JPH08154031A - Surface acoustic wave device - Google Patents

Abstract

PURPOSE: To provide a surface acoustic wave device by which the measurement of characteristics is stabilized and simplified. CONSTITUTION: This device is provided with interdigital electrodes 2 and 3 consisting of comb-like electrodes 2a and 3a at a signal side potential and comb-like electrodes 2b and 3b at a ground potential on the surface of a rectangular piezoelectric substrate 1. A common electrode film 5 to be connected with the respective electrodes 2b and 3b on the ground potential side is formed at one terminal side of the rectangular piezoelectrode substrate 1 at least, the ground potential is made common, and the number of contact positions of probes for ground potential are made one in the case of characteristic measurement.

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,
In particular, the present invention relates to a surface acoustic wave device excellent in checking characteristics.

[0002]

2. Description of the Related Art For example, a surface acoustic wave device has been used as a filter for a video signal of a video, as a filter for frequency conversion of a carrier signal of a communication device, and as a resonance element of a high frequency oscillation circuit of various electronic devices. .

The surface acoustic wave device generates surface acoustic waves on a piezoelectric ceramic substrate such as lead zirconate titanate or a piezoelectric single crystal substrate such as quartz, lithium tantalate, lithium niobate, or lithium tetraborate. In addition, various electrodes that excite surface acoustic waves and reflect surface acoustic waves are formed.

As an example of the electrode configuration of a typical filter, for example, a comb-teeth electrode on the signal side and a comb-teeth electrode on the ground side arranged to mesh with the comb-teeth electrode on the rectangular side are formed on a rectangular single crystal substrate of lithium tetraborate. The input side interdigital electrode, the ground electrode, and the output side interdigital electrode are arranged.

The method of manufacturing such a surface acoustic wave device is as follows.

First, a wafer of a piezoelectric material from which a plurality of mirror-finished elements can be extracted is prepared.

Next, various electrodes such as interdigital electrodes for performing excitation, transmission / reception, etc. are formed in each element region by a thin film technique such as aluminum.

Next, the characteristics are checked for each element region. At this time, each probe of the characteristic measuring device is brought into contact with a predetermined electrode, for example, the probe on the signal potential side is brought into contact with the input / output pad of the electrode on the signal side, and the probe on the ground potential side is brought into contact with the ground pad of the electrode on the ground side. To do. As a result, with respect to the element having the defective characteristic, marking indicating the defect is performed on the element region.

Next, along the boundary of each element, it is cut into individual elements by cutting with a diamond saw or the like.

Then, the defectively marked element is removed.

[0011]

In the conventional structure, when checking the characteristics of each element, there are interdigital electrodes on the input side and the output side which are composed of comb-teeth electrodes on the signal side and the ground side. Since there is a ground electrode and each electrode of each ground potential is dispersed, the probe of the characteristic measuring device prepares an input signal, an output signal, and three ground potentials. For example, the probe had to be brought into contact with the pad portion.

As a result, if even one of the plurality of probes has an unstable contact state, it is impossible to measure a reliable characteristic.

Moreover, in order to surely make contact with each element region on a wafer on which a plurality of element regions are arranged,
The contact alignment between the probe and the pad was difficult.

The present invention has been devised in view of the above-mentioned problems, and the purpose thereof is to make each electrode of the ground potential of each element common in the characteristic check, and to connect the probe of the ground potential to the wafer or the element. Thus, the reliability of characteristic measurement is improved by connecting the probe at one location so that the probe contacts substantially only for input and output on the signal side in the characteristic check.

[0015]

According to the present invention, an elastic surface is formed by arranging a plurality of interdigital electrodes each having a comb-teeth electrode having a signal side potential and a comb-teeth electrode having a ground potential on a surface of a rectangular piezoelectric substrate. In the wave device, a surface acoustic wave device in which a common ground electrode film connected to each electrode on the ground potential side is formed on at least one edge of the rectangular piezoelectric substrate.

[0016]

With the above structure, for example, in the case where one element is taken as an example, each electrode on the ground potential side is shared by the common ground electrode film. It is possible to connect all the electrodes of the ground potential of the device by simply contacting or connecting the probe of the ground potential of the characteristic measuring device. Therefore, in actual measurement, since only the probe on the signal potential side of the characteristic measuring device is operated, the number of probes to be operated is reduced, the positioning is facilitated, and the contact reliability can be improved.

Further, in particular, the ground electrode film is formed on at least one edge of the substrate of the piezoelectric substrate, that is, the cutting line portion. Therefore, in the wafer state, the common ground electrode films are connected to each other. Therefore, when performing the characteristic check on all the elements on the wafer, the probe of the ground potential of the characteristic measuring apparatus uses the common ground electrode film of any arbitrary value. Only one place needs to be connected to the position, and when actually checking the characteristics,
All you have to do is manipulate the input and output plobs.

Further, since the common ground electrode film is formed on the edge of the piezoelectric substrate and the cutting line of the wafer, the saw can be prevented from being displaced in the cutting process.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The surface acoustic wave device of the present invention will be described below with reference to the drawings.

FIG. 1 is an external perspective view of a surface acoustic wave device, and FIG. 2 is a plan view showing a part of a wafer in which a plurality of elements are arranged.

Reference numeral 1 is a piezoelectric substrate, 2 is an input side interdigital electrode, 3 is an output side interdigital electrode, and 4 is a ground electrode.

The piezoelectric substrate 1 is a piezoelectric ceramic substrate such as lead zirconate titanate, quartz, lithium tantalate, or the like.
A piezoelectric single crystal substrate such as lithium niobate or lithium tetraborate can be exemplified. The piezoelectric substrate is subjected to a polarization treatment (in the case of a ceramic substrate) or a predetermined cut treatment (in the case of a single crystal substrate) so that an elastic wave is generated.

The interdigital electrodes 2 and 3 and the ground electrode 4 are formed of a metal material such as aluminum or Au in a predetermined shape and a predetermined thickness by a thin film technique such as sputtering. In particular, the interdigital electrode 2
Comprises a comb-teeth electrode 2a having a signal potential and a comb-teeth electrode 2b having a ground potential so as to mesh with the comb-teeth electrode 2a. The interdigital electrode 3 on the output side is also composed of comb-teeth electrodes 3a and 3b.

The predetermined shape means, in particular, the pitch of adjacent comb-teeth electrodes 2a, 2b, 3a and 3b of interdigital electrodes 2 and 3, the number of pairs of adjacent comb-teeth electrodes 2a, 2b, 3a and 3b, and others. Its thickness, interdigital electrode 2,
The distance between the electrode 3 and the ground electrode 4 is also controlled to a predetermined value according to the characteristics. For example, the adjacent comb-teeth electrodes 2a, 2
The pitch of b, 3a and 3b is set so as to correspond to a quarter wavelength λ of the elastic wave generated on the piezoelectric substrate 1, and the logarithm and thickness of the adjacent comb tooth electrodes 2a, 2b, 3a and 3b are , Controls the excitation intensity by elastic waves due to the electromechanical coupling coefficient of the piezoelectric material.

A part of the signal-side comb-teeth electrode 2a of the input-side interdigital electrode 2 and the signal-side comb-teeth electrode 3a of the output-side interdigital electrode 3 has a connection pad 21a connected to an external circuit. , 31a are formed.

A characteristic of the present invention is that the common ground electrode film 5 is formed on at least one of the four sides of the rectangular piezoelectric substrate 1, that is, on the four sides in FIG. is there.

The interdigital electrode 2 on the input side
Ground potential side comb tooth electrode 2b, output side interdigital electrode 3 ground potential comb tooth electrode 3b, ground electrode 4
Are drawn out to the common ground electrode film 5 and the conductor film 21b,
It is electrically connected via 31b and 41. Also,
A connection pad 42 for ground potential that is connected to an external circuit is formed on a part of the lead conductor film 21b.

The surface acoustic wave device having the above-mentioned structure is made from a wafer large enough to extract a plurality of devices (elements).

The wafer is cut out from an ingot having a diameter of 3 inches formed by, for example, pulling up the above-mentioned piezoelectric single crystal to a predetermined cutting angle so as to have a predetermined cutting angle, and further mirror-finished. Further, it may be a rectangular wafer. Further, in the case of a ceramic material, a polarized material is used.

Next, corresponding to each element region, by the thin film technology, the input / output interdigital electrodes 2, 3, the ground electrode 4, the lead conductor films 21b, 31b, 41, the common ground electrode film 5, and the connection pad. 21a, 22b and 42 are formed.

The thin film technology is, for example, a metal film which is an electrode material such as aluminum or Au is deposited on a wafer by sputtering or the like, and then an etching resist is applied and formed, which is unnecessary depending on the shape of the electrode. The metal film on the part is etched, and the resist film is removed and washed.

Further, a resist film having openings corresponding to the shape of the electrodes is formed on the wafer, and aluminum,
After depositing a metal film such as Au as an electrode material,
It is formed by peeling and cleaning the resist.

At this time, the common ground electrode film 50 formed on the wafer 10 is formed vertically and horizontally so as to partition each element region as shown in FIG. 2, and a solid conductor is formed outside the element region. It is formed on the film 51. That is, the common ground electrode film 50 formed vertically and horizontally so as to partition each element region is connected to the solid conductor film 51.

Next, the characteristics of each element are checked. Specifically, the solid conductor film 51 on the outer peripheral side of the wafer 10 is brought into contact with or connected to a ground potential probe of a measuring device for characteristic measurement, and the interdigital electrodes 2, 3 on the input / output side of each element region are connected. Connection pads 21a, 31a of
In addition, the input probe on the signal side of the measuring device for characteristic measurement,
The output probe is contacted and the characteristics are measured. When measuring the characteristics of other element regions arranged on the wafer 10, only the input probe and the output probe on the signal side of the measuring device for characteristic measurement are interdigital on the input and output sides of the other element regions. Connection pads 21a, 31 of electrodes 2, 3
The characteristics are checked for all elements by moving and contacting with a. As a result, the element whose characteristic is not sufficiently satisfied is marked with a mark indicating that the characteristic is defective.

It should be noted that a plurality of input probes and output probes on the signal side of the characteristic measuring device are arranged in a row corresponding to all element regions arranged on the wafer 10, and the characteristics are measured collectively or sequentially. I don't mind.

In any case, each electrode (comb-teeth electrode) at the ground potential of each element is connected to the common ground electrode film 50 electrically connected to the solid conductor film 51 formed on the outer peripheral portion of the wafer 10. Since the movement and contact of the ground potential for the probing on each element area is omitted, the contact area between the element and the probe is reduced, the contact reliability is improved, and the probe for the characteristic check is used. Since the number is reduced, quick and reliable operation becomes possible.

Next, each element is cut from the wafer. Specifically, the dotted line shown in FIG. 2, that is, the common ground electrode film 50.
Along the line, cut with a dicing saw or the like.

In this cutting step, since the common ground electrode film 50 is formed vertically and horizontally so as to partition each element region, it is possible to easily visually confirm the displacement of the dicing position, and the displacement of the dicing position can be confirmed. It can be easily corrected and the cutting reliability will be greatly improved.

Finally, in the characteristic checking step, the surface acoustic wave device having excellent characteristics can be obtained by excluding and selecting the elements provided with the defective marking.

Here, the common ground electrode film 5 formed on at least one end side of the rectangular piezoelectric substrate 1 of the surface acoustic wave device of the present invention is a part of the common ground electrode film 50 formed on the wafer 10. Yes, for example, when dicing is cut at the central portion of the common ground electrode film 50, as a result, it is formed on each of the four edges of the rectangular piezoelectric substrate 1, and, for example, on one side of the common ground electrode film 50. When cut along the edge, a part of the common ground electrode film 50 may not be formed on a certain edge, or may enter the center from the edge. The common ground electrode film 5 may be in an intermittent state, but this is all included.

In the above-described embodiment, the measuring pads are brought into contact with each other by utilizing the connection pads 21a and 31a formed on the comb-shaped electrodes 2a and 3a on the signal side of the interdigital electrodes 2 and 3 on the input and output sides. However, a connection pad for a probe connected to the comb-teeth electrodes 2a, 3a may be separately provided at a position that does not affect the propagation of elastic waves.

Further, the structure of each electrode can be variously changed according to various uses. For example, in the case of a resonator type filter, an interdigital electrode on the input / output side is provided at the center of the piezoelectric substrate in the propagation direction of the elastic wave. And the interdigital electrodes on the input and output sides are sandwiched in the propagation direction of the elastic wave so that the interdigital electrodes are formed.

[0043]

As described above, according to the present invention, the common ground conductor film is formed on the edge of the rectangular piezoelectric substrate, and the common ground electrode film is connected to each electrode / comb-tooth electrode which is at ground potential. Therefore, in the characteristic check, the ground potential probe of the characteristic measuring device can be used in common, so the number of probes targeted for operation is substantially reduced, the contact reliability of the probe is improved, and accurate characteristics are ensured. Can measure stably.

The characteristic check is measured for each element formed on the wafer. However, since a plurality of elements formed on the wafer are commonly connected by the common ground electrode film, the characteristic check is substantially performed. Since only the probe on the signal side is operated, the characteristic measurement process is greatly simplified.

[Brief description of drawings]

FIG. 1 is an external perspective view of a surface acoustic wave device of the present invention.

FIG. 2 is a partial plan view of a wafer state.

[Explanation of supplements]

 DESCRIPTION OF SYMBOLS 1 ... Piezoelectric substrate 10 ... Wafer 2 ... Input side interdigital electrode 2a ... Comb-shaped electrode 21a of signal potential ... Connection pad 2b ... Comb-shaped electrode 21b of ground potential ... Lead-out conductor film 3 ... Output side interdigital electrode 3a ... Comb-shaped electrode 31a of signal potential ... Connection pad 3b ... Comb-shaped electrode 31b of earth potential ... Lead conductor film 4 ... Ground electrode 41 ... Lead conductor Membrane 5, 50 ... Common earth electrode membrane

Claims (1)

[Claims] 1. A surface acoustic wave device comprising an interdigital electrode composed of a comb-teeth electrode having a signal-side potential and a comb-teeth electrode having a ground potential on a surface of a rectangular piezoelectric substrate. A surface acoustic wave device comprising a piezoelectric substrate and a common ground electrode film connected to a comb-teeth electrode on the ground potential side formed on at least one end of the piezoelectric substrate.