JPH10190389A - Saw filter and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a short circuit between the electrodes of an IDT (interdigital electrode) and to improve reliability. SOLUTION: The photolithography process of a pattern for constituting a bonding pad or the like is executed on the ferroelectric substrate 11 of LiTaO3 or the like and an Au film 12 formed by vapor deposition or sputtering is patterned. Then, the photolithography process is executed so as to overlap at least a part of the bonding pad with the Au film 12 so as to secure conduction and an Al film 13 filmed by the vapor deposition or sputtering is patterned.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a SAW (Surf)
The present invention relates to an ace Acoustic Wave (surface acoustic wave) filter and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, techniques in such a field include:
For example, there are those described below. FIG. 3 is a plan view of such a conventional SAW filter, and FIG.
FIG. 4 is a cross-sectional view taken along a line A.

In these figures, reference numeral 1 denotes a ferroelectric substrate such as LiTaO ₃ , and 2 denotes an IDT (Inter Digit) made of an Al deposited film formed on the ferroelectric substrate 1.
alTransducer: IDT), 3 is an Au deposited film connected to the IDT.

[0004]

When an IDT 2 of a thin film Al is formed on a ferroelectric substrate 1 such as LiTaO ₃ and then a bonding pad pattern is formed by using an Au deposition film 3 for external connection, an Au deposition film is used. 3 may be performed. At this time, as shown in FIG. 5, the IDT 2 of the thin film Al is charged and the dust 4 of the Au deposited film is charged.
2 and short-circuit failure occurs between the electrodes.

[0005] Further, since the IDT is formed first, and then the bonding pads are formed, many irregularities are formed on the substrate surface when the bonding pads are formed, and metal chips are easily caught. SUMMARY OF THE INVENTION It is an object of the present invention to provide a highly reliable SAW filter and a method for manufacturing the same that eliminate the above-mentioned problems and eliminate short-circuits between electrodes of an IDT.

[0006]

In order to achieve the above object, the present invention provides: (1) In a SAW filter, a bonding pad formed on a ferroelectric substrate and a bonding pad connected to the bonding pad. The IDT to be formed is provided.

(2) In the SAW filter according to (1), the bonding pad is an Au thin film and the ID is
T is made of an Al thin film. (3) In the method of manufacturing a SAW filter, a step of forming a bonding pad made of an Au thin film on a ferroelectric substrate and a step of forming an IDT made of an Al thin film so as to be connected to the bonding pad are performed. It is intended to be applied.

[0008] With this configuration, according to the SAW filters described in the above (1) and (2), a short circuit between the electrodes of the IDT can be eliminated, and a highly reliable SAW filter can be provided. Further, the SAW described in the above (3)
According to the filter manufacturing method, the bonding pad portion of the Au thin film has a larger pattern than the IDT of the Al thin film, and the pattern is formed before the IDT portion of the Al thin film. Small and small surface area. Furthermore, since there are few irregularities, metal chips are not easily caught.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows the first embodiment of the present invention.
FIG. 2 is a plan view of a SAW filter showing an embodiment, and FIG.
FIG. 4 is a cross-sectional view taken along line B. As shown in these figures, LiT
A photolithography process is performed on a pattern constituting a bonding pad on a ferroelectric substrate 11 such as aO ₃ to pattern an Au film 12 formed by vapor deposition or sputtering.

Next, in order to secure conduction, a photolithography process is performed so that at least a part of the bonding pad overlaps the Au film 12, and the Al film 13 formed by vapor deposition or sputtering is patterned. Thus, first, Au
After the film 12 was patterned, the Al thin film was patterned by Al vapor deposition, so that the IDT of the thin film Al was charged and the dust 4 of the Au vapor deposited film was charged as in the conventional case.
It does not adhere to the DT2 and cause a short circuit between the electrodes.

The IDT of the SAW (surface acoustic wave) filter thus obtained is composed of an Al thin film.
The center is a frequency of 600 MHz to 1.5 GHz,
It is formed at a pitch of 0.8 to several microns. For this reason, even a minute dust greatly affects the characteristics. The substrate of the SAW filter is made of ferroelectric LiTa.
It is made of a material such as O ₃ , and in particular, static electricity is generated due to a temperature change or slight substrate deformation, and dust and metal chips at the time of lift-off adhere.

As described above, the pattern of the bonding pad portion of the Au thin film is larger than that of the IDT of the Al thin film.
Since the pattern is formed before the IDT portion of the thin film, there is no Al pattern, so there are few irregularities and the surface area is small. Furthermore, since there are few irregularities, metal chips are not easily caught. It should be noted that the present invention is not limited to the above embodiment, and various modifications can be made based on the gist of the present invention, and these are not excluded from the scope of the present invention.

[0013]

As described above, according to the present invention, the following effects can be obtained. (A) According to the first and second aspects of the invention, it is possible to provide a highly reliable SAW filter by eliminating a short circuit between electrodes of an IDT.

(B) According to the third aspect of the invention, Au
The pattern of the bonding pad portion of the thin film is larger than that of the IDT of the Al thin film, and the pattern is formed before the IDT portion of the Al thin film. Furthermore, since there are few irregularities, metal chips are not easily caught.

[Brief description of the drawings]

FIG. 1 is a plan view of a SAW filter according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line BB of FIG.

FIG. 3 is a plan view of a conventional SAW filter.

FIG. 4 is a sectional view taken along line AA of FIG. 3;

FIG. 5 is an explanatory diagram of a problem of the related art.

[Explanation of symbols]

 Reference Signs List 11 ferroelectric substrate 12 Au film 13 Al film

Claims (3)

[Claims] 1. A SAW filter comprising: (a) a bonding pad formed on a ferroelectric substrate; and (b) an IDT formed to be connected to the bonding pad. 2. The SAW filter according to claim 1, wherein said bonding pad is made of an Au thin film, and said IDT is made of an Al thin film. 3. A step of depositing a bonding pad made of an Au thin film on a ferroelectric substrate, and (b) an I layer made of an Al thin film so as to be connected to the bonding pad.
And a step of forming a DT.