The method according to claim 8 or 10, The gas distribution channel connected to the second groove and the first groove, And the channel width gradually widens from the second groove direction to the first groove direction.

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