JP6331513B2 - Acoustic sensor, ultrasonic probe and ultrasonic diagnostic apparatus - Google Patents

Description

  The present invention relates to an acoustic sensor, an ultrasonic probe, and an ultrasonic diagnostic apparatus.

  2. Description of the Related Art Conventionally, there is an ultrasonic diagnostic apparatus that inspects an internal structure by irradiating a subject with ultrasonic waves and receiving and analyzing the reflected waves. In ultrasonic diagnosis, a subject can be examined non-destructively and non-invasively, and thus is widely used for various purposes such as medical examinations and inspections inside buildings.

  In the ultrasound diagnostic apparatus, the received ultrasound is converted into an electrical signal corresponding to the intensity and acquired. A transducer (transducer) using a piezoelectric body is used for the acoustic sensor that receives this ultrasonic wave, and mechanical deformation (expansion / contraction) of the piezoelectric body due to the sound pressure of the ultrasonic wave is an electrical signal corresponding to the amount of deformation. It is converted to (charge amount) and detected. Conventionally, in this acoustic sensor, a vibrator including a piezoelectric body is formed in a plate shape or a thick film shape (usually 10 μm or more, generally 100 μm or more) such as a laminated substrate using a thick film coating technique. Then, the ultrasonic intensity is measured by detecting the deformation in the thickness direction due to the ultrasonic wave incident on the plate surface.

  This piezoelectric material includes a ferroelectric material such as PZT (lead zirconate titanate). Conventionally, a ferroelectric is used in a nonvolatile memory (ferroelectric memory, FeRAM) by using its polarization characteristic having hysteresis. In ferroelectric memory, a ferroelectric thin film is provided between the gate electrode and the channel region between the drain / source, and a voltage is applied to the ferroelectric thin film to maintain a polarization state corresponding to one of the two values. Thus, the electrical conductivity of the channel region is changed, and binary data is read by measuring the state of conduction between the drain and the source (for example, Patent Document 1).

US Pat. No. 3,832,700

  However, with higher resolution and higher sensitivity of ultrasonic diagnostic apparatuses, there is a demand for higher-accuracy ultrasonic probes. At this time, in order to form the piezoelectric member of the acoustic sensor used for ultrasonic reception in the conventional ultrasonic probe with higher accuracy in the current mode, the manufacturing process is required to be complicated and large. There is.

  An object of the present invention is to provide an acoustic sensor, an ultrasonic probe, and an ultrasonic diagnostic apparatus that can easily form a piezoelectric member with high accuracy.

In order to achieve the above object, the invention according to claim 1
Piezoelectric thin films are stacked on the semiconductor substrate directly or indirectly,
Based on the amount of charge induced in the piezoelectric thin film according to the sound pressure incident on the piezoelectric thin film, the energization state of a predetermined region in the semiconductor substrate changes,
A semiconductor chip that outputs a signal corresponding to the energized state ,
The piezoelectric thin film is formed by a ferroelectric member so that a coercive electric field voltage that reverses its polarization state is less than a withstand voltage of the semiconductor chip, and is divided into a plurality of blocks and arranged in at least one direction. And
The semiconductor chip is provided with a voltage application circuit for setting the polarization state of the piezoelectric thin film, and outputs the signal for each of the one or a plurality of the blocks,
The voltage application circuit is an acoustic sensor characterized in that the polarization state can be set for each block .
Here, a thin film refers to what is formed by various thin film manufacturing processes, such as sputtering method, CVD method, and sol-gel method.

The invention according to claim 2 is the acoustic sensor according to claim 1,
The electrical conductivity of the channel region provided in the semiconductor substrate is changed by an electric field generated by the induced charge, whereby the energization state of the channel region is changed.

The invention according to claim 3 is the acoustic sensor according to claim 1,
The semiconductor chip is
An electrode is provided for switching whether the channel region provided in the semiconductor substrate is conductive or not,
When the channel region is in a conductive state, the piezoelectric thin film is in contact with one end of the channel region so that the energization state is changed by the flow of charge according to the amount of the induced charge through the channel region. It is characterized by being connected to each other.

Invention of Claim 4 is an acoustic sensor as described in any one of Claims 1-3 ,
The piezoelectric thin film includes a controller that determines a polarization state of the piezoelectric thin film and controls an operation of the voltage application circuit according to the determined polarization state.

The invention according to claim 5 is the acoustic sensor according to claim 4 ,
The control unit is characterized in that a polarization state is determined according to a process related to a predetermined spatial correlation performed on a received sound wave.

The invention described in claim 6
An ultrasonic probe using the acoustic sensor according to any one of claims 1 to 5 .

The invention described in claim 7
The ultrasonic probe according to claim 6 ,
A signal processing unit for analyzing a signal related to the ultrasonic wave received by the ultrasonic probe;
An output unit for outputting the analysis result of the signal processing unit in a predetermined manner;
An ultrasonic diagnostic apparatus comprising:

The invention described in claim 8
An ultrasonic probe using the acoustic sensor according to any one of claims 1 to 3 ,
A signal processing unit for analyzing a signal related to the ultrasonic wave received by the ultrasonic probe;
An output unit for outputting the analysis result of the signal processing unit in a predetermined manner;
A controller that determines a polarization state of the piezoelectric thin film, and controls an operation of the voltage application circuit according to the determined polarization state;
An ultrasonic diagnostic apparatus comprising:

  According to the present invention, there is an effect that a piezoelectric member for receiving ultrasonic waves can be easily formed with high accuracy.

1 is an overall view showing an ultrasonic diagnostic apparatus according to an embodiment of the present invention. It is a block diagram which shows the internal structure of an ultrasonic diagnosing device. It is a figure explaining the example of a vibrator arrangement. It is a schematic diagram which shows the cross-section of a vibrator | oscillator. It is a schematic diagram which shows the setting of the polarization state in a vibrator array. It is a schematic diagram which shows the cross-section of the vibrator | oscillator of 2nd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is an overall view of an ultrasonic diagnostic apparatus S including an ultrasonic probe using the acoustic sensor of the present embodiment. FIG. 2 is a block diagram showing an internal configuration of the ultrasonic diagnostic apparatus S. As shown in FIG.

  As shown in FIG. 1, the ultrasonic diagnostic apparatus S includes an ultrasonic diagnostic apparatus main body 1 and an ultrasonic probe 2 (ultrasonic probe) connected to the ultrasonic diagnostic apparatus main body 1 via a cable 22. Is provided. The ultrasonic diagnostic apparatus main body 1 is provided with an operation input unit 18 and an output display unit 19. The control unit 15 of the ultrasonic diagnostic apparatus main body 1 outputs a drive signal to the ultrasonic probe 2 and outputs an ultrasonic wave based on an external input operation to an input device such as a keyboard or a mouse of the operation input unit 18. In addition, a reception signal related to ultrasonic reception is acquired from the ultrasonic probe 2 and various processes are performed, and the result and the like are displayed on the liquid crystal screen of the output display unit 19 as necessary.

  As shown in FIG. 2, the ultrasonic diagnostic apparatus main body 1 includes a transmission unit 12, a reception unit 13, a transmission / reception switching unit 14, a control unit 15, an image processing unit 16 (signal processing unit), and a storage unit 17. And an operation input unit 18 and an output display unit 19 (output unit).

  The transmission unit 12 outputs a pulse signal to be supplied to the ultrasonic probe 2 according to the control signal input from the control unit 15, and causes the ultrasonic probe 2 to generate an ultrasonic wave. The transmission unit 12 includes, for example, a clock generation circuit, a pulse generation circuit, a pulse width setting unit, and a delay circuit. The clock generation circuit is a circuit that generates a clock signal that determines the transmission timing and transmission frequency of the pulse signal. The pulse generation circuit is a circuit for generating a bipolar rectangular wave pulse having a preset voltage amplitude at a predetermined cycle. The pulse width setting unit sets the pulse width of the rectangular wave pulse output from the pulse generation circuit. The rectangular wave pulse generated by the pulse generation circuit is separated into different wiring paths for each transducer 21 of the ultrasonic probe 2 before or after input to the pulse width setting unit. The delay circuit is a circuit that delays and outputs the delay time set for each wiring path in accordance with the timing of transmitting the generated rectangular wave pulse to each transducer 21.

  The receiving unit 13 is a circuit that acquires a received signal input from the ultrasound probe 2 under the control of the control unit 15. The receiving unit 13 includes, for example, an amplifier, an A / D conversion circuit, and a phasing addition circuit. The amplifier is a circuit that amplifies a reception signal corresponding to the ultrasonic wave received by each transducer 21 of the ultrasonic probe 2 with a predetermined amplification factor set in advance. The A / D conversion circuit is a circuit that converts an amplified received signal into digital data at a predetermined sampling frequency. The phasing addition circuit adjusts the time phase by giving a delay time to each wiring path corresponding to each transducer 21 with respect to the A / D converted received signal, and adds these (phasing addition) to generate a sound. A circuit for generating line data.

  Based on the control of the control unit 15, the transmission / reception switching unit 14 transmits a drive signal from the transmission unit 12 to the transducer 21 when oscillating ultrasonic waves from the transducer 21, while When such a signal is acquired, a switching operation for causing the reception unit 13 to output the reception signal is performed.

  The control unit 15 includes a CPU (Central Processing Unit), a HDD (Hard Disk Drive), a RAM (Random Access Memory), and the like. The CPU reads various programs stored in the HDD, develops them in the RAM, and performs overall control of operations of the respective units of the ultrasonic diagnostic apparatus S according to the developed programs. The HDD stores a control program and various processing programs for operating the ultrasonic diagnostic apparatus S, various setting data, and the like. These programs and setting data may be stored in an auxiliary storage device using a non-volatile memory such as a flash memory in addition to the HDD so as to be able to be read / written and updated. The RAM is a volatile memory such as SRAM or DRAM, provides a working memory space for the CPU, and stores temporary data.

  The image processing unit 16 performs a calculation process for creating a diagnostic image based on ultrasonic reception data separately from the CPU of the control unit 15. The diagnostic image may include image data to be displayed on the output display unit 19 in substantially real time, a series of moving image data thereof, snapshot still image data, and the like. In addition, the structure by which this arithmetic processing is performed by CPU15 may be sufficient.

  The storage unit 17 is a volatile memory such as a DRAM (Dynamic Random Access Memory), for example. Alternatively, various non-volatile memories that can be rewritten at high speed may be used. The storage unit 17 stores the diagnostic image data for real-time display processed by the image processing unit 16 in units of frames. The ultrasonic diagnostic image data stored in the storage unit 17 is read according to the control of the control unit 15 and transmitted to the output display unit 19 or outside the ultrasonic diagnostic apparatus S via a communication unit (not shown). Or output. At this time, when the display system of the output display unit 19 is a television system, a DSC (Digital Signal Converter) is provided between the storage unit 17 and the output display unit 19 to output after the scanning format is converted. It should be done.

  The operation input unit 18 includes a push button switch, a keyboard, a mouse, a trackball, or a combination thereof, converts a user input operation into an operation signal, and inputs the operation signal to the ultrasonic diagnostic apparatus body 1.

  The output display unit 19 is a display using any one of various display methods such as an LCD (Liquid Crystal Display), an organic EL (Electro-Luminescent) display, an inorganic EL display, a plasma display, and a CRT (Cathode Ray Tube) display. A screen and its drive unit are provided. The output display unit 19 generates a drive signal for the display screen (each display pixel) in accordance with the control signal output from the CPU 15 and the image data generated by the image processing unit 16, and a menu related to ultrasonic diagnosis on the display screen. , Display the status and measurement data based on the received ultrasound.

  The operation input unit 18 and the output display unit 19 may be provided integrally with the housing of the ultrasonic diagnostic apparatus main body 1 or attached to the outside via a USB cable or the like. There may be. Further, if the operation input terminal and the display output terminal are provided in the ultrasonic diagnostic apparatus main body 1, conventional peripheral devices for operation and display may be connected to these terminals for use.

  The ultrasonic probe 2 oscillates an ultrasonic wave (here, about 1 to 30 MHz) and emits it to a subject such as a living body, and a reflected wave (reflected by the subject) of the emitted ultrasonic wave ( It functions as an acoustic sensor that receives (echo) and converts it into an electrical signal. The ultrasonic probe 2 includes a transducer array 210 that is an array of a plurality of transducers 21 that transmit and receive ultrasonic waves, and a cable 22. The cable 22 has a connector (not shown) to the ultrasonic diagnostic apparatus main body 1 at one end, and the ultrasonic probe 2 is configured to be detachable from the ultrasonic diagnostic apparatus main body 1 by the cable 22. ing.

  The vibrator array 210 is an array of a plurality of vibrators 21 each including a piezoelectric element having a piezoelectric body and electrodes provided at both ends where electric charges appear due to deformation (extension / contraction) thereof. , Two-dimensionally arranged in one plane. When a voltage pulse (pulse signal) is supplied to the vibrator 21, the piezoelectric body is deformed according to the electric field generated in each piezoelectric body, and ultrasonic waves are transmitted. Further, when an ultrasonic wave having a predetermined frequency band is incident on the vibrator 21, the thickness of the piezoelectric body fluctuates (vibrates) due to the sound pressure. And an amount of electric charge corresponding to the electric charge is induced in the electrodes at both ends of the piezoelectric element. Here, a ferroelectric material is used as the piezoelectric material. The electric field generated in the ferroelectric substance when transmitting and receiving ultrasonic waves is smaller than the coercive electric field strength of the ferroelectric substance.

FIG. 3 is a diagram for explaining an example of the transducer array 210 in the ultrasonic probe 2.
In the ultrasound probe 2 of the present embodiment, for example, the transducer array 210 includes 3 (width direction) × 192 (scanning direction) = 576 transducers 21 arranged in a two-dimensional array. It is. Alternatively, the transducers 21 may be one-dimensionally arranged in the scanning direction. Further, the number of vibrators 21 can be arbitrarily set. The ultrasonic probe 2 may adopt either an electronic scanning method or a mechanical scanning method, and any of a linear scanning method, a sector scanning method, or a convex scanning method is adopted as a scanning method. It may be what you did. Further, the bandwidth of the ultrasonic reception frequency in the ultrasonic probe 2 can be arbitrarily set.
Further, the ultrasonic diagnostic apparatus S can be configured such that any one of a plurality of different ultrasonic probes 2 depending on the diagnosis target can be connected to the ultrasonic diagnostic apparatus main body 1 and used.

FIG. 4 shows a cross-sectional structure of one transducer 21 related to transmission / reception of ultrasonic waves.
The vibrator 21 according to this embodiment is formed as a semiconductor chip in which a ferroelectric thin film layer 112 (piezoelectric thin film) and a gate electrode 113 are stacked on a semiconductor substrate 100 with a gate insulating film 111 interposed therebetween. . Side walls 114 and 115 are provided on both side surfaces of the ferroelectric thin film layer 112. On the upper surface of the semiconductor substrate 100, extension regions 116, 117 (conductive regions), a source region 101, and a drain region 102 are formed with a region under a gate electrode 113 (a portion serving as a predetermined region and a channel region) interposed therebetween. The The source region 101 and the drain region 102 are connected to metal wirings 103 and 104, respectively.

  The semiconductor substrate 100 is, for example, a p-type silicon substrate. By implanting n-type ions such as phosphorus and arsenic into the semiconductor substrate 100, extension regions 116 and 117 are formed, and further, a source region 101 and a drain region 102 are formed.

  The source region 101 is grounded through the metal wiring 103. The drain region 102 is connected to the signal output via the metal wiring 104. A voltage supply unit can be connected to the gate electrode 113 via a voltage application circuit (not shown) provided on the semiconductor substrate 100, and a gate-source bias voltage is supplied to the gate electrode 113. By applying this bias voltage to the ferroelectric thin film layer 112, the polarization state is changed according to the bias voltage. On the other hand, normally, the gate electrode 113 is kept in a floating state or a ground state, and ultrasonic waves are incident on the ferroelectric thin film layer 112, so that the ultrasonic intensity (sound pressure) and the polarization state are changed. The electric charge corresponding to is generated at both ends (both sides) of the ferroelectric thin film layer 112. In the semiconductor substrate 100, the energization state in the channel region between the source region 101 and the drain region 102 changes according to the electric charge generated on the gate insulating film 111 side of the ferroelectric thin film layer 112, and the source-drain region is changed. The charge that flows through the drain region 102 is output as a signal from the drain region 102.

  The ferroelectric thin film layer 112 is a thin film (usually less than 10 μm, more preferably less than 1 μm) using a ferroelectric member such as PZT (lead zirconate titanate), and the source region 101 and the drain region 102. The surface area and thickness of the channel are set to values corresponding to the reception frequency of the ultrasonic wave while appropriately maintaining the channel length between the two. Ferroelectric materials include PZT, various perovskite-type ferroelectrics, tungsten-bronze-type ferroelectrics, bismuth-layered ferroelectrics, PVDF (polyvinylidene fluoride) or PVDF copolymers. Organic ferroelectrics such as these, or composite materials using these in combination may be used. These ferroelectrics usually have a multidomain and / or polycrystalline structure.

The ferroelectric thin film layer 112 and the gate electrode 113 are formed on the semiconductor substrate 100 using a sputtering method (PVD method (physical vapor deposition method)), a sol-gel method, a CVD method (chemical vapor deposition method), or the like. After the etching, the film is formed by etching back using a mask (photoresist pattern or the like) matched to the structure of the structure. Next, the sidewalls 114 and 115 are also formed by etching after forming an insulating film (for example, silicon dioxide SiO ₂ ) on the semiconductor substrate 100, the ferroelectric thin film layer 112, and the gate electrode 113 by using a CVD method or the like. The The source region 101 and the drain region 102 are formed by performing ion implantation by self-alignment using the gate electrode 113 and the side walls 114 and 115 as a mask. Then, metal wirings 103 and 104 connected to the gate electrode 113, the source region 101, and the drain region 102 are provided.
The plurality of vibrators 21 and the ferroelectric thin film layer 112 (block) corresponding to each of the plurality of vibrators 21 can be individually formed. However, a plurality of vibrators 21 and a plurality of the ferroelectric thin film layers 112 (blocks) can be formed on one or a small number of wafers. Thus, the vibrator array 210 can be formed easily and at low cost while arranging the plurality of vibrators 21 with high accuracy.

As described above, by using the ferroelectric thin film layer 112 for the transducer 21 of the ultrasonic probe 2, the ferroelectric layer is formed uniformly and polarization with high accuracy according to the incident ultrasonic intensity occurs. . Further, by using such a thin film, a voltage (coercive electric field voltage) for generating a coercive electric field necessary for polarization reversal becomes sufficiently small, so that even after circuit formation of the vibrator 21 is easily performed. The polarization state can be changed by applying a voltage to the ferroelectric thin film layer 112. At this time, in the vibrator 21, the withstand voltage of each part, for example, the breakdown voltage of the gate insulating film, the withstand voltage between the drain and the source, the withstand voltage between the PN well, the withstand voltage between the well and the semiconductor substrate, In any case, the thickness of the ferroelectric thin film layer 112 needs to be determined so as to be equal to or higher than the maximum applied voltage for generating a coercive electric field in the ferroelectric thin film layer 112. Usually, the withstand voltage is 10 to several tens of volts or less, and the coercive electric field voltage should be smaller than this. The coercive electric field depends on the ferroelectric material, composition ratio, crystal system, etc., but is about MV / m. In order to make the coercive electric field voltage less than the withstand voltage, the influence of the thickness of the gate insulating film is included. The thickness of the ferroelectric thin film layer 112 is on the order of μm or less.
In addition, here, when ultrasonic waves are transmitted using the ferroelectric thin film layer 112, the voltage applied at the time of transmission can be reduced according to the film thickness, but the polarization is in a range smaller than the coercive electric field voltage. An appropriate value can be set within a range where the state does not change and the amount of heat generation does not become a problem.

  The vibrator 21 according to the present embodiment is not limited to the state in which the polarization directions of the respective regions are aligned, and can receive ultrasonic waves while being set to various polarization states. When the ultrasonic waves are incident on the ferroelectric thin film layer 112 in a state where the polarization directions are perfectly aligned, the entire ferroelectric thin film layer 112 is deformed according to the sound pressure of the ultrasonic waves, as in the case of a normal piezoelectric body. Thus, charges corresponding to the deformation are generated at both ends. On the other hand, when an ultrasonic wave is incident on the ferroelectric thin film layer 112 in a state where the polarization directions of the multi-domain and polycrystalline regions are not aligned, the ferroelectric thin film layer 112 does not undergo stretching deformation as a whole, That is, no charge corresponding to the deformation is generated at both ends. In the polarization state between these, the amount of generated charge is also an intermediate value.

  However, when the polarization state of the ferroelectric thin film layer 112 is changed, the magnitude of the electric field generated in the ferroelectric thin film layer 112 is not proportional to the polarization state. Therefore, the correspondence between the polarization state to be set and the electric field (applied voltage) for changing to the polarization state can be stored in advance in a table in the HDD of the control unit 15 or the like. When the polarization state of the ferroelectric thin film layer 112 is changed, an applied voltage corresponding to the change from the current polarization state to a desired polarization state is obtained by referring to this table, and the source region 101 and the drain region are obtained. The applied voltage may be supplied from the voltage supply unit to the gate electrode 113 with the ground 102. Alternatively, once the current polarization state is changed to a predetermined polarization state, only the table corresponding to the change from the predetermined polarization state is stored by changing the predetermined polarization state to the desired polarization state. Can be.

  In the ultrasonic probe 2 of the present embodiment, the polarization state can be set independently for each transducer 21 of the transducer array 210. That is, the wiring between the voltage supply unit and the gate electrode 113 is provided at least partially on the gate electrode 113 side, via a switching element that can be switched on and off by a control signal from the control unit 15. A voltage can be supplied only to the desired vibrator 21. Alternatively, a configuration in which a voltage dividing circuit or the like is provided in the middle of the individual wiring, and a desired voltage division is applied to the ferroelectric thin film layer 112 of each vibrator 21 with respect to a predetermined voltage output from the voltage supply unit. It may be. In this case, if a resistive element is provided in the ultrasonic probe 2 as a load for voltage division, the size is likely to be larger than that of a semiconductor chip. Therefore, an appropriate voltage is generated by combining a plurality of small capacitors. Also good. Alternatively, a partial pressure may be generated by the ultrasonic diagnostic apparatus main body 1 and supplied to each ferroelectric thin film layer 112 of the ultrasonic probe 2.

Various patterns can be used for setting the polarization state of each vibrator 21. For example, the receiving sensitivity of each transducer 21 can be weighted by changing the polarization state of each transducer 21 for each position. In other words, processing (especially apodization) related to spatial correlation such as weighting for each transducer 21 and formation of a reception window, which has been conventionally performed by individually changing the amplification factor of the amplifier, is performed without adjusting the amplification factor. Can be done.
In particular, in order to reduce the influence of artifacts and the like, the receiving sensitivity of the transducer 21 at a position that is not desired to be received is lowered to zero level, and the polarization state is changed so as to form a receiving window (for example, a Hanning window). I can do it.

FIG. 5 is a diagram schematically showing the setting of the polarization state of each transducer 21 of the transducer array 210 arranged two-dimensionally.
Here, the tendency of the amount of polarization is shown by the length of the double arrow. In this vibrator array 210, the ferroelectric thin film layer 112 related to the vibrator 21 near the center has a large amount of polarization, that is, the polarization direction of each domain (grain) of the multi-domain and the polycrystalline is aligned, It is set so that the polarization amount gradually decreases toward the ferroelectric thin film layer 112 related to the vibrator 21 at the four corners, that is, the polarization directions of the respective domains and crystal regions are not aligned. Thereby, the apodization is set so that the reception sensitivity by the vibrator 21 near the center is high and the reception sensitivity by the vibrators 21 at the four corners is reduced.
Here, the polarization amount (reception sensitivity) is set so as to decrease from the center toward the end in any two-dimensional direction, but the polarization amount may be changed only in the scanning direction.

As described above, in the acoustic sensor used in the ultrasonic probe 2 of the present embodiment, the ferroelectric thin film layer 112 (piezoelectric thin film) is laminated and disposed directly or indirectly on the semiconductor substrate 100. On the basis of the amount of charge induced in the ferroelectric thin film layer 112 according to the sound pressure incident on the ferroelectric thin film layer 112, the energization state of the channel region in the semiconductor substrate 100, that is, the amount of flowing charge changes. The vibrator 21 for outputting a signal corresponding to the energized state is provided.
In this way, a high-precision piezoelectric layer can be formed by receiving ultrasonic waves using a thin film formed by sputtering or the like, so that data with higher resolution and higher resolution can be easily obtained. Can be acquired.

  Further, the electrical conductivity of the channel region provided in the semiconductor substrate 100 is changed by the electric field generated by the electric charge induced in the ferroelectric thin film layer 112 with the incidence of the ultrasonic wave, thereby changing the energization state of the channel region. Since the structure is changed, such an acoustic sensor can be manufactured easily and at low cost using a conventional FeRAM manufacturing process.

In addition, the vibrators 21 each having the ferroelectric thin film layer 112 are arranged in a plurality of two-dimensional arrays or one-dimensionally, and each oscillator 21 outputs a signal related to the ultrasonic reception intensity. The transducer array 210 can be formed in a compact manner.
Further, since such vibrators 210 can be formed collectively on one or a small number of wafers, the vibrator array 210 can be formed easily and at low cost while arranging the plurality of vibrators 21 with high accuracy. I can do it.

  Further, the ferroelectric thin film layer 112 is formed by a ferroelectric member such as PZT so as to be less than the withstand voltage of the vibrator 21 in which a coercive electric field voltage for inverting the polarization state is formed. The ultrasonic wave can be received with appropriate sensitivity by the vibrator 21 by adjusting the ferroelectric thin film layer 112 to an appropriate polarization state. In addition, since the polarization state can be set after the vibrator 21 and the vibrator array 210 are formed, it is possible to easily cope with a secular change in reception sensitivity.

  Further, the vibrator 21 is provided with a voltage application circuit for setting the polarization state of the ferroelectric thin film layer 112, and can easily be controlled by internal control of the ultrasonic probe 2 and the ultrasonic diagnostic apparatus 1. The polarization state of the ferroelectric thin film layer 112 can be adjusted.

  Further, since the voltage application circuit is provided so that the polarization state can be individually set for each vibrator 21, it is possible to easily adjust the sensitivity between the individual vibrators 21. In particular, spatial sensitivity weighting and reception window formation can be performed according to the reception status, so that the processing that has been performed by reducing the artifacts or adjusting the amplification factor of the conventional amplifier can be performed. 21 can be performed.

  In addition, a control unit 15 is provided that determines the polarization state of the ferroelectric thin film layer 112 and controls the operation of the voltage application circuit in accordance with the determined polarization state. Therefore, fine settings such as sensitivity weighting for each transducer 15 can be performed easily, frequently, and at high speed.

  In addition, the control unit 15 can determine the polarization state according to the process related to the spatial correlation such as apodization performed on the received sound wave. Processing such as adjustment of the amplification factor can be simplified or omitted.

  Further, by using the acoustic sensor as described above for the ultrasonic probe 2, the ultrasonic probe 2 can be formed with a light weight, compactness, high sensitivity, and high resolution.

  Moreover, the image processing unit 16 that analyzes the signal related to the ultrasonic wave received by the ultrasonic probe 2 described above, and the output display unit 19 that outputs the analysis result of the image processing unit 16 in a predetermined format are provided. With the ultrasonic diagnostic apparatus S, a user can easily perform ultrasonic diagnosis based on an ultrasonic diagnostic image with high accuracy and high sensitivity at low cost.

[Second Embodiment]
Next, the ultrasonic probe 2 according to the second embodiment will be described.
This ultrasonic probe 2 is the same as the ultrasonic probe 2 of the first embodiment except that the structure of the vibrator 21b is different from that of the vibrator 21, and the same components are denoted by the same reference numerals. Therefore, the description is omitted.

  FIG. 6 is a diagram illustrating a cross-sectional structure of one transducer 21b related to transmission / reception of ultrasonic waves in the ultrasonic probe 2 according to the second embodiment.

In the ultrasonic probe 2 of the present embodiment, a gate electrode 112b (electrode) and a metal wiring 113b are provided on a p-type semiconductor substrate 100 via a gate insulating film 111. In addition, the structure relating to the gate electrode is buried by insulating films 121 and 131. A contact plug 103 b provided through the insulating films 121 and 131 is connected to the source region 101.
Further, here, the drain region 102 is adjacent to the arranged transfer electrode 118.

  On the insulating film 121, a ferroelectric thin film layer 132 is sandwiched and laminated by electrodes 133 and 134 to form a ferroelectric capacitor as a piezoelectric element, and one of these electrodes 133 and 134 is formed. Here, the electrode 134 is connected to the contact plug 103 b via the metal wiring 135.

  The transfer electrode 118 is formed of a metal member or the like, and a potential well is formed in the semiconductor substrate 100 below the transfer electrode 118 by sequentially applying an ON voltage. By moving the potential wells in an overlapping manner, the charges flowing into the drain region 102 are transferred through the formed potential wells and transferred through the semiconductor substrate 100 on the principle of CCD (Charge Coupled Device). To go.

  The gate electrode 112b is formed of, for example, polysilicon, and a desired voltage is supplied from a voltage supply unit connected via the metal wiring 113b, so that the voltage is applied between the gate and the source, and the semiconductor substrate 100 The conduction state of the channel region between the source region 101 and the drain region 102 under the gate electrode 112b is changed.

  As the insulating films 121 and 131, a silicon insulating film using silicon dioxide is used. After the insulating films 121 and 131 are formed, a mask is formed using a photoresist or the like, a contact hole is formed by etching, tungsten or the like is injected into the contact hole, and then polishing is performed by etch back or CMP (Chemical Mechanical Polishing). The contact plug 103b is formed by, for example.

  The electrode 134 provided in the ferroelectric capacitor is kept in a grounded state. On the other hand, the electrode 133 is connected to the source region 101, and when an ultrasonic wave is incident on the ferroelectric thin film layer 132, charges are generated at both ends of the ferroelectric thin film layer 132. Current flows between them. By applying a predetermined voltage to the metal wiring 113b and the gate electrode 112b during reception of the ultrasonic wave so that the channel region can be energized, this current is further sent from the drain region 102 to the signal output via the channel region. .

  Further, the electrode 133 can be connected to a voltage supply unit, and by supplying a desired voltage from the voltage supply unit, an electric field is generated between the electrodes 133 and 134, and the polarization state of the ferroelectric thin film layer 132 is increased. Can be changed.

  As the ferroelectric thin film layer 132, the same ferroelectric as the ferroelectric thin film layer 112 in the vibrator 21 of the ultrasonic probe 2 of the first embodiment can be used. The ferroelectric thin film layer 132 according to this ferroelectric capacitor is formed with an area corresponding to the ultrasonic reception frequency. At this time, the ferroelectric thin film layer 132 is not limited with respect to the channel length, but is appropriately shaped and arranged according to the spatial resolution of the ultrasonic probe 2 related to the plurality of transducers 21b. In FIG. 6, the ferroelectric capacitor and the FET are drawn in the same size, but this is a schematic one. Actually, it is possible to reduce the size of the FET, but the size of the ferroelectric capacitor cannot be reduced with respect to the ultrasonic reception frequency, so the ferroelectric capacitor is larger. Become.

As described above, the ultrasound probe 2 of the second embodiment is provided with the gate electrode 112b for switching the conduction of the channel region provided in the semiconductor substrate 100, and a predetermined voltage is applied to the gate electrode 112b. When the channel region is in a conducting state, the amount of charge flowing through the channel region by flowing a charge corresponding to the amount of charge induced in the ferroelectric thin film layer 132 by the incidence of ultrasonic waves through the channel region (energized state) The ferroelectric thin film layer 132 is connected to one end of the channel region via the electrode 134, the metal wiring 135, and the contact plug 103b.
By providing the ferroelectric capacitor in this way and guiding it to the channel region, the FET related to the signal output while adjusting the size of the ferroelectric capacitor (ferroelectric thin film layer 132) related to ultrasonic reception to the size of the reception frequency. The structure can be easily downsized. At this time, since the ferroelectric is formed of a thin film, a highly accurate acoustic sensor can be provided while being stacked with the FET structure without taking up space.

The present invention is not limited to the above-described embodiment, and various modifications can be made.
For example, although the ferroelectric thin film layer is used in the above embodiment, the present invention is similarly applied even when an acoustic sensor is formed using a normal piezoelectric thin film that does not have ferroelectricity or is weak. I can do it. In this case, since the desired polarization state cannot be maintained, there is no need for a configuration for setting the polarization state by applying a voltage between the gate and the source from the voltage supply unit. On the other hand, when apodization or the like is performed, it is necessary to cope with it by changing the amplification level of the amplifier as usual.

  Even when a ferroelectric thin film is used, the polarization state is adjusted only in response to a long-term change due to aging, etc. Apodization and window setting may be performed by switching.

  In the first embodiment, the gate oxide film is sandwiched between the ferroelectric thin film layer and the silicon substrate. However, as in the MFSFET structure, the ferroelectric thin film layer is directly formed without sandwiching the gate oxide film. It may be laminated on a silicon substrate.

  In the second embodiment, the energization state is controlled via the FET type transistor, but a bipolar type transistor may be used. In this case, the ferroelectric thin film is connected to the emitter instead of the source region. The withstand voltage compared to the coercive electric field voltage includes the withstand voltage between the base, emitter, and collector regions.

  In the second embodiment, an example in which the charge related to one ferroelectric capacitor is supplied to the channel region of one FET has been described as an example. There may be. In this case, it is possible to output charge signals from the n-channel FET and the p-channel FET by using two ferroelectric capacitors whose polarization states are aligned in the same direction. Alternatively, when the polarization states of the two ferroelectric capacitors are reversed, a charge signal corresponding to the amplitude intensity of the ultrasonic wave is output in a rectified form from the n-channel FET and the p-channel FET.

  Further, in the above-described embodiment, the ultrasonic probe according to the medical ultrasonic diagnostic apparatus has been described as an example. However, the ultrasonic diagnostic apparatus used for diagnosis inside the building structure may be used. . In this case, the acoustic sensor portion that transmits and receives ultrasound does not have to be provided outside the ultrasound diagnostic apparatus body as an ultrasound probe, and may be provided integrally with the ultrasound diagnostic apparatus body.

  Further, the vibrator as the acoustic sensor of the present invention does not need to be used in an ultrasonic diagnostic apparatus, and may be used in a measurement apparatus that simply measures the reception intensity of ultrasonic waves. In such a case, only a single acoustic sensor may be provided without providing a plurality of acoustic sensors.

  Moreover, although the case where the ultrasonic wave of 1-30 MHz was received was demonstrated in the said embodiment, about the acoustic sensor which receives the sound wave of the frequency band which can be received when a piezoelectric member is formed in a thin film manufacturing process, this book The invention can be applied.

In the above embodiment, the control unit is provided only in the ultrasonic diagnostic apparatus main body 1 and the control signal is sent to the ultrasonic probe 2. However, the control unit is partially set according to the power consumption, size, weight, and the like. The control may be performed by the ultrasonic probe 2. Thereby, the amount of the control signal passing through the cable 22 can be reduced. Alternatively, the setting data is held by the ultrasonic probe 2, and the polarization state is set using the setting data by the ultrasonic probe 2 based on the control signal from the ultrasonic diagnostic apparatus main body 1. It's also good.
In addition, specific details such as configurations and structures shown in the above embodiments can be appropriately changed without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Ultrasonic diagnostic apparatus main body 2 Ultrasonic probe 12 Transmission part 13 Reception part 14 Transmission / reception switching part 15 Control part 16 Image processing part 17 Memory | storage part 18 Operation input part 19 Output display part 21 Vibrator 21b Vibrator 22 Cable 100 Semiconductor Substrate 101 Source region 102 Drain region 103 Metal wiring 103b Contact plug 104 Metal wiring 111 Gate insulating film 112 Ferroelectric thin film layer 112b Gate electrode 113 Gate electrode 113b Metal wiring 114, 115 Side walls 116, 117 Extension region 118 Transfer electrodes 121, 131 Insulating film 132 Ferroelectric thin film layer 133 Electrode 134 Electrode 135 Metal wiring 210 Transducer array S Ultrasonic diagnostic apparatus

Claims (8)

Piezoelectric thin films are stacked on the semiconductor substrate directly or indirectly,
Based on the amount of charge induced in the piezoelectric thin film according to the sound pressure incident on the piezoelectric thin film, the energization state of a predetermined region in the semiconductor substrate changes,
A semiconductor chip that outputs a signal corresponding to the energized state ,
The piezoelectric thin film is formed by a ferroelectric member so that a coercive electric field voltage that reverses its polarization state is less than a withstand voltage of the semiconductor chip, and is divided into a plurality of blocks and arranged in at least one direction. And
The semiconductor chip is provided with a voltage application circuit for setting the polarization state of the piezoelectric thin film, and outputs the signal for each of the one or a plurality of the blocks,
The acoustic sensor , wherein the voltage application circuit is provided so that the polarization state can be set for each block .   2. The acoustic sensor according to claim 1, wherein the conduction state of the channel region is changed by changing the electric conductivity of the channel region provided in the semiconductor substrate by an electric field generated by the induced electric charge. . The semiconductor chip is
An electrode is provided for switching whether the channel region provided in the semiconductor substrate is conductive or not,
When the channel region is in a conductive state, the piezoelectric thin film is in contact with one end of the channel region so that the energization state is changed by the flow of charge according to the amount of the induced charge through the channel region. The acoustic sensor according to claim 1, wherein the acoustic sensor is connected and arranged. Wherein define the polarization state of the piezoelectric thin film, according to any one of claims 1 to 3, characterized in that in accordance with the determined polarization state and a control unit for controlling the operation of the voltage application circuit Acoustic sensor. The acoustic sensor according to claim 4 , wherein the control unit determines a polarization state according to a process related to a predetermined spatial correlation performed on the received sound wave. An ultrasonic probe using the acoustic sensor according to any one of claims 1 to 5 . The ultrasonic probe according to claim 6 ,
A signal processing unit for analyzing a signal related to the ultrasonic wave received by the ultrasonic probe;
An output unit for outputting the analysis result of the signal processing unit in a predetermined manner;
An ultrasonic diagnostic apparatus comprising: An ultrasonic probe using the acoustic sensor according to any one of claims 1 to 3 ,
A signal processing unit for analyzing a signal related to the ultrasonic wave received by the ultrasonic probe;
An output unit for outputting the analysis result of the signal processing unit in a predetermined manner;
A controller that determines a polarization state of the piezoelectric thin film, and controls an operation of the voltage application circuit according to the determined polarization state;
An ultrasonic diagnostic apparatus comprising:

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