KR20220064729A - multi-layered selector device and method of manufacturing the same - Google Patents

Abstract

According to the present invention, provided is a multi-layer selection device exhibiting low leakage current by controlling a threshold voltage. According to one embodiment of the present invention, the multi-layer selection device comprises: a substrate; a lower electrode layer positioned on the substrate; an insulating layer disposed on the lower electrode layer and having a via hole passing through to expose the lower electrode layer; a switching layer formed of multiple layers located on the lower electrode layer within the via hole, performing a switching operation by forming and destroying a conductive filament, and controlling a threshold voltage by controlling formation of the conductive filament; and an upper electrode layer positioned on the switching layer.

Description

Multi-layered selector device and method of manufacturing the same

The technical idea of the present invention relates to a semiconductor device, and more particularly, to a multi-layer selection device and a method of manufacturing the same.

As a next-generation memory structure, a cross-point array structure is likely to be used in a high-density memory device. However, in such a cross-point array structure, write errors and read errors may occur due to current leaking from neighboring cells, and thus, it is difficult to increase the size of the array. Therefore, a selection element capable of suppressing such leakage of current is required. To date, as such devices of choice, tunnel barriers, mixed-ionic-electronic conduction (MIEC), insulator-metal-transition (IMT), ovonic threshold switching (ovonic threshold) switching, OTS), and a diode-type selector have been proposed. However, there is a problem in that the leakage current still appears at a high level even in the selection devices.

Korean Patent Application No. 10-2016-0010338

The technical problem to be achieved by the technical idea of the present invention is to provide a multilayer selection device exhibiting low leakage current by controlling a threshold voltage and a method for manufacturing the same.

However, these tasks are exemplary, and the technical spirit of the present invention is not limited thereto.

According to one aspect of the present invention, a multi-layer selection device exhibiting a low leakage current by controlling a threshold voltage and a method of manufacturing the same are provided.

According to an embodiment of the present invention, the multi-layer selection device comprises: a substrate; a lower electrode layer positioned on the substrate; a switching layer disposed on the lower electrode layer, performing a switching operation by forming and breaking a conductive filament, and comprising a multi-layered switching layer to control a threshold voltage by controlling the formation of the conductive filament; and an upper electrode layer positioned on the switching layer.

According to an embodiment of the present invention, the switching layer may include: a metal doped layer doped with a metal forming the conductive filament; a conductive filament forming layer in which a conductive filament is formed or destroyed by the metal therein; and a threshold voltage control layer configured to control the threshold voltage by controlling the formation of the conductive filament.

According to an embodiment of the present invention, the switching layer may include a threshold voltage control layer disposed on the lower electrode layer; a conductive filament forming layer positioned on the threshold voltage control layer; and a metal doped layer positioned on the conductive filament forming layer.

According to an embodiment of the present invention, a metal doped layer located on the lower electrode layer; a conductive filament forming layer positioned on the metal doped layer; and a threshold voltage control layer positioned on the conductive filament forming layer.

According to an embodiment of the present invention, the switching layer may include a first threshold voltage control layer disposed on the lower electrode layer; a conductive filament forming layer disposed on the first threshold voltage control layer; a metal doped layer positioned on the conductive filament forming layer; and a second threshold voltage control layer disposed on the metal doped layer.

According to an embodiment of the present invention, the switching layer may include a first threshold voltage control layer disposed on the lower electrode layer; a metal doping layer disposed on the first threshold voltage control layer; a conductive filament forming layer positioned on the metal doped layer; and a second threshold voltage control layer positioned on the conductive filament forming layer.

According to an embodiment of the present invention, the switching layer may include a first metal doped layer positioned on the lower electrode layer; a first conductive filament forming layer positioned on the first metal doped layer; a threshold voltage control layer disposed on the first conductive filament forming layer; a second conductive filament forming layer disposed on the threshold voltage control layer; and a second metal doped layer positioned on the second conductive filament forming layer.

According to an embodiment of the present invention, the switching layer, the first conductive filament forming layer located on the lower electrode layer; a first metal doped layer positioned on the first conductive filament forming layer; a threshold voltage control layer disposed on the first metal doped layer; a second metal doped layer disposed on the threshold voltage control layer; and a second conductive filament forming layer positioned on the second metal doped layer.

According to an embodiment of the present invention, the metal doped into the metal doping layer moves to the conductive filament forming layer to form the conductive filament, and the conductive filament may electrically connect the upper electrode layer and the lower electrode layer. .

According to an embodiment of the present invention, the conductive filament formed on the conductive filament forming layer may have a property of being formed when an electrical signal is applied.

According to an embodiment of the present invention, the conductive filament formed on the conductive filament forming layer may have a volatile characteristic that is formed when an electrical signal is applied and is destroyed when the electrical signal is removed.

According to an embodiment of the present invention, the threshold voltage control layer may include at least one of silicon oxide, silicon nitride, silicon oxynitride, hafnium oxide, titanium oxide, tantalum oxide, aluminum oxide, and zirconium oxide.

According to an embodiment of the present invention, the conductive filament forming layer or the metal doped layer is zinc oxide, indium oxide, indium-zinc oxide, indium-gallium oxide, zinc-tin oxide, aluminum-zinc oxide, gallium-zinc oxide , indium-zinc-tin oxide, indium-gallium-zinc oxide, indium-gallium-tin oxide, hafnium oxide, hafnium-zirconium oxide, zirconium oxide, tantalum oxide, titanium oxide, tungsten oxide, manganese oxide, nickel oxide, and magnesium It may include at least one of oxides.

According to an embodiment of the present invention, an adhesive layer interposed between the substrate and the lower electrode layer to bond the substrate and the lower electrode layer to each other may be further included.

According to an embodiment of the present invention, the multi-layer selection device comprises: a substrate; a lower electrode layer positioned on the substrate; an insulating layer positioned on the lower electrode layer and having a via hole passing through to expose the lower electrode layer; a switching layer positioned on the lower electrode layer in the via hole, performing a switching operation by forming and breaking a conductive filament, and comprising a multi-layered switching layer to control a threshold voltage by controlling the formation of the conductive filament; and an upper electrode layer positioned on the switching layer.

According to an embodiment of the present invention, the insulating layer may form a sidewall of the switching layer to individualize the switch layer.

According to an embodiment of the present invention, the method of manufacturing the multi-layer selection device includes: providing a substrate; forming a lower electrode layer on the substrate; forming an insulating layer on the lower electrode layer; removing a portion of the insulating layer to form a via hole exposing the lower electrode layer; forming a multi-layered switching layer in the via hole to control the formation of the conductive filament to control a threshold voltage; and forming an upper electrode layer on the switching layer.

According to an embodiment of the present invention, the forming of the switching layer comprises: forming a threshold voltage control layer comprising an insulating layer and controlling the formation of the conductive filament; forming a conductive filament forming layer in which the conductive filament is formed on the threshold voltage control layer; and forming a metal doping layer for providing a metal to the conductive filaments on the conductive filament forming layer.

According to an embodiment of the present invention, the forming of the switching layer may include: forming a metal doped layer for providing a metal to the conductive filament; forming a conductive filament forming layer in which the conductive filament is formed on the metal doped layer; and forming, on the conductive filament forming layer, a threshold voltage control layer including an insulating layer and controlling the formation of the conductive filament.

According to an embodiment of the present invention, after performing the step of forming the upper electrode layer, the method may further include annealing the multi-layer selection device at a temperature of 100°C to 500°C.

According to the inventive concept, a threshold switching selection device having a controllable threshold voltage in a wide range can be provided by inserting a threshold voltage control layer made of silicon oxide (SiO ₂ ).

This multi-layer selection device utilizes the formation of conductive filaments by movement of ions, and can implement a cross-point array memory with advantages of a simple structure, CMOS compatibility, and high selectivity. In general, it is difficult to control the formation of conductive filaments, so the non-uniformity and reliability of the selection element can be a problem. Here, a multi-layer selection device including a zinc oxide layer doped with silver has been proposed. Using such a multi-layer structure, it is possible to prevent excessive inflow of silver ions in a high on-current state, thereby easily controlling the formation of conductive filaments.

In addition, the multi-layer selection device may have a tunable threshold voltage characteristic of a multi-layer structure by inserting a threshold voltage control layer made of silicon oxide. By controlling the thickness of the silicon oxide of the threshold voltage control layer, the threshold voltage may be controlled in a wide range of 0.6 V to 2.2 V. The multilayer selection device exhibited thermal stability up to 300°C. Comparing the operation of the 1S-1R structure by adjusting the threshold voltage of the multilayer selection device, the leakage current at 1/2 selection voltage was effectively reduced from 10 ^-6 A to 10 ^-13 A.

According to the technical spirit of the present invention, it is possible to reduce the leakage current of the high-density cross-point array device by controlling the threshold voltage using a multi-layer selection device having a wide range of controllable threshold voltage characteristics.

The above-described effects of the present invention have been described by way of example, and the scope of the present invention is not limited by these effects.

1 is a graph illustrating a relationship between a threshold voltage and a leakage current for a multi-layer selection device according to an embodiment of the present invention.
2 is a schematic diagram illustrating a multi-layer selection device according to an embodiment of the present invention.
3 is a cross-sectional view illustrating a multi-layer selection device according to an embodiment of the present invention.
4 is a schematic diagram illustrating the formation and destruction of a conductive filament in a multi-layer selection device according to an embodiment of the present invention.
5 is a cross-sectional view illustrating a switching layer of a multi-layer selection device according to an embodiment of the present invention.
6 to 10 are cross-sectional views illustrating a method of manufacturing a multi-layer selection device according to an embodiment of the present invention according to process steps.
11 is a scanning electron microscope photograph showing a cross-section of a multi-layer selection device according to an embodiment of the present invention.
12 is a graph showing current-voltage characteristics of a multi-layer selection device according to an embodiment of the present invention.
13 is a graph illustrating changes in electrical characteristics according to a thickness of a threshold voltage control layer of a multi-layer selection device according to an embodiment of the present invention.
14 is a graph illustrating current-voltage characteristics under a compliance current of a multi-layer selection device according to an embodiment of the present invention.
15 is a graph illustrating cumulative probability distributions of an on-state and an off-state of a multi-layer selection device according to an embodiment of the present invention.
16 is a graph illustrating durability characteristics of a multi-layer selection device according to an embodiment of the present invention.
17 is a graph illustrating thermal stability characteristics of a multi-layer selection device according to an embodiment of the present invention.
18 is a schematic diagram of a 1S-1R device in which a multi-layer selection device and a resistance switching memory device are combined according to an embodiment of the present invention.
19 is a graph illustrating current-voltage characteristics of a 1S-1R device in which a multi-layer selection device and a resistance switching memory device are combined according to an embodiment of the present invention.
20 is a schematic diagram of a cross-point array device formed using a 1S-1R device in which a multi-layer selection device and a resistance switching memory device are combined according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments of the present invention are provided to more completely explain the technical idea of the present invention to those of ordinary skill in the art, and the following examples may be modified in various other forms, The scope of the technical idea is not limited to the following examples. Rather, these embodiments are provided so as to more fully and complete the present disclosure, and to fully convey the technical spirit of the present invention to those skilled in the art. In this specification, the same reference numerals refer to the same elements throughout. Furthermore, various elements and regions in the drawings are schematically drawn. Accordingly, the technical spirit of the present invention is not limited by the relative size or spacing drawn in the accompanying drawings.

A three-dimensional cross-point array device based on a two-terminal memristor has the advantages of a simple structure, high density, and CMOS compatibility, and is therefore in the spotlight as a next-generation technology. However, the cross-point array memory device has a problem of leakage current caused by a memory cell disposed at an intersection of two access lines. This leakage current limits the maximum size of the array and makes the memory device difficult to operate. Accordingly, in order to overcome the problems related to the leakage current, various devices have been studied in a highly integrated memory structure, for example, insulator-metal-transition (IMT), mixed-ion-electron conduction (mixed) -ionic-electronic conduction (MIEC) and ovonic threshold switching (OTS) have been proposed. However, these devices have a limitation in that a high level of leakage current occurs due to a high off-state current.

As a method for realizing a low leakage current, a selection device to which an electrochemical metallization (ECM) technique is applied may be considered. The selection element can suppress leakage current of nonvolatile memory elements, and is an important component in a high-density cross-point array element. Atomic switch-based selection devices use the formation and destruction of conductive filaments, and have the advantage of low leakage current.

However, the selection device based on electrochemical metallization has a low threshold voltage characteristic that causes a problem that the operating voltage range of the memory device is not matched during the operation of the cross-point array, cannot effectively reduce the leakage current, and may cause a sensing error. there is. In other words, in order to maintain the low leakage current characteristic of the electrochemical metallization-based selection device, the threshold voltage of the selection device needs to be matched with the operating voltage of the memory device.

1 is a graph illustrating a relationship between a threshold voltage and a leakage current for a multi-layer selection device according to an embodiment of the present invention.

Referring to FIG. 1A , in a cross-point array memory device including 1S-1R (one selector-one resistor), when half of all cells are selected to perform a memory operation, a selection voltage V is applied to the selected cells. _select ) is applied, and a 1/2 selection voltage (1/2V _select ) is applied to unselected neighboring cells. The 1/2 selection voltage 1/2V _select is smaller than the selection voltage V _select . When the threshold voltage V _th of the selection device 1S is smaller than the 1/2 selection voltage 1/2V _select , the selection device is in an on-state during a write operation. In this case, the leakage current of the cross-point array memory device is large, and even when the selection device has a low off current (I _off ) and high selectivity, the leakage current is not suppressed and has a large value.

Referring to FIG. 1B , when the threshold voltage V _th of the selection device is greater than the 1/2 selection voltage 1/2V _select , the selection devices of neighboring cells are maintained in an off-state. and the selection element of the selected cell is turned on. In this case, the leakage current of the cross-point array memory device may appear small.

Accordingly, in order to prevent leakage current caused by the neighboring cells, the threshold voltage of the selection element should have a larger value than the 1/2 selection voltage. Furthermore. In order to reduce the leakage current of the cross-point array memory element, the selection element must have an appropriate threshold voltage characteristic and it is necessary to control the threshold voltage.

According to the technical idea of the present invention, in order to control the threshold voltage of such an electrochemical metallization-based selection device, a multi-layered switching layer is proposed. This multi-layer structure can control defects, in which metal ions can migrate, and increase the interface between switching layers to control filament formation and destruction.

2 is a schematic diagram illustrating a multi-layer selection device 100 according to an embodiment of the present invention.

3 is a cross-sectional view illustrating a multi-layer selection device 100 according to an embodiment of the present invention.

2 and 3 , the multilayer selection device 100 includes a substrate 110 , a lower electrode layer 120 , an insulating layer 130 , a switching layer 140 , and an upper electrode layer 150 . .

Specifically, the multilayer selection device 100 includes a substrate 110 ; a lower electrode layer 120 positioned on the substrate; an insulating layer 130 positioned on the lower electrode layer and having a via hole passing through to expose the lower electrode layer; a switching layer 140 positioned on the lower electrode layer in the via hole, performing a switching operation by forming and breaking a conductive filament, and controlling the formation of the conductive filament to control a threshold voltage; and an upper electrode layer 150 positioned on the switching layer.

The substrate 110 may include various substrates. The substrate 110 may be configured by, for example, a silicon layer 112 and a silicon oxide layer 114 disposed on the silicon layer 112 . However, this is exemplary and the technical spirit of the present invention is not limited thereto.

The lower electrode layer 120 may be positioned on the substrate 110 . The lower electrode layer 120 may include a conductive material, for example, platinum, aluminum, copper, gold, silver, iron, palladium, titanium, zinc, molybdenum, tungsten, nickel, niobium, rubidium, iridium, and alloys thereof. may include at least one of

In addition, an adhesive layer 122 interposed between the substrate 110 and the lower electrode layer 120 to bond the substrate 110 and the lower electrode layer 120 to each other may be further included. The adhesion between the substrate 110 and the lower electrode layer 120 may be strengthened by the adhesive layer 122 , and uniform adhesion may be achieved. The adhesive layer 122 may include, for example, titanium, titanium nitride, silicon, aluminum, and iridium. However, in some other embodiments, the adhesive layer may be omitted.

The insulating layer 130 may be positioned on the lower electrode layer 120 . The insulating layer 130 may include a plurality of via holes 135 penetrating to expose the lower electrode layer 120 . The insulating layer 130 may form a sidewall of the switching layer 140 to individualize the switching layer 140 . The insulating layer 130 may include various insulating materials, and may include, for example, at least one of silicon oxide, silicon nitride, silicon oxynitride, hafnium oxide, titanium oxide, tantalum oxide, aluminum oxide, and zirconium oxide. .

The switching layer 140 may be positioned on the lower electrode layer 120 in the via hole 135 . The switching layer 140 may perform a switching operation by forming and breaking a conductive filament. The switching layer 140 may be formed of multiple layers to control the threshold voltage by controlling the formation of the conductive filament.

The upper electrode layer 150 may be positioned on the switching layer 140 . The upper electrode layer 150 may be formed separately in each of the individualized switching layers 140 . The upper electrode layer 150 may include a conductive material, for example, platinum, aluminum, copper, gold, silver, iron, palladium, titanium, zinc, molybdenum, tungsten, nickel, niobium, rubidium, iridium, and alloys thereof. may include at least one of

Hereinafter, the switching layer 140 of the multi-layer selection device 100 will be described in detail.

The switching layer 140 may include a metal doped layer 160 , a conductive filament forming layer 170 , and a threshold voltage control layer 180 .

Specifically, the switching layer 140 may include a metal doped layer 160 doped with a metal forming the conductive filament; a conductive filament forming layer 170 in which a conductive filament is formed or destroyed by the metal therein; and a threshold voltage control layer 180 for controlling a threshold voltage by controlling the formation of the conductive filament.

The metal doped layer 160 may be doped with a metal forming the conductive filament. The metal doped layer 160 may include an insulating material as a matrix, for example, zinc oxide, indium oxide, indium-zinc oxide, indium-gallium oxide, zinc-tin oxide, aluminum-zinc oxide, gallium- Zinc oxide, indium-zinc-tin oxide, indium-gallium-zinc oxide, indium-gallium-tin oxide, hafnium oxide, hafnium-zirconium oxide, zirconium oxide, tantalum oxide, titanium oxide, tungsten oxide, manganese oxide, nickel oxide, and at least one of magnesium oxide. In addition, the metal doped layer 160 may be doped with a metal in the insulating material, for example, at least one of silver, copper, iron, gold, titanium, zinc, magnesium, and tin may be doped. . The metal doped layer 160 may have a metal doping concentration in the range of, for example, 0.01% to 50%.

In the conductive filament forming layer 170 , a conductive filament may be formed or destroyed by the metal therein. The conductive filaments may be formed or destroyed in the following manner. In the multi-layer selection device in which the conductive filament made of silver is formed, when a voltage is applied, silver ions move to the conductive filament-forming layer, and a conductive filament is formed in the conductive filament-forming layer by an oxidation-reduction reaction. At the threshold voltage, the conductive filament expands to electrically connect the upper electrode and the lower electrode. Accordingly, the resistance of the multi-layer selection element is changed from the on-state to the off-state. On the other hand, when the applied voltage is removed, the conductive filaments are decomposed into silver ions, and the decomposition may be accelerated by the Rayleigh instability effect.

The conductive filament forming layer 170 may include an insulating material as a matrix, for example, zinc oxide, indium oxide, indium-zinc oxide, indium-gallium oxide, zinc-tin oxide, aluminum-zinc oxide, gallium- Zinc oxide, indium-zinc-tin oxide, indium-gallium-zinc oxide, indium-gallium-tin oxide, hafnium oxide, hafnium-zirconium oxide, zirconium oxide, tantalum oxide, titanium oxide, tungsten oxide, manganese oxide, nickel oxide, and at least one of magnesium oxide. The conductive filament forming layer 170 may be configured not to be doped with a metal. Alternatively, in the conductive filament forming layer 170 , the insulating material may be doped with a metal, for example, at least one of silver, copper, iron, gold, titanium, zinc, magnesium, and tin may be doped. The conductive filament forming layer 170 may have, for example, a metal doping concentration in the range of 0.01% to 50%.

Insulators constituting each of the metal doped layer 160 and the conductive filament forming layer 170 may be the same or different from each other. Also, the metal doping layer 160 and the conductive filament forming layer 170 may have different metal doping concentrations. The metal doping concentration of the metal doping layer 160 may be greater than the metal doping concentration of the conductive filament forming layer 170 .

The threshold voltage control layer 180 may include a material that controls, for example, suppresses the formation of the conductive filament. Specifically, the threshold voltage control layer 180 may include a material that suppresses diffusion of the metal discharged from the metal doping layer 160 to form the conductive filament. However, the threshold voltage control layer 180 should not completely block the diffusion of the metal. In order to control the diffusion of the metal, the material type of the threshold voltage control layer 180, the quality of the layer, and the thickness of the layer need to be controlled to specifically suppress but not completely block the diffusion of the metal. For example, by forming the threshold voltage control layer 180 using an atomic layer deposition method, a layer having a relatively dense quality may be formed and a layer having a relatively thin thickness may be formed.

The threshold voltage control layer 180 may include various insulating materials, for example, at least one of silicon oxide, silicon nitride, silicon oxynitride, hafnium oxide, titanium oxide, tantalum oxide, aluminum oxide, and zirconium oxide. can do.

The metal doped layer 160 may have a thickness of, for example, 3 nm to 20 nm. The conductive filament forming layer 170 may have a thickness of, for example, 15 nm to 50 nm. The threshold voltage control layer 180 may have a thickness of, for example, 1 nm to 5 nm. However, this thickness is exemplary and the technical spirit of the present invention is not limited thereto.

In addition, the multilayer selection device according to an embodiment of the present invention includes a case that does not include an insulating layer having a via hole. For example, a multi-layer selection device according to an embodiment of the present invention includes: a substrate; a lower electrode layer positioned on the substrate; a switching layer disposed on the lower electrode layer, performing a switching operation by forming and breaking a conductive filament, and comprising a multi-layered switching layer to control a threshold voltage by controlling the formation of the conductive filament; and an upper electrode layer positioned on the switching layer.

4 is a schematic diagram illustrating the formation and destruction of a conductive filament 190 in the multi-layer selection device 100 according to an embodiment of the present invention.

Referring to FIG. 4A , as a comparative example, the threshold voltage control layer 180 is not included. The formation and destruction of the conductive filaments 190 formed in the conductive filament forming layer 170 are shown.

In an OFF state where no electrical signal is applied from the outside or a low level is applied, a conductive filament cannot be formed, and specifically, the metal 192 discharged from the metal doped layer 160 is the lower electrode layer 120 and the upper electrode layer 150 . ) is not electrically connected. For example, the metal doped layer 160 may exist by doping the metal 192 in the insulator matrix 168 . The metal may not be doped in the conductive filament forming layer 170 or may be doped to a level that does not form the conductive filament 190 .

Even when an electrical signal is applied from the outside and the metal 192 moves from the metal doped layer 160 to the conductive filament forming layer 170, the conductive filament 190 connecting the lower electrode layer 120 and the upper electrode layer 150 is formed. If it does not form, it does not exhibit a threshold switching behavior, and the off-state is continuously maintained. That is, the conductive filament 190 may be formed only when an electrical signal greater than or equal to the threshold voltage is applied.

When an electrical signal is applied from the outside to an on state over a certain level, the metal 192 forms a conductive filament 190 in the conductive filament forming layer 170, and accordingly, the lower electrode layer 120 and the upper electrode layer 150. is electrically connected to The electrical signal becomes a voltage greater than or equal to a threshold voltage. Accordingly, the threshold switching behavior is enabled by the formation of the conductive filament 190 .

The movement of the metal 192 in the on state may be performed as follows. When an electrical signal is applied to the lower electrode layer 120 and the upper electrode layer 150 from the outside at a certain level or more, the doped metal 192 of the metal doped layer 160 moves to the conductive filament forming layer 170 to move to the conductive filament. (190) can be formed. When the metal 192 moves, the metal 192 may move to an atomic state or move to a cation state. By forming the conductive filament 190 , the lower electrode layer 120 and the upper electrode layer 150 may be electrically connected. Specifically, the lower electrode layer 120 , the conductive filament forming layer 170 , the metal doped layer 160 , and the upper electrode layer 150 may be physically connected to form an electrical path.

When the off state again, the conductive filament 190 may be destroyed, and the metal 192 constituting the conductive filament 190 may move back to the metal doped layer 160 . Accordingly, the conductive filament 190 may have volatile properties. However, this is exemplary and the case where the conductive filament 190 has non-volatile properties is also included in the technical spirit of the present invention.

Referring to FIG. 4B , as an embodiment, the threshold voltage control layer 180 is included. Similar to the above-described comparative example, the conductive filament 190 may be formed and destroyed. By the formation of the conductive filament 190, the lower electrode layer 120, the threshold voltage control layer 180, the conductive filament forming layer 170, the metal doped layer 160, and the upper electrode layer 150 are physically connected to form an electrical path. can be formed

However, in the case of the embodiment, since it further includes a threshold voltage control layer 180 capable of suppressing the formation of the conductive filament 190, the conductive filament 190 formed on the threshold voltage control layer 180 is in the comparative example. It may be formed under a relatively high voltage, and may have a relatively small dimension. That is, in order to form the conductive filament 190 , the metal 192 must move to the threshold voltage control layer 180 . Since the movement of the metal 192 in the threshold voltage control layer 180 is relatively difficult compared to the conductive filament forming layer 170 , the threshold voltage may be increased.

The metal doping layer 160 , the conductive filament forming layer 170 , and the threshold voltage controlling layer 180 constituting the switching layer 140 may be disposed in various ways as follows.

5 is a cross-sectional view showing a switching layer of the multi-layer selection device 100 according to an embodiment of the present invention.

Referring to FIG. 5A , the switching layer 140a includes a threshold voltage control layer 180 positioned on the lower electrode layer 120 ; a conductive filament forming layer 170 positioned on the threshold voltage control layer 180; and a metal doped layer 160 positioned on the conductive filament forming layer 170 . In this case, the lower electrode layer 120 , the threshold voltage control layer 180 , the conductive filament forming layer 170 , the metal doped layer 160 , and the upper electrode layer 150 may be sequentially stacked.

Referring to FIG. 5B , the switching layer 140b includes a metal doped layer 160 positioned on the lower electrode layer 120 ; a conductive filament forming layer 170 positioned on the metal doped layer 160; and a threshold voltage control layer 180 positioned on the conductive filament forming layer 170 .

In this case, the lower electrode layer 120 , the metal doped layer 160 , the conductive filament forming layer 170 , the threshold voltage control layer 180 , and the upper electrode layer 150 may be sequentially stacked.

Meanwhile, the threshold voltage control layer 180 may be formed in plurality. The threshold voltage control layer 180 may include a first threshold voltage control layer 181 disposed on a lower side and a second threshold voltage control layer 182 disposed on an upper side thereof. The first threshold voltage control layer 181 may be in physical contact with the lower electrode layer 120 . The second threshold voltage control layer 182 may be in physical contact with the upper electrode layer 150 .

Referring to FIG. 5C , the switching layer 140c includes a first threshold voltage control layer 181 positioned on the lower electrode layer 120 ; a conductive filament forming layer 170 positioned on the first threshold voltage control layer 181; a metal doped layer 160 positioned on the conductive filament forming layer 170; and a second threshold voltage control layer 182 positioned on the metal doped layer 160 . In this case, the lower electrode layer 120 , the first threshold voltage controlling layer 181 , the conductive filament forming layer 170 , the metal doping layer 160 , the second threshold voltage controlling layer 182 , and the upper electrode layer 150 ). may be stacked in the order of

Referring to FIG. 5D , the switching layer 140d includes a first threshold voltage control layer 181 positioned on the lower electrode layer 120 ; a metal doping layer 160 positioned on the first threshold voltage control layer 181; a conductive filament forming layer 170 positioned on the metal doped layer 160; and a second threshold voltage control layer 182 positioned on the conductive filament forming layer 170 . In this case, the lower electrode layer 120 , the first threshold voltage controlling layer 181 , the metal doping layer 160 , the conductive filament forming layer 170 , the second threshold voltage controlling layer 182 , and the upper electrode layer 150 ) may be stacked in the order of

In addition, by combining the switching layer 140c and the switching layer 140d, the metal doped layer 160 is positioned on the first threshold voltage control layer 181 and at the same time below the second threshold voltage control layer 182 . A case in which the metal doped layer 160 is located is also included in the technical concept of the present invention. That is, it is a case in which a plurality of metal doped layers 160 are further included. In this case, the lower electrode layer 120 , the first threshold voltage control layer 181 , the metal doped layer 160 , the conductive filament forming layer 170 , the metal doped layer 160 , and the second threshold voltage control layer 182 ) and the upper electrode layer 150 may be stacked in this order.

In addition, a case in which a plurality of conductive filament forming layers 170 are further included is included in the technical concept of the present invention. In this case, the lower electrode layer 120 , the first threshold voltage control layer 181 , the conductive filament forming layer 170 , the metal doping layer 160 , the conductive filament forming layer 170 , and the second threshold voltage controlling layer 182 . , and an upper electrode layer 150 .

The metal doped layer 160 and the conductive filament forming layer 170 may be formed in plurality, respectively. The metal doped layer 160 may include a first metal doped layer 161 disposed on a lower side and a second metal doped layer 162 disposed on an upper side. The conductive filament-forming layer 170 may include a first conductive filament-forming layer 171 disposed on a lower side and a second conductive filament-forming layer 172 disposed on an upper side thereof.

Referring to FIG. 5E , the switching layer 140e may include a first metal doped layer 161 disposed on the lower electrode layer 120 ; a first conductive filament forming layer 171 positioned on the first metal doped layer 161; a threshold voltage control layer 180 positioned on the first conductive filament forming layer 171; a second conductive filament forming layer 172 positioned on the threshold voltage control layer 180; and a second metal doped layer 162 positioned on the second conductive filament forming layer 172 . In this case, the lower electrode layer 120 , the first metal doped layer 161 , the first conductive filament formation layer 171 , the threshold voltage control layer 180 , the second conductive filament formation layer 172 , and the second metal doped layer 162 , and the upper electrode layer 150 may be stacked in this order.

Referring to (f) of FIG. 5 , the switching layer 140f includes a first conductive filament forming layer 171 positioned on the lower electrode layer 120 ; a first metal doped layer 161 positioned on the first conductive filament forming layer 171; a threshold voltage control layer 180 positioned on the first metal doped layer 161; a second metal doped layer 162 positioned on the threshold voltage control layer 180; and a second conductive filament forming layer 172 positioned on the second metal doped layer 162 . In this case, the lower electrode layer 120 , the first conductive filament forming layer 171 , the first metal doped layer 161 , the threshold voltage control layer 180 , the second metal doped layer 162 , and the second conductive filament forming layer 172 , and the upper electrode layer 150 may be stacked in this order.

In FIGS. 5 (e) and (f), a case in which either one of the first metal doped layer 161 and the first conductive filament forming layer 171 is omitted is included in the technical concept of the present invention. In addition, a case in which any one of the second metal doped layer 162 and the second conductive filament forming layer 172 is omitted is also included in the technical concept of the present invention.

6 to 10 are cross-sectional views illustrating a method of manufacturing a multi-layer selection device according to an embodiment of the present invention according to process steps.

6 to 10, the formation and removal of various layers for the formation of the multi-layer selection device can be performed using a chemical vapor deposition method, a physical vapor deposition method, and a lithography method well known in the art, so the detailed description is to be omitted. The method of manufacturing the multi-layer selection device may be implemented by applying a conventional CMOS technology.

Referring to FIG. 6 , a substrate 110 is provided. The substrate 110 may be configured by stacking a silicon layer 112 and a silicon oxide layer 114 .

Referring to FIG. 7 , the lower electrode layer 120 is formed on the substrate 110 . Optionally, before forming the lower electrode layer 120 , the adhesive layer 122 may be formed on the substrate 110 . The adhesive layer 122 and the lower electrode layer 120 may be formed using, for example, electron beam evaporation.

Referring to FIG. 8 , the insulating layer 130 is formed on the lower electrode layer 120 . The insulating layer 130 may be formed using, for example, plasma enhanced chemical vapor deposition (PECVD).

Referring to FIG. 9 , a portion of the insulating layer 130 is removed to form a via hole 135 exposing the lower electrode layer 120 . The via hole 135 may be formed using, for example, a KrF lithography method and a reactive ion etching method.

Referring to FIG. 10 , a multi-layered switching layer 140 is formed in the via hole 135 to control the formation of the conductive filament to control the threshold voltage.

The forming of the switching layer 140 may include: forming a threshold voltage control layer 180 made of an insulating layer and controlling the formation of the conductive filament; forming a conductive filament forming layer 170 on which the conductive filament is formed on the threshold voltage control layer 180 ; and forming a metal doped layer 160 providing a metal to the conductive filaments on the conductive filament forming layer 170 .

Alternatively, the forming of the switching layer 140 may include: forming a metal doped layer 160 providing a metal to the conductive filament; forming a conductive filament forming layer 170 on which the conductive filament is formed on the metal doped layer 160; and forming, on the conductive filament forming layer 170 , a threshold voltage control layer 180 including an insulating layer and controlling the formation of the conductive filament.

The metal doping layer 160 or the conductive filament forming layer 170 may be formed to have a gradient in the doping concentration of the metal by using simultaneous sputtering using both an oxide target and a metal target.

The threshold voltage control layer 180 may be formed using an atomic layer deposition method. Accordingly, a dense and thin layer can be formed.

Next, the upper electrode layer 150 is formed on the switching layer 140 to complete the multilayer selection device 100 of FIG. 2 . The upper electrode layer 150 may be formed using, for example, electron beam evaporation.

In addition, the multilayer selection device 100 may be additionally annealed at a temperature of 100°C to 500°C.

Experimental example

Hereinafter, preferred experimental examples are presented to help the understanding of the present invention. However, the following experimental examples are only for helping understanding of the present invention, and the present invention is not limited by the following experimental examples.

Fabrication of Multilayer Selection Elements

A SiO ₂ /Si substrate having a silicon oxide layer (SiO ₂ ) formed on silicon (Si) was prepared. An adhesive layer and a lower electrode layer were sequentially formed on the substrate by electron beam evaporation. The adhesive layer had a thickness of about 10 nm and included titanium (Ti). The lower electrode layer had a thickness of about 100 nm and included platinum (Pt). Then, an insulating layer was formed on the lower electrode layer using plasma enhanced chemical vapor deposition (PECVD). The insulating layer had a thickness of about 100 nm, and included silicon oxide (SiO ₂ ).

Then, a plurality of via holes passing through the insulating layer were formed using a KrF lithography method and a reactive ion etching method. The via holes had a diameter of 250 nm and a depth of 100 nm. The lower electrode layer was exposed through the via hole. The insulating layer patterned by the via holes is used to isolate cells of the multi-layer selection device.

Then, in the via hole, a silicon oxide layer was formed on the lower electrode layer at about 300° C. using an atomic layer deposition method. The silicon oxide layer had a thickness of about 2 nm or a thickness of about 4 nm.

Then, in the via hole, a zinc oxide layer was formed on the silicon oxide layer by sputtering. The zinc oxide layer was formed with a zinc oxide target (99.99% purity) in an Ar/O ₂ gas environment at a flow rate of 20/1 sccm. The sputtering was performed at a high frequency (RF) power of 150 W. The operating pressure of the sputtering chamber during the formation of the zinc oxide layer was 10 mTorr. The zinc oxide layer had a thickness of about 25 nm.

Then, in the via hole, a silver-doped zinc oxide layer was formed on the zinc oxide layer. The silver-doped zinc oxide layer was formed by forming a silver (Ag) target (99.99% purity) and a zinc oxide (ZnO) target (99.99% purity) in an Ar/O ₂ gas environment at a flow rate of 20/1 sccm. The silver-doped zinc oxide layers were deposited by simultaneous sputtering. In this case, the high frequency (RF) power provided to the zinc oxide target was 150 W, and the direct current power provided to the silver target was 20 W. The operating pressure of the sputtering chamber during the formation of the silver-doped zinc oxide layer was 10 mTorr. The silver-doped zinc oxide layer had a thickness of about 5 nm.

Then, an upper electrode layer was formed on the silver-doped zinc oxide layer by sputtering at 75 W. The upper electrode layer had a thickness of about 60 nm and included platinum (Pt).

The silicon oxide layer corresponds to the threshold voltage control layer 180 , the zinc oxide layer (or silver-undoped zinc oxide layer) corresponds to the conductive filament forming layer 170 , and the silver-doped zinc oxide layer is a metal Corresponds to the doped layer 160 .

It was then annealed for about 10 minutes at a temperature of 300° C. under atmospheric conditions. Accordingly, a multilayer selection device having a Pt/AZO/ZnO/SiO ₂ /Pt structure was formed.

As a comparative example, a single-layer selection device having a Pt/AZO/ZnO/Pt structure was formed in the same manner. The comparative example is a case in which the silicon oxide layer is not included.

Fabrication of resistive switching memory devices

As described above, after preparing the SiO ₂ /Si substrate and forming the adhesive layer, the lower electrode layer, and the insulating layer, a plurality of via holes passing through the insulating layer and exposing the lower electrode layer were formed.

Then, in the via hole, a ZrO _x layer was formed on the lower electrode layer at about 280° C. using an atomic layer deposition method. To form the ZrO _x layer, Zr[N(C ₂ H ₅ )CH ₃ ] ₄ (TEMAZ) was used as a zirconium precursor and ozone was used as an oxygen source. The ZrO _x layer had a thickness of about 5 nm.

Then, in the via hole, a zinc oxide (ZnO) layer was deposited on the ZrO _x layer at 150 W by sputtering. The operating pressure of the sputtering chamber during the formation of the zinc oxide layer was 10 mTorr. The zinc oxide layer had a thickness of about 15 nm.

Then, a titanium (Ti) layer was formed on the ZrO _x layer by direct current sputtering using a titanium (Ti) target (99.99% purity) at room temperature, and then an upper electrode was formed on the titanium layer. During the sputtering, a DC sputtering power of 400 W was applied to the titanium target, and the working pressure of the sputtering chamber was 2 mTorr. The titanium layer could function as an adhesive layer and had a thickness of about 10 nm. The upper electrode layer had a thickness of about 100 nm and included titanium nitride (TiN). Accordingly, a resistance switching memory device having a TiN/Ti/ZnO/ZrO _x /Pt structure was completed.

Characterization of Multilayer Selective Devices

Electrical characteristics of the multilayer selection device were measured at room temperature under atmospheric conditions using a semiconductor parameter analyzer (4200A-SCS, Keithley). The switching characteristics of the multilayer selection device were measured using a pulse generator (33600A, Keysight) and an oscilloscope (TDS 5054, Tektronix). In order to analyze the electrical characteristics of the multilayer selection device, a bias voltage was applied to the upper electrode made of platinum, and the lower electrode was grounded.

The cross-sectional microstructure of the multilayer selection device was observed using a scanning electron microscope (JSM-7800F Prime, JEOL).

Results and discussion

11 is a scanning electron microscope photograph showing a cross-section of a multi-layer selection device according to an embodiment of the present invention.

Referring to FIG. 11 , an adhesive layer made of titanium (Ti), a lower electrode layer made of platinum (Pt), and an insulating layer made of silicon oxide (SiO ₂ ) are formed on a Si/SiO ₂ substrate. A via hole is formed in a portion of the insulating layer. In the via hole, as indicated by a red region, a multi-layer composed of SiO ₂ /ZnO/AZO is formed on the lower electrode layer.

A silicon oxide layer (SiO ₂ ) formed in the via hole is a threshold voltage control layer 180 and may perform a function of controlling a threshold voltage characteristic of the multi-layer selection device. The zinc oxide layer (ZnO) formed in the B-hole is the conductive filament forming layer 170 and may function as a switching layer in which the conductive filament may be formed.

12 is a graph showing current-voltage characteristics of a multi-layer selection device according to an embodiment of the present invention.

Referring to FIG. 12 , by measuring the current voltage (I-V) characteristics of the multi-layer selection device, the effect of the insertion of the threshold voltage control layer made of silicon oxide on the threshold switching characteristics is examined. During electrical measurements, an electrical bias was applied to the platinum upper electrode, and the platinum lower electrode was grounded.

Referring to FIG. 12A , as a comparative example, the threshold voltage control layer is not included. The comparative example had a low level of off current of 10 ^-13 A. In addition, when the voltage was swept from 0 V to 3 V at a compliance current (I _cc ) of 10 μA, a threshold switching behavior was observed at a threshold voltage (V _th ) of 0.7 V. At this time, the resistance was changed from the high resistance state (HRS) to the low resistance state (LRS) at a rate of about 10 ⁸ . Then, when the voltage is swept from 3 V to 0 V in the opposite direction, the low resistance state (LRS) to the high resistance state (HRS) is abruptly changed. The change in resistance from the high resistance state (HRS) to the low resistance state (LRS) is analyzed to be related to the formation of silver (Ag) conductive filaments in the zinc oxide (ZnO) switching layer.

Referring to FIG. 12B , as an embodiment, a threshold voltage control layer made of silicon oxide having a thickness of 4 nm is included. Examples have low levels of off currents, for example from 10 ^-14 A to 10 ^-12 A, for example 10 ^-13 A. In addition, an electroforming phenomenon was exhibited at 3 V at a compliance current of 10 μA (I _cc ). After the electroforming of the device was performed, the voltage was swept from 0 V to 3 V in order to measure the threshold switching of the selection device. As a threshold switching behavior of the multi-layer selection device of the embodiment, a threshold voltage of 2.2 V, which is higher than that of the comparative example, was measured. At this time, the resistance was changed from the high resistance state (HRS) to the low resistance state (LRS) at a ratio of about 10 ⁷ to 10 ⁸ . When the voltage is swept from 3 V to 0 V in the opposite direction, the voltage level is different but abruptly changed from the low resistance state (LRS) to the high resistance state (HRS) with a similar behavior to the comparative example.

Both the comparative examples and the examples exhibited a threshold switching behavior with a low off-state current regardless of the presence of the threshold voltage control layer. However, in the embodiment having the threshold voltage control layer made of the 4 nm-thick silicon oxide, it was confirmed that the threshold voltage was changed from 0.7 V to 2.2 V. Accordingly, the threshold voltage control layer may increase the threshold voltage.

13 is a graph illustrating changes in electrical characteristics according to a thickness of a threshold voltage control layer of a multi-layer selection device according to an embodiment of the present invention.

Referring to FIG. 13A , current-voltage characteristics according to the thickness of the threshold voltage control layer are shown. The comparative example without the threshold voltage control layer exhibited a threshold voltage of 0.7 V. On the other hand, in the case of the embodiment, when the thickness of the threshold voltage control layer made of silicon oxide was 2 nm, the threshold voltage was 1.3 V, and when the thickness of the threshold voltage control layer was 4 nm, the threshold voltage was 2.2 V. it was Accordingly, it can be seen that the threshold voltage increases as the thickness of the threshold voltage control layer increases.

Referring to FIG. 13B , the threshold voltage distribution according to the thickness of the threshold voltage control layer is shown. In each case, the threshold voltage was measured from 20 repeated threshold switching operations. The comparative example without the threshold voltage control layer showed an average threshold voltage of 0.75 V. On the other hand, in the case of the embodiment, when the thickness of the threshold voltage control layer was 2 nm, the average threshold voltage was 1.27 V, and when the thickness of the threshold voltage control layer was 4 nm, the average threshold voltage was 1.95 V. .

From the above results, the threshold voltage of the multi-layer selection device can be increased by inserting the threshold voltage control layer composed of silicon oxide between the conductive filament forming layer composed of zinc oxide and the lower electrode layer, and the thickness of the threshold voltage control layer can also be increased. According to the control, the magnitude of the threshold voltage may be controlled.

When the silicon oxide layer constituting the threshold voltage control layer is formed using an atomic layer deposition method, it has a low density of defects. Silver ions may move through the bonding. Therefore, in order to form a conductive filament by moving silver ions from the metal doped layer composed of silver-doped zinc oxide to the lower electrode layer through the threshold voltage control layer, a high voltage is required because the movement of silver ions in the threshold voltage control layer is difficult. Accordingly, when a threshold voltage control layer is inserted into the electrochemical metallization-based multi-layer selection device, the threshold voltage of the selection device can be controlled.

The threshold switching characteristics were measured by applying a pulse to the multilayer selection device of the embodiment. Write pulses of 6 V and 100 μs and read pulses of 0.6 V and 50 μs were applied to the upper electrode of the selection device with a relaxation time of 10 μs. The relaxation time was defined as a time during which a rapid change in the rectification level was measured after the write pulse was applied. The on-switching time of the selection element was measured to be 6 μs. In addition, the selection element returned to its initial off-state at about 10 μs time. From these results, the multi-layer selection device having the threshold voltage control layer can be stably operated using a pulse operation.

14 is a graph illustrating current-voltage characteristics under a compliance current of a multi-layer selection device according to an embodiment of the present invention.

Referring to FIG. 14 , the threshold switching behavior of the multilayer selection device was measured under various compliance currents (I _cc ) of 0.1 μA, 1 μA, and 10 μA. The multilayer selection device had a threshold voltage control layer with a thickness of 4 nm. Under the various compliance currents, the selection device having the silicon oxide intervening layer exhibited a low off-state current of 10 ^-13 A and a high threshold voltage in the range of about 1.8 V to 2 V. Accordingly, it can be seen that the multi-layer selection device has reliable threshold switching characteristics.

15 is a graph illustrating cumulative probability distributions of an on-state and an off-state of a multi-layer selection device according to an embodiment of the present invention.

Referring to FIG. 15 , the cumulative probability distribution of the on-state resistance and the off-state resistance was measured using repeated DC measurement. The multilayer selection device had a threshold voltage control layer with a thickness of 4 nm. The resistance distribution was measured during 20 repeated DC voltage operations, and the on-state resistance and off-state resistance were measured at a read voltage of 1 V. As a result, it can be seen that, for example, it has a high selectivity in the range of 10 ⁷ to 10 ⁹ , for example 10 ⁸ , and exhibits reliable on-state resistance distribution and off-state resistance distribution.

16 is a graph illustrating durability characteristics of a multi-layer selection device according to an embodiment of the present invention.

Referring to FIG. 16 , in order to evaluate the stability of the selection device during repetitive operation, durability characteristics were measured using repetitive pulse operation. The multilayer selection device had a threshold voltage control layer with a thickness of 4 nm. A write pulse of 4 V and 100 μs and a read pulse of 0.4 V and 50 μs were repeatedly applied with a relaxation time of 100 μs between the pulses to evaluate the durability characteristics of the multilayer selection device. The selection element exhibited stable on-operation and off-operation for 10 ⁴ cycles without significant deterioration, and thus it can be seen that it has reliable threshold switching characteristics.

17 is a graph illustrating thermal stability characteristics of a multi-layer selection device according to an embodiment of the present invention.

Referring to FIG. 17 , the thermal stability of the multilayer selection device was evaluated at various temperatures. The multilayer selection device had a threshold voltage control layer with a thickness of 4 nm. The on-state resistance and the off-state resistance were measured at 1 V, respectively. The on-state resistance and off-state resistance of the multilayer selection element were maintained up to 300° C. without significant deterioration.

From these results, the multi-layer selection device including the threshold voltage control layer made of silicon oxide can be used as a selection device for a memory device.

18 is a schematic diagram of a 1S-1R device in which a multi-layer selection device and a resistance switching memory device are combined according to an embodiment of the present invention.

18A is a case in which a 1S-1R device is configured as a multi-layer selection device that does not include a threshold voltage control layer as a comparative example. 18B is a case in which the 1S-1R device is configured as a multi-layer selection device including a threshold voltage control layer made of silicon oxide having a thickness of 4 nm as an embodiment.

Referring to FIG. 18 , with this combination, compatibility between the multi-layer selection device and the resistance switching memory device can be confirmed. The resistance switching memory device has a TiN/Ti/ZnO/ZrO _x /Pt structure. The resistance switching memory device includes a lower electrode made of platinum (Pt), a memory layer made of ZrO _x and titanium (Ti), and an upper electrode made of titanium nitride (TiN). The lower electrode of the multi-layer selection element and the upper electrode of the resistance switching memory element are electrically connected to each other. A voltage is applied to the upper electrode of the multilayer selection device, and the lower electrode of the resistance switching memory device is grounded. The resistance switching memory device exhibited resistance switching characteristics at a set voltage (V _set ) of 2.8 V.

19 is a graph illustrating current-voltage characteristics of a 1S-1R device in which a multi-layer selection device and a resistance switching memory device are combined according to an embodiment of the present invention.

Referring to FIG. 19A , as a comparative example, a 1S-1R device is configured as a multi-layer selection device that does not include a threshold voltage control layer. In the case of the comparative example, when a voltage was applied, the multilayer selection device performed a switching operation at a threshold voltage of 0.7 V, and the resistance switching memory device performed a SET operation at 2.8 V. Since the threshold voltage V _th of the multi-layer selection element 1S is smaller than the 1/2 selection voltage 1/2V _select , the unselected multi-layer selection element may be in an on-state during a write operation. there is. Accordingly, a large leakage current may appear.

Referring to FIG. 19B , as an embodiment, a 1S-1R device is configured as a multi-layer selection device including a threshold voltage control layer made of silicon oxide having a thickness of 4 nm. In the embodiment, when a voltage is applied, the multilayer selection device performs a switching operation at a threshold voltage of 1.9 V, and the resistance switching memory device performs a set operation at 2.8 V. Since the threshold voltage V _th of the multi-layer selection element 1S is greater than the 1/2 selection voltage 1/2V _select , the unselected multi-layer selection element may be turned off during a write operation. there is. Accordingly, the leakage current may appear small.

20 is a schematic diagram of a cross-point array device formed using a 1S-1R device in which a multi-layer selection device and a resistance switching memory device are combined according to an embodiment of the present invention.

20A is a case in which a 1S-1R device is configured as a multi-layer selection device that does not include a threshold voltage control layer as a comparative example. 20 (b) is a case in which the 1S-1R device is configured as a multi-layer selection device including a threshold voltage control layer made of silicon oxide having a thickness of 4 nm as an embodiment.

Referring to FIG. 20 , in the write operation of the 1S-1R device, the selection voltage V _select is required to be greater than the set voltage V _set . When the 1S-1R devices constitute a cross-point array memory, a difference in leakage current may occur. A 1/2 select voltage (1/2V _select ) may be used to operate the 1S-1R cross-point array memory.

That is, the write select voltage V _select is applied to the word line 1 WL1 , the bit line 4 BL4 is grounded, and the 1/2 select voltage 1/2V _select is applied to unselected word lines and bits. applied to the lines. In this case, a leakage current may occur in unselected cells located on the selected word line 1 (WL1) and bit line 4 (BL4).

As in the embodiment, when the selection element has a high threshold voltage, the leakage current at the 1/2 selection voltage (1/2V _select ) may be represented as low as 10 ^-13 A. However, as in the comparative example, when the selection device has a low threshold voltage, the leakage current at the 1/2 selection voltage (1/2V _select ) is increased to 10 ⁻⁶ A. Also, it may cause a sensing error in other adjacent cells. Therefore, in order to reduce the leakage current of the resistive switching memory device in the cross-point array memory, it is necessary to increase the threshold voltage of the electrochemical metallization-based selection device. From the above results, the threshold voltage control layer made of silicon oxide may affect the threshold voltage and switching characteristics of the multi-layer selection device.

conclusion

An electrochemical metallization-based threshold switching multilayer selection device having a threshold voltage control layer composed of silicon oxide inserted therein was fabricated by sputtering and atomic layer deposition. The silicon oxide was formed using an atomic layer deposition method.

The manufactured multi-layer selection device had a selectivity of 10 ⁸ and had a controllable threshold voltage characteristic in the range of 0.6 V to 2.2 V by controlling the thickness of the silicon oxide constituting the threshold voltage control layer. By inserting the threshold voltage control layer, a controllable threshold voltage characteristic of the multi-layer selection device is realized. The multilayer selection device exhibited reliable threshold switching characteristics during AC operation up to 10 ⁴ cycles. In addition, the thermal stability of the multilayer selection device was maintained up to a temperature of 300° C. without significant deterioration.

By connecting the multilayer selection device and the resistance switching memory device, the leakage current of the memory device was compared at a 1/2 selection voltage (1/2V _select ) depending on selection devices having different threshold voltages. When a threshold voltage control layer is inserted in the multi-layer selection device, the threshold voltage of the multi-layer selection device is induced to be higher than the set voltage of the resistance switching memory device, and the leakage current of the memory cell is 10 ^-6 A to 10 ⁻ It can be controlled to decrease to ¹³ A.

From these results, an electrochemical metallization-based threshold switching multilayer selection device having a wide range of controllable threshold voltages can be applied to a high-density cross-point array memory. In addition, it is possible to implement a multilayer selection device having a controllable threshold voltage characteristic by controlling the thickness of silicon oxide constituting the threshold voltage control layer, and by using the multilayer selection device, it is possible to effectively reduce the leakage current of the high-density junction array memory. can do it

The technical spirit of the present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is the technical spirit of the present invention that various substitutions, modifications and changes are possible within the scope without departing from the technical spirit of the present invention. It will be apparent to those of ordinary skill in the art to which this belongs.

100: multi-layer selection element;
110: substrate;
120: a lower electrode layer;
130: an insulating layer;
135: via hole,
140, 140a, 140b, 140c, 140d, 140e, 140f: switching layer;
150: an upper electrode layer;
160, 161, 162: metal doped layer
168: insulator base
170, 171, 172: conductive filament forming layer
180, 181, 182: a threshold voltage control layer;
190: conductive filament;
192: metal,

Claims (20)

Board;
a lower electrode layer positioned on the substrate;
a switching layer disposed on the lower electrode layer, performing a switching operation by forming and breaking a conductive filament, and comprising a multi-layered switching layer to control a threshold voltage by controlling the formation of the conductive filament; and
Including; an upper electrode layer positioned on the switching layer;
Multilayer selection device. The method of claim 1,
The switching layer is
a metal doped layer doped with a metal forming the conductive filament;
a conductive filament forming layer in which a conductive filament is formed or destroyed by the metal therein; and
Including; a threshold voltage control layer for controlling the threshold voltage by controlling the formation of the conductive filament
Multilayer selection device. The method of claim 1,
The switching layer is
a threshold voltage control layer disposed on the lower electrode layer;
a conductive filament forming layer positioned on the threshold voltage control layer; and
Containing, a metal doped layer located on the conductive filament forming layer;
Multilayer selection device. The method of claim 1,
a metal doped layer positioned on the lower electrode layer;
a conductive filament forming layer positioned on the metal doped layer; and
Including; a threshold voltage control layer located on the conductive filament forming layer;
Multilayer selection device. The method of claim 1,
The switching layer is
a first threshold voltage control layer disposed on the lower electrode layer;
a conductive filament forming layer disposed on the first threshold voltage control layer;
a metal doped layer positioned on the conductive filament forming layer; and
A second threshold voltage control layer positioned on the metal doped layer; including,
Multilayer selection device. The method of claim 1,
The switching layer is
a first threshold voltage control layer disposed on the lower electrode layer;
a metal doping layer disposed on the first threshold voltage control layer;
a conductive filament forming layer positioned on the metal doped layer; and
Containing; a second threshold voltage control layer located on the conductive filament forming layer;
Multilayer selection device. The method of claim 1,
The switching layer is
a first metal doped layer positioned on the lower electrode layer;
a first conductive filament forming layer positioned on the first metal doped layer;
a threshold voltage control layer disposed on the first conductive filament forming layer;
a second conductive filament forming layer disposed on the threshold voltage control layer; and
A second metal doped layer positioned on the second conductive filament forming layer; including,
Multilayer selection device. The method of claim 1,
The switching layer is
a first conductive filament forming layer positioned on the lower electrode layer;
a first metal doped layer positioned on the first conductive filament forming layer;
a threshold voltage control layer disposed on the first metal doped layer;
a second metal doped layer disposed on the threshold voltage control layer; and
Containing; a second conductive filament forming layer positioned on the second metal doped layer
Multilayer selection device. 3. The method of claim 2,
The metal doped into the metal doping layer moves to the conductive filament forming layer to form the conductive filament,
The conductive filament electrically connects the upper electrode layer and the lower electrode layer,
Multilayer selection device. 3. The method of claim 2,
The conductive filament formed on the conductive filament forming layer has a characteristic that is formed when an electrical signal is applied,
Multilayer selection device. 3. The method of claim 2,
The conductive filament formed on the conductive filament forming layer is formed when an electrical signal is applied, and has a volatile characteristic that is destroyed when the electrical signal is removed,
Multilayer selection device. 3. The method of claim 2,
The threshold voltage control layer includes at least one of silicon oxide, silicon nitride, silicon oxynitride, hafnium oxide, titanium oxide, tantalum oxide, aluminum oxide, and zirconium oxide,
Multilayer selection device. 3. The method of claim 2,
The conductive filament forming layer or the metal doped layer is zinc oxide, indium oxide, indium-zinc oxide, indium-gallium oxide, zinc-tin oxide, aluminum-zinc oxide, gallium-zinc oxide, indium-zinc-tin oxide, indium - comprising at least one of gallium-zinc oxide, indium-gallium-tin oxide, hafnium oxide, hafnium-zirconium oxide, zirconium oxide, tantalum oxide, titanium oxide, tungsten oxide, manganese oxide, nickel oxide, and magnesium oxide,
Multilayer selection device. The method of claim 1,
Further comprising an adhesive layer interposed between the substrate and the lower electrode layer to bond the substrate and the lower electrode layer to each other,
Multilayer selection device. Board;
a lower electrode layer positioned on the substrate;
an insulating layer positioned on the lower electrode layer and having a via hole passing through to expose the lower electrode layer;
a switching layer disposed on the lower electrode layer in the via hole, performing a switching operation by forming and breaking a conductive filament, and comprising a multi-layered switching layer to control a threshold voltage by controlling the formation of the conductive filament; and
Including; an upper electrode layer positioned on the switching layer;
Multilayer selection device. 16. The method of claim 15,
The insulating layer forms a sidewall of the switching layer to individualize the switch layer,
Multilayer selection device. providing a substrate;
forming a lower electrode layer on the substrate;
forming an insulating layer on the lower electrode layer;
removing a portion of the insulating layer to form a via hole exposing the lower electrode layer;
forming a multi-layered switching layer in the via hole to control the formation of the conductive filament to control a threshold voltage; and
Including; forming an upper electrode layer on the switching layer;
A method of manufacturing a multilayer selection device. 18. The method of claim 17,
The step of forming the switching layer,
forming a threshold voltage control layer comprising an insulating layer and controlling the formation of the conductive filament;
forming a conductive filament forming layer in which the conductive filament is formed on the threshold voltage control layer; and
Containing;
A method of manufacturing a multilayer selection device. 18. The method of claim 17,
The step of forming the switching layer,
forming a metal doped layer for providing a metal to the conductive filament;
forming a conductive filament forming layer in which the conductive filament is formed on the metal doped layer; and
Including; on the conductive filament forming layer, forming a threshold voltage control layer comprising an insulating layer and controlling the formation of the conductive filament
A method of manufacturing a multilayer selection device. 18. The method of claim 17,
After performing the step of forming the upper electrode layer,
Further comprising the step of annealing the multilayer selection device at a temperature of 100 °C to 500 °C,
A method of manufacturing a multilayer selection device.

Images