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JPH0415558

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DESCRIPTION JPH0415558
[0001]
A. Industrial Field of Application The present invention relates to an ultrasonic probe suitable for
use in an ultrasonic microscope, and in particular, an ultrasonic probe improved to facilitate
calculation of the sound field inside an acoustic lens. B. Prior Art FIG. 6 is a cross-sectional view
showing a conventional ultrasonic probe used in an ultrasonic microscope. In the figure,
reference numeral 1 denotes an ultrasonic probe, and the ultrasonic probe 1 is roughly
composed of an acoustic lens 2 and an ultrasonic wave generator 4 formed at one end 3 of the
acoustic lens 2. It is configured. The acoustic lens 2 is formed of a material having good
ultrasonic wave transmission performance, and one end 3 on which the ultrasonic wave
generator 4 is formed is formed on the flat surface 3a, and the other end is A concave lens
spherical portion (converging portion) 5 is formed at a position facing the sound wave generator
4. On the other hand, the ultrasonic wave generator 4 is a piezoelectric film (piezoelectric
element made of a piezoelectric material such as ZnO or the like formed on the lower electrode 6
formed on one end face 3 of the acoustic lens 2 and the lower electrode 6 ′ ′ in order. 7) and
two-part electrode 8 . -In order to prevent short circuit between the upper and lower
electrodes 8 and 6 in fishing, the upper electrode 8 is smaller in planar size than the piezoelectric
film 7, and the lower electrode 6 is planar than the piezoelectric film 7 The dimensions are large.
In the ultrasonic probe 1 configured as described above, when a pulse wave or burst wave
voltage is supplied between the upper electrode 8 and the lower electrode 6 from an oscillator
(not shown), the piezoelectric film 7 between the electrodes 6 and 8 is generated. Vibrates in the
film thickness direction, and an ultrasonic wave having a frequency substantially determined by
the film thickness and the launch frequency is emitted downward by "1". Among the ultrasonic
waves, the ultrasonic wave 9 propagating in the acoustic lens 2 is converged by the concave lens
spherical portion 5 formed at the other end of the lens 2 and emitted into the water W outside
the lens 2, It propagates in the water W and is emitted into the sample 10. The ultrasonic waves
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radiated into the sample 10 are reflected by different portions (for example, voids, cracks, etc.) of
the acoustic impedance on the surface or inside thereof, and a portion thereof is returned to the
piezoelectric film 7 through the acoustic lens 2 and this piezoelectric The vibration of the film 7
is received as a voltage between the upper electrode 8 and the lower electrode 6. This voltage is
detected by a receiver (not shown) to obtain surface information and internal information of the
sample 10. C9 Problem to be Solved by the Invention By the way, when designing an ultrasonic
probe used for the above-mentioned ultrasonic microscope, it is necessary to consider the sound
field inside the acoustic lens 2. Specifically, it is desirable that the sound field inside the lens 2
has a uniform amplitude, -like phase, or a Gaussian distribution (normal distribution) like
amplitude and phase.
Each of these sound fields can be obtained by theoretical calculation, but in order to do so, it is
necessary to know the dimensions of the sound source that actually generates ultrasonic waves.
However, in the conventional ultrasonic probe, the upper electrode 8. Since the planar
dimensions of the lower electrode 6 and the piezoelectric film 7 are all different, there is a
problem that it is difficult to estimate the dimensions of a sound source actually generating an
ultrasonic wave. The object of the present invention is to make it possible to estimate the planar
dimensions of the upper and lower electrodes and the piezoelectric element to substantially the
same dimensions, thereby facilitating sound field calculation, that is, a high-performance super
with desired characteristics. It is in providing a sound wave probe. The present invention will be
described with reference to the drawings which are one embodiment of the present invention.
The present invention relates to the piezoelectric element 7 and the piezoelectric element 7 at
one end 3 of the acoustic lens 2. An ultrasonic wave generator 4 having an upper electrode 8 and
a lower electrode 6 respectively provided on the lower surface is provided, and the ultrasonic
wave generator 4 generates an ultrasonic wave at the other end of the acoustic lens 2. The
present invention is applied to an ultrasonic probe provided with a focusing unit 5 for emitting
and focusing propagating ultrasonic waves. The dual purpose is to form the upper electrode 8
and the lower electrode 6 in such a manner that the planar dimensions thereof are larger than
that of the piezoelectric element 7 and have substantially the same diameter as each other and
the piezoelectric element 7 is not interposed. The insulating layer 11 is interposed between the
electrodes 6. Since the insulating layer 11 is interposed between the upper electrode 8 and the
lower electrode 6 in the portion where the 81 action piezoelectric element 7 is not interposed,
between the upper electrode 8 and the lower electrode 6 other than the portion where the
piezoelectric element 7 is interposed. Are electrically isolated by the insulating layer 11.
Therefore, the planar dimensions of the 1-part electrode 8 and the lower electrode 8 can be
made larger than those of the piezoelectric film 'T-7 and have substantially the same diameter,
thereby facilitating estimation of the sound field region. In the above section and the section E to
explain the present invention in detail, the reference numerals of the embodiment are used to
make the present invention easy to understand, but the present invention is not limited to the
embodiments. F. Embodiments Hereinafter, embodiments of the present invention will be
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described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing an
embodiment of an ultrasonic probe according to the present invention. In the following
description, the same components as those of the conventional example shown in FIG. 6 are
denoted by the same reference numerals, and the description thereof is omitted. The difference
between the prior art and this embodiment lies in the presence of an insulating film interposed
between the upper electrode and the lower electrode. That is, in this embodiment, the planar
dimensions of the upper electrode 8 and the lower electrode 6 are oriented, and are formed
substantially larger than the planar dimensions of the piezoelectric film (piezoelectric element) 7
and piezoelectric Between the upper electrode 8 and the lower electrode 6 in which the film 7 is
not interposed, an insulating film (insulation M) 11 made of 8102 or the like is interposed.
This insulating film] 1 is formed to cover the flat surface 3aJ2 of the one end 3 of the acoustic
lens 2, and the upper electrode 8. It is interposed between the lower electrodes 6. To be precise,
the piezoelectric film 7 is composed of a small diameter portion in contact with the lower
electrode 6 and a large diameter portion in contact with the upper electrode 8 and having the
same planar shape as the lower electrodes 6 and 8. The lower electrode 6 protrudes from the
surface of the insulating film 11, so the insulating layer 11 is interposed between the large
diameter portion of the piezoelectric film 7 and the lower electrode 6. In this embodiment, the
planar shape of the lower electrode 6, the piezoelectric film 7 and the upper electrode 8 are all
circular, the diameters of the upper and lower electrodes 8 and 6 are A, and the diameter of the
piezoelectric film 7 is A '. If it does, it has a relation of A> A '(refer to figure 3). Further, in the
figure, reference numeral 12.13 is a lead wire of the lower electrode 6 and the two-part electrode
8, respectively. Although the method of manufacturing the ultrasonic probe 1 having the
following configuration is optional, an example thereof will be described with reference to FIGS. 2
and 3. First, a photoresist is applied to the flat surface 3a at one end of the lens 2 to form a
photoresist film 20 (FIG. 2 (a)). The photoresist film 20 is transparent, and normally, the acoustic
1 non-slip 2 is also formed of a transparent material. Therefore, it is possible to visually confirm
the concave lens spherical portion S from the one side of-on the photoresist film 20. Therefore,
the mask glass 23 provided with the chromium (Cr) film 22 in which the hole 21 is formed is
exposed to the photoresist spherical film 5 while the hole 21 is within the existing range of the
lens spherical portion 5. It aligns above 20 and exposes by irradiating the light 24 from the
upper side in this state (FIG. 2 (b)). Thereafter, the photoresist film 20 is developed to form holes
25 in the photoresist film 20, as shown in FIG. 2 (c). In this manner, the ultrasonic wave
generation unit 4 should be formed while visually confirming the alignment between the hole 25
and the lens spherical portion 5, and noise generation and the like caused by the positional
deviation can be prevented. While the high performance ultrasonic probe 1 can be manufactured,
the yield is also good. Next, a Cr film is vacuum deposited from above the resist film 20, and then
an Au (gold) film is similarly vacuum deposited on the Cr film to form a metal film 26 to be the
lower electrode 6 2 (d)). Thereafter, when the photoresist film 20 is eluted using a photoresist 1
to 1 release material such as acetone, the lower electrode 6 is formed only at the locations where
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the holes 25 were present.
At this stage, lead wires 27 extending from the surface of the lower electrode 6 to the outside of
the acoustic lens 2 are also formed (see FIG. 3 (a)). Further, the insulating film 11 made of SiO 7
is formed on the lower electrode 6 by the sputtering method or the CVD method. At this time,
since it is necessary to form holes 28 in which a piezoelectric film 7 described later is formed in
this insulating film] -1, two masks as shown in FIG. 4 are disposed above the lower electrode 6,
The insulating film 11 is formed while rotating it in the planar direction. The mask 29 has a size
corresponding to the hole 28, that is, a central shielding portion 29a slightly smaller in diameter
than the lower electrode 6, and a frame 29c provided with a hole 29b having a diameter at least
larger than the planar dimension of the acoustic lens 2; The central shield portion 29a and a
connecting portion 29d connecting the frame portion 29c form a plate as a whole. Therefore, if
sputtering or film deposition is performed while rotating the mask 29, the insulating film 11 in
which the hole 28 is formed in the central portion can be obtained (see FIGS. 2 (e) and 3 (b)). .
Thereafter, a piezoelectric film 7 is formed using a mask having a circular opening of the same
diameter as that of the lower electrode 6. That is, when the circular opening is positioned
coaxially with the hole 28 and ZnO is sputtered, Zn ○ is formed in the hole 28 and the
piezoelectric film 7 having the same shape as the lower electrode 6 of the surface of the
insulating layer 11 is formed. . Next, a Cr film and an Au film are vacuum deposited in the same
manner as the lower electrode 6 to form the upper electrode 8 having the same size as the lower
electrode 6. Then, as shown in FIG. 3 (c), a read wire 30 can be formed on the upper electrode 8
to obtain an ultrasonic probe 1 as shown in FIG. Therefore, in this embodiment, since the
insulating film 11 electrically insulates between the upper electrode 8 and the lower electrode 6
other than the portion where the piezoelectric film 7 is interposed, these electrodes 6, 8 and the
piezoelectric film The planar dimensions of 7 can be estimated to be orientation, and when a
voltage is applied between the electrodes 6 and 8, estimation of the dimensions of a sound
source actually generating an ultrasonic wave is facilitated. If it is expressed accurately by the
code shown in FIG. 3, the diameter φ of the sound source actually generating the ultrasonic
wave can be considered as A ′ ≦ φ ≦ A, and the difference between A and A ′ By making it
smaller, more accurate estimation becomes possible. Thereby, calculation of the sound field in
the acoustic lens 2 becomes easy, and it becomes possible to manufacture a high-performance
ultrasonic probe 1. The details of the structure of the ultrasonic probe according to the present
invention are not limited to the embodiment described above, and various modifications are
possible. For example, the shapes of the upper and lower electrodes 6, 8 and the piezoelectric
film 7 May be as shown in FIGS. 5 (a) and 5 (b).
As described in detail above, according to the present invention, since the insulating layer is
interposed between the "two-part electrode" and the lower electrode in the portion where the
piezoelectric element is not interposed, the piezoelectric element is interposed. An insulating
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layer electrically insulates between the upper electrode and the lower electrode other than the
portion. Therefore, the planar dimensions of the two-part electrode and the lower electrode can
be made larger than those of the piezoelectric element and have substantially the same diameter,
which facilitates estimation of the dimensions of the sound source that is actually generating
ultrasonic waves. Therefore, calculation of the sound field in the acoustic lens becomes easy, and
it becomes possible to manufacture a high-performance ultrasonic probe.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a cross-sectional view showing an embodiment of an ultrasonic probe according to the
present invention.
FIG. 2 is a drawing showing a method of manufacturing the ultrasonic probe. FIG. 3 is a plan view
showing a manufacturing method as in FIG. FIG. 4 is a plan view showing a mask. FIG. 5 is an
enlarged view of an ultrasonic wave generator showing a modification. FIG. 6 is a cross-sectional
view showing an example of a conventional ultrasonic probe. 1: Ultrasonic probe 2: One end of
acoustic lens 3 4: Ultrasonic wave generator 5: Lens spherical portion (converging portion)
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