• 专利附录
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    • 专利摘要:
    One aspect of the invention relates to a resistive random access memory device comprising: a first electrode; a solid electrolyte made of metal oxide; a second electrode, the first and second electrodes being respectively arranged on either side of said solid electrolyte in metal oxide, the second electrode being able to supply mobile ions circulating in the solid electrolyte in metal oxide towards the first electrode for forming a conductive filament between the first and second electrodes when a potential difference is applied between the first and second electrodes; said device having an interface layer comprising a metal oxide, the interface layer extending at least partially over the first electrode, the solid metal oxide electrolyte extending at least partially over the interface layer.
    公开号:FR3027444A1
    申请号:FR1459900
    申请日:2014-10-15
    公开日:2016-04-22
    发明作者:Gabriel Molas；Marinela Barci
    申请人:Commissariat a lEnergie Atomique CEA；Commissariat a lEnergie Atomique et aux Energies Alternatives CEA；
    IPC主号:
    专利说明:

    [0001] TECHNICAL FIELD OF THE INVENTION The present invention relates to the field of non-volatile rewritable memories, and more specifically that of resistive random access memories. A resistive random access memory comprises first and second electrodes separated by a layer of electrically insulating material, and switches from an insulating state to a conductive state by forming a conductive filament between the first and second electrodes. BACKGROUND OF THE INVENTION Random access memories (called RRAM memories for "Resistive Random Access Memories" in English) are today the subject of great attention, in particular because of their low power consumption and their high operating speed. A resistive type of memory cell has at least two states: a highly resistive state "HRS" ("High Resistance State"), also called "OFF" state, and a weakly resistive state "LRS" ("Low Resistance State") or ON state. It can therefore be used to store binary information. Three types of resistive memories can be distinguished: thermochemical mechanism-based memories, valence-based memories, and electrochemical metallization-based memories. The field of the present invention relates more particularly to this last category based on ionically conductive materials (CBRAM memories or "Conductive Bridging RAM"). The operation resides in the reversible formation and breaking of a conductive filament in a solid electrolyte by dissolving a soluble electrode. These memories are promising because of their low programming voltages (of the order of Volt), their short programming time (<1 ps), their low power consumption and their low integration cost. In addition, these memories can be integrated in the metallization levels of the logic of a circuit ("above IC"), which makes it possible to increase the integration density of the circuit. From the point of view of architecture, they require only a selection device, a transistor or a diode, for example. The operation of the CBRAM memories is based on the formation, within a solid electrolyte, of one or more conductive filaments (also called "dendrites") between two electrodes, when these electrodes are brought to appropriate potentials. The formation of the filament makes it possible to obtain a given electrical conduction between the two electrodes. By modifying the potentials applied to the electrodes, it is possible to modify the distribution of the filament, and thus to modify the electrical conduction between the two electrodes. For example, by reversing the potential between the electrodes, it is possible to remove or reduce the conductive filament, so as to remove or greatly reduce the electrical conduction due to the presence of the filament. Figures 1a, 1b and 1c schematically illustrate the operation of a memory device 1 CBRAM type. The memory device 1 is formed by a stack of the type Metal / ionic conductor / metal. It comprises a solid electrolyte 2, for example based on doped chalcogenide (eg GeS) or oxide (eg A1203). The electrolyte 2 is disposed between a lower electrode 3, for example Pt, forming an inert cathode, and an upper electrode 4 comprising a portion of ionizable metal, for example copper, and forming a soluble anode. A portion of ionizable metal is a portion of metal capable of forming metal ions, for example Cu2 + ions in the case where the ionizable metal is copper, when it is subjected to a suitable electrical potential. The memory device 1 shown in FIGS. 1a, 1b and 1c form a memory point, that is to say a unit memory cell, of a memory comprising a multitude of these memory devices.
    [0002] FIG. 1a schematically illustrates the memory device 1 in the virgin state, before the first use of said memory device 1, that is to say before the first application of a potential difference between the soluble electrode 4 and the inert electrode 3 for the passage of the memory device 1 to the "ON" state. Figure 1b schematically illustrates the memory device 1 in the "ON" state. Figure 1c schematically illustrates the memory device 1 in the "OFF" state. The first use of the memory device 1 makes it possible to go from the blank state to the "ON" state, by performing a so-called "forming" step. The step from "ON" state to "OFF" state is called "RESET", while the step from "OFF" state to "ON" state is called "SET" . When a potential difference is applied between the soluble electrode 4 and the inert electrode 3, the electric potential applied to the soluble electrode 4 being greater than the electric potential applied to the inert electrode 3, an oxidation reaction Reduction takes place at the soluble electrode 4, creating mobile ions. In the case of a soluble copper electrode 4, the following reaction takes place: Cu -> Cu 2 + + 2 e-. The mobile ions then move in the electrolyte 2 under the effect of the potential difference applied between the electrodes. The rate of displacement depends on the mobility of the ion in the electrolyte in question, which guides the choice of the soluble electrode / electrolyte couple (examples: Ag / GeS, Cu / Al 2 O 3, etc.). The rates of displacement of the ions are of the order of nm / ns. Arrived at the inert electrode 3, the mobile ions are reduced by the presence of electrons provided by the electrode 3, resulting in the growth of a conductive filament 5 according to the following reaction: Cu 2 + + 2 e-> Cu Le The conductive filament 5 preferably increases in the direction of the soluble electrode 4. The memory device 1 goes into the "ON" state when the filament 6 allows contact between the electrodes 3 and 4, making the stack conductive. Figure 1b schematically illustrates the memory device 1 in the "ON" state.
    [0003] A potential difference applied between the soluble electrode 4 and the inert electrode 3, the electric potential applied to the soluble electrode 4 being smaller than the electric potential applied to the inert electrode 3, leads on the contrary to the dissolution of the conductive filament 5 To justify this dissolution, thermal mechanisms (heating) and oxidation-reduction are generally invoked. The memory device 1 then goes into the "OFF" state. Often, the electrolyte 2 contains in the "OFF" state a residual filament 6, which is in contact with the cathode 3 but which is not in contact with the anode 4. The residual filament 6 comes from a dissolution Incomplete conductive filament 5. A filament is said to be residual when it does not establish a sufficient electrical conduction between the electrodes to obtain the "ON" state. Figure 1c schematically illustrates the memory device 1 in the "OFF" state. During the first use of the memory device 1, that is to say during the first application of a potential difference between the soluble electrode 4 and the inert electrode 3, the conductive filament 6 is generated for the first time. time: this is the forming step previously mentioned, which allows to go from the "blank" state to the "ON" state. The potential difference required to perform this first forming step is typically greater than the potential difference required subsequently in the SET steps. Moreover, the potential difference necessary to perform the forming step may vary from one memory device to another. In a memory array comprising a plurality of memory devices, there is thus typically a distribution of a dispersion of the potential difference to be applied to each memory device, for the first formation of the conductive filament within each memory device. This dispersion is explained in particular by the fact that the potential difference required to perform the first forming step is a function of the initial resistance value, denoted by RO, of the memory device 1 in the virgin state. In a memory array having a plurality of memory devices, the distribution of the initial resistance value RO typically reaches several decades. During the forming step, it is nevertheless very important to apply to each memory device a potential difference which is adjusted thereto. Indeed, the application of a potential difference lower than the nominal potential difference does not allow the first formation of the conductive filament. On the contrary, the application of a potential difference greater than the nominal potential difference results in a degradation of the electrical performance of the memory device, particularly in terms of reliability, retention and endurance. In order to avoid the application of a too large potential difference on a memory device during the forming step, one solution consists of successively carrying out several forming cycles with increasing potential differences. The state of the memory device is read after each cycle to know its state, that is to say in order to know if the conductive filament is formed or not. If the conductive filament is not formed, the following cycle is carried out. If the conductive filament is formed, the process is stopped for the memory device under consideration. Such a solution, however, involves a high forming time, particularly in the case of a memory array having a plurality of memory devices, the potential difference to be applied to each memory device to be adjusted for each of said memory devices. SUMMARY OF THE INVENTION In this context, an object of the invention is to provide a metal oxide CBRAM memory device for accelerating the forming step while preserving the electrical performance of said memory device. Another object of the invention is to provide a metal oxide CBRAM memory device for accelerating the forming step while improving the electrical performance of said memory device. Another object of the invention is to provide a method of first formation of the conductive filament in a metal oxide CBRAM memory device for accelerating the forming step while preserving the electrical performance of said memory device.
    [0004] Another objective of the invention is to propose a method of first formation of the conductive filament in a metal oxide-based CBRAM memory device making it possible to accelerate the forming step while improving the electrical performance of said memory device. One aspect of the invention thus relates to a resistive random access memory device comprising: a first electrode, referred to as an "inert electrode"; a solid electrolyte made of metal oxide; a second electrode, called a "soluble electrode", the first and second electrodes being respectively arranged on either side of said solid electrolyte in metal oxide, the second electrode being capable of supplying mobile ions flowing in the solid electrolyte oxide metal to the first electrode to form a conductive filament between the first and second electrodes when a potential difference is applied between the first and second electrodes; said device having an interface layer comprising a metal oxide, the interface layer extending at least partially over the first electrode, the solid metal oxide electrolyte extending at least partially over the interface layer.
    [0005] Thanks to the invention, the interface layer comprising a metal oxide advantageously acts as a source of oxygen vacancies for the solid electrolyte oxide metal, tending to attract, or pump, one or more oxygen elements solid electrolyte metal oxide which extends at least partially on said interface layer. The interface layer advantageously allows the generation of a localized path of oxygen vacancies in the solid electrolyte metal oxide, between the soluble electrode and the inert electrode. In addition to the characteristics which have just been mentioned in the preceding paragraph, the resistive random access memory device according to one aspect of the invention may have one or more additional characteristics from among the following, taken individually or in any technically possible combination: metal oxide of the interface layer is a sub-stoichiometric metal oxide of formula MON, with M a metal, 0 oxygen and 1 <x <2. - The metal oxide of the interface layer is an oxide sub-stoichiometric metal of formula MON, with M a metal, 0 oxygen and 1.6 <x <1.9. The metal oxide of the interface layer is a metal oxide of a transition metal of groups 3, 4, 5 or 6 of the periodic table of the elements. The transition metal of groups 3, 4, 5 or 6 of the periodic table of the elements is Ti titanium. Alternatively, the transition metal of groups 3, 4, 5 or 6 of the periodic table of the elements is hafnium Hf or zirconium Zr. - The interface layer extending along a reference plane, the interface layer has a thickness between 0.5 nm and 2 nm, said thickness being measured in a direction substantially perpendicular to said reference plane.
    [0006] Another aspect of the invention relates to a method of first formation of the conductive filament in a resistive random access memory device according to any one of the preceding claims, the method comprising: a so-called "pre-forming" step according to which, the resistive random access memory device being in a first insulating state and having a first resistor R1, a first electrical potential V1 is applied to the first electrode and a second electrical potential V2 is applied to the second electrode, the second electrical potential V2 being lower than first electric potential V1, for the formation of a localized path of oxygen vacancies between the first and second electrodes, the resistive random access memory device at the end of said pre-forming step being in a second insulating state and presenting a second resistance R2 lower than the first resistor R1; a so-called "forming" step according to which, the resistive random access memory device being in the second insulating state, a first electric potential V1 'is applied to the first electrode and a second electric potential V2' is applied to the second electrode, the second electric potential V2 'being greater than the first electrical potential V1', for the formation of the conductive filament between the first and second electrodes, the resistive random access memory device at the end of said forming step being in an on state. In addition to the characteristics that have just been mentioned in the preceding paragraph, the method of first formation of the conductive filament according to one aspect of the invention may have one or more additional characteristics among the following, considered individually or in any technically possible combination: During the pre-forming step, the value of the first electrical potential V1 that is applied to the first electrode and the value of the second potential V2 that is applied to the second electrode are chosen so that the ratio R1 / R2 of the first resistor R1 on the second resistor R2 is of the order of 103.
    [0007] Another aspect of the invention relates to a method of programming a memory array comprising a plurality of resistive random access memory devices according to one aspect of the invention, said method comprising, for each resistive random access memory device of the memory array, a step of implementing the first method of forming the conductive filament according to one aspect of the invention.
    [0008] In addition to the features that have just been mentioned in the preceding paragraph, the method of programming a memory array comprising a plurality of resistive random access memory devices according to one aspect of the invention may have one or more additional characteristics among the following, considered individually or in any technically possible combination: - During each pre-forming step of each resistive random access memory device of the memory array, the first electrical potential V1 and the second electrical potential V2 are specific to each random access memory device resistive, and during each forming step of each resistive random access memory device of the memory array, the first electrical potential V1 'and the second electrical potential V2' are specific to each resistive random access memory device. Alternatively, the method comprises a so-called "general preforming" step according to which, the memory matrix being in a first average insulating state and having a first average resistance, the same first electrical potential is applied to the first electrode and the same second electrical potential is applied to the second electrode of each resistive random access memory device of the memory array for forming a localized path of oxygen vacancies between the first and second electrodes of each resistive random access memory device of the memory array , the memory array at the end of said general preforming step being in a second average insulating state and having a second average resistance lower than the first average resistance. The invention and its various applications will be better understood by reading the following description and examining the figures that accompany it.
    [0009] BRIEF DESCRIPTION OF THE FIGURES The figures are presented for information only and in no way limitative of the invention. FIG. 1a schematically illustrates a memory device of CBRAM type according to the state of the art, in a "blank" state. - Figure 1b schematically illustrates a CBRAM type memory device according to the state of the art, in an "ON" state. FIG. 1 c schematically illustrates a memory device of the CBRAM type according to the state of the art, in an "OFF" state; FIG. 2 schematically illustrates a CBRAM memory device based on a metal oxide according to an aspect of FIG. invention, in a first insulating state. FIG. 3a schematically illustrates a so-called "pre-forming" step of a first method of forming a conductive filament in the metal oxide CBRAM memory device of FIG. 2. FIG. 3b illustrates schematically a so-called "deforming" step of the first method of forming a conductive filament in the metal oxide CBRAM memory device of FIG. 2. FIG. 3c schematically illustrates a so-called "RESET" stage of a method of using the metal oxide CBRAM memory device of FIG. 2. FIG. 4a is a graph showing, for a plurality of CBRAM memory devices according to the state of the art, the distribution of the resistance values before the forming step. FIG. 4b is a graph showing, for a plurality of CBRAM memory devices according to the state of the art, the distribution of the required potential difference values for carrying out the forming step. FIG. 4c is a graph showing, for a plurality of CBRAM memory devices according to the state of the art, the distribution of the resistance values at the end of the forming step. FIG. 5a is a graph showing, for a plurality of metal oxide CBRAM memory devices according to one aspect of the invention, the distribution of the resistance values before the pre-forming step. FIG. 5b is a graph showing, for a plurality of metal oxide CBRAM memory devices according to one aspect of the invention, the distribution of the resistance values at the end of the pre-forming step. FIG. 5c is a graph showing, for a plurality of metal oxide CBRAM memory devices according to one aspect of the invention, the distribution of the required potential difference values for carrying out the forming step, the step pre-forming having been performed. FIG. 5d is a graph showing, for a plurality of CBRAM memory devices based on metal oxide according to one aspect of the invention, the distribution of the resistance values at the end of the forming step, the step pre-forming having been performed. DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT OF THE INVENTION Unless otherwise specified, the same element appearing in different figures has a unique reference. In the present description, the terms "CBRAM memory cell", "CBRAM memory device" and "resistive random access memory device" will be used interchangeably. FIGS. 1a, 1b and 1c, which schematically illustrate a memory device 1 of CBRAM type according to the state of the art, have been previously described. FIG. 2 schematically illustrates a metal oxide CBRAM memory device 10 according to one aspect of the invention, in a first insulating state. The memory device 10 according to one aspect of the invention comprises: a first electrode El, also called an "inert electrode" or "cathode", extending along a reference plane; an interface layer INT extending at least partially over the first electrode El, parallel to the reference plane; a solid electrolyte ML made of metal oxide, extending over the interface layer INT, parallel to the reference plane; a second electrode E2, also called a "soluble electrode" or "anode", extending over the solid electrolyte ML into a metal oxide, parallel to the reference plane. The second electrode E2 preferably comprises: a first ISL layer, called an "ion source layer" made from a soluble conductive element and extending over the solid electrolyte ML into a metal oxide; a second CT layer, called an "electrical contact layer", made from a conductive material and extending at least partially over the ISL ion source layer. The memory device 10 in the first insulating state has a first resistor Ri. The first insulating state is the state of the memory device 10 before the first formation of a conductive filament within said memory device 10. The first electrode El is made of an inert conductive material, that is to say not participating forming a conductive filament within the solid electrolyte ML metal oxide. This inert conductive material may typically be: - ruthenium Ru, - ruthenium dioxide RuO 2, - tungsten W, - tungsten nitride WNx, - tantalum nitride TaN, - titanium nitride TiN, or any alloy or combination of the elements just mentioned. According to an alternative not shown in Figure 2, the first electrode El may have a stud shape. According to this alternative, the interface layer INT extends partially on the first electrode El. The interface layer INT is a source of oxygen vacancies comprising a metal oxide. By "oxygen deficiency source" is meant that the interface layer INT tends to attract, or pump, one or more oxygen elements of the solid electrolyte ML into the metal oxide. When the interface layer INT takes an oxygen element of the solid electrolyte ML metal oxide, there is created a gap oxygen in the solid electrolyte ML metal oxide. The metal oxide of the interface layer INT is preferably a sub-stoichiometric metal oxide of formula MON, with M a metal, oxygen and 1 <x <2. In particular, the metal oxide of the INT interface is preferably a substoichiometric oxide of formula MON with M metal, oxygen and 1.6 <x <1.9. The metal oxide of the interface layer INT is preferably a metal oxide of a transition metal of the periodic table of the elements. In particular, the metal oxide of the interface layer INT is preferably a metal oxide of a transition metal of groups 3, 4, 5 or 6 of the periodic table of the elements. Thus, the metal oxide of the interface layer INT may in particular be a titanium oxide, a hafnium oxide or a zirconium oxide. Alternatively, the metal oxide of the interface layer INT can also be an aluminum oxide.
    [0010] The interface layer INT typically has a thickness E_INT, measured in a direction perpendicular to the reference plane, between 0.5 nm and 2 nm. In the particular example shown in Figure 2, the solid electrolyte ML metal oxide is made of gadolinium oxide Gd203. In particular, the solid electrolyte ML metal oxide can be made of hybridized Gd203 gadolinium oxide, that is to say comprising at least a first sub-layer of gadolinium oxide Gd203 and a second sub-layer of gadolinium Gd203. The first underlayer is a standard RF-sputtered underlayer using arg argon gas, xenon xe, or krypton kr. The second sublayer is a sub-stoichiometric gadoidium oxide Gd203 layer obtained from from a Gadolinium Gd target in reactive oxygen deposit. .
    [0011] Said first and second sub-layers are, at least partially, directly in contact with each other, and said first and second sub-layers are typically of substantially the same thickness. Alternatively, the following configurations, considered individually or in any technically possible combination, may be adopted: the solid electrolyte ML in metal oxide is made of aluminum oxide A1203, zirconium dioxide ZrO 2, TiO 2 titanium dioxide or tantalum oxide Ta205; the solid electrolyte ML in metal oxide comprises at least one bilayer of Gd203 / Al203, Gd203 / GeO, Gd203 / La203, Gd203 / Li20, Gd203 / B203, Gd203 / W02, Gd203NO2, Gd203N205, Gd203 / Mg0 or Gd203 / type. MgA1204; the solid electrolyte ML made of metal oxide comprises at least one Gd203 / Al 2 O 3 / Gd 2 O 3, Gd 2 O 3 / GeO / Gd 2 O 3, Gd 2 O 3 / La 2 O 3 / Gd 2 O 3, Gd 2 O 3 / Li 2 O / Gd 2 O 3, Gd 2 O 3/13203 / Gd 2 O 3, Gd 2 O 3 / W 2 / Gd203, Gd203NO2 / Gd203, Gd203N2O5 / Gd203, Gd203 / MgO / Gd203, Gd203 / MgA1204 / Gd203. The solid electrolyte ML metal oxide typically has a thickness E ML, measured in a direction perpendicular to the reference plane, of the order of a few nanometers. The thickness E_ML of the solid electrolyte ML is typically chosen so that the first resistor R1 of the memory device 10 in the first insulating state is greater than or equal to 109 ohms. The ISL ion source layer of the second electrode E2 is made of a soluble conductive material, that is to say participating in the formation of a conductive filament within the solid electrolyte ML metal oxide. This soluble conductive material may be, for example: copper Cu; a Cu copper alloy with a chalcogenic element such as Te tellurium; zinc Zn; - Ag money copper nitride Cu3N; Zn3N2 zinc nitride; silver nitride Ag3N. The electrical contact layer CT of the second electrode E2 is made from a conductive material, such as, for example, Ti-TiN, that is to say a Ti layer and a TiN layer, or Ta-TaN, that is to say a layer of Ta and a layer of TaN. Figures 3a and 3b schematically illustrate steps of a method of first forming a conductive filament in the memory device 10 according to one aspect of the invention. Figure 3a schematically illustrates a step 101, called "pre-forming". Before the pre-forming step 101, the memory device 10 is in the first insulating state and has the first resistor R1, as previously described. During the pre-forming step 101, a first electrical potential V1 is applied to the first electrode E1 and a second electrical potential V2 is applied to the second electrode E2, the second electrical potential V2 being smaller than the first electrical potential V1. for the formation of a localized path 11 of oxygen vacancies 12. Note that in the case where the first electrical potential V1 is zero, the second electrical potential V2 is negative. At the end of the pre-forming step 101, the memory device 10 is in a second insulating state and has a second resistor R2 which is smaller than the first resistor Ri. The second insulating state is also called "OFF" state, or "HRS" state (of the "High Resistive State"). The potential difference which is applied to the memory device 10 during the pre-forming step 101 is advantageously chosen so that the ratio R1 / R2 of the first resistor R1 on the second resistor R2 is of the order of 103. Thus, in the case where the first resistor R1 is of the order of 109 ohms, the potential difference which is applied to the memory device 10 during the pre-forming step 101 is advantageously chosen so that the second R2 resistance is of the order of 106 ohms.
    [0012] Figure 3b schematically illustrates a step 102, called "forming". Before the forming step 102, the memory device 10 is in the second insulating state and has the second resistor R2. During the forming step 102, a first electrical potential V1 'is applied to the first electrode E1 and a second electrical potential V2' is applied to the second electrode E2, the second electrical potential V2 'being greater than the first electrical potential V1 for the formation of a conductive filament 13. The conductive filament 13 is formed from mobile ions 14. The mobile ions 14 are created at the level of the soluble electrode E2 by an oxidation-reduction reaction, then move in the solid electrolyte ML under the effect of the potential difference applied between the electrodes, before being reduced at the inert electrode El, causing the growth of the conductive filament 13 between the inert electrode El and the soluble electrode E2. Note that in the case where the first electrical potential V1 'is zero, the second electrical potential V2' is positive. At the end of the forming step 102, the memory device 10 is in an on state and has a third resistor R3 which is smaller than the first and second resistors R1 and R2. The third resistor R3 is typically of the order of 103 ohms. The on state is also called the "ON" state or the "LRS" state (of the "Low Resistive State").
    [0013] In general, the lower the value of the resistance of a memory device, the lower the potential difference UFORM = (V2 '- V1') required to perform the forming step 102 is lowered. When the resistance of a given memory device is sufficiently low, a very interesting case can be reached for which the potential difference UFORM required to perform the forming step 102 is equal to the potential difference USET required to perform a step of SET, as previously described. This type of operation is also called "forming free": the difference in forming potential, during the first formation of the conductive filament, is equal to the potential difference of SET, during subsequent formations of the conductive filament. The method according to the invention of first forming a conductive filament within a memory device 10 advantageously makes it possible, by virtue of the pre-forming step 101, to lower the value of the resistance of said memory device 10, by passing from the first resistor R1 to the second resistor R2, while keeping the memory device 10 in an insulating state. The method according to the invention of first formation of a conductive filament within a memory device 10 also makes it possible, thanks to the step 101 of pre-forming, to control the value of the second resistor R2, and thus to contribute to control the value of the potential difference UFORM required to perform the forming step 102. Thus, in the case of a memory array comprising a plurality of memory devices 10 according to one aspect of the invention, the dispersion of the UFORM potential difference values required to carry out the forming step 102 is advantageously reduced. FIG. 3c schematically illustrates a step 103, called "RESET", of a method of using the memory device 10 according to one aspect of the invention. Said method of use advantageously comprises the pre-forming step 101, the forming step 102 and the RESET step 103. Before step 103 of RESET, the memory device 10 is in the on state, that is to say in the LRS or "ON" state, thanks to the conductive filament 13 between the inert electrode El and the soluble electrode E2. During step 103 of RESET, a first electrical potential Vl "is applied to the first electrode E1 and a second electrical potential V2" is applied to the second electrode E2, the second electrical potential V2 "being smaller than the first electrical potential V1 ", for the at least partial dissolution of the conductive filament 13. Note that in the case where the first electrical potential V1" is zero, the second electrical potential V2 "is negative. At the end of step 103 of RESET, the memory device 10 is in the second insulating state, that is to say in the HRS or "OFF" state. At the end of step 103 of RESET, the conductive filament 13 can be completely dissolved: in this case, the memory device 10 has the second resistor R2. At the end of step 103 of RESET, the filament 13 may alternatively be partially dissolved: in this case, the memory device 10 typically has a resistance which is a little less than the second resistance R2, while being of order of the second resistance R2. In general, at the end of step 103 of RESET, the memory device 10 is in an insulating state with a resistance lower than the first resistance R1 of the first insulating state. It is noted that the localized path 11 of oxygen vacancies 12 is not dissolved during step 103 of RESET. Once formed in the memory device 10 by the step 101 of pre-forming, the localized path 11 of oxygen vacancies 12 remains permanently in the memory device 10 used in normal conditions of use. By "localized path 11 oxygen vacancies 12 remains permanently in the memory device 10" the fact that, from one memory cycle to another, said path locates 11 oxygen vacancies 12 is little or not modified: it is possible for the concentration of oxygen vacancies 12 of the localized path 11 to vary substantially during the various "ON" or "OFF" cycles of the memory device 10. "Normal conditions of use" means the conditions making it possible to change the memory device 10 from its "ON" state to its "OFF" state, thanks to the RESET step that has just been described, as well as from its "OFF" state to its "ON" state. , thanks to a so-called "SET" step which is now described. The method of using the memory device 10 according to one aspect of the invention can then typically comprise a step of SET, not shown. Prior to the SET step, the memory device 10 is in the second insulated state, i.e., in the HRS or "OFF" state. Prior to the SET step, the memory device 10 thus comprises the localized path 11 of oxygen vacancies 12 between the soluble electrode E2 and the inert electrode E1, while the conductive filament 13 is partially or completely dissolved. As previously described: - in the case where the conductive filament 13 is completely dissolved, the memory device 10 typically has the second resistor R2, - while in the case where the conductive filament 13 is partially dissolved, the memory device 10 typically has a resistance lower than the second resistor R2, while being of the order of the second resistor R2.
    [0014] During the SET step, a first electrical potential V1- is applied to the first electrode E1 and a second electrical potential V2- is applied to the second electrode E2, the second electrical potential V2- being greater than the first electrical potential V1- , in order to completely reform the conductive filament 13 between the inert electrode El and the soluble electrode E2. Note that in the case where the first electrical potential V1- is zero, the second electrical potential V2- is positive. At the end of the SET step, the memory device 10 is in the on state, that is to say in the LRS or "ON" state, and has the third resistor R3. Note that the potential difference USET = (V2- - V1-) which is applied to the memory device 10 during the SET step is less than or equal to the potential difference UFORM = (V2 '- V1') which is applied to the memory device 10 during the forming step 102. In the case where the memory device 10 has, before the SET step, the second resistor R2, that is to say in the case where the conductive filament 13 has been completely dissolved during the previous step 103 of RESET, then we typically have: UFORM = USET. In the case where the memory device 10 has, before the SET step, a resistance lower than the second resistor R2, that is to say in the case where the conductive filament 13 has been partially dissolved during the previous step 103 of RESET, then USET G UFORM was typically. FIG. 4a is a graph showing, for a first plurality of memory devices according to the state of the art, the distribution of the first resistance values R1 before the first formation of a conductive filament within each of said memory devices according to FIG. state of the art, that is to say before the forming step. FIG. 4b is a graph showing, for the first plurality of memory devices according to the state of the art, the distribution of UFORM potential differences required to carry out the forming step. FIG. 4c is a graph showing, for the first plurality of memory devices according to the state of the art, the distribution of the third resistance values R3 at the end of the forming step. FIG. 4c shows a first difference ec1 between the line of the first resistance values R1 and the line of the third resistance values R3 for the first plurality of memory devices according to the state of the art.
    [0015] FIG. 5a is a graph showing, for a second plurality of memory devices 10 according to one aspect of the invention, the distribution of the first resistance values R1 before the first formation of a conductive filament within each of said memory devices 10 according to an aspect of the invention, that is to say before step 101 of pre-forming. It is found that said distribution of the first resistance values R1 for the second plurality is substantially identical to the distribution of the first resistance values R1 for the first plurality.
    [0016] FIG. 5b is a graph showing, for the second plurality of memory devices 10 according to one aspect of the invention, the distribution of the second resistance values R2 at the end of the pre-forming step. FIG. 5b shows: firstly, that the values of the second resistance R2 are lower than the values of the first resistance R1, which is shown on the graph 5b by the fact that the line of the second resistance values R2 is shifted towards the left to the right of the first resistance values R1; and secondly, that the dispersion of the values of the second resistance R2 is smaller than the dispersion of the values of the first resistance R1, which is shown on the graph 5b by the fact that the line of the second resistance values R 2 presents a slope greater than the slope of the line of the first resistance values R1. FIG. 5c is a graph showing, for the second plurality of memory devices 10 according to one aspect of the invention, the distribution of UFORM potential differences required to perform the forming step 102, the preforming step 101 having been realized. It can be seen: on the one hand, that the potential difference values UFORM for the second plurality are smaller than the values of the potential potential difference UFORM for the first plurality, which results in the fact that the line of the difference values UFORM potential potential for the second plurality, shown in FIG. 5c, is shifted to the left with respect to the line of the UFORM potential difference values for the first plurality, represented in FIG. 4b; and on the other hand, that the dispersion of the potential difference values UFORM for the second plurality is smaller than the dispersion of the potential difference values UFORM for the first plurality, which results in the fact that the line of the values UFORM potential difference for the second plurality, shown in Figure 5c, has a slope greater than the slope of the right UMC potential difference values for the first plurality, shown in Figure 4b.
    [0017] FIG. 5d is a graph showing, for the second plurality of memory devices 10 according to one aspect of the invention, the distribution of the third resistance values R3 at the end of the forming step 102, the preforming step 101 having been realized. Said distribution of the third resistance values R3 for the second plurality is substantially identical to the distribution of the third resistance values R3 for the first plurality.
    权利要求:
    Claims (11)
    [0001]
    REVENDICATIONS1. Resistive random access memory device (10) comprising: - a first electrode (El), referred to as an "inert electrode"; a solid electrolyte of metal oxide (ML); a second electrode (E2), called a "soluble electrode", the first and second electrodes being respectively arranged on either side of said solid electrolyte in metal oxide (ML), the second electrode (E2) being able to supply ions movable (14) circulating in the metal oxide solid electrolyte (ML) to the first electrode (El) to form a conductive filament (13) between the first and second electrodes when a potential difference is applied between the first and second electrodes electrodes; said device being characterized in that it comprises an interface layer (INT) comprising a metal oxide, the interface layer (INT) extending at least partially over the first electrode (El), the solid electrolyte in metal oxide (ML) extending at least partially over the interface layer (INT).
    [0002]
    2. Device (10) according to the preceding claim characterized in that the metal oxide of the interface layer (INT) is a sub-stoichiometric metal oxide of formula MON, with M a metal, 0 oxygen and 1 < x <2.
    [0003]
    3. Device (10) according to the preceding claim characterized in that 1.6 <x <1.9.
    [0004]
    4. Device (10) according to any one of the preceding claims, characterized in that the metal oxide of the interface layer (INT) is a metal oxide of a transition metal groups 3, 4, 5 or 6 periodic table of elements.
    [0005]
    5. Device (10) according to the preceding claim characterized in that the transition metal of groups 3, 4, 5 or 6 of the periodic table of elements is titanium Ti, hafnium Hf or zirconium Zr.
    [0006]
    6. Device (10) according to any one of the preceding claims, wherein the interface layer (INT) extends along a reference plane, characterized in that the interface layer (INT) has a thickness of between 0.5 nm and 2 nm, said thickness being measured in a direction substantially perpendicular to said reference plane.
    [0007]
    7. A method of first forming the conductive filament (13) in a device (10) of resistive random access memory according to any preceding claim, the method comprising: - a step (101) called "pre-forming" according to which the resistive random access memory device being in a first insulating state and having a first resistor R1, a first electrical potential V1 is applied to the first electrode (El) and a second electrical potential V2 is applied to the second electrode (E2), the second electrical potential V2 being smaller than the first electrical potential V1, for the formation of a localized path (11) of oxygen vacancies (12) between the first and second electrodes, the resistive random access memory device at the end of said pre-forming step being in a second insulating state and having a second resistance R2 smaller than the first resistance Ri; a so-called "forming" step (102) according to which, the resistive random access memory device being in the second insulating state, a first electrical potential V1 'is applied to the first electrode (El) and a second electrical potential V2' is applied to the second electrode (E2), the second electric potential V2 'being greater than the first electrical potential V1', for the formation of the conductive filament (6) between the first and second electrodes, the resistive random access memory device at the end said forming step being in an on state.
    [0008]
    8. Method according to the preceding claim characterized in that during the step (101) of pre-forming, the value of the first electrical potential V1 which is applied to the first electrode (El)) and the value of the second potential V2 which is applied to the second electrode (E2) are chosen so that the ratio R1 / R2 of the first resistor R1 on the second resistor R2 is of the order of 103.
    [0009]
    9. A method of programming a memory array comprising a plurality of devices (10) of resistive random access memory according to any one of claims 1 to 6, said method comprising, for each device (10) of resistive random access memory of the matrix. memory, a step of implementing the first method of forming the conductive filament in a resistive random access memory device according to any one of claims 7 or 8.
    [0010]
    10. Method according to the preceding claim characterized in that: - during each step (101) of pre-forming each device (10) of resistive random access memory memory, the first electrical potential V1 and the second electrical potential V2 are specific to each resistive random access memory device; during each step (102) of forming each resistive random access memory device (10) of the memory matrix, the first electrical potential V1 'and the second electrical potential V2' are specific to each resistive random access memory device.
    [0011]
    11. The method of claim 10 characterized in that it comprises a so-called "general preforming" step in which, the memory array being in a first average insulating state and having a first average resistance, the same first electrical potential is applied to the first electrode (El) and the same second electrical potential is applied to the second electrode (E2) of each resistive memory device (10) of the memory array for the formation of a localized path (11) of defect gaps. oxygen (12) between the first and second electrodes of each resistive random access memory device of the memory array, the memory array at the end of said general preforming stage being in a second average insulating state and having a second lower average resistance at the first average resistance.
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    同族专利:
    公开号 | 公开日
    EP3010023B1|2017-08-30|
    US9748477B2|2017-08-29|
    EP3010023A1|2016-04-20|
    US20160111637A1|2016-04-21|
    FR3027444B1|2017-12-22|
    引用文献:
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    法律状态:
    2015-09-28| PLFP| Fee payment|Year of fee payment: 2 |
    2016-04-22| PLSC| Publication of the preliminary search report|Effective date: 20160422 |
    2016-10-24| PLFP| Fee payment|Year of fee payment: 3 |
    2017-09-21| PLFP| Fee payment|Year of fee payment: 4 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1459900A|FR3027444B1|2014-10-15|2014-10-15|RESISTIVE LIFE MEMORY DEVICE|FR1459900A| FR3027444B1|2014-10-15|2014-10-15|RESISTIVE LIFE MEMORY DEVICE|
    EP15189521.6A| EP3010023B1|2014-10-15|2015-10-13|Resistive random access memory device|
    US14/884,328| US9748477B2|2014-10-15|2015-10-15|Method of forming a conductive filament in a living resistive memory device including a pre-forming step to form a localised path of oxygen vacancies from an interface layer|
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