JP7242240B2 - ultrasound diagnostic equipment - Google Patents

Description

One embodiment of the present invention relates to an ultrasonic diagnostic apparatus including a semiconductor device and a control method thereof. In particular, the present invention relates to an ultrasonic probe, a scanning method for the ultrasonic probe, an ultrasonic image processing system, or a control system for an ultrasonic diagnostic apparatus.

In this specification, a semiconductor device refers to all devices that can function by utilizing semiconductor characteristics, and electro-optical devices, semiconductor circuits, and electronic devices are all semiconductor devices.

By applying the probe of an ultrasound diagnostic device to the surface of a living body such as a human being and performing ultrasound diagnosis, the inside of the body can be displayed as an ultrasound image. Highly scrutinized. In addition, since the ultrasonic diagnostic apparatus can observe a tomographic image of an object to be measured in a short period of time, it is useful for diagnosing parts of the human body.

Ultrasonic sensors are also used as vehicle detection sensors in parking lots. One ultrasonic sensor is provided on the ceiling or the like for one parking area, and a plurality of ultrasonic sensors are used for the entire parking lot.

Patent Literature 1 discloses a semiconductor device that identifies the position of a detection target using a plurality of ultrasonic sensors.

U.S. Patent Publication No. 2014/0306935

When a plurality of ultrasonic sensors are used, since ultrasonic waves are elastic waves, mutual interference occurs depending on their positions. Therefore, various measures are taken to prevent interference. For example, ultrasonic sensors with different oscillation frequencies are used.

The higher the frequency of ultrasonic waves, the better the resolution, but the greater the attenuation and the worse the permeability. Ultrasound diagnostic equipment creates an image based on the signal received by the probe as a reflected wave of ultrasonic waves emitted inside the human body. Since it becomes weaker, it is necessary to correct it with an amplifier or the like, which may reduce the accuracy of the image.

An object of the present invention is to provide an ultrasonic diagnostic apparatus capable of solving the problem of attenuation and improving diagnostic imaging performance. An object is to provide an ultrasonic diagnostic apparatus that can obtain a highly accurate image even with high-frequency ultrasonic waves. Another object is to provide an ultrasonic image processing system.

Another object is to provide an ultrasonic probe that is most suitable for ultrasonic diagnosis. Another object is to provide a novel scanning method for an ultrasonic probe.

Another object is to provide a new control method for an ultrasonic diagnostic apparatus. Another object is to provide a control system for an ultrasonic diagnostic apparatus.

In order to solve the above problems, an ultrasonic probe is provided in which transducers are arranged in a matrix so that ultrasonic waves from a plurality of transducers are mutually interfered and strengthened. Ultrasonic waves transmitted from a plurality of transducers interfere with each other as they travel through the body, and the transducers receive the reflected waves. By intentionally interfering and using intensified ultrasonic waves, sufficiently strong reflected waves can be obtained even in the deep parts of the human body, improving diagnostic imaging performance.

One of the configurations disclosed in this specification is a plurality of transducers arranged in a matrix so that ultrasonic waves interfere with each other, and each of the plurality of transducers is connected via a receiving circuit. The ultrasonic diagnostic apparatus includes at least a memory circuit, an image processing circuit that reads data from the memory circuit and performs image processing, and a display section that displays information output from the image processing circuit.

In the above configuration, the interval between the transducers is equal to the distance for one cycle of the wavelength of the ultrasonic waves. By arranging the transducers in this way, the ultrasonic waves are superimposed and have directivity. In addition, attenuation is suppressed by interfering and strengthening ultrasonic waves.

In addition, one of the configurations disclosed in this specification is a probe having two or more transducers arranged at intervals of one cycle of ultrasonic waves, and each of the two or more transducers and a receiving device. and a plurality of memory circuits connected via circuits, the ultrasound received by the transducer is analog data, and the analog data is held in the memory circuit corresponding to the transducer. .

In the above configuration, the voltage output from one of the two or more oscillators is separated by time and analog data is held in a plurality of memory circuits.

In each of the above structures, the memory circuit includes a transistor including an oxide semiconductor and a capacitor electrically connected to the transistor. By using a transistor including an oxide semiconductor, leakage current in the off state of the transistor can be reduced, and data retention time of the memory circuit can be increased.

If the data held in the memory circuit is read out and image processing is performed to display an image, display can be performed on the display unit. Images displayed on the display unit are black-and-white or color images. Image data obtained by one reception of ultrasonic waves is for one direction (for example, for one line of an image). By transmitting ultrasonic waves in a plurality of directions and combining the obtained image data, one image can be constructed, and by repeating such image processing, moving images can also be obtained. For the transmission of ultrasonic waves, either continuous oscillation or Hals wave transmission may be appropriately selected.

Also, three-dimensional image data can be configured by performing depth calculation processing using a plurality of two-dimensional image data.

Furthermore, an ultrasound image processing system using an AI system can improve the diagnostic imaging performance.

Various operating systems such as Windows (registered trademark), UNIX (registered trademark), and macOS (registered trademark) can be used as the software operating system for constructing the AI system. Software programs are available in Python, Go, Perl, Ruby, Prelog, Visual Basic, C, C++, Swift, Java, . It can be written in various programming languages such as NET. Applications may also be written using frameworks such as Chainer (available in Python), Caffe (available in Python and C++), TensorFlow (available in C, C++, and Python). CNN models require a large amount of convolution processing. Since the convolution process uses a sum-of-products operation, an LSI chip capable of configuring a power-saving sum-of-products operation circuit, particularly an IC chip using a transistor using an oxide semiconductor material, can be used. An IC incorporating an AI system is sometimes called a circuit (microcomputer) that performs neural network operations.

In addition, by inputting regularly obtained data to the neural network unit and performing learning, feature amounts are extracted by calculations in the neural network processing, and image diagnosis performance is improved. Data for learning is stored in an external server using communication functions, neural network processing is performed on an external device, weighting coefficients are calculated, and data is sent from the outside according to the weighting coefficients. A system for controlling an ultrasonic diagnostic apparatus may also be used.

By intentionally causing the ultrasonic waves from a plurality of transducers to interfere with each other, it is possible to acquire sufficient reflected wave data even in the deep part of the human body, because even high frequencies are difficult to attenuate. For example, ultrasound tomographic images (two-dimensional) can be obtained in diagnosing liver, pancreas, and the like.

1 is an ultrasonic diagnostic apparatus showing one embodiment of the present invention. FIG. 2 is a schematic diagram showing how ultrasonic waves interfere with each other according to one embodiment of the present invention. 1 is a block diagram illustrating one aspect of the present invention; FIG. 1 is a block diagram illustrating one aspect of the present invention; FIG. 4 is a flowchart illustrating one aspect of the present invention; 1A and 1B illustrate a memory circuit and a timing chart illustrating one embodiment of the present invention; FIG. 2 is a schematic diagram showing the reflection of multiple substances of ultrasonic transmission; 4A and 4B are schematic cross-sectional views illustrating operation of a semiconductor device; 1A and 1B are schematic cross-sectional views illustrating the structure of a semiconductor device; 1A and 1B are schematic cross-sectional views illustrating the structure of a semiconductor device;

Embodiments of the present invention will be described in detail below with reference to the drawings. However, those skilled in the art will easily understand that the present invention is not limited to the following description, and that the forms and details thereof can be variously changed. Moreover, the present invention should not be construed as being limited to the description of the embodiments shown below.

(Embodiment 1)
FIG. 1A is a perspective view showing an example of the appearance of an ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus has a probe 101, a housing 103, and a display unit 104. The housing 103 contains a power supply, a control circuit, a storage medium for saving data, and other equipment. It has an interface for For data analysis, image processing, etc., it is preferable to provide the housing 103 with a computer in which a program for executing these processes is installed. A program that allows a computer to execute image processing can also be distributed by being stored in a recording medium such as a magnetic disk (hard disk, etc.), an optical disk, a semiconductor memory, or the like. Note that moving means such as wheels may be provided at a plurality of locations on the bottom surface of the ultrasonic diagnostic apparatus.

The ultrasonic diagnostic apparatus shown in FIG. 1A transmits ultrasonic waves from a transducer of a probe 101 (probe) to a biological object to be measured such as a human body, and receives the reflected ultrasonic waves. Then, based on the data, the internal state of the object to be measured is displayed as an image on the display unit 104 . The transducer is a part that transmits and receives ultrasonic waves, and uses a piezoelectric element made of a material having a piezoelectric effect such as PZT (lead zirconate titanate) or PVDF (polyvinylidene fluoride).

FIG. 1B is an enlarged schematic diagram of the probe 101 of the ultrasonic diagnostic apparatus. The size of one vibrator 102 provided in the probe 101 is several tens of μm square, and a plurality of vibrators 102 are arranged in a matrix. The distance between the transducers is preferably matched to the distance of one cycle of the wavelength of the ultrasonic wave to be used. It should be arranged by pitch.

FIG. 2A shows interference when two transducers 102 transmit signals at the same time. FIG. 2B shows how the two transducers 102 transmit ultrasonic waves with slightly different transmission timings. It creates waves that strengthen each other in a specific direction, giving it directivity.

Conventionally, when an ultrasonic wave is given directivity, a plane wave is transmitted so that the ultrasonic wave does not spread. In the present embodiment, ultrasonic waves are intentionally emitted radially and many waves are superimposed to provide directivity, and attenuation can be suppressed by reinforcing each other through interference.

Also, when transmitting, the multiple transducers transmit ultrasonic waves with slightly different timings. By shifting the timing, it controls the interference between ultrasonic waves and transmits ultrasonic waves in a specific direction. During reception, the reflected echoes received by all transducers are converted into voltages and written to the memory. By using as many transducers as possible to receive the ultrasonic waves, the signals received by the transducers can be compared to accurately identify the direction and distance of the object that reflected the ultrasonic waves. can get.

FIG. 3 shows a block diagram from the probe 101 to the display section 104. As shown in FIG. The probe 101 has two or more transducers, and transmits the transmission signal applied from the transmission circuit to the object to be measured as an ultrasonic signal from each transducer, while receiving the ultrasonic echo signal generated in the object to be measured. and output to the receiving circuit as a received signal, which is an electrical signal.

The transmission circuit 105 instructs the probe 101 to transmit a desired ultrasonic wave according to an instruction from the control circuit 109 . The probe 101 irradiates an object to be measured with ultrasonic waves that are caused to interfere with each other from a plurality of transducers. Reflected waves of ultrasonic waves received by the probe 101 are received as analog voltage data, and are held in the memory circuit 107 as analog data. In the present embodiment, since many vibrators 102 are used, a large memory capacity is required. Accurate values can be obtained by using analog data. In addition, since analog data is stored in the analog memory without using a converter or the like, the data can be stored with high power efficiency. The held analog voltage data is sequentially image-processed by the image processing circuit 108 and displayed on the display unit 104 .

A block diagram showing the relationship between the vibrator 102 and the memory circuit 107 is shown in FIG. As shown in FIG. 4, n memories are prepared for n oscillators 102 (where n is a natural number). A plurality of memory cells are prepared for each memory. The analog voltage data output from the vibrator is written to each memory cell divided by time.

Here, FIG. 5 shows an example of a flow chart from transmission of ultrasonic waves to screen display.

As step 1, an ultrasonic wave is transmitted in a certain direction of the object to be measured. In step 2, a reflected wave of the transmitted ultrasonic wave is received. As step 3, the analog voltage data obtained from the reflected wave by the oscillator is written into each memory cell every time. As step 4, the analog voltages written in the memory are read out sequentially or all at once. After reading out, the ultrasound is emitted in another direction of the object. As step 5, the read data is image-processed. AD/DA conversion is also performed as necessary for image processing. As step 6, the image-processed data is displayed on the screen.

Note that the image data obtained by transmitting ultrasonic waves once is for one direction (for example, for one row of an image). A single image is created by combining the image data obtained by transmitting ultrasonic waves in multiple directions. If you repeat this over and over again, it will become a movie. Such image processing can be performed using a microcomputer or the like. Also, an IC (also called an inference chip) incorporating an AI (Artificial Intelligence) system may be used. An IC incorporating an AI system is sometimes called a circuit (microcomputer) that performs neural network operations. When using an IC chip incorporating such an AI system, the system configuration can be simplified. By simplifying the system, the power used for calculation can be reduced, and the power consumption of the system as a whole can be reduced.

FIG. 6A shows a circuit diagram of one analog memory cell. The selection 1 transistor selects the address to write the voltage to the memory. The smaller the voltage write capacity, the shorter the write time and the higher the frame rate. After writing, the transistor of select 2 is opened, read out and image processed. Note that an OS-FET is a transistor whose active layer is an oxide semiconductor containing at least In, Ga, and Zn.

The gate control of the transistors for selection 1 and selection 2 of the memory cell in FIG. 6A will be described below.

Selection 1 is open on memory writes and selection 2 is open on memory reads. For example, if the memory cells in the memory 1 in FIG. 4 are 1-1, 1-2, . )become that way. After selection 1 of memory cell 1-1 is opened and written, when selection 1 is closed, selection 2 of 1-1 is opened and read, and at the same time selection 1 of 1-2 is opened and written. This is repeated in order. In the flow chart of FIG. 5, memory reading is performed after memory writing. Strictly speaking, reading is performed sequentially while writing as shown in the timing chart of FIG. 6(B).

Also, it is preferable that the memory write time is short. For example, as shown in FIG. 7, an echo reflected by a substance 1 in the body is referred to as a reflection 1, and an echo reflected by a substance 2 is referred to as a reflection 2. FIG. When the distance between substance 1 and substance 2 is close, reflection 1 and reflection 2 are reflected almost at the same time, so if the memory write time is long, the two reflections are written together and cannot be distinguished. In order to shorten the write time, the capacity of the circuit in FIG. 6A should be reduced. In that case, since it is necessary to reduce the leakage current of selection 1, it is preferable to employ an OS-FET.

(Embodiment 2)
In this embodiment mode, a structure of a transistor that can be applied to the structure of the semiconductor device described in the above embodiment mode, specifically, a structure in which transistors having different electrical characteristics are stacked to be stacked will be described. In particular, in this embodiment mode, a structure of each transistor included in a memory circuit included in a semiconductor device will be described. With such a structure, the degree of freedom in designing the semiconductor device can be increased. In addition, by stacking transistors having different electrical characteristics, the degree of integration of the semiconductor device can be increased.

A semiconductor device illustrated in FIG. 8 includes a transistor 300 , a transistor 500 , and a capacitor 600 . 10A is a cross-sectional view of the transistor 500 in the channel length direction, FIG. 10B is a cross-sectional view of the transistor 500 in the channel width direction, and FIG. 10C is a cross-sectional view of the transistor 300 in the channel width direction. It is a diagram.

The transistor 500 is a transistor (OS transistor) including a metal oxide in a channel formation region. Since the transistor 500 has a low off-state current, by using the transistor 500 as an OS transistor included in the semiconductor device, written data voltage or electric charge can be held for a long time. In other words, the power consumption of the semiconductor device can be reduced because the frequency of the refresh operation is low or the refresh operation is not required.

A semiconductor device described in this embodiment includes a transistor 300, a transistor 500, and a capacitor 600 as illustrated in FIG. The transistor 500 is provided above the transistor 300 , and the capacitor 600 is provided above the transistors 300 and 500 . Note that the capacitor 600 can be the capacitor Cs in the memory circuit 107 or the like.

The transistor 300 is provided over a substrate 311 and has a conductor 316, an insulator 315, a semiconductor region 313 made of part of the substrate 311, and low-resistance regions 314a and 314b functioning as source or drain regions. . Note that the transistor 300 can be applied to the transistor or the like included in the memory circuit 107 in the above embodiment, for example.

In the transistor 300, as shown in FIG. 10C, a top surface and side surfaces in the channel width direction of a semiconductor region 313 are covered with a conductor 316 with an insulator 315 interposed therebetween. By making the transistor 300 Fin-type in this manner, the effective channel width is increased, so that the on-characteristics of the transistor 300 can be improved. Further, since the contribution of the electric field of the gate electrode can be increased, the off characteristics of the transistor 300 can be improved.

Note that the transistor 300 may be of either p-channel type or n-channel type.

A region in which a channel of the semiconductor region 313 is formed, a region in the vicinity thereof, the low-resistance regions 314a and 314b serving as a source region or a drain region, and the like preferably contain a semiconductor such as a silicon-based semiconductor. It preferably contains crystalline silicon. Alternatively, a material including Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), or the like may be used. A structure using silicon in which the effective mass is controlled by applying stress to the crystal lattice and changing the lattice spacing may be used. Alternatively, the transistor 300 may be a HEMT (High Electron Mobility Transistor) by using GaAs, GaAlAs, or the like.

In the low-resistance regions 314a and 314b, in addition to the semiconductor material applied to the semiconductor region 313, an element imparting n-type conductivity, such as arsenic or phosphorus, or an element imparting p-type conductivity, such as boron, is used. contains elements that

The conductor 316 functioning as a gate electrode is a semiconductor material such as silicon containing an element imparting n-type conductivity such as arsenic or phosphorus or an element imparting p-type conductivity such as boron, a metal material, or an alloy. material, or a conductive material such as a metal oxide material.

Note that since the work function is determined by the material of the conductor, the threshold voltage of the transistor can be adjusted by selecting the material of the conductor. Specifically, it is preferable to use a material such as titanium nitride or tantalum nitride for the conductor. Furthermore, in order to achieve both conductivity and embeddability, it is preferable to use a metal material such as tungsten or aluminum as a laminate for the conductor, and it is particularly preferable to use tungsten from the viewpoint of heat resistance.

Note that the transistor 300 illustrated in FIG. 8 is an example, and the structure thereof is not limited, and an appropriate transistor may be used depending on the circuit configuration and the driving method. For example, in the case where the semiconductor device is a unipolar circuit including only an OS transistor (meaning a transistor with the same polarity as only an n-channel transistor), the transistor 300 is formed using an oxide semiconductor as illustrated in FIG. A structure similar to that of the transistor 500 may be used. Details of the transistor 500 will be described later.

An insulator 320 , an insulator 322 , an insulator 324 , and an insulator 326 are stacked in order to cover the transistor 300 .

For the insulators 320, 322, 324, and 326, for example, silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, aluminum oxide, aluminum oxynitride, aluminum nitride oxide, aluminum nitride, or the like is used. Just do it.

In this specification, silicon oxynitride refers to a material whose composition contains more oxygen than nitrogen, and silicon oxynitride refers to a material whose composition contains more nitrogen than oxygen. indicates In this specification, aluminum oxynitride refers to a material whose composition contains more oxygen than nitrogen, and aluminum oxynitride refers to a material whose composition contains more nitrogen than oxygen. indicates

The insulator 322 may function as a planarization film that planarizes a step caused by the transistor 300 or the like provided therebelow. For example, the top surface of the insulator 322 may be planarized by a chemical mechanical polishing (CMP) method or the like to improve planarity.

For the insulator 324, it is preferable to use a film having a barrier property such that hydrogen or impurities do not diffuse from the substrate 311, the transistor 300, or the like to the region where the transistor 500 is provided.

As an example of a film having a barrier property against hydrogen, silicon nitride formed by a CVD method can be used. Here, diffusion of hydrogen into a semiconductor element including an oxide semiconductor, such as the transistor 500, might degrade the characteristics of the semiconductor element. Therefore, it is preferable to use a film that suppresses diffusion of hydrogen between the transistor 500 and the transistor 300 . Specifically, the film that suppresses diffusion of hydrogen is a film from which the amount of desorption of hydrogen is small.

The desorption amount of hydrogen can be analyzed using, for example, thermal desorption spectroscopy (TDS). For example, the amount of hydrogen released from the insulator 324 is the amount of hydrogen atoms released per area of the insulator 324 when the surface temperature of the film is in the range of 50° C. to 500° C. in TDS analysis. , 10×10 ¹⁵ atoms/cm ² or less, preferably 5×10 ¹⁵ atoms/cm ² or less.

Note that the insulator 326 preferably has a lower dielectric constant than the insulator 324 . For example, the dielectric constant of insulator 326 is preferably less than 4, more preferably less than 3. Also, for example, the dielectric constant of the insulator 326 is preferably 0.7 times or less, more preferably 0.6 times or less, that of the insulator 324 . By using a material with a low dielectric constant as the interlayer film, the parasitic capacitance generated between wirings can be reduced.

In addition, the insulator 320, the insulator 322, the insulator 324, and the insulator 326 are embedded with conductors 328, 330, and the like connected to the capacitor 600 or the transistor 500, respectively. Note that the conductors 328 and 330 function as plugs or wirings. In addition, conductors that function as plugs or wiring may have a plurality of structures collectively given the same reference numerals. Further, in this specification and the like, the wiring and the plug connected to the wiring may be integrated. That is, part of the conductor may function as wiring, and part of the conductor may function as a plug.

As a material for each plug and wiring (conductor 328, conductor 330, etc.), a conductive material such as a metal material, an alloy material, a metal nitride material, or a metal oxide material is used as a single layer or a laminated layer. be able to. It is preferable to use a high-melting-point material such as tungsten or molybdenum that has both heat resistance and conductivity, and it is preferable to use tungsten. Alternatively, it is preferably made of a low resistance conductive material such as aluminum or copper. Wiring resistance can be reduced by using a low-resistance conductive material.

A wiring layer may be provided over the insulator 326 and the conductor 330 . For example, in FIG. 8, an insulator 350, an insulator 352, and an insulator 354 are stacked in this order. A conductor 356 is formed over the insulators 350 , 352 , and 354 . The conductor 356 functions as a plug or wiring connected to the transistor 300 . Note that the conductor 356 can be provided using a material similar to that of the conductors 328 and 330 .

Note that for the insulator 350 , for example, an insulator having a barrier property against hydrogen is preferably used, like the insulator 324 . Further, the conductor 356 preferably contains a conductor having a barrier property against hydrogen. In particular, a conductor having a barrier property against hydrogen is formed in the opening of the insulator 350 having a barrier property against hydrogen. With this structure, the transistor 300 and the transistor 500 can be separated by a barrier layer, and diffusion of hydrogen from the transistor 300 to the transistor 500 can be suppressed.

Note that tantalum nitride or the like may be used as the conductor having a barrier property against hydrogen, for example. Further, by stacking tantalum nitride and tungsten having high conductivity, diffusion of hydrogen from the transistor 300 can be suppressed while the conductivity of the wiring is maintained. In this case, it is preferable that the tantalum nitride layer having a barrier property against hydrogen be in contact with the insulator 350 having a barrier property against hydrogen.

A wiring layer may be provided over the insulator 354 and the conductor 356 . For example, in FIG. 8, an insulator 360, an insulator 362, and an insulator 364 are stacked in order. A conductor 366 is formed over the insulators 360 , 362 , and 364 . The conductor 366 functions as a plug or wiring. Note that the conductor 366 can be provided using a material similar to that of the conductors 328 and 330 .

Note that for the insulator 360, for example, an insulator having a barrier property against hydrogen is preferably used, like the insulator 324. Further, the conductor 366 preferably contains a conductor having a barrier property against hydrogen. In particular, a conductor having a barrier property against hydrogen is formed in the opening of the insulator 360 having a barrier property against hydrogen. With this structure, the transistor 300 and the transistor 500 can be separated by a barrier layer, and diffusion of hydrogen from the transistor 300 to the transistor 500 can be suppressed.

A wiring layer may be provided over the insulator 364 and the conductor 366 . For example, in FIG. 8, an insulator 370, an insulator 372, and an insulator 374 are stacked in this order. A conductor 376 is formed over the insulators 370 , 372 , and 374 . The conductor 376 functions as a plug or wiring. Note that the conductor 376 can be provided using a material similar to that of the conductors 328 and 330 .

Note that for the insulator 370, for example, an insulator having a barrier property against hydrogen is preferably used like the insulator 324. Further, the conductor 376 preferably contains a conductor having a barrier property against hydrogen. In particular, a conductor having a barrier property against hydrogen is formed in the opening of the insulator 370 having a barrier property against hydrogen. With this structure, the transistor 300 and the transistor 500 can be separated by a barrier layer, and diffusion of hydrogen from the transistor 300 to the transistor 500 can be suppressed.

A wiring layer may be provided over the insulator 374 and the conductor 376 . For example, in FIG. 8, an insulator 380, an insulator 382, and an insulator 384 are stacked in order. A conductor 386 is formed over the insulators 380 , 382 , and 384 . The conductor 386 functions as a plug or wiring. Note that the conductor 386 can be provided using a material similar to that of the conductors 328 and 330 .

Note that for the insulator 380, for example, an insulator having a barrier property against hydrogen is preferably used like the insulator 324. Further, the conductor 386 preferably contains a conductor having a barrier property against hydrogen. In particular, a conductor having a barrier property against hydrogen is formed in the opening of the insulator 380 having a barrier property against hydrogen. With this structure, the transistor 300 and the transistor 500 can be separated by a barrier layer, and diffusion of hydrogen from the transistor 300 to the transistor 500 can be suppressed.

The wiring layer including the conductor 356, the wiring layer including the conductor 366, the wiring layer including the conductor 376, and the wiring layer including the conductor 386 are described above. It is not limited to this. The number of wiring layers similar to the wiring layer including the conductor 356 may be three or less, or the number of wiring layers similar to the wiring layer including the conductor 356 may be five or more.

An insulator 510 , an insulator 512 , an insulator 514 , and an insulator 516 are stacked in this order over the insulator 384 . Any of the insulator 510, the insulator 512, the insulator 514, and the insulator 516 is preferably a substance having barrier properties against oxygen and hydrogen.

For the insulators 510 and 514, for example, a film having barrier properties such that hydrogen or impurities do not diffuse from the substrate 311 or a region where the transistor 300 is provided to a region where the transistor 500 is provided is used. is preferred. Therefore, a material similar to that of the insulator 324 can be used.

As an example of a film having a barrier property against hydrogen, silicon nitride formed by a CVD method can be used. Here, diffusion of hydrogen into a semiconductor element including an oxide semiconductor, such as the transistor 500, might degrade the characteristics of the semiconductor element. Therefore, it is preferable to use a film that suppresses diffusion of hydrogen between the transistor 500 and the transistor 300 . Specifically, the film that suppresses diffusion of hydrogen is a film from which the amount of desorption of hydrogen is small.

As a film having a barrier property against hydrogen, for example, the insulators 510 and 514 are preferably formed using a metal oxide such as aluminum oxide, hafnium oxide, or tantalum oxide.

In particular, aluminum oxide has a high shielding effect of preventing the penetration of both oxygen and impurities such as hydrogen and moisture, which cause variations in the electrical characteristics of the transistor. Therefore, aluminum oxide can prevent impurities such as hydrogen and moisture from entering the transistor 500 during and after the manufacturing process of the transistor. In addition, release of oxygen from the oxide forming the transistor 500 can be suppressed. Therefore, it is suitable for use as a protective film for the transistor 500 .

Further, for example, the insulators 512 and 516 can be formed using a material similar to that of the insulator 320 . In addition, by using a material with a relatively low dielectric constant for these insulators, parasitic capacitance generated between wirings can be reduced. For example, the insulators 512 and 516 can be formed using a silicon oxide film, a silicon oxynitride film, or the like.

In addition, the insulator 510 , the insulator 512 , the insulator 514 , and the insulator 516 are embedded with a conductor 518 , a conductor forming the transistor 500 (eg, the conductor 503 ), and the like. Note that the conductor 518 functions as a plug or wiring that is connected to the capacitor 600 or the transistor 300 . The conductor 518 can be provided using a material similar to that of the conductors 328 and 330 .

In particular, a conductor 518 in a region in contact with the insulator 510 and the insulator 514 is preferably a conductor having barrier properties against oxygen, hydrogen, and water. With this structure, the transistor 300 and the transistor 500 can be separated by a layer having barrier properties against oxygen, hydrogen, and water, and diffusion of hydrogen from the transistor 300 to the transistor 500 can be suppressed.

A transistor 500 is provided above the insulator 516 .

As shown in FIGS. 10A and 10B, the transistor 500 is provided with a conductor 503 embedded in insulators 514 and 516 and over the insulators 516 and 503 . Insulator 520, insulator 522 over insulator 520, insulator 524 over insulator 522, oxide 530a over insulator 524, and oxide 530a an oxide 530b overlying a conductor 542a and a conductor 542b spaced apart from each other over the oxide 530b; An insulator 580 with an opening overlapping between them, an oxide 530c arranged on the bottom and side surfaces of the opening, an insulator 550 arranged on the formation surface of the oxide 530c, and an insulator 550 are formed. and a conductor 560 disposed on the surface.

In addition, an insulator 544 is preferably provided between the oxide 530a, the oxide 530b, the conductors 542a and 542b, and the insulator 580 as illustrated in FIGS. . 10A and 10B, the conductor 560 includes a conductor 560a provided inside the insulator 550 and a conductor 560b embedded inside the conductor 560a. and preferably. Further, an insulator 574 is preferably provided over the insulator 580, the conductor 560, and the insulator 550 as shown in FIGS.

Note that the oxide 530a, the oxide 530b, and the oxide 530c are collectively referred to as the oxide 530 in some cases below.

Note that although the transistor 500 has a structure in which three layers of the oxide 530a, the oxide 530b, and the oxide 530c are stacked in a region where a channel is formed and in the vicinity thereof, the present invention is limited to this. not a thing For example, a single layer of the oxide 530b, a two-layer structure of the oxides 530b and 530a, a two-layer structure of the oxides 530b and 530c, or a stacked structure of four or more layers may be employed. Although the conductor 560 has a two-layer structure in the transistor 500, the present invention is not limited to this. For example, the conductor 560 may have a single-layer structure or a laminated structure of three or more layers. Further, the transistor 500 illustrated in FIGS. 8 and 10A is only an example, and the structure is not limited, and an appropriate transistor may be used depending on the circuit structure and driving method.

Here, the conductor 560 functions as a gate electrode of the transistor, and the conductors 542a and 542b function as source and drain electrodes, respectively. As described above, the conductor 560 is formed to be embedded in the opening of the insulator 580 and the region sandwiched between the conductors 542a and 542b. The placement of conductor 560 , conductor 542 a and conductor 542 b is selected in a self-aligned manner with respect to the opening in insulator 580 . That is, in the transistor 500, the gate electrode can be arranged between the source electrode and the drain electrode in a self-aligned manner. Therefore, the conductor 560 can be formed without providing an alignment margin, so that the area occupied by the transistor 500 can be reduced. As a result, miniaturization and high integration of the semiconductor device can be achieved.

Furthermore, since conductor 560 is formed in a region between conductors 542a and 542b in a self-aligned manner, conductor 560 does not have a region that overlaps conductors 542a or 542b. Accordingly, parasitic capacitance formed between the conductor 560 and the conductors 542a and 542b can be reduced. Therefore, the switching speed of the transistor 500 can be improved and high frequency characteristics can be obtained.

Conductor 560 may function as a first gate (also called top gate) electrode. In some cases, the conductor 503 functions as a second gate (also referred to as a bottom gate) electrode. In that case, the threshold voltage of the transistor 500 can be controlled by changing the potential applied to the conductor 503 independently of the potential applied to the conductor 560 . In particular, by applying a negative potential to the conductor 503, the threshold voltage of the transistor 500 can be made higher than 0 V and the off current can be reduced. Therefore, when a negative potential is applied to the conductor 503, the drain current when the potential applied to the conductor 560 is 0 V can be made smaller than when no potential is applied.

The conductor 503 is arranged so as to overlap with the oxide 530 and the conductor 560 . Accordingly, when a potential is applied to the conductor 560 and the conductor 503, the electric field generated from the conductor 560 and the electric field generated from the conductor 503 are connected to each other, so that the channel formation region formed in the oxide 530 is covered. can be done. In this specification and the like, a transistor structure in which a channel formation region is electrically surrounded by electric fields of a first gate electrode and a second gate electrode is referred to as a surrounded channel (S-channel) structure.

The conductor 503 has the same structure as the conductor 518. A conductor 503a is formed in contact with the inner walls of the openings of the insulators 514 and 516, and a conductor 503b is formed inside. Note that although the structure in which the conductors 503a and 503b are stacked is shown in the transistor 500, the present invention is not limited to this. For example, the conductor 503 may be provided as a single layer or a laminated structure of three or more layers.

Here, for the conductor 503a, it is preferable to use a conductive material that has a function of suppressing diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, and copper atoms (the impurities are less likely to permeate). Alternatively, it is preferable to use a conductive material that has a function of suppressing diffusion of oxygen (eg, at least one of oxygen atoms, oxygen molecules, etc.) (the above oxygen is difficult to permeate). In this specification, the function of suppressing the diffusion of impurities or oxygen means the function of suppressing the diffusion of one or all of the impurities or oxygen.

For example, since the conductor 503a has a function of suppressing the diffusion of oxygen, it is possible to suppress a decrease in conductivity due to oxidation of the conductor 503b.

In the case where the conductor 503 also functions as a wiring, the conductor 503b is preferably made of a highly conductive material containing tungsten, copper, or aluminum as its main component. In that case, the conductor 505 is not necessarily provided. Note that although the conductor 503b is illustrated as a single layer, it may have a layered structure, for example, a layered layer of titanium, titanium nitride, and any of the above conductive materials.

The insulator 520, the insulator 522, the insulator 524, and the insulator 550 function as a second gate insulating film.

Here, the insulator 524 in contact with the oxide 530 preferably contains more oxygen than the stoichiometric composition. In other words, the insulator 524 preferably has an excess oxygen region. By providing such an insulator containing excess oxygen in contact with the oxide 530, oxygen vacancies in the oxide 530 can be reduced and the reliability of the transistor 500 can be improved.

Specifically, an oxide material from which part of oxygen is released by heating is preferably used as the insulator having the excess oxygen region. The oxide that desorbs oxygen by heating means that the desorption amount of oxygen in terms of oxygen atoms is 1.0×10 ¹⁸ atoms/cm ³ or more, preferably 1, in TDS (Thermal Desorption Spectroscopy) analysis. 0×10 ¹⁹ atoms/cm ³ or more, more preferably 2.0×10 ¹⁹ atoms/cm ³ or more, or 3.0×10 ²⁰ atoms/cm ³ or more. The surface temperature of the film during the TDS analysis is preferably in the range of 100° C. or higher and 700° C. or lower, or 100° C. or higher and 400° C. or lower.

In addition, when the insulator 524 has an excess oxygen region, the insulator 522 preferably has a function of suppressing diffusion of oxygen (eg, oxygen atoms, oxygen molecules, etc.) (the above oxygen is difficult to permeate).

Since the insulator 522 has a function of suppressing diffusion of oxygen and impurities, oxygen contained in the oxide 530 does not diffuse toward the insulator 520, which is preferable. In addition, the conductor 503 can be prevented from reacting with oxygen contained in the insulator 524 and the oxide 530 .

The insulator 522 is, for example, aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), tantalum oxide, zirconium oxide, lead zirconate titanate (PZT), strontium titanate ( _SrTiO3 ), or It is preferable to use an insulator containing a so-called high-k material such as (Ba,Sr)TiO ₃ (BST) in a single layer or a laminated layer. As transistors are miniaturized and highly integrated, thinning of gate insulating films may cause problems such as leakage current. By using a high-k material for the insulator that functions as the gate insulating film, it is possible to reduce the gate potential during transistor operation while maintaining the physical film thickness.

In particular, an insulator containing an oxide of one or both of aluminum and hafnium, which is an insulating material having a function of suppressing diffusion of impurities and oxygen (through which oxygen is difficult to permeate), is preferably used. As the insulator containing oxides of one or both of aluminum and hafnium, aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), or the like is preferably used. When the insulator 522 is formed using such a material, the insulator 522 suppresses release of oxygen from the oxide 530 and entry of impurities such as hydrogen from the periphery of the transistor 500 into the oxide 530. act as a layer.

Alternatively, aluminum oxide, bismuth oxide, germanium oxide, niobium oxide, silicon oxide, titanium oxide, tungsten oxide, yttrium oxide, or zirconium oxide may be added to these insulators. Alternatively, these insulators may be nitrided. Silicon oxide, silicon oxynitride, or silicon nitride may be stacked over the above insulator.

Insulator 520 is also preferably thermally stable. For example, silicon oxide and silicon oxynitride are preferred because they are thermally stable. Further, by combining an insulator made of a high-k material with silicon oxide or silicon oxynitride, the insulators 520 and 526 having a stacked structure which are thermally stable and have a high relative dielectric constant can be obtained.

Note that in the transistor 500 in FIGS. 10A and 10B, the insulator 520, the insulator 522, and the insulator 524 are illustrated as the second gate insulating film having a stacked-layer structure of three layers. The second gate insulating film may have a single layer, two layers, or a laminated structure of four or more layers. In that case, it is not limited to a laminated structure made of the same material, and a laminated structure made of different materials may be used.

In the transistor 500, a metal oxide functioning as an oxide semiconductor is preferably used for the oxide 530 including a channel formation region. For example, as the oxide 530, In-M-Zn oxide (element M is aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium , hafnium, tantalum, tungsten, magnesium, or the like) may be used. Particularly, the In-M-Zn oxide that can be applied as the oxide 530 is preferably CAAC-OS (c-axis aligned crystalline oxide semiconductor) or CAC-OS (Cloud-Aligned Composite Oxide Semiconductor). CAAC-OS refers to an oxide having a CAAC structure, and the CAAC structure is a crystal structure in which a plurality of IGZO nanocrystals have a c-axis orientation and are connected without being oriented in the ab plane. is. A CAC-OS is, for example, one structure of a material in which elements constituting a metal oxide are unevenly distributed with a size of 0.5 nm or more and 10 nm or less, preferably 1 nm or more and 2 nm or less, or in the vicinity thereof. In the following description, one or more metal elements are unevenly distributed in the metal oxide, and the region having the metal element has a size of 0.5 nm or more and 10 nm or less, preferably 1 nm or more and 2 nm or less, or a size in the vicinity thereof. The mixed state is also called a mosaic shape or a patch shape. Alternatively, as the oxide 530, an In--Ga oxide or an In--Zn oxide may be used.

A metal oxide with a low carrier concentration is preferably used for the transistor 500 . In the case of lowering the carrier concentration of the metal oxide, the impurity concentration in the metal oxide should be lowered to lower the defect level density. In this specification and the like, a low impurity concentration and a low defect level density are referred to as high-purity intrinsic or substantially high-purity intrinsic. Impurities in metal oxides include, for example, hydrogen, nitrogen, alkali metals, alkaline earth metals, iron, nickel, and silicon.

In particular, hydrogen contained in the metal oxide reacts with oxygen bound to the metal atom to form water, which may cause oxygen vacancies in the metal oxide. If the channel formation region in the metal oxide contains oxygen vacancies, the transistor may have normally-on characteristics. Furthermore, a defect in which hydrogen is added to an oxygen vacancy functions as a donor, and an electron, which is a carrier, may be generated. In addition, part of hydrogen may bond with oxygen that bonds with a metal atom to generate an electron that is a carrier. Therefore, a transistor using a metal oxide containing a large amount of hydrogen tends to have normally-on characteristics.

Defects with hydrogen in oxygen vacancies can function as donors for metal oxides. However, it is difficult to quantitatively evaluate the defects. Therefore, metal oxides are sometimes evaluated not by the donor concentration but by the carrier concentration. Therefore, in this specification and the like, instead of the donor concentration, the carrier concentration assuming a state in which no electric field is applied may be used as a parameter of the metal oxide. In other words, the “carrier concentration” described in this specification and the like may be rephrased as “donor concentration”.

Therefore, when a metal oxide is used for the oxide 530, hydrogen in the metal oxide is preferably reduced as much as possible. Specifically, in the metal oxide, the hydrogen concentration obtained by secondary ion mass spectrometry (SIMS) is less than 1×10 ²⁰ atoms/cm ³ , preferably 1×10 ¹⁹ atoms/cm It is less than ³ , more preferably less than 5×10 ¹⁸ atoms/cm ³ , still more preferably less than 1×10 ¹⁸ atoms/cm ³ . By using a metal oxide in which impurities such as hydrogen are sufficiently reduced for a channel formation region of a transistor, stable electrical characteristics can be imparted.

Further, when a metal oxide is used for the oxide 530, the carrier concentration of the metal oxide with the channel formation region is preferably 1×10 ¹⁸ cm ⁻³ or less, and is less than 1×10 ¹⁷ cm ⁻³ . is more preferably less than 1×10 ¹⁶ cm ⁻³ , still more preferably less than 1×10 ¹³ cm ⁻³ , even more preferably less than 1×10 ¹² cm ⁻³ . Although there is no particular limitation on the lower limit of the carrier concentration of the metal oxide in the channel forming region, it can be, for example, 1×10 ⁻⁹ cm ⁻³ .

In the case where a metal oxide is used for the oxide 530, the conductors 542 (the conductors 542a and 542b) are in contact with the oxide 530, whereby oxygen in the oxide 530 diffuses into the conductor 542. Conductor 542 may oxidize. Oxidation of the conductor 542 is highly likely to reduce the conductivity of the conductor 542 . Note that diffusion of oxygen in the oxide 530 to the conductor 542 can be rephrased as that the conductor 542 absorbs oxygen in the oxide 530 .

Further, oxygen in the oxide 530 diffuses into the conductor 542 (the conductor 542a and the conductor 542b), so that the conductor 542a and the oxide 530b and the conductor 542b and the oxide 530b are diffused. Different layers may form between them. Since the different layer contains more oxygen than the conductor 542, the different layer is presumed to have insulating properties. At this time, the three-layer structure of the conductor 542, the different layer, and the oxide 530b can be regarded as a three-layer structure composed of metal-insulator-semiconductor, and is called a metal-insulator-semiconductor (MIS) structure. Alternatively, it may be called a diode junction structure mainly composed of the MIS structure.

Note that the different layer is not limited to being formed between the conductor 542 and the oxide 530b. It may form between body 542 and oxide 530b and between conductor 542 and oxide 530c.

Further, it is preferable that a metal oxide which functions as a channel formation region in the oxide 530 has a bandgap of 2 eV or more, preferably 2.5 eV or more. By using a metal oxide with a large bandgap in this manner, off-state current of a transistor can be reduced.

Since the oxide 530 includes the oxide 530a under the oxide 530b, diffusion of impurities from a structure formed below the oxide 530a to the oxide 530b can be suppressed. In addition, by providing the oxide 530c over the oxide 530b, diffusion of impurities from a structure formed above the oxide 530c to the oxide 530b can be suppressed.

Note that the oxide 530 preferably has a layered structure with oxides having different atomic ratios of metal atoms. Specifically, in the metal oxide used for the oxide 530a, the atomic number ratio of the element M among the constituent elements is greater than the atomic number ratio of the element M among the constituent elements in the metal oxide used for the oxide 530b. is preferred. Further, in the metal oxide used for the oxide 530a, the atomic ratio of the element M to In is preferably higher than the atomic ratio of the element M to In in the metal oxide used for the oxide 530b. In addition, the atomic ratio of In to the element M in the metal oxide used for the oxide 530b is preferably higher than the atomic ratio of In to the element M in the metal oxide used for the oxide 530a. In addition, the oxide 530c can be a metal oxide that can be used for the oxide 530a or the oxide 530b.

In addition, it is preferable that the energies of the conduction band bottoms of the oxides 530a and 530c be higher than the energies of the conduction band bottoms of the oxide 530b. In other words, the electron affinities of the oxides 530a and 530c are preferably smaller than that of the oxide 530b.

Here, the energy level at the bottom of the conduction band changes smoothly at the junction of the oxide 530a, the oxide 530b, and the oxide 530c. In other words, it can be said that the energy level of the bottom of the conduction band at the junction of the oxide 530a, the oxide 530b, and the oxide 530c continuously changes or continuously joins. In order to achieve this, the defect level density of the mixed layers formed at the interface between the oxides 530a and 530b and the interface between the oxides 530b and 530c should be lowered.

Specifically, the oxide 530a and the oxide 530b, and the oxide 530b and the oxide 530c have a common element (main component) other than oxygen, thereby forming a mixed layer with a low defect level density. be able to. For example, when the oxide 530b is an In--Ga--Zn oxide, the oxides 530a and 530c may be In--Ga--Zn oxide, Ga--Zn oxide, gallium oxide, or the like.

At this time, the main path of carriers is the oxide 530b. When the oxides 530a and 530c have the above structure, defect level densities at the interfaces between the oxides 530a and 530b and between the oxides 530b and 530c can be reduced. Therefore, the influence of interface scattering on carrier conduction is reduced, and the transistor 500 can obtain a high on-state current.

Conductors 542a and 542b functioning as source and drain electrodes are provided over the oxide 530b. Conductors 542a and 542b include aluminum, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tungsten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, indium, and ruthenium. , iridium, strontium, and lanthanum, an alloy containing the above-described metal elements as a component, or an alloy in which the above-described metal elements are combined. For example, tantalum nitride, titanium nitride, tungsten, nitride containing titanium and aluminum, nitride containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, oxide containing strontium and ruthenium, oxide containing lanthanum and nickel, and the like are used. is preferred. Also, tantalum nitride, titanium nitride, nitrides containing titanium and aluminum, nitrides containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, oxides containing strontium and ruthenium, and oxides containing lanthanum and nickel are difficult to oxidize. It is preferable because it is a conductive material or a material that maintains conductivity even after absorbing oxygen. Furthermore, a metal nitride film such as tantalum nitride is preferable because it has a barrier property against hydrogen or oxygen.

In addition, although the conductor 542a and the conductor 542b have a single-layer structure in FIGS. 10A and 10B, they may have a stacked structure of two or more layers. For example, a tantalum nitride film and a tungsten film are preferably stacked. Alternatively, a titanium film and an aluminum film may be stacked. A two-layer structure in which an aluminum film is stacked over a tungsten film, a two-layer structure in which a copper film is stacked over a copper-magnesium-aluminum alloy film, a two-layer structure in which a copper film is stacked over a titanium film, a two-layer structure in which a copper film is stacked over a titanium film, A two-layer structure in which copper films are stacked may be used.

Further, a three-layer structure in which a titanium film or a titanium nitride film is laminated, an aluminum film or a copper film is laminated on the titanium film or the titanium nitride film, and a titanium film or a titanium nitride film is formed thereon, a molybdenum film or a There is a three-layer structure including a molybdenum nitride film, an aluminum film or a copper film laminated on the molybdenum film or the molybdenum nitride film, and a molybdenum film or a molybdenum nitride film formed thereon. Note that a transparent conductive material containing indium oxide, tin oxide, or zinc oxide may be used.

Further, as shown in FIG. 10A, regions 543a and 543b are formed as low-resistance regions at the interface between the oxide 530 and the conductor 542a (conductor 542b) and in the vicinity thereof. There is At this time, the region 543a functions as one of the source region and the drain region, and the region 543b functions as the other of the source region and the drain region. A channel formation region is formed in a region sandwiched between the regions 543a and 543b.

By providing the conductor 542a (the conductor 542b) so as to be in contact with the oxide 530, the oxygen concentration of the region 543a (the region 543b) may be reduced. In some cases, a metal compound layer containing the metal contained in the conductor 542a (conductor 542b) and the component of the oxide 530 is formed in the region 543a (region 543b). In such a case, the carrier concentration of the region 543a (region 543b) increases and the region 543a (region 543b) becomes a low resistance region.

The insulator 544 is provided so as to cover the conductors 542a and 542b and suppress oxidation of the conductors 542a and 542b. At this time, the insulator 544 may be provided so as to cover the side surface of the oxide 530 and be in contact with the insulator 524 .

The insulator 544 is a metal oxide containing one or more selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, neodymium, lanthanum, magnesium, and the like. can be used. Alternatively, silicon nitride oxide, silicon nitride, or the like can be used as the insulator 544 .

In particular, as the insulator 544, an insulator containing one or both oxides of aluminum and hafnium, such as aluminum oxide, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate), is preferably used. . In particular, hafnium aluminate has higher heat resistance than hafnium oxide film. Therefore, it is preferable because it is less likely to be crystallized in heat treatment in a later step. Note that the insulator 544 is not essential when the conductors 542a and 542b are made of an oxidation-resistant material or when the conductivity does not significantly decrease even when oxygen is absorbed. It may be appropriately designed depending on the required transistor characteristics.

The insulator 544 can suppress diffusion of impurities such as water and hydrogen contained in the insulator 580 through the oxide 530c and the insulator 550 into the oxide 530b. In addition, oxidation of the conductor 560 due to excess oxygen in the insulator 580 can be suppressed.

The insulator 550 functions as a first gate insulating film. The insulator 550 is preferably placed in contact with the inside (top and side surfaces) of the oxide 530c. The insulator 550 is preferably formed using an insulator that contains excess oxygen and releases oxygen by heating, similarly to the insulator 524 described above.

Specifically, silicon oxide containing excess oxygen, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide to which fluorine is added, silicon oxide to which carbon is added, silicon oxide to which carbon and nitrogen are added, and vacancies are can be used. In particular, silicon oxide and silicon oxynitride are preferable because they are stable against heat.

By providing an insulator from which oxygen is released by heating as the insulator 550 in contact with the top surface of the oxide 530c, oxygen is effectively introduced from the insulator 550 to the channel formation region of the oxide 530b through the oxide 530c. can be supplied. Further, similarly to the insulator 524, the concentration of impurities such as water or hydrogen in the insulator 550 is preferably reduced. The thickness of the insulator 550 is preferably 1 nm or more and 20 nm or less.

Further, a metal oxide may be provided between the insulator 550 and the conductor 560 in order to efficiently supply excess oxygen contained in the insulator 550 to the oxide 530 . The metal oxide preferably suppresses diffusion of oxygen from the insulator 550 to the conductor 560 . By providing the metal oxide that suppresses diffusion of oxygen, diffusion of excess oxygen from the insulator 550 to the conductor 560 is suppressed. That is, reduction in the amount of excess oxygen supplied to the oxide 530 can be suppressed. In addition, oxidation of the conductor 560 due to excess oxygen can be suppressed. As the metal oxide, a material that can be used for the insulator 544 may be used.

Note that the insulator 550 may have a stacked structure similarly to the second gate insulating film. As transistors are miniaturized and highly integrated, thinning of the gate insulating film may cause problems such as leakage current. By forming a laminated structure with a material that is relatively stable, it is possible to reduce the gate potential during transistor operation while maintaining the physical film thickness. Moreover, it is possible to obtain a laminated structure that is thermally stable and has a high dielectric constant.

Although the conductor 560 functioning as the first gate electrode has a two-layer structure in FIGS. 10A and 10B, it may have a single-layer structure or a stacked structure of three or more layers.

The conductor 560a has a function of suppressing diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (such as N ₂ O, NO, NO ₂ ), and copper atoms. Materials are preferably used. Alternatively, a conductive material having a function of suppressing diffusion of oxygen (eg, at least one of oxygen atoms and oxygen molecules) is preferably used. Since the conductor 560a has a function of suppressing diffusion of oxygen, oxygen contained in the insulator 550 can suppress oxidation of the conductor 560b and a decrease in conductivity. As the conductive material having a function of suppressing diffusion of oxygen, tantalum, tantalum nitride, ruthenium, ruthenium oxide, or the like is preferably used, for example. Further, an oxide semiconductor that can be used for the oxide 530 can be used as the conductor 560a. In that case, by forming the conductor 560b by a sputtering method, the electric resistance value of the conductor 560a can be lowered to make the conductor 560a a conductor. This can be called an OC (Oxide Conductor) electrode.

A conductive material containing tungsten, copper, or aluminum as its main component is preferably used for the conductor 560b. In addition, since the conductor 560b also functions as a wiring, a conductor with high conductivity is preferably used. For example, a conductive material whose main component is tungsten, copper, or aluminum can be used. Further, the conductor 560b may have a layered structure, for example, a layered structure of titanium, titanium nitride, and the above conductive materials.

The insulator 580 is provided over the conductors 542a and 542b with the insulator 544 interposed therebetween. Insulator 580 preferably has excess oxygen regions. For example, the insulator 580 may be silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide to which fluorine is added, silicon oxide to which carbon is added, silicon oxide to which carbon and nitrogen are added, or oxide with vacancies. It preferably contains silicon, resin, or the like. In particular, silicon oxide and silicon oxynitride are preferable because they are thermally stable. In particular, silicon oxide and silicon oxide having vacancies are preferable because an excess oxygen region can be easily formed in a later step.

Insulator 580 preferably has excess oxygen regions. By providing the insulator 580 from which oxygen is released by heating in contact with the oxide 530c, oxygen in the insulator 580 can be efficiently supplied to the oxide 530 through the oxide 530c. Note that the concentration of impurities such as water or hydrogen in the insulator 580 is preferably low.

The opening of the insulator 580 is formed so as to overlap a region between the conductors 542a and 542b. Thus, the conductor 560 is formed so as to be embedded in the opening of the insulator 580 and the region sandwiched between the conductors 542a and 542b.

When miniaturizing a semiconductor device, it is required to shorten the gate length, but it is necessary to prevent the conductivity of the conductor 560 from being lowered. Therefore, when the film thickness of the conductor 560 is increased, the conductor 560 can have a shape with a high aspect ratio. In this embodiment mode, since the conductor 560 is embedded in the opening of the insulator 580, the conductor 560 can be formed without collapsing during the process even if the conductor 560 has a high aspect ratio. can be done.

The insulator 574 is preferably provided in contact with the top surface of the insulator 580 , the top surface of the conductor 560 , and the top surface of the insulator 550 . By forming the insulator 574 by a sputtering method, excess oxygen regions can be provided in the insulators 550 and 580 . Accordingly, oxygen can be supplied into the oxide 530 from the excess oxygen region.

For example, the insulator 574 can be a metal oxide containing one or more selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, magnesium, and the like. can be done.

In particular, aluminum oxide has a high barrier property and can suppress diffusion of hydrogen and nitrogen even in a thin film having a thickness of 0.5 nm or more and 3.0 nm or less. Therefore, the aluminum oxide film formed by the sputtering method can function not only as an oxygen supply source but also as a barrier film against impurities such as hydrogen.

An insulator 581 functioning as an interlayer film is preferably provided over the insulator 574 . The insulator 581 preferably has a reduced concentration of impurities such as water or hydrogen in the film, similarly to the insulator 524 and the like.

In addition, conductors 540 a and 540 b are provided in openings formed in the insulators 581 , 574 , 580 , and 544 . The conductor 540a and the conductor 540b are provided to face each other with the conductor 560 interposed therebetween. The conductors 540a and 540b have the same structure as the conductors 546 and 548, which are described later.

An insulator 582 is provided over the insulator 581 . It is preferable that the insulator 582 use a substance that has a barrier property against oxygen and hydrogen. Therefore, a material similar to that of the insulator 514 can be used for the insulator 582 . For example, the insulator 582 is preferably formed using a metal oxide such as aluminum oxide, hafnium oxide, or tantalum oxide.

In particular, aluminum oxide has a high shielding effect of preventing the penetration of both oxygen and impurities such as hydrogen and moisture, which cause variations in the electrical characteristics of the transistor. Therefore, aluminum oxide can prevent impurities such as hydrogen and moisture from entering the transistor 500 during and after the manufacturing process of the transistor. In addition, release of oxygen from the oxide forming the transistor 500 can be suppressed. Therefore, it is suitable for use as a protective film for the transistor 500 .

An insulator 586 is provided over the insulator 582 . A material similar to that of the insulator 320 can be used for the insulator 586 . In addition, by using a material with a relatively low dielectric constant for these insulators, parasitic capacitance generated between wirings can be reduced. For example, a silicon oxide film, a silicon oxynitride film, or the like can be used as the insulator 586 .

In addition, the insulator 520, the insulator 522, the insulator 524, the insulator 544, the insulator 580, the insulator 574, the insulator 581, the insulator 582, and the insulator 586 include the conductor 546, the conductor 548, and the like. is embedded.

The conductors 546 and 548 function as plugs or wirings that connect to the capacitor 600 , the transistor 500 , or the transistor 300 . The conductors 546 and 548 can be formed using a material similar to that of the conductors 328 and 330 .

Next, a capacitor 600 is provided above the transistor 500 . A capacitor 600 includes a conductor 610 , a conductor 620 , and an insulator 630 .

A conductor 612 may be provided over the conductor 546 and the conductor 548 . The conductor 612 functions as a plug or wiring connected to the transistor 500 . The conductor 610 functions as an electrode of the capacitor 600 . Note that the conductor 612 and the conductor 610 can be formed at the same time.

The conductors 612 and 610 are metal films containing elements selected from molybdenum, titanium, tantalum, tungsten, aluminum, copper, chromium, neodymium, and scandium, or metal nitride films containing any of the above elements. (tantalum nitride film, titanium nitride film, molybdenum nitride film, tungsten nitride film) or the like can be used. Alternatively, indium tin oxide, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium zinc oxide, and silicon oxide are added. Conductive materials such as indium tin oxide can also be applied.

Although the conductors 612 and 610 each have a single-layer structure in FIGS. 8A and 8B, they are not limited to this structure and may have a stacked structure of two or more layers. For example, between a conductor with barrier properties and a conductor with high conductivity, a conductor with barrier properties and a conductor with high adhesion to the conductor with high conductivity may be formed.

A conductor 620 is provided so as to overlap with the conductor 610 with an insulator 630 interposed therebetween. Note that a conductive material such as a metal material, an alloy material, or a metal oxide material can be used for the conductor 620 . It is preferable to use a high-melting-point material such as tungsten or molybdenum that has both heat resistance and conductivity, and it is particularly preferable to use tungsten. In addition, when forming simultaneously with another structure such as a conductor, a low-resistance metal material such as Cu (copper) or Al (aluminum) may be used.

An insulator 640 is provided over the conductor 620 and the insulator 630 . The insulator 640 can be provided using a material similar to that of the insulator 320 . In addition, the insulator 640 may function as a planarizing film that covers the uneven shape thereunder.

By using this structure, a semiconductor device including a transistor including an oxide semiconductor can be miniaturized or highly integrated.

101 probe 102 vibrator 103 housing 104 display unit 105 transmission circuit 107 memory circuit 108 image processing circuit 109 control circuit

Claims (3)

a plurality of transducers arranged in a matrix so that ultrasonic waves interfere with each other;
a memory circuit connected to each of the plurality of transducers via a receiving circuit;
an image processing circuit that reads data from the memory circuit and performs image processing;
a display unit for displaying information output from the image processing circuit,
the interval between the transducers is equal to the distance for one cycle of the wavelength of the ultrasonic wave;
the memory circuit includes a transistor and a capacitor electrically connected to the transistor ;
The transistor includes a first conductor, a second conductor, a third conductor, a first oxide semiconductor, a second oxide semiconductor, a third oxide semiconductor, and a third oxide semiconductor. 1 insulator and a metal oxide,
the first conductor functions as one of a source electrode or a drain electrode of the transistor;
the second conductor functions as the other of a source electrode and a drain electrode of the transistor;
the third conductor functions as a gate electrode of the transistor;
the first insulator functions as a gate insulating film of the transistor;
the second oxide semiconductor has a channel formation region of the transistor;
the first oxide semiconductor, the second oxide semiconductor, and the third oxide semiconductor each contain In, Ga, and Zn;
the atomic ratio of Ga in the first oxide semiconductor is greater than the atomic ratio of Ga in the second oxide semiconductor;
an atomic ratio of In to Ga in the second oxide semiconductor is greater than an atomic ratio of In to Ga in the first oxide semiconductor;
The second oxide semiconductor is arranged above the first oxide semiconductor,
the first conductor has a region in contact with the top surface of the second oxide semiconductor;
the second conductor has a region in contact with the top surface of the second oxide semiconductor;
The third oxide semiconductor includes a region in contact with the top surface of the second oxide semiconductor, a region in contact with the side surface of the first conductor, a region in contact with the side surface of the second conductor, and the a region in contact with a sidewall of an opening of a first conductor and a second insulator disposed above the second conductor;
the first insulator has a region in contact with the top surface of the third oxide semiconductor;
The first insulator has a function of releasing oxygen by heating,
the metal oxide is disposed between the first insulator and the third conductor;
The metal oxide includes one or more selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, neodymium, lanthanum, or magnesium,
the third conductor, the first insulator, and the third oxide semiconductor have a region arranged inside the opening of the second insulator;
the upper surface of the second insulator, the edge of the third oxide semiconductor, the edge of the first insulator, and the upper surface of the third conductor are aligned, ultrasonic diagnostic equipment. a probe having two or more transducers arranged at intervals of one cycle of ultrasonic waves;
a plurality of memory circuits connected to each of the two or more transducers via a receiving circuit;
the ultrasonic wave received by the transducer is analog data, and the analog data is held in the memory circuit corresponding to the transducer;
the memory circuit includes a transistor and a capacitor electrically connected to the transistor ;
The transistor includes a first conductor, a second conductor, a third conductor, a first oxide semiconductor, a second oxide semiconductor, a third oxide semiconductor, and a third oxide semiconductor. 1 insulator and a metal oxide,
the first conductor functions as one of a source electrode or a drain electrode of the transistor;
the second conductor functions as the other of a source electrode and a drain electrode of the transistor;
the third conductor functions as a gate electrode of the transistor;
the first insulator functions as a gate insulating film of the transistor;
the second oxide semiconductor has a channel formation region of the transistor;
the first oxide semiconductor, the second oxide semiconductor, and the third oxide semiconductor each contain In, Ga, and Zn;
the atomic ratio of Ga in the first oxide semiconductor is greater than the atomic ratio of Ga in the second oxide semiconductor;
an atomic ratio of In to Ga in the second oxide semiconductor is greater than an atomic ratio of In to Ga in the first oxide semiconductor;
The second oxide semiconductor is arranged above the first oxide semiconductor,
the first conductor has a region in contact with the top surface of the second oxide semiconductor;
the second conductor has a region in contact with the top surface of the second oxide semiconductor;
The third oxide semiconductor includes a region in contact with the top surface of the second oxide semiconductor, a region in contact with the side surface of the first conductor, a region in contact with the side surface of the second conductor, and the a region in contact with a sidewall of an opening of a first conductor and a second insulator disposed above the second conductor;
the first insulator has a region in contact with the top surface of the third oxide semiconductor;
The first insulator has a function of releasing oxygen by heating,
the metal oxide is disposed between the first insulator and the third conductor;
The metal oxide includes one or more selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, neodymium, lanthanum, or magnesium,
the third conductor, the first insulator, and the third oxide semiconductor have a region arranged inside the opening of the second insulator;
the upper surface of the second insulator, the edge of the third oxide semiconductor, the edge of the first insulator, and the upper surface of the third conductor are aligned, ultrasonic diagnostic equipment. In claim 2,
An ultrasonic diagnostic apparatus that divides the voltage output from one of the two or more transducers by time and holds analog data in a plurality of memory circuits.

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