JPS605236B2 - Zinc oxide porcelain for high frequency sputtering - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to zinc oxide ceramic used as a target for high frequency sputtering.

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

Among these sputtering methods, there are two types of sputtering methods: a DC two-pole type, a DC three-pole type, and a high-frequency sputtering method. The DC bipolar type is the simplest of the sputtering methods, but unless the resistivity of the zinc oxide porcelain target is low, positive charges will accumulate on the surface of the target exposed to ions, resulting in poor sputtering. This could not be done efficiently and stable discharge could not be maintained.

Furthermore, since a target with low specific resistance is used, the specific resistance of the obtained film also tends to be low. Although these films can be used at high frequencies due to the dielectric relaxation phenomenon, they have not been able to be used over a wide range of low frequencies.
Further, in such a sputtering method, an active gas such as oxygen, an inert gas such as argon, or a mixture thereof is generally used as the atmospheric gas.

One method of increasing the specific resistance of a crystal film is to increase the amount of oxygen in the atmospheric gas, but this method has the drawback of slowing down the growth rate of the crystal film. On the other hand, the high-frequency sputtering method has the advantage that it can be used with both low-resistance and high-resistance targets.
In order to industrially mass-produce crystalline films, the growth rate of the film must be increased.

For this purpose, a high-density target is required. In other words, if the density is high, the power applied per unit area of the target (power density) can be increased, and the growth rate of the film increases. Furthermore, as mentioned above, if a piezoelectric crystal film of zinc oxide is to be used in a wide range from low frequency range to high frequency range, it is necessary to increase the specific resistance of the crystal film, and a high resistance target is required. .

Conventionally, high-purity zinc oxide porcelain was used as the target, but when the pre-fired molded product is fired at a high temperature of 1300℃ or higher, the fired density becomes over 90% of the theoretical density, but the specific resistance becomes low. , it is unsuitable as a target for high frequency sputtering.

On the other hand, if fired at less than 1300 qo, the specific resistance will be high, but the fired density will be less than 30% of the theoretical density, which is also unsuitable as a target. No density was obtained. For example, a low-density target (burning stripe density/theoretical density x 10
0<90%), the surface of the obtained piezoelectric crystal film becomes uneven.

This is presumed to be due to the zinc oxide clusters flying unevenly in the form of souls. As a result of various studies on the above-mentioned problems, we found that porcelain obtained by incorporating glass into zinc oxide can provide a target with high resistivity, high density, and little difference in density distribution throughout the porcelain. I put it out. The glass to be contained in the target here is Si02, B2Q, etc., as introduced in the "Glass Handbook" (edited by Masao Sakka, Teruo Sakaino, and Katsuaki Takahashi, published by Ichi Asakura Shoten, September 30, 1973). single component, two-component systems such as Li20-&03, Na20-Si02, Na20-Sj02, K20-Ca
○-Sj02, Li20-K20-Ca○-Si02,
There are multi-component systems such as Na20-K20-Ca○-ku03-Si02.

This invention will be described in detail below according to examples.

After calcining Zn○ powder, which is the raw material for the example, at 600 to 80,000 for 2 hours, glass powder was mixed to obtain porcelain in the ratio shown in Table 1, and at the same time, it was ground together with organic/winder in a green mill. Mixed.

The glass powder used here was processed into a vibrating mill for 40 degrees of esh.
I used the one that was crushed before and after. Next, it was dehydrated, dried, and then sized. Thereafter, the powder was pressed at a pressure of 1000 k9/carp and molded into a disc with a diameter of 10 m and a thickness of 5 skin. Furthermore, the molded disk was fired at 900 to 1200 qo for 2 hours to create a target sample containing glass. In addition, the first
The firing temperature of sample number 1, which is a reference example in the table, is 1250qo
It is. When the resistivity of the obtained target and the percentage of the fired density with respect to the theoretical density (agglomerated density/theoretical density xlooo) were measured, the results shown in Table 1 were obtained.

Here, the theoretical density of zinc oxide was assumed to be 5.67 ta'. In Table 1, sample number 1 is a conventional sample without glass added, and the others are samples according to the present invention. "Abbreviated younger sister" Mechuyafubi A-kei Houki-Q', 〇Mesan-Oki- Utakauki Shin≦Sa column※・Next, in order to examine the density distribution of the target, start from the center of the target as shown in Figure 1. Square plates were cut out at 0, 10, 20, 30, and 40 skin intervals, approximately 10 x 1 side, and 3 to 4 sides thick.

Both sides and the surrounding area of the cut porcelain were polished, a thin wax layer was attached on the surface, and the sample was used as a measurement sample for sintered density.
The density was measured using hexachloro-1,3-butadiene (2
The process was carried out by the Archimedes method using a 1.682-mass block (density 1.682 at 0qo) as the immersion liquid.

Table 2 shows the sintered density at each measurement position and its standard deviation (
This figure shows the following. Table 2 *Reference Example From Table 2, the density variation in the position of the sintered porcelain according to this invention, that is.

It can be seen that this has been significantly improved. Next, a piezoelectric crystal film of zinc oxide was created by high-frequency sputtering using the target described above.

FIG. 2 shows an apparatus for implementing a high frequency bipolar sputtering method among high frequency sputtering methods.

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.

Each target sample 4 described above is fixed on the cathode 2 . 5 is a shirt evening.

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 0qo. 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 1×10 −6 tons or more.

Next, introduce argon, oxygen, or a mixed gas of oxygen and argon from the gas inlet, and adjust the gas pressure to 1×10-1 to 1×.
Make it 10-3 tom. A high frequency voltage is applied to the cathode 2 by a high frequency power source 9. The target sample 4 is supplied with high frequency power of 2 to 1 OW/square per unit area. A piezoelectric crystal film of zinc oxide was actually created under the following sputtering conditions.

Mixed gas ratio; Argon: Oxygen = 9% by volume: 1% by volume
Pressure: 2×10 - frequency of high frequency power supply; 13
．． Sputtering was carried out under the above conditions, and the film quality and adhesion of the piezoelectric crystal film were examined. The results are shown in Table 1. .

As shown in Table 1, by containing glass, a piezoelectric crystal film with good film quality and good adhesion to the substrate can be obtained. The reason for the good adhesion between the substrate and the piezoelectric crystal film is thought to be that the glass component acts like an adhesive. Furthermore, when the relationship between the maximum input power that can be applied to each target sample and the sintered density was measured, the results were shown in FIG. 3.

The target sample has an average value of 2, and its variation is also shown in Figure 3. As can be seen from FIG. 3, the device according to the present invention has the effect that the maximum input power is more than twice that of the conventional device, the crystal film formation speed can be more than doubled, and mass productivity can be improved.

The glass powder used in the above examples was obtained by pulverizing glass within the vitrification range listed in Table 1.

In addition, in this invention, the range in which glass is contained in zinc oxide is 0.01 to 60. It is sufficient if it is within the shark weight % range.

In other words, if the glass content is less than 0.01% by weight, the bran feed density and specific resistance will not increase; If the amount exceeds 20% by weight, the resulting film will have poor autotropism. Furthermore, it is easily inferred that the same effect can be obtained even if the glass component is not only the above-mentioned crushed glass, but also the respective glass constituent elements can be added at the time of preparation etc. to achieve the composition of the glass component. Furthermore, similar effects can be obtained even if other glass components are included in addition to those in the above embodiments. Furthermore, since an alkali metal or the like that can increase the specific resistance of the target sample can be present as a glass powder, it can be easily incorporated into the zinc oxide porcelain. As described above, according to the present invention, a target can be obtained which has a lower sintering temperature than conventional targets, has a high density, and has small density variations within one target.

Further, it has the effect that a large maximum input power can be obtained, and a crystal film of good quality can be obtained with good mass production.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram for cutting out a sample for measuring sintered density from a target sample, Figure 2 is a high-frequency bipolar sputtering device, and Figure 3 is an illustration of the maximum input power that can be applied to the target sample and the sintered density. It is a figure showing a relationship. 1... Airtight container, 2... Cathode, 3...
...Anode, 4...Target, 6...
··substrate. Kagami Izu Festival 2nd Figure 3

Claims (1)

[Claims] 1 As a target for high frequency sputtering,
Zinc oxide-based porcelain for high-frequency sputtering, characterized by containing glass in zinc oxide.