Electrochemical device with variable conductance

Abstract

An electrochemical device includes an electrochemical cell and an electrical circuit. The electrochemical cell includes a first solid component and a second solid component. The two solid components contain the same chemical elements, but differ in the concentration of at least one type of chemical element. A solid electrolyte is disposed between the two solid components. The solid electrolyte is a dielectric material. The electrical circuit is connected to the electrochemical cell. The electrochemical cell can operate according to a redox process to exchange at least one type of chemical element between the first solid component and the second solid component, thereby changing the electrical conductance of each of the two solid components.

Description

Technical Field

[0001] The present invention generally relates to the field of electrochemical devices having solid electrolytes. In particular, the present invention relates to electrochemical devices that include circuitry for varying the conductance of a solid component of the device. Electrochemical devices according to various embodiments can be advantageously used, for example, as synaptic elements in neuromorphic hardware devices. The present invention also relates to methods of operating electrochemical devices. Background Art

[0002] Machine learning often relies on artificial neural networks (ANNs), computational models inspired by biological neural networks in the human or animal brain. An ANN consists of a set of connected units or nodes, called artificial neurons. Signals are transmitted along the connections (also called edges) between artificial neurons, similar to synapses. That is, the artificial neuron that receives a signal processes it and then signals the connected neuron. Connection weights (also called synaptic weights) are associated with connections and nodes. Each neuron can have several inputs, and a connection weight is assigned to each input (the weight of that particular connection). These weights adjust as learning progresses.

[0003] Neural networks are typically implemented in software. However, neural networks can also be implemented in hardware, for example, as resistive processing units (relying on a crossbar array structure) or optical neuromorphic systems. That is, a hardware-implemented ANN is a physical machine that is significantly different from a classical computer (general-purpose or special-purpose) because it is primarily and specifically designed to implement ANNs (for training and / or inference purposes). The synaptic elements used in neuromorphic hardware devices typically include memristive devices, such as phase-change memory devices, resistive random access memory (RRAM), or magnetic random access memory (SRAM).

[0004] In addition to neuromorphic hardware devices, various electrochemical devices are known. An electrochemical cell is a device configured to generate electrical energy from a chemical reaction or, conversely, to utilize electrical energy to induce some chemical reaction. Solid-state electrochemical capacitors, as well as computer storage elements based on such capacitors, in particular electrochemical random access memory (ECRAM) devices, have been proposed, see, for example, Sharbati, Mohammad Taghi et al., “Artificial synapses: low-power electrochemically tunable graphene synapses for neuromorphic computing (Adv. Mater. 36 / 2018)”, Advanced Materials 30.36 (2018): 1870273, and J. Tang et al., “ECRAM as a scalable synaptic cell for high-speed, low-power neuromorphic computing”, IEDM, p. 13.1.1, 2018. Summary of the Invention

[0005] In various embodiments, an electrochemical device includes an electrochemical cell. The electrochemical cell may include a first solid component and a second solid component. Additionally, the electrochemical cell may include a first solid electrolyte and an electrical circuit. The first solid component may be composed of one or more specific chemical elements, wherein a first chemical element of the one or more specific chemical elements is present in the first solid component at a first concentration. The second solid component may be composed of the same one or more specific chemical elements, however, the first chemical element of the one or more specific chemical elements is present in the second solid component at a second concentration, and the first and second concentrations are different. The first solid electrolyte may be disposed or arranged between the first and second solid components. The first solid electrolyte is a dielectric material. The electrical circuit is coupled to the electrochemical cell and configured to operate the electrochemical cell according to a redox process in which the first chemical element is exchanged between the first and second solid components. This exchange changes the electrical conductance of each of the first and second solid components.

[0006] According to a first aspect, the present invention is embodied as an electrochemical device. The device includes an electrochemical cell and an electrical circuit. The electrochemical cell includes two solid components, namely a first solid component and a second solid component. The two solid components contain the same chemical elements, but the concentration of at least one type of chemical element in the chemical elements differs. Each of the first solid component and the second solid component can be formed as a material layer, for example. A solid electrolyte is provided between the two solid components. The solid electrolyte is a dielectric material. The electrical circuit is connected to the electrochemical cell. It is typically configured to operate the cell according to a redox process so that during operation, the at least one type of chemical element is exchanged between the first solid component and the second solid component, thereby changing the electrical conductance of each of the two solid components.

[0007] Thus, the solid components have a symmetrical composition; they act as cathode and anode. Since they differ in the concentration of one or more chemical elements that they have in common, one of the solid components can be converted into the other by a redox process, one of the solid components being the reduced form of the other. The operation of the device is very simple and can be exploited to read out the conductance (or resistance, or a change in such conductance or resistance) in the second solid component. The use of solid components makes the above-mentioned device very suitable for integration into hardware. In particular, such a device can be used as a synaptic element in a neuromorphic circuit to process cognitive workloads. The electrochemical principle utilized makes the device a non-volatile device, which can be advantageously used to store and modify the weights of the synaptic elements of neuromorphic hardware.

[0008] In an embodiment, the two solid components each contain a compound of at least two chemical elements and have a different concentration of one of the at least two chemical elements.

[0009] Preferably, in operation of the device, each of the two solid components comprises WO3, although one component is a reduced form of the other.

[0010] In a preferred embodiment, the solid electrolyte comprises a high-κ dielectric material. The solid electrolyte may, for example, comprise HfO2, through which intercalated ions are exchanged between the two solid components in operation.

[0011] In an embodiment, the circuit includes two circuits, namely a first circuit and a second circuit. The first circuit connects the first solid-state component to the second solid-state component so that, during operation, the primitive operates according to the redox process. The second circuit is closed by the second solid-state component. The second circuit is configured to sense an electrical signal affected by a change in conductance occurring in the second solid-state component during operation of the device.

[0012] Preferably, the electrochemical cell further comprises three electrical contacts, the latter consisting of a source contact, a drain contact, and a gate contact. Each of the source contact and the drain contact is in electrical communication with the second solid component, while the gate contact is in electrical communication with the first solid component. A first circuit is connected to each of the source contact and the gate contact. A second circuit is connected to the source contact and the drain contact. For example, the electrochemical cell can be configured as a three-terminal device having three electrical contacts, the three electrical contacts consisting of the source contact, the drain contact, and the gate contact.

[0013] Preferably, the device further comprises a substrate, a second solid component extending on top of the substrate, the source contact and the drain contact each being electrically connected to the second solid component, the solid electrolyte extending on top of and in contact with the second solid component, the first solid component extending on top of and in contact with the solid electrolyte, and the gate contact disposed on top of and in contact with the first solid component.

[0014] In an embodiment, each of the source contact and the drain contact is arranged on top of the second solid component, in contact therewith, and the solid electrolyte extends between the source contact and the drain contact.

[0015] In some embodiments, the substrate comprises a doped substrate. In a variant, an insulating (or semiconductor) substrate is used. In a preferred embodiment, the circuit further comprises a third circuit that grounds the doped substrate.

[0016] Preferably, the cell further comprises a third solid component extending between the doped substrate and the second solid component. The third solid component comprises the same chemical element as the first and second solid components, but has a different concentration of the at least one type of the chemical element compared to the second solid component. The solid electrolyte is a first solid electrolyte, and the second solid electrolyte extends between the third and second solid components so as to contact the third and second solid components.

[0017] In an embodiment, the circuit further comprises a third circuit connected to the first circuit so as to connect the doped substrate to the first circuit.

[0018] The second solid component can be configured as a fin. In this case, the source contact and the drain contact each extend on top of the substrate so as to laterally contact the fin at each end. In addition, the gate contact, the solid electrolyte, and the first solid component are at least partially wrapped around the fin, for example, to form a wraparound structure.

[0019] In a preferred embodiment, the device comprises a plurality of wrapping structures arranged along the fin and separated from each other. Each wrapping structure is constructed similarly to the wrapping structure described above so as to at least partially wrap around the fin.

[0020] According to another aspect, the present invention is embodied in an apparatus comprising a plurality of electrochemical devices as described above. The apparatus further comprises a controller connected to the circuitry of the devices to operate the devices according to a redox process. Furthermore, a readout circuit is connected to the circuitry of the devices. The readout circuit is configured to sense an electrical signal influenced by the conductance of one or more second solid components of the electrochemical devices during operation. The apparatus is preferably configured as artificial neural network hardware, wherein each device is configured as a synaptic element of the artificial neural network hardware.

[0021] According to a final aspect, the present invention is embodied in a method for operating an electrochemical device. The method relies on an apparatus such as that described above, i.e., comprising an electrochemical cell comprising two solid components, i.e., a first solid component and a second solid component. The two solid components contain the same chemical element, but have different concentrations of at least one type of said chemical element. The device also includes a solid electrolyte arranged between the two solid components, wherein the solid electrolyte is a dielectric material. Finally, the device also includes an electrical circuit connected to the electrochemical cell. According to the method, the circuit is used to operate the electrochemical cell according to a redox process so as to exchange the at least one type of chemical element between the first solid component and the second solid component, thereby changing the conductivity of each of the two solid components, and sensing an electrical signal affected by the conductivity of the second solid component.

[0022] Devices, apparatus and methods embodying the invention will now be described by way of non-limiting examples and with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are used to further illustrate various embodiments and explain various principles and advantages according to the present disclosure. In the accompanying drawings, like reference numerals refer to the same or functionally similar elements throughout the various views, and the accompanying drawings are incorporated into and form a part of this specification together with the following detailed description. In the accompanying drawings:

[0024] Figures 1 to 3 is a two-dimensional cross-sectional view of an electrochemical device according to an embodiment of the present invention;

[0025] Figure 4 is a three-dimensional view of an electrochemical device according to another embodiment;

[0026] Figure 5 is a 3-dimensional diagram of a neuromorphic device including a crossbar array structure according to an embodiment, whose input and output lines are connected via channels such as Figure 4 The electrochemical devices depicted in are interconnected at junctions; and

[0027] Figure 6 is a flow chart illustrating high-level steps of a method of operating an electrochemical device according to an embodiment.

[0028] The accompanying drawings show simplified representations of devices or components thereof as described in the embodiments. The technical features depicted in the accompanying drawings are not necessarily drawn to scale. Unless otherwise indicated, similar or functionally similar elements in the figures are assigned the same reference numerals. DETAILED DESCRIPTION

[0029] Electrochemical devices have been proposed as alternatives to conventional memristive devices for synaptic elements in neuromorphic hardware. Such devices typically have low power budgets. However, difficulties arise from their scalability, lack of CMOS compatibility, and enabling control of the stoichiometry of the reservoir (the reservoir is the component that can provide or store the active ions that activate the ECRAM function as a result of a chemical reaction activated by an electrical stimulus). Furthermore, these devices typically rely on liquid electrolytes or organic solid electrolytes, making them unsuitable for integration into neuromorphic hardware.

[0030] In order to develop suitable electrochemical devices for integration in neuromorphic hardware, the inventors of the present invention set out to develop various devices that could be satisfactorily used in neuromorphic hardware. Such solutions are described in detail in the following description.

[0031] Reference Figure 1-4First, one aspect of the present invention is described, which relates to electrochemical devices 1-4, which include electrochemical cells 30, 31, 32, and 33 respectively. Figure 5 The illustrated electrochemical devices 1-3 and apparatus 100 include circuits 110-150, which typically include several circuit sections having different functions.

[0032] Electrochemical cells 30, 31, 32, 33 include two solid components 11, 12: a first solid component 11 and a second solid component 12. These two solid components 11, 12 may include the same chemical element, although one or more chemical elements may be present in different concentrations in solid components 11, 12. For example, a particular chemical element may be present in solid component 11 at a first concentration, and the same particular chemical element may be present in solid component 12 at a second concentration, where the first and second concentrations are different. Thus, components 11, 12 may have different concentrations of at least one type of chemical element that they share. This may result in a low open-circuit voltage during operation. For example, components 11, 12 may include binary compounds that differ in the concentration of one element.

[0033] The electrochemical cells 30, 31, 32, 33 may also include a solid electrolyte 14 arranged between the two solid components 11, 12. This solid electrolyte is a dielectric material. The solid electrolyte 14 may, for example, comprise a high-κ dielectric material, such as HfO2 (hafnium(IV) oxide), in which oxygen ions serve as intercalating ions, i.e., ions that move between the components 11 and 12. (The κ in "high-κ" refers to the dielectric constant.) These ions pass through the electrolyte 14, which acts as an ionic conductor but does not conduct electronic current. The use of oxygen as an intercalating ion makes it possible to avoid some of the problems caused by the use of lithium-based devices, as most commonly reported in the literature (safety drawbacks, energy density, etc.).

[0034] Circuits 110 and 140 are connected to electrochemical elements 30, 31, and 32. Circuit 150 is connected to the electrochemical elements of device 100. The circuits are typically configured to operate the elements according to a redox process. The redox process can be chemical (e.g., in a hydrogen atmosphere) or electrochemical (e.g., by applying a negative / positive bias). This allows, during operation of the device, the exchange of the at least one type of chemical element between first solid component 11 and second solid component 12. This exchange, in turn, causes a change in the electrical conductance of each of the two solid components 11, 12.

[0035] Thus, solid components 11 and 12 function as cathodes and anodes. Because they differ in the concentration of one or more chemical elements they share, during operation of devices 1-4, one solid component can be converted into the other through a redox process. That is, during operation, one solid component is a reduced form of the other. As discussed later in the embodiments, this can be exploited to read the conductance (or resistance, or changes in such conductance or resistance) of the second solid component.

[0036] Devices 1-4 can be manufactured as multilayer devices, see e.g. Figure 1-4 The solid electrolyte 14 and the solid components 11 , 12 of the electrochemical cells 30 , 31 , 32 , 33 can, for example, be formed as material layers, possibly structured. The use of solid components makes the device suitable for integration into hardware. In particular, such a device can be used as a synaptic element in neuromorphic circuits to process cognitive workloads. The electrochemical principles utilized make the device a non-volatile device, which can be advantageously used to store and modify the weights of synaptic elements of neuromorphic hardware.

[0037] All of this will now be described in detail with reference to a specific embodiment of the present invention. First, the two solid components 11, 12 preferably each include a compound of at least two chemical elements and have different concentrations of one of the at least two chemical elements. For example, the solid components 11, 12 may include exactly two elements. For example, they may include WO3 (tungsten trioxide). The use of a symmetrical, WO3-based solid component makes the device compatible with CMOS, and the device can be integrated in the back-end of line (BEOL) of a CMOS process. Incidentally, when using a high-κ dielectric material such as HfO2, the use of a WO3-based solid component is particularly advantageous because HfO2 is a good ion conductor (rather than an electron conductor), allowing oxygen ions to be properly (de-)intercalated between the two solid components of WO3.

[0038] In various embodiments, other materials may be considered for the solid components 11, 12 and the solid electrolyte 14. For example, the solid components 11, 12 may each comprise strontium titanate (SrTiO3, or STO for short). In a variant, they may comprise, for example, perovskites (SrFeOx, SrCoO x ,CaCrO x ), solid solution: BaInO x -BaZrO x 、SrTiO x -SrCoO x , other oxides (La2NiO4, La2CuO4) or non-oxygen compounds (such as Li x CoO2 and Na xFurthermore, the solid electrolyte 14 may comprise, for example, Ta2O5, or yttrium-doped zirconium oxide (Y:ZrO2 or YZO), or CeO2, or a non-oxide oxygen electrolyte (LaF3), or any other electrolyte suitable for (de)intercalation of species.

[0039] In e.g. Figure 1-3 In the embodiment depicted in FIG, the circuit of the device 1-3 is broken down into two distinct (albeit connected) circuits (or circuit portions), namely a first circuit 110 and a second circuit 120. The first circuit 110 connects the first solid component 11 to the second solid component 12 via contacts 21. The circuit 110 is generally designed to allow the primitives 30, 31, 32 to operate according to the redox process as described above. The first circuit 110 generally includes a voltage source or a current source to drive the redox process, as assumed in the drawings. A current source is preferred because it makes it easier to measure the ionic charge moving during the redox process.

[0040] The second circuit 120 is provided for sensing some electrical signal affected by changes in conductance during operation of the devices 1-4, which changes in conductance occur significantly in the second solid-state component 12. Note that the second circuit 120 is closed by the second solid-state component 12 (also referred to as the "channel" in this document) and is therefore affected by the electrical properties of the second solid-state component 12. The second circuit 120 can, for example, be designed to sense current and thereby read, for example, the resistance or conductance of the second solid-state component 12. The change in the conductance of the channel 12 is due to ions entering or leaving the channel 12 due to redox processes; it can be considered a non-volatile change in the conductivity of the channel.

[0041] like Figure 1-4 As shown, the electrochemical cells 30, 31, 32, 33 preferably include three electrical contacts, namely a source contact 21, a drain contact 23, and a gate contact 22. The source contact 21 and the drain contact 23 are each in electrical communication with the second solid component 12, while the gate contact 22 is in electrical communication with the first solid component 11. As shown, a first circuit 110 is connected to each of the source contact 21 and the gate contact 22, while a second circuit 120 is connected to the source contact 21 and the drain contact 23.

[0042] As such, devices 1-4 can be considered FET-like devices (i.e., devices similar to field effect transistors) because the flow of current can be controlled by applying a voltage to the gate, which can be provided by the first circuit 110, which in turn changes the conductivity between the drain and source, as measured by the second circuit 120. In particular, the electrochemical cells 30, 31, 32, 33 can be configured as three-terminal devices 1-4, i.e., devices having three electrical contacts consisting of a source contact 21, a drain contact 23, and a gate contact 22.

[0043] exist Figure 1 In the example of FIG, the device includes only three electrical contacts 21-23, and the substrate 10 is electrically insulating. In this case, in order to prevent the reading current from passing through the substrate when reading the channel 12, the substrate must be truly insulating. However, it is noted that the substrate 10 may include or may be an undoped semiconductor material, such as silicon.

[0044] like Figure 1-4 As shown, devices 1-4 can basically have a layer structure. For example, each of the first solid component 11 and the second solid component 12 can be formed as a material layer. Similarly, the solid electrolyte 14 can also be formed as a material layer, although the solid electrolyte 14 is preferably constructed (for example, to present a raised edge, as shown in the figure) to avoid short circuits between the source contact 21 or the drain contact 23 and the first solid component 11.

[0045] Device 1-3 is preferably constructed as follows. A second solid component 12 extends on top of the substrate 10, with a source contact 21 and a drain contact 23 electrically connected to the second solid component 12, respectively. In addition, a solid electrolyte 14 extends on top of the second solid component 12 so as to be in contact with the latter. Next, the first solid component 11 extends on top of the solid electrolyte 14, in contact with it. Finally, a gate contact 22 is arranged on top of the first solid component 11, in contact with the element 11. Note that "on top" means "above, and in contact with it or at a distance from it". That is, an intermediate layer of additional material may be required, as long as they do not significantly change the desired electrical path. "Above" is in the z direction.

[0046] exist Figure 1-3 In the example structure shown, each of the source contact 21 and the drain contact 23 is arranged on top of the second solid component 12, in contact therewith. In addition, the solid electrolyte 14 extends between the source contact 21 and the drain contact 23. Note that for compactness or occupied area, the source 21 and the drain contact 23 may be in direct contact with the solid electrolyte 14 laterally, as shown in FIG. Figure 1-3 As assumed in .

[0047] exist Figure 2 and 3 In the example, with Figure 1 Instead, substrate 10a comprises doped material due to the additional contacts to the substrate.In fact, substrate 10 may for example comprise a doped region implanted for isolation from ground, similar to an implanted n-well in p-type silicon of a typical MOSFET circuit.

[0048] exist Figure 2In the example of , the entire circuit also includes a third circuit portion 130 that connects the doped substrate 10a to the ground. Note that despite the additional contacts, the device 2 can still be considered a FET-type device. The additional contacts on the doped substrate and the third circuit 130 are used to dynamically control the FET. This circuit 130 allows, together with the top contact 22, ions to be inserted into the layer 12 or, conversely, to be extracted from this layer 12. The circuit 130 plays the role of a volatile field effect. Thus, in this case, two effects are obtained in the same device 2. The first effect is a non-volatile effect obtained from electrochemical operation by the circuit 110, while the second effect obtained by the circuit 130 is volatile. In other words, the circuit 130 allows a potential to be applied to the substrate 10a relative to the ground, so that the substrate acts as a gate.

[0049] In addition, Figure 2 and Figure 3 In the embodiment of the present invention, another dielectric layer 16 extends on top of the doped substrate 10a, ie between the second solid component 12 and the substrate 10a. This layer 16 may, for example, comprise HfO2, just like the solid electrolyte 14, or any other dielectric material, such as Ta2O5 or YZO.

[0050] exist Figure 3 In the example shown, element 32 further includes a third solid component 13 extending between doped substrate 10a and second solid component 12. Third solid component 13 comprises the same chemical elements as first solid component 11 and second solid component 12. However, third solid component 13 will have a different concentration of one or more chemical elements common to layers 11-13, at least when compared to second solid component 12. As previously described, the concentration difference may involve only one element. Furthermore, the initial concentration of that element can be the same, for example, in first and third solid components 13 to achieve a symmetrical ion exchange layer structure.

[0051] In this example, the element 32 also includes a second solid electrolyte 16. That is, two solid electrolytes are provided in this case. The solid electrolyte 16 extends between the third solid component 13 and the second solid component 12. The second electrolyte 16 is in contact with each of the lower layer (the third solid component 13) and the upper layer (the second solid component 12).

[0052] Preferably, the circuit of the device 3 further comprises a third circuit 140. However, Figure 2 In contrast to the circuit 130, the circuit 140 is connected to the first circuit 110 to connect the doped substrate 10a to the first circuit 110. Similarly, the third circuit 140 may include a voltage source or a current source, such as Figure 3 Device 3 can be considered as a four-terminal dual-gate device (with a symmetrical ion exchange layer structure).

[0053] Circuit 140 is intended to use two gates, namely top gate (based on circuit 110, such as Figure 1 This feature provides more flexibility in operating an artificial synapse comprising device 3, for example. That is, the third circuit 140 can provide another pulse source (e.g., current or voltage pulses) similar to circuit 110. The overall synaptic response can, for example, result from a dual redox process occurring in channel 12, which is due to the first gate, the second gate, or a combination of the effects of both gates. In other words, as Figure 3 The structure shown provides another way to increase the active portion of the channel material, which changes the conductance of the channel 12, similar to FinFETs where multiple interfaces between the gate and the channel can be used for de-insertion purposes. However, circuit 140 is optional.

[0054] Figure 4 The illustrated embodiment includes an alternative structure in which the second solid component 12 is configured as a fin. In addition, the source contact 21 and the drain contact 23 each extend on top of the substrate 10 so as to laterally contact the fin 12 at each end thereof. In addition, the solid electrolyte 14, the first solid component 11 and the gate contact 22 are at least partially wrapped around the fin 12 as a continuous layer 14, 11, 22 (in that order). Therefore, the encapsulating structure formed by the gate contact 22, the solid electrolyte 14 and the first solid component 11 may be formed on two or more sides thereof (for example, on three sides, assuming the fin has a rectangular cross-section, as shown in FIG. Figure 4 ) contact fin 12. This structure can be considered as a FinFET-like device 4 with multiple ion exchange layers, which again allows more flexibility in the operation of the device in a compact and easily manufactured manner (compared to Figure 1 ).

[0055] In this example, the substrate is also insulating, at least if only two elements 11, 12 are used, separated by the dielectric 14. When additional circuitry is present, in order to obtain multiple gates (from top and bottom, or when using FET functionality), a doped substrate is required.

[0056] However, it is noted that the device 4 may optionally include several packaging structures (not shown for clarity of description), each packaging structure being similar to the above-mentioned Figure 4 The wrapping structures shown, i.e., the successive layers 14, 11 and 22, are wrapped around the fin and are shaped complementarily to the fin. That is, each resulting wrapping structure is similar to Figure 4 The single wrapping structure shown is similarly configured so as to at least partially wrap around the fin 12. A plurality of wrapping structures are arranged along the fin 12, albeit laterally separated from one another.

[0057] The structure comprising multiple wrapping structures as described above makes it possible to obtain multiple gates separated from each other. The use of several gates allows for higher density to be achieved because it enables individual fins 12 to operate in parallel. In particular, when the device 4 is used in a neuromorphic device, this can be used to increase the adjustability of the synaptic weight. In this case, the weight is captured by the resistance or conductance value of the channel 12. The artificial synapse carries the weight of the input stimulus arriving from the connection node and therefore changes the way the signal is processed / propagated further along the node. The weight value affects the current read at the output, as explained later with reference to the second aspect of the invention.

[0058] Can be combined with reference Figure 1-4 Many of the features described. For example, embodiments may relate to electrochemical devices in which the top and bottom layers (i.e., the solid components 11, 12 forming the anode and cathode) are composed of the same chemical elements (e.g., "A" and "X" for a binary compound), but one of the elements (e.g., "X") differs in concentration, resulting in a low open circuit voltage. This distinguishes electrochemical devices from solid-state batteries and solid oxide fuel cells because this feature results in a low cell voltage, which is undesirable for batteries but desirable for devices such as synaptic devices. As previously described, one compound (solid component 11) can be converted into another compound (solid component 12) through a redox process. A first circuit 110 is formed between a contact on the top layer and a contact on the bottom layer, while a second circuit 120 is formed between contacts on the same bottom layer. In contrast to conventional field-effect devices, an element of variable concentration ("X") is exchanged between the layers corresponding to the solid components 11 and 12 via the solid electrolyte 14 by an electrical signal applied via the first circuit 110. The conductivity of the bottom layer changes as a function of the concentration of the variable concentration element ("X") therein. For example, the device can be constructed as a 3-terminal device using decoupled programming and reading operations. The solid component 11 (which can be considered as a reservoir) and the channel 12 can advantageously comprise WO3, wherein the composition of one of the components 11, 12 is a reduced form of the other. Finally, the solid electrolyte preferably comprises HfO2. During the deposition process, H + / Ar reduction treatment to control and adjust the initial WO x For the rest, conventional photolithography processes can be used to fabricate the device.

[0059] refer to Figure 5 , another aspect of the present invention will now be described, which relates to the apparatus 100 .

[0060] like Figure 5 As shown, the device 100 includes a plurality of electrochemical devices 4 as described above. In addition, the device includes a controller 170 (ie, a programming circuit) that is connected to the circuits of the electrochemical devices 4 (eg, Figure 1-3The circuit portion 110 shown is connected to operate the device 4 according to the redox process, as previously described. Note that for clarity of description, the electrical connections between the controller 170 and the various devices 4 are now shown.

[0061] Furthermore, readout circuitry 160 is provided, which is again connected to the circuitry of the device 4 (e.g. Figure 1-3 120). Readout circuitry 160 is configured to sense one or more electrical signals affected by the conductance of the channel. In operation, the channel is formed by the second solid component 12 of the one or more electrochemical devices 4. Additional components such as input circuitry 150 and a processing unit may be required for reasons that will become apparent later.

[0062] Note that in Figure 5 , input circuitry 150, readout circuitry 160 and controller 170 typically form part of the same processing core, together with the connection structure formed by electrical conductors 155 and 165. However, in variations, components 150, 160 and 170 may be provided on separate chips, for example.

[0063] The device 100 may be particularly configured as a neuromorphic device, such as Figure 5 As assumed in . Each device 4 may form part of a corresponding synaptic element. Note that each device 4 may include several wrapping structures, as previously described with respect to Figure 5 As described, while still functioning as a single synaptic element 4. Each structure may include a solid electrolyte 14, a first solid component 11, and a gate contact 22 at least partially wrapped around the fin 12. Each of these wrapping structures may be spaced or separated from each other along the fin 12, such as Figure 5 This embodiment can be compared, for example, to PCM synaptic elements, where multiple PCM devices are used to provide the overall response of each synaptic element. The advantage of using multiple wrapping structures for each individual synaptic element is that it increases the tunability of the overall resistance / conductance of the channel of each synaptic device.

[0064] exist Figure 5 In the example shown, device 100 includes a crossbar array structure formed by N input lines 155 and M output lines 165. For illustrative purposes, only five input lines and five output lines are depicted in this example. However, in practice, hundreds of input lines may be involved. Similarly, hundreds of output lines may be required. The input and output lines are interconnected at the junctions by N×M electronic devices, each of which includes an electrochemical device 4 as described above.

[0065] The controller 170 may advantageously be connected to Figure 1-3The analog circuit of the first circuit 110 is shown. The controller is used to program the devices 4 so that they store values, or more precisely, have properties (e.g., conductance) that can be interpreted as such values. The devices 4 can be programmed to store synaptic weights accordingly.

[0066] Different analog circuits 150 may be used, for example, to couple an input signal (eg, apply a voltage bias) into an input line 155, such as Figure 5 As shown in .

[0067] The readout circuit 160 is configured to read out M output signals (e.g., currents) obtained from the M output lines 165. The readout is typically performed according to a multiply-accumulate operation that takes into account the signal (e.g., current or voltage bias) coupled to each of the input lines 155. According to the multiply-accumulate operation performed, the value stored on each electrochemical device 4 affects the readout. The multiply-accumulate operation typically results in the signal coupled to the input line being multiplied by the value stored at the junction on the device 4.

[0068] Notice, Figure 5 The architecture shown corresponds to a single layer of nodes of an ANN, rather than a multi-layer network. In principle, the architecture can be extended (or stacked) to implement several connected layers (thus being able to represent a multi-layer network), or connected to a core-to-core communication bus that may include digital processing units. Figure 5 Note that each or any of the circuits 150-170 may also be embodied as a digital processing unit, provided appropriate converters are provided to convert the signals (although for efficiency reasons analog circuits are preferably relied upon).

[0069] For inference purposes, the weights stored on the device 4 are constant (they benefit from the stability of the electrochemical device 4), whereas for learning purposes they need to be repeatedly reprogrammed. The calculations for weight updates are typically performed by a processing unit, and the crossbar array structure is used to perform all the basic operations required by the ANN (i.e., matrix-vector products for forward evaluation, products of the transposed matrix and the error gradient vector for backward evaluation, and vector outer products for updating weights), which involve large vector-matrix multiplications. For the learning phase, the analog circuit 170 can be used to reprogram the device 4 so as to change the synaptic weights stored thereon, and this is according to any suitable automatic learning process. However, such as Figure 5 The illustrated structure or neuromorphic device 100 can be used for both learning and inference purposes.

[0070] See also Figure 6, a final aspect of the invention will now be described, which relates to a method of operating an electrochemical device 1-4, or, by extension, to a method as previously described with reference to Figure 1-5 The basic aspects of the method have been described with reference to the devices and apparatus of the present invention. Therefore, only a brief description of the method will be given below.

[0071] In S10, an electrochemical device 1-4 as described above is provided. That is, a device 1-4 is provided, wherein the device includes an electrochemical cell 30, 31, 32, 33 having two solid components 11, 12, wherein the two solid components include the same chemical elements, but the concentration of one or more of the chemical elements they share is different. The electrochemical cell 30, 31, 32, 33 also includes a solid electrolyte 14 (dielectric material) disposed between the two solid components 11, 12. The device also includes a circuit 110-150 connected to the electrochemical cell.

[0072] like Figure 6 As shown in the flowchart of FIG. 1 , in S20 , the circuit is used to operate the primitives 30 , 31 , 32 , 33 according to the redox process so as to exchange chemical elements between the solid components 11 , 12 , thereby changing the conductance of each of the two components 11 , 12 .

[0073] Furthermore, in S30, the circuit is used to sense the electrical signal affected by the conductance of the channel, ie, the second solid component 12. The same principle can be used for the plurality of devices 1-4, as previously described with reference to Figure 5 Likewise, steps S20 and S30 will typically be mixed, for example, for the purpose of training the synaptic weights of the neuromorphic device 100 .

[0074] Although the present invention has been described with reference to a limited number of embodiments, variations and drawings, it will be understood by those skilled in the art that, without departing from the scope of the present invention, various changes may be made and equivalents may be used to replace them. In particular, the features (similar devices or similar methods) described in a given embodiment, variation or shown in the drawings may be combined with or replace another feature in another embodiment, variation or drawing without departing from the scope of the present invention. Therefore, various combinations of features described with respect to any of the above-mentioned embodiments or variations may be considered, provided that they remain within the scope of the appended claims. In addition, many minor modifications may be made to adapt specific situations or materials to the teachings of the present invention without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed, but the present invention will include all embodiments falling within the scope of the appended claims. In addition, many other variations other than those explicitly mentioned above may be expected. For example, other materials other than those explicitly cited herein may be used.

Claims

1. An electrochemical device comprising An electrochemical cell, comprising: a first solid component comprising one or more specific chemical elements, wherein a first chemical element of the one or more specific chemical elements is present in the first solid component at a first concentration, a second solid component comprising the one or more specific chemical elements, wherein the first chemical element of the one or more specific chemical elements is present in the second solid component at a second concentration, wherein the first and second concentrations are different, and a first solid electrolyte disposed between the first solid component and the second solid component, wherein the first solid electrolyte is a dielectric material; an electrical circuit coupled to the electrochemical cell and configured to operate the electrochemical cell according to a redox process to exchange the first chemical element between the first solid component and the second solid component and thereby change the conductance of each of the first and second solid components; as well as A substrate comprising a doped substrate, wherein the circuit comprises: a first circuit for operating an electrochemical cell, the first circuit connecting the first solid component to the second solid component; a second circuit for sensing an electrical signal, the second circuit having a first terminal and a second terminal, each terminal connected to the second solid component; and a third circuit connecting the doped substrate to ground.

2. The device according to claim 1, wherein: The first and second solid components each include a compound of at least two of the one or more specific chemical elements, and the first and second solid components each have a different concentration of one of the at least two chemical elements.

3. The device according to claim 2, wherein: The first and second solid components each include: WO3.

4. The device according to claim 3, wherein: The first solid electrolyte comprises a high-κ dielectric material.

5. The device according to claim 4, wherein: The first solid electrolyte includes: HfO2.

6. The device of claim 1 , wherein the electrochemical cell further comprises: a source contact, a drain contact, and a gate contact, wherein each of the source contact and the drain contact is in electrical communication with the second solid component, and the gate contact is in electrical communication with the first solid component, The first circuit is connected to each of the source contact and the gate contact, and The second circuit is connected to the source contact and the drain contact.

7. The device according to claim 6, wherein: the second solid component extending on top of the substrate, The source contact and the drain contact are each in electrical communication with the second solid component, the first solid electrolyte extending on top of the second solid component in contact therewith, The first solid component extends on top of the first solid electrolyte in contact therewith, and The gate contact is arranged on top of the first solid component in contact therewith.

8. The device according to claim 7, wherein: Each of the source contact and the drain contact is disposed on top of the second solid component in contact therewith, and the first solid electrolyte extends between the source contact and the drain contact.

9. The device of claim 1 , wherein the electrochemical cell further comprises: a third solid component extending between the doped substrate and the second solid component, wherein the third solid component comprises one or more specific chemical elements, and the first chemical element of the one or more specific chemical elements is present in the third solid component at a third concentration, wherein the third concentration is different from the second concentration, and A second solid electrolyte extends between the third solid component and the second solid component, and the second solid electrolyte contacts the third solid component and the second solid component.

10. The device according to claim 9, wherein: The circuit also includes a third circuit connected to the first circuit, thereby connecting the doped substrate to the first circuit.

11. The device according to claim 7, wherein: the second solid component being a fin; The source contact and the drain contact each extend on top of the substrate, laterally contacting the fin at each end thereof; and The gate contact, the first solid component, and the first solid electrolyte at least partially wrap around a first portion of the fin.

12. The device according to claim 11, further comprising: a second gate contact, a component comprising the same chemical element at the same concentration as the first solid component, and a solid electrolyte comprising the same composition as the first solid electrolyte, the second gate contact, the component, and the solid electrolyte at least partially wrapped around a second portion of the fin and spaced apart from the gate contact, the first solid component, and the first solid electrolyte at least partially wrapped around the first portion of the fin.

13. The device according to claim 1, wherein: Each of the first solid component and the second solid Formed into a material layer.

14. A device comprising A plurality of electrochemical devices, each electrochemical device having an electrochemical cell, wherein the electrochemical cell comprises: a first solid component comprising one or more specific chemical elements, wherein a first chemical element of the one or more specific chemical elements is present in the first solid component at a first concentration, a second solid component comprising one or more specific chemical elements, wherein the first chemical element of the one or more specific chemical elements is present in the second solid component at a second concentration, wherein the first and second concentrations are different, and a first solid electrolyte disposed between the first component and the second solid component, wherein the first solid electrolyte is a dielectric material; an electrical circuit coupled to the electrochemical cell and configured to operate the electrochemical cell according to a redox process to exchange the first chemical element between the first solid component and the second solid component and thereby change the conductance of each of the first and second solid components; as well as a substrate comprising a doped substrate, wherein the circuit comprises: a first circuit for operating an electrochemical cell, the first circuit connecting the first solid component to the second solid component; a second circuit for sensing an electrical signal, the second circuit having a first terminal and a second terminal, each terminal connected to the second solid component; and a third circuit connecting the doped substrate to ground; a controller for operating the plurality of electrochemical devices, the controller being connected to the circuits of the devices; and A readout circuit for sensing a change in an electrical signal due to a change in the electrical conductance of the second solid component of one or more of the plurality of electrochemical devices, the readout circuit being connected to the circuits of the plurality of electrochemical devices.

15. The apparatus of claim 14, wherein: The apparatus is configured as artificial neural network hardware, and each of the plurality of electrochemical devices is configured as a synaptic element of the artificial neural network hardware.

16. A method of operating an electrochemical device, the method comprising A device is provided comprising an electrochemical cell comprising: a first solid component comprising one or more specific chemical elements, wherein a first chemical element of the one or more specific chemical elements is present in the first solid component at a first concentration, a second solid component comprising one or more specific chemical elements, wherein the first chemical element of the one or more specific chemical elements is present in the second solid component at a second concentration, wherein the first and second concentrations are different, and a first solid electrolyte disposed between the first and second solid components, wherein the first solid electrolyte is a dielectric material, an electrical circuit coupled to the electrochemical cell and configured to operate the electrochemical cell according to a redox process to exchange the first chemical element between the first solid component and the second solid component and thereby change the conductance of each of the first and second solid components; as well as a substrate comprising a doped substrate, wherein the circuit comprises: a first circuit for operating an electrochemical cell, the first circuit connecting the first solid component to the second solid component; a second circuit for sensing an electrical signal, the second circuit having a first terminal and a second terminal, each terminal connected to the second solid component; and a third circuit connecting the doped substrate to ground; operating the electrochemical cell according to the redox process; and A change in the electrical signal due to a change in the electrical conductance of the second solid component is sensed.

Images