JPH0454445A - Production of oxygen sensor - Google Patents

Abstract

PURPOSE:To form an LaF3 thin film into a dense structure so as to prevent film cracking and to improve durability by utilizing an ion shower method to project particles of an inert gas on the thin film surface at the time of forming the above-mentioned thin film. CONSTITUTION:A platinum film is formed on a silicon substrate 1 to form a 1st electrode 2 and LaF3 is deposited by evaporation on the prescribed elec trode 2 by a vapor deposition method with an electron beam to form the LaF3 thin film 3 of a prescribed thickness. The ion shower method of providing electrodes in an electron beam device, introducing gaseous argon into the device, accelerating the argon ionized together with the vapor deposition molecules of the LaF3 between the electrodes and radiating the ions to a substrate is used at the time of executing the vapor deposition with the electron beam. The platinum film of a prescribed thickness is formed on this thin film to form a 2nd electrode 4. The LaF3 thin film having the dense structure is formed in this way. The film cracking is substantially prevented and the durability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an oxygen sensor used for measuring oxygen concentration in exhaled breath, monitors of oxygen inhalers, etc., and automobiles.

B8 Summary of the Invention The present invention uses lanthanum fluoride represented by the molecular formula LaF as a solid electrolyte, and when forming the above-mentioned LaF3 thin film by electron beam evaporation, ionized inert gas particles collide with the above-mentioned thin film. By using the ion shower method to smooth the thin film surface, the solid electrolyte structure of the LaF3 thin film oxygen sensor was made denser and its durability was improved.

C9 Conventional technology Conventionally, stabilized zirconia, which is a solid solution of zirconium oxide with the chemical formula ZrO2 and yttrium oxide with the chemical formula Y2O3 as a stabilizer, has been used as a solid electrolyte to measure oxygen contained in fuel gas, etc. A new type of thin film oxygen sensor using thin film microfabrication technology has been developed to improve the responsiveness and miniaturize oxygen sensors using solid electrolytes.

However, since ZrO2 used as a solid electrolyte requires a high temperature of 700°C or higher as an operating condition, oxygen sensors that can operate at low temperatures are currently being researched. is proposed.

However, although the LaF3 single crystal oxygen sensor can operate at a lower temperature than conventional sensors, it is very expensive and is not suitable for commercial use.

Therefore, a thin film oxygen sensor using a thin film of LaF3 as a solid electrolyte is being researched, and in the prior art, a resistance heating method is used as a method for thinning the film.

D1 Problems to be Solved by the Invention Conventionally, it has been desired to realize an oxygen sensor that has a fast response speed to oxygen concentration, is small in size, and can operate at low temperatures. Sensors were being researched.

However, the LaF3 thin-film oxygen sensor manufactured using the conventional resistance heating method satisfies the conventional demands of improved response speed, miniaturization, and lower operating temperature, and is significantly more efficient than the LaF3 single-crystal oxygen sensor. Although it has the advantage of being able to reduce costs, it has the disadvantages of being prone to cracking due to the rough structure of the membrane and lack of durability, so it has not been put into practical use.

The present invention was made against this background, and
An object of the present invention is to provide a method for manufacturing a LaF3 thin film oxygen sensor, which has a dense film structure, prevents film cracking, improves durability, and reduces costs.

80 Means for Solving the Problems In order to achieve the above-mentioned problems, the present invention provides a method for manufacturing an oxygen sensor in which electrodes are formed on both sides of a solid electrolyte layer, in which an electron beam is applied to a deposition source made of LaFs. The method is characterized in that it emits vapor-deposited molecules onto the electrode by irradiation, and at the same time causes ionized inert gas particles to collide with the electrode to form a LaF3 layer, which is a solid electrolyte layer, on the electrode.

F3 action In the present invention, when forming a LaF3 thin film, the formed LaF2 thin film is made dense and smooth by utilizing an ion shower method in which inert gas particles collide with the surface of the thin film.

G. Example Hereinafter, a method for manufacturing a LaF3 thin film oxygen sensor in this example will be explained with reference to FIG.

A platinum film having a thickness of about 5000λ is formed on a silicon substrate 1, preferably by a sputtering method, as a first electrode 2,
Further, on this first electrode 2, La is deposited by electron beam evaporation method.
F3 is deposited to form a LaF3 thin film 3 having a thickness of 2 μm.

Here, when performing electron beam evaporation, electrodes are provided in the electron beam device, argon gas is introduced, and LaF
An ion shower method is used in which ionized argon is accelerated together with the vapor-deposited molecules of step 3 and radiated onto the substrate.

As shown in FIG. 3, the ion shower device used in the method of the present invention places a shutter 13 and a silicon substrate 15 attached to a sample holder 14 on a straight line in this order above a container 12 containing a deposit. At the same time, a pair of electrodes 16.
16 are arranged opposite to each other, and an electron beam gun 11 is further provided for irradiating the deposited material with an electron beam.

When this apparatus is made into a vacuum atmosphere and an inert gas is introduced, and an electron beam is irradiated from the electron beam gun II and a voltage is applied between the electrodes 16 and 16, vapor deposition molecules are radiated onto the silicon substrate 15 and at the same time the inert gas is ionized and collides with the thin film layer formed on the silicon substrate 15.

In this example, argon gas is introduced into a vacuum of 6.67
Set to mA and apply an electron beam applied voltage of 6.0■.
A 1-5 mm pellet of LaF3 is used for the deposition.

In addition, by using small particle size LaFs as the deposit,
The thin film formed has a denser, smoother structure.

After forming the LaF3 thin film 3 in this manner, a platinum film having a thickness of about 500 OA is formed on this thin film by sputtering to form the second electrode 4.

Furthermore, the method for producing the first electrode and the second electrode is not limited to the sputtering method, but may also be a resistance heating method, a platinum paste coating method, or the like.

In addition, FIG. 2 shows both electrodes when the measurement temperature is 300°C, the first electrode 2 side of the oxygen sensor according to the present invention is the standard air side, and the exhaust gas with a low oxygen concentration is sent to the second electrode 4 side. Graph (1) shows the measurement results of the electromotive force generated between the
Graph (2) of measurement results using the Fs single crystal oxygen sensor
Shown below.

Graphs (1) and (2) show that the equilibrium state values are not much different, but the LaF3 thin film oxygen sensor clearly takes a faster time to reach equilibrium and has improved responsiveness.

H0 effect As mentioned above, the L
The aF3 thin film has a dense structure, making it extremely difficult for film cracking to occur and improving durability.

As a result, a LaF3 thin film oxygen sensor that has higher responsiveness, is smaller, operates at lower temperatures, and is lower in cost than conventional oxygen sensors will be put into practical use.

[Brief explanation of the drawing]

Fig. 1 is a structural diagram of an oxygen sensor according to the present invention, and Fig. 2 is a structural diagram of an oxygen sensor according to the present invention.
Output characteristic diagrams of an aF3 thin film oxygen sensor and a LaF3 single crystal oxygen sensor, and FIG. 3 is a schematic explanatory diagram of an ion shower device. DESCRIPTION OF SYMBOLS 1... Silicon substrate, 2... First electrode, 3... Lanthanum fluoride thin film, 4... Second electrode, 11... Electron beam, 12... Container, 13... Shutter 14
... Sample holder 15 ... Silicon substrate, 16
... Electrode Figure 1 Structure diagram of the oxygen sensor according to the present invention Figure 2 Output characteristic diagram of the oxygen sensor Time (minutes) Figure 3 Schematic diagram of the ion power device 0 = 22 11 11

Claims (1)

[Claims] (1) In a method for manufacturing an oxygen sensor in which electrodes are formed on both sides of a solid electrolyte layer, an electron beam is irradiated onto a deposition source made of LaF_3 to emit deposition molecules onto the electrodes, and at the same time an ionized inert A method for manufacturing an oxygen sensor, characterized in that a LaF_3 layer, which is a solid electrolyte layer, is formed on the electrode by colliding gas particles with the electrode.