JPS5831741B2 - Zinc oxide piezoelectric crystal film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric crystal film made of zinc oxide.

Methods for producing piezoelectric crystal films of zinc oxide include vacuum evaporation, gas phase reaction, and sputtering.

Among these methods, for example, the sputtering method, particularly the high-frequency sputtering method, has the advantage that the growth rate of an axially oriented crystal film is fast and that it can be mass-produced industrially.

When creating a piezoelectric crystal film of zinc oxide on an adhered surface using this high-frequency sputtering method, a sintered body of high-purity zinc oxide was conventionally used as a target. However, the adhesion of the obtained crystal film was poor and the film was not of good quality.

Also, it was difficult to make the C-axis perpendicular to the surface to which it was adhered.

If the adhesion of the zinc oxide piezoelectric crystal film is poor as described above, for example, when a surface acoustic wave filter is constructed with this piezoelectric crystal film, the film may peel off, resulting in the formation of tooth-shaped electrodes.
＜、There were disadvantages in that disconnection accidents were more likely to occur and propagation loss was also large.

Furthermore, if the C-axis is tilted with respect to the axis perpendicular to the adhered surface, the value of the electromechanical coupling coefficient becomes small, making it difficult to obtain a zinc oxide piezoelectric crystal film with good conversion efficiency.

As a result of various studies on these problems, we discovered that by incorporating vanadium and manganese into a zinc oxide piezoelectric crystal film, a high-quality piezoelectric crystal film with the C-axis perpendicular to the adhering surface can be obtained. .

In order to explain the present invention, an example in which a piezoelectric crystal film of zinc oxide is made to contain vanadium and manganese using a high frequency sputtering method will be described below.

FIG. 1 shows a high frequency bipolar sputtering apparatus for forming a piezoelectric crystal film of zinc oxide.

Reference numeral 1 denotes an airtight container (bell jar), and a pair of parallel plate-shaped cathode 2 and anode 3 are arranged in this airtight container 1.

A target 4 made of zinc oxide containing vanadium and manganese is fixed on the cathode 2.

5 is a shutter.

A substrate 6 of glass, metal, etc. to be deposited is fixed to the anode 3, and this substrate 6 is heated to a temperature of 200 to 500 nm during sputtering.
It is heated in the range of 0°C.

7 is an exhaust hole, and 8 is a gas inlet.

To perform high frequency sputtering, the airtight container 1 is sealed and then evacuated from the exhaust hole 7 to a degree of vacuum of I.times.10@-6 Torr or higher.

Next, argon, oxygen, or a mixed gas of oxygen and argon is introduced from the gas inlet 8 until the gas pressure is lXl0-1~1.
x1O-3 Torr.

A high frequency voltage is applied to the cathode 2 by a high frequency power supply 9.

High frequency power of 2 to 8 W/cnl per unit area is supplied to the target 4.

A target made of a sintered body of zinc oxide containing vanadium and manganese was prepared as follows.

ZnO, V2O5, and coffee powders were used as raw materials and mixed in the proportions shown in Table 1, followed by wet mixing.

After dehydrating these, they were calcined at 600-800*°C for 2 hours.

Next, it was ground and mixed with an organic binder in a wet mill, further dehydrated, dried, and then sized.

Thereafter, the powder was press-molded at a pressure of 1000 kg/cJ to form a disc with a diameter of 100 mm and a thickness of 57 nTIL.

Furthermore, the molded disk was fired at 1000° C. for 2 hours to create a target sample containing vanadium and manganese.

The specific resistance of the obtained target and the percentage of the sintered density with respect to the theoretical density (sintered zone W7. theoretical density X100) were measured, and the results shown in Table 1 were obtained.

Using each target sample, a piezoelectric crystal film of zinc oxide was formed on a glass substrate using a high-frequency sputtering device.

High frequency sputtering was performed under the following conditions.

That is, 90% of argon is introduced into the airtight container 1 from the gas inlet 8.
A mixed gas of 10 volumes and 10 volumes of oxygen was introduced, and the pressure in the airtight container 1 was set to 2×10-” Torr1.The glass substrate to be the adhering surface was heated to 350°C.

Further, power of 6 W/cd was supplied to the target 4 at a frequency of 13.56 MHz per unit area, for example.

The C-axis orientation of the piezoelectric crystal film of zinc oxide obtained in this way was determined using the X-ray diffraction rocking curve method (References: Akata, Chubachi, Kikuchi, "Quantitative representation method of crystal axes in ZnO crystal thin films") ``Introduction of Pole Figures and Normal Distribution Approximation)'' 20th International Union of Materials Lecture Proceedings, 2 (1973) 84. Makoto Kuriki Tohoku Canine Studies Doctoral Dissertation (1974)).

The average value and standard deviation σ of the degree of inclination of the C-axis with respect to the axis perpendicular to the adherend surface were determined.

In addition, the membrane resistance, membrane quality, and adhesion of each sample were measured using MIL
-8TD-202D test method 107C, those in which the piezoelectric crystal film has peeled off from the glass substrate are rated "unacceptable", those with cracks are rated "slightly good", and those with no change are rated "
"Good."

Each characteristic of the piezoelectric crystal film described above is shown in Table 1.

From Table 1, it can be seen that the C-axis of the invention is almost perpendicular to the surface to which it is adhered, and as a result, a large electromechanical coupling coefficient can be obtained, and an excellent piezoelectric crystal film with high conversion efficiency can be obtained. I can see that it is being done.

In addition, a high-quality piezoelectric crystal film with smooth film quality and good adhesion was obtained.

In Table 1, each characteristic of the zinc oxide piezoelectric crystal film for sample numbers 8 and 9 is indicated with a "-", but this is because the C axis is not oriented perpendicularly to the adhered surface, and the piezoelectric crystal film This means that the characteristics were not evaluated because it cannot be used as a.

As is clear from Table 1, there is an appropriate range for vanadium and manganese to be contained in the zinc oxide piezoelectric crystal film, and the content may be within the following range.

That is, vanadium may be in the range of 0.01 to 20.0 atomic ratios in terms of vanadium atomic ratios.

If it is less than 0.01 atomic ratio, the film quality will deteriorate, and 20.
This is because if the ratio exceeds 0 atoms, the orientation deteriorates.

Regarding manganese, the number of atoms of manganese is o, oi ~ 20. It is sufficient if it is within the range of O atoms.

This is because if the amount is less than 0.01 atoms, the resistivity of the piezoelectric crystal film of zinc oxide will not increase and the quality of the film will be poor, and if it exceeds 20.0 atoms, the orientation will be poor.

In the above example, vanadium and manganese were contained in the target, but other compounds of vanadium and manganese may also be used, as long as vanadium and manganese are contained in the piezoelectric crystal film of zinc oxide obtained. The effect of this can be obtained.

Further, in the above-mentioned embodiments, a high-frequency sputtering method was used, but other methods such as simultaneous sputtering method or ion blating method may be used as long as vanadium and manganese can be contained in the piezoelectric crystal film of zinc oxide. .

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a sputtering apparatus used to explain an embodiment of the present invention. 1... Airtight container, 2... Cathode, 3...
...Anode, 4...Target, 6...
··substrate.

Claims (1)

[Claims] 1 A piezoelectric crystal film of zinc oxide whose C axis is perpendicular to the surface to which it is adhered, characterized in that the piezoelectric crystal film contains 0.01 to 20.0 atoms of vanadium and manganese, respectively. Zinc oxide piezoelectric crystal film.