JPS58179011A - Surface acoustic wave device - Google Patents

Abstract

PURPOSE:To ensure the workng of a surface acoustic wave device over a wide range of frequencies, by providing a lead-out electrode along the surface of a piezoelectric film formed on a non-piezoelectric substrate. CONSTITUTION:Electrodes 14A, 14B and 14C having phases of 0 deg., 120 deg. and 240 deg. respetively are formed on the surface of a non-piezoelectric substrate 13 of silicon, etc. Then lead-out electrodes 15B and 15C are provided on the substrate 13 in correspondence to electrodes 14B and 14C respectively. A piezoelectric film 16 is formed as if it covered over electrodes 14A and 14B. A lead-out electrode 15A is provided along the film 16. Then feed terminals 17A, 17B and 17C are provided in response to electrodes 15A, 15B and 15C respectively. The electric signals of three phases are applied to electrodes 14A, 14B and 14C of three phases of a transducer via terminals 17A, 17B and 17C respectively. Thus the working is ensured over a wide range of frequencies for a surface acoustic wave device.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a surface acoustic wave device 1ILVc using a unidirectional transducer that enables the ignition of the Kosojo characteristic.
It is related to

Waves that propagate with concentrated energy in the flat surface pressure oil of an elastic body, so-called surface acoustic waves, are superior in terms of softness compared to conventionally used bulk waves. It is now being used as a surface acoustic wave device for various electronic components such as the filter Y. FIG. 1 shows a filter as an example, in which 1 is a piezoelectric substrate, 2 is an input trannuducer consisting of a pair of interdigital electrodes 3A and 3B, and 4 is a pair of interdigital electrodes 5A.

Output transducer consisting of 5B, input terminal IN
The signal applied from the human power transducer 2 is converted into a surface acoustic wave, which propagates along the surface Y of the elastic substrate 1 as shown by the arrow and reaches the output transducer 4. The signal is converted into a signal and taken out from the output terminal OUT.

By the way, in the case of a filter in which a pair of -C barb-shaped electrodes 3A, 3B and 5A, 5B are each arranged with a Shikishi 21 Koji transducer 2.4, as in the surface wave device made by Sozo in FIG. These transducers 2.4 propagate waves in both left and right directions.''5K III
Electricity for I<! I-mechanical exchange loss is unavoidable, and there is a drawback that the loss increases as a filter.

In order to eliminate this drawback, a so-called unidirectional transducer has been proposed which is devised to allow surface wave sound to propagate only on one 7 iF# of the surface of a piezoelectric substrate. The specific configuration of this unidirectional transducer is as shown in Figure 2.
0' phase shifter! A method using a 90° S phase bv, and a method using a reflective Fi mirror as shown in Figure #143 are known.

Figure 2 vch c6, 6A, 6B are y each other vclzc
In electrical connection with a phase difference of f, the second electrode 6 is connected to the other electrode 6A at Ikl[! M gap? Alternatively, an insulating layer may be interposed so that the front Ifl wave propagates in only one direction.

However, this method of using a phase shifter has the disadvantage that the manufacturing process is complicated because it is necessary to provide the electrodes with a cross section as described above.

On the other hand, in FIG. 3, 8A and 8B are a power supply part and a reflection part provided to constitute part of the interdigital electrode, and both are made of regular electrodes, and 9 is a 8A,
88 is a common pole, lO is a signal source, 11 is a matching circuit, and a hill actance circuit. In the above, the signal applied from the signal source W via the matching circuit 111' is converted into an elastic surface th wave from the power supply 1118A and propagated in both left and right directions. At this time, the surface wave propagated to the left is reflected by the reflection section 88 connected to the reactance circuit 12Y and returned to the right direction, and the surface wave propagated to the right at the power feeding section 8AiIC and the reflected surface wave. Synthesis takes place. As a result, the same numbers of centers jllll in the table wave overlap 1IIIIII&, but the center JliII
IIl! If it deviates from this, both waves will act to cancel each other out (the 'lk plane wave will propagate in the opposite direction to the desired direction. Therefore, Table FhIl
There is a drawback that the propagation characteristics of l are limited to narrow band characteristics.

The present invention has been made to address the above-mentioned problems, and includes 0°, Iz6 and 24♂ made on a non-piezoelectric substrate.
One of the three extraction electrodes to be connected to each of the three electrodes having a phase difference of Elastic IiI equipped with transshu sun! It is the object of the present invention to provide a second aspect of the present invention and an apparatus. The present invention will be described in detail below with reference to the drawings.

41st! ! And FIG. 5 shows the elasticity according to the embodiment of the present invention! l
l! A schematic top view and a schematic cross-sectional view showing a plane IIL device, in which O', O',
6 turtle j1 with three phases of 120' and z4cr
4A, 14B, and 14C are formed. For the electrodes 14B and 14CK of the above three-phase electric wire, a non-piezoelectric substrate 13 is provided correspondingly to the lead-out electric wire 1!
15B and 15C are connected to each.

In addition, a piezoelectric film 16 made of zinc oxide or the like is formed on the non-piezoelectric substrate 413 surface as shown in FIG.
An extraction voltage provided along the surface of this piezoelectric layer 16*
15A is connected to the above voltage value 14AK. Furthermore, each kK of the above tension t'1tiL electric m15A, 15H, 15C
For supplying each phase signal, a feeder cable 17A is provided for supplying each phase signal.
, 178.17C is distributed by wire bonding etc.

One method for fabricating the above structure is to first deposit all *kK uniform gold #4w vacuum evaporation on the opening of the non-piezoelectric substrate, and then remove the metal from the undesired parts using a photo-etching method. 14B of the above 3-phase power.

Only the pattern 140 and the extraction electrodes 15B and 15c are left in the pattern t, which is set to 5. a and each of these electrodes 14B.

14 CM YUx5B, 15CvttrlHE electrolytic group [13 Table 1+ (Piezoelectric film 16 is uniformly deposited. Then, an electric current 1i14A is applied onto the non-piezoelectric substrate RO and ionization 1
In order to configure the KiWl width between 4C and 14B (piezoelectric material ill 16 V, open a window in the necessary part).Furthermore, piezoelectric material film 16
By forming the outer surface of the non-piezoelectric substrate 13 where there is no electrode 14A, the electrode 14A is formed on the non-piezoelectric substrate 13 (and the extraction electrode 15A is formed along the surface of the piezoelectric film 16).

Next, each extraction electrode rs A, 15 B, 15
CK unreasonable money-1i! i! The power supply terminals 17A, 17B, 17 are connected by wire bonding method.
By forming C, the structure shown in FIG. 4 is obtained.

The three-phase electrode 14A of the above Il bottom transducer.

Power supply terminals 17A and 17B for each of 14B and 14c
, applying a 3-phase electrical signal via 17Cv is a wide -
It can be made to work as a unidirectional transducer over m*number m8tC.

Here, if silicon (8i)t' is used as the non-piezoelectric substrate B and zinc oxide (ZnO) is used as the piezoelectric film 16, an elastic **a* device Y can be formed on one substrate together with a semiconductor device. Therefore, it is possible to make efforts to accumulate and develop. A similar effect can be obtained by using a silicon substrate with an oxide film provided on its surface in advance.

As is clear from the above description, according to the present invention, the 39A '#L function formed on the non-piezoelectric substrate with phases of 0°, 120° and 240' should be connected to each of the Since one of the three extraction electrodes is provided along the surface of the piezoelectric film formed on the non-piezoelectric substrate, the unidirectional transducer is configured, so that the characteristics of can be realized.

Also, by applying conventional technology to the manufacturing method, 3
Since it is possible to form a phase signal electric camellia system Y, manufacturing costs can be reduced.

In addition, the manufacturing method shown in the practical column is the one given as an example Y,
Depending on the cost, you can add any chest construction equipment, change history, etc. V-5.

[Brief explanation of the drawing]

Figures IK1 to A13 are all schematic diagrams showing conventional N%, and Figures 4 and 5 are both a track top view and a schematic sectional view showing an embodiment of the present invention. 13'°・Non-piezoelectric substrate, 14A, 14B, 14C...
・3-phase electric cannon, 15A, 15B, 15c... - Extracting electrode, 16... Piezoelectric film, 17A, 17B, 17C...
・Power supply terminal. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. Non-pressure on the body&i Ko, 12c;m Yohiz4
Each electrode having a phase of f is formed, and one of the three extraction electrodes to be connected to each of these three electrodes is provided along the surface of the piezoelectric film formed on the non-piezoelectric substrate. What is claimed is: 1. An elastic wave device comprising: a transducer configured to perform a transducer. 2.41# that the lead-out electrodes for the remaining two electrodes are provided along the above-mentioned non-piezoelectric substrate. FtII demand range! The surface acoustic wave device according to item M1. 3. If the piezoelectric film is formed like the remaining two electrophonic layers 5, the elasticity Ii as set forth in claim 1 or 2 is v**! IiI wave device. 4. The surface acoustic wave device according to any one of the first to third tombs in the watch-ice range, wherein the non-piezoelectric substrate is made of silicon and the piezoelectric film is made of zinc oxide.