JPH0280924A - Apparatus for measuring propagation velocity of surface wave - Google Patents

Abstract

PURPOSE:To certainly detect the propagation velocity of the surface wave propagating through the surface part of a sample by detecting interference frequency from the outputs of two receiving piezoelectric transducers. CONSTITUTION:The bulk wave generated in a transmitting transducer 16 is emitted into water by the transmitting acoustic lens part12 of the acoustic lens 15 opposed to said transducer 16. Since this bulk wave is refracted within a predetermined angle range containing the Rayleigh's critical angle of a sumple 22 by the transmitting acoustic lens part 12, the sonic wave coinciding with the Rayleigh's critical angle of the sample 22 in the bulk wave emitted into water is propagated on the same 22 as a surface wave by the lens part 12. The leak wave of this surface wave is received by the first and second receiving acoustic lens parts 13, 14 to reach receiving piezoelectric transducers 17, 18 and only the surface wave incident in a vertical direction in said leak wave is detected. From the interference frequency of the signals of two waves and the pitches of the receiving acoustic lenses 13, 14, the propagation velocity of the surface wave can be detected.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a surface wave propagation velocity measuring device used for measuring the propagation velocity of a surface wave propagating through a sample such as a substrate used in a surface acoustic wave device. Regarding.

[Prior Art] In general, surface wave devices directly utilize the propagation of surface waves propagating on the surface of a substrate such as alkali-free glass, so the surface wave propagation speed of the substrate material greatly affects the characteristics of the device. . Therefore, when manufacturing a surface acoustic wave device, if the surface wave propagation velocity of the processed surface of the substrate can be known, processing can be performed in accordance with the surface wave propagation velocity.

For this reason, measurement of the propagation velocity of surface waves has been conventionally performed. An example of a conventional surface wave propagation velocity measuring device is shown in the fourth section.
As shown in the figure.

The above device forms an interdigital electrode 2 for one-phase wave transmission on one main surface of - piezoelectric substrates 1, and
Two sets of interdigital electrodes 3 and 4 for receiving waves are formed with an interval ρ. The piezoelectric substrate 1 is placed parallel to the surface of the sample 5 whose surface wave propagation velocity is to be measured, with water 6 interposed therebetween. In this state, ultrasonic waves are emitted from the wave transmitting interdigital electrode 2 to the surface of the sample 5 as indicated by arrow A1. When the angle of incidence of this ultrasonic wave on the sample 5 is equal to the Lely critical angle OL, a surface wave is generated on the surface of the sample 5 by the ultrasonic wave.

This surface wave moves the surface of the sample 5 along the arrow A in FIG.
t, propagates as shown in A3. The above-mentioned surface wave is shown by arrow A 4 in FIG. 4 during its propagation.

It leaks as shown by A, and enters the interdigital electrodes 3 and 4 for wave reception, respectively. This interdigital electrode 3.4 detects the leakage elastic wave and calculates its interference frequency △f.
and the interval Q between the wave receiving interdigital electrodes 3.4, the surface wave propagation velocity V propagating on the surface of the sample 5 can be determined from the following equation (1).

ν=Q・△f ・・・・・・(l:) [Problem to be solved by the invention] By the way, in the above-mentioned conventional device, since the Lely critical angle θI7 differs between trials 1'-1 and 5, the transmission The radiation angle Oa of the ultrasonic wave emitted from the wave interdigital electrode 2 is not necessarily equal to the Ley critical angle OL of the sample 5, and the radiation angle θa is to some extent close to the Ley critical angle OL. If the distance is not close, there is a problem that surface waves will not be generated in the sample 5.

In addition, in the conventional device described above, since there is water for coupling between the piezoelectric substrate 1 and the sample 5, there is a problem that the interdigital electrodes 2 to 4 come into contact with this water 1.2 and corrode. .

Furthermore, the above-mentioned conventional device has a problem in that the efficiency of converting water from the interdigital electrode 2 for transmission into a bulk wave and the conversion from a bulk wave to a surface wave at the substrate 5 is low, and an amplifier or the like is required. Ta.

The purpose of the present invention is to reliably generate ultrasonic waves with a radiation angle equal to the Lely critical angle of the sample, to avoid corrosion of the electrodes due to coupling water, and to improve the conversion efficiency between surface waves and bulk waves. An object of the present invention is to provide a high surface wave propagation velocity measurement device.

[Means for Solving the Problems] Therefore, in the present invention, a sound wave that is incident on the sample surface from the Rayleigh critical angle direction propagates on the sample surface t as a surface wave, and during the propagation of this surface wave, Leakage waves leaking in the Rayleigh critical angle direction are detected at two positions along the propagation direction of the surface waves at equal heights from the sample surface, and the surface wave propagation is determined from the interference frequency and the distance between the two positions. This is a surface wave propagation velocity measuring device for measuring velocity, which consists of a solid block and has a distance between it and the sample surface.1. 'Power=! On one side, which are arranged parallel to each other with the pull liquid in between, there is a transmitting acoustic lens section that makes the sound waves incident on the sample surface from the Rayleigh critical angle direction, and a second section that receives the leaky waves at the two positions, respectively. an acoustic lens comprising a first wave receiving acoustic lens section and a second wave receiving acoustic lens section, and is bonded to the other surface opposite to one surface of the acoustic lens facing the wave transmitting acoustic lens section. a piezoelectric transducer for wave transmission, a first piezoelectric transducer for wave reception bonded to the other surface marked J- of the acoustic lens opposite to the first acoustic lens unit for wave reception, and the second piezoelectric transducer for wave reception; and a second piezoelectric transducer for wave reception, which is bonded to the L mud surface of the acoustic lens opposite to the wave reception acoustic lens part, and these first and second piezoelectric transducers for wave reception It is characterized in that the interference frequency is detected from the output of the .

[Function] The bulk wave generated by the piezoelectric transducer for wave transmission is radiated into the water by the acoustic lens section of the acoustic lens facing it. The wave acoustic lens section refracts the sample within a predetermined angle range that includes the Lely critical angle. Therefore, among the bulk waves radiated into the water by the transmission acoustic lens section, the sound waves that match the Lely critical angle of the sample propagate as surface waves on the sample. The leakage waves of this surface wave are received by the first and second wave receiving acoustic lens sections and reach the wave receiving piezoelectric transducer, but only one wave incident in the vertical direction is detected. Ru. The propagation speed of the surface wave is detected from the interference frequency of the two signals and the pitch of the receiving acoustic lens.

[Effects of the Invention] According to the present invention, since an ultrasonic wave having a radiation angle equal to the Ley critical angle of the sample is always emitted from the transmitting acoustic lens portion of the acoustic lens, the surface wave is reliably transmitted to the sample. occurs,
Therefore, by detecting the leakage waves, it is possible to reliably detect the propagation speed of the surface waves propagating on the sample surface.

Further, according to the present invention, although the water for the couple comes into contact with the acoustic lens, the electrodes of the piezoelectric transducer do not come into contact with the water for the couple, so the problem of electrode corrosion is completely resolved.

Furthermore, according to the present invention, the bulk waves generated by the wave transmitting piezoelectric transducer are all radiated from the wave transmitting acoustic lens part of the acoustic lens and do not propagate to other parts of the acoustic lens, so that the bulk waves are not propagated to other parts of the acoustic lens. The generation efficiency of surface waves also increases.

[Example〕 Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a perspective view of an embodiment of the surface wave propagation velocity measuring device according to the present invention.

The above measuring device consists of a solid block 2 made of a material such as sapphire or glass, and on one surface of this solid block 11 are provided an acoustic lens section 12 for transmitting waves, and an acoustic lens section i3 for first and second receiving waves. and 14 in this order. And this acoustic lens 15
A wave transmitting piezoelectric transducer 16. is mounted on the other surface of the solid block 11. The first and second receiving piezoelectric transducers 17 and 18 are bonded. These piezoelectric transducers l6,17.18 are made of ZnO# film, P
It is made of ZT ceramics etc.

The transmitting acoustic lens section 12, the first receiving acoustic lens section 13, and the second receiving acoustic lens section 14 of the acoustic lens 15 are all of a cylindrical type, for example. That is, the wave transmitting acoustic lens section 12 has a groove shape with a semicircular cross section formed on one surface of the solid block I+ of the acoustic lens 15, and crosses the one surface of the solid block 11. It is formed by The first wave receiving acoustic lens section 13 and the second wave receiving acoustic lens section 14 are also cylindrical shaped like the wave transmitting acoustic lens section 12, and extend across the one surface of the solid block It. and is arranged parallel to the wave transmitting acoustic lens section 12.

On the other hand, a common electrode 19 is formed on the other surface of the solid block 11 of the acoustic lens 15.
9, a piezoelectric transducer 16 for transmitting waves having an electrode 16a. ? 'IX first with poles 17a and 18a
and second wave receiving piezoelectric transducers 17 and 1
8 is glued. These piezoelectric transducers for wave transmission 1
6. First and second wave receiving piezoelectric transducers 17
and 18 are the wave transmitting acoustic lens section 12 . on the common electrode 19 . First and second wave receiving acoustic lens parts I
3 and 14, respectively.

As shown in FIG. 2, the above-described acoustic lens I5 includes the wave transmitting acoustic lens section 12. The first and second wave receiving acoustic lens sections 13 and 14 are arranged facing the sample 22 at a constant interval with the couple water 21 in between. And piezoelectric transducer 1 for wave transmission
6 is vibrated by applying a driving voltage between its electrode 16a and common electrode 19. The bulk waves generated by this vibration are radiated into the couple water 21 from the wave transmitting acoustic lens section 12 of the solid block 11 of the acoustic lens 15. A sound wave whose radiation angle θa matches the Lely critical angle θI of the sample 22 propagates as a surface wave on the surface of the sample 22 as shown by arrows A 1 I, A 12 and A13.

The leakage waves of the surface waves propagating on the surface of the sample 22 are
more radiated. This surface wave leakage wave is transmitted through the acoustic lens 15.
The first and second wave receiving acoustic lens sections 13 and 14 of
The wave is received by The leakage waves received by the first and second wave receiving acoustic lens sections 13 and 14 are detected whether they are only those that are perpendicularly incident on the first and second wave receiving piezoelectric transducers 17 and 18. . That is, the first and second wave receiving piezoelectric transducers 17 and +8
are arrows A+a and A+s from two points P and Q located on the surface of the sample 22 at an interval equal to the interval a, respectively.
As shown in , the Lely critical angle θ1. Detect surface waves leaking in the direction. Interference frequency signal of these two leaky waves △
The propagation velocity of the surface wave propagating on the surface of the sample 22 can be detected by calculating the above-mentioned equation (1) from the above distance a.

Sample 2 using the surface wave propagation velocity measuring device explained above
FIG. 3 shows an example of the system configuration of the surface wave propagation velocity measurement system described in Section 2.

A driving signal is supplied to the wave transmitting piezoelectric transducer I6 of the acoustic lens 15 from the output terminal OUT of the network analyzer 23 via the distributor 24. and,
The outputs of the first and second receiving piezoelectric transducers 17 and +8 are input to the input terminal of the amplifier 25, and the interference frequency Δr is detected. The output terminal of the amplifier 23 is connected to the input terminal B of the network analyzer 23. Then, the output of the network analyzer 23 is output to an arithmetic processing unit (not shown), and the propagation velocity of the surface wave is calculated using the above equation (1).

In this way, as can be seen from FIG. 2, when the wave transmission acoustic lens section 12 of the acoustic lens 15 is emitted into the water 21, the wave transmission piezoelectric transducer 16 emits the wave perpendicularly thereto. Since the bulk wave is refracted, there is always one whose radiation angle θa is equal to the Lely critical angle θL of the sample 22. This ensures that surface waves are generated in the sample 22.

Further, the acoustic lens 15 has a transmitting acoustic lens section 12.
．． First and second wave receiving acoustic lens sections 13 and 14
Since only that part is in contact with the couple water 21, the common electrode 19 and the wave transmitting piezoelectric transducer I
6 electrode 16a and the electrodes of the first and second wave receiving piezoelectric transducers I7 and 18! Corrosion of 7a and 18a does not occur.

Furthermore, in order to generate the surface waves of the sample 22, the piezoelectric transducer 16 for wave transmission generates bulk waves.
The generation efficiency of surface waves is also high.

[Brief explanation of the drawing]

1 is a perspective view of an embodiment of the surface wave propagation velocity measuring device according to the present invention; FIG. 2 is a vertical sectional view showing the surface wave propagation velocity measuring device of FIG. 1 placed on a sample; FIG. 3 is a system configuration diagram showing an example of a system for measuring the propagation velocity of a surface wave of a sample using the surface wave propagation velocity measuring device shown in FIG. 1, and FIG. 4 is an explanatory diagram of a conventional surface wave propagation velocity measuring device. +1...solid block, I2...acoustic lens section for wave transmission, 13...first acoustic lens section for wave reception, 14...second
Acoustic lens section for wave reception, 15...Acoustic lens, +6...Piezoelectric transducer for wave transmission, 17...First piezoelectric transducer for wave reception, 18-Second piezoelectric transducer for wave reception, 19 ...Common electrode, 21...
・Water, 22...sample. Patent Applicant: Sokoku Seisakusho Co., Ltd. Agent: Patent Attorney: Hajime Aoyama and 1 other person Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] (1) Sound waves incident on the sample surface from the Rayleigh critical angle direction propagate on the sample surface as surface waves, and during the propagation of the surface waves, leakage waves leak in the Rayleigh critical angle direction from the sample surface. Detection is made at two positions along the propagation direction of the surface waves at the same height, and the interference frequency and the above two positions are detected.
A surface wave propagation velocity measurement device that measures surface wave propagation velocity from the distance between positions, and is made of a solid block, one side of which is placed parallel to the sample surface with a coupling liquid interposed between them. The method further comprises: a transmitting acoustic lens section that causes sound waves to be incident on the sample surface from the Rayleigh critical angle direction; and first and second wave receiving acoustic lens sections that receive leakage waves at the two positions, respectively. a piezoelectric transducer for wave transmission, which is provided with an acoustic lens and is bonded to one surface of the acoustic lens opposite to the acoustic lens section for wave transmission, and the first acoustic transducer for wave reception; a first wave-receiving piezoelectric transducer bonded to the other surface of the acoustic lens facing the lens portion; and a first wave-receiving piezoelectric transducer bonded to the other surface of the acoustic lens facing the second wave-receiving acoustic lens portion. a second piezoelectric transducer for receiving waves, which is bonded to the first and second piezoelectric transducers;
A surface wave propagation velocity measuring device characterized in that the interference frequency is detected from the output of a wave receiving piezoelectric transducer.