JP2619003B2 - Oxygen detecting element and method for manufacturing the same - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial application field) The present invention relates to an oxygen detection element used in fields such as industrial use, medical use and consumer use, and a method for producing the same.

(Prior Art) Oxygen measurement has been widely required in industrial, medical and consumer fields. As an oxygen detecting element for these uses, a zirconia-type oxygen detecting element has been widely used, and a magnetic oxygen detecting element has been slightly used.

As the zirconia-type oxygen detecting element, one having a structure shown in FIG. 17 is known. That is, reference numeral 1 in the drawing denotes a single-seal pipe made of zirconia porcelain inserted into the partition 2. An internal electrode 3 is provided on the inner surface of the pipe 1, and an external electrode 4 is provided on the outer surface. These electrodes 3, 4
Are connected to lead wires 5 and 6, respectively, at the end of the pipe 1. Around the sealed portion side of the pipe 1,
A heater 7 is provided. In the oxygen detecting element having such a configuration, the gas 8 having a reference oxygen partial pressure is filled in the single-sealed pipe 1 and the heater 7 disposed on the single-sealed portion side of the pipe 1.
When the test gas 9 surrounding the test gas 9 is heated, the gas 8 is interposed between the internal electrode 3 and the external electrode 4 of the pipe 1.
An electromotive force proportional to the logarithm of the oxygen partial pressure ratio is generated, and the oxygen concentration of the gas 9 is measured.

As the magnetic oxygen detecting element, one having a structure shown in FIG. 18 is known. That is, reference numeral 11 in the drawing denotes an annular glass tube for forming a flow path, and an introduction portion 12 and a discharge portion 13 for a gas to be reduced containing oxygen are provided in the diameter direction of the glass tube 11. In addition, a horizontal bypass pipe 14 is connected to the annular glass pipe 11 in a direction orthogonal to a straight line connecting the introduction section 12 and the discharge section 13. Two heaters 15a and 15b having a bridge configuration are wound around the bypass pipe 14. A magnet (not shown) for vertically applying a fixed magnetic field 16 is provided in a flow path near the connection between the annular glass tube 11 and one end of a bypass tube 14 around which one heater 15a is wound. . In the figure, 17 is an AC power supply and 18 is an output terminal.
In the oxygen detection element having such a configuration, a test gas containing oxygen is introduced into the annular glass tube 11 from the introduction section 12, one heater 15a is maintained at a constant temperature, and the annular glass tube 11 and one heater are maintained by a magnet (not shown). When a fixed magnetic field 16 is applied vertically to the flow path near the connection with one end of the bypass pipe 14 around which the 15a (bridge side) is wound, oxygen in the gas to be saved is drawn into the magnetic field 16, and the oxygen Since the magnetic susceptibility is rapidly reduced by being heated by the heater 15a, the gas flows from the left to the right of the bypass pipe 14 as shown by the arrow in FIG. For this reason, a temperature difference is generated on the bridge side, and the bridge between the bridge and the other heater 15b to which a constant voltage is applied becomes unbalanced due to a difference in resistance due to the temperature difference.
Produces an output correlated to the oxygen concentration. In this case, the gas flow rate is proportional to the oxygen concentration in the gas, and the temperature difference, that is, the resistance difference, is also proportional to the oxygen concentration.

However, the above-mentioned zirconia-type oxygen detecting element has high accuracy and wide detection oxygen concentration, but has the following disadvantages.

. Since the operating temperature is as high as 650 ° C, the place of use is limited. In addition, the single-piece sealed pipe made of zirconia porcelain, which is the detection unit, is large (about 8 mm in diameter x about 50 mm in length), and the envelope becomes large. In addition, since the power for heating is as large as several tens of watts, the power supply also has a large capacity, and it is practically difficult to drive with a battery.

. It requires a reference gas whose oxygen concentration is always kept constant, which makes the operation cumbersome.

. The output fluctuates due to the presence of a small amount of combustible gas.

Therefore, the zirconia oxygen detection element is the above-mentioned ~
In view of the above, the installation place and application are limited, so that it is mainly used for industrial use, and rarely used for medical use, laboratory use, or consumer use.

On the other hand, although the above-described magnetic oxygen detection element does not have the above-mentioned disadvantages, in order to draw oxygen into a magnetic field by a fixed magnetic field and heat the drawn oxygen by a heater to rapidly reduce the magnetic susceptibility, It is necessary to create a pressure difference before and after the magnetic field. In this case, since the heater 15a is wound around the outer surface of the glass bypass tube 14 having heat insulation as shown in FIG. 18, the heat transfer to the flow path formed by the annular glass tube 11 and the like is reduced. Therefore, a large amount of heat is required to rapidly reduce the magnetic susceptibility. In addition, the heater 15 due to the gas flow generated by the rapid decrease of the magnetic susceptibility
When the temperature difference a is detected, the temperature difference is detected through the bypass pipe 14 having heat insulation properties. Therefore, it is necessary to increase the heating temperature of the heater 15a. Therefore, from the viewpoint of sharply decreasing the magnetic susceptibility and improving the detection sensitivity in the magnetic oxygen detection element, the heater installed near the magnetic field usually needs to be set to about 250 ° C., so that the power consumption is large. As a result, the outer shape of the element body also increases. In the case of the oxygen detecting element having such a structure, the performance remarkably varies depending on the shape of the gas flow path. In the oxygen detection element described above, since the annular glass tube and the bypass tube for forming the gas flow path are manufactured by glasswork, a high-precision annular glass tube or the like cannot be made with good reproducibility, and the performance varies. Problem.

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned conventional problems, and it is possible to obtain sufficient sensitivity even if the heating temperature by the thin film heater is lowered, and to reduce the size. It is an object of the present invention to provide an oxygen detection element capable of performing the above-mentioned method and a method capable of manufacturing such a detection element with high accuracy and high reproducibility.

[Constitution of the Invention] (Means for Solving the Problems) An oxygen detection element of the present invention has an element main body having a flow path for a gas to be conserved and having a heater in the flow path, and a flow path of the main body. An oxygen detecting element comprising a magnet for applying a fixed magnetic field perpendicular to a path, wherein the element body corresponds to the groove by bonding two silicon or glass substrates having a groove on at least one side. A flow path is formed at a location, and a thin film heater is provided between the substrates so as to cross the flow path and to be disposed in a non-contact state with each substrate in the flow path. .

In the manufacturing method of the present invention, a step of forming a shallow concave portion on the surface of one substrate made of silicon or glass, and depositing a metal thin film on the entire surface of the substrate including the concave portion, patterning and forming a thin film heater in the concave portion Forming a groove, selectively etching the substrate to form a groove crossing below the center of the thin film heater, and forming the other silicon or glass substrate on the side where the thin film heater is disposed. A flow path is formed at a position corresponding to the groove by bonding to the surface, and a thin film heater is provided between the substrates in a non-contact state with each substrate in the flow path while traversing the flow path. And forming a device body having the above structure.

Another manufacturing method of the present invention includes a step of forming a thin film heater by depositing a metal thin film on a surface of a substrate made of one of silicon and glass, and forming a thin film heater by selectively etching the substrate. A step of forming a groove that crosses below the center, and bonding another silicon or glass substrate provided with a groove in a position corresponding to the groove of the substrate in advance to the substrate surface on the side where the thin film heater is disposed Thereby, a flow path was formed at a position corresponding to the groove of each of the substrates, and a thin film heater was provided between the substrates in a state of non-contact with each substrate in the flow path while traversing the flow path. And a step of manufacturing an element body having a structure.

(Operation) According to the present invention, two silicon or glass substrates having at least one groove are bonded to form a flow path at a location corresponding to the groove, and a thin film heater is provided between the substrates. An element main body is provided that traverses the flow path and is disposed in a non-contact state with respect to each substrate in the flow path, and a magnet for applying a fixed magnetic field perpendicular to the flow path of the main body is provided. Oxygen in the test gas supplied to the flow path is drawn into the magnetic field by the fixed magnetic field, and the drawn oxygen is heated by the thin-film heater to efficiently and rapidly reduce the magnetic susceptibility, thereby causing a pressure difference between before and after the magnetic field. Can be caused. That is, since the thin film heater crosses the flow path and is disposed in a non-contact state with each substrate in the flow path, the heat transfer efficiency to the test gas in the flow path can be significantly improved. The magnetic susceptibility can be efficiently and rapidly reduced by low-temperature heating (at least 50 ° C.) to generate a pressure difference before and after a magnetic field. When a pressure difference occurs before and after such a magnetic field and a gas flows in the flow path, the thin film heater is disposed in a non-contact state with each substrate in the flow path. Even if is heated at a low temperature, a sufficient temperature difference is generated by the flow of the gas, and oxygen in the gas can be detected with high sensitivity from a change in electric resistance of the heater. Since the power consumption can be reduced by reducing the heating temperature by such a thin film heater, the element body can be made compact, and a mobile oxygen detection element that operates on a dry battery can also be realized.

Further, according to the manufacturing method using the fine processing technique of the present invention, the oxygen detecting element having the above-described excellent action can be obtained with high accuracy and high reproducibility. In other words, the performance of the oxygen detection element having such a structure varies significantly depending on the shape of the gas flow path. However, in the method of the present invention, the element body having the gas flow path and the like can be manufactured with high precision and reproducibility as described above. It is possible to obtain a highly reliable oxygen detection element having no variation in the above.

(Example) Hereinafter, a manufacturing process illustrating an example of the present invention will be described in detail together with a manufacturing process.

Example 1 First, an oxide film was formed by wet oxidation of a silicon substrate 21 and then patterned by a photoetching technique to form an oxide film pattern 22 (FIG. 1A).
Subsequently, as shown in FIG.
Using the mask 22 as a mask, the surface of the substrate 21 was etched with a 35% by weight KOH solution (at a temperature of 70 ° C.) to form a recess 23.

Next, after removing the oxide film pattern 22, a 2.1 μm thick SiO ₂ layer is formed on the entire surface including the concave portion 23 by dry oxidation and CVD.
A film 24 is formed, and a thickness of 4000 mm is further formed by electron beam evaporation.
A Ni film 25 was deposited (illustrated in FIG. 3C). Subsequently, the Ni film 25 and the SiO ₂ film 24 are sequentially patterned by a photo-etching technique, and the base layer 26 and the thin film heater 27 made of SiO ₂ and the terminal portion 28a of the heater 27 are formed on the central concave portion 23 from the substrate 21 side. , 28b, respectively. Subsequently, after depositing a ₂ μm-thick SiO ₂ film on the entire surface by the CVD method, the protective film 29 covering the thin-film heater 27 and the SiO ₂ pattern 30 serving as a mask in the subsequent steps are patterned by photoetching technology. (FIG. 3D).

Next, the concave portion 23 of the exposed silicon substrate 21 was etched with a hydrazine solution using the SiO ₂ pattern 30 as a mask, thereby forming a V-shaped groove 31 and a wide groove 32 crossing under the thin film heater 27 (illustrated in FIG. 3E). . Then, gas introduction hole 33, gas discharge hole 34, wiring takeout hole
The Pyrex glass plate 36 having holes 35a and 35b
There after superimposed on the SiO ₂ pattern 30 of the substrate 21 formed, the substrate 21 and the glass plate 36 was heated at 300 ° C., and anodic bonding by applying a DC voltage of -800V to the glass plate 36 side. (Illustration (f) in the figure). Subsequently, after this joined body was scribed to a size of 12 mm × 19 mm, the wiring terminals 35 a and 35 b of the Pyrex glass plate 36 were filled with a conductive epoxy resin, and the heater terminals connected to the terminal portions 28 a and 28 b were connected. 37a and 37b were formed, and lead wires 38a and 38b were buried and connected to the terminals 37a and 37b. Continued, gas introduction pipe on glass plate 36
39, a gas exhaust pipe 40 was connected by an epoxy resin adhesive 41 so as to match the gas inlet hole 33 and the gas exhaust hole 34 of the glass plate 36, respectively, to produce an element body 42 (FIG. 2
Illustration). FIG. 2 is a plan view of FIG. 1 (g). In the element body 42 manufactured by such a process, a bypass flow path 43 is formed at a position corresponding to the V-shaped groove 31, a flow path 44 is formed at a position corresponding to the groove 32, and the thin film heater is formed.
29 has a structure in which the substrate 21 and the Pyrex glass plate 36 are disposed in a non-contact state in the channel 43 by forming the concave portion 23 in the substrate 21 while traversing the bypass channel 43.

Next, disk-shaped barium ferrite magnets 45a and 45b each having a diameter of 7 mm and a thickness of about 3 mm supported by a yoke (not shown) on the front and back sides of the element body 42 are arranged with a gap of about 1.5 mm, and then shown in the figure. 45% each magnet by polymer adhesive
a and 45b were fixed to the element body 44. In fixing these magnets 45a, 45b, a fixed magnetic field is applied vertically to the flow paths 43, 44 and the magnets 45a, 45b that cover the element body 42 are fixed.
It was arranged so that the arc portion on the tip side was located immediately above the thin film heater 27. Further, the lead wires 38a and 38b are connected to a detection circuit.
The device was connected to a device 46 to produce an oxygen detector (FIGS. 3 and 4). FIG. 4 is a cross-sectional view taken along line XX of FIG.

As shown in FIGS. 3 and 4, the oxygen detecting element of the first embodiment is formed by bonding the silicon substrate 21 having the V-shaped grooves 31 and 32 and the Pyrex glass plate 36 to each other. A bypass flow path 43 is formed at a location corresponding to the groove 31, a flow path 44 is formed at a location corresponding to the groove 32, and the thin film heater 29 traverses the bypass flow path 43 and a concave portion to the substrate 21 is formed.
By forming the element 23, the element body 42 having a structure disposed in a non-contact state with the substrate 21 and the Pyrex glass plate 36 in the channel 43, and a fixed magnetic field perpendicular to the channels 43, 44 of the element body 42 Disc-shaped barium ferrite magnets for applying force
45a, 45b, and a terminal 28 on the thin film heater 27 of the element body 42.
a, 28b, heater terminals 37a, 3 made of conductive epoxy resin
7b and the detection circuit 46 connected through the lead wires 38a and 38b.
It has a structure with The thin film heater 27
The upper and lower surfaces are covered with a base layer 26 made of SiO ₂ and a protective film 28. The operation of the oxygen detecting element having such a configuration is described below.
This will be described below with reference to FIGS. 5 and 6.

First, when a test gas containing no oxygen is introduced from the gas introduction pipe 39 into the flow path 44 through the gas introduction hole 33, the flow path 44 is formed symmetrically. As shown by arrows, the gas is discharged from the gas discharge pipe 44 through the upper and lower flow paths 44 and the gas discharge holes 34. At this time, the pressure difference between both ends of the central bypass channel 43 becomes zero, and no gas flow occurs.

On the other hand, when a test gas containing no oxygen is introduced from the gas introduction pipe 39 into the flow path 44 through the gas introduction hole 33 with a fixed magnetic field applied to the flow path 44 of the element body 42 from the two magnets 45a and 45b. The oxygen in the test gas introduced into the flow path 44
As shown by an arrow in the figure, the magnetic field is drawn into the magnetic field by the fixed magnetic field, and the pressure of the flow path 44 below the element body 42 to which the magnetic field is applied increases. In this state, the thin film heater 27 arranged near the center of the bypass passage 43 is connected to the lead wire 38 by the detection circuit 46.
When heated to a constant temperature through the a, 38b, the lead terminals 37a, 37b, and the terminal portions 28a, 28b, the magnetic susceptibility of the oxygen drawn into the magnetic field is rapidly reduced by the heating by the thin film heater 27, and the magnetic field is applied. A pressure difference is generated between the flow path 44 and the bypass flow path 43 in which the thin film heater 27 is disposed, and a gas having a flow rate corresponding to the oxygen concentration in the gas flows as shown by a dotted arrow in FIG. Flow occurs in the bypass channel 43. At this time,
Since the thin film heater 27 crosses the bypass channel 43 and is disposed in a non-contact state with the silicon substrate 21 and the Pyrex glass 36 in the channel 43, the bypass channel 43
The heat transfer efficiency with respect to the gas to be detected in the inside is remarkably improved, and the flow of gas can be generated in the bypass passage 43 by the constant temperature heating (50 ° C. or more) by the thin film heater 27. When the gas flows in the bypass channel 43 in this manner, a temperature difference is generated in the thin film heater 27 disposed in the channel 43, and a change in the electric resistance of the heater 27 is detected by the detection circuit 46.
, Oxygen in the test gas is detected. In this case, since the thin-film heater 27 is disposed directly in the bypass passage 43 and is air-insulated in a non-contact state with respect to the silicon substrate 21 and the Pyrex glass 36, the thin-film heater 27 is heated at a low temperature. However, a sufficient temperature difference is generated by the flow of the gas, and a change in the electric resistance of the heater 27 can be detected well by the detection circuit 46, so that oxygen in the test gas can be detected with high sensitivity. Since the power consumption can be reduced by reducing the heating temperature by such a thin film heater, the element body can be made compact,
In addition, a mobile oxygen detection element that operates on a dry battery can be realized.

In fact, test gases having different oxygen concentrations are introduced into the flow path 44 of the element main body 42 by the oxygen detection element of the first embodiment, and from the disc-shaped barium ferrite magnets 45a and 45b to the flow path 44 of the element main body 42. Apply a fixed magnetic field of magnetic flux density 2500G,
When the output voltage (ΔVout) from the detection circuit 46 when the heating temperature of 7 was set to 50 ° C., 100 ° C., and 200 ° C. was measured, the characteristic diagram shown in FIG. 7 was obtained. Note that A in FIG. 7 is a characteristic line when the heating temperature of the thin film heater 27 is set to 50 ° C.
B is the same characteristic line when the heating temperature is set to 100 ° C., and C is the same characteristic line when the heating temperature is set to 200 ° C. From FIG. 7, it can be seen that the oxygen detecting element of Example 1 can detect oxygen in the test gas with high sensitivity even when the temperature of the thin film heater 27 is sufficiently low.

Therefore, according to the present invention, even if the heating temperature of the thin-film heater 27 is reduced, oxygen in the test gas can be detected with high sensitivity, so that power consumption during driving is reduced and the element body 42 is made compact. In addition, a mobile oxygen detector that operates on a dry battery can be realized.

Further, according to the manufacturing method of the first embodiment, since the element main body 42 is manufactured by a fine processing technique such as etching, the oxygen detecting element having the above-described excellent action can be obtained with high accuracy and high reproducibility. In other words, the performance of the oxygen detection element having such a structure varies significantly depending on the shape of the gas flow path. However, in the method of the present invention, as described above, the thin film heater 27, the flow path 44, the bypass flow path 43, etc. Since the element body 42 having the above can be manufactured with high accuracy and high reproducibility,
It is possible to obtain a highly reliable oxygen detection element having no variation in performance.

Example 2 First, a 2.1 μm thick SiO ₂ film 24 was formed on the entire surface of a silicon substrate 21 by dry oxidation and CVD, and a 4000 nm thick Ni film 25 was further deposited by electron beam evaporation (FIG. 8 ( a) illustrated). Subsequently, as shown in FIG. 2B, the Ni film 25 and the SiO ₂ film are sequentially patterned by a photo-etching technique, and a base layer 26 made of SiO _{2, a} thin-film heater 27 and terminals of the heater 27 are formed from the substrate 21 side. The portions 28a and 28b were respectively formed.

Next, after depositing a ₂ μm-thick SiO ₂ film on the entire surface by the CVD method, the protective film 29 covering the thin-film heater 27 and the SiO ₂ pattern 30 serving as a mask in the subsequent steps are patterned by photo-etching technology. Formed. Then,
Exposed silicon substrate 21 using SiO ₂ pattern 30 as a mask
Was etched with a hydrazine solution to form a V-shaped groove 31 and a wide groove 32 crossing under the thin film heater 27 (illustrated in FIG. 3C).

Next, a V-shaped groove 47, a groove 48 and a gas introduction hole are formed on the Pyrex glass plate 36 at locations corresponding to the V-shaped grooves 31 and 32 on the substrate 21 by photo-etching technology and electrolytic discharge machining.
33, a gas exhaust hole 34, and wiring extraction holes 35a and 35b were opened.
Subsequently, after stacking this Pyrex glass plate 36 on the SiO ₂ pattern 30 of the substrate 21 in which the groove 32 was formed,
21 and the glass plate 36 are heated at 300 ° C., and −8
A direct current voltage of 00 V was applied to perform anodic bonding (illustration (d) in the same figure). Subsequently, after this joined body was scribed to a size of 12 mm × 19 mm, the wiring terminals 35 a and 35 b of the Pyrex glass plate 36 were filled with a conductive epoxy resin, and the heater terminals 37 a connected to the terminal portions 28 a and 28 b were connected. , 37b, and lead wires 38a, 38b were buried and connected to the terminals 37a, 37b. Further, a gas inlet pipe 39 and a gas outlet pipe 40 are connected on the glass plate 36 with an epoxy resin adhesive 41 so as to match the gas inlet holes 33 and the gas outlet holes 34 of the glass plate 36, respectively, thereby connecting the element body 42. It was produced (FIG. (E)). In the element body 42 manufactured by this process, a bypass channel 43 ′ is provided at a location corresponding to the V-shaped grooves 31, 47 of the substrate 21 and the Pyrex glass plate 36, and a channel is provided at a location corresponding to the grooves 32, 48. 44 'is formed, and the thin film heater 27 is
It has a structure that traverses 3 ′ and is disposed in a non-contact state with the substrate 21 and the Pyrex glass plate 36 in the channel 43 ′.

Next, disk-shaped barium ferrite magnets 45a and 45b each having a diameter of 7 mm and a thickness of about 3 mm supported by a yoke (not shown) on the front and back sides of the element body 42 are arranged with a gap of about 1.5 mm, and then shown in the figure. 45% each magnet by polymer adhesive
a and 45b were fixed to the element body 44. In fixing these magnets 45a, 45b, a fixed magnetic field is applied vertically to the flow paths 43, 44 and the magnets 45a, 45b that cover the element body 42 are fixed.
It was arranged so that the arc portion on the tip side was located immediately above the thin film heater 27. Further, the lead wires 38a and 38b are connected to a detection circuit.
The device was connected to an oxygen detector (see FIGS. 9 and 10). FIG. 10 is a sectional view taken along line XX of FIG.

According to the oxygen detecting element of the second embodiment shown in FIGS. 9 and 10, even if the heating temperature of the thin film heater 27 is reduced similarly to the oxygen detecting element of the first embodiment, Since oxygen can be detected with high sensitivity, power consumption during driving can be reduced and the element body 42 can be made compact, and a mobile oxygen detection element that operates on dry batteries can also be realized. Further, according to the manufacturing method of the second embodiment, it is possible to obtain a highly reliable oxygen detection element having no variation in performance.

Example 3 First, a 2.1 μm thick SiO ₂ film 24 was formed on the entire surface of a silicon substrate 21 by dry oxidation and CVD, and a 4000 nm thick Ni film 25 was deposited by electron beam evaporation (FIG. 11 ( a) illustrated). Subsequently, as shown in FIG. 2B, the Ni film 25 and the SiO film 24 are sequentially patterned by a photoetching technique, and a base layer 26 made of SiO ₂ and a thin film heater 27 and terminals of the heater 27 are formed from the substrate 21 side. The portions 28a and 28b were respectively formed.

Next, after depositing a ₂ μm-thick SiO ₂ film on the entire surface by the CVD method, the protective film 29 covering the thin-film heater 27 and the SiO ₂ pattern 30 serving as a mask in the subsequent steps are patterned by photo-etching technology. Formed. Then,
Exposed silicon substrate 21 using SiO ₂ pattern 30 as a mask
Was etched with a hydrazine solution to form a V-shaped groove 31 and a wide groove 32 crossing under the thin film heater 27 (illustrated in FIG. 3C).

Next, the Pyrex glass plate 36 is subjected to photoetching technology and electrolytic discharge machining to form a groove 49 in a small area at a position corresponding to the thin film heater and the terminal portions 28a and 28b of the substrate 21, and a groove at a position corresponding to the groove 32 of the substrate 21. 48 and gas inlet 3
3. The gas discharge hole 34 and the wiring extraction holes 35a and 35b were opened.
Subsequently, after stacking this Pyrex glass plate 36 on the SiO ₂ pattern 30 of the substrate 21 in which the groove 32 was formed,
21 and the glass plate 36 are heated at 300 ° C., and −8
A direct current voltage of 00 V was applied to perform anodic bonding (illustration (d) in the same figure). Subsequently, after this joined body was scribed to a size of 12 mm × 19 mm, the wiring terminals 35 a and 35 b of the Pyrex glass plate 36 were filled with a conductive epoxy resin, and the heater terminals 37 a connected to the terminal portions 28 a and 28 b were connected. , 37b, and lead wires 38a, 38b were buried and connected to the terminals 37a, 37b. Further, a gas inlet pipe 39 and a gas outlet pipe 40 are connected on the glass plate 36 with an epoxy resin adhesive 41 so as to match the gas inlet holes 33 and the gas outlet holes 34 of the glass plate 36, respectively, thereby connecting the element body 42. It was produced (FIG. (E)). In the element body 42 manufactured by such a process, a bypass flow path 43 is provided at a location corresponding to the V-shaped groove 31 of the substrate 21, and a flow path is provided at a location corresponding to the grooves 32 and 48 of the substrate 21 and the Pyrex glass plate 36. 44 ′
Is formed, and the thin film heater 27 is connected to the bypass passage.
It has a structure that traverses 43 'and is disposed in a non-contact state with the substrate 21 and the Pyrex glass plate 36 in the flow path 43'.

Next, disk-shaped barium ferrite magnets 45a and 45b each having a diameter of 7 mm and a thickness of about 3 mm supported by a yoke (not shown) on the front and back sides of the element body 42 are arranged with a gap of about 1.5 mm, and then shown in the figure. 45% each magnet by polymer adhesive
a and 45b were fixed to the element body 44. In fixing these magnets 45a, 45b, a fixed magnetic field is applied vertically to the flow paths 43, 44 and the magnets 45a, 45b that cover the element body 42 are fixed.
It was arranged so that the arc portion on the tip side was located immediately above the thin film heater 27. Further, the lead wires 38a and 38b are connected to a detection circuit.
The device was connected to 46 to produce an oxygen detector (FIGS. 12 and 13). FIG. 13 is a sectional view taken along the line XX of FIG.

According to the oxygen detecting element of the third embodiment shown in FIGS. 12 and 13, even if the heating temperature of the thin-film heater 27 is reduced similarly to the oxygen detecting element of the first embodiment, Since the detection can be performed with high sensitivity, the power consumption during driving can be reduced and the element body 42 can be made compact, and a mobile oxygen detection element that operates on a dry battery can also be realized.
Further, according to the manufacturing method of the third embodiment, it is possible to obtain a highly reliable oxygen detection element having no variation in performance.

The oxygen detecting element of the present invention is not limited to the structure shown in the first to third embodiments, and may have a structure shown in FIGS. 14 to 16.

That is, FIG. 14 is a plan view showing the element body 42,
44 is a rhombus, and a bypass flow path 43 is formed on a diagonal line of the flow path 44 orthogonal to a straight line connecting the gas introduction pipe 39 and the gas discharge pipe 40.
Is provided. Note that reference numeral 50 in the drawing denotes a fixed magnetic field applied perpendicularly to the flow path 44 from the magnet. Also in the oxygen detection element including the element body 42 having such a structure,
It has the same excellent performance as in Examples 1 to 3.

FIG. 15 shows the element body 12 in which the thin film heater 27 is arranged in one flow path 51. The oxygen detecting element provided with the element main body 42 having such a configuration can exhibit the same performance as the first to third embodiments when no external gas flows.

FIG. 16 shows an element body 42 in which a thin-film heater 27 is arranged in a bypass channel 43 and a thin-film resistor 52 having the same shape as the heater 27 is arranged on the upstream side of the flow of gas from the heater 27. It is. Incidentally, 53a and 53b in the figure are the thin film resistors.
52 terminals. According to the oxygen detection element including the element body having such a configuration, even if the temperature of the test gas guided to the bypass passage 43 changes due to the influence of the ambient temperature, the thin-film heater 27
A thin-film resistor 52 having the same shape as the heater 27 disposed on the upstream side of
By measuring the temperature and compensating the temperature, the amount of oxygen in the test gas can be accurately detected. In fact, when the temperature of the thin-film heater 27 was set to 50 ° C. by such an oxygen detecting element, it was possible to stably detect the oxygen in the test gas at an ambient temperature of −10 ° C. to + 30 ° C.

In the above embodiment, a barium ferrite magnet is used as the magnet for applying a fixed magnetic field perpendicular to the flow path, but another permanent magnet or electromagnet may be used.

In the above embodiment, a silicon substrate and a Pyrex glass plate are used as the substrate of the element body, but the element body may be constituted by a combination of two silicon substrates or a combination of two glass substrates. Further, the glass substrate is not limited to Pyrex glass, and another glass substrate such as Vycor glass may be used.

[Effects of the Invention] As described in detail above, according to the present invention, sufficient sensitivity can be obtained even when the heating temperature of the thin-film heater is lowered, and compactness can be achieved. Oxygen detecting element that can be applied to oxygen measurement in various fields such as
In addition, it is possible to provide a method capable of manufacturing such an oxygen detecting element with high accuracy and reproducibility.

[Brief description of the drawings]

1 (a) to 1 (g) are cross-sectional views showing steps of manufacturing an element main body in Example 1 of the present invention, FIG. 2 is a plan view of FIG. 1 (g), and FIG. FIG. 4 is a cross-sectional view taken along line XX of FIG. 3, and FIGS. 5 and 6 are plan views for explaining the operation of the first embodiment. FIG. 7 shows the oxygen concentration in the gas and the detection circuit when the set temperature of the thin film heater is 50 ° C., 100 ° C., and 200 ° C. when the oxygen of the test gas is measured using the oxygen detecting element of the first embodiment. 8 (a) to 8 (e) are cross-sectional views showing steps of manufacturing an element body according to Embodiment 2 of the present invention, and FIG. FIG. 10 is a plan view showing the oxygen detecting element shown in FIG.
11 (a) to 11 (e) are cross-sectional views showing steps of manufacturing an element body according to the third embodiment of the present invention, and FIG. 12 is a cross-sectional view of the oxygen detecting element manufactured in the third embodiment. Plan view,
FIG. 13 is a sectional view taken along line XX of FIG. 12, and FIGS.
The figure is a plan view of an element body showing another embodiment of the present invention,
FIG. 17 is a sectional view showing a conventional oxygen detecting element, and FIG. 18 is a schematic view showing another conventional oxygen detecting element. 21 silicon substrate, 27 thin film heater, 31, 47 V
Mold groove, 32, 48… Groove, 36… Pyrex glass plate, 39
…… Gas inlet pipe, 40 …… Gas exhaust pipe, 42 …… Element body,
43, 43 '... bypass flow path, 44, 44' ... flow path, 45a, 4
5b Barium ferrite magnet, 46 Detection circuit, 52
... Thin film resistors.

Claims (3)

(57) [Claims] An oxygen device comprising: an element main body having a flow path of a test gas and a heater provided in the flow path; and a magnet for applying a fixed magnetic field perpendicular to the flow path of the main body. In the detection element, the element body is formed by laminating two silicon or glass substrates having a groove on at least one side to form a flow path at a position corresponding to the groove, and forming a thin film heater between the substrates. An oxygen detection element having a structure traversing a flow path and disposed in a non-contact state with each substrate in the flow path. 2. A step of forming a shallow concave portion on the surface of one of the silicon or glass substrates, and depositing a metal thin film on the entire surface of the substrate including the concave portion, followed by patterning to form a thin film heater in the concave portion. And a step of selectively etching the substrate to form a groove crossing below the center of the thin film heater, and placing the other silicon or glass substrate on the substrate surface on the side where the thin film heater is disposed. A structure in which a flow path is formed at a position corresponding to the groove by laminating, and a thin film heater is arranged between the substrates in such a manner that the thin film heater crosses the flow path and is not in contact with each substrate in the flow path. Producing the element main body of the above. 3. A step of forming a thin film heater by depositing a metal thin film on the surface of one of silicon or glass substrates and patterning the thin film heater, and selectively etching the substrate to form a lower portion near the center of the thin film heater. Forming a crossing groove, and bonding the other silicon or glass substrate having a groove in a location corresponding to the groove of the substrate in advance to the substrate surface on the side where the thin film heater is disposed. An element body having a structure in which a flow path is formed at a position corresponding to a groove of a substrate, and a thin film heater is interposed between the substrates and disposed in a non-contact state with each substrate in the flow path. A method of manufacturing an oxygen detection element.