JPH1022764A - Saw device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the SAW device using an interdigital transducer(IDT) electrode capable of withstanding a large power application. SOLUTION: A high power resistance is obtained by forming an IDT electrode 2 comprising an aluminum alloy ternary or over formed by two kinds of additives as an additive A solved in grain of aluminum to form a solid solution at room temperature and an additive B depositted in the grain boundary of the aluminum at room temperature or forming an intermetallic compound with the aluminum at the boundary of the aluminum added in the aluminum at the same time onto a surface of a piezoelectric substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a SAW device, and more particularly, to a power durability of an IDT electrode of a SAW device.

[0002]

2. Description of the Related Art In a SAW device, an electrode made of an aluminum film is provided in a comb shape on a surface of a piezoelectric substrate, and an IDT is formed.
An electrode section is formed to constitute a filter and a resonator.

[0003] In recent years, with the increase in the frequency of mobile communication, SA
It is desired that the operating frequency of the W device be increased from several hundred MHz to several GHz and high output. Due to the high frequency, the pattern width of the IDT electrode must be reduced,
For a filter in the center frequency band of 1.5 GHz, the electrode width needs to be formed to be about 0.7 μm.

When a large power is applied to a SAW device having a fine line width as described above, a strain caused by a surface acoustic wave generates a stress in an electrode film. Aluminum atoms move through the crystal grain boundaries, and as a result, protrusions (hillocks) and voids (voids) are generated, causing electrode destruction, leading to deterioration of SAW device characteristics.

To solve such a problem, Japanese Patent Publication No.
As described in Japanese Patent No. 47010, an aluminum alloy film to which copper is added is used as an electrode material, and a material that can withstand higher power application than an aluminum single film has been manufactured. Also, in addition to copper, titanium, nickel, palladium, etc. are added to aluminum,
Binary alloys with a strengthened electrode film are also used to withstand higher power application than aluminum alone films.

[0006]

In the above prior art,
For use in the receiving stage of an antenna duplexer of a mobile phone, sufficient power durability has not been obtained against leakage of current from the transmitting stage. For example, in an analog cellular telephone, there is a wraparound of 1 W power in the band of the transmission stage of the filter of the reception stage, and it is necessary to withstand the application of this power.

An object of the present invention is to provide a SAW device using an IDT electrode that can withstand high power.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an IDT electrode provided on the surface of a piezoelectric substrate, which forms a solid solution with aluminum at a normal temperature by dissolving in aluminum agglomerates. From a ternary or more system in which two kinds of additives A and two kinds of additives B, which precipitate at an aluminum grain boundary at room temperature or form an intermetallic compound with aluminum at an aluminum grain boundary, are simultaneously added to aluminum. Aluminum alloy.

As a result, a SAW device that can withstand high power application can be obtained.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a surface acoustic wave device having a piezoelectric substrate and an IDT electrode provided on the piezoelectric substrate, wherein the IDT electrode is formed at room temperature with respect to aluminum. Additive A which forms a solid solution by forming a solid solution in aluminum agglomerates and additive B which precipitates at the aluminum grain boundary at room temperature or forms an intermetallic compound with aluminum at the aluminum grain boundary. Is added to aluminum at the same time, and the ternary system or more is added. By adding the additive A, the strength of the film is strengthened by the action of solid solution strengthening,
Further, the addition of the additive B has the effect of preventing aluminum from intergranular diffusion and consequently preventing the IDT electrode from deteriorating.

According to a second aspect of the present invention, any one of scandium, gallium, hafnium, zinc and magnesium is used as the additive A, and these materials are added to aluminum. Accordingly, at room temperature, these materials form a solid solution in the aluminum agglomerates, thereby having an effect of solid solution strengthening.

According to a third aspect of the present invention, any one of germanium, copper, and silicon is used as the additive B. By adding these materials to aluminum, these materials can be used at room temperature. The material precipitates at the grain boundaries of aluminum or forms intermetallic compounds,
It has the effect of suppressing the grain boundary diffusion of aluminum.

According to a fourth aspect of the present invention, the amount of the additive A, which forms a solid solution by dissolving in aluminum agglomerates with aluminum at room temperature, does not exceed the solid solubility limit of aluminum at room temperature. It has an effect of preventing an increase in the specific resistance of the film due to excessive addition and preventing the film from becoming brittle due to the formation of an intermetallic compound in the aluminum agglomerates.

According to a fifth aspect of the present invention, the amount of the additive B, which precipitates at the aluminum grain boundary or forms an intermetallic compound with aluminum at the aluminum grain boundary at room temperature, is 0.01% by weight to 10%. 0.0wt
%, It has the effect of defining the lower limit of the amount of additive that exhibits the effect of the additive B and preventing the deterioration of brittleness due to excessive formation of intermetallic compounds.

According to a sixth aspect of the present invention, an aluminum alloy film composed of three or more elements is formed and then heat-treated at a temperature of 200 ° C. or less. At the same time as preventing the additive A which forms a solid solution by forming a solid solution from being precipitated at the grain boundary and increasing the grain size of aluminum, It has an effect of sufficiently depositing the additive B which precipitates at the aluminum grain boundary or forms an intermetallic compound with aluminum at the aluminum grain boundary.

According to a seventh aspect of the present invention, the heat treatment is performed by SAW.
This is an alternative to the heating process during the device manufacturing process, which has the effect that the heat treatment process after film formation can be omitted.

Hereinafter, embodiments of the present invention will be described. (Embodiment 1) FIG. 1A is a perspective view showing the configuration of an 800 MHz band ladder type SAW filter created in the present embodiment. FIG. 1B is a diagram showing the configuration.
Reference numeral 1 denotes a piezoelectric substrate, and in the first embodiment, a lithium tantalum substrate (hereinafter, LT substrate) was used. 2 is an IDT electrode and 3 is a reflector electrode. FIG. 2 is a sectional view of the IDT electrode. The cross-sectional view shows only one IDT electrode.
In the first embodiment, scandium is added as an additive A which forms a solid solution by dissolving in aluminum agglomerates at room temperature with respect to aluminum. Germanium was used as an additive B forming an inter-compound. In the first embodiment, the SAW filter shown in FIG. 1 is formed as follows. The electrode film was formed by a sputtering method, and an alloy target was used as a target. The amount of scandium added in the target is 0.1.
1 wt%, and the amount of germanium added was 1.0 wt%. For comparison, an electrode film obtained by adding 1.0 wt% of copper to aluminum was also formed by the same method. Predetermined patterns were formed on the electrode films of these samples by photolithography and ion milling, and then die-bonded to a dicing and package substrate, and wire-bonded to form terminals.

The test sample was subjected to a power durability test by applying a power of 1 W in an atmosphere of 80 degrees. In the evaluation of the power durability, the point at which the filter characteristics deteriorated was regarded as the life of the device, and the value was normalized with respect to a film obtained by adding 1.0 wt% of copper to aluminum. The results are shown in (Table 1).

[0019]

[Table 1]

As can be seen from Table 1, SAW having a film obtained by adding 1.0 wt% of copper to aluminum was used as an electrode film.
Scandium on aluminum 0.1 against filter
The power durability of a SAW filter using a film containing 1 wt% and 1.0 wt% of germanium as an electrode film is improved by 100 times in terms of life. As described above, the additive A that forms a solid solution by dissolving into aluminum at a normal temperature to form a solid solution with respect to aluminum, and precipitates at the aluminum grain boundary or forms an intermetallic compound with aluminum at the aluminum grain boundary at normal temperature. It was confirmed that when an aluminum alloy in which two kinds of additives B were simultaneously added to aluminum was used as the electrode film, the power durability of the SAW device was greatly improved.

In the first embodiment, scandium is used as an additive A which forms a solid solution by forming a solid solution with aluminum at a normal temperature with respect to aluminum. However, gallium, hafnium, zinc and magnesium are used instead of scandium. It has been confirmed that the same effect can be obtained even when used. In addition, copper or silicon is used instead of germanium as an additive B that precipitates at the aluminum grain boundary at room temperature or forms an intermetallic compound with aluminum at the aluminum grain boundary. It has been confirmed that the same effect can be obtained by using.

(Embodiment 2) In this embodiment 2, scandium is added as an additive A which forms a solid solution by dissolving into aluminum agglomerates at room temperature with respect to aluminum, and precipitates at the aluminum grain boundaries at room temperature. Alternatively, germanium was used as an additive B that forms an intermetallic compound with aluminum at the aluminum grain boundary. In the second embodiment, the SAW filter shown in FIG. 1 is formed as follows. The electrode film is formed by a sputtering method,
An alloy target was used as a target. The addition amount of scandium in the target was 0.1 wt%, and the addition amount of germanium was 1.0 wt%. For comparison, an electrode film in which 1.0 wt% of copper was added to aluminum, and 1.0 wt% of germanium and 0.06 wt% were added to aluminum.
% Of scandium and an electrode film of aluminum with 1.0 wt% of germanium and 0.5 wt% of scandium added in the same manner. Predetermined patterns were formed on the electrode films of these samples by photolithography and ion milling, and then die-bonded to a dicing and package substrate, and wire-bonded.

The test sample was subjected to a power durability test by applying 1 W of power in an atmosphere of 80 degrees. In the evaluation of the power durability, the point at which the filter characteristics deteriorated was regarded as the life of the device, and the value was normalized with respect to a film obtained by adding 1.0 wt% of copper to aluminum. The results are shown in (Table 2).

[0024]

[Table 2]

As can be seen from Table 2, a SAW having a film obtained by adding 1.0 wt% of copper to aluminum was used as an electrode film.
Scandium on aluminum 0.1 against filter
The power durability of a SAW filter using a film containing 1.0 wt% of germanium and 1.0 wt% of germanium as an electrode film and a SAW filter using an electrode film containing 0.06 wt% of scandium and 1.0 wt% of germanium in aluminum as an electrode film are respectively shown. The former is about 100 times the life ratio, and the latter is about 60 times the life ratio.
It increases twice as much as the amount of scandium added. On the other hand, scandium 0.5
The power durability of a SAW filter using a film containing 1.0 wt% of germanium and 1.0 wt% of germanium as an electrode film is 30 times as large as that of a SAW filter using a film containing 1.0 wt% of copper added to aluminum and the amount of scandium added. However, the power durability has deteriorated in spite of the increase in power consumption. This is because the scandium was added in excess of the solubility limit of scandium to aluminum at room temperature, and excess scandium formed intermetallic compounds with aluminum in the aluminum agglomerates and the aluminum film became brittle. It seems to have worsened. As described above, the amount of the additive A, which forms a solid solution by dissolving into aluminum agglomerates at normal temperature with respect to aluminum, is most effective when it is within the solid solubility limit for aluminum at normal temperature. It was found that the power durability of the device was greatly improved.

In the second embodiment, scandium is used as an additive A which forms a solid solution by forming a solid solution with aluminum at a normal temperature with respect to aluminum. However, gallium, hafnium, zinc and magnesium are used instead of scandium. Also in the case of using, it is confirmed that the amount of addition is effective when it is within the solubility limit of aluminum of each additive at room temperature at room temperature, and has the same effect on the power durability.

(Embodiment 3) In this embodiment 3, scandium is added as an additive A which forms a solid solution by dissolving into aluminum agglomerates at room temperature with respect to aluminum, and precipitates at the aluminum grain boundaries at room temperature. Alternatively, copper was used as an additive B which forms an intermetallic compound with aluminum at the aluminum grain boundary. In the third embodiment, the SAW filter shown in FIG. 1 is formed as follows. The electrode film was formed by a sputtering method, and an alloy target was used as a target. The amount of scandium in the target was 0.1 wt%, and the amount of copper was 1.0 wt%.
%.

Further, after film formation, a sample subjected to a heat treatment at 150 ° C. for 1 hour, a sample subjected to a heat treatment at 200 ° C. for 1 hour, and 2
Four types of samples were prepared: a sample subjected to a heat treatment at 50 degrees for 1 hour and a sample subjected to a heat treatment at 350 degrees for 1 hour. For comparison, the same heat treatment was applied to aluminum by 1.0 wt%.
A sample was also made on the electrode film to which% copper was added. A predetermined pattern was formed on the electrode films of these samples by photolithography and dry etching, and thereafter, dicing and die bonding were performed on a package substrate, and wire bonding was performed. In the SAW filter forming process after the heat treatment, the process was performed in a low-temperature process in which the process temperature did not exceed 100 degrees.

The test sample was subjected to a power durability test by applying a power of 1 W to an out-of-band frequency in an atmosphere of 80 degrees. In the evaluation of the power durability, the point at which the filter characteristics deteriorated was regarded as the life of the device, and each sample was normalized with respect to the life of the sample that was not subjected to the heat treatment and displayed. The result is shown in FIG.

As can be seen from FIG.
In a device to which 1 wt% scandium and 1.0 wt% copper are added, the heat resistance is improved by performing the heat treatment up to about 300 ° C. for 1 hour as compared with the case where the heat treatment is not performed. On the other hand, the device subjected to the heat treatment at a temperature of 350 ° C. for one hour has the power resistance deteriorated. In addition, in a device in which 1.0 wt% copper is added to aluminum, there is a condition that the power durability is slightly improved as compared with the case where the heat treatment is not performed. However, the device subjected to the heat treatment generally has deteriorated power durability. I have. Observation of the particle size of the aluminum alloy film after heat treatment of these electrode films revealed that 0.1 wt% scandium was added to aluminum and 1.0 wt% to 1.0 wt%.
In the device to which wt% copper was added, the electrode film heat-treated at 250 ° C. or lower for 1 hour was almost the same as that of the electrode film not heat-treated, but the electrode film heat-treated at 350 ° C. The grain size of the aluminum alloy is larger than that of the electrode film not subjected to the heat treatment, and in the device in which 1.0 wt% of copper is added to aluminum, the electrode film subjected to the heat treatment as a whole is subjected to the heat treatment. Growing larger than that of the electrode film not performed was observed. It is generally known that in a SAW device, when heat treatment is performed after film formation, the particle size of aluminum increases and the power durability deteriorates. Additive B, which is prevented from increasing in diameter and supersaturated in the aluminum agglomerates during the film formation process, is sufficiently precipitated at the grain boundaries by heat treatment or aluminum and the intermetallic compound at the aluminum grain boundaries. And the effect of the additive B can be sufficiently obtained. Further, as a result of the experiment, it has been found that the heat treatment needs to be performed at a temperature of at least 120 ° C., and that the time for performing the heat treatment has an optimum time depending on the temperature of the heat treatment.

In the third embodiment, scandium is used as an additive A which forms a solid solution by dissolving in aluminum agglomerates at room temperature with respect to aluminum. However, gallium, hafnium, zinc and magnesium are used instead of scandium. The same heat treatment is effective when used, or when germanium or silicon is used instead of copper as an additive B which precipitates at the aluminum grain boundary at room temperature or forms an intermetallic compound with aluminum at the aluminum grain boundary. Make sure that. In addition, these heat treatment processes do not need to be performed as one independent step in the device manufacturing process.
It has also been confirmed that the above can be replaced by a heating step in the device manufacturing process.

[0032]

As described above, the present invention relates to an additive A which forms a solid solution by dissolving aluminum into agglomerates of aluminum at room temperature and forming a solid solution at room temperature with respect to aluminum. Forming an IDT electrode with an aluminum alloy consisting of a ternary or more system in which two kinds of additives B, which form an intermetallic compound with aluminum, are simultaneously added into aluminum, and subjecting to a heat treatment at 120 ° C. or more A SAW device that can withstand large power application can be manufactured with high reliability, and a large effect is achieved in that a filter at the top of the receiving stage of a mobile phone to which high power is applied and an oscillator used in a key entry system can be reliably manufactured. Having.

[Brief description of the drawings]

FIG. 1A is a perspective view showing a configuration of a SAW device created based on an embodiment of the present invention. FIG. 1B is a configuration diagram of the SAW device.

FIG. 2 is a cross-sectional configuration diagram of an IDT electrode showing an embodiment of the present invention.

FIG. 3 is a characteristic diagram of heat treatment temperature versus life in one embodiment of the present invention.

[Explanation of symbols]

1 piezoelectric substrate 2 interdigital transducer (IDT)
Electrode 4 Aluminum alloy film

Claims (7)

[Claims] A piezoelectric substrate and an interdigital transducer electrode (hereinafter referred to as ID) provided on the piezoelectric substrate.
A surface acoustic wave device having a T electrode).
Additive A that forms a solid solution by forming a solid solution with aluminum at room temperature as a DT electrode at room temperature
And a ternary or more aluminum alloy in which two kinds of additives B, which precipitate at an aluminum grain boundary at room temperature or form an intermetallic compound with aluminum at the aluminum grain boundary, are simultaneously added into aluminum. SAW device. 2. The SAW device according to claim 1, wherein said additive A is any one of scandium, gallium, hafnium, zinc, and magnesium. 3. The SAW device according to claim 1, wherein the additive B is any one of germanium, copper, and silicon. 4. The SAW device according to claim 1, wherein the amount of the additive A does not exceed the solubility limit of aluminum at room temperature. 5. The amount of the additive B is 0.01 wt%.
The SAW device according to claim 1, wherein the content is -10.0 wt%. 6. An additive A which forms a solid solution by being dissolved in aluminum agglomerates at room temperature with respect to aluminum as the IDT electrode and an additive which precipitates or forms an intermetallic compound at the aluminum grain boundary at room temperature. After forming an aluminum alloy film composed of a ternary system or more in which two kinds of additives of the product B are simultaneously added to aluminum,
A method for manufacturing a SAW device in which a heat treatment is performed at a temperature of 120 ° C. or higher. 7. The method of manufacturing a SAW device according to claim 7, wherein the heat treatment is replaced by a heating process during a manufacturing process of the SAW device.