JP2002027594A - Ultrasonic probe and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a probe structure optimal to the high density mounting of a vibrator. SOLUTION: This ultrasonic probe 100 is provided with a circuit mounted board 110, a semiconductor device 120 in which a plurality of changeover switch circuits are integrated, and an electric/acoustic converting layer 130 formed on a back face 120a of the semiconductor device 120. Then, the electric/acoustic layer 130 is provided with driving electrodes 132 respectively formed on electrodes connected to the contacts of the respective changeover switch circuits, piezoelectric thin films 131 formed as vibrators on the respective driving electrodes 132, a ground electrode 134 commonly formed to all the piezoelectric thin films 131, insulating layers 133 packed between the respective driving electrodes 131 and the ground electrode 134, and an acoustic matching layer 135 formed on the ground electrode 134 as the outermost layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an applied technique of ultrasonic flaw detection, and more particularly to an ultrasonic probe suitable for obtaining a tomographic image and a method of manufacturing the same.

[0002]

2. Description of the Related Art Ultrasonic tomographic image display apparatuses are used in various fields such as medical diagnosis and internal flaw detection of structures because of their advantages such as small size, easy movement, and excellent operability. FIG. 5 shows a structural example of this ultrasonic tomographic image display device.

The ultrasonic tomographic image display main body 500 includes:
Array type ultrasonic probe 60 for transmitting and receiving ultrasonic waves
0 is connected via the cable 700. The monitor 50 is provided on the ultrasonic tomographic image display main body 500.
1. A signal processing system 502 for converting the output from the ultrasonic probe 600 into luminance information on the monitor 501 is mounted.

[0004] The ultrasonic probe 600 has two wiring boards 630 and 660.

[0005] On one wiring board 660, a changeover switch circuit 661 and other circuits (memory, buffer, etc.) 662 connected in series to each of the piezoelectric ceramic vibrators on the other wiring board 630 are mounted. I have. Note that these circuits 661 and 662 may be provided in the signal processing system of the ultrasonic tomographic image display device main body 500. However, in order to prevent signal delay and signal attenuation in the cable 700, usually, , Ultrasonic probe 60
0 on the circuit mounting board.

As shown in FIG. 6, a plurality of strip-shaped piezoelectric ceramic vibrators 631 are fixed to the other wiring board 630 (circuit mounting board). More specifically,
Electrodes 631a on both surfaces of each piezoelectric ceramic vibrator 631,
One of the electrodes 631a among the electrodes 631b is joined to the electrode 632 on the electrode surface 630a side of the wiring board 630 by solder 633. One ground electrode plate 635 is attached to the other electrode 631b of all the piezoelectric ceramic vibrators 631 with a conductive adhesive 634. Note that 636 is an acoustic matching layer attached to the ground electrode plate 635, 637 is an insulator filled between the piezoelectric ceramic vibrators 631, and 638
Is an absorption layer for absorbing a sound wave from the back surface 630b of the wiring board 630 (the surface 630b opposite to the electrode surface 630a).

The arrangement structure of the piezoelectric ceramic vibrators 631 on the wiring board 630 includes 1D (Dimensi
onal) array and 2D array (Dimensional).

An ultrasonic probe having an array structure called a 1D array (hereinafter referred to as a 1D array probe)
The plurality of piezoelectric ceramic vibrators 631 are arranged at a predetermined pitch in a line on the surface of the wiring board 630. According to the 1D array probe, a tomographic image of an observation target can be obtained by electronic scanning by switching of the changeover switch circuit 661.

In the case of an ultrasonic probe having an array structure called a 2D array (hereinafter referred to as a 2D array probe), a plurality of piezoelectric ceramic vibrators 631 are connected to the wiring board 6.
30 in a two-dimensional matrix. According to this 2D array probe, the changeover switch circuit 661
The three-dimensional image of the observation target can be obtained by the electronic scanning by the switching. The technology related to this 2D array probe is described in 1996 IEEE ULTRASONICS SYMPOSIUM pp1523-pp.
1526, 1996 IEEE ULTRASONICS SYMPOSIUMpp1573-pp
1576. For example, in the latter document, 40
A 2D array probe in which 96 piezoelectric ceramic transducers (0.22 mm in width × 0.22 mm in length) are arranged in a 64 × 64 matrix at a pitch of 0.3 mm is described.

[0010]

In an ultrasonic probe, high-density mounting of transducers is an important issue from the viewpoint of miniaturization of the ultrasonic probe and improvement of image resolution. In particular, with respect to the 2D array probe, there is a high demand for high-density mounting of transducers.

However, considering the reliability (connection accuracy, connection strength, etc.) of the solder joint between the wiring board and the vibrator, the above-described conventional probe structure (see FIG. 6) has a 1D array probe and a Both 2D array probes have limitations on the miniaturization of transducers. In addition, when the vibrator is miniaturized, a high-density wiring of a wiring board on which the vibrator is mounted is required.

Accordingly, an object of the present invention is to provide an ultrasonic probe having a structure optimal for high-density mounting of a transducer and a method of manufacturing the same. It is another object of the present invention to provide an ultrasonic tomographic image display device having the ultrasonic probe.

[0013]

In order to solve the above-mentioned problems, in the present invention, a piezoelectric thin film is grown as a piezoelectric element on a semiconductor element for turning on / off a voltage applied to a plurality of piezoelectric elements.

In the following, an embodiment of the present invention will be described in detail. However, the matters included in the configuration have a degree of freedom of combination as much as possible, and any of the combinations is It constitutes the invention. Therefore, for example, an embodiment in which a part of the configuration described as an embodiment of the present invention is appropriately deleted below is also one of the embodiments of the present invention.

[0015] Further, each of the items included in the configuration specifically shown below can be replaced by another configuration having the same function, and as a means specified by the same function. Can be comprehensively expressed.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

First, an ultrasonic probe according to the present embodiment will be described with reference to FIGS. However, here, a 2D probe is taken as an example.

As shown in FIG. 1, the present ultrasonic probe 100
Is a circuit mounting board 110, an electroacoustic conversion layer 130 including a plurality of transducers 131 (piezoelectric thin films), a memory and other circuit elements (not shown), and a plurality of switching units connected in series to each of the transducers 131. It has a semiconductor element 120 in which a switch circuit (121 in FIG. 2) is built, and a connector 111 to which a cable 111a from the ultrasonic image display device is connected.

The semiconductor element 120, the connector 111, the memory, and other circuit elements are mounted on the uppermost wiring layer 110a of the circuit mounting board 110, respectively. Here, the semiconductor element 120 is formed by a flip chip method.
And the circuit mounting board 110 are electrically connected, but an electrode pad for connecting to an electrode pad of the circuit mounting board 110 is provided on the back surface 120a (the surface opposite to the circuit mounting board 110) of the semiconductor element 120. The semiconductor element 120 and the circuit mounting substrate 110 may be formed and electrically connected by a wire bonding method.

In the semiconductor element 120, in addition to the plurality of changeover switch circuits 121, lead wires from the contacts (121a, 121b in FIG. 2) of the plurality of changeover switch circuits 121, and a plurality of electrodes (circuit mounting) connected to the respective lead lines (Including the aforementioned electrodes soldered to the electrode pads of the substrate 110). The lead wiring (122 in FIG. 2) from one contact 121b of each changeover switch circuit 121 merges with one wiring (122a in FIG. 2), and is then soldered to the electrode pad of the circuit board 110. One of the electrodes
Connected to one. As described above, the number of connection points between the semiconductor element 120 and the circuit mounting board 110 is reduced by using a common lead wiring from one contact point 121b from all the changeover switch circuits 121.

Wiring (123 in FIG. 2) extending from the other contact (121a in FIG. 2) of each changeover switch circuit 121
Are arranged in a matrix of n rows and m columns (here, for example, 3 × 3) in the back surface 120b of the semiconductor element. The electroacoustic conversion layer 130 is formed on the back surface 120a.

The electroacoustic layer 130 includes a semiconductor element 120
Drive electrodes 132 formed on the respective electrodes on the back surface 120a of each of them, a piezoelectric thin film 131 formed as a vibrator on each of the drive electrodes 132, and a ground electrode 134 (reference potential) formed in common on all the piezoelectric thin films 131. ), An insulating layer 133 filled between each drive electrode 131 and the ground electrode 134, and an acoustic matching layer 135 formed on the ground electrode 134 as the outermost layer. The acoustic matching layer 135 is for matching acoustic impedance between each transducer 131 and a subject (for example, a living body).

As described above, according to the probe structure according to the present embodiment, the drive electrode 132 and the piezoelectric thin film 131 are sequentially formed on the electrode of the semiconductor element 120 including the plurality of changeover switch circuits 121. Since soldering is not used for connecting the vibrator, the reliability of the connection can be maintained even if the vibrator is miniaturized. Of course, even when a transducer having the same size as the ultrasonic probe described in the section of the related art is mounted, the effect of improving the reliability of the connection of the transducer can be obtained.

The contact 1 of each changeover switch circuit 121
The lead wiring 123 from the terminal 21a is formed on a semiconductor substrate by using a semiconductor process technology. Therefore, a wiring pitch on the order of submicrons can be realized.

As described above, according to the probe structure according to the present embodiment, two factors that have hindered the high-density mounting of the fine vibrator can be solved, and the height of the fine vibrator can be reduced. It is possible to realize density packaging. If a fine transducer is mounted at a high density using this probe structure, the size of the ultrasonic probe can be reduced and the resolution of an ultrasonic image can be improved.

Further, since the drive electrode 134 and the piezoelectric thin film 131 are formed on each electrode on the back surface 120a of the semiconductor element 120, wiring between the semiconductor element and each vibrator can be omitted. The wiring board (630 in FIG. 6) on which the wiring between the vibrator and the changeover switch circuit is formed, which is required in the probe structure of (1), becomes unnecessary. For this reason, the configuration of the ultrasonic probe can be simplified.

In this embodiment, only the changeover switch circuit is formed in the semiconductor element, but other circuits may be formed in the semiconductor element together with the changeover switch circuit. Further, in the present embodiment, the connector for connecting the cable is provided on the circuit mounting board. However, the cable may be directly connected to the circuit mounting board by soldering or the like without using the connector.

Next, a method of manufacturing the ultrasonic probe according to the present embodiment will be described with reference to FIG. Note that the above-described changeover switch circuit and the like are built in the semiconductor element used here.

Solder bumps 124 for connection to electrode pads on the circuit mounting substrate 110 are formed on the electrodes on the back surface 120b (surface 120b facing the circuit mounting substrate 110) of the semiconductor element 120, respectively. On the other hand, each electrode arranged in a matrix on the back surface 120a of the semiconductor element 120 is provided with a conductive thin film (for example, aluminum, copper, ITO, or the like) as a driving electrode 132 of the vibrator by a thin film technique such as sputtering. ) Is formed (FIG. 3A).

Then, by the photo etching technique,
A predetermined region in the back surface 120 of the semiconductor element 120 (the insulating layer 1
A mask pattern is formed in a region where the layer 33 is to be formed (FIG. 3B).

Thereafter, in a vacuum atmosphere, an appropriate control atmosphere, or the like, a piezoelectric material (piezoelectric ceramics such as PZT,
A piezoelectric thin film 131 of ZnO or the like is formed on each drive electrode 133 (FIG. 3C). Examples of a method for forming these piezoelectric thin films 131 include an electron beam evaporation method, an activated reactive evaporation (ARE) method, a sputtering method, a cluster ion beam (ICB) method, an ion beam sputtering (IBS) method, and a chemical vapor deposition method. Phase crystal growth (CVD) method, atomic layer epitaxy (A
LE) growth method, molecular beam epitaxial (MBE) growth method,
A gas source (MBE or CBE) method, electron cyclotron resonance (ECR), or the like can be used.

Then, after removing the piezoelectric thin film that has grown on the insulating layer 133, the mask pattern 300 is removed. Then, a low-viscosity insulating resin or the like is poured into the region from which the mask pattern 300 has been removed, and is cured to form the insulating layer 133. However,
When the mask pattern 300 is formed of an insulating material such as a photoresist, the mask pattern 300 may be used as the insulating layer 133 as it is.

Then, a ground electrode 134 covering all the piezoelectric thin films 131 is formed (FIG. 3D). The ground electrode 134 may be a conductive thin film grown by a thin film technique such as sputtering, a conductive resin layer formed by applying a conductive resin, a metal layer formed by bonding a metal foil, or the like. I just need.

Thereafter, a material (for example, a mixture of a metal powder and an epoxy resin) for matching the acoustic impedance with the test object is adhered to the ground electrode 134, so that the acoustic matching layer 135 is formed on the ground electrode 134. Is formed (FIG. 3E). In the case where the acoustic matching layer 135 is formed by adhering a material to match the acoustic impedance with the subject, if a conductive adhesive is used for bonding the material, the conductive adhesive layer is grounded. It may be used as an electrode.

When the electroacoustic conversion layer 130 on the back surface 120a side of the semiconductor element 120 is completed in this way, the semiconductor element 120 and other circuits and the like are mounted on the circuit mounting board 110. Thus, the ultrasonic probe 100 is completed.

In this embodiment, one ultrasonic probe 100 is manufactured. However, when a plurality of ultrasonic probes are manufactured, a wafer on which a plurality of semiconductor elements are formed is used. May be prepared, and the electroacoustic conversion layer 130 may be formed in a single step on a plurality of semiconductor elements formed on the wafer.

Finally, with reference to FIG. 4, an ultrasonic image display device which is an example of the ultrasonic probe 100 according to the present embodiment will be described.

The present ultrasonic image display device 400 includes a monitor 4
01, a signal processing system 402 to which the cable 111a from the ultrasonic probe 100 is connected, and the like.

The signal processing system 402 includes a voltage generator (not shown) for generating a voltage for driving each transducer of the ultrasonic probe 100, and monitors an output from the ultrasonic probe 100. A conversion processing unit for converting into the above luminance information,
It has a changeover switch circuit of the ultrasonic probe 100 and a control unit for controlling the entire ultrasonic image display device.

With such a configuration, the ultrasonic probe 10
When the focal depth of the ultrasonic beam from 0 is moved in the XY biaxial directions, a three-dimensional ultrasonic image of the observation target is displayed on the monitor 401.

In the above, the case where the present invention is applied to a 2D array probe has been described as an example.
The present invention is also applicable to a probe other than the D array probe, for example, a 1D array probe.

[0042]

According to the present invention, a probe structure optimal for high-density mounting of a fine vibrator can be obtained.

[Brief description of the drawings]

FIG. 1A is a front view of an ultrasonic probe according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA.

FIG. 2 is a wiring diagram of a changeover switch circuit section of the semiconductor device according to one embodiment of the present invention.

FIG. 3 is a diagram illustrating a method for manufacturing an ultrasonic probe according to an embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of an ultrasonic image display device according to an embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of a conventional ultrasonic image display device.

FIG. 6 is a view for explaining the structure of a conventional ultrasonic probe.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 ultrasonic probe 110 circuit board 111 connector 111 a cable 120 semiconductor element 121 switch circuit 130 electroacoustic conversion layer 131 piezoelectric thin film 132 drive electrode 133 insulating layer 134 ground electrode 135 ... Acoustic matching layer 400 ... Ultrasonic image display device main body

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H04R 3/00 330 H04R 3/00 330 31/00 330 31/00 330 (72) Inventor Takashi Kuroki Kanagawa 292 Yoshida-cho, Totsuka-ku, Yokohama, Japan Inside Hitachi, Ltd.Production Technology Laboratory (72) Inventor Hidezo Sano 1-1-14 Uchikanda, Chiyoda-ku, Tokyo Inside Hitachi Medical Corporation (72) Inventor Takaya Osawa Tokyo Hitachi Medical Co., Ltd. 1-11-1 Uchikanda, Chiyoda-ku, Tokyo (72) Inventor Masasaku Ishihara 292 Yoshidacho, Totsuka-ku, Yokohama-shi, Kanagawa Pref. GA00 GB02 GB21 4C301 EE20 GB09 GB18 5C054 AA05 CA08 CB03 EA01 EA05 FD05 HA05 HA12 5D019 AA06 AA26 BB02 BB19 BB28 EE06 FF04 GG01 GG11 HH01 HH02

Claims (3)

[Claims] An ultrasonic probe comprising: a plurality of piezoelectric elements; and a semiconductor element for turning on and off a voltage applied to the plurality of piezoelectric elements, wherein each of the piezoelectric elements is formed on the semiconductor element. An ultrasonic probe comprising a plurality of formed piezoelectric thin films. 2. An ultrasonic probe manufacturing method for manufacturing an ultrasonic probe for turning on and off a supply voltage to a plurality of piezoelectric elements by a semiconductor element, wherein each of said piezoelectric elements is provided to said semiconductor element. A method for manufacturing an ultrasonic probe, comprising a step of growing a plurality of piezoelectric thin films. 3. An ultrasonic probe according to claim 1, wherein said image processing apparatus displays an image corresponding to an echo signal detected by said ultrasonic transducer on a monitor. An image processing apparatus comprising: