Semiconductor Devices

Abstract

To provide a semiconductor device capable of measuring a minute current.SOLUTION: In a semiconductor device including an operational amplifier and a diode element. an inverting input terminal of the operational amplifier and an input terminal of the diode element are electrically connected to a first terminal to which a current is input, and an output terminal of the operational amplifier and an output terminal of the diode element are electrically connected to a second terminal from which a voltage is output. As the diode element, a diode-connected transistor including a metal oxide in a channel formation region is used. Since an off-state current of the transistor is extremely low, a minute current can be caused to flow between the first terminal and the second terminal. Thus, by outputting a voltage from the second terminal, a minute current flowing from this voltage through the first terminal can be estimated.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] One embodiment of the present invention relates to a semiconductor device, a semiconductor wafer, and an electronic device.

[0002] Note that one embodiment of the present invention is not limited to the above technical field. The technical field of the invention disclosed in this specification relates to an object, a method, or a manufacturing method. Alternatively, one embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter. Therefore, more specifically, examples of the technical field of one embodiment of the present invention disclosed in this specification include semiconductor devices, display devices, liquid crystal display devices, light-emitting devices, power storage devices, imaging devices, memory devices, signal processing devices, processors, electronic devices, systems, driving methods thereof, manufacturing methods thereof, and testing methods thereof. [Background technology]

[0003] A sensor has the function of converting the detected object into an electrical signal or the like, and by converting information about the object into an electrical signal, the information about the object can be processed by another device, such as visually displaying the information about the object using a display device or storing the information about the object using a storage device. Specifically, a sensor converts the detected object into a current value and measures the current value, thereby observing quantities related to the object. Apparatuses and methods for measuring current are disclosed in Patent Document 1, etc. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-137359 Summary of the Invention [Problem to be solved by the invention]

[0005] In a sensor that detects a physical quantity or the like and generates a current, one example of a means for reading out the current is a method using an inverting amplifier circuit. With this method, the current is used as an input current, a voltage is output by the inverting amplifier circuit, and the value of the input current is measured from the voltage. However, in recent years, efforts have been made to miniaturize sensors and to reduce the current output by sensors, creating a need for a circuit that can accurately read out even minute currents.

[0006] An object of one embodiment of the present invention is to provide a semiconductor device or the like that can measure minute current.Another object of one embodiment of the present invention is to provide a novel semiconductor device or the like.Another object of one embodiment of the present invention is to provide a novel electronic device or the like that includes the semiconductor device.

[0007] Note that the problems of one embodiment of the present invention are not limited to the problems listed above. The problems listed above do not preclude the existence of other problems. Note that the other problems are problems not mentioned in this section, which will be described below. Problems not mentioned in this section can be derived by a person skilled in the art from the description in the specification or drawings, and can be appropriately extracted from these descriptions. Note that one embodiment of the present invention solves at least one of the problems listed above and other problems. Note that one embodiment of the present invention does not necessarily solve all of the problems listed above and other problems. [Means for solving the problem]

[0008] (1) One embodiment of the present invention is a semiconductor device including a transistor and an operational amplifier, in which an inverting input terminal of the operational amplifier is electrically connected to a first terminal and a gate of the transistor, an output terminal of the operational amplifier is electrically connected to a second terminal of the transistor, and the transistor has a metal oxide in a channel formation region.

[0009] (2) Alternatively, one embodiment of the present invention is a transistor having the structure (1) in which the off-state current of the transistor is 1.0×10 -12A semiconductor device with a rating of A or less.

[0010] (3) Alternatively, according to another embodiment of the present invention, in the structure (1), the transistor has a back gate. A potential that shifts the threshold voltage of the transistor to the positive side is input to the back gate, thereby reducing the off-state current of the transistor by 1.0×10 -15 A semiconductor device having the function of reducing the temperature to below A.

[0011] (4) Alternatively, one embodiment of the present invention includes a first circuit and an operational amplifier, wherein an inverting input terminal of the operational amplifier is electrically connected to a first terminal of the first circuit and an output terminal of the operational amplifier is electrically connected to a second terminal of the first circuit, the first circuit includes a transistor, and the transistor has a metal oxide in a channel formation region, and the first circuit has a capacitance of 1.0×10 between the first terminal and the second terminal. -12 It is a semiconductor device that has the function of passing a current of 1 A or less.

[0012] (5) Another embodiment of the present invention is a semiconductor device having the above structure (4), in which the transistor has a back gate.

[0013] (6) Alternatively, one aspect of the present invention is a semiconductor device having any one of the above structures (1) to (5), in which the metal oxide is an In-M-Zn oxide (the element M is one or more elements selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, or magnesium).

[0014] (7) Another embodiment of the present invention is a semiconductor wafer including a plurality of semiconductor devices according to any one of (1) to (6) above and having a region for dicing.

[0015] (8) Another embodiment of the present invention is an electronic device including the semiconductor device according to any one of (1) to (6), a detection unit, and a housing, in which the detection unit has a function of outputting a current by detecting an object to be detected, and the current is input to the semiconductor device.

[0016] In this specification and the like, a semiconductor device is a device that utilizes semiconductor characteristics, and refers to a circuit including a semiconductor element (transistor, diode, photodiode, etc.), a device having such a circuit, etc. It also refers to any device that can function by utilizing semiconductor characteristics. For example, an integrated circuit, a chip including an integrated circuit, or an electronic component in which a chip is housed in a package are examples of semiconductor devices. Furthermore, memory devices, display devices, light-emitting devices, lighting devices, electronic devices, etc. are themselves semiconductor devices and may include semiconductor devices.

[0017] Furthermore, when it is stated in this specification that X and Y are connected, it is understood that the following cases are disclosed in this specification: when X and Y are electrically connected, when X and Y are functionally connected, and when X and Y are directly connected. Therefore, it is not limited to a predetermined connection relationship, for example, a connection relationship shown in a figure or text, and it is understood that connections other than those shown in a figure or text are also disclosed in a figure or text. X and Y are understood to be objects (e.g., a device, an element, a circuit, wiring, an electrode, a terminal, a conductive film, a layer, etc.).

[0018] As an example of a case where X and Y are electrically connected, one or more elements (for example, a switch, a transistor, a capacitance element, an inductor, a resistance element, a diode, a display element, a light-emitting element, a load, etc.) that enable the electrical connection between X and Y can be connected between X and Y. The switch has a function of controlling on / off. In other words, the switch has a function of being in a conductive state (on state) or a non-conductive state (off state), and controls whether or not a current flows.

[0019] As an example of a case where X and Y are functionally connected, one or more circuits that enable the functional connection between X and Y (for example, logic circuits (inverters, NAND circuits, NOR circuits, etc.), signal conversion circuits (DA conversion circuits, AD conversion circuits, gamma correction circuits, etc.), potential level conversion circuits (power supply circuits (boosting circuits, step-down circuits, etc.), level shifter circuits that change the potential level of signals, etc.), voltage sources, current sources, switching circuits, amplifier circuits (circuits that can increase the signal amplitude or current amount, operational amplifiers, differential amplifier circuits, source follower circuits, buffer circuits, etc.), signal generation circuits, memory circuits, control circuits, etc.) can be connected between X and Y. As an example, even if another circuit is sandwiched between X and Y, X and Y are considered to be functionally connected if a signal output from X is transmitted to Y.

[0020] Note that when it is explicitly stated that X and Y are electrically connected, this includes the case where X and Y are electrically connected (i.e., when they are connected with another element or another circuit between them), the case where X and Y are functionally connected (i.e., when they are functionally connected with another circuit between them), and the case where X and Y are directly connected (i.e., when they are connected without another element or another circuit between them). In other words, when it is explicitly stated that X and Y are electrically connected, it is the same as when it is simply explicitly stated that they are connected.

[0021] Furthermore, for example, it can be expressed as follows: "X, Y, and the source (or first terminal, etc.) and drain (or second terminal, etc.) of the transistor are electrically connected to each other, and are electrically connected in the order of X, the source (or first terminal, etc.) of the transistor, the drain (or second terminal, etc.) of the transistor, and Y." Or, it can be expressed as follows: "The source (or first terminal, etc.) of the transistor is electrically connected to X, and the drain (or second terminal, etc.) of the transistor is electrically connected to Y, and X, the source (or first terminal, etc.) of the transistor, the drain (or second terminal, etc.) of the transistor, and Y are electrically connected in this order." Or, it can be expressed as follows: "X is electrically connected to Y via the source (or first terminal, etc.) and drain (or second terminal, etc.) of the transistor, and X, the source (or first terminal, etc.) of the transistor, the drain (or second terminal, etc.) of the transistor, and Y are provided in this connection order." By using expressions similar to these examples to define the order of connections in a circuit configuration, the source (or first terminal, etc.) and drain (or second terminal, etc.) of a transistor can be distinguished and the technical scope can be determined. Note that these expressions are merely examples and are not limiting. Here, X and Y are assumed to be objects (e.g., devices, elements, circuits, wiring, electrodes, terminals, conductive films, layers, etc.).

[0022] Note that even when independent components are shown electrically connected in a circuit diagram, one component may have the functions of multiple components. For example, if part of a wiring also functions as an electrode, one conductive film has the functions of both wiring and an electrode. Therefore, the term "electrically connected" in this specification also includes such cases where one conductive film has the functions of multiple components.

[0023] Furthermore, in this specification and the like, a "resistance element" can refer to, for example, a circuit element, wiring, etc. having a resistance value higher than 0 Ω. Therefore, in this specification and the like, a "resistance element" can include wiring having a resistance value, a transistor in which a current flows between the source and drain, a diode, a coil, etc. Therefore, the term "resistance element" can be replaced with terms such as "resistance," "load," or "region having a resistance value," and conversely, the terms "resistance," "load," or "region having a resistance value" can be replaced with terms such as "resistance element." The resistance value can be, for example, preferably 1 mΩ or more and 10 Ω or less, more preferably 5 mΩ or more and 5 Ω or less, and even more preferably 10 mΩ or more and 1 Ω or less. Furthermore, for example, a resistance value can be replaced with a resistance value of 1 Ω or more and 1×10 9 It may be set to Ω or less.

[0024] Furthermore, in this specification, the term "capacitive element" can refer to, for example, a circuit element having a capacitance value greater than 0 F, as well as a region of a wiring having a capacitance value, parasitic capacitance, or the gate capacitance of a transistor. Therefore, in this specification, the term "capacitive element" may refer not only to a circuit element including a pair of electrodes and a dielectric between the electrodes, but also to a parasitic capacitance appearing between wiring and the wiring, or a gate capacitance appearing between one of the source or drain of a transistor and the gate. Furthermore, terms such as "capacitive element," "parasitic capacitance," and "gate capacitance" can be replaced with terms such as "capacitance," and conversely, the term "capacitance" can be replaced with terms such as "capacitive element," "parasitic capacitance," and "gate capacitance." Furthermore, the term "pair of electrodes" in "capacitance" can be replaced with "pair of conductors," "pair of conductive regions," or "pair of regions." The capacitance value can be, for example, 0.05 fF or more and 10 pF or less. It may also be, for example, 1 pF or more and 10 μF or less.

[0025] In this specification, a transistor has three terminals called a gate, a source, and a drain. The gate is a control terminal that controls the conduction state of the transistor. The two terminals that function as a source or a drain are input / output terminals of the transistor. One of the two input / output terminals serves as a source and the other as a drain depending on the conductivity type (n-channel or p-channel) of the transistor and the level of the potential applied to the three terminals of the transistor. Therefore, in this specification, the terms source and drain are interchangeable. In addition, in this specification, when describing the connection relationship of a transistor, the terms "one of the source or drain" (or first electrode or first terminal) and "the other of the source or drain" (or second electrode or second terminal) are used. Note that, depending on the structure of the transistor, a backgate may be included in addition to the three terminals described above. In this case, in this specification, one of the gate or backgate of the transistor may be referred to as a first gate, and the other of the gate or backgate of the transistor may be referred to as a second gate. Furthermore, for the same transistor, the terms "gate" and "backgate" may be interchangeable. Furthermore, when a transistor has three or more gates, the gates may be referred to as a first gate, a second gate, a third gate, and so on in this specification and the like.

[0026] Furthermore, in this specification and the like, a node can be referred to as a terminal, a wiring, an electrode, a conductive layer, a conductor, an impurity region, etc. depending on the circuit configuration, device structure, etc. Furthermore, a terminal, a wiring, etc. can be referred to as a node.

[0027] Furthermore, in this specification and the like, the terms "voltage" and "potential" can be interchanged as appropriate. "Voltage" refers to the potential difference from a reference potential. For example, if the reference potential is the ground potential (earth potential), then "voltage" can be interchanged with "potential." Note that ground potential does not necessarily mean 0 V. Furthermore, potential is relative, and as the reference potential changes, the potential applied to wiring, the potential applied to a circuit, etc., the potential output from a circuit, etc. also changes.

[0028] "Current" refers to the phenomenon of charge transfer (electrical conduction). For example, a statement that "electrical conduction of a positively charged body is occurring" can be rephrased as "electrical conduction of a negatively charged body is occurring in the opposite direction." Therefore, in this specification, unless otherwise specified, "current" refers to the phenomenon of charge transfer (electrical conduction) associated with the movement of carriers. The carriers referred to here include electrons, holes, anions, cations, complex ions, etc., and the carriers differ depending on the system through which the current flows (e.g., semiconductor, metal, electrolyte, vacuum, etc.). Furthermore, the "direction of current" in wiring, etc., refers to the direction in which positive carriers move and is expressed as a positive current amount. In other words, the direction in which negative carriers move is opposite to the direction of current and is expressed as a negative current amount. Therefore, in this specification, etc., unless otherwise specified regarding the positive / negative sign of the current (or the direction of current), a statement such as "current flows from element A to element B" can be rephrased as "current flows from element B to element A," etc. Furthermore, statements such as "current is input to element A" can be rephrased as "current is output from element A" or the like.

[0029] Furthermore, in this specification, the ordinal numbers "first," "second," and "third" are used to avoid confusion between components. Therefore, they do not limit the number of components. Furthermore, they do not limit the order of the components. For example, a component referred to as "first" in one embodiment of this specification may be a component referred to as "second" in another embodiment or in the claims. Furthermore, for example, a component referred to as "first" in one embodiment of this specification may be omitted in another embodiment or in the claims.

[0030] Furthermore, in this specification, terms indicating position, such as "above" and "below," may be used for convenience in describing the positional relationship between components with reference to the drawings. Furthermore, the positional relationship between components changes as appropriate depending on the direction in which each component is depicted. Therefore, the terms are not limited to those used in the specification, and can be rephrased appropriately depending on the situation. For example, the expression "insulator located on the upper surface of a conductor" can be rephrased as "insulator located on the lower surface of a conductor" by rotating the orientation of the drawing 180 degrees.

[0031] Furthermore, the terms "above" and "below" do not limit the positional relationship of components to being directly above or below and in direct contact with each other. For example, the expression "electrode B on insulating layer A" does not require that electrode B be formed on insulating layer A in direct contact with it, and does not exclude the inclusion of other components between insulating layer A and electrode B.

[0032] Furthermore, in this specification and the like, terms such as "film" and "layer" can be interchanged depending on the situation. For example, the term "conductive layer" may be interchanged with the term "conductive film." Or, for example, the term "insulating film" may be interchanged with the term "insulating layer." Or, in some cases or depending on the situation, terms such as "film" and "layer" may not be used and may be interchanged with other terms. For example, the terms "conductive layer" or "conductive film" may be interchanged with the term "conductor." Or, for example, the terms "insulating layer" and "insulating film" may be interchanged with the term "insulator."

[0033] Furthermore, the terms "electrode" and "wiring" used in this specification and elsewhere do not limit the functionality of these components. For example, an "electrode" may be used as part of a "wiring," and vice versa. Furthermore, the terms "electrode" and "wiring" also include cases where multiple "electrodes" or "wirings" are integrally formed.

[0034] Furthermore, in this specification and the like, terms such as "wiring," "signal line," and "power supply line" may be interchangeable depending on the circumstances. For example, the term "wiring" may be changed to the term "signal line." For example, the term "wiring" may be changed to the term "power supply line." Vice versa, terms such as "signal line" and "power supply line" may be changed to the term "wiring." A term such as "power supply line" may be changed to the term "signal line." Vice versa, terms such as "signal line" may be changed to the term "power supply line." Furthermore, the term "potential" applied to a wiring may be changed to the term "signal" depending on the circumstances. Vice versa, terms such as "signal" may be changed to the term "potential."

[0035] In this specification and the like, a switch refers to a device that has the function of being in a conductive state (on state) or a non-conductive state (off state) and controlling whether or not a current flows. Alternatively, a switch refers to a device that has the function of selecting and switching a path through which a current flows. As an example, an electrical switch, a mechanical switch, or the like can be used. In other words, the switch is not limited to a specific one as long as it can control a current.

[0036] Examples of electrical switches include transistors (e.g., bipolar transistors, MOS transistors, etc.), diodes (e.g., PN diodes, PIN diodes, Schottky diodes, MIM (Metal Insulator Metal) diodes, MIS (Metal Insulator Semiconductor) diodes, diode-connected transistors, etc.), and logic circuits combining these. When a transistor is used as a switch, the "conductive state" of the transistor refers to a state in which the source electrode and drain electrode of the transistor can be considered to be electrically short-circuited. The "non-conductive state" of the transistor refers to a state in which the source electrode and drain electrode of the transistor can be considered to be electrically disconnected. When a transistor is operated simply as a switch, the polarity (conductivity type) of the transistor is not particularly limited.

[0037] An example of a mechanical switch is a switch that uses MEMS (microelectromechanical systems) technology. This switch has a mechanically movable electrode, and the movement of the electrode controls whether the switch is conductive or non-conductive.

[0038] In this specification and the like, the impurities in a semiconductor refer to, for example, components other than the main components constituting the semiconductor layer. For example, elements with a concentration of less than 0.1 atomic % are impurities. When impurities are included, for example, DOS (Density of States) may be formed in the semiconductor, the carrier mobility may decrease, or the crystallinity may decrease. When the semiconductor is an oxide semiconductor, examples of the impurities that change the characteristics of the semiconductor include Group 1 elements, Group 2 elements, Group 13 elements, Group 14 elements, Group 15 elements, transition metals other than the main components, etc. In particular, for example, hydrogen (also contained in water), lithium, sodium, silicon, boron, phosphorus, carbon, nitrogen, etc. are included. Specifically, when the semiconductor is a silicon layer, examples of the impurities that change the characteristics of the semiconductor include, for example, Group 1 elements, Group 2 elements, Group 13 elements, Group 15 elements excluding oxygen and hydrogen.

[0039] Also, regarding this specification and the like, the composition of In:Ga:Zn = 4:2:3 or in the vicinity thereof means that when In is 4 with respect to the total number of atoms, Ga is 1 or more and 3 or less (1 ≤ Ga ≤ 3), and Zn is 2 or more and 4.1 or less (2 ≤ Zn ≤ 4.1). Also, the composition of In:Ga:Zn = 5:1:6 or in the vicinity thereof means that when In is 5 with respect to the total number of atoms, Ga is greater than 0.1 and 2 or less (0.1 < Ga ≤ 2), and Zn is 5 or more and 7 or less (5 ≤ Zn ≤ 7). Also, the composition of In:Ga:Zn = 1:1:1 or in the vicinity thereof means that when In is 1 with respect to the total number of atoms, Ga is greater than 0.1 and 2 or less (0.1 < Ga ≤ 2), and Zn is greater than 0.1 and 2 or less (0.1 < Zn ≤ 2). Also, the composition of In:Ga:Zn = 5:1:3 or in the vicinity thereof means that when In is 5 with respect to the total number of atoms, Ga is 0.5 or more and 1.5 or less (0.5 ≤ Ga ≤ 1.5), and Zn is 2 or more and 4.1 or less (2 ≤ Zn ≤ 4.1). Also, the composition of In:Ga:Zn = 10:1:3 or in the vicinity thereof means that when In is 10 with respect to the total number of atoms, Ga is 0.5 or more and 1.5 or less (0. [Effects of the Invention]

[0040] According to one embodiment of the present invention, a semiconductor device or the like capable of measuring minute current can be provided. Further, according to one embodiment of the present invention, a novel semiconductor device or the like can be provided. Further, according to one embodiment of the present invention, a novel electronic device or the like including the semiconductor device can be provided.

[0041] The effects of one embodiment of the present invention are not limited to the effects listed above. The effects listed above do not preclude the existence of other effects. The other effects are described below and are not mentioned in this section. Effects not mentioned in this section can be derived by a person skilled in the art from the description in the specification or drawings, and can be extracted as appropriate from these descriptions. One embodiment of the present invention has at least one of the effects listed above and other effects. Therefore, one embodiment of the present invention may not have the effects listed above in some cases. [Brief explanation of the drawings]

[0042] [Figure 1] 1A, 1B, and 1C are circuit diagrams showing an example of a semiconductor device. [Figure 2] FIG. 2 is a diagram illustrating the current-voltage characteristics of a transistor. [Figure 3] 3A, 3B, 3C, 3D, 3E, and 3F are circuit diagrams showing examples of semiconductor devices. [Figure 4] FIG. 4 is a cross-sectional view illustrating the configuration of the semiconductor device. [Figure 5] FIG. 5 is a cross-sectional view illustrating the configuration of the semiconductor device. [Figure 6] 6A, 6B, and 6C are cross-sectional views illustrating the configuration of the semiconductor device. [Figure 7] 7A is a top view showing an example of the structure of a capacitive element, FIG. 7B is a cross-sectional perspective view showing the example of the structure of a capacitive element, and FIG. 7C is a cross-sectional perspective view showing the example of the structure of a capacitive element. [Figure 8]FIG. 8A is a top view showing an example of the structure of a capacitive element, FIG. 8B is a cross-sectional view showing the example of the structure of a capacitive element, and FIG. 8C is a cross-sectional perspective view showing the example of the structure of a capacitive element. [Figure 9] FIG. 9A is a table showing the classification of the crystal structure of oxide semiconductors, FIG. 9B is the XRD spectrum of silica glass, and FIG. 9C is the XRD spectrum of crystalline IGZO. [Figure 10] FIG. 10A is a perspective view showing an example of a semiconductor wafer, FIG. 10B is a perspective view showing an example of a cut semiconductor wafer, and FIGS. 10C and 10D are perspective views showing an example of an electronic component. [Figure 11] FIG. 11 is a block diagram illustrating an example of the configuration of an electronic device. [Figure 12] 12A, 12B, 12C, 12D, and 12E are perspective views illustrating an example of a product. [Figure 13] 13A and 13B are perspective views illustrating an example of a product. [Figure 14] 14A and 14B are diagrams for explaining the conditions for circuit calculation. [Figure 15] FIG. 15 is a diagram illustrating the voltage-current characteristics of a diode-connected transistor. [Figure 16] FIG. 16 is a diagram for explaining the results of the circuit calculation. [Figure 17] FIG. 17 is a diagram for explaining the results of the circuit calculation. [Figure 18] FIG. 18 is a diagram for explaining the results of the circuit calculation. [Figure 19] FIG. 19 is a diagram showing the measurement circuit. [Figure 20] FIG. 20 is a diagram showing the temperature dependence of the off-current. [Figure 21] FIG. 21 is a graph showing the temperature dependence of the Hall mobility and carrier density of the CAAC-IGZO film. [Figure 22] FIG. 22 is a diagram showing the temperature dependence of the cutoff frequency. [Figure 23] FIG. 23 is a distribution diagram showing variations in threshold voltages of a plurality of FETs. [Figure 24]24A and 24B are diagrams showing the results of the accelerated test. [Figure 25] 25A and 25B are diagrams showing the results of the accelerated test. DETAILED DESCRIPTION OF THE INVENTION

[0043] In this specification and the like, the term "metal oxide" refers to an oxide of a metal in a broad sense. Metal oxides are classified into oxide insulators, oxide conductors (including transparent oxide conductors), oxide semiconductors (also referred to as "oxide semiconductors" or simply "OSs"). For example, when a metal oxide is used in the active layer of a transistor, the metal oxide may be referred to as an oxide semiconductor. That is, when a metal oxide can form a channel formation region of a transistor having at least one of an amplifying function, a rectifying function, and a switching function, the metal oxide can be referred to as a metal oxide semiconductor. Furthermore, when a metal oxide is referred to as an OS FET or an OS transistor, it can be rephrased as a transistor having a metal oxide or an oxide semiconductor.

[0044] In this specification and the like, nitrogen-containing metal oxides may also be collectively referred to as metal oxides. Nitrogen-containing metal oxides may also be referred to as metal oxynitrides.

[0045] In this specification and the like, the configurations shown in each embodiment can be combined as appropriate with the configurations shown in other embodiments to form one aspect of the present invention. In addition, when multiple configuration examples are shown in one embodiment, the configuration examples can be combined as appropriate with each other.

[0046] In addition, the content (or even part of the content) described in one embodiment can be applied, combined, or replaced with at least one of another content (or even part of the content) described in that embodiment and another content (or even part of the content) described in one or more other embodiments.

[0047] The contents described in the embodiments refer to the contents described in each embodiment using various figures or the contents described using text in the specification.

[0048] Furthermore, a figure (or even a part thereof) described in one embodiment can be combined with another part of that figure, another figure (or even a part thereof) described in that embodiment, and at least one figure (or even a part thereof) described in one or more other embodiments to form even more figures.

[0049] The embodiments described in this specification will be described with reference to the drawings. However, it will be readily understood by those skilled in the art that the embodiments can be implemented in many different ways, and that various changes in form and details can be made without departing from the spirit and scope of the invention. Therefore, the present invention should not be interpreted as being limited to the description of the embodiments. Note that in the configuration of the invention of the embodiments, the same reference numerals are used in different drawings for the same parts or parts having similar functions, and repeated description thereof may be omitted. Also, in perspective views and the like, the description of some components may be omitted to ensure clarity of the drawings.

[0050] In this specification, when the same symbol is used for multiple elements, and particularly when it is necessary to distinguish between them, an identification symbol such as “_1”, “[n]”, or “[m,n]” may be added to the symbol.

[0051] In addition, in the drawings of this specification, the size, layer thickness, or region may be exaggerated for clarity. Therefore, the drawings are not necessarily limited to the scale. Note that the drawings are schematic illustrations of ideal examples, and are not limited to the shapes or values ​​shown in the drawings. For example, variations in signals, voltages, or currents due to noise, or variations in signals, voltages, or currents due to timing differences may be included.

[0052] (Embodiment 1) In this embodiment, a circuit capable of measuring a minute current, which is a semiconductor device of one embodiment of the present invention, will be described.

[0053] 1A illustrates a circuit 20 capable of measuring current, which is a semiconductor device according to one embodiment of the present invention. The circuit 20 includes a transistor M1 and an operational amplifier OP1. The circuit 20 also includes an input terminal IT and an output terminal OT.

[0054] The transistor M1 is an OS transistor having a metal oxide in a channel formation region. The metal oxide can be, for example, one or more materials selected from indium, element M (the element M is one or more materials selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium), and zinc. In particular, metal oxides containing indium, gallium, and zinc are intrinsic (also called I-type) or substantially intrinsic semiconductors with a wide band gap, and the carrier concentration of the metal oxide is 1×10 18 cm -3 Preferably, it is 1×10 or less. 17 cm -3 More preferably, it is less than 1×10 16 cm -3 More preferably, it is less than 1×10 13 cm -3 More preferably, it is less than 1×10 12 cm-3 The off-state current of an OS transistor including the metal oxide in a channel formation region is preferably less than 10 aA (1×10 -17 A) or less, preferably 1 aA (1 × 10 -18 A) or less, and more preferably 10 zA (1 × 10 -20 A) or less, more preferably 1 zA (1 × 10 -21 A) or less, more preferably 100 yA (1 × 10 -22 A) or less. Furthermore, since the carrier concentration of the metal oxide in the OS transistor is low, the off-state current of the OS transistor remains low even when the temperature of the OS transistor changes. For example, even when the temperature of the OS transistor is 150° C., the off-state current can be 100 zA per 1 μm of channel width.

[0055] In this specification, the off-state current of an n-channel transistor can refer to a leakage current that flows between the source and drain when a gate-source voltage applied to the transistor is lower than the threshold voltage of the transistor, or a leakage current that flows when the transistor is in an off state.

[0056] As shown in FIG. 1A, the transistor M1 may have a back gate. Although FIG. 1A does not specifically illustrate where the back gate of the transistor M1 is electrically connected, the electrical connection of the back gate of the transistor M1 may be freely determined during the design phase of the circuit 20. For example, by electrically connecting the gate and back gate of the transistor M1, the current flowing when the transistor M1 is in an on state can be increased. Furthermore, for example, by providing a wiring for electrically connecting the back gate of the transistor M1 to an external circuit, the threshold voltage of the transistor M1 can be varied by applying a potential to the back gate of the transistor M1 from the external circuit. The transistor M1 may not have a back gate.

[0057] The operational amplifier OP1 is preferably a circuit formed by a CMOS (complementary metal-oxide semiconductor) process. Furthermore, the CMOS process can use transistors whose channel formation region is made of single-crystal silicon, polycrystalline silicon, or microcrystalline silicon (hereinafter referred to as Si transistors). In particular, Si transistors have high field-effect mobility and high reliability, so it is preferable to use Si transistors in the circuit configuration of the operational amplifier OP1.

[0058] The operational amplifier OP1 may also be a unipolar circuit using OS transistors. Regarding the metal oxide contained in the channel formation region of an OS transistor, it is possible to fabricate an n-type semiconductor using a metal oxide containing indium (e.g., In oxide) or a metal oxide containing zinc (e.g., Zn oxide). However, it is difficult to fabricate a p-type semiconductor using such a metal oxide in terms of mobility and reliability. Therefore, when configuring the operational amplifier OP1 using OS transistors, it is sufficient to design it as a unipolar circuit. In this case, when manufacturing the circuit 20, the operational amplifier OP1 can be manufactured simultaneously with the transistor M1, thereby shortening the manufacturing time of the circuit 20.

[0059] Furthermore, operational amplifier OP1 may have a circuit configuration in which OS transistors are used as n-channel transistors and Si transistors are used as p-channel transistors.

[0060] In this specification and the like, the term "operational amplifier" can be replaced with "differential amplifier circuit."

[0061] The input terminal IT is electrically connected to the inverting input terminal of the operational amplifier OP1, the first terminal of the transistor M1, and the gate of the transistor M1, the output terminal OT is electrically connected to the output terminal of the operational amplifier OP1 and the second terminal of the transistor M1, and the non-inverting input terminal of the operational amplifier OP1 is electrically connected to the wiring GNDL.

[0062] The wiring GNDL has a function of applying a constant voltage. The constant voltage can be, for example, a ground potential (sometimes referred to as GND). The constant voltage applied by the wiring GNDL may also be a voltage other than the ground potential. In this description, the constant voltage applied by the wiring GNDL is the ground potential.

[0063] As shown in Figure 1A, transistor M1 is configured as a diode, so circuit 20 in Figure 1A can be considered as an equivalent circuit of circuit 10 shown in Figure 1B.

[0064] The circuit 10 is a circuit in which the transistor M1 of the circuit 20 is replaced with a diode element DE, and the input terminal of the diode element DE is electrically connected to the input terminal IT and the inverting input terminal of the operational amplifier OP1, and the output terminal of the diode element DE is electrically connected to the output terminal OT and the output terminal of the operational amplifier OP1.

[0065] As shown in Figure 1B, the circuit 10 is configured as a logarithmic conversion circuit. When the diode element DE is an ideal pn junction and a large forward voltage is applied, an input current I in The output voltage V when outcan be expressed as the following equation:

[0066]

number

[0067] where k is the Boltzmann constant, T is the absolute temperature, q is the unit charge, and I0 is the amount of saturated current.

[0068] As shown in the above equation, by using the circuit 10, the output voltage V out is the input current I in In other words, by using the voltage range of the forward current-voltage characteristics of the diode, the input current I in can be measured.

[0069] The lower limit of the measurable current value is determined by the current-voltage characteristics of the diode element DE. For example, if a pn junction diode, a bipolar transistor, or the like is used as the diode element DE of the circuit 10, the range of current that can be measured by the circuit 10 is approximately 1.0 pA (1.0×10 -12 A) or more and 10 mA or less. Therefore, it is not desirable to measure currents lower than 1.0 fA using circuit 10 in this case. Furthermore, if a pn junction diode, bipolar transistor, or the like is used as the diode element DE in circuit 10, the current-voltage characteristics of the diode also depend on temperature as shown in the above equation, so current measurement may be affected by the environmental temperature.

[0070] Now consider diode-connected transistor M1 as diode element DE as in circuit 20 of FIG. 1A.

[0071] First, we will explain the advantages of using an OS transistor as the transistor M1. Figure 2 is a schematic diagram showing an example of the drain current Id and gate-source voltage Vgs characteristics of an OS transistor and a Si transistor, where the OS transistor shows characteristic IVC1a and the Si transistor shows characteristic IVC2. Note that the drain current Id is displayed logarithmically, and the gate-source voltage Vgs is displayed linearly. As shown in Figure 2, the off-current of the OS transistor is smaller than that of the Si transistor.

[0072] Specifically, the off-state current of the OS transistor is 10 aA (1.0 × 10) per 1 μm of channel width. -17 A) or less, more preferably 100 yA (1.0 × 10 -22 Therefore, by using an OS transistor as the transistor M1, the off-state current can flow from the input terminal IT to the output terminal OT of the circuit 20, and an output voltage V out can be output.

[0073] In other words, the off-state current flowing through transistor M1 in circuit 20 of FIG. 1A can be made smaller than the current flowing in the forward direction of diode element DE (pn junction diode, bipolar transistor, etc.) in circuit 10 of FIG. 1B. Therefore, by using circuit 20 of FIG. 1A, it is possible to measure a current with a lower measurement limit than that of circuit 10 of FIG. 1B.

[0074] Furthermore, when the transistor M1 is a transistor having a back gate, by applying a desired potential to the back gate and varying the threshold voltage of the transistor M1, it is possible to shift the characteristic IVC1a to the characteristic IVC1b as shown in FIG. 2, and to change the drain current Id when the gate-source voltage Vgs of the transistor M1 is 0V. In other words, by varying the threshold voltage of the transistor M1 while keeping the transistor M1 in the off state, it is possible to change the off-current. For example, by varying the threshold voltage of the transistor M1, it is possible to reduce the off-current to 1.0 fA (1.0×10) per 1 μm of channel width. -15 A) or less, preferably 1.0 pA (1.0 × 10) per 1 μm of channel width -12 A) or less, more preferably 1.0 nA (1.0 × 10) per 1 μm of channel width. -9 A) or less, more preferably 1.0 μA (1.0 × 10) per 1 μm of channel width. -6 A) It can be done as follows:

[0075] Furthermore, since the off-state current of an OS transistor changes less with temperature than that of a Si transistor, the circuit 20 including the transistor M1 can measure the current more stably with respect to temperature than the circuit 10 including a diode element DE (such as a pn junction diode or a bipolar transistor).

[0076] Note that the semiconductor device of one embodiment of the present invention is not limited to the circuit 20 shown in FIG. 1A and the circuit configuration can be changed depending on the situation. For example, as shown in FIG. 1C, the electrical connection of the gate of the transistor M1 in the circuit 20 of FIG. 1A may be changed. In the circuit 20A shown in FIG. 1C, the gate of the transistor M1 is electrically connected to the second terminal of the transistor M1, not the first terminal. In this case, the transistor M1 functions as a diode element whose forward direction is the direction in which current flows from the second terminal to the first terminal.

[0077] Note that this embodiment mode can be appropriately combined with other embodiment modes described in this specification.

[0078] (Embodiment 2) In this embodiment, a circuit capable of measuring minute currents, which is different from that shown in FIG. 1A described in the previous embodiment, will be described.

[0079] The circuit 21 shown in FIG. 3A is a circuit in which the transistor M1 of the circuit 20 in FIG. 1A is replaced with a circuit OSC, and a first terminal of the circuit OSC is electrically connected to the input terminal IT and the inverting input terminal of the operational amplifier OP1, and a second terminal of the circuit OSC is electrically connected to the output terminal OT and the output terminal of the operational amplifier OP1.

[0080] The circuit OSC is a circuit having an OS transistor, and the current flowing between the first terminal and the second terminal of the circuit OSC is set to 1.0 μA (1.0×10 -6 A) or less, preferably 1.0 pA (1.0 × 10 -12 A) or less, preferably 1.0 aA (1.0 × 10 -18 A) or less, preferably 1.0 zA (1.0 × 10 -21 A), more preferably 100 yA (1.0 × 10 -22 A) can be used.

[0081] A specific configuration of the circuit OSC can be, for example, the circuit OSC shown in Fig. 3B. Fig. 3B shows a circuit 21A, which is an example of the circuit 21, and the circuit OSC included in the circuit 21A includes transistors M1[1] to M1[m] (m is an integer of 2 or more).

[0082] 3B, the transistors M1[1] to M1[m] are each configured as a diode, and the transistors M1[1] to M1[m] are electrically connected in series. One end of the series-connected transistors M1[1] to M1[m] is electrically connected to a first terminal of the circuit OSC, and the other end of the series-connected transistors M1[1] to M1[m] is electrically connected to a second terminal of the circuit OSC.

[0083] All of the transistors M1[1] to M1[m] may be OS transistors. Alternatively, at least one of the transistors M1[1] to M1[m] may be an OS transistor, and the rest may be transistors other than OS transistors (for example, a transistor with an active layer made of a semiconductor such as Si or Ge, a transistor with an active layer made of a compound semiconductor such as ZnSe, CdS, GaAs, InP, GaN, or SiGe, a transistor with an active layer made of a carbon nanotube, or a transistor with an active layer made of an organic semiconductor).

[0084] Furthermore, the gates of the transistors M1[1] to M1[m] included in the circuit OSC of the circuit 21A can be configured to be electrically connected to each other as shown in Fig. 3C. Specifically, in the circuit OSC of the circuit 21B shown in Fig. 3C, the gates of the transistors M1[1] to M1[m] are electrically connected to the first terminal of the transistor M1[1]. In the circuit OSC, by electrically connecting the transistors M1[1] to M1[m] as shown in Fig. 3C, a diode element can be configured using a transistor with a substantially long channel length.

[0085] Furthermore, a circuit CE may be provided in the circuit OSC of the circuit 21A. In the circuit 21C shown in FIG. 3D, the circuit OSC is configured such that the circuit CE is electrically connected to the transistors M1[1] to M1[m] electrically connected in series. The circuit CE may be, for example, a circuit element, specifically, a resistor, a diode, or a capacitor. The circuit CE may be, for example, a circuit in which circuit elements are connected in parallel. While FIG. 3D illustrates the circuit CE being provided between the transistor M1[m] and the second terminal of the circuit OSC, the circuit CE may also be provided between the transistor M1[1] and the first terminal of the circuit OSC, or between any of the transistors M1[1] to M1[m] electrically connected in series.

[0086] 3A, which is different from the circuits OSC in FIG. 3B to FIG. 3D, may have a specific configuration such as the circuit OSC shown in FIG. 3E. FIG. 3D shows a circuit 21D, which is an example of the circuit 21. The circuit OSC included in the circuit 21D includes transistors M1[1] to M1[m] (m is an integer of 2 or greater), similar to the circuit 21A.

[0087] 3E, the transistors M1[1] to M1[m] are each configured as a diode and electrically connected in parallel, that is, the first terminal and gate of each of the transistors M1[1] to M1[m] are electrically connected to the first terminal of the circuit OSC, and the second terminal of each of the transistors M1[1] to M1[m] is electrically connected to the second terminal of the circuit OSC.

[0088] Furthermore, the circuit OSC of the circuit 21D may be provided with a capacitor C1. In the circuit 21E shown in FIG. 3F, the circuit OSC has a configuration in which a capacitor C1 is electrically connected in parallel to the transistors M1[1] to M1[m] electrically connected in parallel. Specifically, the first terminal of the capacitor C1 is electrically connected to the first terminals and gates of the transistors M1[1] to M1[m] and the inverting input terminal of the operational amplifier OP1, and the second terminal of the capacitor C1 is electrically connected to the second terminals of the transistors M1[1] to M1[m] and the output terminal of the operational amplifier OP1. The capacitor C1 in the circuit 21E can maintain the potential between the inverting input terminal and the output terminal of the operational amplifier OP1, thereby enabling a stable current to flow between the first terminal and the second terminal of each of the diode-connected transistors M1[1] to M1[m]. In addition, in the circuit 21E of Figure 3F, transistors M1[1] to M1[m] are illustrated as multiple transistors, but the circuit 21E may be configured with a single transistor M1 instead of transistors M1[1] to M1[m].

[0089] Note that it is preferable that all of the transistors M1[1] to M1[m] be OS transistors.

[0090] Similarly to the circuit 20 described in the first embodiment, minute current amounts can be measured using the circuits 21, 21A, 21B, 21C, 21D, and 21E shown in FIGS. 3A to 3F.

[0091] Note that this embodiment mode can be appropriately combined with other embodiment modes and examples described in this specification.

[0092] (Embodiment 3) This embodiment mode will describe a transistor structure applicable to the semiconductor device structure described in the above embodiment mode, specifically, a structure in which transistors having different electrical characteristics are stacked. This structure can increase the degree of freedom in designing a semiconductor device. Furthermore, stacking transistors having different electrical characteristics can increase the degree of integration of a semiconductor device.

[0093] 4 includes a transistor 300, a transistor 500, and a capacitor 600. Fig. 6A is a cross-sectional view of the transistor 500 in the channel length direction, Fig. 6B is a cross-sectional view of the transistor 500 in the channel width direction, and Fig. 6C is a cross-sectional view of the transistor 300 in the channel width direction.

[0094] The transistor 500 is a transistor (OS transistor) having a metal oxide in a channel formation region. Because the off-state current of the transistor 500 is small, when the transistor 500 is used as a write transistor in a memory cell, the written data voltage or charge can be held for a long period of time. In other words, the refresh operation is performed less frequently or is not required, thereby reducing the power consumption of the semiconductor device.

[0095] In the semiconductor device described in this embodiment, the transistor 500 is provided above the transistor 300 , and the capacitor 600 is provided above the transistors 300 and 500 .

[0096] The transistor 300 is provided over a substrate 311 and includes a conductor 316, an insulator 315, a semiconductor region 313 formed of part of the substrate 311, and low-resistance regions 314a and 314b functioning as source and drain regions. Note that the transistor 300 can be applied to, for example, the transistor included in the operational amplifier OP1 in the above embodiment.

[0097] 6C , the transistor 300 has an upper surface and a side surface in the channel width direction of a semiconductor region 313 covered with a conductor 316 via an insulator 315. By forming the transistor 300 as a fin type in this way, the effective channel width is increased, thereby improving the on-state characteristics of the transistor 300. Furthermore, the contribution of the electric field of the gate electrode can be increased, thereby improving the off-state characteristics of the transistor 300.

[0098] The transistor 300 may be either a p-channel type or an n-channel type.

[0099] The region where the channel of the semiconductor region 313 is formed, the region nearby, the low-resistance region 314a that serves as the source region or the drain region, and the low-resistance region 314b preferably contain a semiconductor such as a silicon-based semiconductor, and preferably contain single-crystal silicon. Alternatively, they may be formed of a material containing Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), or the like. A configuration using silicon in which the effective mass is controlled by applying stress to the crystal lattice and changing the lattice spacing may also be used. Alternatively, the transistor 300 may be a high electron mobility transistor (HEMT) by using GaAs and GaAlAs, or the like.

[0100] The low resistance region 314a and the low resistance region 314b contain, in addition to the semiconductor material applied to the semiconductor region 313, an element that imparts n-type conductivity, such as arsenic or phosphorus, or an element that imparts p-type conductivity, such as boron.

[0101] The conductor 316 functioning as the gate electrode can be made of a conductive material such as a semiconductor material, metal material, alloy material, or metal oxide material, such as silicon containing an element that imparts n-type conductivity, such as arsenic or phosphorus, or an element that imparts p-type conductivity, such as boron.

[0102] Since the work function is determined by the material of the conductor, the threshold voltage of the transistor can be adjusted by selecting the material of the conductor. Specifically, it is preferable to use a material such as titanium nitride or tantalum nitride as the conductor. Furthermore, in order to achieve both conductivity and embeddability, it is preferable to use a metal material such as tungsten or aluminum as the conductor in a laminated state, and tungsten is particularly preferable in terms of heat resistance.

[0103] 4 is just an example, and the structure is not limited thereto. An appropriate transistor may be used depending on the circuit configuration and driving method. For example, when the semiconductor device is a unipolar circuit including only OS transistors (meaning transistors with the same polarity, such as only n-channel transistors), the structure of the transistor 300 may be the same as that of the transistor 500 including an oxide semiconductor, as shown in FIG. The details of the transistor 500 will be described later.

[0104] An insulator 320, an insulator 322, an insulator 324, and an insulator 326 are stacked in this order to cover the transistor 300.

[0105] The insulators 320, 322, 324, and 326 can be formed using, for example, silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, aluminum oxide, aluminum oxynitride, aluminum nitride oxide, aluminum nitride, or the like.

[0106] In this specification, silicon oxynitride refers to a material whose composition contains more oxygen than nitrogen, silicon nitride oxide refers to a material whose composition contains more nitrogen than oxygen, aluminum oxynitride refers to a material whose composition contains more oxygen than nitrogen, and aluminum nitride oxide refers to a material whose composition contains more nitrogen than oxygen.

[0107] The insulator 322 may function as a planarization film to reduce steps caused by the transistor 300 or the like provided thereunder. For example, the top surface of the insulator 322 may be planarized by planarization treatment using a chemical mechanical polishing (CMP) method or the like to improve the planarity.

[0108] The insulator 324 is preferably a film having a barrier property that prevents hydrogen or impurities from diffusing from the substrate 311, the transistor 300, or the like to a region where the transistor 500 is provided.

[0109] An example of a film having a barrier property against hydrogen is silicon nitride formed by a CVD method. Here, hydrogen diffusion into a semiconductor element having an oxide semiconductor, such as the transistor 500, may degrade the characteristics of the semiconductor element. Therefore, it is preferable to use a film that suppresses hydrogen diffusion between the transistor 500 and the transistor 300. Specifically, the film that suppresses hydrogen diffusion is a film that releases a small amount of hydrogen.

[0110] The amount of desorption of hydrogen can be analyzed using, for example, thermal desorption spectroscopy (TDS). For example, the amount of desorption of hydrogen from the insulator 324 is calculated as 10×10 per area of ​​the insulator 324 when the surface temperature of the film is in the range of 50° C. to 500° C. in TDS analysis. 15 atoms / cm 2 Less than or equal to 5 x 10 15 atoms / cm 2 The following is fine.

[0111] It is preferable that the insulator 326 has a lower dielectric constant than the insulator 324. For example, the relative dielectric constant of the insulator 326 is preferably less than 4, and more preferably less than 3. Furthermore, for example, the relative dielectric constant of the insulator 326 is preferably 0.7 times or less, and more preferably 0.6 times or less, the relative dielectric constant of the insulator 324. By using a material with a low dielectric constant as the interlayer film, the parasitic capacitance that occurs between wirings can be reduced.

[0112] Conductors 328 and 330, which connect to the capacitor 600 or the transistor 500, are embedded in the insulators 320, 322, 324, and 326. The conductors 328 and 330 function as plugs or wirings. A plurality of conductors that function as plugs or wirings may be collectively denoted by the same reference numeral. In this specification and the like, a wiring and a plug connected to the wiring may be integral. That is, a part of a conductor may function as a wiring, and a part of a conductor may function as a plug.

[0113] The materials for each plug and wiring (conductor 328, conductor 330, etc.) can be a conductive material such as a metal material, an alloy material, a metal nitride material, or a metal oxide material, and can be used in a single layer or a laminated layer. It is preferable to use a high-melting-point material such as tungsten or molybdenum, which has both heat resistance and conductivity, and tungsten is particularly preferable. Alternatively, it is preferable to form the plug and wiring from a low-resistance conductive material such as aluminum or copper. Using a low-resistance conductive material can reduce the wiring resistance.

[0114] A wiring layer may be provided over the insulator 326 and the conductor 330. For example, in FIG. 4, the insulator 350, the insulator 352, and the insulator 354 are stacked in this order. The conductor 356 is formed over the insulator 350, the insulator 352, and the insulator 354. The conductor 356 functions as a plug or wiring connected to the transistor 300. Note that the conductor 356 can be formed using a material similar to that of the conductor 328 and the conductor 330.

[0115] Note that, for example, the insulator 350 preferably uses an insulator having a barrier property against hydrogen, similar to the insulator 324. The conductor 356 preferably includes a conductor having a barrier property against hydrogen. In particular, a conductor having a barrier property against hydrogen is formed in an opening of the insulator 350 having a barrier property against hydrogen. With this structure, the transistor 300 and the transistor 500 can be separated by a barrier layer, and diffusion of hydrogen from the transistor 300 to the transistor 500 can be suppressed.

[0116] Note that, for example, tantalum nitride or the like is preferably used as the conductor having a barrier property against hydrogen. Stacking tantalum nitride and highly conductive tungsten can suppress diffusion of hydrogen from the transistor 300 while maintaining the conductivity of the wiring. In this case, a structure in which the tantalum nitride layer having a barrier property against hydrogen is in contact with the insulator 350 having a barrier property against hydrogen is preferable.

[0117] A wiring layer may be provided over the insulator 354 and the conductor 356. For example, in FIG. 4, an insulator 360, an insulator 362, and an insulator 364 are stacked in this order. A conductor 366 is formed in the insulator 360, the insulator 362, and the insulator 364. The conductor 366 functions as a plug or a wiring. The conductor 366 can be formed using a material similar to that of the conductors 328 and 330.

[0118] Note that, for example, the insulator 360 preferably uses an insulator having a barrier property against hydrogen, similar to the insulator 324. The conductor 366 preferably includes a conductor having a barrier property against hydrogen. In particular, a conductor having a barrier property against hydrogen is preferably formed in an opening of the insulator 360 having a barrier property against hydrogen. With this structure, the transistor 300 and the transistor 500 can be separated by a barrier layer, and diffusion of hydrogen from the transistor 300 to the transistor 500 can be suppressed.

[0119] A wiring layer may be provided over the insulator 364 and the conductor 366. For example, in FIG. 4, an insulator 370, an insulator 372, and an insulator 374 are stacked in this order. A conductor 376 is formed in the insulator 370, the insulator 372, and the insulator 374. The conductor 376 functions as a plug or a wiring. The conductor 376 can be formed using a material similar to that of the conductors 328 and 330.

[0120] Note that, for example, the insulator 370 preferably uses an insulator having a barrier property against hydrogen, similar to the insulator 324. The conductor 376 preferably includes a conductor having a barrier property against hydrogen. In particular, a conductor having a barrier property against hydrogen is preferably formed in an opening of the insulator 370 having a barrier property against hydrogen. With this structure, the transistor 300 and the transistor 500 can be separated by a barrier layer, and diffusion of hydrogen from the transistor 300 to the transistor 500 can be suppressed.

[0121] A wiring layer may be provided over the insulator 374 and the conductor 376. For example, in FIG. 4, an insulator 380, an insulator 382, ​​and an insulator 384 are stacked in this order. A conductor 386 is formed in the insulator 380, the insulator 382, ​​and the insulator 384. The conductor 386 functions as a plug or a wiring. The conductor 386 can be formed using a material similar to that of the conductors 328 and 330.

[0122] Note that, for example, the insulator 380 preferably uses an insulator having a barrier property against hydrogen, similar to the insulator 324. The conductor 386 preferably includes a conductor having a barrier property against hydrogen. In particular, a conductor having a barrier property against hydrogen is preferably formed in an opening of the insulator 380 having a barrier property against hydrogen. With this structure, the transistor 300 and the transistor 500 can be separated by a barrier layer, and diffusion of hydrogen from the transistor 300 to the transistor 500 can be suppressed.

[0123] In the above, a wiring layer including the conductor 356, a wiring layer including the conductor 366, a wiring layer including the conductor 376, and a wiring layer including the conductor 386 have been described, but the semiconductor device according to this embodiment is not limited to this. There may be three or fewer wiring layers similar to the wiring layer including the conductor 356, or there may be five or more wiring layers similar to the wiring layer including the conductor 356.

[0124] An insulator 510, an insulator 512, an insulator 514, and an insulator 516 are stacked in this order over the insulator 384. Any of the insulator 510, the insulator 512, the insulator 514, and the insulator 516 is preferably formed using a substance that has a barrier property against oxygen and hydrogen.

[0125] For example, the insulator 510 and the insulator 514 are preferably formed using a film having a barrier property that prevents hydrogen or impurities from diffusing from the substrate 311 or a region where the transistor 300 is provided to a region where the transistor 500 is provided. Therefore, a material similar to that of the insulator 324 can be used.

[0126] An example of a film having a barrier property against hydrogen is silicon nitride formed by a CVD method. Here, hydrogen diffusion into a semiconductor element having an oxide semiconductor, such as the transistor 500, may degrade the characteristics of the semiconductor element. Therefore, it is preferable to use a film that suppresses hydrogen diffusion between the transistor 500 and the transistor 300. Specifically, the film that suppresses hydrogen diffusion is a film that releases a small amount of hydrogen.

[0127] As a film having a barrier property against hydrogen, for example, the insulators 510 and 514 are preferably made of a metal oxide such as aluminum oxide, hafnium oxide, or tantalum oxide.

[0128] In particular, aluminum oxide has a high blocking effect of preventing the permeation of both oxygen and impurities such as hydrogen and moisture, which can cause fluctuations in the electrical characteristics of a transistor. Therefore, aluminum oxide can prevent impurities such as hydrogen and moisture from entering the transistor 500 during and after the transistor manufacturing process. Furthermore, aluminum oxide can suppress the release of oxygen from the oxide that constitutes the transistor 500. Therefore, aluminum oxide is suitable for use as a protective film for the transistor 500.

[0129] For example, the insulator 512 and the insulator 516 can be formed using a material similar to that of the insulator 320. By using a material with a relatively low dielectric constant for these insulators, parasitic capacitance between wirings can be reduced. For example, the insulators 512 and 516 can be formed using a silicon oxide film, a silicon oxynitride film, or the like.

[0130] A conductor 518, a conductor constituting the transistor 500 (for example, the conductor 503), and the like are embedded in the insulators 510, 512, 514, and 516. The conductor 518 functions as a plug or a wiring connected to the capacitor 600 or the transistor 300. The conductor 518 can be formed using a material similar to that of the conductor 328 and the conductor 330.

[0131] In particular, the conductor 518 in the region in contact with the insulator 510 and the insulator 514 is preferably a conductor that has a barrier property against oxygen, hydrogen, and water. With this structure, the transistor 300 and the transistor 500 can be separated by a layer that has a barrier property against oxygen, hydrogen, and water, and diffusion of hydrogen from the transistor 300 to the transistor 500 can be suppressed.

[0132] Above the insulator 516 is the transistor 500 .

[0133] As shown in Figures 6A and 6B, the transistor 500 includes a conductor 503 arranged so as to be embedded in the insulator 514 and the insulator 516, an insulator 520 arranged on the insulator 516 and the conductor 503, an insulator 522 arranged on the insulator 520, an insulator 524 arranged on the insulator 522, an oxide 530a arranged on the insulator 524, an oxide 530b arranged on the oxide 530a, conductors 542a and 542b arranged apart from each other on the oxide 530b, an insulator 580 arranged on the conductors 542a and 542b and having an opening formed therein overlapping the conductors 542a and 542b, an oxide 530c arranged on the bottom and side surfaces of the opening, an insulator 550 arranged on the surface on which the oxide 530c is formed, and a conductor 560 arranged on the surface on which the insulator 550 is formed.

[0134] 6A and 6B, it is preferable that an insulator 544 be disposed between the oxide 530a, the oxide 530b, the conductor 542a, and the conductor 542b and the insulator 580. It is preferable that the conductor 560 include a conductor 560a disposed inside the insulator 550 and a conductor 560b disposed so as to be embedded inside the conductor 560a. It is preferable that an insulator 574 be disposed on the insulator 580, the conductor 560, and the insulator 550, as shown in FIGS.

[0135] In the following, the oxide 530a, the oxide 530b, and the oxide 530c may be collectively referred to as the oxide 530.

[0136] Although the transistor 500 has a three-layer structure of oxides 530a, 530b, and 530c in and around a channel region, the present invention is not limited to this structure. For example, the transistor may have a single layer of oxide 530b, a two-layer structure of oxides 530b and 530a, a two-layer structure of oxides 530b and 530c, or a stacked structure of four or more layers. Although the transistor 500 has a two-layer structure, the present invention is not limited to this structure. For example, the conductor 560 may have a single-layer structure or a stacked structure of three or more layers. The transistor 500 shown in FIGS. 4 and 6A is merely an example, and the transistor may be of any suitable structure depending on the circuit configuration and driving method.

[0137] Here, the conductor 560 functions as the gate electrode of the transistor, and the conductors 542a and 542b function as the source and drain electrodes, respectively. As described above, the conductor 560 is formed so as to be embedded in the opening of the insulator 580 and in the region sandwiched between the conductors 542a and 542b. The arrangements of the conductors 560, 542a, and 542b are selected in a self-aligned manner with respect to the opening of the insulator 580. That is, in the transistor 500, the gate electrode can be positioned between the source and drain electrodes in a self-aligned manner. Therefore, the conductor 560 can be formed without providing an alignment margin, thereby reducing the area occupied by the transistor 500. This allows for miniaturization and high integration of semiconductor devices.

[0138] Furthermore, since the conductor 560 is formed in a self-aligned manner in the region between the conductor 542a and the conductor 542b, the conductor 560 does not have a region that overlaps with the conductor 542a or the conductor 542b. This reduces the parasitic capacitance formed between the conductor 560 and the conductor 542a and between the conductor 560 and the conductor 542b. This improves the switching speed of the transistor 500 and provides high frequency characteristics.

[0139] The conductor 560 may function as a first gate (also referred to as a top gate) electrode. The conductor 503 may function as a second gate (also referred to as a bottom gate) electrode. In this case, the threshold voltage of the transistor 500 can be controlled by changing the potential applied to the conductor 503 independently of the potential applied to the conductor 560. In particular, applying a negative potential to the conductor 503 can increase the threshold voltage of the transistor 500 above 0 V and reduce the off-state current. Therefore, applying a negative potential to the conductor 503 can reduce the drain current when the potential applied to the conductor 560 is 0 V compared to when a negative potential is not applied.

[0140] The conductor 503 is arranged to overlap the oxide 530 and the conductor 560. In this way, when a potential is applied to the conductor 560 and the conductor 503, the electric field generated from the conductor 560 and the electric field generated from the conductor 503 are connected, and the channel formation region formed in the oxide 530 can be covered. In this specification and the like, a transistor structure in which the channel formation region is electrically surrounded by the electric fields of the first gate electrode and the second gate electrode is called a surrounded channel (S-channel) structure.

[0141] The conductor 503 has a structure similar to that of the conductor 518, in which the conductor 503a is formed in contact with the inner walls of the openings of the insulators 514 and 516, and the conductor 503b is formed further inward. Note that although the transistor 500 has a structure in which the conductors 503a and 503b are stacked, the present invention is not limited to this. For example, the conductor 503 may have a single layer structure or a stacked structure of three or more layers.

[0142] Here, the conductor 503a is preferably made of a conductive material that has the function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, and copper atoms (the impurities are less likely to permeate). Alternatively, it is preferably made of a conductive material that has the function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.) (the oxygen is less likely to permeate). In this specification, the function of suppressing the diffusion of impurities or oxygen refers to the function of suppressing the diffusion of any one or all of the impurities and oxygen.

[0143] For example, the conductor 503a has a function of suppressing the diffusion of oxygen, so that the conductor 503b can be prevented from being oxidized and its conductivity from decreasing.

[0144] Furthermore, when the conductor 503 also functions as a wiring, it is preferable that the conductor 503b be made of a highly conductive material containing tungsten, copper, or aluminum as a main component. In this case, the conductor 503b is not necessarily provided. Note that although the conductor 503b is illustrated as a single layer, it may have a multilayer structure, for example, a multilayer structure of titanium or titanium nitride and the above-mentioned conductive material.

[0145] The insulators 520, 522, and 524 function as a second gate insulating film, and the insulator 550 functions as a first gate insulating film.

[0146] Here, the insulator 524 in contact with the oxide 530 preferably contains more oxygen than the oxygen required for the stoichiometric composition. That is, an excess oxygen region is preferably formed in the insulator 524. By providing such an insulator containing excess oxygen in contact with the oxide 530, oxygen vacancies in the oxide 530 can be reduced and the reliability of the transistor 500 can be improved.

[0147] Specifically, it is preferable to use an oxide material from which a portion of oxygen is released by heating as an insulator having an excess oxygen region. The oxide material from which oxygen is released by heating is an oxide material from which the amount of released oxygen converted to oxygen atoms is 1.0 × 10 in TDS (Thermal Desorption Spectroscopy) analysis. 18 atoms / cm 3 or more, preferably 1.0 × 10 19 atoms / cm 3 More preferably, 2.0 × 10 19 atoms / cm 3 or more, or 3.0 x 10 20 atoms / cm 3 The oxide film is one having the above properties. The surface temperature of the film during the TDS analysis is preferably in the range of 100°C or higher and 700°C or lower, or 100°C or higher and 400°C or lower.

[0148] Alternatively, the oxide 530 may be brought into contact with the insulator having the excess oxygen region and subjected to one or more of heat treatment, microwave treatment, and RF treatment. By performing such treatment, water or hydrogen in the oxide 530 can be removed. For example, in the oxide 530, V O A reaction occurs in which the bond of H is broken, in other words, "V O H→V O +H" reaction occurs, resulting in dehydrogenation. Some of the generated hydrogen may combine with oxygen to form HO and be removed from the oxide 530 or an insulator near the oxide 530. Some of the hydrogen may also be diffused or captured (also called gettered) in the conductor 542a and / or the conductor 542b.

[0149] The microwave treatment is preferably performed using, for example, an apparatus having a power source for generating high-density plasma or an apparatus having a power source for applying RF to the substrate side. For example, high-density oxygen radicals can be generated by using an oxygen-containing gas and high-density plasma, and the oxygen radicals generated by the high-density plasma can be efficiently introduced into the oxide 530 or an insulator near the oxide 530 by applying RF to the substrate side. The microwave treatment is performed at a pressure of 133 Pa or higher, preferably 200 Pa or higher, and more preferably 400 Pa or higher. The gases introduced into the microwave treatment apparatus may be, for example, oxygen and argon, with an oxygen flow ratio (O2 / (O2+Ar)) of 50% or less, preferably 10% to 30%.

[0150] During the manufacturing process of the transistor 500, heat treatment is preferably performed with the surface of the oxide 530 exposed. The heat treatment may be performed, for example, at a temperature of 100° C. to 450° C., more preferably 350° C. to 400° C. Note that the heat treatment is performed in a nitrogen gas or inert gas atmosphere, or an atmosphere containing an oxidizing gas at 10 ppm or more, 1% or more, or 10% or more. For example, the heat treatment is preferably performed in an oxygen atmosphere. This supplies oxygen to the oxide 530, thereby eliminating oxygen vacancies (V O ) can be reduced. The heat treatment may be performed under reduced pressure. 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 after the heat treatment in a nitrogen gas or inert gas atmosphere to compensate for the desorbed oxygen. 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 the heat treatment may be performed in a nitrogen gas or inert gas atmosphere.

[0151] By subjecting the oxide 530 to oxygen addition treatment, oxygen vacancies in the oxide 530 are repaired by the supplied oxygen. In other words, O Furthermore, the reaction of the hydrogen remaining in the oxide 530 with the supplied oxygen can be removed as HO (dehydration). As a result, the hydrogen remaining in the oxide 530 recombines with the oxygen vacancies to form V O The formation of H can be suppressed.

[0152] When the insulator 524 has an excess oxygen region, the insulator 522 preferably has a function of suppressing the diffusion of oxygen (for example, oxygen atoms, oxygen molecules, etc.) (preferably making the oxygen less permeable).

[0153] The insulator 522 preferably has a function of suppressing diffusion of oxygen and impurities, which prevents oxygen contained in the oxide 530 from diffusing toward the insulator 520. Furthermore, reaction of the conductor 503 with oxygen contained in the insulator 524 or the oxide 530 can be suppressed.

[0154] The insulator 522 is preferably a single-layer or multi-layer insulator containing a high-k material, such as aluminum oxide, hafnium oxide, oxide 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 highly integrated, thinner gate insulating films can cause problems such as leakage current. Using a high-k material for the insulator that functions as the gate insulating film allows for a reduction in the gate potential during transistor operation while maintaining the physical film thickness.

[0155] In particular, an insulator containing an oxide of one or both of aluminum and hafnium, which is an insulating material that has the function of suppressing the diffusion of impurities and oxygen (i.e., is difficult for oxygen to permeate), is preferably used. As an insulator containing an oxide of one or both of aluminum and hafnium, aluminum oxide, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate) is preferably used. When the insulator 522 is formed using such a material, the insulator 522 functions as a layer that suppresses oxygen release from the oxide 530 and the intrusion of impurities such as hydrogen into the oxide 530 from the periphery of the transistor 500.

[0156] Alternatively, for example, aluminum oxide, bismuth oxide, germanium oxide, niobium oxide, silicon oxide, titanium oxide, tungsten oxide, yttrium oxide, or zirconium oxide may be added to these insulators. Alternatively, these insulators may be nitrided. Silicon oxide, silicon oxynitride, or silicon nitride may be stacked on the above insulators.

[0157] Furthermore, it is preferable that the insulator 520 be thermally stable. For example, silicon oxide and silicon oxynitride are suitable because they are thermally stable. Furthermore, by combining a high-k insulator with silicon oxide or silicon oxynitride, it is possible to obtain the insulator 520 having a thermally stable layered structure with a high dielectric constant.

[0158] 6A and 6B, the second gate insulating film has a three-layer stack structure including the insulators 520, 522, and 524. However, the second gate insulating film may have a single-layer, two-layer, or four or more-layer stack structure. In this case, the second gate insulating film is not limited to a stack structure made of the same material, and may have a stack structure made of different materials.

[0159] In the transistor 500, a metal oxide functioning as an oxide semiconductor is preferably used for the oxide 530 including the channel formation region. For example, a metal oxide such as In-M-Zn oxide (wherein M is one or more elements selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, or the like) may be used for the oxide 530. In particular, the In-M-Zn oxide that can be used for the oxide 530 is preferably the CAAC-OS or CAC-OS described in Embodiment 4. Alternatively, an In-Ga oxide or an In-Zn oxide may be used for the oxide 530.

[0160] Furthermore, it is preferable to use a metal oxide with a low carrier concentration for the transistor 500. To lower the carrier concentration of a metal oxide, the impurity concentration in the metal oxide should be lowered to lower the density of defect states. In this specification and the like, a low impurity concentration and a low density of defect states 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.

[0161] In particular, hydrogen contained in the metal oxide reacts with oxygen that bonds with the metal atom to form water, which can cause oxygen vacancies in the metal oxide. When hydrogen enters an oxygen vacancy in the oxide 530, the oxygen vacancy and hydrogen bond to form V. O May form H. V O H functions as a donor and may generate electrons as carriers. Furthermore, some of the hydrogen may bond with oxygen, which is bonded to a metal atom, to generate electrons as carriers. Therefore, a transistor using a metal oxide containing a large amount of hydrogen is likely to have normally-on characteristics. Furthermore, since hydrogen in a metal oxide is easily moved by stresses such as heat and an electric field, the reliability of the transistor may be reduced if the metal oxide contains a large amount of hydrogen. In one embodiment of the present invention, V in the oxide 530 O It is preferable to reduce H as much as possible to obtain high-purity intrinsic or substantially high-purity intrinsic V. O To obtain metal oxides with sufficiently reduced H, it is important to remove impurities such as water and hydrogen from the metal oxide (sometimes referred to as dehydration or dehydrogenation treatment), and to supply oxygen to the metal oxide to compensate for oxygen deficiencies (sometimes referred to as oxygen addition treatment). O By using a metal oxide in which impurities such as H are sufficiently reduced for the channel formation region of a transistor, stable electrical characteristics can be achieved.

[0162] Defects in which hydrogen has entered oxygen vacancies can function as donors in metal oxides. However, it is difficult to quantitatively evaluate such defects. Therefore, metal oxides are sometimes evaluated using carrier concentration rather than donor concentration. Therefore, in this specification and the like, the carrier concentration assuming a state in which no electric field is applied may be used as a parameter of metal oxides, rather than donor concentration. In other words, the "carrier concentration" described in this specification and the like may sometimes be rephrased as "donor concentration."

[0163] Therefore, when a metal oxide is used for the oxide 530, it is preferable that the hydrogen in the metal oxide is reduced as much as possible. Specifically, in the metal oxide, the hydrogen concentration obtained by secondary ion mass spectrometry (SIMS) is set to 1×10 20 atoms / cm 3 Less than 1 x 10 19 atoms / cm 3 less than 5 × 10 18 atoms / cm 3 less than 1×10 18 atoms / cm 3 By using a metal oxide in which impurities such as hydrogen are sufficiently reduced for a channel formation region of a transistor, stable electrical characteristics can be obtained.

[0164] When a metal oxide is used for the oxide 530, the carrier concentration of the metal oxide in the channel formation region is 1×10 18 cm -3 Preferably, it is 1×10 or less. 17 cm -3 More preferably, it is less than 1×10 16 cm -3 More preferably, it is less than 1×10 13 cm -3 More preferably, it is less than 1×10 12 cm -3 The lower limit of the carrier concentration of the metal oxide in the channel formation region is not particularly limited, but is preferably, for example, 1×10 -9 cm -3 It can be said that:

[0165] Furthermore, when a metal oxide is used for the oxide 530, contact between the conductor 542a (conductor 542b) and the oxide 530 may cause oxygen in the oxide 530 to diffuse into the conductor 542a (conductor 542b), resulting in the oxidation of the conductor 542a (conductor 542b). The oxidation of the conductor 542a (conductor 542b) is likely to result in a decrease in the conductivity of the conductor 542a (conductor 542b). The diffusion of oxygen in the oxide 530 into the conductor 542a (conductor 542b) can be rephrased as the conductor 542a (conductor 542b) absorbing the oxygen in the oxide 530.

[0166] Furthermore, oxygen in the oxide 530 diffuses into the conductor 542a and the conductor 542b, which may form insulating regions at and near the interface between the conductor 542a and the oxide 530b, and at and near the interface between the conductor 542b and the oxide 530b. Since these regions contain more oxygen than the conductors 542a and 542b, they are presumed to have higher electrical resistance than the conductors 542a and 542b. In this case, the three-layer structure of the conductors 542a and 542b, the regions, and the oxide 530b can be considered a three-layer structure consisting of a metal, an insulator, and a semiconductor, and is sometimes called a metal-insulator-semiconductor (MIS) structure or a diode junction structure based on the MIS structure.

[0167] The insulating region is not limited to being formed between the conductor 542a (conductor 542b) and the oxide 530b, and may be formed, for example, between the conductor 542a (conductor 542b) and the oxide 530c, between the conductor 542a (conductor 542b) and the oxide 530b, or between the conductor 542a (conductor 542b) and the oxide 530c.

[0168] The metal oxide that functions as a channel formation region in the oxide 530 preferably has a band gap of 2 eV or more, preferably 2.5 eV or more. By using a metal oxide with a wide band gap, the off-state current of the transistor can be reduced.

[0169] The oxide 530 has the oxide 530a below the oxide 530b, which can prevent impurities from diffusing from structures formed below the oxide 530a to the oxide 530b. Also, the oxide 530 has the oxide 530c on the oxide 530b, which can prevent impurities from diffusing from structures formed above the oxide 530c to the oxide 530b.

[0170] The oxide 530 preferably has a layered structure made up of oxides with different atomic ratios of metal atoms. Specifically, the atomic ratio of the element M among the constituent elements in the metal oxide used for the oxide 530a is preferably greater than the atomic ratio of the element M among the constituent elements in the metal oxide used for the oxide 530b. The atomic ratio of the element M to In in the metal oxide used for the oxide 530a is preferably greater than the atomic ratio of the element M to In in the metal oxide used for the oxide 530b. The atomic ratio of In to M in the metal oxide used for the oxide 530b is preferably greater than the atomic ratio of In to M in the metal oxide used for the oxide 530a. The oxide 530c can be made up of the same metal oxide as that used for the oxide 530a or the oxide 530b.

[0171] For example, consider a case where an In-Ga-Zn oxide is used as the oxide 530. When an In-Ga-Zn oxide having an atomic ratio of In, Ga, and Zn of In:Ga:Zn=4:2:3 to 4.1 or a composition thereof is used as the oxide 530b, it is preferable to use an In-Ga-Zn oxide having an atomic ratio of In:Ga:Zn=1:3:4 or a composition thereof, or an In:Ga:Zn=1:1:1 or a composition thereof, as the oxide 530a. Furthermore, it is preferable that the oxide 530c is an In-Ga-Zn oxide having any one of the above compositions.

[0172] Furthermore, for example, when the atomic ratio of In to element M in the metal oxide used for oxide 530a is smaller than the atomic ratio of In to element M in the metal oxide used for oxide 530b, an In-Ga-Zn oxide having a composition in which the atomic ratio of In to Ga to Zn is In:Ga:Zn=5:1:6 or thereabouts, In:Ga:Zn=5:1:3 or thereabouts, or In:Ga:Zn=10:1:3 or thereabouts, can be used as oxide 530b.

[0173] The conduction band minimum energy of the oxide 530a and the oxide 530c is preferably higher than that of the oxide 530b. In other words, the electron affinity of the oxide 530a and the oxide 530c is preferably smaller than that of the oxide 530b.

[0174] Here, the energy level of the conduction band minimum changes gradually at the junction between the oxides 530a, 530b, and 530c. In other words, the energy level of the conduction band minimum at the junction between the oxides 530a, 530b, and 530c changes continuously or forms a continuous junction. To achieve this, it is preferable to reduce the defect level density of the mixed layers formed at the interface between the oxides 530a and 530b and at the interface between the oxides 530b and 530c.

[0175] Specifically, the oxides 530a and 530b, and the oxides 530b and 530c, each have a common element (main component) other than oxygen, thereby forming a mixed layer with a low density of defect states. For example, when the oxide 530b is an In-Ga-Zn oxide, the oxides 530a and 530c may be made of an In-Ga-Zn oxide, a Ga-Zn oxide, or gallium oxide.

[0176] In this case, the oxide 530b serves as the main carrier path. By configuring the oxide 530a and the oxide 530c as described above, the defect state density at the interface between the oxide 530a and the oxide 530b and at the interface between the oxide 530b and the oxide 530c can be reduced. As a result, the influence of interface scattering on carrier conduction is reduced, and the transistor 500 can obtain a high on-state current.

[0177] Conductors 542a and 542b, which function as a source electrode and a drain electrode, are provided on oxide 530b. Conductors 542a and 542b are preferably made of a metal element 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 an alloy containing any of the above metal elements or an alloy combining any of the above metal elements. For example, tantalum nitride, titanium nitride, tungsten nitride, a nitride containing titanium and aluminum, a nitride containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, an oxide containing strontium and ruthenium, or an oxide containing lanthanum and nickel is preferably used. In addition, 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 materials that maintain conductivity even when absorbing oxygen. Furthermore, metal nitride films such as tantalum nitride are preferred because they have barrier properties against hydrogen or oxygen.

[0178] 6, the conductors 542a and 542b are shown as single-layer structures, but they may also have a stacked structure of two or more layers. For example, a tantalum nitride film and a tungsten film may be stacked. Alternatively, a titanium film and an aluminum film may be stacked. Alternatively, a two-layer structure in which an aluminum film is stacked on a tungsten film, a two-layer structure in which a copper film is stacked on a copper-magnesium-aluminum alloy film, a two-layer structure in which a copper film is stacked on a titanium film, or a two-layer structure in which a copper film is stacked on a tungsten film may be used.

[0179] Further, there are three-layer structures in which a titanium film or titanium nitride film is laminated on the titanium film or titanium nitride film, an aluminum film or copper film is laminated on the titanium film or titanium nitride film, and a titanium film or titanium nitride film is further formed thereon, a three-layer structure in which a molybdenum film or molybdenum nitride film is laminated on the molybdenum film or molybdenum nitride film, an aluminum film or copper film is laminated on the molybdenum film or molybdenum nitride film, and a molybdenum film or molybdenum nitride film is further formed thereon, etc. Note that a transparent conductive material containing indium oxide, tin oxide, or zinc oxide may also be used.

[0180] 6A, regions 543a and 543b may be formed as low-resistance regions at and near the interface of the oxide 530 with the conductor 542a (conductor 542b). In this case, the region 543a functions as one of a source region and a drain region, and the region 543b functions as the other of the source region and the drain region. A channel formation region is formed in the region sandwiched between the regions 543a and 543b.

[0181] By providing the conductor 542a (conductor 542b) so as to be in contact with the oxide 530, the oxygen concentration in the region 543a (region 543b) may be reduced. Also, a metal compound layer containing the metal contained in the conductor 542a (conductor 542b) and components of the oxide 530 may be formed in the region 543a (region 543b). In such a case, the carrier concentration in the region 543a (region 543b) increases, and the region 543a (region 543b) becomes a low-resistance region.

[0182] The insulator 544 is provided to cover the conductors 542a and 542b and suppresses oxidation of the conductors 542a and 542b. In this case, the insulator 544 may be provided to cover the side surface of the oxide 530 and to be in contact with the insulator 524.

[0183] The insulator 544 can be a metal oxide containing one or more elements selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, neodymium, lanthanum, magnesium, etc. Alternatively, the insulator 544 can be silicon nitride oxide, silicon nitride, or the like.

[0184] In particular, it is preferable to use, as the insulator 544, an insulator containing an oxide of either or both of aluminum and hafnium, such as aluminum oxide, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate). Hafnium aluminate is particularly preferable because it has higher heat resistance than a hafnium oxide film. Therefore, it is less likely to crystallize during heat treatment in a later step. Note that if the conductors 542a and 542b are made of oxidation-resistant materials or materials whose conductivity does not decrease significantly even when they absorb oxygen, the insulator 544 is not an essential component. The insulator may be designed appropriately depending on the desired transistor characteristics.

[0185] The insulator 544 can prevent impurities such as water and hydrogen contained in the insulator 580 from diffusing to the oxide 530b through the oxide 530c and the insulator 550. The insulator 544 can also prevent the conductor 560 from being oxidized by excess oxygen contained in the insulator 580.

[0186] The insulator 550 functions as a first gate insulating film. The insulator 550 is preferably disposed in contact with the inside (top surface and side surface) of the oxide 530c. The insulator 550 is preferably formed using an insulator that contains excess oxygen and releases oxygen by heating, similar to the insulator 524 described above.

[0187] Specifically, silicon oxide having excess oxygen, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide to which fluorine is added, silicon oxide to which carbon is added, silicon oxide to which carbon and nitrogen are added, and silicon oxide having vacancies can be used. In particular, silicon oxide and silicon oxynitride are preferable because they are stable against heat.

[0188] By providing the insulator 550, which releases oxygen upon heating, in contact with the top surface of the oxide 530c, oxygen can be effectively supplied from the insulator 550 to the channel formation region of the oxide 530b through the oxide 530c. Similar to the insulator 524, the insulator 550 preferably has a low concentration of impurities such as water or hydrogen. The thickness of the insulator 550 is preferably 1 nm to 20 nm.

[0189] Furthermore, a metal oxide may be provided between the insulator 550 and the conductor 560 to efficiently supply excess oxygen contained in the insulator 550 to the oxide 530. The metal oxide preferably suppresses oxygen diffusion from the insulator 550 to the conductor 560. By providing a metal oxide that suppresses oxygen diffusion, the diffusion of excess oxygen from the insulator 550 to the conductor 560 is suppressed. In other words, a decrease in the amount of excess oxygen supplied to the oxide 530 can be suppressed. Furthermore, oxidation of the conductor 560 due to excess oxygen can be suppressed. As the metal oxide, a material that can be used for the insulator 544 may be used.

[0190] The insulator 550 may have a layered structure, similar to the second gate insulating film. As transistors become smaller and more highly integrated, thinner gate insulating films can cause problems such as leakage current. Therefore, by using a layered 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. Furthermore, a layered structure that is thermally stable and has a high dielectric constant can be achieved.

[0191] The conductor 560 functioning as the first gate electrode is shown as a two-layer structure in FIGS. 6A and 6B, but may be a single-layer structure or a stacked structure of three or more layers.

[0192] The conductor 560a is preferably made of a conductive material that suppresses the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (e.g., NO, NO, and the like), and copper atoms. Alternatively, a conductive material that suppresses the diffusion of oxygen (e.g., at least one of oxygen atoms, oxygen molecules, and the like) is preferably used. The conductor 560a has the function of suppressing the diffusion of oxygen, which can suppress the oxidation of the conductor 560b due to the oxygen contained in the insulator 550, thereby preventing a decrease in conductivity. Examples of conductive materials that suppress the diffusion of oxygen include tantalum, tantalum nitride, ruthenium, and ruthenium oxide. Alternatively, the conductor 560a can be made of an oxide semiconductor that can be used for the oxide 530. In this case, the conductor 560b can be formed by sputtering to reduce the electrical resistance of the conductor 560a, thereby making it a conductor. This can be called an OC (Oxide Conductor) electrode.

[0193] The conductor 560b is preferably made of a conductive material containing tungsten, copper, or aluminum as a main component. The conductor 560b also functions as wiring, so it is preferable to use a conductor with high conductivity. The conductor 560b may have a layered structure, such as a layered structure of titanium or titanium nitride and the above-mentioned conductive material.

[0194] The insulator 580 is provided over the conductor 542a and the conductor 542b with the insulator 544 interposed therebetween. The insulator 580 preferably has an excess oxygen region. For example, the insulator 580 preferably includes silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide doped with fluorine, silicon oxide doped with carbon, silicon oxide doped with carbon and nitrogen, silicon oxide having voids, or a resin. Silicon oxide and silicon oxynitride are particularly preferred because they are thermally stable. Silicon oxide and silicon oxide having voids are particularly preferred because they allow for easy formation of excess oxygen regions in a later step.

[0195] By providing the insulator 580, which has an excess oxygen region and releases oxygen when heated, in contact with the oxide 530c, oxygen in the insulator 580 can be efficiently supplied to the oxide 530a and the oxide 530b through the oxide 530c. Note that the concentration of impurities such as water and hydrogen in the insulator 580 is preferably reduced.

[0196] The opening of the insulator 580 is formed to overlap the region between the conductor 542a and the conductor 542b, so that the conductor 560 is formed to be embedded in the opening of the insulator 580 and the region sandwiched between the conductor 542a and the conductor 542b.

[0197] When miniaturizing semiconductor devices, it is necessary to shorten the gate length, but it is also necessary to prevent the conductivity of the conductor 560 from decreasing. If the film thickness of the conductor 560 is increased to achieve this, the conductor 560 may have a shape with a high aspect ratio. In this embodiment, the conductor 560 is provided so as to be embedded in the opening of the insulator 580. Therefore, even if the conductor 560 has a shape with a high aspect ratio, the conductor 560 can be formed without collapsing during the process.

[0198] The insulator 574 is preferably provided in contact with the top surface of the insulator 580, the top surface of the conductor 560, and the top surface of the insulator 550. By forming the insulator 574 by a sputtering method, excess oxygen regions can be provided in the insulator 550 and the insulator 580. This allows oxygen to be supplied from the excess oxygen regions into the oxide 530.

[0199] For example, the insulator 574 can be a metal oxide containing one or more elements selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, magnesium, and the like.

[0200] In particular, aluminum oxide has high barrier properties and can suppress the diffusion of hydrogen and nitrogen even when it is a thin film with a thickness of 0.5 nm to 3.0 nm. Therefore, aluminum oxide formed by sputtering can function as both an oxygen source and a barrier film against impurities such as hydrogen.

[0201] An insulator 581 functioning as an interlayer film is preferably provided over the insulator 574. Like the insulator 524, the insulator 581 preferably has a reduced concentration of impurities such as water or hydrogen.

[0202] Furthermore, the conductor 540a and the conductor 540b are placed in openings formed in the insulator 581, the insulator 574, the insulator 580, and the insulator 544. The conductor 540a and the conductor 540b are provided opposite each other with the conductor 560 interposed therebetween. The conductor 540a and the conductor 540b have the same structure as the conductor 546 and the conductor 548, which will be described later.

[0203] An insulator 582 is provided over the insulator 581. The insulator 582 is preferably formed using a substance that has a barrier property against oxygen and hydrogen. Therefore, the insulator 582 can be formed using a material similar to that of the insulator 514. For example, the insulator 582 is preferably formed using a metal oxide such as aluminum oxide, hafnium oxide, or tantalum oxide.

[0204] In particular, aluminum oxide has a high blocking effect of preventing the permeation of both oxygen and impurities such as hydrogen and moisture, which can cause fluctuations in the electrical characteristics of a transistor. Therefore, aluminum oxide can prevent impurities such as hydrogen and moisture from entering the transistor 500 during and after the transistor manufacturing process. Furthermore, aluminum oxide can suppress the release of oxygen from the oxide that constitutes the transistor 500. Therefore, aluminum oxide is suitable for use as a protective film for the transistor 500.

[0205] An insulator 586 is provided over the insulator 582. The insulator 586 can be formed using a material similar to that of the insulator 320. By using a material with a relatively low dielectric constant for these insulators, parasitic capacitance between wirings can be reduced. For example, a silicon oxide film, a silicon oxynitride film, or the like can be used as the insulator 586.

[0206] Furthermore, conductors 546, conductors 548, etc. are embedded in insulators 520, 522, 524, 544, 580, 574, 581, 582, and 586.

[0207] The conductor 546 and the conductor 548 function as a plug or a wiring that connects to the capacitor 600, the transistor 500, or the transistor 300. The conductor 546 and the conductor 548 can be formed using a material similar to that of the conductor 328 and the conductor 330.

[0208] After the transistor 500 is formed, 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 surrounding the transistor 500 with the insulator with high barrier properties, it is possible to prevent moisture and hydrogen from entering from the outside. Alternatively, multiple transistors 500 may be collectively surrounded by an insulator with high barrier properties against hydrogen or water. When forming an opening to surround the transistor 500, for example, it is preferable to form an opening that reaches the insulator 514 or the insulator 522 and form the insulator with high barrier properties in contact with the insulator 514 or the insulator 522, because this can serve as part of the manufacturing process of the transistor 500. For example, the insulator with high barrier properties against hydrogen or water may be made of a material similar to that of the insulator 522.

[0209] Subsequently, a capacitor 600 is provided above the transistor 500. The capacitor 600 includes a conductor 610, a conductor 620, and an insulator 630.

[0210] A conductor 612 may be provided over the conductor 546 and the conductor 548. The conductor 612 functions as a plug or a wiring connected to the transistor 500. The conductor 610 functions as an electrode of the capacitor 600. Note that the conductor 612 and the conductor 610 can be formed at the same time.

[0211] A metal film containing an element selected from molybdenum, titanium, tantalum, tungsten, aluminum, copper, chromium, neodymium, and scandium, or a metal nitride film containing any of the above elements (tantalum nitride film, titanium nitride film, molybdenum nitride film, tungsten nitride film), or the like can be used for the conductor 612 and the conductor 610. Alternatively, a conductive material 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 to which silicon oxide is added can also be used.

[0212] 4, the conductor 612 and the conductor 610 have a single-layer structure, but are not limited to this structure and may have a stacked structure of two or more layers. For example, a conductor having a barrier property and a conductor having high adhesion to the conductor having high conductivity may be formed between a conductor having a barrier property and a conductor having high conductivity.

[0213] The conductor 620 is provided to overlap with the conductor 610 with the insulator 630 interposed therebetween. Note that the conductor 620 can be formed using a conductive material such as a metal material, an alloy material, or a metal oxide material. It is preferable to use a high-melting-point material such as tungsten or molybdenum that has both heat resistance and conductivity, and tungsten is particularly preferable. Furthermore, when the conductor 620 is formed simultaneously with other structures such as a conductor, a low-resistance metal material such as Cu (copper) or Al (aluminum) can be used.

[0214] An insulator 640 is provided over the conductor 620 and the insulator 630. The insulator 640 can be provided using a material similar to that of the insulator 320. The insulator 640 may also function as a planarizing film that covers the uneven shape underneath.

[0215] Next, the capacitive element 600 of the semiconductor device of Figures 4 and 5 will be described. Figure 7 shows a capacitive element 600A as an example of a capacitive element 600 that can be applied to a semiconductor device. Figure 7A is a top view of capacitive element 600A, Figure 7B is a perspective view showing a cross section of capacitive element 600A taken along dashed line L3-L4, and Figure 7C is a perspective view showing a cross section of capacitive element 600A taken along dashed line W3-L4.

[0216] The conductor 610 functions as one of a pair of electrodes of the capacitor 600A, and the conductor 620 functions as the other of the pair of electrodes of the capacitor 600A. The insulator 630 functions as a dielectric sandwiched between the pair of electrodes.

[0217] The capacitor 600 is electrically connected to the conductor 546 and the conductor 548 below the conductor 610. The conductors 546 and 548 function as plugs or wiring for connecting to other circuit elements. In addition, in FIG. 7, the conductors 546 and 548 are collectively referred to as the conductor 540.

[0218] Also, in Figure 7, for clarity, the insulator 586 in which the conductors 546 and 548 are embedded, and the insulator 640 covering the conductor 620 and the insulator 630 are omitted.

[0219] 4, 5, and 7 is a planar type, the shape of the capacitive element is not limited to this. For example, the capacitive element 600 may be a cylindrical capacitive element 600B shown in FIG. 8.

[0220] 8A is a top view of the capacitive element 600B, FIG. 8B is a cross-sectional view of the capacitive element 600B taken along the dashed dotted line L3-L4, and FIG. 8C is a perspective view showing the cross-section of the capacitive element 600B taken along the dashed dotted line W3-L4.

[0221] In Figure 8B, the capacitor element 600B has an insulator 631 on an insulator 586 in which a conductor 540 is embedded, an insulator 651 having an opening, a conductor 610 that functions as one of a pair of electrodes, and a conductor 620 that functions as the other of the pair of electrodes.

[0222] Also, in FIG. 8C, insulator 586, insulator 650, and insulator 651 are omitted for clarity.

[0223] The insulator 631 can be formed using, for example, a material similar to that of the insulator 586.

[0224] Furthermore, a conductor 611 is embedded in the insulator 631 so as to be electrically connected to the conductor 540. The conductor 611 can be made of the same material as the conductors 330 and 518, for example.

[0225] The insulator 651 can be formed using, for example, a material similar to that of the insulator 586.

[0226] As described above, the insulator 651 has an opening that overlaps with the conductor 611.

[0227] The conductor 610 is formed on the bottom and side surfaces of the opening. That is, the conductor 610 overlaps with the conductor 611 and is electrically connected to the conductor 611.

[0228] The conductor 610 is formed by forming an opening in the insulator 651 by etching or the like, and then depositing the conductor 610 by sputtering, ALD or the like. Thereafter, the conductor 610 deposited on the insulator 651 may be removed by CMP (Chemical Mechanical Polishing) or the like, leaving the conductor 610 deposited in the opening.

[0229] The insulator 630 is located on the insulator 651 and on the surface on which the conductor 610 is formed. The insulator 630 functions as a dielectric sandwiched between a pair of electrodes in the capacitor.

[0230] The conductor 620 is formed on the insulator 630 so that the opening of the insulator 651 is filled.

[0231] The insulator 650 is formed to cover the insulator 630 and the conductor 620 .

[0232] 8 can have a higher capacitance value than the planar capacitive element 600A. Therefore, by using the capacitive element 600B, the voltage between the terminals of the capacitive element can be maintained for a long period of time.

[0233] By using this structure, miniaturization or high integration can be achieved in a semiconductor device including a transistor including an oxide semiconductor.

[0234] Note that this embodiment mode can be appropriately combined with other embodiment modes described in this specification.

[0235] (Fourth embodiment) In this embodiment, structures of a cloud-aligned composite oxide semiconductor (CAC-OS) and a c-axis aligned crystalline oxide semiconductor (CAAC-OS), which are metal oxides that can be used for the OS transistors described in the above embodiments, will be described.

[0236] <Metal oxide composition> CAC-OS or CAC-metal oxide has a conductive function in a part of the material and an insulating function in a part of the material, and functions as a semiconductor as a whole. When CAC-OS or CAC-metal oxide is used in the active layer of a transistor, the conductive function is a function of allowing electrons (or holes) to flow as carriers, and the insulating function is a function of preventing electrons from flowing as carriers. By making the conductive function and the insulating function act complementarily, a switching function (on / off function) can be imparted to CAC-OS or CAC-metal oxide. By separating the respective functions in CAC-OS or CAC-metal oxide, both functions can be maximized.

[0237] Furthermore, CAC-OS or CAC-metal oxide has a conductive region and an insulating region. The conductive region has the above-mentioned conductive function, and the insulating region has the above-mentioned insulating function. In addition, in the material, the conductive region and the insulating region may be separated at the nanoparticle level. In addition, the conductive region and the insulating region may be unevenly distributed in the material. In addition, the conductive region may be observed as connected in a cloud-like shape with the periphery blurred.

[0238] In addition, in CAC-OS or CAC-metal oxide, the conductive regions and the insulating regions may be dispersed in the material with sizes of 0.5 nm to 10 nm, preferably 0.5 nm to 3 nm.

[0239] Furthermore, the CAC-OS or CAC-metal oxide is composed of components having different band gaps. For example, the CAC-OS or CAC-metal oxide is composed of a component having a wide gap due to an insulating region and a component having a narrow gap due to a conductive region. In this configuration, when carriers flow, the carriers mainly flow in the component having the narrow gap. Furthermore, the component having the narrow gap acts complementarily with the component having the wide gap, and carriers also flow in the component having the wide gap in conjunction with the component having the narrow gap. Therefore, when the CAC-OS or CAC-metal oxide is used in the channel formation region of a transistor, the transistor can achieve high current driving power in the on state, i.e., a large on-state current, and high field-effect mobility.

[0240] That is, CAC-OS or CAC-metal oxide can also be called a matrix composite or a metal matrix composite.

[0241] <Metal oxide structure> Oxide semiconductors are classified into single-crystal oxide semiconductors and non-single-crystal oxide semiconductors, such as c-axis aligned crystalline oxide semiconductors (CAAC-OS), polycrystalline oxide semiconductors, nanocrystalline oxide semiconductors (nc-OS), amorphous-like oxide semiconductors (a-like OS), and amorphous oxide semiconductors.

[0242] Furthermore, when focusing on the crystal structure, oxide semiconductors may be classified differently from the above. Here, the classification of the crystal structure of oxide semiconductors will be explained using FIG. 9A. FIG. 9A is a diagram explaining the classification of the crystal structure of oxide semiconductors, typically IGZO (a metal oxide containing In, Ga, and Zn).

[0243] As shown in Figure 9A, IGZO can be broadly classified into Amorphous, Crystalline, and Crystal. Amorphous includes completely amorphous. Crystalline includes c-axis aligned crystalline (CAAC), nanocrystalline (nc), and cloud-aligned composite (CAC). Crystal includes single crystal and polycrystalline.

[0244] The structure within the bold frame in Figure 9A belongs to the newcrystalline phase. This structure is in the boundary region between amorphous and crystalline. In other words, this structure is completely different from the energetically unstable amorphous and crystalline phases.

[0245] The crystalline structure of the film or substrate can be evaluated using X-ray diffraction (XRD) images. Figures 9B and 9C show the XRD spectra of silica glass and IGZO (also called crystalline IGZO), which has a crystalline structure classified as crystalline. Figure 9B shows the XRD spectrum of silica glass, while Figure 9C shows the XRD spectrum of crystalline IGZO. The crystalline IGZO shown in Figure 9C has a composition of In:Ga:Zn=4:2:3 [atomic ratio]. The crystalline IGZO shown in Figure 9C has a thickness of 500 nm.

[0246] As shown by the arrows in Figure 9B, the peaks in the XRD spectrum of silica glass are nearly symmetrical. On the other hand, as shown by the arrows in Figure 9C, the peaks in the XRD spectrum of crystalline IGZO are asymmetrical. The asymmetric peaks in the XRD spectrum clearly indicate the presence of crystals. In other words, if the peaks in the XRD spectrum are not symmetrical, it cannot be said to be amorphous.

[0247] CAAC-OS has a c-axis orientation and a distorted crystal structure in which multiple nanocrystals are connected in the a-b plane. The distorted structure refers to the change in the lattice orientation between regions with a uniform lattice arrangement and regions with a different uniform lattice arrangement in the regions where multiple nanocrystals are connected.

[0248] Nanocrystals are basically hexagonal, but not necessarily regular hexagonal, and may have non-regular hexagonal shapes. Furthermore, distortion can result in pentagonal, heptagonal, and other lattice arrangements. In CAAC-OS, no clear grain boundaries can be observed even near the distortion. This indicates that the formation of grain boundaries is suppressed by the distortion of the lattice arrangement. This is thought to be because CAAC-OS can tolerate distortion due to the lack of close-packed oxygen atom arrangement in the a-b plane and the change in interatomic bond distance caused by the substitution of metal elements.

[0249] The CAAC-OS also tends to have a layered crystal structure (also referred to as a layered structure) in which a layer containing indium and oxygen (hereinafter referred to as an In layer) and a layer containing the element M, zinc, and oxygen (hereinafter referred to as an (M,Zn) layer) are stacked. Note that indium and the element M are mutually substituted, and when the element M in an (M,Zn) layer is substituted with indium, the layer can also be referred to as an (In,M,Zn) layer. When the indium in an In layer is substituted with the element M, the layer can also be referred to as an (In,M) layer.

[0250] CAAC-OS is an oxide semiconductor with high crystallinity. On the other hand, because no clear grain boundaries are observed in CAAC-OS, it can be said that the decrease in electron mobility due to the grain boundaries is unlikely to occur. Furthermore, because the crystallinity of oxide semiconductors can be reduced by the inclusion of impurities or the generation of defects, CAAC-OS can be considered an oxide semiconductor with few impurities and defects (such as oxygen vacancies). Therefore, oxide semiconductors with CAAC-OS have stable physical properties. Therefore, oxide semiconductors with CAAC-OS are heat-resistant and highly reliable. Furthermore, CAAC-OS is stable even under high temperatures (so-called thermal budgets) during the manufacturing process. Therefore, using CAAC-OS for OS transistors enables greater flexibility in the manufacturing process.

[0251] The nc-OS has periodic atomic arrangement in a microscopic region (for example, a region of 1 nm to 10 nm, particularly a region of 1 nm to 3 nm). Furthermore, the nc-OS exhibits no regularity in the crystal orientation between different nanocrystals. Therefore, no orientation is observed throughout the film. Therefore, depending on the analytical method, the nc-OS may be indistinguishable from a-like OS or amorphous oxide semiconductors.

[0252] The a-like OS is an oxide semiconductor having a structure between the nc-OS and the amorphous oxide semiconductor. The a-like OS has a pore or low-density region. That is, the a-like OS has lower crystallinity than the nc-OS and CAAC-OS.

[0253] Oxide semiconductors have a variety of structures and each has different characteristics. The oxide semiconductor of one embodiment of the present invention may include two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, an a-like OS, an nc-OS, and a CAAC-OS.

[0254] <Transistors containing oxide semiconductors> Next, a case where the oxide semiconductor is used in a transistor will be described.

[0255] By using the oxide semiconductor for a transistor, a transistor with high field-effect mobility and high reliability can be realized.

[0256] In addition, it is preferable to use an oxide semiconductor with a low carrier concentration for the transistor. In order to reduce the carrier concentration of the oxide semiconductor film, the impurity concentration in the oxide semiconductor film may be reduced to reduce the density of defect states. In this specification and the like, a semiconductor having a low impurity concentration and a low density of defect states is referred to as a highly purified intrinsic semiconductor or a substantially highly purified intrinsic semiconductor.

[0257] Furthermore, a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film has a low density of defect states, and therefore the density of trap states may also be low.

[0258] Furthermore, charges trapped in the trap states of an oxide semiconductor take a long time to disappear and may behave like fixed charges. Therefore, a transistor in which a channel formation region is formed in an oxide semiconductor with a high density of trap states may have unstable electrical characteristics.

[0259] Therefore, in order to stabilize the electrical characteristics of a transistor, it is effective to reduce the impurity concentration in the oxide semiconductor. Furthermore, in order to reduce the impurity concentration in the oxide semiconductor, it is preferable to also reduce the impurity concentration in the adjacent film. Examples of impurities include hydrogen, nitrogen, alkali metals, alkaline earth metals, iron, nickel, and silicon.

[0260] <Impurities> Here, the influence of each impurity in an oxide semiconductor will be described.

[0261] When an oxide semiconductor contains silicon or carbon, which is one of the Group 14 elements, defect levels are formed in the oxide semiconductor. Therefore, the concentrations of silicon or carbon in the oxide semiconductor and those near the interface with the oxide semiconductor (concentrations obtained by secondary ion mass spectrometry (SIMS)) are calculated as follows: 18 atoms / cm 3 Less than or equal to 2 x 10 17 atoms / cm 3 The following applies.

[0262] Furthermore, when an oxide semiconductor contains an alkali metal or alkaline earth metal, defect states may be formed and carriers may be generated. Therefore, a transistor using an oxide semiconductor containing an alkali metal or alkaline earth metal is likely to have normally-on characteristics. For this reason, it is preferable to reduce the concentration of the alkali metal or alkaline earth metal in the oxide semiconductor. Specifically, the concentration of the alkali metal or alkaline earth metal in the oxide semiconductor obtained by SIMS is preferably reduced to 1×10 18 atoms / cm 3 Less than or equal to 2 x 10 16 atoms / cm 3 Do the following:

[0263] Furthermore, when nitrogen is contained in an oxide semiconductor, electrons serving as carriers are generated, the carrier concentration increases, and the semiconductor is likely to become n-type. As a result, a transistor using an oxide semiconductor containing nitrogen as a semiconductor tends to have normally-on characteristics. Therefore, it is preferable that the nitrogen content in the oxide semiconductor be reduced as much as possible. For example, the nitrogen concentration in the oxide semiconductor is 5×10 19 atoms / cm 3 Less than 5 x 10 18 atoms / cm 3 Less than 1×10, more preferably 18 atoms / cm 3 Less than 5 × 10, more preferably 17 atoms / cm 3 The following applies.

[0264] Furthermore, hydrogen contained in an oxide semiconductor may react with oxygen bonded to a metal atom to form water, which may form an oxygen vacancy. When hydrogen enters the oxygen vacancy, electrons serving as carriers may be generated. Furthermore, some of the hydrogen may bond with oxygen bonded to a metal atom to generate electrons serving as carriers. Therefore, a transistor using an oxide semiconductor containing hydrogen is likely to have normally-on characteristics. For this reason, it is preferable to reduce the amount of hydrogen in the oxide semiconductor as much as possible. Specifically, the hydrogen concentration in an oxide semiconductor measured by SIMS is 1×10 20 atoms / cm 3 Less than 1 x 10 19 atoms / cm 3 less than 5 × 10 18 atoms / cm 3 less than 1×10 18 atoms / cm 3 Less than.

[0265] When an oxide semiconductor with sufficiently reduced impurities is used for a channel formation region of a transistor, stable electrical characteristics can be obtained.

[0266] Note that this embodiment mode can be appropriately combined with other embodiment modes described in this specification.

[0267] (Embodiment 5) This embodiment mode will describe an example of a semiconductor wafer on which the semiconductor device or the like shown in the above embodiment mode is formed, and an electronic component in which the semiconductor device is incorporated.

[0268] <Semiconductor wafer> First, an example of a semiconductor wafer on which a semiconductor device or the like is formed will be described with reference to FIG. 10A.

[0269] 10A includes a wafer 4801 and a plurality of circuit portions 4802 provided on the upper surface of the wafer 4801. Note that on the upper surface of the wafer 4801, a portion where the circuit portions 4802 are not present is a spacing 4803, which is a region for dicing.

[0270] The semiconductor wafer 4800 can be manufactured by forming a plurality of circuit portions 4802 on the surface of the wafer 4801 in a previous process. After that, the surface of the wafer 4801 opposite to the surface on which the plurality of circuit portions 4802 are formed may be ground to thin the wafer 4801. This process reduces warping of the wafer 4801 and allows for miniaturization of the component.

[0271] The next step is the dicing process. Dicing is performed along scribe lines SCL1 and SCL2 (sometimes called dicing lines or cutting lines) indicated by dashed lines. To facilitate the dicing process, spacing 4803 is preferably arranged so that multiple scribe lines SCL1 are parallel to each other, multiple scribe lines SCL2 are parallel to each other, and scribe lines SCL1 and SCL2 are perpendicular to each other.

[0272] By performing a dicing process, chips 4800a such as those shown in FIG. 10B can be cut out from semiconductor wafer 4800. Chip 4800a includes wafer 4801a, circuit portion 4802, and spacing 4803a. It is preferable to make spacing 4803a as small as possible. In this case, it is sufficient that the width of spacing 4803 between adjacent circuit portions 4802 is approximately the same length as the cutting margin of scribe line SCL1 or the cutting margin of scribe line SCL2.

[0273] Note that the shape of the element substrate of one embodiment of the present invention is not limited to the shape of the semiconductor wafer 4800 illustrated in Figure 10A. For example, the semiconductor wafer may have a rectangular shape. The shape of the element substrate can be changed as appropriate depending on the manufacturing process and the apparatus for manufacturing the element.

[0274] <Electronic components> Next, an example of an electronic component incorporating chip 4800a will be described with reference to FIGS. 10C and 10D.

[0275] Fig. 10C shows a perspective view of electronic component 4700 and a substrate (mounting substrate 4704) on which electronic component 4700 is mounted. Electronic component 4700 shown in Fig. 10C has leads 4701 and chip 4800a described above, and functions as an IC chip or the like.

[0276] Electronic component 4700 can be fabricated, for example, by performing a wire bonding process in which leads 4701 of a lead frame are electrically connected to electrodes on chip 4800a using thin metal wires, a molding process in which they are sealed with epoxy resin or the like, a plating process on leads 4701 of the lead frame, and a printing process on the surface of the package. The wire bonding process can be performed using, for example, ball bonding or wedge bonding. Although FIG. 10C shows electronic component 4700 packaged as a QFP (Quad Flat Package), the package form is not limited thereto.

[0277] The electronic component 4700 is mounted on, for example, a printed circuit board 4702. A plurality of such IC chips are combined and electrically connected on the printed circuit board 4702 to complete a mounting board 4704.

[0278] 10D shows a perspective view of electronic component 4730. Electronic component 4730 is an example of a SiP (System in Package) or MCM (Multi Chip Module). Electronic component 4730 has an interposer 4731 provided on a package substrate 4732 (printed circuit board), and a semiconductor device 4735 and multiple semiconductor devices 4710 provided on interposer 4731.

[0279] The electronic component 4730 includes a semiconductor device 4710. The semiconductor device 4710 can be, for example, any of the semiconductor devices described in the above embodiments or a high bandwidth memory (HBM). The semiconductor device 4735 can be an integrated circuit (semiconductor device) such as a CPU, a GPU, an FPGA, or a memory device.

[0280] A ceramic substrate, a plastic substrate, a glass epoxy substrate, or the like can be used for the package substrate 4732. A silicon interposer, a resin interposer, or the like can be used for the interposer 4731.

[0281] The interposer 4731 has multiple wirings and functions to electrically connect multiple integrated circuits with different terminal pitches. The multiple wirings are provided in a single layer or multiple layers. The interposer 4731 also functions to electrically connect the integrated circuits provided on the interposer 4731 to electrodes provided on the package substrate 4732. For these reasons, the interposer is sometimes called a "rewiring substrate" or "intermediate substrate." In some cases, through electrodes are provided in the interposer 4731, and the integrated circuits and the package substrate 4732 are electrically connected using the through electrodes. In addition, in a silicon interposer, TSVs (Through Silicon Vias) can also be used as through electrodes.

[0282] It is preferable to use a silicon interposer as the interposer 4731. Since a silicon interposer does not require an active element, it can be manufactured at a lower cost than an integrated circuit. On the other hand, since the wiring of a silicon interposer can be formed using a semiconductor process, it is easy to form fine wiring that is difficult to form with a resin interposer.

[0283] HBM requires many interconnects to achieve a wide memory bandwidth. Therefore, the interposer that implements HBM requires fine and high-density interconnects. Therefore, it is preferable to use a silicon interposer for implementing HBM.

[0284] Furthermore, in SiPs and MCMs that use silicon interposers, a decrease in reliability due to differences in the coefficient of expansion between the integrated circuit and the interposer is unlikely to occur. Furthermore, because the surface of a silicon interposer is highly flat, poor connections between the integrated circuit mounted on the silicon interposer and the silicon interposer are unlikely to occur. In particular, it is preferable to use silicon interposers in 2.5D packages (2.5-dimensional packaging), in which multiple integrated circuits are arranged horizontally on an interposer.

[0285] A heat sink (heat sink) may be provided overlapping the electronic component 4730. When a heat sink is provided, it is preferable to align the height of an integrated circuit provided on the interposer 4731. For example, in the electronic component 4730 shown in this embodiment, it is preferable to align the height of the semiconductor device 4710 and the height of the semiconductor device 4735.

[0286] Electrodes 4733 may be provided on the bottom of package substrate 4732 in order to mount electronic component 4730 on another substrate. Fig. 10D shows an example in which electrodes 4733 are formed with solder balls. By providing solder balls in a matrix on the bottom of package substrate 4732, BGA (Ball Grid Array) mounting can be achieved. Electrodes 4733 may also be formed with conductive pins. By providing conductive pins in a matrix on the bottom of package substrate 4732, PGA (Pin Grid Array) mounting can be achieved.

[0287] The electronic component 4730 can be mounted on other substrates using various mounting methods, including but not limited to BGA and PGA, such as a staggered pin grid array (SPGA), a land grid array (LGA), a quad flat package (QFP), a quad flat J-leaded package (QFJ), or a quad flat non-leaded package (QFN).

[0288] Note that this embodiment mode can be appropriately combined with other embodiment modes described in this specification.

[0289] (Sixth embodiment) In this embodiment mode, an electronic device to which the semiconductor device described in the above embodiment mode is applied will be described.

[0290] 11 shows an example of the configuration of the semiconductor device described in the above embodiment. Electronic device 100 includes circuit 20, which is the semiconductor device, detection unit 30, processing unit 40, storage unit 50, display unit 60, and power supply circuit 70.

[0291] The electronic device 100 functions as a sensor that acquires a detection object 90 from the outside and converts the detection object 90 into information such as an electrical signal. The detection object 90 includes, for example, temperature, light (including visible light, X-rays, ultraviolet light, infrared light, etc.), sound, substances (components) such as water and gas, force, displacement, position, speed, acceleration, angular velocity, number of rotations, magnetism, electric field, current, voltage, power, radiation, flow rate, gradient, etc.

[0292] The detection unit 30 has a function of detecting one or a selected plurality of the above-described detection objects 90, and a function of outputting a current when the detection object 90 is detected. Note that the detection unit 30 is preferably configured so that the magnitude of the output current changes depending on the amount, strength, size, etc. of the detection object. The output current is input to the input terminal of the circuit 20.

[0293] As explained in the above embodiment, the circuit 20 outputs a voltage to the output terminal in accordance with the current input to the input terminal. The voltage is supplied to the processing unit 40.

[0294] The power supply circuit 70 has the function of supplying power to devices included in the electronic device 100, such as the circuit 20 and the detection unit 30.

[0295] The processing unit 40 has a function of calculating the physical quantity of the detection target 90 based on the voltage output from the circuit 20. The calculated physical quantity is sent to the storage unit 50 and / or the display unit 60.

[0296] The storage unit 50 has a function of storing the physical quantities sent from the processing unit 40. Note that depending on the use of the electronic device 100, the storage unit 50 may not be included in the electronic device 100.

[0297] The display unit 60 has a function of visually displaying the physical quantity sent from the processing unit 40. The display unit 60 may be, for example, a display device (such as a liquid crystal display device or a light emitting device), a meter (a measuring instrument), or the like.

[0298] Next, an example of a product that can be used as the electronic device 100 will be described.

[0299] [Video camera] The electronic device 100 described above can be applied to a video camera.

[0300] 12A shows a video camera 6300, which is an example of an imaging device. The video camera 6300 has a first housing 6301, a second housing 6302, a display unit 6303, operation keys 6304, a lens 6305, a connection unit 6306, and the like. The operation keys 6304 and the lens 6305 are provided in the first housing 6301, and the display unit 6303 is provided in the second housing 6302. The first housing 6301 and the second housing 6302 are connected by the connection unit 6306, and the angle between the first housing 6301 and the second housing 6302 can be changed by the connection unit 6306. The image on the display unit 6303 may be switched according to the angle between the first housing 6301 and the second housing 6302 at the connection unit 6306.

[0301] The video camera 6300 captures an image as detection of the detection target object 90. Therefore, the detection unit 30 corresponds to a cell (image sensor) including a photoelectric conversion element (imaging element) in the video camera 6300, and the display unit 60 corresponds to the display unit 6303.

[0302] [camera] The electronic device 100 described above can be applied to a camera.

[0303] 12B shows a digital camera 6240, which is an example of an imaging device. The digital camera 6240 has a housing 6241, a display unit 6242, operation buttons 6243, a shutter button 6244, etc., and is also equipped with a detachable lens 6246. Note that, although the digital camera 6240 is configured such that the lens 6246 can be detached from the housing 6241 and replaced, the lens 6246 and the housing 6241 may be integrated. The digital camera 6240 may also be configured such that a strobe device, a viewfinder, etc. can be separately attached.

[0304] The digital camera 6240 captures an image of the subject to detect the detection target 90. Therefore, the detection unit 30 corresponds to a cell (image sensor) including a photoelectric conversion element (imaging element) in the digital camera 6240, and the display unit 60 corresponds to the display unit 6242.

[0305] Furthermore, the detection object 90 may not only be the subject, but also the brightness of external light. This allows the digital camera 6240 to have a function of automatically turning on a flash according to the brightness of the environment, a function of adjusting the color of a captured image, and the like.

[0306] [robot] The electronic device 100 described above can be applied to a robot.

[0307] 12C shows an example of a robot. The robot 6140 has contact sensors 6141a to 6141e. The robot 6140 can grasp an object using the contact sensors 6141a to 6141e. The contact sensors 6141a to 6141e have a function of causing a current to flow through the object depending on the contact area when the contact sensor 6141a to 6141e touches the object, and the robot 6140 can recognize that it is grasping the object from the amount of current flowing.

[0308] 12D shows an example of an industrial robot. The industrial robot preferably has multiple drive axes to precisely control the driving range. An example of an industrial robot 6150 is shown, which includes a functional unit 6151, a control unit 6152, a drive axis 6153, a drive axis 6154, and a drive axis 6155. The functional unit 6151 preferably has a sensor such as an image detection module.

[0309] Furthermore, it is preferable that the functional unit 6151 has one or more functions such as gripping, cutting, welding, coating, and pasting an object. When the responsiveness of the industrial robot 6150 is improved, the productivity improves proportionally. Furthermore, in order for the industrial robot 6150 to perform precise operations, it is preferable to provide a sensor that detects minute currents.

[0310] [Alarm] 12E shows an alarm 6900. The alarm 6900 includes a sensor 6901, a receiver 6902, and a transmitter 6903.

[0311] The sensor 6901 has a sensor circuit 6904, a window 6905, operation keys 6906, etc. Light passing through the window 6905 is irradiated onto the sensor circuit 6904. The sensor circuit 6904 can be, for example, a detector that detects a detection object 90 such as a water leak, an electric leak, a gas leak, a fire, the water level of a river that may overflow, the seismic intensity of an earthquake, or radiation. For example, when the sensor circuit 6904 detects a detection object 90 that is equal to or greater than a specified value, the sensor 6901 sends the information to the receiver 6902. The receiver 6902 has a display unit 6907, operation keys 6908 and 6909, wiring 6910, etc. The receiver 6902 controls the operation of the transmitter 6903 according to the information from the sensor 6901. The transmitter 6903 has a speaker 6911, a lighting device 6912, etc. Transmitter 6903 has a function of issuing an alarm in accordance with a command from receiver 6902. Fig. 12E shows an example in which transmitter 6903 issues both an audio alarm using speaker 6911 and an optical alarm using lighting device 6912 such as a red light, but transmitter 6903 may issue only one of the alarms or other alarms.

[0312] Furthermore, if the sensor circuit functions as a fire alarm, the receiver 6902 may send a command to fire prevention equipment such as a shutter to perform a predetermined operation when an alarm is issued. Also, although Fig. 12E illustrates an example in which signals are transmitted and received wirelessly between the receiver 6902 and the sensor 6901, signals may be transmitted and received via wiring or the like. Also, Fig. 12E illustrates an example in which signals are transmitted from the receiver 6902 to the transmitter 6903 via wiring 6910, signals may be transmitted wirelessly.

[0313] [ICD] The electronic device 100 described above can be applied to an implantable cardioverter defibrillator (ICD).

[0314] 13A is a cross-sectional schematic diagram showing an example of an ICD. ICD main body 5300 has at least batteries 5301a and 5301b, a regulator, a control circuit, an antenna 5304, a wire 5302 to the right atrium, and a wire 5303 to the right ventricle.

[0315] The ICD body 5300 is placed in the body by surgery, and the two wires are passed through the subclavian vein 5305 and superior vena cava 5306 of the human body so that one wire tip is placed in the right ventricle and the other wire tip is placed in the right atrium.

[0316] The ICD main body 5300 functions as a pacemaker and paces the heart when the heart rate falls outside a specified range. If the heart rate does not improve with pacing (such as in the case of fast ventricular tachycardia or ventricular fibrillation), treatment with an electric shock is administered.

[0317] The ICD main body 5300 must constantly monitor the heart rate in order to properly perform pacing and administer electric shocks. Therefore, the ICD main body 5300 has a sensor for detecting the heart rate. The electronic device 100 shown in FIG. 11 can be used as the sensor. In this case, the object to be detected 90 is the heart rate. Furthermore, since the ICD main body 5300 is placed inside the body, it does not need to have a display unit 60. Furthermore, the ICD main body 5300 can store heart rate data, the number of times pacing treatment has been performed, the duration, etc. in the memory unit 50.

[0318] In addition, power can be received by the antenna 5304, and the power is charged into multiple batteries 5301a and 5301b, reducing the frequency of pacemaker replacement. As the ICD main body 5300 has multiple batteries, it is highly safe and can also function as an auxiliary power source, as the other batteries can continue to function even if one fails.

[0319] In addition to the antenna 5304 that can receive power, an antenna that can transmit physiological signals may be provided, and a system for monitoring cardiac activity may be configured in which physiological signals such as pulse rate, respiratory rate, heart rate, and body temperature can be confirmed on an external monitor device.

[0320] 13B is attached to the human body using adhesive pads or the like. Sensor 5900 acquires biometric information such as heart rate, electrocardiogram, etc. by transmitting signals to electrodes 5931 or the like attached to the human body via wiring 5932. The acquired information is transmitted as a wireless signal to a terminal such as a reader.

[0321] Note that this embodiment mode can be appropriately combined with other embodiment modes described in this specification. [Example]

[0322] <Calculations and results> In order to confirm whether minute currents are being measured appropriately in the configuration of circuit 20 shown in FIG. 1A, calculations were performed using a circuit simulator.

[0323] The software used in this calculation is a circuit simulator called SmartSpice (version 8.2.12.R) by Silvaco. Using this simulator, the output voltage V output from the output terminal OT relative to the current input to the first terminal of the transistor M1 was calculated. out Calculations were performed on the following.

[0324] First, the circuit configuration for performing this calculation will be described. Fig. 14A shows a circuit configuration input into a circuit simulator based on the circuit 20 shown in Fig. 1A. In addition to the circuit 20 in Fig. 1A, the circuit 20S has constant voltage sources VC1 and VC2 and a constant current source CC1.

[0325] The positive terminal of the constant voltage source VC1 is electrically connected to the high power supply potential input terminal DT of the operational amplifier OP1 and the negative terminal of the constant current source CC1, and the positive terminal of the constant current source CC1 is electrically connected to the first terminal and gate of the transistor M1 and the inverting input terminal of the operational amplifier OP1. The positive terminal of the constant voltage source VC2 is electrically connected to the non-inverting input terminal of the operational amplifier OP1. The line GNDL is electrically connected to the negative terminal of the constant voltage source VC1, the negative terminal of the constant voltage source VC2, and the low power supply potential input terminal ST of the operational amplifier OP1. In this calculation, the potential of the line GNDL is set to 0V.

[0326] The constant voltage source VC1 applies a voltage of 3.3 V between the positive and negative terminals, and the constant voltage source VC2 applies a voltage of 1.5 V between the positive and negative terminals. The constant current source CC1 supplies a current I to be input to the input terminal IT of the circuit 20S. in In this calculation, a current of 1zA to 1mA is input to the input terminal IT.

[0327] In addition, the conditions for this calculation were that the channel length of the transistor M1 was 0.36 μm, the channel width was 0.36 μm, and the threshold voltage was 0.83V.

[0328] Voltage V of circuit 20Sout and current I in In calculating the characteristics of the transistor M1, we will first explain the diode characteristics of the diode-connected transistor M1. Figure 14B shows only the diode-connected transistor M1 of Figure 14A. When the voltage applied to the gate is Vg (the voltage applied between the first and second terminals of the transistor M1 is Vd), the current Id flowing between the first and second terminals of the transistor M1 is calculated using a similar circuit simulator to obtain the result shown in Figure 15.

[0329] Next, in the circuit 20S, the current I input to the first terminal of the transistor M1 in The output voltage V output from the output terminal OT out The results of the calculations are shown in Figure 16.

[0330] From Figure 16, the current I from 1zA to around 1fA in When input to the input terminal IT, the output voltage V out It can be seen that the output voltage V is a constant voltage of approximately 1.5 V. This is because the differential voltage input to the operational amplifier OP1 is outside the operating range. out is saturated at approximately 1.5V and output. Therefore, the current I in In each case, different output voltages V out Therefore, the current I in It is not possible to measure the current I from 1zA to around 1fA. in Output voltage at V out The characteristic corresponds to the diode characteristic of the transistor M1 (FIG. 15) when the current Id is approximately 1 fA or less, and Vg of the transistor M1 is approximately 0V.

[0331] In addition, the current I in When input to the input terminal IT, the output voltage V out is output as approximately 0.6V, and then the current I in When increasing, the output voltage Vout decreases, and the output voltage V out becomes 0V. This current I in - Output voltage V out The characteristic corresponds to the diode characteristic of transistor M1 when the current Id is in the range of approximately 2 nA or more and 70 nA or less (Figure 15), and the slope of the diode characteristic of transistor M1 in this current range is gentler than in the range of 100 pA or more and less than 2 nA.

[0332] And, the current I is greater than about 70 nA. in When input to the input terminal IT, the output voltage V out is output as a constant voltage of approximately 0 V. On the other hand, in the diode characteristics of transistor M1 (FIG. 15), when a current Id of 70 nA or more flows, Vg of transistor M1 becomes approximately 1.5 V or more. However, in circuit 20S, the differential voltage input to operational amplifier OP1 is outside the operating range, so the output voltage V out is saturated to approximately 0V and output. Therefore, a current I larger than around 70nA in is input to the input terminal IT, Vg of the transistor M1 becomes a constant voltage of approximately 1.5V.

[0333] In Figure 16, the current I in The current-voltage characteristics for the expanded range of I are shown in Figure 17. in is in the range of 10fA to 1nA, the output voltage V out can be expressed as a linear equation with a negative slope. The range expressed by this linear equation is referred to here as the measurable range. This range corresponds to the range in which the current Id of the diode characteristics of the transistor M1 (FIG. 15) ranges from 10 fA to 1 nA. Therefore, by using the diode-connected transistor M1 as a diode element, the circuit 20S can measure the current Id from 10 fA to 1 nA. in can be measured.

[0334] Next, FIG. 18 shows the current-voltage characteristics of circuit 20S when the threshold voltage of transistor M1 is changed to the positive side and the negative side from 0.83V. The threshold voltage is changed according to conditions CN0 to CN11. Condition CN0 is the same condition as the current-voltage characteristics of circuit 20S shown in FIG. 16, and is the condition where the threshold voltage of transistor M1 is 0.83V. Conditions CN1 to CN7 are conditions where the threshold voltage of transistor M1 in condition CN0 is shifted to the negative side, and the shift amounts of the threshold voltages of the respective conditions are -0.4V, -0.8V, -1.2V, -1.6V, -2.0V, -2.4V, -2.8V. Also, each of conditions CN8 to CN11 is a condition where the threshold voltage of transistor M1 in condition CN0 is shifted to the positive side, and the shift amounts of the threshold voltages of the respective conditions are 0.4V, 0.8V, 1.2V, 1.6V.

[0335] When changing from condition CN0 to condition CN7 and lowering the threshold voltage of transistor M1 from 0V, in the region having the slope of the current-voltage characteristics, since the slope becomes steeper on the negative side, current I in 's measurable region becomes narrower.

[0336] [[ID=⑨]] On the other hand, when changing with condition CN0, conditions CN8 to CN11 and raising the threshold voltage of transistor M1 from 0V, the measurable region is in the range from around 100 aA to around 1 nA in condition CN8, in the range from around 1 aA to around 100 pA in condition CN9, and further in the range from around 1 zA to around 1 pA in condition CN10. From this, in circuit 20S, by shifting the threshold voltage of transistor M1 to the positive side, a smaller current can be measured.

Example

[0337] <High-temperature characteristics of CAAC-IGZO FET> It should be noted that there is a mislabeled "⑨" in the original text which is retained as is in the translation for consistency. Also, there is a mislabeled "□" which is also retained as is. If these are actual errors in the original, they should be corrected in the source material for a more accurate translation.A field-effect OS transistor (hereinafter referred to as a CAAC-IGZO FET) that can be provided in a semiconductor device according to one embodiment of the present invention has low temperature dependence and can operate stably even in a high-temperature environment. In this example, an experiment on the high-temperature characteristics of a CAAC-IGZO FET and the results thereof will be described.

[0338] CAAC-IGZO FETs can be fabricated in the BEOL (Back End Of Line) process of semiconductor manufacturing processes such as CMOS. This allows them to be stacked with Si transistors (field-effect Si transistors are also called "Si FETs"). For example, a circuit requiring high-speed operation can be fabricated using the CMOS process, while a circuit requiring low leakage current can be fabricated using the CAAC-IGZO process.

[0339] Furthermore, while the off-state current of a Si FET increases with increasing temperature, the off-state current of a CAAC-IGZO FET is always at the lower limit of measurement. Therefore, we compared the temperature characteristics of the off-state current of a Si FET with L (channel length) / W (channel width) = 60nm / 120nm and a CAAC-IGZO FET with L / W = 60nm / 60nm. The off-state current of both FETs was measured using the circuit shown in Figure 19.

[0340] The circuit shown in FIG. 19 includes a FET serving as a DUT (Device Under Test), a write transistor WFET, and a read circuit SF. The write transistor WFET is a CAAC-IGZO FET. The read circuit SF includes CAAC-IGZO FETs connected in series. Terminal S of the FET serving as the DUT functions as a terminal for inputting a source voltage. Note that the DUT in FIG. 19 is a CAAC-IGZO FET with a top gate TG and a back gate BG; this does not necessarily apply if the DUT is a Si FET.

[0341] In FIG. 19, when a Si FET is used as the DUT, the measurement conditions for the off-state current of the Si FET are a gate voltage V G= -1.0V, source voltage V S = 0V, drain voltage V D =1.2V, body voltage V B In addition, in Fig. 19, when a CAAC-IGZO FET is used as the DUT, the measurement conditions for the off-state current of the CAAC-IGZO FET are a gate voltage V G = -2.0V, source voltage V S = 0V, drain voltage V D = 2.0V, back gate voltage V BG =-3.0V.

[0342] The measurement results are shown in Figure 20. At a measurement temperature of 150°C, the off-current of the Si FET was approximately 2.2 × 10 -6 A, and the off-current of the CAAC-IGZO FET is approximately 3.9×10 -20 A. CAAC-IGZO FETs can maintain a low off-state current even in high-temperature environments. Furthermore, by adjusting the back gate voltage, it is possible to further reduce the off-state current.

[0343] Next, Figure 21 shows the temperature dependence of the Hall mobility and carrier density of the CAAC-IGZO film. Figure 21 shows that the Hall mobility of the CAAC-IGZO film changes almost unchanged with temperature. The Hall mobility of the CAAC-IGZO film does not decrease even at high temperatures, as it is assumed that Coulomb scattering is more dominant than phonon scattering.

[0344] Next, the cutoff frequencies f of the CAAC-IGZO FET and Si FET at 27°C and 150°C were measured. T The measurement DUTs were a Si FET with L / W = 60nm / 480nm and a CAAC-IGZO FET with L / W = 21nm / 25nm. The Si FET was measured by connecting 21 Si FETs in parallel (M = 21). The CAAC-IGZO FET was measured by connecting 672 CAAC-IGZO FETs in parallel (M = 672).

[0345] The measurement results are shown in Figure 22. The cutoff frequency fT The change rate from 27°C to 150°C was -36% for the cutoff frequency f of the CAAC-IGZO FET. T The change rate from 27°C to 150°C was +55% for the cutoff frequency f of the [FET name not clear in the original, seems like a different FET]. T Compared with the Si FET, the CAAC-IGZO FET has the characteristic that the cutoff frequency f at 27°C and the cutoff frequency f at 150°C do not decrease but increase. T Also, in the Si FET measured this time, the cutoff frequency at a measurement temperature of 150°C and VD = 1.2V was 88 GHz, while in the CAAC-IGZO FET, at a measurement temperature of 150°C and V D = 2.5V, the cutoff frequency f T was 51 GHz.

[0346] From these, it was found that the CAAC-IGZO FET has a mobility that does not decrease due to an increase in temperature of the cutoff frequency f compared to the Si FET. T Also, it was found that by providing a back gate electrode to the CAAC-IGZO FET, the variation in the threshold voltage due to temperature change can be suppressed. T Also, it was found that the amount of change in the cutoff frequency f of the CAAC-IGZO FET with respect to temperature change is lower than that of the Si FET. -20 Also, it was found that the off-current of the CAAC-IGZO FET is extremely small, at 10

Example

[0347] <Variation and reliability of the threshold voltage of the CAAC-IGZO FET> A CAAC-IGZO FET, which is a field-effect OS transistor that can be included in a semiconductor device according to one embodiment of the present invention, has a small variation in threshold voltage and a small change in threshold voltage due to degradation. Therefore, the CAAC-IGZO FET has high reliability. In this example, the results of investigating the degree of variation in threshold voltage of CAAC-IGZO FETs and the measurement results of the change in threshold voltage of CAAC-IGZO FETs in an accelerated test are described.

[0348] First, we will explain the investigation of the degree of variation in the threshold voltage of CAAC-IGZO FETs. The investigation method was to form 512 CAAC-IGZO FETs with L / W = 60 nm / 60 nm on the surface of a single wafer, and measure the gate-source voltage V GS and source-drain current I DS The characteristics of each CAAC-IGZO FET were measured, and the threshold voltage V th Here, the threshold voltage V th is the source-drain current I in the saturation region, assuming that the CAAC-IGZO FET conforms to the gradual channel approximation. DS From V th The gate-source voltage V GS and source-drain current I DS The measurement conditions for the characteristics are the source-drain voltage V of the CAAC-IGZO FET. DS =1.2V, back gate-source voltage V BS = 0V.

[0349] Figure 23 shows the threshold voltage V of 512 CAAC-IGZO FETs. th The calculation results also show that the threshold voltage V thThe average value μ of the threshold voltage was estimated to be 388 mV, and the standard deviation σ was estimated to be 76 mV. From these results, it was found that the CAAC-IGZO FET has a small variation in threshold voltage. In addition, because the variation in threshold voltage is small, the back gate-source voltage V BS By appropriately adjusting the threshold voltage, it is possible to adjust the threshold voltage to, for example, 0V.

[0350] Next, we will explain the measurement of the change in threshold voltage of CAAC-IGZO FET by accelerated testing. In this accelerated testing, the gate voltage V G = 3.63V, source voltage V S = 0V, drain voltage V D = 0V, back gate voltage V BS = 0V, the threshold voltage V of the CAAC-IGZO FET with L / W = 60 nm / 60 nm th In this accelerated test, the change in threshold voltage V th as well as the source-drain current I ds , S value (also called subthreshold swing, SS, etc.), field-effect mobility μ FE The S value is the minimum change in gate voltage required to change the drain current by one order of magnitude in the subthreshold region of a transistor, and the smaller the S value, the sharper the transistor's on / off switching operation can be.

[0351] In addition, in order to measure the physical properties and characteristics of each CAAC-IGZO FET, the source-drain voltage V DS =1.2V, back gate voltage V BS = 0V, the source-drain current I ds Also, the threshold voltage V th is the source-drain current I ds is 1.0×10 -12 A is the gate-source voltage.

[0352] 24A, 24B, 25A, and 25B show the threshold voltage V th , source-drain current I ds , S value, field effect mobility μ FE The results shown in Figure 24A show that the change in threshold voltage |ΔV th 24B, 25A, and 25B, the source-drain current I ds , S value, field effect mobility μ FE The amount of change in each of these was also found to be small, as in FIG. 24A.

[0353] From the above, it was found that the variation in threshold voltage of CAAC-IGZO FETs is small when multiple CAAC-IGZO FETs are simultaneously formed on a single wafer. Therefore, the use of CAAC-IGZO FETs can increase the yield of circuits, semiconductor devices, electronic devices, etc. Furthermore, CAAC-IGZO FETs have low threshold voltage and source-drain current I ds , S value, field effect mobility μ FE These results suggest that the use of CAAC-IGZO FETs can lead to the creation of highly reliable circuits, semiconductor devices, and electronic devices.

[0354] This embodiment can be appropriately combined with each embodiment mode described in this specification. [Explanation of symbols]

[0355] M1: transistor, DE: diode element, C1: capacitance element, OP1: operational amplifier, OSC: circuit, CE: circuit, IT: input terminal, OT: output terminal, DT: high power supply potential input terminal, ST: low power supply potential input terminal, GNDL: wiring, VC1: constant voltage source, VC2: constant voltage source, CC1: constant current source, IVC1a: characteristics, IVC1b: characteristics, IVC2: characteristics, TG: top gate, BG: back gate, S: terminal, WFET: write transistor, SF: read circuit, 10: circuit, 20: circuit, 20A: circuit, 20S: circuit, 21: circuit, 21A: circuit, 21 B: Circuit, 21C: Circuit, 21D: Circuit, 21E: Circuit, 30: Detection unit, 40: Processing unit, 50: Memory unit, 60: Display unit, 70: Power supply circuit, 90: Object to be detected, 300: Transistor, 311: Substrate, 313: Semiconductor region, 314a: Low resistance region, 314b: Low resistance region, 315: Insulator, 316: Conductor, 320: Insulator, 322: Insulator, 324: Insulator, 326: Insulator, 328: Conductor, 330: Conductor, 350: Insulator, 352: Insulator, 354: Insulator, 356: Conductor, 360: Insulator, 362: Insulator, 364: Insulator, 366: Conductor, 370: insulator, 372: insulator, 374: insulator, 376: conductor, 380: insulator, 382: insulator, 384: insulator, 386: conductor, 500: transistor, 503: conductor, 503a: conductor, 503b: conductor, 505: conductor, 510: insulator, 512: insulator, 514: insulator, 516: insulator, 518: conductor, 520: insulator, 522: insulator, 524: insulator, 530: oxide, 530a: oxide, 530b: oxide, 530c: oxide, 540: conductor, 540a: conductor, 540b: conductor, 542a: conductor, 542b: conductor conductor, 543a: region, 543b: region, 544: insulator, 546: conductor, 548: conductor, 550: insulator, 560: conductor, 560a: conductor, 560b: conductor, 574: insulator, 580: insulator, 581: insulator, 582: insulator, 586: insulator, 600: capacitance element, 600A: capacitance element, 600B: capacitance element, 610: conductor, 611: conductor, 612: conductor, 620: conductor, 630: insulator, 631: insulator, 640: insulator, 650: insulator, 651: insulator, 4700: electronic component, 4701: lead, 4702: printed circuit board,4704: Mounting board, 4710: Semiconductor device, 4730: Electronic component, 4731: Interposer, 4732: Package substrate, 4733: Electrode, 4735: Semiconductor device, 4800: Semiconductor wafer, 4800a: Chip, 4801: Wafer, 4801a: Wafer, 4802: Circuit section, 4803: Spacing, 4803a: Spacing, 5300: ICD body, 5301a: Battery, 5301b: Battery, 5302: Wire, 5303: Wire, 5304: Antenna, 5305: Subclavian vein, 5306: Superior vena cava, 5900: Sensor, 5931: Electrode, 5932: Wiring, 6140: Robot, 6141a: Contact sensor, 6141b: Contact sensor, 6141c: Contact sensor, 6141d: Contact sensor, 614 1e: contact sensor, 6150: industrial robot, 6151: functional part, 6152: control part, 6153: drive shaft, 6154: drive shaft, 6155: drive shaft, 6240: digital camera, 6241: housing, 6242: display part, 6243: operation button, 6244: shutter button, 6246: lens, 6300: video camera, 6301: first housing, 6302: second housing Housing, 6303: display unit, 6304: operation keys, 6305: lens, 6306: connection unit, 6900: alarm, 6901: sensor, 6902: receiver, 6903: transmitter, 6904: sensor circuit, 6905: window, 6906: operation keys, 6907: display unit, 6908: operation keys, 6909: operation keys, 6910: wiring, 6911: speaker, 6912: lighting device,

Claims

[Claim 1] a first transistor, a second transistor, and an operational amplifier; an inverting input terminal of the operational amplifier directly connected to the first terminal and the gate of the first transistor; a second terminal of the first transistor directly connected to a first terminal of the second transistor; a gate of the second transistor is directly connected to the inverting input terminal of the operational amplifier; the output terminal of the operational amplifier is directly connected to the second terminal of the second transistor; the operational amplifier is a unipolar circuit using a transistor having a metal oxide in a channel formation region, the first and second transistors each have a metal oxide in a channel formation region; the first and second transistors have back gates; A potential that shifts the threshold voltages of the first and second transistors to the positive side is input to the back gate, thereby increasing the off-state current of the first and second transistors by 1.0×10 －１５ A semiconductor device having a function of reducing the temperature to A or less.

Images