JPH0641930B2 - Method for manufacturing oxygen concentration detecting element - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an oxygen concentration detection element having a laminated structure of thin films and including a so-called solid electrolyte thin film.

BACKGROUND ART An oxygen detection element is used, for example, for the purpose of detecting the oxygen concentration in a fluid. For example, by detecting the oxygen concentration in the exhaust gas of an automobile, so-called air-fuel ratio (combustion air / fuel ratio) control is performed. It is also used in various industrial furnaces. The following types have been used as conventional oxygen concentration detecting elements used for such purposes. With the fact that oxygen is a paramagnetic gas,
A type that detects the degree of magnetization of oxygen in a magnetic field. In this case, although the device can be used at room temperature, there is a problem that the device is large, complicated and expensive.

In addition, in the type using a metal oxide semiconductor, titanium oxide TiO ₂ , tin oxide SnO ₂ and neodymium oxide Nb _{2 are used.}
For example, at a high temperature of 700 ° C. or higher, a metal oxide such as O ₅ is redox-reduced to an extent depending on the oxygen concentration in the atmosphere, and the electric resistance value of the metal oxide changes correspondingly. We are using. This type has the advantage of being simple and compact in structure, but at the time of use, the atmospheric gas containing oxygen gas must be at a high temperature, and at such a high temperature, carbon monoxide CO, CO Methane CH ₄ , nitrogen oxide NOx, sulfide SO
There is a problem that it is easily affected by x and the like.

In the type using a so-called solid electrolyte whose electric resistance changes according to the oxygen concentration in the fluid, for example, a relatively large ceramics material has been used. When such a relatively large ceramics material is used, it is necessary to increase the oxygen ion conductivity of the solid electrolyte ceramics in order to detect the oxygen concentration in the fluid to be measured with high accuracy. Therefore, it is necessary to raise the temperature of the solid electrolyte ceramics to a high temperature of 800 ° C., for example.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In such an oxygen concentration detecting element of the related art and the manufacturing method thereof, the stabilizer contained in the solid electrolyte scatters. The component ratios varied, the oxygen ion conductivity of the solid electrolyte was lowered, and the characteristics in oxygen concentration detection were lowered.

The object of the present invention is to solve the above-mentioned problems, and in the solid electrolyte thin film, the stabilizer is uniformly distributed in the thickness direction of the solid electrolyte thin film layer in a desired manner, thus improving the characteristics of the oxygen concentration detection element. It is an object of the present invention to provide a method of manufacturing an oxygen concentration detecting element, which is capable of significantly simplifying the manufacturing process.

Means for Solving the Problems According to the present invention, a stabilized zirconia thin film is formed by depositing a molecule of stabilized zirconium, which is composed of zirconium oxide and a metal oxide stabilizer, on a substrate, and then an electrode is formed. In the method for manufacturing an oxygen concentration detecting element, a silicon substrate is used as the substrate, a step of forming an aluminum nitride film on the silicon substrate, a step of forming the stabilized zirconia thin film on the aluminum nitride film, and Forming a porous upper electrode on the stabilized zirconia thin film; forming a through hole from the lower surface of the silicon substrate to the stabilized zirconia thin film; and a porous lower electrode so as to cover the through hole. And a step of forming the oxygen concentration detecting element.

Action According to the present invention, in the production of an oxygen concentration detection element having a stabilized zirconia thin film consisting of zirconium oxide and a metal oxide stabilizer, in forming an aluminum nitride thin film on a silicon substrate, sputtering method, chemical Formed by a method such as a dynamic vapor deposition method (CVD method), an atomic layer growth method (ALE method) and an ion plating method, on which a thin film of stable zirconia, which is a kind of solid electrolyte, is formed. The upper electrode is formed on the stabilized zirconia thin film by a method similar to the forming method, a through hole reaching from the lower surface of the silicon substrate to the stable zirconia thin film is formed, and the lower electrode is formed so as to cover the through hole. To form. Therefore, since molecules of the stabilized zirconia are deposited on the substrate to form a thin film, the stabilized zirconia thin film can be manufactured on the aluminum nitride thin film on the silicon substrate in a single manufacturing process to a desired film thickness. Further, the component ratio of the stabilizer can be formed uniformly in the thickness direction, and the stabilized zirconia thin film for detecting the oxygen concentration is formed relatively thin, so that it can be measured at a relatively low temperature. Furthermore, since a highly insulating aluminum nitride film is provided between the silicon substrate and the stabilized zirconia thin film, the current flowing through the silicon substrate, which is a semiconductor, can be interrupted and the current can be concentrated in the through hole. The oxygen concentration can be detected with high sensitivity.

Example FIG. 1 is a sectional view for explaining a manufacturing method of an example of the present invention. As shown in FIG. 1 (1), aluminum nitride AlN is formed on a silicon substrate 1 by sputtering, chemical vapor deposition (CVD), atomic layer growth (ALE).
Method), vacuum deposition method and ion plating method,
The aluminum nitride thin film 2 is formed by using at least one of the methods of forming a thin film by depositing molecules of a solid electrolyte on a substrate.

Next, as shown in FIG. 1 (2), the stabilized zirconia thin film 3 is formed on the surface of the aluminum nitride thin film 2 opposite to the substrate 1.
To form. Stabilized zirconia is a so-called solid electrolyte, and contains zirconium oxide ZrO ₂ in yttrium oxide Y ₂ O ₃ , magnesium oxide MgO, calcium oxide CaO, samarium oxide Sm ₂ O ₃ , ytteribium oxide Yb ₂ O ₃ , and scandium oxide Sc. Stabilizers such as ₂ O ₅ , gadolinium oxide Gd ₂ O ₃ and neodymium oxide Nd ₂ O ₃ are added at 6.1 to 12.6 mol% and the growth temperature is 550
A film thickness of 0.5 to 10 μm is formed at an ambient temperature of up to 1000 ° C. Such a stabilized zirconia thin film 3 (Z
rO ₂ ) _1-n (Y ₂ O ₃ ) n or (ZrO ₂ ) _1- n (Mg
O) n, (ZrO ₂ ) _1- n (CaO) n, (ZrO ₂ ) _1-
n (Sm ₂ O ₃ ) n, (ZrO ₂ ) _1- n (Yb ₂ O ₃ ) n,
(ZrO ₂ ) _1- n (Sc ₂ O ₅ ) n, (ZrO ₂ ) _1- n (G
It has a chemical structure such as d ₂ O ₃ ) n, (ZrO ₂ ) _1- n (Nd ₂ O ₃ ) n. However, the value of n is 0.05 to 0.2.

That is, by forming the stabilized zirconia thin film 3 in this way, the manufacturing process is significantly simplified. In addition, the above-mentioned stabilizer molecules in the stabilized zirconia thin film 3 do not scatter during the production of the stabilized zirconia thin film 3, and therefore the composition ratio of the above stabilizer is not uniform in the thickness direction. Could be prevented.

In FIG. 1 (3), a porous upper electrode 4 made of, for example, platinum Pt is formed on the surface of the stabilized zirconia thin film 3 by, for example, a sputtering method, for example, 1000
Formed. Then, in FIG. 1 (4), silicon dioxide SiO ₂ 5 is formed on the opposite side of the stabilized zirconia thin film 3 of the substrate 1 using a lithography method and an anodic oxidation method, and anisotropic etching is performed. Then, a through hole 6 reaching the surface of the stabilized zirconia thin film 3 on the side opposite to the upper electrode 4 was formed. In FIG. 1 (5), the through hole 6 is covered to form a porous lower electrode 7 made of, for example, platinum.
In the same manner as the upper electrode 4 by the sputtering method, etc.
For example, 1000 formed. In this way, the oxygen concentration detection element 8 was constructed.

The structure for detecting the acidity concentration using the oxygen concentration detecting element 8 manufactured in this manner is similar to that of a solid electrolyte type oxygen detector which has been conventionally used. For example, JP-A-59-166854. Is shown in. Figure 2 shows
It is a figure which shows an example of such an oxygen concentration detector. A constant voltage power supply 9 applies a constant level voltage between the upper electrode 4 and the lower electrode 7 of the oxygen concentration detection element 8. An ammeter 10 for measuring a current flowing between both electrodes 4 and 7 of the acidity concentration detecting element 8 is connected in series with the oxygen concentration detecting element 8. In the acidity concentration detecting element 8, a fluid to be detected containing oxygen gas is brought into contact with the upper electrode 4 side, and a fluid having oxygen gas with a reference concentration is brought into contact with the lower electrode 7 side.

In such a configuration, since the electrodes 4, 7 are porous as described above, the oxygen gas on the electrodes 4, 7 side is
Both surfaces 1 of the stabilized zirconia thin film 3 through
Contact 1,12. In the stabilized zirconia thin film 3, oxygen ions O ²⁺ flow from the high concentration side to the low concentration side. That is, assuming that the oxygen gas concentration on the upper electrode 4 side is lower than the oxygen gas concentration on the lower electrode 7 side, such oxygen ions flow in the direction of arrow A1. That is, a current flows through the stabilized zirconia thin film 3.

The flow rate of such oxygen ions depends on the concentration difference of the oxygen gas concentrations among the flow rates on the electrodes 4 and 7 side, and the flow rate of oxygen ions increases as the concentration difference increases. Therefore, the current value corresponding to the oxygen gas concentration difference between the upper electrode 4 side and the lower electrode 7 side is read as the current value between the electrodes 4 and 7 with the ammeter 10 to determine the oxygen gas concentration difference between the two electrodes. Can be detected. The oxygen gas concentration in the fluid to be detected on the upper electrode 4 side can be known by performing a calculation based on the detected concentration difference and the reference oxygen gas concentration on the lower electrode 7 side.

The oxygen concentration detecting element 8 manufactured by the manufacturing process as described above is manufactured by the so-called thin film manufacturing technique as described above, and a large number can be simultaneously manufactured on the substrate 1. Therefore, the manufactured oxygen concentration detecting element 8 can be obtained with uniform quality. Further, since the stabilized zirconia thin film 3 is manufactured by the above-mentioned thin film manufacturing technique, it is easy to control the physical and chemical characteristics of the stabilized zirconia thin film and the electrodes 4 and 7 with high precision, and the quality is remarkably high. It is possible to manufacture the oxygen concentration detection element 8 that has been improved. In addition, the obtained stabilized zirconia thin film 3 is 0.5 to 10
Since the thickness can be significantly reduced to μm, the impedance of such a thin film can be significantly reduced, and at a lower temperature than the solid electrolyte made of the comparatively large ceramics of the first conventional art. It can be operated.
Also, due to this low temperature, the solid electrolyte thin film on the substrate,
It is possible to prevent the phenomenon in which the substrates and the solid electrolyte thin film are separated from each other due to the difference in the coefficient of thermal expansion between the substrates. Further, since the aluminum nitride film 2 having a high insulating property is provided between the silicon substrate 1 and the stabilized zirconia thin film 3,
The oxygen concentration can be detected with high sensitivity by interrupting the current flowing through the silicon substrate 1 and concentrating the current in the through hole.

Effects According to the present invention as described above, an aluminum nitride film is formed on a silicon substrate, and in forming a stabilized zirconia thin film that is a solid electrolyte on the aluminum nitride film, a sputtering method, a chemical vapor deposition method, It was manufactured using a method of forming a thin film by depositing molecules of a film-forming substance such as an atomic layer growth method, a vacuum deposition method and an ion plating method. Therefore, the distribution state of the stabilizer molecules in the stabilized zirconia thin film can be made uniform in the thickness direction of the stabilized zirconia thin film, and therefore the device characteristics can be remarkably improved. Further, such thin films of aluminum nitride and stabilized zirconia could be manufactured by a simple process, and the characteristics of the obtained oxygen concentration detecting element could be made uniform, and the operating temperature could be made relatively low. Therefore, the power consumption associated with the use of the oxygen concentration detection element can be significantly reduced. Furthermore, since a highly insulating aluminum nitride film is provided between the silicon substrate and the stabilized zirconia, the aluminum nitride film serves as an etching stopper when forming a through hole reaching the stabilized zirconia thin film from the lower surface of the silicon substrate. The current flowing through the silicon substrate, which is a semiconductor, can be blocked, and the oxygen concentration can be detected with high sensitivity by concentrating the current in the through hole.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating a manufacturing process of the oxygen concentration detecting element 8, and FIG. 2 is a diagram showing a configuration for performing an oxygen concentration detecting operation using the oxygen concentration detecting element 8 according to an embodiment of the present invention. is there. DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... Aluminum nitride thin film, 4 ... Upper electrode, 7 ... Lower electrode, 8 ... Oxygen concentration detection element

Front page continuation (72) Inventor Tsukasa Doi 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (56) Reference JP-A-61-147154 (JP, A)

Claims (1)

[Claims] 1. A method for producing an oxygen concentration detecting element, comprising forming a stabilized zirconia thin film by depositing molecules of stabilized zirconia comprising zirconium oxide and a metal oxide stabilizer on a substrate to form an electrode. In the method, a silicon substrate is used as the substrate, an aluminum nitride film is formed on the silicon substrate, a step of forming the stabilized zirconia thin film on the aluminum nitride film, and a porous layer is formed on the stabilized zirconia thin film. Quality upper electrode, forming a through hole from the lower surface of the silicon substrate to the stabilized zirconia thin film, and forming a porous lower electrode so as to cover the through hole. A method for manufacturing an oxygen concentration detecting element, comprising: