Mobile device

Abstract

To provide a vehicle alarm device having a novel configuration.SOLUTION: A vehicle alarm device has a sound source detection device, wherein the sound source detection device includes a plurality of microphones and a delay circuit. An OS transistor is used as a transistor constituting the delay circuit. An externally derived sound is acquired by the sound source detection device, and a sound source position of the externally derived sound is specified. When it is assessed, from the relative speed between the vehicle and the sound source for which the position was specified and the like, that there is a high risk that the vehicle could collide with the sound source, an audio signal for evoking caution in a passenger is outputted.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One aspect of the present invention relates to a vehicle warning device. Alternatively, one aspect of the present invention relates to a method for operating such a device.

[0002] Furthermore, one aspect of the present invention is not limited to the above-mentioned technical field. The technical field of one aspect of the invention disclosed herein relates to a product, method, or method of manufacture. Alternatively, one aspect of the present invention relates to a process, machine, manufacture, or composition of matter. [Background technology]

[0003] Automobiles and other vehicles have become an indispensable means of transportation and logistics in modern society. In recent years, many organizations have been developing technologies for recognizing the surrounding environment of vehicles using sensors such as LiDAR (Light Detection and Ranging), millimeter-wave radar, and cameras. Patent Document 1 discloses a method for detecting obstacles in areas that cannot be seen visually using sound source localization technology with microphones. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 5-85288 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] One aspect of the present invention aims to provide a novel vehicle warning device, or to provide a vehicle warning device with improved operating speed, or to provide a vehicle warning device that can operate accurately even in high-temperature environments.

[0006] Furthermore, the description of these problems does not preclude the existence of other problems. Moreover, one aspect of the present invention does not need to solve all of these problems. Other problems will naturally become apparent from the description in the specification, drawings, and claims, and it is possible to extract other problems from the description in the specification, drawings, and claims. [Means for solving the problem]

[0007] Another aspect of the present invention is a vehicle warning system having a sound source detection device, the sound source detection device including a plurality of microphones and a delay circuit. The transistor constituting the delay circuit is a transistor (also called an "OS transistor") which includes an oxide semiconductor, a type of metal oxide, in the semiconductor layer in which the channel is formed. The sound source detection device acquires external sounds and identifies the location of the external sound source. If it is determined that there is a high risk of collision between the sound source and the vehicle based on the relative speed of the identified sound source and the vehicle, an acoustic signal is output to alert the occupants.

[0008] Another aspect of the present invention is a vehicle warning device mounted on a vehicle, comprising a sound source detection device, a control device, and a signal output device, wherein the sound source detection device has a function to acquire external sounds and a function to identify the location of the external sound source, the control device has a function to acquire changes in the sound source location and a function to supply a signal to the signal output device, and the signal output device has a function to receive a signal and output an acoustic signal.

[0009] Another aspect of the present invention is a vehicle warning device mounted on a vehicle, which includes a sound source detection device, a control device, and a signal output device. The sound source detection device has a function of acquiring external sounds and a function of specifying the position of the sound source of the external sounds. The control device has a function of acquiring changes in the sound source position and a function of supplying a signal to the signal output device. The signal output device has a function of receiving a signal and outputting an acoustic signal. The sound source detection device includes a microphone array having a first microphone and a second microphone, a first selection circuit, a first signal holding circuit, a second signal holding circuit, a second selection circuit, and a signal processing circuit. The first selection circuit has a function of selecting either the first microphone or the second microphone. The first signal holding circuit has a function of holding the sound source signals acquired at a plurality of timings using the first microphone as a plurality of first voltages corresponding to the respective sound source signals. The second signal holding circuit has a function of holding the sound source signals acquired at a plurality of timings using the second microphone as a plurality of second voltages corresponding to the respective sound source signals. The second selection circuit has a function of selecting any one of the plurality of first voltages and any one of the plurality of second voltages. The signal processing circuit has a function of calculating the first voltage and the second voltage selected by the second selection circuit. The first signal holding circuit and the second signal holding circuit each have a first transistor, and the semiconductor layer of the first transistor includes an oxide semiconductor.

[0010] The acoustic signal is preferably a signal that alerts the occupant. As long as it can alert the occupant, the output of the signal output device does not have to be an acoustic signal. For example, it may be a light emission signal, or it may be an odor, vibration, or the like.

[0011] The control device has a function of acquiring changes in the sound source position using the sound source position and the relative speed between the sound source position and the vehicle.

[0012] The signal processing circuit may include a differential circuit and / or a multiplication circuit.

[0013] Furthermore, one aspect of the present invention is not limited to automobiles, buses, and other vehicles, but can be applied to any mobile body. For example, it can be applied to various mobile bodies such as railway vehicles like trains and locomotives, civil engineering vehicles like cranes and bulldozers, manned robots, aircraft like airplanes and helicopters, ships, and submarines. [Effects of the Invention]

[0014] According to one aspect of the present invention, a novel vehicle warning device can be provided. Alternatively, a vehicle warning device with improved operating speed can be provided. Alternatively, a vehicle warning device that can operate accurately even in high-temperature environments can be provided.

[0015] Furthermore, the description of these effects does not preclude the existence of other effects. Moreover, one aspect of the present invention does not necessarily have to possess all of these effects. Other effects will naturally become apparent from the description in the specification, drawings, and claims, and it is possible to extract other effects from the description in the specification, drawings, and claims. [Brief explanation of the drawing]

[0016] [Figure 1] Figures 1A and 1B are diagrams illustrating the vehicle. [Figure 2] Figures 2A, 2B, and 2C are block diagrams illustrating example configurations of a vehicle warning system and a sound source detection system. [Figure 3] Figure 3 is a flowchart illustrating the operation of the vehicle warning system. [Figure 4] Figure 4 is a flowchart illustrating the operation of the vehicle warning system. [Figure 5] Figure 5 illustrates the operation of the vehicle warning system. [Figure 6] Figure 6 is a diagram illustrating the operation of the vehicle warning system. [Figure 7] Figure 7 is a diagram illustrating the operation of the vehicle warning system. [Figure 8] Figure 8 is a diagram illustrating the operation of the vehicle warning system. [Figure 9] Figure 9 is a diagram illustrating the operation of the vehicle warning system. [Figure 10] Figures 10A and 10B illustrate examples of neural network configurations. [Figure 11] Figures 11A and 11B are block diagrams showing examples of the configuration of a sound source detection device. [Figure 12] Figure 12 illustrates an example of a delay circuit configuration. [Figure 13] Figures 13A and 13B illustrate examples of how a delay circuit operates. [Figure 14] Figure 14 illustrates an example of a delay circuit configuration. [Figure 15] Figure 15 is a timing chart illustrating an example of the operation of a delay circuit. [Figure 16] Figures 16A and 16B illustrate the sound source direction estimation technique. [Figure 17] Figure 17 illustrates an example of a signal processing circuit configuration. [Figure 18] Figures 18A, 18B, and 18C illustrate examples of signal processing circuit configurations. [Figure 19] Figures 19A and 19B illustrate examples of delay circuit configurations. [Figure 20] Figures 20A and 20B illustrate examples of differential circuit configurations. [Figure 21] Figure 21 illustrates an example of a semiconductor device configuration. [Figure 22] Figure 22 illustrates an example of a semiconductor device configuration. [Figure 23] Figures 23A, 23B, and 23C show examples of transistor structures. [Figure 24] Figures 24A, 24B, 24C, 24D, and 24E illustrate the configuration of semiconductor wafers and electronic components. [Figure 25] Figures 25A and 25B show examples of electronic device configurations. [Figure 26] Figure 26 is a diagram illustrating the market image. [Modes for carrying out the invention]

[0017] Embodiments of the present invention will be described in detail below with reference to the drawings. However, it will be readily apparent to those skilled in the art that the present invention is not limited to the following description, and its form and details can be modified in various ways. Furthermore, the present invention is not to be interpreted as being limited to the embodiments described below.

[0018] In the figures described herein, the size of each component, the thickness of each layer, or the area may be exaggerated or omitted to clarify the invention. Therefore, the scale is not necessarily limited. Also, in top views (also called "plan views") and perspective views, some components may be omitted to make the drawings easier to understand. In addition, some hidden lines may be omitted.

[0019] In this specification, ordinal numbers such as "first," "second," etc., are used to avoid confusion of constituent elements and do not indicate any order or rank, such as process order or layering order. Furthermore, even if a term in this specification does not have an ordinal number, an ordinal number may be added in the claims to avoid confusion of constituent elements. Also, even if a term in this specification has an ordinal number, a different ordinal number may be added in the claims. Furthermore, even if a term in this specification has an ordinal number, the ordinal number may be omitted in the claims, etc.

[0020] Furthermore, where it is explicitly stated in this specification that X and Y are connected, this specification shall disclose the cases in which X and Y are electrically connected, functionally connected, and directly connected. Therefore, predetermined connection relationships, not limited to those shown in the figures or text, shall also be disclosed in the figures or text.

[0021] Furthermore, in this specification, "parallel" means, for example, a state in which two lines are arranged at an angle of -10° or more and 10° or less. Therefore, the case of -5° or more and 5° or less is also included. Also, "perpendicular" and "orthogonal" mean, for example, a state in which two lines are arranged at an angle of 80° or more and 100° or less. Therefore, the case of 85° or more and 95° or less is also included.

[0022] In this specification, when count values ​​and measured values ​​are referred to as "identical," "same," "equal," or "uniform" (including synonyms thereof), unless otherwise explicitly stated, this refers to a margin of error of plus or minus 20%.

[0023] Furthermore, in this specification, the high power supply potential VDD (hereinafter also simply referred to as "VDD" or "H potential") refers to a power supply potential that is higher than the low power supply potential VSS. The low power supply potential VSS (hereinafter also simply referred to as "VSS" or "L potential") refers to a power supply potential that is lower than the high power supply potential VDD. The ground potential can also be used as VDD or VSS. For example, if VDD is the ground potential, then VSS is a potential lower than the ground potential, and if VSS is the ground potential, then VDD is a potential higher than the ground potential.

[0024] It should be noted that the terms "film" and "layer" can be interchanged depending on the context or situation. For example, the term "conductive layer" can sometimes be changed to "conductive film." Or, for example, the term "insulating film" can sometimes be changed to "insulating layer."

[0025] (Embodiment 1) A vehicle warning device according to one aspect of the present invention will be described with reference to the drawings. Figure 1A is a perspective view showing the external appearance of a vehicle 100 having a vehicle warning device 200. Figure 1B is a top view of the vehicle 100. For clarity, some components of the vehicle 100 have been omitted in Figure 1B and other figures. Figure 2A shows a block diagram illustrating an example of the configuration of the vehicle warning device 200.

[0026] <Example configuration of vehicle 100 and vehicle warning device 200> The vehicle 100 shown in Figures 1A and 1B has M sound source detection devices 110 (where M is an integer greater than or equal to 1). In this specification, the first sound source detection device 110 is referred to as sound source detection device 110[1], the kth sound source detection device 110 (where k is an integer greater than or equal to 1 and less than or equal to M) is referred to as sound source detection device 110[k], and similarly, the Mth sound source detection device 110 is referred to as sound source detection device 110[M].

[0027] In this specification, when referring to any one of the sound source detection devices 110[1] to 110[M], it will be indicated as "sound source detection device 110[k]" or "sound source detection device 110". The same applies to the symbols indicating other components. To distinguish between multiple elements, expressions such as [1] or _1 are used.

[0028] Figures 1A and 1B show 14 sound source detection devices 110 (sound source detection devices 110[1] to 11[1]). Specifically, the vehicle 100 has sound source detection devices 110[1] to 110[3] at the front, sound source detection devices 110[4] to 110[7] on the right side, sound source detection devices 110[8] to 110

[10] at the rear, and sound source detection devices 110

[11] to 110

[14] on the left side. Note that the number of sound source detection devices 110 installed on the vehicle 100 is not limited to 14. Furthermore, by increasing the number of sound source detection devices 110 used, the detection accuracy of the position and speed of objects approaching the vehicle 100 can be further improved.

[0029] Furthermore, vehicle 100 has an airbag device 131 in the steering wheel 151 and an airbag device 132 in the dashboard 152. It also has an airbag device 133a in the door 135a and an airbag device 133b in the door 135b. Furthermore, it has an airbag device 134a in the door 136a and an airbag device 134b in the door 136b. In addition, vehicle 100 has a control device 120 and a signal output device 130.

[0030] The vehicle warning system 200 comprises a sound source detection device 110, a control device 120, and a signal output device 130. Specifically, M sound source detection devices 110 and signal output devices 130 are connected to the control device 120 (see Figure 2A).

[0031] The control device 120 may include a storage device 121, an arithmetic unit 122, and a neural network 123, etc. The arithmetic unit 122 may be a GPU (Graphics Processing Unit). Alternatively, the control device 120 or the arithmetic unit 122 may be implemented using a PLD (Programmable Logic Device) such as an FPGA (Field Programmable Gate Array) or an FPAA (Field Programmable Analog Array).

[0032] The connection between the sound source detection device 110 and the signal output device 130 and the control device 120 may be via a wired connection or a wireless connection. A wired connection, which uses metal wiring or the like for direct connection, is less susceptible to noise than a wireless connection, which uses wireless communication or the like. Optical fibers may be used instead of metal wiring. On the other hand, using a wireless connection reduces the amount of wiring used for connection. It also increases the flexibility of installation for the sound source detection device 110 and the signal output device 130. Therefore, the installation of the vehicle warning device 200 can be made easier.

[0033] Furthermore, sensors 140 other than the sound source detection device 110 may be connected to the control device 120 (see Figure 2A). Examples of sensors 140 include electromagnetic wave sensors, ultrasonic sensors, infrared sensors, acceleration sensors, image sensors, millimeter-wave radar, and lidar. Multiple types of sensors 140 may be connected to the control device 120.

[0034] Sound source detection devices 110[1] to 110[3] have the function of mainly detecting sound sources in front of the vehicle 100. Sound source detection devices 110[4] to 110[7] have the function of mainly detecting sound sources to the right of the vehicle 100. Sound source detection devices 110[8] to 110

[10] have the function of mainly detecting sound sources behind the vehicle 100. Sound source detection devices 110

[11] to 110

[14] have the function of mainly detecting sound sources to the left of the vehicle 100.

[0035] The installation height H of the sound source detection device 110 (height from the road surface to the sound source detection device 110) is preferably 50 cm or more, preferably 1 m or more, and more preferably 1 m 50 cm or more from the road surface. If the installation position of the sound source detection device 110 is close to the road surface, it may be susceptible to the effects of sound reflection from the road surface, which may reduce the detection accuracy.

[0036] Furthermore, it is preferable that the M sound source detection devices 110 each have the same installation height H from the ground. In particular, it is preferable that the installation height H of sound source detection devices 110[1] to 110[3] is the same. It is also preferable that the installation height H of sound source detection devices 110[4] to 110[7] is the same. Furthermore, it is preferable that the installation height H of sound source detection devices 110[8] to 110

[10] is the same. Furthermore, it is preferable that the installation height H of sound source detection devices 110

[11] to 110

[14] is the same.

[0037] Specifically, the installation height H of each of the M sound source detection devices 110 is preferably 0.8 times or more and 1.2 times or less the average value of the installation height H, and more preferably 0.9 times or more and 1.1 times or less the average value of the installation height H.

[0038] Figure 2B is a block diagram showing the configuration of the sound source detection device 110[k]. The sound source detection device 110[k] includes a microphone array 111[k], a delay circuit group 112[k], a signal processing circuit 113[k], an ADC 114[k], and a digital arithmetic circuit 115[k].

[0039] The microphone array 111[k] has N microphones 116 (where N is an integer greater than or equal to 2). Each microphone 116 has the function of converting the captured sound waves into electrical signals (also called "sound source signals").

[0040] The delay circuit group 112[k] has N delay circuits 117. The j-th microphone 116 (microphone 116[j]), where j is an integer between 1 and N, is electrically connected to the j-th delay circuit 117 (delay circuit 117[j]). The N delay circuits 117 are electrically connected to the signal processing circuit 113[k], and the signal processing circuit 113[k] is electrically connected to the digital arithmetic circuit 115[k]. The sound source detection device 110 will be described in detail later.

[0041] ADC114[k] has the function of converting analog signals to digital signals. Therefore, if the output of the signal processing circuit 113[k] is a digital signal, ADC114 does not need to be provided. Also, by having the control device 120 handle the functions of ADC114[k] and / or the digital arithmetic circuit 115[k], the configuration of the sound source detection device 110[k] can be simplified (see Figure 2C).

[0042] On the other hand, analog signals are susceptible to noise, so if the output of the signal processing circuit 113[k] is an analog signal, it is preferable to place the ADC 114[k] as close as possible to the signal processing circuit 113[k].

[0043] When an ADC 114 is provided in the sound source detection device 110, for example, if the number of sound source directions to be identified is 8, then 8 ADC 114s may be provided in one sound source detection device 110. By providing multiple ADC 114s, the processing capacity of the sound source detection device 110 can be increased.

[0044] <Example of operation of vehicle warning device 200> Next, an example of the operation of the vehicle warning device 200 will be explained with reference to the drawings. Figures 3 and 4 are flowcharts illustrating the operation of the vehicle warning device 200. Figures 5 to 9 are diagrams illustrating the operation of the vehicle warning device 200.

[0045] [Example of operation 1] Figure 3 shows a flowchart illustrating an example of the operation of the vehicle warning device 200. First, it acquires sounds from outside the vehicle 100 (also called "external sounds") (step S310). Figure 5 shows how the external sound 901 emitted by vehicle 900 moving behind a wall-like structure 800 is acquired from the perspective of vehicle 100. The vehicle 900 is not visible from vehicle 100 because it is obscured by the structure 800.

[0046] Next, the location of the sound source of the external sound 901 is identified (step S320; see Figure 6). The method for identifying the sound source location will be explained in detail later.

[0047] Next, the control device 120 determines whether the sound source whose position has been identified is approaching the vehicle 100 based on the sound source position and the relative speed between the sound source and the vehicle 100 (step S330).

[0048] If the control device 120 determines from a change in the sound source's position that there is a risk of the sound source colliding with the vehicle 100, it supplies a signal to the signal output device 130 located inside the vehicle. The signal output device 130 receives the signal supplied by the control device 120 and outputs an acoustic signal, such as a warning sound, to alert the occupants (step S340; see Figure 7). By outputting a warning sound from the signal output device 130, the occupants can take evasive action to prevent a collision. The signal output device 130 may be an audio system or navigation system installed in the vehicle 100.

[0049] Furthermore, the output of the signal output device 130 is not limited to an acoustic signal; it may also be a light-emitting signal. Alternatively, the device may emit odors, vibrations, or other signals to attract the attention of passengers.

[0050] The location of the sound source may be determined using one sound source detection device 110 or multiple sound source detection devices 110. By increasing the number of sound source detection devices 110 used to determine the location of the sound source, the accuracy of determining the location of the sound source can be improved.

[0051] [Example of operation 2] Figure 4 shows a flowchart illustrating an operation different from Operation Example 1. Figure 4 is a flowchart illustrating an example of operation when an occupant protection device (such as an airbag system) is used in conjunction with the vehicle warning device 200.

[0052] Operation Example 2 performs the same operations as Operation Example 1 up to step S340. Subsequently, the digital arithmetic circuit 115[k] and / or the control device 120 analyze the sound source approaching the vehicle 100 and identify what kind of object (vehicle 900 in this embodiment) is approaching based on the type of sound (step S350). For example, noise components such as engine noise, brake noise, and driving noise can be identified and excluded using information processing methods such as template matching. It is also possible to identify whether the object (hereinafter also referred to as "approaching object") is a truck, a car, a motorcycle, etc. Furthermore, if the approaching object is equipped with an ultrasonic collision avoidance device, the ultrasonic waves emitted by the approaching object can also be used to identify the approaching object.

[0053] Information processing, such as identifying the type of approaching object and removing noise components, may be performed using artificial intelligence (AI) technologies such as machine learning.

[0054] For example, the control device 120 may store weight information and acoustic information acquired through pre-training in its memory device 121, and use this weight information and acoustic information to identify the type of approaching object using the neural network 123. Alternatively, the neural network 123 may be configured in software, and the type of approaching object may be identified by performing calculations with the computing device 122.

[0055] By using artificial intelligence technology, noise components such as engine noise, brake noise, driving noise, and other ambient sounds can be removed. Furthermore, by using artificial intelligence technology, approaching objects can be identified from among various noise components.

[0056] Here, we will explain an example of the configuration of neural network 123. As shown in Figure 10A, neural network 123 can be composed of an input layer IL, an output layer OL, and a hidden layer HL. Each of the input layer IL, output layer OL, and hidden layer HL has one or more neurons (neurons 124). The hidden layer HL may be one layer or two or more layers. A neural network with two or more hidden layers HL can be called a DNN (Deep Neural Network), and learning using a deep neural network can be called deep learning.

[0057] Each neuron in the input layer (IL) receives input data, each neuron in the hidden layer (HL) receives the output signal of a neuron in the preceding or succeeding layer, and each neuron in the output layer (OL) receives the output signal of a neuron in the preceding layer. Each neuron may be connected to all neurons in the preceding and succeeding layers (fully connected), or to some of the neurons.

[0058] Figure 10B shows an example of computation by neurons. Here, we see neuron 124 and two neurons in the pre-layer that output signals to neuron 124. Neuron 124 receives the outputs x1 and x2 of the pre-layer neurons as inputs. Then, neuron 124 calculates the sum x1w1 + x2w2, which is the result of multiplying output x1 by weight w1 (x1w1) and output x2 by weight w2 (x2w2). After that, a bias b is added as needed to obtain the value a = x1w1 + x2w2 + b. The value a is then transformed by the activation function h, and the output signal y = h(a) is output from neuron 124.

[0059] Thus, the calculations performed by neurons include operations that add up the products of the outputs of neurons in the previous layer and their weights, i.e., multiply-accumulate operations (x1w1 + x2w2 above). These multiply-accumulate operations may be performed in software using a program, or they may be performed in hardware. When multiply-accumulate operations are performed in hardware, a multiply-accumulate circuit can be used. This multiply-accumulate circuit may be a digital circuit or an analog circuit. When an analog circuit is used for the multiply-accumulate circuit, it is possible to reduce the size of the multiply-accumulate circuit, or to improve processing speed and reduce power consumption by reducing the number of memory accesses.

[0060] The multiply-accumulate (MLP) operation circuit may be constructed using transistors containing silicon (such as single-crystal silicon) in the semiconductor layer where the channel is formed (also called "Si transistors"), or it may be constructed using OS transistors. In particular, OS transistors are suitable as transistors for constructing the analog memory of the MLP operation circuit because they have extremely low off-current. It is also possible to construct the MLP operation circuit using both Si transistors and OS transistors.

[0061] Next, the control device 120 estimates whether a collision between the approaching object and the vehicle 100 is certain based on the change in distance and relative speed between the approaching object and the vehicle 100 (step S360). The control device 120 also estimates the magnitude of the impact at the time of the collision based on the type of approaching object and its relative speed. At this time, by taking into account the information obtained from the sensor 140, the magnitude of the impact can be estimated more accurately.

[0062] If it is determined that the likelihood of a collision is low, the process returns to step S310. If it is determined that a collision is certain, the occupant protection devices are activated (step S370). For example, if airbags are used as occupant protection devices, all airbags installed in vehicle 100 may be activated simultaneously, or the location of the collision of vehicle 100 may be estimated to determine which airbags to activate.

[0063] For example, if a collision with the right side of vehicle 100 is certain, airbag devices 133a and 133b are activated to inflate airbag 108. At this time, airbag 108 may be inflated by a mechanical method such as a pump before the collision (see Figure 8), and then rapidly inflated by an inflator after the collision (see Figure 9).

[0064] The final pressure within the airbag 108 is determined according to the magnitude of the impact during the collision, as previously estimated. By appropriately controlling the pressure within the airbag, optimal occupant protection can be achieved. Alternatively, the pressure within the airbag may be further adjusted after detecting the impact immediately following a collision using an acceleration sensor or similar device. Activating the airbag system before a collision allows for immediate occupant protection.

[0065] Furthermore, the airbag system may be equipped with multiple inflators, and the pressure and inflation speed of the airbag may be adjusted by operating the inflators sequentially. When the airbag system is equipped with multiple inflators, the explosive force of each inflator may be the same or different.

[0066] By incorporating multiple inflators into an airbag system, the amount of explosive used per inflator can be reduced, thereby lowering the possibility of secondary accidents caused by the deployment of the airbag system. Furthermore, the noise of the explosion during inflator deployment can be reduced, thus alleviating the psychological burden on occupants.

[0067] Furthermore, by equipping the airbag system with multiple inflators, even if one inflator malfunctions, the other inflators can ensure that the airbag system operates reliably. Therefore, the redundancy of the airbag system can be increased. In other words, the redundancy of the occupant protection system can be increased.

[0068] Furthermore, if the aforementioned method of inflating the airbag using a mechanical means such as a pump before a collision is used, the airbag can be retracted and reused if the collision is avoided at the last moment or if the collision is minor enough that the inflator does not need to be activated. Even in airbag systems equipped with multiple inflators, if there are unused inflators remaining after the airbag system has been deployed, the airbag can be retracted and reused. Since there is no need to replace the airbag system, the maintenance costs of the vehicle 100 can be reduced.

[0069] This embodiment can be implemented in appropriate combination with the configurations described in other embodiments.

[0070] (Embodiment 2) In this embodiment, the configuration and operation of the sound source detection device 110 described in the above embodiment will be explained in detail with reference to the drawings. Figure 11A is a block diagram showing an example of the configuration of the sound source detection device 110[k] described in the above embodiment. Note that Figure 11A is a block diagram equivalent to Figure 2C. Therefore, in order to reduce repetition of explanation, we will mainly explain the parts that differ from those described in the above embodiment.

[0071] One embodiment of the present invention, a sound source detection device 110[k], comprises a microphone array 111[k] having multiple microphones, and functions as a sound source localization device that can focus on a target direction by delaying the sound entering each microphone and aligning the phase of sound from the target direction. The position of the sound source is estimated by utilizing the fact that the difference in distance between the sound source and the microphones corresponds to the difference in the time-of-flight (ToF) of sound waves.

[0072] In Figure 11A, the sound source signals converted by each microphone 116 are shown as sound source signals D1 to DN. Sound source signal D1 is supplied to delay circuit 117[1], and sound source signal DN is supplied to delay circuit 117[N]. That is, sound source signals D1 to DN are each supplied to the corresponding delay circuit 117[1] to 117[N].

[0073] Furthermore, an amplification circuit may be provided between each microphone 116 and each delay circuit 117. By providing an amplification circuit between each microphone 116 and each delay circuit 117, the distance between the microphone array 111[k] and the delay circuit group 112[k] can be increased.

[0074] The delay circuits 117 (delay circuits 117[1] to 117[N]) have the function of delaying the sound source signals provided from each microphone 116 to generate output signals. Figure 11B shows a block diagram illustrating the configuration of one delay circuit 117. Each delay circuit 117 has a selection circuit 21, a plurality of signal holding circuits 22, and a selection circuit 23.

[0075] The selection circuit 21 (also called the first selection circuit) functions as a demultiplexer, distributing one of the sound source signals D1 to DN, for example, sound source signal D1, to multiple signal holding circuits 22. The selection circuit 21 also functions as a switch, and its on / off state is controlled by the selection signal W. As an example, the selection circuit 21 is composed of an n-channel transistor. In this case, the transistor in the selection circuit 21 turns on when the selection signal W is high and turns off when it is low.

[0076] Multiple signal holding circuits 22 have the function of holding an analog voltage corresponding to the sound source signal and outputting a voltage corresponding to that analog voltage. The signal holding circuits 22 record the analog voltage by sampling the sound source signal by turning on a switch in the selection circuit 21 at a predetermined timing. The writing of the analog voltage to the signal holding circuits 22 can be controlled by setting the selection signal W to a high level. The holding of the analog voltage in the signal holding circuits 22 can be controlled by setting the selection signal W to a low level.

[0077] Each of the multiple signal holding circuits 22 has an analog voltage based on the sound source signal at a time when the selection signal W is set to a high level at a different timing, and this analog voltage is held by setting it to a low level. In other words, each of the multiple signal holding circuits 22 can acquire the sound source signal from the microphone 116 at a different timing and hold a voltage corresponding to that sound source signal. Therefore, by successively sampling the sound source signal in the multiple signal holding circuits 22, discrete values ​​in the sound source signal output from the microphone 116 can be held.

[0078] Furthermore, the multiple signal holding circuits 22 have the function of amplifying and outputting the held analog voltage. For example, each of the multiple signal holding circuits 22 has a source follower circuit and has the function of outputting a voltage corresponding to the held analog voltage via the source follower circuit, etc.

[0079] The selection circuit 23 (also called the second selection circuit) functions as a multiplexer, selecting one of the analog voltages held in the multiple signal holding circuits 22 and outputting it at a different timing. The selection circuit 23 also functions as a switch, and its on / off state is controlled by the selection signal S. As an example, the selection circuit 23 is composed of an n-channel transistor. In this case, the transistor in the selection circuit 23 turns on when the selection signal S is high and turns off when it is low.

[0080] A selection circuit 23 is provided for each delay circuit 117[1] to delay circuit 117[N], and output signals Q11 to Q1n to QN1 to QNn can be obtained. Output signals Q11 to Q1n are signals corresponding to the sound source signal D1, and are discrete signals obtained by sequentially outputting the analog voltages held in the multiple signal holding circuits 22 of the delay circuit 117[1]. These output signals Q11 to Q1n correspond to the sound source signal D1 delayed by a predetermined time. Similarly, output signals Q21 to Q2n to QN1 to QNn are signals corresponding to the sound source signals D2 to DN, and are discrete signals obtained by sequentially outputting the analog voltages held in the signal holding circuits 22 of the delay circuits 117[2] to delay circuit 117[N]. These output signals Q21 to Q2n to QN1 to QNn correspond to the sound source signals D2 to DN delayed by a predetermined time. In other words, by setting the selection signal S to a predetermined delay time, the selection circuit 23 can output output signals Q11~Q1n to QN1~QNn corresponding to the sound source signal with a defined delay time.

[0081] It is preferable that each transistor constituting the delay circuit 117 be an OS transistor. In particular, it is preferable to use OS transistors for the transistors constituting the signal holding circuit 22 within the delay circuit 117. OS transistors have an extremely low current flowing between the source and drain when they are off (also called the "off current"). By using OS transistors in the signal holding circuit 22, the analog voltage obtained by sampling the sound source signal can be held in the signal holding circuit 22 for a long period of time. In other words, the analog voltage held in the signal holding circuit 22 becomes less prone to fluctuation, making it possible to estimate the sound source based on the sound source signal more accurately.

[0082] In addition, the signal retention circuit 22 using OS transistors allows for rewriting and reading of the analog voltage by charging or discharging, making it possible to acquire and read the analog voltage virtually without limit. The signal retention circuit using OS transistors does not involve structural changes at the atomic level, as seen in magnetic memory or resistive random-access memory, and therefore has excellent rewrite endurance. Furthermore, the signal retention circuit using OS transistors does not exhibit instability due to an increase in electron trapping centers, even with repeated rewriting operations like those in flash memory.

[0083] Furthermore, since the signal holding circuit 22 using OS transistors can be freely placed on circuits using Si transistors, integration is easily achieved even when a configuration with multiple delay circuits is implemented. In addition, since OS transistors can be manufactured using the same manufacturing equipment as Si transistors, they can be manufactured at low cost.

[0084] Furthermore, an OS transistor can be a four-terminal semiconductor device by including a back gate electrode in addition to the gate electrode, source electrode, and drain electrode. Depending on the voltage applied to the gate electrode or back gate electrode, it can be configured as an electrical network where the input and output of signals flowing between the source and drain can be independently controlled. Therefore, circuit design can be performed using the same approach as LSIs. In addition, OS transistors have superior electrical characteristics compared to Si transistors in high-temperature environments. Specifically, even at high temperatures of 125°C to 150°C, the ratio of on-current to off-current is large, enabling good switching operation.

[0085] The signal processing circuit 113 has the function of calculating the difference between the output signals selected by the selection circuit 23, calculating the integral of that difference, and estimating the delay time at which the phases of the sound source signals align. As an example, the signal processing circuit 113 includes a differential circuit, an integrating circuit, a comparator, and a triangular wave generation circuit. The differential circuit receives the voltages of the two output signals to be compared, selected by the selection circuit 23, as input. The integrating circuit outputs a value obtained by integrating the output signal of the differential circuit. The comparator receives the output signal of the integrating circuit and the output signal of the triangular wave generation circuit as input.

[0086] The signal processing circuit 113 functions as an analog arithmetic circuit. Since the signal processing circuit 113 performs signal processing by comparing analog signals, it is possible to omit circuits that occupy a large area, such as A / D conversion circuits, thereby suppressing an increase in circuit area.

[0087] Alternatively, the signal processing circuit 113 may be configured as a multiplication circuit. The multiplication circuit can be implemented using logarithmic transformation, addition, and inverse logarithmic transformation circuits with operational amplifiers. Furthermore, the multiplication circuit can also be implemented using translinear circuits such as Gilbert cells.

[0088] One embodiment of the present invention, the sound source detection device 110, uses OS transistors as each transistor constituting the delay circuit 117. Furthermore, one embodiment of the present invention, the sound source detection device 110, employs a method of holding charge corresponding to analog voltages sampled at different timings. Because OS transistors have extremely low off-currents, the holding capacitance required to hold the analog voltage can be reduced. Therefore, the mounting density of the delay circuit 117 can be increased.

[0089] In addition, the sound source detection device 110 according to one aspect of the present invention can read out discrete sound source signals as output signals by reading out analog voltages corresponding to the charge held in the delay circuit 117 at different timings. By varying the timing of the control signal S, the delay time can be controlled to a desired duration. Therefore, the delay time can be controlled to a desired duration without converting the sound source signal to a digital signal, and the phase of the discrete sound source signals can be aligned.

[0090] Figure 12 illustrates a specific circuit configuration example of the delay circuit 117 described in Figure 11B. Figure 12 shows an example of a delay circuit configuration in which the sound source signal D1 output from the microphone 116 is held by two nodes and output as three output signals with different delay times.

[0091] Figure 12 illustrates transistor 101 constituting the selection circuit 21, transistors 101, 102, and 103 constituting the signal holding circuit 22, and transistor 104 constituting the selection circuit 23. Transistors 101 to 104 are n-channel transistors and function as switches that turn on with a high-level control signal and turn off with a low-level control signal.

[0092] Figure 12 illustrates the selection signals W11 and W12 as selection signals W. Selection signals W11 and W12 are signals for sampling the analog voltage of the sound source signal D1 at different timings.

[0093] Figure 12 illustrates nodes F11 and F12 for holding the analog voltage sampled by the selection circuit 21. Figure 12 also illustrates a configuration where nodes F11 and F12 are connected to the gate of transistor 102, which is the input terminal of the source follower circuit. The bias voltage V of the source follower circuit is also shown. BThe diagram illustrates the configuration in which a voltage is applied to the gate of transistor 103. Although the diagram shows capacitive elements connected to nodes F11 and F12, these can be omitted by setting the gate capacitance of transistor 102 to a sufficiently large value. In Figure 12, the nodes to which transistors 102 and 103, which constitute the source follower circuit, are connected are shown as O11 and O12. The voltages at nodes O11 and O12 correspond to the analog voltages at nodes F11 and F12. The presence of the source follower circuit increases the charge supply capability to the subsequent selection circuit 23.

[0094] Figure 12 illustrates the selection signals S11 to S1n and S21 to S2n as selection signals S of the selection circuit 23. Selection signals S11 to S1n have the function of outputting the voltage of node O11 to output signals Q11 to Q1n. By adjusting the timing of supplying selection signals S11 to S1n, the output signals Q11 to Q1n can be made to be signals in which the voltage of node O11 is delayed by a predetermined period. In addition, selection signals S21 to S2n have the function of outputting the voltage of node O12 to output signals Q11 to Q1n. By adjusting the timing of supplying selection signals S21 to S2n, the output signals Q11 to Q1n can be made to be signals in which the voltage of node O12 is delayed by a predetermined period.

[0095] Next, the operation of the delay circuit 117 shown in Figure 12 will be explained with reference to Figures 13 to 16.

[0096] Figure 13A shows an example configuration of a delay circuit 117, which facilitates understanding of the operation in Figure 12. The selection signals W11 to W13 are used to sample the sound source signal, and the selection signals S111 and S112, S121 and S122, and S131 and S132 are used to read out the multiple analog voltages held as output signals Q11 and Q12. In other words, the delay circuit 117 shown in Figure 13A samples the sound source signal at three different timings to acquire three analog voltages, and outputs two output signals with different delay times at two different timings. Figure 13A also illustrates nodes F11 to F13 and nodes O11 to O13.

[0097] Figure 13B is a timing chart illustrating the sampling operation of the sound source signal D1 connected to the delay circuit 117 shown in Figure 13A. In Figure 13B, the waveform of the sound source signal D1 is shown, along with the operation of the selection signals W11 to W13 and the voltages written to nodes F11 to F13 at times T1 to T4. In the diagram illustrating the timing chart, the hatched periods represent periods of indeterminate states.

[0098] As described above, at time T1, the selection signal W11 is set to a high level, and the voltage V1 of the sound source signal D1 is written to node F11, and sampling of the sound source signal D1 is performed.

[0099] At time T2, after a period T, the selection signal W12 is set to a high level, and the voltage V2 of the sound source signal D1 is written to node F12, thereby sampling the sound source signal D1. A shorter period T is preferable. This allows for a higher sampling rate of the sound source signal and improves angular resolution.

[0100] At time T3, the selection signal W13 is set to a high level, and the voltage V3 of the sound source signal D1 is written to node F13, causing the sound source signal D1 to be sampled.

[0101] The voltages V1 to V3 held at nodes F11 to F13 can be maintained by setting the selection signals W11 to W13 to the L level. To initialize, as shown at time T4, set the selection signal W11 to the H level while applying a constant potential sound source signal.

[0102] Figure 14 shows an example configuration of delay circuit 117[1], in order to facilitate understanding of the operation in Figure 12, in which selection signals W11 to W13 are used to sample the sound source signal D1, and selection signals S111 and S112, S121 and S122, and selection signals S131 and S132 are used to read out the held voltages as output signals Q11 and Q12. Also shown is an example configuration of delay circuit 117[2], in which selection signals W21 to W23 are used to sample the sound source signal D2, and selection signals S211 and S212, S221 and S222, and selection signals S231 and S232 are used to read out the held voltages as output signals Q21 and Q22. In other words, the delay circuits 117[1] and 117[2] shown in Figure 14 acquire three analog voltages and output two output signals with different delay times at two different timings. Figure 14 also illustrates nodes F11 to F13, nodes F21 to F23, nodes O11 to O13, and nodes O21 to O23.

[0103] Figure 15 is a timing chart illustrating the operation of reading out the voltages V1 to V3 held at nodes F11 to F13 of the delay circuit 117[1] shown in Figure 14, and the voltages V4 to V6 held at nodes F21 to F23 of the delay circuit 117[2], as output signals Q11, Q12, Q21, and Q22. Figure 15 also illustrates the operation of the output signals Q11, Q12, Q21, and Q22, which are read out from nodes F11 to F13 and nodes F21 to F23 by the selection signals S111 and S112, S121 and S122, S131 and S132, S211 and S212, S221 and S222, and selection signals S231 and S232, at times T5 to T8.

[0104] At time T5, the selection signal S111 is set to high level, and the voltage corresponding to the voltage V1 at node F11 is output as output signal Q11. Also at the same time T5, the selection signal S211 is set to high level, and the voltage corresponding to the voltage V4 at node F21 is output as output signal Q21.

[0105] At time T7, the selection signal S131 is set to high level, and the voltage corresponding to the voltage V3 at node F13 is output as output signal Q11. Also at the same time T7, the selection signal S122 is set to high level, and the voltage corresponding to the voltage V5 at node F12 is output as output signal Q12. Also at time T7, the selection signal S231 is set to high level, and the voltage corresponding to the voltage V6 at node F23 is output as output signal Q21. Also at the same time T7, the selection signal S222 is set to high level, and the voltage corresponding to the voltage V5 at node F22 is output as output signal Q22.

[0106] At time T8, the selection signal S132 is set to high level, and the voltage corresponding to the voltage V3 at node F13 is output as output signal Q12. Also at the same time T8, the selection signal S232 is set to high level, and the voltage corresponding to the voltage V6 at node F23 is output as output signal Q22.

[0107] As shown in Figure 15, output signal Q12 can be obtained as a delayed signal of output signal Q11. Similarly, output signal Q22 can be obtained as a delayed signal of output signal Q21. By controlling the timing of the selection signal S, the signal held in the signal holding circuit can be delayed and output by an arbitrary delay period. Therefore, for example, when the distance between the sound source and the microphone is different for delay circuit 117[1] and delay circuit 117[2], the phase of the sound source signal can be aligned by switching the delay period, and the direction of the sound source can be estimated.

[0108] Figure 16A is a schematic diagram illustrating the technique of aligning the phase of the output signal corresponding to the sound source signal and estimating the direction of the sound source by switching the delay period described above.

[0109] Figure 16A shows the sound source 40, as well as microphones 116[1] and 116[2] as part of the microphone array. For explanatory purposes, in Figure 16A, the distance between the sound source 40 and microphone 116[1] is assumed to be 1 m, and the distance between microphones 116[1] and 116[2] is assumed to be 0.5 m. Therefore, the distance from the sound source 40 to microphone 116[2] is approximately 1.12 m. Consequently, assuming a sound speed of 340 m / s, the arrival of sound from the sound source 40 to microphone 116[2] will be delayed by approximately 0.35 ms compared to the arrival of sound from the sound source 40 to microphone 116[1].

[0110] Figure 16B visualizes the output signals Q11 to Q13 and Q21 to Q23 obtained by delaying the sound source signal through delay circuits 117[1] and 117[2] in the schematic diagram shown in Figure 16A. As shown in Figure 16B, delay circuits 117[1] and 117[2] delay the output signal using delay circuits set to no delay period (0ms), with a delay period (0.35ms), and with a delay period (0.7ms).

[0111] As shown in Figure 16B, without a delay period (0 ms), there is a difference in the arrival time of sound between microphone 116[1] and microphone 116[2], so the output signals from both delay circuits 117[1] and 117[2] do not match (time t1). On the other hand, the output signal that has gone through a delay period (0.35 ms) in delay circuit 117[1] matches the output signal from delay circuit 117[2] without a delay period (time t2). The output signals obtained at times t3 and t4 also match. By comparing the output signals that have gone through different delay circuits, it is possible to determine whether the phases of the output signals match or not, and this can be used to estimate the sound source.

[0112] As shown in the schematic diagrams of Figures 16A and 16B, the output signals based on the sampled sound source signals are delayed, and these output signals are compared with each other. Therefore, it is possible to estimate the phase delay period of sound from the target direction, and by calculating the difference in distance to the sound source from the delay time, it can function as a sound source localization device that can focus on the target direction.

[0113] Next, Figure 17 illustrates a specific example of the configuration of the signal processing circuit 113. The signal processing circuit 113 shown in Figure 17 includes differential circuits 31_1 to 31_9, integral circuits 32_1 to 32_9, comparators 33_1 to 33_9, a triangular wave generation circuit 34, and an arithmetic circuit 35.

[0114] Differential circuits 31_1 to 31_9 calculate the difference between the output signals (output signals Q11 to Q13 and Q21 to Q23 in the example of Figure 17) output from each delay circuit (delay circuit 117[1] and delay circuit 117[2] in the example of Figure 17). Integrating circuits 32_1 to 32_9 receive the output signals from each differential circuit 31_1 to 31_9 and integrate them. Comparators 33_1 to 33_9 receive the triangular wave output from the triangular wave generation circuit 34 and the output signals from the integrating circuits 32_1 to 32_9 and compare the voltages. The calculation circuit 35 receives the output signals from the comparators 33_1 to 33_9 and estimates the delay time required to align the phase of the sound source signal, thereby obtaining the output signal OUT corresponding to the difference in distance to the sound source from the delay time.

[0115] Specific examples of the circuits constituting the signal processing circuit 113 will be explained with reference to Figures 18A to 18C. Figure 18A is a block diagram showing the configuration of one stage of the signal processing circuit 113 shown in Figure 17. As an example, Figure 18A shows a differential circuit 31, an integrating circuit 32, a comparator 33, and a triangular wave generation circuit 34 to which output signals Q1 and Q2 are input.

[0116] An example configuration of the differential circuit 31 is shown in Figure 18B. The differential circuit 31, as an example, includes resistors 51 and 52, and transistors 53, 54, and 55. The gate of transistor 53 is connected to a non-inverting input terminal. The gate of transistor 54 is connected to an inverting input terminal. The gate of transistor 55 is connected to a wire that provides a bias voltage Vbias. The drain terminal side of transistor 54 is provided with the output terminal OUT of the differential circuit 31.

[0117] An example configuration of the integrating circuit 32 is shown in Figure 18C. The integrating circuit 32, as an example, includes a diode 61, a resistor 62, an operational amplifier 63, a capacitive element 64, and a switch 65. The output signal of the differential circuit 31 is supplied to the input terminal of the diode 61. The output terminal OUT of the integrating circuit 32 is provided at the output terminal of the operational amplifier.

[0118] Figures 19A and 19B show modified circuit configurations applicable to each transistor in the delay circuit 117 described above.

[0119] In Figures 12, 13A, etc., transistors 101 to 104 are shown as top-gate or bottom-gate transistors without a back gate electrode, but are not limited to these. For example, transistors 101A to 104A may have a back gate electrode, as in the delay circuit 117A shown in Figure 19A. The configuration in Figure 19A makes it easier to control the state of transistors 101A to 104A from the outside.

[0120] In Figures 12, 13A, etc., transistors 101 to 104 are shown as top-gate or bottom-gate transistors without a back gate electrode, but are not limited to these. For example, transistors 101B to 104B may have a back gate electrode connected to the gate electrode, as shown in the delay circuit 117B in Figure 19B. By using the configuration in Figure 19B, the amount of current flowing through transistors 101B to 104B can be increased.

[0121] Figures 20A and 20B show modified circuit configurations applicable to each transistor in the differential circuit 31 described above.

[0122] In Figure 18B, transistors 53 to 55 are shown as top-gate or bottom-gate transistors without a back gate electrode, but are not limited to these. For example, transistors 53A to 55A may have a back gate electrode, as in the differential circuit 31A shown in Figure 20A. The configuration in Figure 20A makes it easier to control the state of transistors 53A to 55A from the outside.

[0123] In Figure 18B, transistors 53 to 55 are shown as top-gate or bottom-gate transistors without a back gate electrode, but are not limited to these. For example, transistors 53B to 55B may have a back gate electrode connected to the gate electrode, as shown in the differential circuit 31B in Figure 20B. By using the configuration shown in Figure 20B, the amount of current flowing through transistors 53B to 55B can be increased.

[0124] The semiconductor device according to one aspect of the present invention described above can hold the signals from multiple microphones together as an analog signal and output a delayed signal. Furthermore, it can be configured to perform signal processing while the signal remains in analog voltage. Therefore, the A / D conversion circuit for signal processing can be reduced, and malfunctions due to frequency errors or asynchronous operations caused by large amounts of calculation processing can be reduced. It should be noted that the semiconductor device according to one aspect of the present invention is not limited to application to sound source localization technology, which identifies the direction from which a particular sound is emitted. For example, it can also be applied to technology that estimates the state from the phase difference of a received signal.

[0125] This embodiment can be implemented in appropriate combination with the configurations described in other embodiments.

[0126] (Embodiment 3) This embodiment describes a transistor configuration applicable to semiconductor devices such as the vehicle warning device 200 described in the above embodiment. Specifically, a configuration in which transistors with different electrical characteristics are stacked is described. This configuration increases the design flexibility of the semiconductor device. Furthermore, stacking transistors with different electrical characteristics increases the integration density of the semiconductor device.

[0127] The semiconductor device shown in Figure 21 includes a transistor 300, a transistor 500, and a capacitive element 600. Figure 23A is a cross-sectional view of transistor 500 in the channel length direction, Figure 23B is a cross-sectional view of transistor 500 in the channel width direction, and Figure 23C is a cross-sectional view of transistor 300 in the channel width direction.

[0128] Transistor 500 is an OS transistor. Therefore, because transistor 500 has a low off-current, using it in a semiconductor device allows it to retain written data voltage or charge for a long period of time. In other words, because the frequency of refresh operations is reduced, or refresh operations are not required at all, the power consumption of the semiconductor device can be reduced.

[0129] The semiconductor device described in this embodiment has a transistor 300, a transistor 500, and a capacitive element 600, as shown in Figure 21. The transistor 500 is located above the transistor 300, and the capacitive element 600 is located above both the transistor 300 and the transistor 500.

[0130] The transistor 300 is provided on the substrate 311 and has a conductor 316, an insulator 315, a semiconductor region 313 consisting of a part of the substrate 311, a low-resistance region 314a that functions as a source region or drain region, and a low-resistance region 314b. The transistor 300 can be applied, for example, to the transistor in the buffer circuit 17 in the above embodiment.

[0131] As shown in Figure 23C, the transistor 300 has its semiconductor region 313's top surface and side surface in the channel width direction covered by a conductor 316 via an insulator 315. By making the transistor 300 a Fin type in this way, the effective channel width can be increased, thereby improving the on-characteristics of the transistor 300. In addition, the contribution of the gate electrode's electric field can be increased, thus improving the off-characteristics of the transistor 300.

[0132] Note that transistor 300 can be either a p-channel or n-channel type.

[0133] In the low-resistance region 314a and low-resistance region 314b, which are the channel-forming region of the semiconductor region 313, the region near it, the source region, or the drain region, it is preferable that a semiconductor such as a silicon-based semiconductor is included, and it is preferable that single-crystal silicon is included. Alternatively, it may be formed from a material having Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), etc. A configuration using silicon in which the effective mass is controlled by applying stress to the crystal lattice and changing the lattice spacing is also possible. Alternatively, the transistor 300 may be made into a HEMT (High Electron Mobility Transistor) by using GaAs and GaAlAs, etc.

[0134] The low-resistance regions 314a and 314b include, in addition to the semiconductor material applied to the semiconductor region 313, elements that impart n-type conductivity, such as arsenic and phosphorus, or elements that impart p-type conductivity, such as boron.

[0135] The conductor 316, which functions as the gate electrode, can be made of a conductive material such as silicon, a semiconductor material, a metallic material, an alloy material, or a metal oxide material, which contains an element that imparts n-type conductivity such as arsenic or phosphorus, or an element that imparts p-type conductivity such as boron.

[0136] Furthermore, 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 materials such as titanium nitride or tantalum nitride as the conductor. In addition, in order to achieve both conductivity and embedding properties, it is preferable to use metallic materials such as tungsten or aluminum as a laminate for the conductor, and tungsten is particularly preferable in terms of heat resistance.

[0137] Note that the transistor 300 shown in Figure 21 is just one example, and its structure is not limited to this; any appropriate transistor can be used depending on the circuit configuration and driving method. For example, if the semiconductor device is a unipolar circuit consisting only of OS transistors (meaning transistors of the same polarity, such as only n-channel transistors), then the configuration of transistor 300 can be the same as that of transistor 500, which uses an oxide semiconductor, as shown in Figure 22. Details of transistor 500 will be described later.

[0138] The transistor 300 is covered by a series of insulators, 320, 322, 324, and 326, which are stacked in that order.

[0139] For insulators 320, 322, 324, and 326, for example, silicon oxide, silicon oxide nitride, silicon oxide nitride, silicon nitride, aluminum oxide, aluminum oxide nitride, aluminum oxide nitride, aluminum nitride, etc. may be used.

[0140] In this specification, silicon oxidizide refers to a material in which the oxygen content is greater than the nitrogen content, and silicon nitride refers to a material in which the nitrogen content is greater than the oxygen content. Furthermore, in this specification, aluminum oxidizide refers to a material in which the oxygen content is greater than the nitrogen content, and aluminum nitride refers to a material in which the nitrogen content is greater than the oxygen content.

[0141] The insulator 322 may also function as a planarizing film that flattens steps caused by transistors 300 or the like located below it. For example, the upper surface of the insulator 322 may be planarized by a planarizing treatment using chemical mechanical polishing (CMP) or the like to improve its flatness.

[0142] Furthermore, it is preferable to use a film for the insulator 324 that has barrier properties to prevent hydrogen and impurities from diffusing from the substrate 311 or the transistor 300 to the region where the transistor 500 is provided.

[0143] As an example of a film having barrier properties against hydrogen, silicon nitride formed by the CVD method can be used. However, when hydrogen diffuses into a semiconductor element having an oxide semiconductor, such as transistor 500, the properties of the semiconductor element may deteriorate. Therefore, it is preferable to use a film that suppresses hydrogen diffusion between transistor 500 and transistor 300. Specifically, a film that suppresses hydrogen diffusion is a film that has a low hydrogen desorption rate.

[0144] The amount of hydrogen desorption can be analyzed, for example, using a thermal desorption gas analysis (TDS) method. For example, in TDS analysis, the amount of hydrogen desorption from insulator 324, when the film surface temperature is in the range of 50°C to 500°C, is calculated as 10 × 10¹⁶ hydrogen atoms per unit area of ​​insulator 324. 15 atoms / cm 2 The following is preferably 5 × 10 15 atoms / cm 2 The following is acceptable.

[0145] Furthermore, it is preferable that the dielectric constant of the insulator 326 is lower than that of the insulator 324. For example, the relative permittivity of the insulator 326 is preferably less than 4, and more preferably less than 3. Also, for example, the relative permittivity of the insulator 326 is preferably 0.7 times or less, and more preferably 0.6 times or less, than that of the relative permittivity of the insulator 324. By using a material with a low dielectric constant as the interlayer film, parasitic capacitance occurring between wiring can be reduced.

[0146] Furthermore, insulators 320, 322, 324, and 326 have embedded conductors 328 and 330, which connect to the capacitive element 600 or the transistor 500. Conductors 328 and 330 function as plugs or wires. Conductors that function as plugs or wires may be grouped together and assigned the same reference numeral. In this specification, the wire and the plug connected to the wire may be an integrated unit. That is, a part of the conductor may function as a wire, and a part of the conductor may function as a plug.

[0147] The plugs and wiring (conductor 328, conductor 330, etc.) can be made of conductive materials such as metal materials, alloy materials, metal nitride materials, or metal oxide materials, which can be used in a single layer or in a laminated form. It is preferable to use high-melting-point materials such as tungsten or molybdenum that provide both heat resistance and conductivity, and tungsten is preferred. Alternatively, it is preferable to form them with low-resistance conductive materials such as aluminum or copper. Using low-resistance conductive materials can reduce the wiring resistance.

[0148] A wiring layer may be provided on the insulator 326 and the conductor 330. For example, in Figure 21, insulators 350, 352, and 354 are stacked in order. Conductors 356 are formed on insulators 350, 352, and 354. Conductors 356 function as a plug or wiring for connecting to the transistor 300. Conductors 356 can be provided using the same material as conductors 328 and 330.

[0149] For example, it is preferable that the insulator 350, like the insulator 324, be an insulator that has barrier properties against hydrogen. It is also preferable that the conductor 356 includes a conductor that has barrier properties against hydrogen. In particular, a conductor that has barrier properties against hydrogen is formed in the openings of the hydrogen barrier insulator 350. With this configuration, transistor 300 and transistor 500 can be separated by the barrier layer, and the diffusion of hydrogen from transistor 300 to transistor 500 can be suppressed.

[0150] For example, tantalum nitride may be used as the conductor that has barrier properties against hydrogen. Furthermore, by laminating tantalum nitride with highly conductive tungsten, it is possible to suppress the diffusion of hydrogen from the transistor 300 while maintaining conductivity as wiring. In this case, it is preferable that the tantalum nitride layer, which has barrier properties against hydrogen, is in contact with the insulator 350, which also has barrier properties against hydrogen.

[0151] A wiring layer may be provided on the insulator 354 and the conductor 356. For example, in Figure 21, insulators 360, 362, and 364 are stacked in order. Conductors 366 are formed on insulators 360, 362, and 364. Conductors 366 function as a plug or wiring. Conductors 366 can be provided using the same material as conductors 328 and 330.

[0152] For example, it is preferable that the insulator 360, like the insulator 324, be an insulator having barrier properties against hydrogen. Furthermore, it is preferable that the conductor 366 includes a conductor having barrier properties against hydrogen. In particular, a conductor having barrier properties against hydrogen is formed in the openings of the hydrogen barrier insulator 360. With this configuration, transistor 300 and transistor 500 can be separated by the barrier layer, and the diffusion of hydrogen from transistor 300 to transistor 500 can be suppressed.

[0153] A wiring layer may be provided on the insulator 364 and the conductor 366. For example, in Figure 21, insulators 370, 372, and 374 are stacked in order. Conductors 376 are formed on insulators 370, 372, and 374. Conductors 376 function as a plug or wiring. Conductors 376 can be provided using the same material as conductors 328 and 330.

[0154] For example, it is preferable that the insulator 370, like the insulator 324, be an insulator having barrier properties against hydrogen. Furthermore, it is preferable that the conductor 376 includes a conductor having barrier properties against hydrogen. In particular, a conductor having barrier properties against hydrogen is formed in the openings of the hydrogen barrier insulator 370. With this configuration, transistor 300 and transistor 500 can be separated by the barrier layer, and the diffusion of hydrogen from transistor 300 to transistor 500 can be suppressed.

[0155] A wiring layer may be provided on the insulator 374 and the conductor 376. For example, in Figure 21, insulators 380, 382, ​​and 384 are stacked in order. Conductors 386 are formed on insulators 380, 382, ​​and 384. Conductors 386 function as a plug or wiring. Conductors 386 can be provided using the same material as conductors 328 and 330.

[0156] For example, it is preferable that the insulator 380, like the insulator 324, be an insulator having barrier properties against hydrogen. Furthermore, it is preferable that the conductor 386 includes a conductor having barrier properties against hydrogen. In particular, a conductor having barrier properties against hydrogen is formed in the openings of the hydrogen barrier insulator 380. With this configuration, transistor 300 and transistor 500 can be separated by the barrier layer, and the diffusion of hydrogen from transistor 300 to transistor 500 can be suppressed.

[0157] In the above, wiring layers including conductor 356, wiring layers including conductor 366, wiring layers including conductor 376, and wiring layers including conductor 386 have been described, but the semiconductor device according to this embodiment is not limited thereto. Three or fewer wiring layers similar to the wiring layer including conductor 356 may be used, or five or more wiring layers similar to the wiring layer including conductor 356 may be used.

[0158] Insulators 510, 512, 514, and 516 are layered sequentially on the insulator 384. It is preferable that one of the insulators 510, 512, 514, and 516 is made of a material that has barrier properties against oxygen and hydrogen.

[0159] For example, it is preferable to use a film for insulators 510 and 514 that has barrier properties to prevent hydrogen and impurities from diffusing from, for example, the substrate 311 or the region where the transistor 300 is installed to the region where the transistor 500 is installed. Therefore, the same material as for insulator 324 can be used.

[0160] As an example of a film having hydrogen barrier properties, silicon nitride formed by the CVD method can be used. However, when hydrogen diffuses into a semiconductor element having an oxide semiconductor, such as transistor 500, the characteristics of the semiconductor element may deteriorate. Therefore, it is preferable to use a film that suppresses hydrogen diffusion between transistor 500 and transistor 300. Specifically, a film that suppresses hydrogen diffusion is a film that has a low hydrogen desorption rate.

[0161] Furthermore, as a film having barrier properties against hydrogen, it is preferable to use metal oxides such as aluminum oxide, hafnium oxide, and tantalum oxide for insulator 510 and insulator 514.

[0162] In particular, aluminum oxide exhibits a high barrier effect, preventing the penetration of both oxygen and impurities such as hydrogen and moisture, which can cause fluctuations in the electrical properties of transistors. Therefore, aluminum oxide can prevent the ingress of impurities such as hydrogen and moisture into the transistor 500 during and after the transistor manufacturing process. It can also suppress the release of oxygen from the oxides constituting the transistor 500. For this reason, it is suitable for use as a protective film for transistor 500.

[0163] Furthermore, for example, the same materials as insulator 320 can be used for insulators 512 and 516. Additionally, by applying materials with relatively low dielectric constants to these insulators, parasitic capacitance between wiring can be reduced. For example, silicon oxide films or silicon oxynitride films can be used as insulators 512 and 516.

[0164] Furthermore, the insulators 510, 512, 514, and 516 have a conductor 518 and a conductor constituting the transistor 500 (for example, conductor 503) embedded in them. The conductor 518 functions as a plug or wiring for connecting to the capacitive element 600 or the transistor 300. The conductor 518 can be provided using the same material as the conductors 328 and 330.

[0165] In particular, the conductor 518 in the 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 configuration, transistor 300 and transistor 500 can be separated by a layer having barrier properties against oxygen, hydrogen, and water, and the diffusion of hydrogen from transistor 300 to transistor 500 can be suppressed.

[0166] A transistor 500 is provided above the insulator 516.

[0167] As shown in Figures 23A and 23B, the transistor 500 includes a conductor 503 arranged to be embedded in insulators 514 and 516, an insulator 520 arranged on top of insulators 516 and 503, an insulator 522 arranged on top of insulator 520, an insulator 524 arranged on top of insulator 522, an oxide 530a arranged on top of insulator 524, an oxide 530b arranged on top of oxide 530a, conductors 542a and 542b arranged spaced apart from each other on oxide 530b, an insulator 580 arranged on top of conductors 542a and 542b with an opening formed between conductors 542a and 542b, an oxide 530c arranged on the bottom and side surfaces of the opening, an insulator 550 arranged on the forming surface of oxide 530c, and a conductor 560 arranged on the forming surface of insulator 550.

[0168] Furthermore, as shown in Figures 23A and 23B, it is preferable that an insulator 544 is placed between the oxide 530a, oxide 530b, conductor 542a, and conductor 542b and the insulator 580. Also, as shown in Figures 23A and 23B, it is preferable that the conductor 560 has a conductor 560a provided inside the insulator 550 and a conductor 560b provided so as to be embedded inside the conductor 560a. Furthermore, as shown in Figures 23A and 23B, it is preferable that an insulator 574 is placed on top of the insulator 580, conductor 560, and insulator 550.

[0169] In this specification and other documents, oxides 530a, 530b, and 530c are sometimes collectively referred to as oxide 530.

[0170] While the transistor 500 shows a configuration in which three layers of oxide 530a, oxide 530b, and oxide 530c are stacked in the region where the channel is formed and in its vicinity, the present invention is not limited to this. For example, a single layer of oxide 530b, a two-layer structure of oxide 530b and oxide 530a, a two-layer structure of oxide 530b and oxide 530c, or a stacked structure of four or more layers may be provided. Also, while the conductor 560 is shown as a two-layer stacked structure in the transistor 500, the present invention is not limited to this. For example, the conductor 560 may be a single-layer structure or a stacked structure of three or more layers. Furthermore, the transistor 500 shown in Figures 21 and 23A is just an example, and the present invention is not limited to its structure; an appropriate transistor may be used depending on the circuit configuration and driving method.

[0171] Here, the conductor 560 functions as the gate electrode of the transistor, and the conductors 542a and 542b function as the source electrode or drain electrode, respectively. As described above, the conductor 560 is formed to be embedded in the opening of the insulator 580 and in the region sandwiched between the conductors 542a and 542b. The arrangement of the conductors 560, 542a, and 542b is selected in a self-aligned manner with respect to the opening of the insulator 580. In other words, in the transistor 500, the gate electrode can be positioned in a self-aligned manner between the source electrode and the drain electrode. Therefore, since the conductor 560 can be formed without providing a positional margin, the occupied area of ​​the transistor 500 can be reduced. This enables miniaturization and high integration of semiconductor devices.

[0172] Furthermore, since the conductor 560 is formed self-aligned in the region between the conductors 542a and 542b, the conductor 560 does not have any region that overlaps with the conductors 542a or 542b. This reduces the parasitic capacitance formed between the conductor 560 and the conductors 542a and 542b. Therefore, the switching speed of the transistor 500 can be improved, and it can be given high frequency characteristics.

[0173] Conductor 560 may function as a first gate (also called a top gate) electrode. Conductor 503 may function as a second gate (also called a bottom gate) electrode. In this case, the threshold voltage of transistor 500 can be controlled by changing the potential applied to conductor 503 independently of the potential applied to conductor 560, without linking them. In particular, by applying a negative potential to conductor 503, it is possible to make the threshold voltage of transistor 500 greater than 0V and reduce the off-current. Therefore, applying a negative potential to conductor 503 reduces the drain current when the potential applied to conductor 560 is 0V compared to not applying a negative potential.

[0174] The conductor 503 is positioned so as to overlap with the oxide 530 and the conductor 560. As a result, 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 connect, and can cover the channel-forming region formed in the oxide 530.

[0175] In this specification, a transistor structure in which the channel formation region is electrically surrounded by the electric fields of a pair of gate electrodes (a first gate electrode and a second gate electrode) is called a surrounded channel (S-channel) structure. In this specification, the surrounded channel (S-channel) structure is characterized in that the sides and periphery of the oxide 530 in contact with the conductors 542a and 542b, which function as the source and drain electrodes, are I-type, just like the channel formation region. Furthermore, the sides and periphery of the oxide 530 in contact with the conductors 542a and 542b are in contact with the insulator 544, and therefore can also be I-type, just like the channel formation region. In this specification, I-type can be treated the same as high-purity intrinsic material, which will be described later. Also, the S-channel structure disclosed in this specification is different from the Fin-type structure and the planar-type structure. By adopting the S-channel structure, resistance to short-channel effects can be increased, or in other words, a transistor in which short-channel effects are less likely to occur can be made.

[0176] Furthermore, the conductor 503 has a similar configuration to the conductor 518, with conductor 503a formed in contact with the inner walls of the openings of the insulators 514 and 516, and conductor 503b formed further inside. Although the transistor 500 shows a configuration in which conductors 503a and conductor 503b are stacked, the present invention is not limited to this. For example, the conductor 503 may be provided as a single layer or as a stacked structure of three or more layers.

[0177] Here, it is preferable to use a conductive material for the conductor 503a that has the function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, and copper atoms (i.e., the above impurities are less permeable). Alternatively, it is preferable to use a conductive material that has the function of suppressing the diffusion of oxygen (e.g., at least one such as oxygen atoms or oxygen molecules) (i.e., the above oxygen is less permeable). In this specification, the function of suppressing the diffusion of impurities or oxygen means the function of suppressing the diffusion of any one or all of the above impurities or oxygen.

[0178] For example, since the conductor 503a has a function of suppressing the diffusion of oxygen, it is possible to suppress the oxidation of the conductor 503b and the decrease in conductivity.

[0179] Further, when the conductor 503 also serves as a wiring, the conductor 503b is preferably made of a highly conductive material mainly composed of tungsten, copper, or aluminum. In that case, the conductor 505 does not necessarily have to be provided. Although the conductor 503b is shown as a single layer, it may have a laminated structure. For example, it may be a laminate of titanium or titanium nitride and the above-mentioned conductive material.

[0180] The insulators 520, 522, and 524 have a function as a second gate insulating film.

[0181] Here, the insulator 524 in contact with the oxide 530 is preferably an insulator containing more oxygen than the oxygen satisfying the stoichiometric composition. That is, it is preferable that an excess oxygen region is formed in the insulator 524. By providing such an insulator containing excess oxygen in contact with the oxide 530, the oxygen vacancies (V O : also referred to as oxygen vacancy) in the oxide 530 can be reduced, and the reliability of the transistor 500 can be improved. When hydrogen enters the oxygen vacancies in the oxide 530, the defect (hereinafter sometimes referred to as V O H.) may function as a donor, and electrons as carriers may be generated. Also, part of the hydrogen may combine with the oxygen bonded to the metal atom to generate electrons as carriers. Therefore, a transistor using an oxide semiconductor containing a large amount of hydrogen tends to have normally-on characteristics. Further, since hydrogen in the oxide semiconductor is likely to move due to stress such as heat and an electric field, if the oxide semiconductor contains a large amount of hydrogen, the reliability of the transistor may deteriorate. In one aspect of the present invention, it is preferable to reduce V O H in the oxide 530 as much as possible to make it highly pure intrinsic or substantially highly pure intrinsic. Thus, V OTo obtain an oxide semiconductor with sufficiently reduced H content, it is important to remove impurities such as water and hydrogen from the oxide semiconductor (sometimes referred to as dehydration and dehydrogenation treatment) and to supply oxygen to the oxide semiconductor to compensate for oxygen deficiencies (sometimes referred to as oxygenation treatment). O By using an oxide semiconductor with sufficiently reduced impurities such as H in the channel formation region of a transistor, stable electrical characteristics can be provided.

[0182] Specifically, as an insulator having an excess oxygen region, it is preferable to use an oxide material in which some of the oxygen is desorbed upon heating. An oxide that desorbs oxygen upon heating is one in which the amount of oxygen desorbed, converted to oxygen atoms, is 1.0 × 10⁻⁶ as determined by TDS (Thermal Desorption Spectroscopy) analysis. 18 atoms / cm 3 Preferably 1.0 × 10 19 atoms / cm 3 More preferably 2.0 × 10 19 atoms / cm 3 Above, or 3.0 × 10 20 atoms / cm 3 The oxide film is as described above. The surface temperature of the film during the TDS analysis is preferably in the range of 100°C to 700°C, or 100°C to 400°C.

[0183] Furthermore, the insulator having the excess oxygen region described above and the oxide 530 may be brought into contact and subjected to one or more of the following treatments: heat treatment, microwave treatment, or RF treatment. By performing this treatment, water or hydrogen in the oxide 530 can be removed. For example, in the oxide 530, a reaction occurs in which the VoH bond is broken, in other words, "V O The reaction H → Vo + H occurs, allowing for dehydrogenation. Some of the hydrogen generated at this time may combine with oxygen to form H2O, which may be removed from oxide 530 or the insulator near oxide 530. In addition, some of the hydrogen may be gettered by conductor 542.

[0184] Furthermore, the above microwave processing is preferably carried out using, for example, a device having a power supply that generates high-density plasma, or a device having a power supply that applies RF to the substrate side. For example, by using an oxygen-containing gas and a high-density plasma, high-density oxygen radicals can be generated, and by applying RF to the substrate side, the oxygen radicals generated by the high-density plasma can be efficiently introduced into the oxide 530 or the insulator near the oxide 530. In addition, the above microwave processing should be carried out at a pressure of 133 Pa or higher, preferably 200 Pa or higher, and more preferably 400 Pa or higher. In addition, as the gas introduced into the device for microwave processing, for example, oxygen and argon should be used, and the oxygen flow rate ratio (O2 / (O2+Ar)) should be 50% or less, preferably 10% to 30% or less.

[0185] Furthermore, during the manufacturing process of the transistor 500, it is preferable to perform a heat treatment while the surface of the oxide 530 is exposed. This heat treatment may be performed, for example, at a temperature of 100°C to 450°C, more preferably 350°C to 400°C. The heat treatment should be performed in an atmosphere of nitrogen gas or an inert gas, or in an atmosphere containing 10 ppm or more, 1% or more, or 10% or more of an oxidizing gas. For example, it is preferable to perform the heat treatment in an oxygen atmosphere. This supplies oxygen to the oxide 530, thereby preventing oxygen deficiency (V O This can reduce the amount of oxygen released. The heat treatment may also be performed under reduced pressure. Alternatively, the heat treatment may be performed in an atmosphere of nitrogen gas or an inert gas, and then in an atmosphere containing 10 ppm or more, 1% or more, or 10% or more of an oxidizing gas to replenish the oxygen that has been removed. Alternatively, the heat treatment may be performed in an atmosphere containing 10 ppm or more, 1% or more, or 10% or more of an oxidizing gas, and then continuously in an atmosphere of nitrogen gas or an inert gas.

[0186] Furthermore, by performing an oxygenation treatment on oxide 530, oxygen vacancies in oxide 530 can be repaired by the supplied oxygen, in other words, the reaction "Vo + O → null" can be promoted. In addition, the supplied oxygen reacts with the hydrogen remaining in oxide 530, removing the hydrogen as H2O (dehydration). As a result, the hydrogen remaining in oxide 530 recombines with the oxygen vacancies and V O This can suppress the formation of H.

[0187] Furthermore, if the insulator 524 has an excess oxygen region, it is preferable that the insulator 522 has a function to suppress the diffusion of oxygen (e.g., oxygen atoms, oxygen molecules, etc.) (i.e., the oxygen is less permeable).

[0188] The insulator 522 has a function of suppressing the diffusion of oxygen and impurities, so the oxygen contained in the oxide 530 does not diffuse toward the insulator 520, which is preferable. Furthermore, it is possible to suppress the reaction of the conductor 503 with the oxygen contained in the insulator 524 and the oxide 530.

[0189] The insulator 522 preferably uses a single-layer or multi-layer insulator containing so-called high-k materials such as aluminum oxide, hafnium oxide, oxides containing aluminum and hafnium (hafnium aluminate), tantalum oxide, zirconium oxide, lead zirconate titanate (PZT), strontium titanate (SrTiO3), or (Ba,Sr)TiO3 (BST). As transistors become smaller and more integrated, thinning of the gate insulating film can lead to problems such as leakage current. By using a high-k material as 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.

[0190] In particular, it is preferable to use an insulator containing an oxide of either aluminum or hafnium, or both, which is an insulating material that has the function of suppressing the diffusion of impurities and oxygen (the above-mentioned oxygen is less permeable). As an insulator containing an oxide of either aluminum or hafnium, or both, it is preferable to use aluminum oxide, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate). When an insulator 522 is formed using such a material, the insulator 522 functions as a layer that suppresses the release of oxygen from the oxide 530 and the mixing of impurities such as hydrogen from the periphery of the transistor 500 into the oxide 530.

[0191] 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 subjected to nitriding treatment. Silicon oxide, silicon oxynitride, or silicon nitride may be laminated onto the above insulators.

[0192] Furthermore, it is preferable that the insulator 520 is thermally stable. For example, silicon oxide and silicon oxynitride are suitable because they are thermally stable. Also, by combining a high-k material insulator with silicon oxide or silicon oxynitride, an insulator 520 or insulator 526 with a thermally stable and high dielectric constant laminated structure can be obtained.

[0193] In Figures 23A and 23B, transistor 500 is shown with insulators 520, 522, and 524 as a second gate insulating film consisting of a three-layer laminated structure. However, the second gate insulating film may have a single-layer, two-layer, or four-layer or more laminated structure. In that case, it is not limited to a laminated structure made of the same material, but may also be a laminated structure made of different materials.

[0194] In transistor 500, it is preferable to use a metal oxide that functions as an oxide semiconductor for the oxide 530 including the channel formation region. For example, as oxide 530, a metal oxide such as In-M-Zn oxide (where element M is one or more selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, or magnesium) is preferable. In particular, the In-M-Zn oxide applicable as oxide 530 is preferably CAAC-OS (c-axis aligned crystalline oxide semiconductor). Alternatively, In-Ga oxide or In-Zn oxide may be used as oxide 530.

[0195] Metal oxides that function as oxide semiconductors can be divided into single-crystal oxide semiconductors and other non-single-crystal oxide semiconductors. Examples of non-single-crystal oxide semiconductors include CAAC-OS, polycrystalline oxide semiconductors, nc-OS (nanocrystalline oxide semiconductor), pseudo-amorphous oxide semiconductors (a-like OS), and amorphous oxide semiconductors.

[0196] CAAC-OS has a c-axis orientation and a crystal structure in which multiple nanocrystals are linked in the ab-plane direction, resulting in a strained structure. The strain refers to the region where the orientation of the lattice arrangement changes between a region with a aligned lattice arrangement and another region with a aligned lattice arrangement, within the region where multiple nanocrystals are linked.

[0197] Nanocrystals are based on a hexagonal structure, but they are not necessarily regular hexagons and may have non-regular hexagonal shapes. Furthermore, under strain, they may have lattice arrangements such as pentagons and heptagons. In CAAC-OS, however, it is difficult to observe clear grain boundaries (also called grain boundaries) even near strain. This indicates that the formation of grain boundaries is suppressed by the strain in the lattice arrangement. This is because CAAC-OS can tolerate strain due to factors such as the sparse arrangement of oxygen atoms in the ab-plane and the change in interatomic bond distances caused by the substitution of metal elements.

[0198] Furthermore, CAAC-OS tends to have a layered crystalline structure (also called a layered structure) in which layers containing indium and oxygen (hereinafter referred to as the In layer) and layers containing element M, zinc, and oxygen (hereinafter referred to as the (M,Zn) layer) are stacked. Note that indium and element M are mutually substitutable, and when element M in the (M,Zn) layer is substituted with indium, it can also be represented as the (In,M,Zn) layer. Similarly, when indium in the In layer is substituted with element M, it can also be represented as the (In,M) layer.

[0199] CAAC-OS is a highly crystalline metal oxide. Furthermore, because it is difficult to identify clear grain boundaries in CAAC-OS, it is less susceptible to the reduction in electron mobility caused by grain boundaries. Also, since the crystallinity of metal oxides can decrease due to impurities and defects, CAAC-OS can be considered a metal oxide with few impurities or defects (such as oxygen vacancies). Therefore, metal oxides containing CAAC-OS have stable physical properties. Consequently, metal oxides containing CAAC-OS are highly heat-resistant and reliable.

[0200] nc-OS exhibits periodicity in atomic arrangement within minute regions (e.g., regions between 1 nm and 10 nm, particularly between 1 nm and 3 nm). Furthermore, nc-OS lacks regularity in crystal orientation between different nanocrystals. Therefore, no orientation is observed across the entire film. Consequently, depending on the analytical method, nc-OS may be indistinguishable from a-like OS or amorphous oxide semiconductors.

[0201] Furthermore, in-Ga-Zn oxide (also known as "IGZO"), a type of metal oxide containing indium, gallium, and zinc, can sometimes adopt a stable structure when formed into the nanocrystals described above. In particular, since IGZO tends to have difficulty growing crystals in the atmosphere, smaller crystals (for example, the nanocrystals mentioned above) may be structurally more stable than larger crystals (here, crystals of several millimeters or several centimeters).

[0202] a-like OS is a metal oxide having a structure between nc-OS and amorphous oxide semiconductors. a-like OS has porous or low-density regions. In other words, a-like OS has lower crystallinity compared to nc-OS and CAAC-OS.

[0203] Oxide semiconductors (metal oxides) can take on diverse structures, each possessing different properties. One embodiment of the present invention may include two or more of the following: amorphous oxide semiconductors, polycrystalline oxide semiconductors, a-like OS, nc-OS, and CAAC-OS.

[0204] Furthermore, it is preferable to use a metal oxide with a low carrier concentration for transistor 500. When the carrier concentration of the metal oxide is low, the impurity concentration in the metal oxide should be lowered to reduce the defect level density. In this specification, a low impurity concentration and a low defect level density are referred to as high-purity intrinsic or substantially high-purity intrinsic. Examples of impurities in metal oxides include hydrogen, nitrogen, alkali metals, alkaline earth metals, iron, nickel, and silicon.

[0205] In particular, hydrogen contained in metal oxides can react with oxygen bonded to metal atoms to form water, thus creating oxygen vacancies within the metal oxide. If oxygen vacancies are present in the channel-forming region of the metal oxide, the transistor may exhibit normally-on characteristics. Furthermore, defects containing hydrogen can function as donors, generating electrons as carriers. In addition, some of the hydrogen can combine with oxygen bonded to metal atoms, generating electrons as carriers. Therefore, transistors using metal oxides with a high hydrogen content tend to exhibit normally-on characteristics.

[0206] Defects where hydrogen fills an oxygen vacancy can function as donors for metal oxides. However, quantitatively evaluating such defects is difficult. Therefore, in metal oxides, evaluation is sometimes done using carrier concentration rather than donor concentration. Accordingly, in this specification, the carrier concentration, assuming no electric field is applied, may be used as a parameter for metal oxides, rather than the donor concentration. In other words, "carrier concentration" as described in this specification may sometimes be rephrased as "donor concentration."

[0207] Therefore, when using metal oxides in oxide 530, it is preferable that the hydrogen content in the metal oxide is reduced as much as possible. Specifically, in metal oxides, the hydrogen concentration obtained by secondary ion mass spectrometry (SIMS) should be 1 × 10⁻⁶. 20 atoms / cm 3 Less than 1 × 10 19 atoms / cm 3 Less than 5x10 18 atoms / cm 3 Less than 1 × 10 18 atoms / cm 3 It should be less than [amount]. By using metal oxides with sufficiently reduced impurities such as hydrogen in the channel formation region of a transistor, stable electrical characteristics can be provided.

[0208] Furthermore, when a metal oxide is used for oxide 530, the carrier concentration of the metal oxide in the channel-forming region is 1 × 10⁻⁶. 18 cm -3 The following is preferable: 1 × 10 17 cm -3 It is more preferable that it be less than 1 × 10 16 cm -3 It is even more preferable that it be less than 1 × 10 13 cm -3 It is even more preferable that it be less than 1 × 10 12 cm -3 It is even more preferable that it be less than . There are no particular limitations on the lower limit of the carrier concentration of the metal oxide in the channel-forming region, but for example, 1 × 10 -9 cm -3 It can be done this way.

[0209] Furthermore, when a metal oxide is used for the oxide 530, contact between the conductor 542 (conductor 542a and conductor 542b) and the oxide 530 may cause oxygen in the oxide 530 to diffuse into the conductor 542, leading to oxidation of the conductor 542. Oxidation of the conductor 542 is highly likely to reduce its conductivity. Note that the diffusion of oxygen from the oxide 530 into the conductor 542 can be rephrased as the conductor 542 absorbing oxygen from the oxide 530.

[0210] Furthermore, oxygen in the oxide 530 may diffuse into the conductor 542 (conductor 542a and conductor 542b), potentially forming a heterogeneous layer between conductor 542a and oxide 530b, and between conductor 542b and oxide 530b. Since this heterogeneous layer contains more oxygen than conductor 542, it is presumed to have insulating properties. In this case, the three-layer structure of conductor 542, this heterogeneous layer, and oxide 530b can be considered a three-layer structure consisting of metal-insulator-semiconductor, and is sometimes called an MIS (Metal-Insulator-Semiconductor) structure, or a diode junction structure mainly composed of an MIS structure.

[0211] Furthermore, the above-mentioned heterogeneous layer is not limited to being formed between the conductor 542 and the oxide 530b. For example, the heterogeneous layer may be formed between the conductor 542 and the oxide 530c, or between the conductor 542 and the oxide 530b, and between the conductor 542 and the oxide 530c.

[0212] Furthermore, it is preferable to use a metal oxide with a band gap of 2 eV or more, preferably 2.5 eV or more, that functions as a channel-forming region in oxide 530. By using a metal oxide with a large band gap in this way, the off-current of the transistor can be reduced.

[0213] By having oxide 530a below oxide 530b, the diffusion of impurities from structures formed below oxide 530a to oxide 530b can be suppressed. Furthermore, by having oxide 530c above oxide 530b, the diffusion of impurities from structures formed above oxide 530c to oxide 530b can be suppressed.

[0214] Furthermore, it is preferable that oxide 530 has a layered structure made up of oxides with different atomic ratios of each metal atom. Specifically, in the metal oxide used for oxide 530a, it is preferable that the atomic ratio of element M in the constituent elements is greater than the atomic ratio of element M in the constituent elements of the metal oxide used for oxide 530b. Also, in the metal oxide used for oxide 530a, it is preferable that the atomic ratio of element M to In is greater than the atomic ratio of element M to In in the metal oxide used for oxide 530b. Furthermore, in the metal oxide used for oxide 530b, it is preferable that the atomic ratio of In to element M is greater than the atomic ratio of In to element M in the metal oxide used for oxide 530a. In addition, oxide 530c can be any metal oxide that can be used for oxide 530a or oxide 530b.

[0215] Furthermore, it is preferable that the energy at the lower end of the conduction band of oxide 530a and oxide 530c is higher than the energy at the lower end of the conduction band of oxide 530b. In other words, it is preferable that the electron affinity of oxide 530a and oxide 530c is smaller than the electron affinity of oxide 530b.

[0216] Here, at the junctions of oxide 530a, oxide 530b, and oxide 530c, the energy level at the lower end of the conduction band changes smoothly. In other words, the energy level at the lower end of the conduction band at the junctions of oxide 530a, oxide 530b, and oxide 530c can be said to change continuously or be continuously joined. To achieve this, it is desirable to lower the defect level density of the mixed layer formed at the interface between oxide 530a and oxide 530b, and at the interface between oxide 530b and oxide 530c.

[0217] Specifically, a mixed layer with a low defect level density can be formed if oxide 530a and oxide 530b, and oxide 530b and oxide 530c, have a common element other than oxygen (as the main component). For example, if oxide 530b is In-Ga-Zn oxide, then In-Ga-Zn oxide, Ga-Zn oxide, gallium oxide, etc., can be used as oxide 530a and oxide 530c.

[0218] In this case, the primary carrier pathway is oxide 530b. By configuring oxides 530a and 530c as described above, the defect level density at the interface between oxide 530a and oxide 530b, and at the interface between oxide 530b and oxide 530c, can be reduced. As a result, the influence of interface scattering on carrier conduction is reduced, and transistor 500 can obtain a high on-current.

[0219] Conductors 542a and 542b, which function as source electrodes and drain electrodes, are provided on the oxide 530b. It is preferable to use metallic elements selected from aluminum, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tungsten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, indium, ruthenium, iridium, strontium, and lanthanum, or alloys composed of the above metallic elements, or alloys combining the above metallic elements, etc. For example, it is preferable to use tantalum nitride, titanium nitride, tungsten, nitrides containing titanium and aluminum, nitrides containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, oxides containing strontium and ruthenium, oxides containing lanthanum and nickel, etc. Furthermore, 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 preferred because they are conductive materials that are resistant to oxidation or maintain conductivity even when absorbing oxygen. In addition, metal nitride films such as tantalum nitride are preferred because they have barrier properties against hydrogen or oxygen.

[0220] Furthermore, although conductors 542a and 542b are shown as single-layer structures in Figure 23, they may also be laminated structures of two or more layers. For example, a tantalum nitride film and a tungsten film may be laminated. Alternatively, a titanium film and an aluminum film may be laminated. In addition, a two-layer structure in which an aluminum film is laminated on a tungsten film, a two-layer structure in which a copper film is laminated on a copper-magnesium-aluminum alloy film, a two-layer structure in which a copper film is laminated on a titanium film, or a two-layer structure in which a copper film is laminated on a tungsten film may also be used.

[0221] Furthermore, there are three-layer structures such as a titanium film or titanium nitride film, an aluminum film or copper film laminated on top of the titanium film or titanium nitride film, and a titanium film or titanium nitride film formed on top of that; and a molybdenum film or molybdenum nitride film, an aluminum film or copper film laminated on top of the molybdenum film or molybdenum nitride film, and a molybdenum film or molybdenum nitride film formed on top of that. Transparent conductive materials containing indium oxide, tin oxide, or zinc oxide may also be used.

[0222] Furthermore, as shown in Figure 23A, regions 543a and 543b may be formed as low-resistance regions at and near the interface between the oxide 530 and the conductor 542a (conductor 542b). In this case, region 543a functions as either a source region or a drain region, and region 543b functions as either a source region or a drain region. In addition, a channel-forming region is formed in the region sandwiched between regions 543a and 543b.

[0223] By providing the conductor 542a (conductor 542b) in contact with the oxide 530, the oxygen concentration in region 543a (region 543b) may be reduced. In addition, a metal compound layer containing the metal contained in the conductor 542a (conductor 542b) and the components of the oxide 530 may be formed in region 543a (region 543b). In such cases, the carrier density in region 543a (region 543b) increases, and region 543a (region 543b) becomes a low-resistance region.

[0224] The insulator 544 is provided so as to cover the conductors 542a and 542b, thereby suppressing oxidation of the conductors 542a and 542b. In this case, 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.

[0225] As the insulator 544, one or more metal oxides selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, neodymium, lanthanum, or magnesium can be used. Alternatively, silicon nitride or silicon nitride can also be used as the insulator 544.

[0226] In particular, it is preferable to use an insulator 544 that contains an oxide of either aluminum or hafnium, or both, such as aluminum oxide, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate). Hafnium aluminate is especially preferable because it has higher heat resistance than hafnium oxide film. Therefore, it is preferable because it is less likely to crystallize during heat treatment in a later process. Note that if the conductors 542a and 542b are made of oxidation-resistant materials, or if their conductivity does not significantly decrease even when oxygen is absorbed, the insulator 544 is not an essential component. It should be designed appropriately according to the desired transistor characteristics.

[0227] The presence of the insulator 544 suppresses the diffusion of water and other impurities such as hydrogen contained in the insulator 580 to the oxide 530b via the oxide 530c and insulator 550. Furthermore, it suppresses the oxidation of the conductor 560 due to excess oxygen present in the insulator 580.

[0228] The insulator 550 functions as a first gate insulating film. It is preferable that the insulator 550 is placed in contact with the inside (top and side) of the oxide 530c. It is preferable that the insulator 550 is formed using an insulator that contains an excess of oxygen and releases oxygen upon heating, similar to the insulator 524 described above.

[0229] Specifically, silicon oxide with excess oxygen, silicon oxide nitride, silicon nitride, silicon nitride, silicon oxide with added fluorine, silicon oxide with added carbon, silicon oxide with added carbon and nitrogen, and silicon oxide with vacancies can be used. Silicon oxide and silicon oxide nitride are particularly preferred because they are stable to heat.

[0230] By providing an insulator 550, which releases oxygen upon heating, in contact with the upper surface of oxide 530c, oxygen can be effectively supplied from the insulator 550 to the channel-forming region of oxide 530b through oxide 530c. Furthermore, similar to the insulator 524, it is preferable that the concentration of impurities such as water or hydrogen in the insulator 550 is reduced. The film thickness of the insulator 550 is preferably between 1 nm and 20 nm.

[0231] Furthermore, in order to efficiently supply excess oxygen from the insulator 550 to the oxide 530, a metal oxide may be provided between the insulator 550 and the conductor 560. It is preferable that the metal oxide suppresses the diffusion of oxygen from the insulator 550 to the conductor 560. By providing a metal oxide that suppresses the diffusion of oxygen, the diffusion of excess oxygen from the insulator 550 to the conductor 560 is suppressed. In other words, the 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, any material that can be used for the insulator 544 may be used.

[0232] Furthermore, the insulator 550 may have a multilayer structure, similar to the second gate insulating film. As transistors become smaller and more integrated, thinning of the gate insulating film can lead to problems such as leakage current. Therefore, by using a multilayer structure of a high-k material and a thermally stable material for the insulator that functions as the gate insulating film, it becomes possible to reduce the gate potential during transistor operation while maintaining the physical film thickness. In addition, a multilayer structure that is thermally stable and has a high dielectric constant can be achieved.

[0233] The conductor 560, which functions as the first gate electrode, is shown as a two-layer structure in Figures 23A and 23B, but it may also be a single-layer structure or a stacked structure of three or more layers.

[0234] It is preferable to use a conductive material for the conductor 560a that has the function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (N2O, NO, NO2, etc.), and copper atoms. Alternatively, it is preferable to use a conductive material that has the function of suppressing the diffusion of oxygen (for example, at least one such as oxygen atoms or oxygen molecules). By having the function of suppressing the diffusion of oxygen in the conductor 560a, it is possible to suppress the oxidation of the conductor 560b by the oxygen contained in the insulator 550, which reduces the conductivity. As a conductive material that has the function of suppressing the diffusion of oxygen, it is preferable to use, for example, tantalum, tantalum nitride, ruthenium, or ruthenium oxide. Furthermore, an oxide semiconductor applicable to the oxide 530 can be used as the conductor 560a. In that case, by depositing the conductor 560b by sputtering, the electrical resistance value of the conductor 560a can be reduced to make it a conductor. This can be called an OC (Oxide Conductor) electrode.

[0235] Furthermore, it is preferable that the conductor 560b is made of a conductive material mainly composed of tungsten, copper, or aluminum. Also, since the conductor 560b functions as wiring, it is preferable to use a conductor with high conductivity. For example, a conductive material mainly composed of tungsten, copper, or aluminum can be used. The conductor 560b may also be in a laminated structure, for example, a laminated structure of titanium or titanium nitride and the above conductive material.

[0236] The insulator 580 is provided on the conductors 542a and 542b via the insulator 544. The insulator 580 preferably has an excess oxygen region. For example, the insulator 580 preferably has silicon oxide, silicon oxynitride, silicon nitride, silicon nitride, fluorine-added silicon oxide, carbon-added silicon oxide, carbon and nitrogen-added silicon oxide, porous silicon oxide, or a resin. Silicon oxide and silicon oxynitride are particularly preferred because they are thermally stable. Silicon oxide and porous silicon oxide are particularly preferred because they can easily form an excess oxygen region in a later process.

[0237] The insulator 580 preferably has an excess oxygen region. By providing the insulator 580, which releases oxygen upon heating, in contact with the oxide 530c, oxygen in the insulator 580 can be efficiently supplied to the oxide 530 through the oxide 530c. It is preferable that the concentration of impurities such as water or hydrogen in the insulator 580 is reduced.

[0238] The opening in the insulator 580 is formed superimposed on the region between the conductors 542a and 542b. As a result, the conductor 560 is formed to be embedded in the opening in the insulator 580 and in the region sandwiched between the conductors 542a and 542b.

[0239] When miniaturizing semiconductor devices, it is necessary to shorten the gate length, but it is also necessary to ensure that the conductivity of the conductor 560 does not decrease. If the film thickness of the conductor 560 is increased to achieve this, the conductor 560 may take on a shape with a high aspect ratio. In this embodiment, since the conductor 560 is embedded in the opening of the insulator 580, even if the conductor 560 has a shape with a high aspect ratio, it can be formed without the conductor 560 collapsing during the manufacturing process.

[0240] The insulator 574 is preferably provided in contact with the upper surface of the insulator 580, the upper surface of the conductor 560, and the upper surface of the insulator 550. By depositing the insulator 574 by sputtering, an excess oxygen region can be created in the insulator 550 and the insulator 580. This allows oxygen to be supplied to the oxide 530 from the excess oxygen region.

[0241] For example, as the insulator 574, one or more metal oxides selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, or magnesium can be used.

[0242] In particular, aluminum oxide has high barrier properties and can suppress the diffusion of hydrogen and nitrogen even in thin films between 0.5 nm and 3.0 nm in thickness. Therefore, aluminum oxide deposited by sputtering can function as both an oxygen source and a barrier film against impurities such as hydrogen.

[0243] Furthermore, it is preferable to provide an insulator 581 that functions as an interlayer film on top of the insulator 574. Similar to the insulator 524, it is preferable that the insulator 581 has a reduced concentration of impurities such as water or hydrogen in the film.

[0244] Furthermore, conductors 540a and 540b are placed in the openings formed in insulators 581, 574, 580, and 544. Conductors 540a and 540b are provided facing each other with conductor 560 in between. Conductors 540a and 540b have the same configuration as conductors 546 and 548, which will be described later.

[0245] An insulator 582 is provided on the insulator 581. It is preferable that the insulator 582 be made of a material that has barrier properties against oxygen and hydrogen. Therefore, the same material as that used for the insulator 514 can be used for the insulator 582. For example, it is preferable that the insulator 582 be made of a metal oxide such as aluminum oxide, hafnium oxide, or tantalum oxide.

[0246] In particular, aluminum oxide exhibits a high barrier effect, preventing the penetration of both oxygen and impurities such as hydrogen and moisture, which can cause fluctuations in the electrical properties of transistors. Therefore, aluminum oxide can prevent the ingress of impurities such as hydrogen and moisture into the transistor 500 during and after the transistor manufacturing process. It can also suppress the release of oxygen from the oxides constituting the transistor 500. For this reason, it is suitable for use as a protective film for transistor 500.

[0247] Furthermore, an insulator 586 is provided on the insulator 582. The insulator 586 can be made of the same material as the insulator 320. By applying materials with relatively low dielectric constants to these insulators, parasitic capacitance between the wiring can be reduced. For example, silicon oxide films or silicon oxynitride films can be used as the insulator 586.

[0248] Furthermore, insulators 520, 522, 524, 544, 580, 574, 581, 582, and 586 have conductors 546 and 548 embedded in them.

[0249] Conductors 546 and 548 function as plugs or wires for connecting to the capacitive element 600, transistor 500, or transistor 300. Conductors 546 and 548 can be provided using the same materials as conductors 328 and 330.

[0250] Furthermore, after the formation of the transistor 500, an opening may be formed to surround the transistor 500, and an insulator with high barrier properties against hydrogen or water may be formed to cover the opening. By enclosing the transistor 500 with the above-mentioned high-barrier insulator, it is possible to prevent moisture and hydrogen from entering from the outside. Alternatively, multiple transistors 500 may be encased together with an insulator with high barrier properties against hydrogen or water. When forming an opening to surround the transistor 500, for example, forming an opening that reaches the insulator 522 or insulator 514, and forming the above-mentioned high-barrier insulator in contact with the insulator 522 or insulator 514 is preferable because it can also serve as part of the manufacturing process for the transistor 500. For example, the same material as insulator 522 or insulator 514 may be used as the insulator with high barrier properties against hydrogen or water.

[0251] Next, a capacitive element 600 is provided above the transistor 500. The capacitive element 600 has a conductor 610, a conductor 620, and an insulator 630.

[0252] Furthermore, a conductor 612 may be provided on the conductors 546 and 548. The conductor 612 functions as a plug or wiring for connecting to the transistor 500. The conductor 610 functions as an electrode for the capacitive element 600. Note that the conductors 612 and 610 can be formed simultaneously.

[0253] Conductors 612 and 610 can be made of a metal film containing an element selected from molybdenum, titanium, tantalum, tungsten, aluminum, copper, chromium, neodymium, or scandium, or a metal nitride film (tantalum nitride film, titanium nitride film, molybdenum nitride film, tungsten nitride film) composed of the above elements. Alternatively, conductive materials such as 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, or indium tin oxide with silicon oxide added can also be used.

[0254] In this embodiment, the conductors 612 and 610 are shown as single-layer structures, but the embodiment is not limited to this configuration and may be a laminated structure of two or more layers. For example, a conductor with high adhesion to both the barrier conductor and the highly conductive conductor may be formed between the barrier conductor and the highly conductive conductor.

[0255] A conductor 620 is provided so as to overlap the conductor 610 via an insulator 630. The conductor 620 can be made of a conductive material such as a metal, alloy, or metal oxide. It is preferable to use a high-melting-point material such as tungsten or molybdenum that provides both heat resistance and conductivity, and tungsten is particularly preferable. When forming the conductor simultaneously with other structures, low-resistance metallic materials such as Cu (copper) or Al (aluminum) may be used.

[0256] An insulator 640 is provided on the conductor 620 and the insulator 630. The insulator 640 can be provided using the same material as the insulator 320. The insulator 640 may also function as a planarizing film that covers the uneven shape below it.

[0257] By using this structure, it is possible to achieve miniaturization or high integration in semiconductor devices using transistors having oxide semiconductors.

[0258] This embodiment can be implemented in appropriate combination with the configurations described in other embodiments.

[0259] (Embodiment 4) In this embodiment, as an example of a semiconductor device, an IC chip, an electronic component, an electronic device, etc. will be described.

[0260] <Example of manufacturing method of electronic component> FIG. 24A is a flowchart showing an example of a method for manufacturing an electronic component. An electronic component is also referred to as a semiconductor package or an IC package. This electronic component has a plurality of standards and names depending on the terminal extraction direction and the shape of the terminals. Therefore, in this embodiment, an example thereof will be described. The electronic component described below corresponds to an electronic component including each transistor of the delay circuit constituting the semiconductor device.

[0261] A semiconductor device composed of transistors is completed by attaching a plurality of components that can be detached from the printed board through an assembly process (post-process). The post-process can be completed by going through each process shown in FIG. 24A. Specifically, after the element substrate obtained in the previous process is completed (step ST71), the back surface of the substrate is polished. At this stage, the substrate is thinned to reduce the warping of the substrate in the previous process and to miniaturize the components. Next, a dicing process for separating the substrate into a plurality of chips is performed (step ST72).

[0262] FIG. 24B is a top view of the semiconductor wafer 7100 before the dicing process is performed. FIG. 24C is a partially enlarged view of FIG. 24B. A plurality of circuit regions 7102 are provided on the semiconductor wafer 7100. For example, a semiconductor device according to the embodiment of the present invention is provided in the circuit region 7102.

[0263] Multiple circuit regions 7102 are each surrounded by isolation regions 7104. A separation line (also called a "dicing line") 7106 is set at a position overlapping with the isolation regions 7104. In the dicing process ST72, the semiconductor wafer 7100 is cut along the separation line 7106, thereby cutting out the chip 7110 containing the circuit regions 7102 from the semiconductor wafer 7100. Figure 24D shows an enlarged view of the chip 7110.

[0264] A conductive layer or semiconductor layer may be provided in the isolation region 7104. By providing a conductive layer or semiconductor layer in the isolation region 7104, ESD that may occur during the dicing process can be mitigated, and a decrease in yield caused by the dicing process can be prevented. In general, the dicing process is carried out while supplying pure water, in which carbon dioxide or the like has been dissolved to lower its resistivity, to the cutting area for purposes such as cooling the substrate, removing shavings, and preventing static electricity. By providing a conductive layer or semiconductor layer in the isolation region 7104, the amount of pure water used can be reduced. Therefore, the production cost of semiconductor devices can be reduced. In addition, the productivity of semiconductor devices can be increased.

[0265] After step ST72, a die bonding process is performed in which the separated chips are individually picked up, mounted on the lead frame, and joined (step ST73). The method of bonding the chips to the lead frame in the die bonding process should be selected to suit the product. For example, bonding may be done with resin or tape. The die bonding process may also involve mounting and bonding the chips on an interposer. In the wire bonding process, the leads of the lead frame and the electrodes on the chips are electrically connected with thin metal wires (step ST74). Silver or gold wires can be used for the thin metal wires. Wire bonding may be either ball bonding or wedge bonding.

[0266] The wire-bonded chips undergo a molding process (step ST75) in which they are sealed with epoxy resin or the like. The molding process fills the inside of the electronic component with resin, reducing damage to the internal circuitry and wires from mechanical external forces, and also reducing degradation of properties due to moisture and dust. The leads of the lead frame are plated. Then the leads are cut and shaped (step ST76). The plating prevents rust on the leads and allows for more reliable soldering when mounting them on a printed circuit board later. The surface of the package is printed (marked) (step ST77). After the inspection process (step ST78), the electronic component is completed (step ST79).

[0267] Figure 24E shows a schematic perspective view of the completed electronic component. Figure 24E shows a schematic perspective view of a QFP (Quad Flat Package) as an example of an electronic component. As shown in Figure 24E, the electronic component 7000 has leads 7001 and a chip 7110.

[0268] The electronic component 7000 is mounted, for example, on a printed circuit board 7002. Multiple such electronic components 7000 are combined and electrically connected on the printed circuit board 7002, allowing them to be mounted in an electronic device. The completed circuit board 7004 is installed inside the electronic device or the like.

[0269] Electronic component 7000 can be applied to electronic components (IC chips) in a wide range of electronic devices, including digital signal processing, software-defined radio, avionics (electronic equipment related to aviation such as communication equipment, navigation systems, autopilots, and flight management systems), ASIC prototyping, medical image processing, speech recognition, cryptography, bioinformatics (biological information science), mechanical device emulators, and radio telescopes in radio astronomy. Examples of such electronic devices include cameras (video cameras, digital still cameras, etc.), display devices, personal computers (PCs), mobile phones, game consoles including portable ones, portable information terminals (smartphones, tablet information terminals, etc.), e-book readers, wearable information terminals (watches, head-mounted devices, goggles, glasses, armbands, bracelets, necklaces, etc.), navigation systems, sound playback devices (car audio, digital audio players, etc.), photocopiers, fax machines, printers, multifunction printers, automated teller machines (ATMs), vending machines, and home electrical appliances.

[0270] <Examples of application to electronic devices> Next, we will explain how to apply the above-mentioned electronic components to electronic devices or enclosures such as mobile devices and structures.

[0271] Figure 25A illustrates the HMD910 (HMD: Head Mounted Display). The HMD910 has an opening 912 in part of its housing 911. The HMD910 also includes a separator 913, an operation switch 914, an external storage means 915, a speaker 916, an external audio output terminal 917, a fixing device 920, a display means 921 (display means 921R and display means 921L), and a sound source detection device 922 (sound source detection device 922[1] and sound source detection device 922[2]).

[0272] The sound source detection device 922 can be the sound source detection device 110 shown in the above embodiment. The HMD 910 is also equipped with the above-mentioned electronic components having functions such as the sound source detection device 922.

[0273] Users of the HMD910 can view images displayed on the display means 921 by wearing the HMD910 on their heads. By equipping the HMD910 with a sound source detection device 922, it can detect changes in the surrounding environment while viewing. It can also emit a warning sound as needed. Furthermore, it can display a warning on the display means 921 as needed. By equipping the HMD910 with a sound source detection device 922, users can concentrate on viewing the images with peace of mind, thereby achieving a higher level of immersion.

[0274] Figure 25B illustrates the scooter 950. The scooter 950 has side mirrors 951, a secondary battery 952, turn signals 953, and a sound source detection device 955. The secondary battery 952 is housed in the under-seat storage compartment 954.

[0275] The sound source detection device 955 can be the sound source detection device 110 shown in the above embodiment. Furthermore, the scooter 950 is equipped with the above-mentioned electronic components having functions such as the sound source detection device 955. By providing the sound source detection device 955 to the scooter 950, driving safety can be improved.

[0276] This embodiment can be implemented in appropriate combination with the configurations described in other embodiments.

[0277] (Embodiment 5) This embodiment describes a market scenario in which OS transistors can be used.

[0278] <Market Image> First, Fig. 26 shows the market image where an OS transistor can be used. In Fig. 26, region 701 represents the product region (OS Display) applicable to a display using an OS transistor, region 702 represents the product region (OS LSI analog) where LSI (Large Scale Integration) using an OS transistor is applicable to analog processing, and region 703 represents the product region (OS LSI digital) where LSI using an OS transistor is applicable to digital processing. The OS transistor can be suitably used in three regions, namely region 701, region 702, and region 703 shown in Fig. 26, or rather, in three large markets.

[0279] Also, in Fig. 26, region 704 represents the region where region 701 and region 702 overlap, region 705 represents the region where region 702 and region 703 overlap, region 706 represents the region where region 701 and region 703 overlap, and region 707 represents the region where region 701, region 702, and region 703 all overlap.

[0280] In OS Display, for example, FET structures such as a Bottom Gate type OS FET (BG OSFET) and a Top Gate type OS FET (TG OS FET) can be suitably used. Note that the Bottom Gate type OS FET includes a channel etch type FET and a channel protection type FET. Also, the Top Gate type OS FET includes a TGSA (Top Gate Self - Aligned) type FET.

[0281] Also, in OS LSI analog and OS LSI digital, for example, a Gate Last type OS FET (GL OS FET) can be suitably used.

[0282] The transistors mentioned above include, for example, single-gate transistors with one gate electrode, dual-gate transistors with two gate electrodes, or transistors with three or more gate electrodes. Among dual-gate transistors, S-channel (surrounded channel) transistors are particularly preferred.

[0283] In this specification, an S-channel transistor refers to a transistor structure in which the channel formation region is electrically surrounded by the electric fields of one and the other of a pair of gate electrodes. In this specification, the surrounded channel (S-channel) structure is characterized in that the sides and periphery of the oxide 530 in contact with the conductors 542a and 542b, which function as the source and drain electrodes, are I-type, just like the channel formation region. Furthermore, since the sides and periphery of the oxide 530 in contact with the conductors 542a and 542b are in contact with the insulator 544, they can also be I-type, just like the channel formation region. In this specification, I-type can be treated the same as the high-purity intrinsic material described above. Also, the S-channel structure disclosed in this specification is different from the Fin-type structure and the planar-type structure. By adopting the S-channel structure, it is possible to increase resistance to short-channel effects, or in other words, to create a transistor in which short-channel effects are less likely to occur.

[0284] Furthermore, products included in OS Display (area 701) include products having LCD (liquid crystal display), EL (electroluminescence), and LED (light-emitting diode) as display devices. Alternatively, it is also preferable to combine the above display devices with Q-Dot (quantum dot).

[0285] In this embodiment, EL includes organic EL and inorganic EL. Also, in this embodiment, LED includes microLED, miniLED and macroLED. In this specification, the chip area is 10,000 μm². 2 The following light-emitting diodes are microLEDs, with a chip area of ​​10,000 μm². 2 Larger by 1mm 2 The following light-emitting diodes are mini LEDs, with a chip area of ​​1mm². 2 Larger light-emitting diodes are sometimes referred to as macro LEDs.

[0286] Furthermore, products included in OS LSI analog (area 702) include sound source localization devices that support a wide range of frequencies (for example, audible sounds with frequencies from 20Hz to 20kHz, or ultrasound above 20kHz), as well as battery control devices (battery control ICs, battery protection ICs, or battery management systems).

[0287] Furthermore, products included in OS LSI digital (area 703) include memory devices, CPU (Central Processing Unit) devices, GPU (Graphics Processing Unit) devices, FPGA (field-programmable gate array) devices, power devices, hybrid devices that stack or mix OS LSI and Si LSI, and light-emitting devices.

[0288] Furthermore, products included in area 704 include display devices having an infrared sensor or a near-infrared sensor in the display area, or signal processing devices with sensors having OS FETs, or implantable biosensor devices. Furthermore, products included in area 705 include processing circuits having A / D (Analog to Digital) conversion circuits, or AI (Artificial Intelligence) devices having such processing circuits. Furthermore, products included in area 706 include display devices to which Pixel AI technology is applied. In this specification, Pixel AI technology refers to a technology that utilizes memory composed of OS FETs mounted in the pixel circuit of a display.

[0289] Furthermore, products included in area 707 include composite products that combine any of the products included in areas 701 to 706.

[0290] As described above, a semiconductor device according to one aspect of the present invention can be applied to a wide range of product areas, as shown in Figure 26. In other words, a semiconductor device according to one aspect of the present invention can be applied to many markets.

[0291] This embodiment can be implemented in appropriate combination with the configurations described in other embodiments. [Explanation of symbols]

[0292] 100: Vehicle, 101: Transistor, 102: Transistor, 103: Transistor, 104: Transistor, 108: Airbag, 110: Sound source detection device, 111: Microphone array, 112: Delay circuit group, 113: Signal processing circuit, 114: ADC, 115: Digital processing circuit, 116: Microphone, 117: Delay circuit, 120: Control device, 121: Memory device, 122: Processing unit, 123: Neural network, 124: Neuron, 130: Signal output device, 131: Airbag device, 132: Airbag device, 133a: Airbag device, 133b: Airbag device, 134a: Airbag device, 134b: Airbag device, 140: Sensor, 151: Steering wheel, 152: Dashboard, 200: Vehicle warning device

Claims

[Claim 1] A mobile device comprising a sound source detection device, a control device, and a crew protection device, The sound source detection device has the function of identifying the location of the sound source of an external sound, The sound source detection device comprises a first microphone, a second microphone, a first delay circuit, a second delay circuit, and a signal processing circuit. The first delay circuit comprises a first selection circuit, a second selection circuit, and a first plurality of holding circuits. The second delay circuit comprises a third selection circuit, a fourth selection circuit, and a second plurality of holding circuits. The sound waves emitted by the sound source are picked up by the first microphone and converted into a first sound source signal, and are also picked up by the second microphone and converted into a second sound source signal. The first sound source signal is supplied to the first selection circuit. The second sound source signal is supplied to the third selection circuit. When the first selection signal becomes high level, the transistor in the first selection circuit turns on, and a first analog voltage corresponding to the first sound source signal is written to the first plurality of holding circuits. When the first selection signal becomes low level, the transistor in the first selection circuit turns off, and the first analog voltage is held in the first plurality of holding circuits. When the second selection signal becomes high level, the transistor in the third selection circuit turns on, and the second analog voltage corresponding to the second sound source signal is written to the second plurality of holding circuits. When the second selection signal becomes low level, the transistor in the third selection circuit turns off, and the second analog voltage is held in the second plurality of holding circuits. The second selection circuit, when the third selection signal becomes high level, turns on a transistor in the second selection circuit, thereby selecting one of the first analog voltages held by the first plurality of holding circuits and outputting it to the signal processing circuit. The fourth selection circuit, when the fourth selection signal becomes high level, turns on the transistor of the second selection circuit, thereby selecting one of the second analog voltages held by the second plurality of holding circuits and outputting it to the signal processing circuit. The transistors in the first plurality of holding circuits and the second plurality of holding circuits are made of oxide semiconductors, and the device is for a mobile body.

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