WO2017019068A1 - Dispositifs de mémoire non volatile à résistance comprenant un sélecteur volatil comprenant du cuivre et de l'oxyde de tantale - Google Patents

Dispositifs de mémoire non volatile à résistance comprenant un sélecteur volatil comprenant du cuivre et de l'oxyde de tantale Download PDF

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Publication number
WO2017019068A1
WO2017019068A1 PCT/US2015/042723 US2015042723W WO2017019068A1 WO 2017019068 A1 WO2017019068 A1 WO 2017019068A1 US 2015042723 W US2015042723 W US 2015042723W WO 2017019068 A1 WO2017019068 A1 WO 2017019068A1
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Prior art keywords
selector
top electrode
bottom electrode
volatile
copper
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PCT/US2015/042723
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English (en)
Inventor
Minxian Max Zhang
Katy SAMUELS
Ning GE
Zhiyong Li
R. Stanley Williams
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Hewlett Packard Enterprise Development Lp
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Priority to PCT/US2015/042723 priority Critical patent/WO2017019068A1/fr
Publication of WO2017019068A1 publication Critical patent/WO2017019068A1/fr

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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
    • G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
    • G11C13/0021—Auxiliary circuits
    • G11C13/003—Cell access
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10B—ELECTRONIC MEMORY DEVICES
    • H10B63/00—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices
    • H10B63/20—Resistance change memory devices, e.g. resistive RAM [ReRAM] devices comprising selection components having two electrodes, e.g. diodes
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N70/00—Solid-state devices without a potential-jump barrier or surface barrier, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/20—Multistable switching devices, e.g. memristors
    • H10N70/24—Multistable switching devices, e.g. memristors based on migration or redistribution of ionic species, e.g. anions, vacancies
    • H10N70/245—Multistable switching devices, e.g. memristors based on migration or redistribution of ionic species, e.g. anions, vacancies the species being metal cations, e.g. programmable metallization cells
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N70/00—Solid-state devices without a potential-jump barrier or surface barrier, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/801—Constructional details of multistable switching devices
    • H10N70/821—Device geometry
    • H10N70/826—Device geometry adapted for essentially vertical current flow, e.g. sandwich or pillar type devices
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N70/00—Solid-state devices without a potential-jump barrier or surface barrier, and specially adapted for rectifying, amplifying, oscillating or switching
    • H10N70/801—Constructional details of multistable switching devices
    • H10N70/881—Switching materials
    • H10N70/883—Oxides or nitrides
    • H10N70/8833—Binary metal oxides, e.g. TaOx
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
    • G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
    • G11C13/0007—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements comprising metal oxide memory material, e.g. perovskites
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C2213/00—Indexing scheme relating to G11C13/00 for features not covered by this group
    • G11C2213/70—Resistive array aspects
    • G11C2213/76—Array using an access device for each cell which being not a transistor and not a diode

Definitions

  • NON-VOLATILE RESISTANCE MEMORY DEVICES INCLUDING A VOLATILE SELECTOR WITH COPPER AND TANTALUM OXIDE
  • Non-volatile memory is computer memory that can store information even when not powered.
  • Types of non-volatile memory may include resistive RAM (random access memory) (RRAM or ReRAM), phase change RAM (PCRAM), conductive bridge RAM (CBRAM), ferroelectric RAM (F-RAM), etc.
  • Resistance memory elements such as resistive RAM, or ReRAM
  • resistive RAM can be programmed to different resistance states by applying programming energy. After programming, the state of the resistive memory elements can be read and remains stable over a specified time period.
  • Large arrays of resistive memory elements can be used to create a variety of resistive memory devices, including non-volatile solid state memory, programmable logic, signal processing, control systems, pattern recognition devices, and other applications. Examples of resistive memory devices include valence change memory and electrochemical metallization memory, both of which involve ionic motion during electrical switching and belong to the category of memristors.
  • Memristors are devices that can be programmed to different resistive states by applying a programming energy, for example, a voltage or current pulse.
  • This energy generates a combination of electric field and thermal effects that can modulate the conductivity of both non-volatile switch and nonlinear select functions in a memristive element.
  • the state of the memristor can be read and remains stable over a specified time period.
  • FIGS. 1 A-1 B depict, in perspective, a memristor crossbar and a selector-memristor crossbar, respectively, according to an example.
  • FIG. 2 depicts a half V scheme with selector, according to an example.
  • FIG. 3 is a cross-sectional view, depicting a device structure for a selector, according to an example.
  • FIG. 4 in cross-sectional view, illustrates a nonvolatile memory cell that may include a volatile selector electrically coupled in series with a nonvolatile resistance memory device, according to an example.
  • FIG. 5 depicts a method of manufacturing a memory array with nonvolatile resistance memory devices and volatile selectors, according to an example.
  • FIGS. 6A-6D show the l-V results for a selector having a Ta 2 0 5 selector oxide matrix sandwiched between a Cu bottom electrode and a Cu top electrode, measured at two different current compliances (50 ⁇ for FIGS. 6A- 6B and 40 ⁇ for FIGS. 6C and 6D), according to an example.
  • FIGS. 6B and 6D include the same information as in FIGS. 6A and 6C, respectively, but are plotted on a semi-log scale in current.
  • FIGS. 7A-7B show the l-V results for the same selector as in
  • FIGS. 6A-6D but at a lower current compliance (30 ⁇ ), according to an example.
  • FIG. 7B includes the same information as in FIG. 7A, but is plotted on a semi-log scale in current.
  • Memristors are nano-scale devices that may be used as a component in a wide range of electronic circuits, such as memories, switches, radio frequency circuits, and logic circuits and systems.
  • a crossbar array of memristor devices may be used.
  • memristors When used as a basis for memories, memristors may be used to store bits of information, 1 or 0.
  • a memristor When used as a logic circuit, a memristor may be employed as configuration bits and switches in a logic circuit that resembles a Field Programmable Gate Array, or may be the basis for a wired-logic Programmable Logic Array. It is also possible to use memristors capable of multi-state or analog behavior for these and other applications.
  • non-volatile memory While specific examples to memristors are provided herein, it is appreciated that many other types of non-volatile memory may beneficially employ the teachings herein. Examples of such other types of non-volatile memory may include resistive RAM (random access memory) (RRAM or ReRAM), phase change RAM (PCRAM), conductive bridge RAM (CBRAM), ferroelectric RAM (F-RAM), etc.
  • RRAM or ReRAM resistive RAM
  • PCRAM phase change RAM
  • CBRAM conductive bridge RAM
  • F-RAM ferroelectric RAM
  • the resistance of a memristor may be changed by applying a voltage across or a current through the memristor.
  • at least one channel may be formed that is capable of being switched between two states— one in which the channel forms an electrically conductive path ("ON") and one in which the channel forms a less conductive path ("OFF").
  • conducting channels may be formed by metal ions and/or oxygen vacancies.
  • Some memristors exhibit bipolar switching, where applying a voltage of one polarity may switch the state of the memristor and where applying a voltage of the op- posite polarity may switch back to the original state.
  • memristors may exhibit unipolar switching, where switching is performed, for example, by applying different voltages of the same polarity.
  • Using memristors in crossbar arrays may lead to read and/or write failure due to sneak currents passing through the cells that are not selected, for example, cells on the same row or column as a targeted cell. Failure may arise when there is insufficient current through the targeted memristor due to current sneaking through untargeted neighboring cells. As a result, effort has been spent on minimizing sneak currents.
  • Using a transistor with each memristor has been proposed to isolate each cell and overcome the sneak current.
  • using a transistor with each memristor in a crossbar array limits array density and increases cost, which may impact the commercialization of memristor devices.
  • the memristor When used as a switch, the memristor may either be in a low resistance (ON) or high resistance (OFF) state in a crosspoint memory.
  • the memristor may either be in a low resistance (ON) or high resistance (OFF) state in a crosspoint memory.
  • tantalum oxide (TaO x )-based memristors have been demonstrated to have superior endurance over other nano-scale devices capable of electronic switching. In lab settings, tantalum oxide-based memristors are capable of over 10 billion switching cycles.
  • a memristor may use a switching material, such as TiO x , HfO x or TaOx, sandwiched between two electrodes.
  • Memristive behavior is achieved by the movement of ionic species (e.g., oxygen ions or vacancies) within the switching material to create localized changes in conductivity via modulation of a conductive filament between two electrodes, which results in a low resistance "ON" state, a high resistance “OFF” state, or intermediate states.
  • ionic species e.g., oxygen ions or vacancies
  • the entire switching material may be noncon- ductive. As such, a forming process may be required to form the conductive channel in the switching material between the two electrodes.
  • a known forming process often called “electroforming” includes applying a sufficiently high (threshold) voltage across the electrodes for a sufficient length of time to cause a nucleation and formation of a localized conductive channel (or active region) in the switching material.
  • the threshold voltage and the length of time required for the forming process may depend upon the type of material used for the switching material, the first electrode, and the second electrode, and the device geometry.
  • Metal or semiconductor oxides may be employed in memristive devices; examples include either transition metal oxides, such as tantalum oxide, titanium oxide, yttrium oxide, hafnium oxide, niobium oxide, zirconium oxide, or other like oxides, or non-transition metal oxides, such as aluminum oxide, calcium oxide, magnesium oxide, dysprosium oxide, lanthanum oxide, silicon dioxide, or other like oxides. Further examples include transition metal nitrides, such as aluminum nitride, gallium nitride, boron nitride, and silicon nitride.
  • TaOx and HfO x based memristors have demonstrated the most promising results.
  • both of these oxide systems have a linear current- voltage relation in the ON state, which is not desired due to the sneak path current issue, described above.
  • a nonlinear selector may be in series with each memristor to form a 1 S1 R (one selector - one resistor) structure.
  • a bipolar nonlinear selector to suppress the sneak current in the crossbar array has been fabricated using a simple metal- oxide-metal structure realized by the Schottky emission over the metal/oxide barriers or the resistance change associated with insulator-metal-transition (IMT) or other methods.
  • IMT insulator-metal-transition
  • IMT materials can be used for the selectors (e.g., VO2, T12O3, Nb0 2 , etc.).
  • the metal for the bottom electrode and the top electrode can be TiN, TaN, etc.
  • TaN/Nb0 2 /TaN and TiN/Nb0 2 /TiN have shown good performance.
  • high nonlinearity is based on a comparison of the current density level at two different voltages, here, V and V/2, where V is the selected cell voltage and V/2 is the half-selected cell voltage.
  • the selector's threshold voltage is between V/2 and V.
  • the ratio of the two current densities should be at least 10 3 to be considered a useful nonlinearity. In some cases, the ratio may approach or even exceed 10 6 for improved nonlinearity.
  • a new type of selector which can satisfy both requirements of high nonlinearity and be able to conduct current at a level of a few tens of ⁇ for a nano device size such as 30 nm x 30 nm, or have a current density of at least 10 6 A/cm 2 .
  • the new selector may enable the final production of memristors for large crossbar applications.
  • a volatile, nonlinear selector may be made with a matrix oxide (e.g., Ta 2 0 5 ) and at least one of two electrodes based on a fast diffusing cation metal, such as Cu.
  • a matrix oxide e.g., Ta 2 0 5
  • a fast diffusing cation metal such as Cu.
  • volatile in reference to memory, is meant computer memory that requires power to maintain the stored information; it retains its contents while powered on but when the power is interrupted, the stored data is immediately lost or decays with time, which is characterized by a relaxation time.
  • fast-diffusing is meant that the rate of diffusion should be faster than the rate of diffusion of oxygen vacancies in a memristor oxide (or nitrogen vacancies in a memristor nitride).
  • interstitial diffusion is much fast than substitutional diffusion.
  • Interstitial diffusion has a lower activation energy, and a higher jump frequency (neighboring interstitial sites are always vacant).
  • Substitutional diffusion has a higher activation energy, and a lower jump frequency (neighboring substitutional site may not be vacant).
  • Cu, Ag, and Au are some examples of fast diffusers.
  • fast ions e.g., copper
  • matrix oxide e.g., silicon oxide
  • the Cu-Ta equilibrium dia- gram includes the following equilibrium phases: (1 ) liquid, (2) an FCC terminal solid solution (Cu) with limited solid solubility of Ta, and (3) a BCC terminal solid solution (Ta) with limited solid solubility of Cu.
  • Solid phase Cu and Ta are in equilibrium; therefore, there is no chemical reaction between Cu and Ta atoms.
  • Solid phase Cu or Ta shows no mutual solubility; this can suggest that the enthalpy of mixing between Cu and Ta is positive so that a Cu-Ta bond is not preferentially formed compared to a Cu-Cu or a Ta-Ta bond.
  • the free energy of formation of Ta 2 C>5 is much more negative than that of copper oxide; this can also reduce the chance for Cu oxidation in a tantalum oxide matrix.
  • Cu is to form a VCB across Ta 2 Os quickly when the applied voltage is above threshold, and either Cu is not to form the VCB or the VCB is to disappear quickly when the applied voltage is below threshold.
  • a Cu atom will not react with a Ta atom (see above), a Cu-Ta bond is not likely to form, and therefore Cu can exist or pass through the tantalum oxide without reacting with Ta. This may enable use of Cu as the fast ion for the VCB.
  • the selector may be configured in series with a nonvolatile element, such as a memristor.
  • a nonvolatile element such as a memristor.
  • the term "in series” means that the components are electrically connected along a single path so that the same current flows through all of the components. While the components may be in series, they may or may not be in direct contact with one another, and the order of the components may vary.
  • the nonvolatile element may be linear, or, if nonlinear, then only slightly.
  • the selector formed with the materials mentioned (fast- diffusing cation metal particles) evidences high nonlinearity and volatile charac- terizations.
  • linear and nonlinear refer to the nature of the current- voltage (l-V) curve; that is, whether the curve is linear or nonlinear, respectively.
  • nonlinear may refer to a property of the selector or memristor wherein a change in voltage applied across the selector or memristor results in a disproportionate change in current flowing through the selector or memristor, respectively.
  • FIG. 1 A depicts a crossbar 100 containing a plurality of memory elements 102.
  • Each memory element 102 may include a switching material, such as a switching oxide or switching nitride, sandwiched between a bottom electrode and a top electrode (not visible in FIG. 1 , but depicted in FIG. 4).
  • Each memory element 102 is sandwiched between a bottom electrically conducting trace 106 and a top electrically conducting trace 108.
  • the crossbar 100 is made of a lower layer 1 10 of electrically conducting traces formed by a plurality of bottom conducting traces 106 and an upper layer 1 12 of electrically conducting traces formed by a plurality of top conducting traces 108, with the memory element 102 at each crosspoint 1 14 formed by a bottom trace 106 and a top trace 108.
  • the bottom conductive traces 106 may be referred to as row, or bit, lines
  • the top conductive traces 108 may be referred to as column, or word, lines.
  • FIG. 1 A depicts the situation that while trying to read the high resistive element 102a, a current sneak path exists due to three low resistive elements 102b.
  • the thin line 1 16 with arrow head shows the desired current path.
  • the dashed line 1 18 with arrow head shows a sneak path current path.
  • the solution, illustrated in FIG. 1 B, may be to increase the nonlin- earity or asymmetry of the l-V characteristic of the memristor elements 102, which may ensure that the memristor, or other nonlinear memory device, can be used in large crossbar arrays 150. Increasing the nonlinearity of the memristor cells 102 may result in reduction or even elimination of the sneak path current path 1 18.
  • a nonlinear, nonvolatile memristor cell 102' may include a selector 300 (discussed below in connection with FIG. 3) and a memristor element 102.
  • the selector 300 may be nonlinear and volatile; the memristor 102 may be linear and nonvolatile.
  • the selector 300 may be used to mitigate the sneak path current issue by suppressing the total current passing through the non-selected devices in the array at the given voltage.
  • Nonlinearity may depend on the operating voltage range, which in turn depends on the materials used and structure of the device stack (memristor plus selector). For memristors having a certain operating voltage, there may be a need to tune the threshold of selector 300, such as by adjusting the species, film thickness, concentration, etc., as described in greater detail below.
  • FIG. 2 The concept for a selector associated with a popular reading scheme for a 1 S1 R cell is shown in FIG. 2.
  • the selected low resistance cell is denoted 102'a and the half selected cells having high resistance are denoted 102'b.
  • the high resistance cells 102'b are in the same row or column as the selected cell 102'a. It is the high resistance cells 102'b that may suppress sneak path currents.
  • V is the selected cell voltage
  • V/2 half selected cell voltage
  • G is ground.
  • the selector 300 may include a bottom electrode 302, a top electrode 304, and a selector oxide matrix 306 disposed between the two electrodes.
  • the bottom electrode 302 and top electrode 304 may be symmetrical or asymmetrical. If symmetrical, both electrodes 302 and 304 may be made of the same metal, here, copper (Cu).
  • one of the two electrodes 302, 304 may be copper and the other of the two electrodes may be, but not limited to, aluminum (Al), nickel (Ni), platinum (Pt), tungsten (W), gold (Au), titanium (Ti), ruthenium dioxide (Ru0 2 ), titanium nitride (TiN), tung- sten nitride (WN 2 ), tantalum (Ta), hafnium nitride (HfN), niobium nitride (NbN), tantalum nitride (TaN), and the like.
  • the thickness of the electrodes 302, 304 may be in the range of 0.3 to 20 nm.
  • the minimum thickness may be 0.6 nm.
  • one or both copper electrodes may be based on a copper alloy.
  • a copper alloy may help improve adhesion of the electrode to an underlying layer and/or to the selector oxide matrix 306.
  • suitable elements for alloying with copper may include Ni and Pt, either of which can form continuous solid solution with Cu.
  • Ni also controls amount of Cu moving into Ta 2 05. Essentially, nickel reduces the amount of Cu available to diffuse into the oxide, since nickel will not diffuse into the oxide.
  • the selector oxide matrix 306 may be tantalum oxide.
  • the tantalum oxide may be Ta 2 Os.
  • the tantalum oxide can be an oxide mixture. Examples of oxides that may be mixed with Ta 2 Os include silica (Si0 2 ) or alumina (Al 2 0 3 ). Up to about 25 at% (atomic percent) Si or Al may be employed. The addition of silica or alumina may reduce leakage current.
  • the tantalum oxide can include a dispersion of copper atoms or copper oxide, in the form of Cu 2 0 or CuO.
  • the tantalum oxide may include up to about 10 at% Cu atoms or ions.
  • the thickness of the selector oxide matrix may range from about 3 to 100 nm.
  • an example nonvolatile memory cell 102' may include the volatile selector 300 electrically coupled in series with the nonvolatile resistance memory device, such as memristor 102.
  • the nonvolatile resistance memory device 102 may include a switching layer 406 composed of an oxide or nitride sandwiched between a first bottom electrode 402 and a first top electrode 404.
  • the volatile selector 300 may include the selector oxide matrix 306 sandwiched between a second bottom electrode 302 and a second top electrode 304. In a crossbar configuration (FIG.
  • each memory cell 102' may be disposed at the intersection 1 14 formed by one of the bottom conducting traces 106 and one of the top conducting traces [0034]
  • the electrodes 402, 404 for the memristor 102 may include aluminum (Al), platinum (Pt), tungsten (W), gold (Au), titanium (Ti), ruthenium dioxide (Ru0 2 ), titanium nitride (TiN), tungsten nitride (WN 2 ), tantalum (Ta), hafnium nitride (HfN), niobium nitride (NbN), tantalum nitride (TaN), and the like.
  • the thickness of the electrodes 402, 404 may be in the same range as for electrodes 302, 304.
  • the teachings herein may be employed with a crossbar that is fabricated with resistance memory devices, or resistance random access memory devices, denoted RRAM or ReRAM, such as phase change RAM (PCRAM), spin transfer torque RAM (STTRAM), conductive bridge RAM (CBRAM), and others.
  • RRAM resistance random access memory
  • PCRAM phase change RAM
  • STTRAM spin transfer torque RAM
  • CBRAM conductive bridge RAM
  • the nonvolatile resistance memory device 102 may be a memristor.
  • the nonvolatile memory cell 102' may include an optional interface layer 408 sandwiched between the first top electrode 404 of the nonvolatile resistance memory device 102 and the second bottom electrode 302 of the selector 300.
  • the interface layer 408 may serve as a buffer layer to separate the memristor and selector so that they do not chemically and/or physically interfere with each other.
  • the interface layer 408 may be a good electrical conductor over the temperature range from room temperature (approximately 20° to 26°C) to about 1 10°C and a good diffusion barrier.
  • the interface layer 408 may be a metal, such as tantalum or tungsten. The choice of a material for the interface layer may depend on layers below and above it.
  • interface layer 408 may include TiN, Ti 4 0 7 , TaN, NbN, Ru, and W.
  • the interface layer 408 is optional, in that it may be omitted, since the nonvolatile memory cell 102' may operate fine without it. Alternatively, it may be used for an improved device 102', but accepting the costs associated with providing the extra layer.
  • a memory array, or crossbar, 150 (in FIG. 1 B) having nonvolatile resistance memory devices may include a set 1 10 of electrically conducting row traces 106 intersecting a set 1 12 of electrically conducting column traces 108 to form intersections 1 14, with a memory cell 102' disposed at each intersection between one of the row lines and one of the column lines.
  • the memory cell 102' may be a combination of a volatile selector 300 electrically coupled in series with the nonvolatile resistance memory device 102, as described above.
  • the first bottom electrode 402 may be electrically coupled to a row trace 106 or to a column trace 108 and wherein the second top electrode 304 may be electrically coupled to the other of the row trace 106 or the column trace 108.
  • the switching material 406 and selector oxide matrix 306 layers may be coupled directly to the electrically conducting row trace 106 and the electrically conducting column trace 108, respectively.
  • the method 500 includes providing 505 a set 1 10 of electrically conducting row traces 106.
  • the electrically conducting row traces 106 may be formed by any of a number of processes, including electroplating, sputtering, evaporation, ALD (atomic layer deposition), co-deposition, chemical vapor deposition, IBAD (ion beam assisted deposition), oxidation of pre-deposited materials, or any other film deposition technology.
  • the method 500 further includes providing 510 memory cells 102' disposed at a plurality of locations along the set 1 10 of row traces 106.
  • the memory cell 102' may include the nonvolatile resistance memory device 102 electrically coupled in series with the volatile selector 300 or 300', as described above.
  • deposition of the metal layers 402, 404, 302, and 304 may be performed by such processes as electroplating, sputtering, evaporation, ALD (atomic layer deposition), co-deposition, chemical vapor deposition, IBAD (ion beam assisted deposition), oxidation of pre-deposited materials, or any other film deposition technology.
  • the switching material layer 406, the optional interface layer 408, and the selector oxide matrix 406 may be formed by e-beam deposition, sputter deposition, atomic layer deposition (ALD), and the like.
  • the layers 402, 406, 404, 408 (if used), 302, 306, and 304 may be deposited sequentially. It will be appreciated that in FIG. 4, the selector 300 is shown on “top” and the memristor 102 is shown on the "bottom” of the cell 102'. However, in some examples, the memristor 102 may be on "top” and the selector 300 on the "bottom”.
  • the method 500 concludes with providing 515 a set 1 12 of electrically conducting column traces 108 to contact the memory cells 102' at unique intersections 1 14.
  • the electrically conducting column traces 1 12 may be formed by any of a number of processes, including electroplating, sputtering, evaporation, ALD (atomic layer deposition), co-deposition, chemical vapor deposition, IBAD (ion beam assisted deposition), oxidation of pre-deposited materials, or any other film deposition technology.
  • the process used may be the same as or different than the process used to form the electrically conducting row traces 1 10.
  • the order of the steps of method 500 may be reversed, so that the column traces 108 are formed first and the row traces 106 are formed last.
  • the new selector 300, 300' may have a nonlin- earity of >10 6 with large current density.
  • a nonlinearity of >10 6 may allow a crossbar array of 1000 rows by 1000 columns, or 10 6 memristors to populate the 10 6 crosspoints.
  • a nonlinearity on the order of 10 3 could lead to a smaller array. Since a Cu-Ta-0 ternary phase diagram was not available, it was estimated that there is no reaction between Cu and Ta 2 Os, especially at low temperatures.
  • a VCB crossbar device was fabricated having the structure as shown in FIG. 3.
  • the bottom electrode was Ti 2 nm/Cu 15 nm evaporated through a shadow mask. Ti was used as an adhesion layer between the Si substrate (covered with thermally grown Si0 2 ) and Cu.
  • Ta 2 Os 15 nm was a blanket film sputtered from a Ta 2 Os target.
  • the top electrode was Cu 10 nm/Pt 20 nm evaporated through a shadow mask.
  • the effective device stack was Cu/Ta 2 0 5 /Cu.
  • FIGS. 6- 7 show the electric characterizations of the device. Specifically, FIGS. 6A-6D and 7A-7B show the l-V results using the Ta 2 0 5 selector oxide matrix 306 with Cu bottom electrode 302 and Cu top electrode 304 from the same device with the only variation in current compliance.
  • FIG. 6B shows the same information as in FIG. 6A, but plotted on a semi-log scale in current.
  • FIG. 6D shows the same information as in FIG. 6C, but plotted on a semi-log scale in current.
  • FIG. 7B shows the same information as in FIG. 7A, but plotted on a semi-log scale in current.
  • the device demonstrated several encouraging behaviors: a clear threshold volatile switching (-0.4 V), reasonable ON current (about 30 to 50 ⁇ ), and a transition from open loop to narrow loop volatile switching from the same device.
  • the present device may have a relatively high leakage current, which can be due to the sputtered Ta oxide deviating from Ta 2 Os. This can be corrected by using ALD Ta 2 0 5 , or sputter Ta 2 0 5 under oxygen plasma, or increase the Ta 2 0 5 thickness, or dope Ta 2 0 5 with Si0 2 or Al 2 0 3 .
  • the VCB selectors disclosed herein can have a large nonlinearity (large ON-OFF ratio), as shown in FIGS. 6A-6D.
  • the VCB selectors also may have a low operating energy (no joule heating compared with an IMT selector); here, the VCB switch energy (voltage * current ⁇ time) is lower than the IMT switching energy.
  • the VCB selectors may have a high current density, as evidenced by the 30 ⁇ to 50 ⁇ ON current, which is sufficient to write a memristor.
  • the VCB selectors may have an adjustable threshold voltage, which can be achieved by adjusting the thickness of the selector oxide 306 or the doping level of the selector oxide.
  • the selector disclosed herein may achieve both high current in a low resistance state and high nonlinear selection functions.

Abstract

L'invention concerne une cellule de mémoire non volatile comprenant un sélecteur volatil couplé électriquement en série à un dispositif de mémoire non volatile à résistance. Le dispositif de mémoire non volatile à résistance comprend un oxyde de commutation ou un nitrure de commutation intercalé entre une première électrode inférieure et une première électrode supérieure. Le sélecteur volatil comprend une matrice d'oxyde de sélecteur intercalée entre une seconde électrode inférieure et une seconde électrode supérieure. La matrice d'oxyde de sélecteur comprend de l'oxyde de tantale tandis que la seconde électrode inférieure et/ou la seconde électrode supérieure comprennent du cuivre. L'invention concerne également une matrice mémoire utilisant la cellule de mémoire ainsi qu'un procédé de fabrication de la matrice mémoire.
PCT/US2015/042723 2015-07-29 2015-07-29 Dispositifs de mémoire non volatile à résistance comprenant un sélecteur volatil comprenant du cuivre et de l'oxyde de tantale WO2017019068A1 (fr)

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CN111799372A (zh) * 2020-05-15 2020-10-20 上海华力微电子有限公司 Rram阻变结构的形成方法
WO2023245204A1 (fr) * 2022-06-17 2023-12-21 Tetramem Inc. Dispositifs de mémoire vive résistive ayant des électrodes non réactives composées

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US20110002161A1 (en) * 2009-07-06 2011-01-06 Seagate Technology Llc Phase change memory cell with selecting element
US20120250395A1 (en) * 2011-04-04 2012-10-04 Commissariat A L'energie Atomique Et Aux Energies Alternatives Selector type electronic device
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CN111799372A (zh) * 2020-05-15 2020-10-20 上海华力微电子有限公司 Rram阻变结构的形成方法
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WO2023245204A1 (fr) * 2022-06-17 2023-12-21 Tetramem Inc. Dispositifs de mémoire vive résistive ayant des électrodes non réactives composées

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