JPH11298289A - Surface acoustic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an SAW(surface acoustic wave) device which prevents the generation of static electricity or pyroelectricity by preparing a short circuit thin line of a metallic thin film on the inside of a dicing line to surround the device and using plural thin lines to secure the electrical connection between the metallic thin film thin line and an IDT electrode. SOLUTION: A 2nd short circuit thin line 6 is formed by a metallic thin film on the inside of a 1st short circuit thin line 4. In regard to the line 6, the bus bars and the electrode fingers of IT electrodes 1 and 2 and reflectors 3a and 3b are connected to each other via thin lines 5a to 5d. Then the fingers of electrodes 1 and 2 of individual SAW device elements and the reflectors 3a and 3b are connected to the line 6 via the line 5a to 5d even after the line 6 is cut into the individual SAW device elements along its outside dicing line. Therefore, the distortions of the SAW devices or the pyroelectric charge that is caused by the temperature gradient are short-circuited by the line 6 and a SAW device is never broken by discharge.

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, and more particularly, to an ID generated when electric charges generated by a piezoelectric effect or a pyroelectric effect on a wafer are instantaneously discharged.
The present invention relates to a surface acoustic wave device that prevents destruction of a T electrode finger or the like.

[0002]

2. Description of the Related Art In recent years, surface acoustic wave devices (hereinafter, referred to as SAW devices) have been widely used in the field of communication and have excellent characteristics such as high performance, small size, and mass productivity, and thus are often used especially for mobile phones. Has been playing a part in its spread. FIG. 6A is a plan view showing a configuration of a longitudinally coupled dual mode SAW filter (hereinafter, referred to as a dual mode SAW filter) element which is an example of a conventional SAW device. As shown in FIG. 6A, a conventional dual mode SAW filter has two IDT electrodes 21 and 22 on the main surface of a piezoelectric substrate 26 along the propagation direction of a surface wave and grating reflectors 23a on both sides thereof. 23b (hereinafter, referred to as a reflector).

A dual mode SAW as shown in FIG.
The operation of the filter is, as is well known, the IDT electrodes 21, 2 and
Surface waves excited by the reflectors 2a and 2b
3b, acoustic coupling occurs between the IDT electrodes 21 and 22. As a result, the first and second longitudinal resonance modes are strongly excited, and these two modes are formed by appropriate termination. It operates as a dual mode SAW filter using the filter.

[0006] A schematic manufacturing process of the SAW device shown in FIG. 6 will be described. A wafer of a predetermined size composed of a piezoelectric substrate is sufficiently cleaned and dried by a cleaning device, and the wafer is subjected to aluminum alloying using a vapor deposition device or the like. Is deposited to form a metal thin film of an aluminum alloy. A thin resist film is uniformly applied on the metal thin film. Then, FIG.
As shown in the figure, an IDT electrode and a reflector, a short wire 24 made of a metal thin film on a dicing line surrounding the IDT electrode and a reflector, bus bars of the short wire 24 and the IDT electrodes 21 and 22, and reflectors 23a and 23b, respectively. A plurality of thin metal thin wires electrically connecting the bus bars or electrode fingers
The electrode pattern is exposed and developed using a glass mask on which the electrode pattern of No. 5 is drawn. Here, the dicing line is a boundary line for dividing a plurality of SAW devices formed on a wafer into individual pieces. The resist film other than the electrode pattern is stripped, an unnecessary aluminum film is removed by using an etching means, and the resist film on the electrode pattern is stripped to form a desired electrode pattern. At this time, the IDT electrodes 21 and 22, the reflector 23
By using a dicing machine to cut along the short wires 24 of the metal thin film formed simultaneously with the formation of the a and 23b, individual SAW device elements are obtained. In this cutting step, the short wire 24 on the dicing line is shaved and disappears, so that an individual SAW device having a configuration as shown in FIG. 6A is obtained. The reason why the short-circuited thin wire is employed in the manufacturing process will be described below.

For example, in a cleaning and drying process performed after etching an aluminum alloy film deposited on a piezoelectric substrate, moisture during the cleaning is dried by heat, but a temperature gradient is generated on the piezoelectric substrate. Therefore, pyroelectricity of the piezoelectric material generates a pyroelectric charge on the piezoelectric substrate. Further, in addition to the pyroelectric charge, when stress is applied to the piezoelectric substrate and distortion occurs inside the substrate, an electrostatic charge is generated on the substrate. In the absence of short-circuited wires, the pyroelectric or electrostatic charge sparks between the electrode fingers of the IDT electrode or the grating electrode, damaging the electrode and rendering it unusable, or altering the electrode film due to electrochemical reactions. Occurs. Therefore, the IDT electrode and the grating electrode are short-circuited by the short wires 24 and 25 to neutralize the electric charge, thereby preventing the IDT electrode fingers from being deteriorated or damaged due to a chemical change.

[0006]

However, in the above-described SAW device manufacturing process, the SAW device elements once separated from the wafer are combined with the IDT electrodes 21, 22 and the reflectors 23a, 23b as shown in FIG. Are separated from the short-circuit wire 24, their electrode fingers are not kept at the same potential. As a result, static electricity or pyroelectricity is generated due to external strain or non-uniform temperature distribution on the individual SAW device elements, and when the charges are instantaneously discharged, the IDT electrodes 21 and 22 and the reflector 23 are generated.
There is a problem that the electrode fingers a and 23b are damaged, and the characteristics of the SAW device element deteriorate. The present invention has been made to solve the above-described problem, and has as its object to provide a SAW device in which generation of static electricity or pyroelectricity is prevented.

[0007]

According to a first aspect of the present invention, there is provided a surface acoustic wave device comprising: an IDT electrode or a grating electrode on a piezoelectric substrate along a propagation direction of a surface acoustic wave; In the surface acoustic wave device configured by disposing, a short-circuit thin line of a metal thin film surrounding the periphery of the dicing line is provided inside the dicing line, and a plurality of thin wires for electrically connecting these thin metal thin wires and the IDT electrode are formed. The surface acoustic wave device is provided. The invention according to claim 2 is the surface acoustic wave device according to claim 1, wherein a part of the short-circuited thin line or the thin line is made narrower than another part to facilitate the fusing of the part. According to a third aspect of the present invention, there is provided the surface acoustic wave device according to the first or second aspect, wherein the short wire or a part of the short wire is replaced with a meander line.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the drawings. FIG. 1A is a plan view showing the configuration of an electrode pattern when a SAW device according to the present invention is manufactured, taking a dual mode SAW filter as an example, and FIG. FIG. 3 is a plan view showing an electrode pattern of a SAW filter. In the present invention, as shown in FIG. 1A, two IDT electrodes 1, 2 and reflectors 3a, 3b are arranged close to each other on the main surface of the piezoelectric substrate along the propagation direction of the surface acoustic wave. At the same time, a first short wire 4 is arranged on the dicing line,
And a plurality of fine wires 5c and 5d for electrically connecting the short-circuit fine wire 4 to the respective bus bars of the IDT electrodes 1 and 2, the bus bars of the reflectors 3a and 3b, or the electrode fingers.

Further, it is a feature of the present invention to form a second short-circuit wire 6 made of a metal thin film inside the first short-wire 4. The short wires 6 are connected to the respective bus bars and electrode fingers of the IDT electrodes 1 and 2 and the reflectors 3a and 3b by the thin wires 5a to 5d. These IDT electrodes 1,
2, reflectors 3a, 3b, dicing line 4, fine line 5a
5d and the short-circuit fine line 6 are simultaneously formed by the photo-etching means.

After cutting along the dicing line outside the short-circuited thin wire 6 and separating it into individual SAW device elements as shown in FIG.
Since the electrode fingers of the electrodes 1 and 2 and the reflectors 3a and 3b are connected to the short-circuit fine line 6 through a plurality of fine lines 5a to 5d,
The electrode fingers can be held at the same potential. Therefore, the strain applied to the SAW device element or the pyroelectric charge generated due to the temperature gradient is short-circuited by the short-circuit fine line 6 and is electrically neutralized, so that damage due to discharge does not occur.

However, as shown in FIG.
d, In the state where the input / output electrodes are short-circuited with each other or between the input / output electrodes and the ground by the short-circuited thin wires 6, they do not function as SAW device elements. Therefore, for example, after each element is mounted on a package, the thin wires 5a to 5d and the short-circuited thin wires 6 A part of the laser is blown by passing a laser or current. Since it is considered that the means for cutting using a laser does not require special explanation, the means for fusing the thin wires 5a to 5d and the short-circuit thin wire 6 by the current will be described. As shown in FIGS. 2 (a) and 2 (b), a part of the short-circuit wire 6 between the input / output electrodes (IDT1 and IDT2) or a part of the short-circuit wire 6 connecting the input / output electrodes IDT1 and IDT2 and the ground. May be provided with a wedge-shaped portion thinner than the line width of the other portion, or a wedge-shaped portion of the short-circuited thin wire 6 may be provided at the intersection of the thin wires 5a to 5d and the short-circuited thin wire 6, as shown in FIG. Is provided with a portion having a structure in which lines obtained by narrowing the widths of the thin wires 5a to 5d in a wedge shape are connected in a T shape.

As described above, a part of the thin wires 5a to 5d and the short-circuit thin wire 6 is provided with a wedge-shaped structure thinner than the line width of the other part, and then between the input / output electrodes and between the input / output electrodes and the ground. When a current is applied, the portion of the wedge-shaped structure between the thin wires 5a to 5d and the short-circuit wire 6 is larger than the resistance of the other portions, so that the portion is instantaneously heated and melted. And the ground is opened, and can function as a SAW device.

FIG. 3 shows another embodiment of the SAW device according to the present invention.
This is an example in which a meandering line 7 is used as a part of a short-circuited thin wire 6 arranged so as to surround the T electrodes 1 and 2 and the reflectors 3a and 3b. By providing the meander line 7 between the input electrode and the output electrode and between the input / output electrode and the ground, each electrode finger of the IDT electrodes 1 and 2 and the reflectors 3a and 3b is short-circuited in terms of direct current. , IDT electrodes 1 and 2 and reflector 3
The electrode fingers a and 3b have the same potential. In this short-circuited state, even if static charge or pyroelectric charge is generated by external stress or temperature gradient in the SAW device, the SAW device is electrically connected via the fine wires 5a to 5d and the short-circuit fine wire 6. Since the electrode fingers are neutralized, breakage of the electrode fingers can be significantly reduced. On the other hand, at a high frequency at which the SAW device operates, the meander line becomes an electrical inductance and S
Since the impedance of the high-frequency current handled by the AW device exhibits a high impedance, the portion where the meander line is inserted is electrically open.
Therefore, there is a feature that it is not necessary to cut the short-circuited thin wire or the meander line by laser or current after cutting into individual pieces. In addition, it is possible to check the quality of each SAW device element using a probe in a state of the wafer before dicing.

FIG. 4 is a plan view showing the structure of another embodiment of the SAW device according to the present invention, in which a double-mode SAW filter, a short wire 6 surrounding them, reflectors 3a and 3b are shown.
The configuration in which the thin wires 6a to 6d extending from the first wire 6a to 6d extend to the short wire 6 is the same as that in FIG. Also in this case, the meander line 7 is short-circuited in terms of direct current. Further, in terms of high frequency, since the meander line 7 presents a high impedance as described above, between the input / output electrodes or between the input / output electrodes and the ground approaches an open state, without cutting the short-circuit thin line or the meander line. A function as a device can be obtained, and individual SAW device characteristics can be checked by a probe in a state of a wafer to judge pass / fail. It is needless to say that a meandering line may be used as a part of the short-circuiting thin wire 6 and a meandering line may be used as the thin wires 5a to 5d connecting the short-circuiting thin wire 6 to an IDT electrode or the like. Nor.

FIG. 5 shows an embodiment in which a SAW device is applied to a dual mode SAW filter in which two stages are cascaded, and a short-circuit wire 6 for short-circuiting charges is provided inside a dicing line. In this case, the wiring pattern 8 for cascade connection between the dual mode SAW filters is formed wider than the fine wires 5a to 5d and the short-circuit fine wire 6 so as not to be blown by the current.

As described above, the present invention is applied to a dicing line for the first time.
Although the example in which the short-circuit thin line is formed has been described as an example, the first short-circuit thin line may be omitted if a second short-circuit thin line inside the dicing line is formed. Also, the present invention has been described by taking a dual mode SAW filter as an example. However, it is needless to say that the present invention can be applied to a SAW resonator, a longitudinally-coupled or laterally-coupled multi-mode SAW filter, a resonator-type SAW filter, a transversal-type filter, and the like. Nor.

[0017]

According to the present invention, as described above, the IDT electrode or the reflector due to the electric charge generated due to the external distortion or the temperature gradient in the process after being cut from the wafer by dicing is obtained. Damage to the electrode fingers was significantly reduced. Further, by providing a wedge-shaped structure on a part of the short-circuited thin wire or by forming a T-shaped wedge-shaped structure at the intersection of the short-circuited thin wire and the thin wire, the current can be easily blown by an electric current. There is no difference from the element. As described above, the use of the structure of the present invention has an excellent effect that the yield of SAW devices can be greatly improved.

[Brief description of the drawings]

FIG. 1A is a plan view showing a configuration of a SAW device according to the present invention, and FIG. 1B is a diagram showing an electrode pattern on a wafer.

FIG. 2 is an enlarged view of a wedge-shaped portion provided on a short-circuited thin wire or a part of the thin wire surrounding the device.

FIG. 3 is a plan view showing an electrode pattern according to another embodiment of the present invention.

FIG. 4 is a plan view showing an electrode pattern according to another embodiment of the present invention.

FIG. 5 is an embodiment in which the present invention is applied to a two-stage cascade-connected dual-mode SAW filter.

6A and 6B are diagrams illustrating an example of a conventional SAW device, in which FIG. 6A is a diagram illustrating an individual electrode pattern, and FIG. 6B is a diagram illustrating an electrode pattern on a wafer.

[Explanation of symbols]

 1, 2, IDT electrode 3a, 3b, grating reflector 4, dicing line 5a, 5b, 5c, 5d, thin line 6, short-circuited thin line 7, meander line 8, cascade connection wiring pattern

Claims (4)

[Claims] In a surface acoustic wave device having an IDT electrode or a grating electrode arranged on a piezoelectric substrate along a propagation direction of a surface acoustic wave, a short-circuited thin wire of a metal thin film surrounding the periphery of the device is provided inside a dicing line. A surface acoustic wave device comprising: a plurality of thin metal wires; and a plurality of thin wires for electrically connecting the metal thin film wires to the IDT electrode. 2. The surface acoustic wave device according to claim 1, wherein the short-circuited thin wire or a part of the thin wire is replaced with a meander line. 3. The surface acoustic wave device according to claim 1, wherein a required portion of the short-circuit wire is cut. 4. The surface acoustic wave device according to claim 3, wherein a part of the short-circuited thin line or the thin line is made narrower than another part to facilitate the fusing of the part.