JPH02196956A - Electrochemical type sensor and production thereof - Google Patents

Abstract

PURPOSE:To improve the strength of the rugged parts of the sensor by forming the root parts of the rugged parts of an insulating substrate to an arc shape with which stress concentration hardly arises. CONSTITUTION:Projecting parts 11 constituting many slender plate shapes are arrayed and provided in two rows on the surface of the insulating substrate 10 formed by coating the surface of a conductive substrate 13 consisting of silicon, etc., of the sensor with an insulating layer 14 consisting of silicon dioxide, etc. A working electrode 20 and a counter electrode 30 are formed on the respective projecting part arrays. A reference electrode 40 is formed to the flat part between the working electrode 20 and the counter electrode 30. The electrodes of the working electrode 20..., etc., are formed of electrode materials, such as platinum and gold. The surface of the insulating substrate 10 is coated with the electrolyte layer 50 consisting of a high- polymer solid electrolyte, etc. and the projecting parts 11 are partly exposed to the upper part of the electrolyte layer 50. The respective electrodes 20... are partly extended to the outside of the electrolyte layer 50 to constitute terminal parts 22, 32, 42 for connection to external circuits. The stress concentration in the root parts of the rugged parts of the insulating substrate 10 is decreased in this way and the strength of the rugged pats is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrochemical sensor and a method for manufacturing the same, and more particularly, to a sensor that uses electrolytic reactions to detect gases and vapors such as carbon oxide and alcohol. The present invention relates to an electrochemical sensor used as a device, a biosensor, etc., and a method for manufacturing such an electrochemical sensor.

[Conventional technology]

Electrochemical sensors for detecting various gas components, such as hydrogen, oxygen, carbon oxides, etc., are known and are described in detail in various publications. Electrochemical gas sensors generally have three electrodes in an electrolyte: a sensing electrode called a working electrode, a counter electrode, and a reference electrode.The gas component to be sensed is brought into contact with the working electrode, and the gas component is detected by the exchange of electrons. The gas component is oxidized or reduced, and the presence and concentration of the gas component is detected by the current flowing between the working electrode and the counter electrode.

Such electrochemical sensors have the advantages of high sensitivity and low power consumption. However, conventional electrochemical sensors use a liquid acid electrolyte and have a structure in which each electrode is in contact with the gas to be detected through a gas permeable membrane, so there are problems such as changes in the liquid electrolyte over time, leakage, and material corrosion. There was a problem. Therefore, there have been serious problems in that it is difficult to miniaturize the detection section, the sensitivity or output decreases over time, and the lifespan is short.

As a method to solve the above-mentioned difficulties, U.S. Patent No. 4
．． No. 22-7.984, No. 4,265.714
The patent proposes an electrochemical sensor using a solid polymer electrolyte. In its structure, a working electrode and a reference electrode are arranged on one side of a solid electrolyte membrane, and a counter electrode is arranged on the opposite side of the electrolyte membrane, facing the working electrode.

However, in the above-mentioned prior art, it is necessary to adhere the electrode onto a flexible film containing a solid electrolyte, and the volume change due to swelling of the gas-permeable solid polymer electrolyte causes the electrode to peel off, resulting in a decrease in sensitivity and output. There was a problem.

In order to solve the above problems, a planar electrochemical sensor has been proposed. Its structure is ceramic,
It has a structure in which a working electrode, a counter electrode, and a reference electrode are formed on one surface of a strong insulating substrate such as glass by means such as vapor deposition or sputtering, and a gas permeable solid electrolyte is applied thereon.

Furthermore, in the planar electrochemical sensors mentioned above, there are some in which the working electrode and the counter electrode have a three-dimensional uneven structure in order to efficiently carry out electrochemical reactions and improve the output and sensitivity of the sensor. .

FIGS. 4 and 5 show the structure of an electrochemical sensor having such a three-dimensional uneven structure. This sensor is constructed by forming a large number of convex portions 11 on a flat surface of an insulating substrate 10, and forming a working electrode 20 and a counter electrode 30 so as to cover the convex portions 11.
0 has a three-dimensional uneven structure. Reference electrode 40 is working electrode 2
0 and the counter electrode 30 on a flat portion without a convex portion 11. The solid electrolyte layer 50 covers the surface of the insulating substrate IO with a certain thickness, and a part of the convex portion 11 provided with the action i20 and the counter electrode 30 is exposed above the solid electrolyte layer 50. One end of each electrode 2o is extended and exposed to the outside of the solid electrolyte layer 50, and serves as a terminal portion 22, 32, 42 for connection to an external circuit. In a sensor having such a three-dimensional uneven structure, a good electrochemical reaction occurs at the boundary between the electrode 20, 30, the solid electrolyte N50, and the outside world, and the sensitivity or output of the sensor can be improved.

In the conventional planar electrochemical sensor as described above, the three-dimensional uneven structure is formed by processing the insulating substrate 10 made of an insulating material such as synthetic resin or ceramic by physical or chemical means to form the uneven structure. In addition to this method, there is a method of forming an insulating substrate 10 by processing a concavo-convex structure on a conductive substrate and then forming an insulating layer on the surface thereof.

The above-mentioned method of forming an uneven structure on a conductive substrate and then forming an insulating layer has the advantage that it is possible to form a fine and accurate uneven structure by employing microfabrication methods such as photolithography technology. .

Specifically, for example, a method is employed in which a silicon substrate is used as the conductive substrate, a three-dimensional uneven structure is formed by alkali etching, and then an insulating layer of silicon dioxide is formed on the surface.

FIG. 6 shows an example of a method of forming the insulating substrate 10 as described above. An etching pattern 60 is formed on the flat surface of the silicon substrate 13 at a location corresponding to the convex portion 11, and the silicon substrate 13 is etched by etching with an alkaline solution, and the remaining portion becomes the convex portion 11. (al) After removing the etching pattern 60, an insulating substrate 14 is formed on the entire surface of the silicon substrate 13 by oxidizing the silicon substrate 13, thereby forming an insulating substrate 10 having a three-dimensional uneven structure. [During the process]
].

[Problem to be solved by the invention]

In order to make the sensor smaller in the planar sensor as described above, it is necessary to further miniaturize the three-dimensional uneven structure described above.
It is required that the shape be as fine as tts. However, forming the minute protrusions II in this way causes a problem that the strength becomes weak, and when the protrusions 11 are formed during use of the sensor, etc.
There is a problem in that the breakage or partial loss of the convex portion 11 causes electrode ifr lines of the working electrode 20 and the counter electrode 30 formed on the convex portion 11, resulting in deterioration of sensor performance.

In particular, in the method of forming the insulating substrate 10 by forming the insulating layer 14 on the surface of the conductive substrate 13, when forming the insulating layer 14, distortion occurs at the convex portions 11 of the substrate 13, especially at the roots. Since a large stress is applied to the protrusion 11, the protrusion 11 becomes weak in strength and becomes easily broken. FIG. 7 shows the area around the convex portion 11 when the insulating layer 14 is formed by performing oxidation treatment on the surface of the silicon substrate 13. As the formation reaction of the insulating Ji 14 progresses, the insulating layer 14 is deformed and Internal stress is generated, especially at the root portion of the convex portion 11, where the bottom and side surfaces intersect in an angular shape, and stress concentration is likely to occur. This makes it easier to destroy.

Note that such a decrease in strength at the root portion 12 of the convex portion 11 is particularly noticeable in the case of a structure in which the insulating layer 14 is formed on the surface of the conductive substrate 13 as described above, but This problem also occurs in the case of the insulating substrate 10 made of material.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electrochemical sensor of the Brehner type electrochemical sensor having a three-dimensional uneven structure as described above, in which the strength of the uneven structure is improved, and a method for manufacturing such an electrochemical sensor. It's about doing.

[Means to solve the problem]

An electrochemical sensor according to claim 1 of the present invention that solves the above problems is an electrochemical sensor in which a working electrode, a counter electrode, and a reference electrode are provided on the same surface of an insulating substrate, and each electrode is covered with an electrolyte layer. The surface of the substrate at the location where the working electrode and the counter electrode are provided has many uneven portions, and the root portion where the bottom surface and the side surface of the uneven portion intersect forms an arc shape.

Further, the invention according to claim 2, which is a method for manufacturing the electrochemical sensor as described above, is one in which the insulating substrate is composed of a conductive substrate and an insulating layer formed on the surface thereof, A large number of uneven parts each having an angular base where the bottom and side surfaces intersect are formed on the surface of the flexible substrate, and an oxide film is deposited on the surface of the uneven parts by a thermal oxidation method. By removing it, the root portion of the uneven portion on the substrate surface is formed into an arc shape, and then an insulating layer is formed on the surface of the conductive substrate.

[For production]

According to the invention as claimed in claim 1, since the root portion of the uneven portion of the insulating substrate where the bottom surface and the side surface intersect is formed in an arc shape, stress concentration at the root portion is reduced compared to a conventional square shape. It becomes much stronger in terms of strength, and is less likely to be destroyed even if minute unevenness is formed.

According to the invention as claimed in claim 2, when manufacturing an insulating substrate having a structure in which an insulating layer is formed on the surface of the conductive substrate, in the step of forming the uneven portion on the conductive substrate, the bottom and side surfaces of the uneven portion are The bases where the two intersect are formed into an angular shape (after depositing an oxide film on the uneven surface of the conductive substrate by a thermal oxidation method and then removing this oxide film, the conductive film becomes conductive during the oxide film formation process. The surface of the uneven portion of the substrate is processed by being locally deformed, so that the entire uneven portion has a smooth outer shape, and the root portion of the uneven portion is formed in an arc shape. If an insulating substrate is manufactured by forming an insulating layer on the surface of a conductive substrate having an arcuate root portion of the uneven portion, the root portion of the uneven portion of the insulating substrate will be arcuate, and the insulation layer will be At the stage of forming the layer, stress concentration is unlikely to occur at the arcuate root portions of the uneven portions, so that the strength of the uneven portions does not decrease due to the formation of the insulating layer.

〔Example〕

Next, while referring to the drawings showing embodiments of the present invention,
This will be explained in detail below.

FIG. 1 shows a schematic structure of an embodiment of an electrochemical sensor according to the present invention.

The basic structure of the sensor is the same as that of the conventional example described above, so common parts are given the same reference numerals and redundant explanation will be omitted.

A large number of thin plate-shaped protrusions 11 are arranged in two rows on the surface of an insulating substrate 10 which is formed by covering the surface of a conductive substrate 13 made of silicon or the like with an insulating layer 14 made of silicon dioxide or the like. A working electrode 20 and a counter electrode 30 are formed on the working electrode 20 and a counter electrode 30, and a reference electrode 40 is formed in a flat portion between the working electrode 20 and the counter electrode 30. Electrodes such as the working electrode 20 are made of ordinary electrode materials such as platinum and gold.

The surface of the insulating substrate 10 is covered with an electrolyte layer 50 made of a solid polymer electrolyte or the like, and a portion of the protrusion 11 is exposed above the electrolyte layer 50. One end of each electrode 20 extends to the outside of the electrolyte layer 50 and constitutes a terminal portion 22, 32° 42 for connection to an external circuit. The configuration described above is similar to the conventional electrochemical sensor described above.

In this embodiment, as shown in FIG. 1(a), the convex portion 11
The base 12, where the side surface and the bottom surface intersect, is formed into a smooth arc shape. The larger the size of the circular arc of the root portion 12, the less stress concentration will occur, which is preferable in terms of strength, but it is set to an appropriate size in consideration of the influence on the electrochemical reaction in the uneven structure, processing conditions, etc. In the illustrated embodiment, the upper corners of the convex portions 11 are also formed into smooth arc shapes, which makes it difficult for the upper corners of the convex portions 11 to be chipped or damaged, making it easier to form electrodes. It has the effect of being easy to perform.

Dimensions such as the height and spacing of the convex portions 11 are appropriately set in consideration of the output sensitivity of the sensor, processing conditions, etc., as in the case of an ordinary electrochemical sensor having a three-dimensional uneven structure. Convex portion 11
As shown in the figure, the structure includes various three-dimensional uneven structures, such as a structure in which a large number of elongated plate-like protrusions 11 are arranged in parallel, and a structure in which protrusion-like protrusions 11 are arranged vertically and horizontally or in a staggered manner. It can also be changed. In addition, in the illustrated example,
Although this is a structure in which the convex portions 11 protrude from the flat surface of the insulating substrate 10, it is also possible to form any structure with concave or convex structures, such as forming a large number of grooves on the flat surface of the insulating substrate 10.

The structure of each electrode 20 can also be changed to various structures employed in ordinary electrochemical sensors other than the structure of the illustrated embodiment.

Next, an example of a method for manufacturing an electrochemical sensor having the above structure will be described.

FIG. 2 schematically shows the process order from (al to (kl). First, a silicon dioxide layer 60 for etching is deposited on the flat surface of the (110) plane of the silicon substrate 13 using a thermal oxidation method. [Step (a)]. Apply a resist 70 on the silicon dioxide layer 60 [Step...)].
, exposure and development is carried out in a predetermined pattern, leaving the resist 70 only at the locations corresponding to the convex portions 11 of the working electrode 20 and the counter electrode 30 [Step (C)] Using the resist 70 thus formed as a mask, The silicon dioxide layer 60 is removed in a predetermined pattern to partially expose the surface of the silicon substrate 13. At this time, silicon dioxide jif 60 is patterned so as to be parallel to the intersection line of the (ITl) plane or the (110) plane of the silicon substrate 13, and the engraving of the silicon substrate 13 in the later process is performed. Make it easy to perform [Step (d)].

After removing the resist 70 [step (e)), KOH45
The silicon substrate 13 is dug to a certain depth using an etching solution containing 55 wt% of Hg and 55 wt% of Hg at a liquid temperature of 80° C., so that only the convex portions 11 remain in a protruding form [step (f)]. At this time, when the silicon substrate 13 is etched with the arrangement pattern of the silicon dioxide layer 60 as described above, etching is performed perpendicularly to the surface of the silicon substrate 13 due to the anisotropy of the etching rate depending on the plane orientation of the silicon substrate 13. The shape of the convex portion 11 can be formed accurately. Normally, etching time is 25
The digging of the silicon substrate 13 is completed in a certain degree. By removing the silicon dioxide layer 60 remaining on the upper surface of the convex portion 11 of the silicon substrate 13, the silicon substrate 13 having the predetermined convex portion 11 is obtained [Step (A)].

A silicon dioxide film 61, which is an oxide film for processing the protrusions, is deposited to a thickness of 1 μm over the entire surface of the silicon substrate 13, including the protrusions 11, by the same thermal oxidation method as described above [step (
h)]. This silicon dioxide film 61 is formed by HF:HmO=
When removed by etching using a 4:1 etchant,
The surface of the convex portion 11 of the silicon substrate 13 is processed to form the circular arc shape of the root portion 12 of the convex portion 11 and the convex portion 11 as described above.
A circular arc shape at the tip is formed [step (1)].

A silicon dioxide layer 1 serving as an insulating layer is spread over the entire surface of the silicon substrate 13 on which the convex portions 11 have been processed as described above.
4 is deposited to a thickness of 5,000 people, the silicon substrate 1
3 and a silicon dioxide layer 14, an insulating substrate 10 having a three-dimensional uneven structure is produced [step (j)].

Thereafter, each electrode 20 made of platinum or the like is formed to a thickness of about 11, for example, on the surface of the insulating substrate 10 using a normal electrode forming method such as a mask sputtering method [step (k)]. Furthermore, by covering the electrodes 20 with an electrolyte layer 50, an electrochemical sensor can be manufactured.

Among the steps described above, the step of processing the convex portion 11 of the silicon substrate 13, which is a feature of the present invention, will be explained in more detail with reference to FIG.

The convex portion 11 of the silicon base Fi 13 formed in the process (river) has a shape in which the side and bottom surfaces of the convex portion 11 intersect linearly,
It constitutes an angular corner portion, that is, a root portion 12. Therefore, if the insulating layer 14 is formed in this state,
Similar to the conventional example described above, stress concentration occurs at the root portion 12 of the convex portion 11, resulting in a decrease in strength. Therefore, the process (
In h), when a relatively thick oxide film 61 made of silicon dioxide is deposited over the entire surface of the silicon substrate 13, the oxide film 61 is distorted due to internal stress etc. generated when the oxide film 61 is formed, and the silicon substrate 13 give stress to This stress acts intensively on the root portion 12 and the like of the convex portion 11, causing the convex portion 11 to be locally deformed. When the oxide film 61 is removed, the silicon substrate 1
3 is released, but the deformation of the root portion 12 of the convex portion 11 remains, and the root portion 12 of the convex portion 11 and the tip of the convex portion 11 are processed into an arc shape.

After that, as shown in step (jl), if a relatively thin silicon dioxide layer 14 is formed as an insulating layer, the convex portion 11 having an arcuate root portion 12 will not receive stress even if the insulating layer 14 is formed. Since it has a shape that does not easily cause distortion, the strength of the convex portion 11 does not decrease, and the insulating substrate IO produced by the conventional method
It is possible to significantly improve the strength compared to

In the method for manufacturing an electrochemical sensor described above, the conductive substrate 13 and the insulating layer 14 that constitute the insulating substrate 10 are
In addition to the silicon substrate and silicon dioxide layer described above,
It is possible to use a combination of conductive substrate materials and insulating layer materials that are commonly used in various electronic devices.

Specific steps such as the method of forming uneven shapes such as the convex portions 11 on the conductive substrate 13 and the method of forming the electrodes 8ii20... can also be performed by applying ordinary manufacturing techniques for electrochemical sensors and other electronic devices. Can be done.

Insulating substrate 10 manufactured by the above manufacturing method
We will explain the results of a strength test to compare the strength of this product with that of a conventional product.

The insulating substrate 10 used in the test has a convex portion 11 having a structure as shown in FIG. 1 described above, and the width of the convex portion 11 is 5. Ill,
The gap between adjacent convex portions 11 is 5n. The test product is a practical product of the present invention in which a relatively thin insulating layer 14 is formed after the process of processing the protrusion 11 using the oxide film 61 described above, and the root portion 12 of the protrusion 11 has an arc shape. , and a conventional product in which the insulating layer 14 was directly formed without performing the processing step of the convex part 11, and after washing these with ultrasonic water for 10 minutes, it was observed whether the convex part 11 was destroyed. are shown in the table below.

From the results shown in Table 1, it can be seen that in the conventional product in which the insulating layer I4 was directly formed on the convex part 11 having the angular root part 12, all convex parts were removed after the test due to the stress generated in the process of forming the insulating layer 14. While part 11 was destroyed, silicon dioxide layer 6
In the case of an actual product having a convex portion 11 whose root portion 12 is processed into an arc shape by forming and removing step 1, the stress is alleviated even if the insulating layer 14 is formed, so that the convex portion 11 is not destroyed at all. The effectiveness of this invention was demonstrated.

〔Effect of the invention〕

The electrochemical sensor according to the present invention described above is
The strength of the uneven portion can be improved by forming the root portion of the uneven portion of the insulating substrate into an arcuate shape so that stress concentration is difficult to occur. Therefore, while the sensor is in use, there will be no problems such as damage to the uneven parts, deterioration of the sensor function, or disconnection of the electrodes, and the excellent performance of the sensor with the three-dimensional uneven structure. can be maintained stably over a long period of time, greatly improving the stability and reliability of the sensor.

In particular, when the insulating substrate has a structure in which the surface of the conductive substrate is covered with an insulating layer, an oxide film is first formed on the surface of the uneven portion formed on the conductive substrate by a normal method. By removing it with Stress concentration at the base of uneven parts can be alleviated,
The strength of the uneven portion can be improved more effectively.

[Brief explanation of the drawing]

FIG. 1 shows an electrochemical sensor according to an embodiment of the present invention, FIG. 1(a) is a perspective view of the whole, and FIG. Figures 2 (a) to (kl are schematic cross-sectional views showing the manufacturing process of the sensor in order, Figure 3 (g); (h), 01 are enlarged cross-sectional views of some of the previous steps;
FIG. 4 is a perspective view of a conventional example, FIG. 5 is a sectional view, FIG. 6 is a sectional view showing an example of a method for manufacturing an insulating substrate, and FIG. 7 is an enlarged sectional view of an uneven portion. 10... Insulating substrate 11... Convex portion 12... Root portion 13... Conductive substrate 14... Insulating layer 20.3
0°40... Electrode 50... Electrolyte layer 61...
Oxide film diagram 1

Claims (1)

[Claims] 1. In an electrochemical sensor in which a working electrode, a counter electrode, and a reference electrode are provided on the same surface of an insulating substrate, and each electrode is covered with an electrolyte layer, insulation at a location where the working electrode and the counter electrode are provided. An electrochemical sensor characterized by having a large number of uneven parts on the surface of a substrate, and having an arcuate base where the bottom and side surfaces of the uneven parts intersect. 2 The insulating substrate is composed of a conductive substrate and an insulating layer formed on the surface thereof, and the surface of the conductive substrate has many irregularities whose bases where the bottom and side surfaces intersect are angular. After forming an oxide film on the surface of the uneven portion by a thermal oxidation method and removing this oxide film, the root portion of the uneven portion on the substrate surface is processed into an arc shape,
Claim 1: An insulating layer is formed on the entire surface of the conductive substrate.
A method of manufacturing the electrochemical sensor described above.