JPH08340233A - Surface acoustic wave device - Google Patents

Abstract

PURPOSE: To obtain a highly reproducible and reliable electrode with high power resistance. CONSTITUTION: In a base film 2 consisting of a transition metal or its alloy M and an electrode 3 deposited on the film 2 and consisting of Al or Al-based alloy, the base film 2 consists of M-Si alloy obtained by adding 0.5 to 5weight% Si to the transition metal or metal M consisting of one or more kinds of transition metals. In the surface acoustic wave device having (111) orientation of Al or Al-based alloy, the film thickness of the M-Si alloy base film 2 is preferably controlled to 0.3 to 3nm in order to strongly orient the Al or Al-based alloy film deposited on base film 2 to (111).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave device.

[0002]

2. Description of the Related Art In surface acoustic wave devices used for mobile communication equipment, it is essential to improve the power resistance of the electrodes. Conventionally, it has been known that in order to improve the stress migration resistance of the electrode of the surface acoustic wave device, that is, the power resistance, it is effective to add a small amount of Cu or Ti to the electrode material or improve the crystallinity of the electrode film. Has been. For example, an Al electrode strongly oriented in (111) obtained by depositing it on a metal base film having a film thickness of about 1 nm has excellent power resistance. As disclosed in Japanese Patent Laid-Open No. 5-226337 and the like, it is possible to improve the migration resistance of the surface acoustic wave device electrode by improving the crystal orientation.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
(111) -oriented Al disclosed in Japanese Patent No. 90368
Although the electrode has improved power resistance, it is thin, but uses a metal other than Al for the base, so during electrode processing,
This underlying metal cannot be completely etched and remains as a residue. Since such an etching residue is a material having conductivity, it has a problem of causing a short circuit (short circuit) between electrodes.

Further, in Japanese Patent Laid-Open No. 5-226337, an amorphous or fine flow structure Al or Al alloy thin film is used as an underlayer of the thin film.
It has been reported that an Al or Al alloy thin film having a (111) orientation can be obtained. In the case of this structure, since the material of the electrode thin film and the underlying metal are made of the same Al or Al alloy, the problem of generation of etching residue due to the difference in material is eliminated, but the underlying layer is made amorphous or has a fine flow structure. In that it has to be formed,
There is a problem in that a large-scale device modification, an increase in work steps, an increase in work time, and the like are required, which takes time and effort in the creation process.

The present invention is intended to solve the above-mentioned drawbacks of the conventional example, and its purpose is to prevent the orientation of Al or an Al alloy from being deteriorated and to leave a residue with the same etching solution as Al. An object of the present invention is to provide a base metal film that can be etched, and to provide a surface acoustic wave device that has no short circuit between electrodes and is excellent in power resistance.

[0006]

As shown in FIG. 1, a surface acoustic wave device according to the present invention includes titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), cobalt (C).
o), nickel (Ni), copper (Cu), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), palladium (Pd), lanthanum (L)
a), hafnium (Hf), tantalum (Ta), tungsten (W), or any other transition metal, or an alloy composed of two or more of these, added with 0.5 to 5% by weight of Si. The formed alloy is used as a base film and Al
Alternatively, the surface acoustic wave device has a highly oriented Al electrode formed by depositing an Al-based alloy. Here, the film thickness of the Si-added alloy underlayer film is 0.1 to several nm in order to strongly orient the Al or Al-based alloy film deposited on it to (111).
It is desirable to be in the range of.

[0007]

The present inventors have discovered that in the case of a transition metal underlayer film of Cr, Ti, Cu or the like, if a trace amount of Si is added thereto, the underlying metal film can be etched without leaving a residue,
The present invention has been completed. In general, the transition metal used as the underlayer metal easily reacts with Si. Therefore, by adding a small amount of Si to the underlayer metal, the transition metal is changed into a state in which it can be easily etched even by an etching solution for Al or Al alloy film. It is considered to be a thing.

The film thickness of the Si-added alloy base film is 0.3 to
It is desirable to be in the range of several nm. Even if the thickness is thinner or thicker than this, the orientation of the Al or Al alloy film deposited thereon is deteriorated. Also, when the base film becomes thicker,
Even if the base film metal is more easily etched by the addition of Si, the base metal is less likely to be etched than Al or Al-based alloy. Therefore, when the base film becomes thick, the base metal is etched without leaving a residue. In order to achieve this, the etching time must be lengthened, and as a result,
Since the electrode width of Al or an Al-based alloy becomes small, it becomes difficult to manufacture a surface acoustic wave device having characteristics as designed. The metal underlayer of the present invention, to which 0.5 to 5% by weight of Si is added, has the effect as an underlayer, that is, the effect of highly orienting the Al or Al alloy film deposited on the metal underlayer is the film of the underlayer. If the thickness is in the above range,
There is no difference from the case where Si is not added. Also,
The amount of Si added affects the etching property of the underlayer film and the orientation of the Al or Al alloy film. If it is less than 0.5% by weight, etching residues occur, and if it is more than 5% by weight,
Not only is the orientation of Al or Al alloy deteriorated, but also Si produces etching residues, which is not preferable.

[0009]

EXAMPLES The present invention will be described below with reference to examples. In the following examples, the electrodes were manufactured by
It was manufactured by the ion beam sputtering method described in Japanese Patent No. 90268.

(Example 1) Cu-Si alloy target added with 0 to 8% by weight of Si and Al-0.5% by weight of Cu
An ion beam sputtering apparatus equipped with an alloy (hereinafter referred to as Al-0.5% Cu) target was used to form an Al-0.5% Cu film on the Cu-Si alloy base film by the ion beam sputtering method. A as an index of orientation degree by line diffraction
The rocking curve half-width of the l (111) peak was measured. Here, the film thicknesses of the base film and the Al-0.5% Cu alloy film were 0.4 nm and 100 nm, respectively. further,
Using these films, a 674 MHz surface acoustic wave filter was produced, and a scanning electron microscope (SEM) was used.
The presence or absence of a residue between the electrodes was examined in detail with 10 filters arbitrarily selected. The etching process was performed by immersing the substrate in a phosphoric acid (100%) solution at a temperature of 55 ° C.
Table 1 shows Al-0.5 formed on each base film.
The full width at half maximum of the Al (111) rocking curve of the% Cu film and the presence or absence of etching residue are shown. It can be seen that when the Si added to the Cu underlayer is in the range of 0.5 to 5% by weight, the orientation of the electrode film is not deteriorated and no etching residue is generated. In this embodiment, Al-0.5% Cu is used as Al or Al-based alloy formed on the base film.
Examples of alloys have been described, but pure Al, Al-2% C
u alloy, Al-1% Si-0.5% Cu alloy, Al-1
Similar results were obtained with the% Ti alloy and the Al-2% Pd alloy.

[0011]

[Table 1]

(Example 2) In Example 1, Cu-1.0 wt. % Si base film,
Cu-1.0 wt. 1% on the% Si base film
Depositing a 100 nm Al-1% Si-0.5% Cu alloy,
The rocking curve half width of Al (111) was measured.
As shown in Table 2, Cu-1.0 wt. When the thickness of the% Si base film is 0.1 to 1 nm, the Al-
It can be seen that the 1% Si-0.5% Cu alloy is highly oriented to (111).

[0013]

[Table 2]

Example 3 Titanium (Ti), vanadium (V), chromium (C
r), iron (Fe), cobalt (Co), nickel (N
i), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), palladium (P
d), lanthanum (La), hafnium (Hf), tantalum (Ta), and tungsten (W), the addition amount of Si and the Si-added transition metal underlayer film (film thickness: 0.
Al-2% Cu alloy film (film thickness 1
Rocking curve full width at half maximum of Al (111) peak at 00 nm) and after electrode processing (etching solution is at a temperature of 55
When the presence or absence of a residue of phosphoric acid (100% solution at 0 ° C.) was examined, almost the same results as in Example 1 were obtained.
That is, if the amount of Si added is within the range of 0.5 to 5% by weight, Al-2.0% C is obtained regardless of the type of transition metal.
It was found that the electrode processing without etching residue can be performed without lowering the orientation of the u film. In this embodiment, an Al-2% Cu alloy is used as the Al or Al-based alloy formed on the base film, but pure Al, Al-0.5% Cu alloy, Al-1% Si are used. -0.
Similar results were obtained with a 5% Cu alloy, an Al-1% Ti alloy, and an Al-2% Pd alloy.

(Example 4) 1 wt. % Of Si is added, the thickness of the transition metal underlayer of Example 3 is changed to 2
With respect to the electrode film on which a 100 nm Al-1% Ti alloy was deposited, the full width at half maximum of the rocking curve of the Al (111) peak and the presence or absence of etching residue were examined as in Example 1 or 3. In Table 3, 1 wt. The region of the underlayer film thickness where the Al-1% Ti film is highly oriented and the region of the underlayer film thickness where no etching residue of the underlayer film is left with respect to the transition metal underlayer film to which Si is added. Where Al (11
1) The case where the full width at half maximum of the rocking curve is 4.0 degrees or less was defined as high orientation. Further, regarding the presence or absence of etching residue, it was determined that there was no residue when one or less of the filters with etching residue was one or less out of 10 filters arbitrarily selected. Note that a phosphoric acid (100%) solution at a temperature of 55 ° C. was used for etching for electrode processing. As can be seen from Table 3, the Al-1% Ti film shows a high orientation and does not cause an etching residue. The film thickness of the transition metal underlayer film to which Si is added is in the range of 0.1 to several nm, although there are some differences depending on the type of transition metal.

[0016]

[Table 3]

(Embodiment 5) As a base metal, Ti, V,
Cr, Fe, Co, Ni, Cu, Y, Zr, Nb, M
When using an alloy composed of two or more kinds of transition metals selected from o, Pd, La, Hf, Ta, and W, Si
And the rocking curve of the Al (111) peak of the Al-2% Pd alloy film (film thickness is 100 nm) deposited on these Si-added transition metal alloy underlayer films (film thickness is 0.5 nm) When the full width at half maximum and the presence or absence of a residue after the electrode processing (the etching solution was a nitric acid (40%) solution at a temperature of 25 ° C.) were examined, almost the same results as in Example 1 or Example 3 were obtained. It was That is, if the amount of Si added is in the range of 0.5 to 5% by weight, the orientation of the Al-2% Pd film is not deteriorated regardless of the type of transition metal alloy, and there is no etching residue. It turned out that electrode processing is possible. In this embodiment, A formed on the base film
Although the example of Al-2% Pd alloy was described as l or Al-based alloy, pure Al, Al-0.5% Cu alloy, Al-2% Cu alloy, Al-1% Si-0.5%. C
Similar results were obtained with u alloy and Al-1% Ti alloy.

(Example 6) 1 wt. % Of Si is added, the thickness of the transition metal alloy underlayer is changed to 200 nm.
For the electrode film on which the Al-1% Ti alloy was deposited, the full width at half maximum of the rocking curve of the Al (111) peak and the presence or absence of etching residue were examined as in Example 4.
In Table 4, 1 wt. The region of the underlayer film thickness where the Al-1% Ti film is highly oriented and the region of the underlayer film thickness where no etching residue of the underlayer film is left with respect to the transition metal underlayer film to which Si is added. Here, high orientation means Al (111)
The full width at half maximum of the rocking curve was defined as 4.0 degrees or less.
In addition, for the presence or absence of etching residue, among the 10 filters selected arbitrarily, the filter with etching residue is 1
The case where the number was less than or equal to was determined to be no residue. A nitric acid (40%) solution at a temperature of 25 ° C. was used for etching for electrode processing. As can be seen from Table 3, the Al-1% Ti film exhibits a high orientation and does not cause an etching residue.
t. %, The film thickness of the transition metal underlayer with Si added is 0.1 to several
It is in the range of nm.

[0019]

[Table 4]

Although the surface acoustic wave device manufactured by the ion beam sputtering method has been described in the above embodiments, the manufacturing method of the electrode is not limited to the ion beam sputtering method, and the vapor deposition method or the ordinary sputtering method is used. Almost the same result was obtained in.

[0021]

As described above, Si of the present invention can be added to
Since the underlayer film of the transition metal or the alloy composed of them added by 5 to 5% by weight can be etched without lowering the orientation of Al or Al alloy and leaving no residue with the same etching solution as Al, It is possible to provide a surface acoustic wave device that has no short circuit between electrodes and is excellent in power resistance.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electrode film of the present invention.

[Explanation of symbols]

1 Substrate 2 Base metal film in which 0.5 to 5 wt% Si is added to transition metal 3 (111) oriented Al film

Claims (2)

[Claims] 1. An electrode composed of a base film and aluminum (Al) or an Al-based alloy deposited on the base film, wherein the base film comprises a metal M of 0.5 to 5% by weight of silicon (Si).
Is an M-Si alloy, the metal M is any one of transition metals, or an alloy composed of two or more thereof, and the Al or Al-based alloy has a (111) orientation. A surface acoustic wave device. 2. The thickness of the M-Si alloy base film is 0.3 to 3 nm.
The surface acoustic wave device according to claim 1, wherein