JP2607631B2 - Electrochemical sensor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrochemical sensor, and more particularly to a detector and a biosensor that detect gas or vapor such as carbon monoxide and alcohol using an electrolytic reaction. The present invention relates to an electrochemical sensor used as a sensor.

[Conventional technology]

Electrochemical sensors for detecting various gas components, for example, hydrogen, oxygen, carbon monoxide, etc., are known and described in detail in various publications. An electrochemical gas sensor generally has a sensing electrode called a working electrode, a counter electrode, and a reference electrode, which are provided in an electrolyte. The components are oxidized or reduced, and the presence and concentration of gas components are detected by a current flowing between the working electrode and the counter electrode at this time.

Such an electrochemical sensor has the advantage of high sensitivity and low power consumption. However, conventional electrochemical sensors use a liquid acid electrolyte, and each electrode has a structure in contact with the gas to be detected through a gas permeable membrane. There was a problem. For this reason, it has been difficult to reduce the size of the detection unit, the sensitivity or output has been reduced over time, and there has been a serious problem that the life is short.

As a method of solving the above-mentioned difficulties, U.S. Pat.
Nos. 4,227,984 and 4,265,714 propose an electrochemical sensor using a solid polymer electrolyte. In this structure, a working electrode and a reference electrode are arranged on one side of a solid polymer electrolyte membrane, and a counter electrode is arranged on the opposite side of the electrolyte membrane so as to face the working electrode.

However, in the above prior art, it is necessary to adhere the electrode on a flexible film having a solid electrolyte, and the electrode is separated due to a volume change due to swelling of the gas-permeable solid polymer electrolyte, thereby lowering sensitivity and output. There was a problem.

In order to solve the above problems, a planar-type electrochemical sensor has been proposed. FIG. 5 shows an example of the structure of a planar sensor, in which a working electrode 2, a counter electrode 3 and a reference electrode 4 are formed on one surface of a strong insulating substrate 1 made of ceramic, glass or the like by means of vapor deposition, sputtering or the like. And a gas permeable solid electrolyte 5 applied thereon.
In order to hold the solid electrolyte 5 on the insulating substrate 1, a weir-like frame 1 a is provided on the surface of the insulating substrate 1 so as to surround the electrodes 2.

The inventors have also studied on such a planar type electrochemical sensor, and have filed a patent application in Japanese Patent Application No. 63-42848 (Japanese Patent Application Laid-Open No. 1-216256).

As a method for forming the frame 1a in the conventional planar sensor as described above, after forming the electrodes 2 on the insulating substrate 1, the insulating polymer material is formed so as to surround the electrodes 2 on the insulating substrate 1. Alternatively, the frame 1a is formed by applying or attaching an inorganic material or the like.

6 to 8 show a specific method of forming the frame 1a. First, the method shown in FIG. 6 is a method of forming the frame 1a formed in a predetermined frame shape separately from the substrate 1. [Step (a)], and the frame 1a is attached to the insulating substrate 1 [Step (b)].

In the method shown in FIG. 7, a portion of the surface of the substrate 1 other than the portion where the frame 1a is formed is covered with a mask 6 [step (a)], and a frame material 1a 'is applied to the entire substrate 1 from above [step (a). b)) Then, if the mask 6 is removed together with the covering frame material 1a 'thereon, only a predetermined portion of the frame material remains on the substrate 1 to form the frame 1a [step (step (b)). c)].

In the method shown in FIG. 8, a frame material 1a ″ made of an inorganic material or the like is deposited on the entire surface of the substrate 1 at a predetermined height [step (a)], and the top thereof is covered with a mask 6 [step (b)]. Then, a portion other than the portion where the frame 1a is formed is patterned and removed [step (c)]. Using the patterned mask 6, the frame material 1a ″ is dug by etching means or the like [step (d)]. After that, if the mask 6 is removed, the frame 1a is formed.

[Problems to be solved by the invention]

However, in the above-mentioned planar type sensor,
To reduce the size of the sensor, the element size must be
When it is necessary to make the size extremely small, such as × 1 mm or less, the position, shape, pattern, etc. of the frame must also be formed with very high precision.

However, frames manufactured by the above-described conventional method are generally inferior in accuracy, and in order to achieve high accuracy, cost is high, and there is a disadvantage that manufacturing efficiency is reduced,
In practice, it is impossible to achieve a certain degree of higher accuracy, which has been a factor that hinders miniaturization or higher accuracy of the entire sensor.

For example, as shown in FIG. 6, in the method of attaching the frame 1a made of a separate member to the substrate 1, the deformation of the frame 1a occurs, the alignment accuracy between the frame 1a and the substrate 1 is poor, the sensor element 1 It takes time and effort to attach the frame 1a to the substrate 1 for each piece, and has disadvantages such as high production cost and poor production efficiency.

As shown in FIG. 7, the method of applying the frame material 1a 'in accordance with the pattern of the mask 6 also does not provide very good positioning accuracy between the frame 1a and the substrate.

As shown in FIG. 8, in the method of excavating the frame material 1a ″ deposited on the substrate 1 in accordance with the pattern of the mask 6, the frame material 1a having a height of several tens μm or more required for a normal frame 1a is used. Is difficult to form by deposition, and the deposition process is very time consuming and costly.

Also, in each of the methods, since the frame 1a has a structure different from that of the substrate 1, there is a disadvantage that the integration between the frame 1a and the substrate 1 is inferior, and the material cost is higher by the amount of the frame material.

Accordingly, an object of the present invention is to provide, in the above-described planar type electrochemical sensor, a frame having a structure that is excellent in integration with an insulating substrate and has high accuracy, and that can form such a frame efficiently and at low cost. Is to provide.

[Means for solving the problem]

According to a first aspect of the present invention to solve the above-mentioned problems, in the above-mentioned planar type electrochemical sensor, the frame and the insulating substrate are integrally formed of the same member.

According to a second aspect of the present invention, in carrying out the first aspect of the present invention, the frame is integrally formed by digging an insulating substrate.

[Action]

According to the first aspect of the present invention, since the frame is formed integrally with the insulating substrate, the integration with the insulating substrate is improved, and the displacement between the substrate and the frame is unlikely to occur. Further, the step of depositing the frame material and the like can be omitted, and there is no need to prepare a frame material separately from the insulating substrate.

According to the second aspect of the present invention, since the frame is formed by digging the insulating substrate, a high-precision and low-cost frame can be formed using a normal photolithography technique or the like.

〔Example〕

Next, the present invention will be described in detail below with reference to the drawings showing embodiments.

FIG. 1 shows a structural example of an electrochemical sensor according to the present invention. A working electrode 20 and a counter electrode 3 made of an electrode material such as gold and platinum are placed on an insulating substrate 10 made of silicon or the like.
0 and the reference electrode 40 are formed, and the frame 11 is formed in a square frame shape so as to surround most of the surface of the insulating substrate 10 except for one end of each electrode 20.
11 and the insulating substrate 10 are integrally formed of the same material. The electrodes 20 are formed continuously from the inside of the frame 11 to the insulating substrate 10 outside the frame 11 along the peripheral wall of the frame 11, and portions 21, 31 of the electrodes 20 in the frame 11 are formed. ,
41 constitutes a reaction part which is a place for an electrochemical reaction with a component to be detected.Parts 22, 32, and 42 outside the frame 11 receive an electric signal from an external circuit or receive an electric signal to the external circuit. It becomes a terminal part for taking out. The inside of the frame 11 is coated or filled with a gas-permeable solid electrolyte 50 such as a polymer solid electrolyte.

The shape and structure of these electrodes 20,..., The material of the electrolyte 50, or the shapes of the insulating substrate 10 and the frame 11 can be basically the same as those of a normal planar sensor.

FIG. 2 shows the manufacturing steps of the above-described sensor, in particular, focusing on the method of forming the frame 11, in the order of the steps.

First, a silicon dioxide layer 60 for etching is deposited to a thickness of 1 μm on the (110) plane of the silicon substrate 13 by a thermal oxidation method. [Step (a)].

A resist 61 is applied thereon (step (b)), and is exposed and developed in a pattern corresponding to the shape of the frame 11 to form a resist 61 having a predetermined pattern [step (c)].

Using the pattern of the resist 61 as a mask, the silicon dioxide film 60 is patterned, and the silicon dioxide film 60 other than where the frame 11 is formed is removed. At this time, the pattern of the silicon dioxide film 60 is
1) Or it is arranged so as to be parallel to the intersection line between (1) and (110) [Step (d)].

After removing the resist 61 [step (e)], KOH 45 wt%,
The silicon substrate 13 is dug using an etching solution of 55 wt% of H ₂ O and a liquid temperature of 85 ° C. to form the frame 11 [step (f)]. At this time, the silicon dioxide film as described above
If the pattern is formed in 60 patterns, the anisotropy of the etching rate depending on the plane orientation of the silicon substrate 13 makes it possible to dig vertically into the surface of the silicon substrate 13 and accurately form the shape of the frame 11. The digging of the silicon substrate 13 is completed in an etching time of 30 minutes.

If the remaining silicon dioxide film 60 is removed (step (g)), the frame 11 is formed integrally with the silicon substrate 13. In the following steps, the steps of insulating the silicon substrate 13 and manufacturing the electrodes 20. Will be described.

A silicon dioxide layer 12 serving as an insulating layer is deposited to a thickness of 2 μm on the entire surface of the silicon substrate 13 including the frame 11 by the same thermal oxidation method as described above, thereby manufacturing an insulating substrate 10 (step (h)). ].

On the silicon dioxide layer 12, each electrode 20 consisting of a platinum film was formed to a thickness of 1 μm using a mask sputtering method.
[Step (i)].

Thus, the silicon substrate 13 and the silicon dioxide layer
A frame 11 is integrally formed on an insulating substrate 10 made of 12,
The electrochemical sensor according to the present invention in which the electrodes 20 are formed thereon is completed. The inside of the frame 11 is filled with an appropriate electrolyte 50 and held by ordinary means.

Next, FIG. 3 shows another embodiment, and FIG. 4 shows the manufacturing method in the order of steps. In addition, the same reference numerals are given to the same structural parts as those in the above-described embodiment, and the overlapping description will be omitted.

In this embodiment, the electrodes 20 are not formed so as to extend to the outside of the frame 11, and the whole of the electrodes 20 is accommodated inside the frame 11. Although the structures of the reaction portions 21 and the terminal portions 22 of the electrodes 20 are not shown in detail, the structure is the same as that of a normal sensor.

As shown in FIG. 4, a mask 62 such as a polymer mask material is deposited on the surface of the insulating substrate 10 (step (a)), and after the mask 62 is formed in a predetermined mask pattern [step (c)] , The insulating substrate 10
The frame 11 is formed by digging [Step (c)], and the remaining mask 62 is removed [Step (d)] to manufacture a sensor as shown in FIG. As in the previous embodiment, the silicon substrate 13 and the silicon dioxide layer
Without forming the insulating substrate 10 consisting of 12, the entire insulating substrate 10
If it is made of an insulating material such as a glass substrate or a ceramic substrate, the manufacturing method as in this embodiment can be applied.

As described above, the method of integrally forming the insulating substrate 10 and the frame 11 with the same member is a method in which the surface of the insulating substrate 10 is dug by etching using the photolithography method, which can be manufactured with high precision and efficiency. However, for the specific etching solution and process,
Depending on the material of the frame 10, the structure of the frame 11, and the like, the etching is carried out under various ordinary etching methods and appropriate processing conditions.
The method of digging the insulating substrate 10 may employ not only a chemical digging method such as etching, but also a physical means for mechanically shaving the surface of the insulating substrate 10. When the insulating substrate 10 is formed of a ceramic material or the like, the frame 11 can be formed integrally.

In the electrochemical sensor according to the present invention, the materials and structures of the electrodes 20... And the electrolyte layer 50 other than the structure of the frame 11 described above are implemented by freely combining the structure and the like of a normal planar electrochemical sensor. It is possible to

〔The invention's effect〕

According to the first aspect of the present invention, since the frame and the insulating substrate are integrally formed by the same member, the integration between the frame and the insulating substrate is high, and Since the insulating substrate is not a separate member, the alignment between the frame and the insulating substrate is extremely accurate, and various properties such as electrical insulation are uniform and excellent.

Since a part of the insulating substrate is used as a frame without applying or depositing another frame material on the insulating substrate, the material cost is reduced and the application and deposition steps of the frame material are not required. The process can be simplified, the production efficiency can be improved, and the overall production cost can be reduced.

According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, since the frame is formed by digging the insulating substrate, a high-precision processing method such as a photolithography technique is applied. As a result, the shape, formation position, and pattern of the frame are improved in accuracy, and for example, a highly accurate frame with an error of ± 10 μm or less can be provided. Also, since the frame can be processed simultaneously for many sensor elements,
Suitable for mass production.

[Brief description of the drawings]

1 is a perspective view of an embodiment according to the present invention, FIG. 2 is a sectional view showing a manufacturing method in the order of steps, FIG. 3 is a perspective view of another embodiment, and FIG. 5 and 5 are perspective views of a conventional example, and FIGS. 6 to 8 are cross-sectional views showing different manufacturing methods in the order of steps. 10 ... insulating substrate, 11 ... frame, 20 ... working electrode, 30 ...
… Counter electrode, 40 …… Reference electrode, 50 …… Electrolyte layer

Claims (2)

(57) [Claims] A working electrode, a counter electrode and a reference electrode are provided on the same surface of an insulating substrate, and a space between each of the electrodes is covered with a gas-permeable solid electrolyte layer. An electrochemical sensor held in a frame projecting from the surface, wherein the frame and the insulating substrate are integrally formed of the same member. 2. The electrochemical sensor according to claim 1, wherein the frame is formed integrally by digging an insulating substrate.