KR20130014004A - Resistance variable memory device and method for fabricating the same - Google Patents

Abstract

PURPOSE: A variable resistance memory device and a manufacturing method thereof are provided to improve a switching characteristic by controlling a conductivity filament within a variable resistance material layer. CONSTITUTION: A conductive film for a first electrode is formed on a substrate. A nanowire(12) made of variable resistance material is formed on the conductive film. An insulating layer(13) covering the nanowire is formed on the conductive film. Part of the insulating layer is removed to expose the nanowire. A conductive film for a second electrode is formed on the insulating layer.

Description

TECHNICAL FIELD [0001] The present invention relates to a variable resistance memory device and a method of manufacturing the same,

The present invention relates to a variable resistance memory device and a method of manufacturing the same, and more particularly, to a variable resistance memory device using a nano-wire and a method of manufacturing the same.

The variable resistance memory device refers to a device that stores data using a material (hereinafter, referred to as a variable resistance material) that switches between different resistance states according to an applied voltage. As the variable resistance material, a metal oxide, a perovskite-based material, or the like is used.

The switching mechanism of the variable resistance memory device will be briefly described as follows.

The initial state of the predetermined variable resistance material layer is a high resistance state, that is, an off state. When a specific voltage is applied across the variable resistance material layer, switching from a high resistance state to a low resistance state, that is, an on state occurs, which is called a set operation. Once switched to the low resistance state, the state is maintained until another specific voltage is applied, and when another specific voltage is applied, the state is switched from the low resistance state to the high resistance state, which is called a reset operation. At this time, the set operation and the reset operation are performed in such a manner that a conductive filament is locally formed in the variable resistance material layer or the generated conductive filament is broken and extinguished.

However, since the size of the conductive filament or the position of the conductive filament is difficult to be arbitrarily adjusted, there is a problem that the uniformity of the switching is lowered such as the set voltage / current and the reset voltage / current are not constant. In addition, when the size of the conductive filament is large, that is, when the width of one conductive filament is large or a large number of conductive filaments are generated, there is a problem in that switching current is difficult and power required for operation is increased because the flowing current increases.

Therefore, the development of a variable resistance memory device that can solve the above problems is required.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a variable resistance memory device and a method of manufacturing the same, which may ensure improved switching characteristics by controlling conductive filaments in the layer of variable resistance material.

According to one or more embodiments of the present invention, a variable resistance memory device includes: a first electrode; A second electrode; An insulating layer interposed between the first electrode and the second electrode; And nanowires passing through the insulating layer and connected between the first electrode and the second electrode and made of a variable resistance material.

In addition, a method of manufacturing a variable resistance memory device according to an embodiment of the present invention for solving the above problems, forming a conductive film for the first electrode on the substrate; Forming a nanowire made of a variable resistance material on the conductive film for the first electrode; Forming an insulating layer covering the nanowires on the conductive film for the first electrode; Removing a portion of the insulating layer to expose the nanowires; And forming a conductive film for the second electrode on the partially removed insulating layer.

According to the variable resistance memory device according to the present invention described above, improved switching characteristics can be secured by controlling the conductive filaments in the variable resistance material layer.

1 is a cross-sectional view illustrating a variable resistance memory device according to an exemplary embodiment of the present invention.
2 to 6 are cross-sectional views illustrating a method of manufacturing a variable resistance memory device according to an exemplary embodiment of the present invention.
7 is a photograph showing that a tungsten oxide (WO 3) whisker is formed.
8 and 9 are cross-sectional views illustrating a method of manufacturing a variable resistance memory device according to another exemplary embodiment of the present invention.

Hereinafter, the most preferred embodiment of the present invention will be described. In the drawings, the thickness and spacing are expressed for convenience of description and may be exaggerated compared to the actual physical thickness. In describing the present invention, known configurations irrespective of the gist of the present invention may be omitted. It should be noted that, in the case of adding the reference numerals to the constituent elements of the drawings, the same constituent elements have the same number as much as possible even if they are displayed on different drawings.

1 is a cross-sectional view illustrating a variable resistance memory device according to an exemplary embodiment of the present invention.

Referring to FIG. 1, a variable resistance memory device according to an exemplary embodiment may be interposed between a first electrode 11, a second electrode 14, a first electrode 11, and a second electrode 14. An insulating layer 13 and a nanowire 12 connected between the first electrode 11 and the second electrode 14 through the insulating layer 13 and made of a variable resistance material.

Specifically, the first electrode 11 and the second electrode 14 are conductive materials, for example, aluminum (Al), platinum (Pt), ruthenium (Ru), iridium (Ir), nickel (Ni), and nitride. Titanium (TiN), titanium (Ti), cobalt (Co), chromium (Cr), tungsten (W), copper (Cu), zirconium (Zr), hafnium (Hf) or an alloy thereof.

The insulating layer 13 may include an oxide or a nitride.

Nanowire 12 is a variable resistance material, for example, nickel oxide (NiO), titanium oxide (TiO 2), hafnium oxide (HfO), niobium oxide (Nb 2 O 5), zinc oxide (ZnO), zirconium oxide (ZrO 2), tungsten It may be formed of a transition metal oxide such as oxide (WO 3), cobalt oxide (CoO), manganese oxide (MnO 2), or a perovskite-based material such as STO (SrTiO), PCMO (PrCaMnO), or GST (GeSbTe). . In particular, the present specification shows an experimental example in which the nanowires 12 are formed of tungsten oxide, which will be described later with reference to FIG. 6.

In the drawing, two nanowires 12 are shown to be connected between the first and second electrodes 11 and 14, respectively, but the present invention is not limited thereto. The nanowires 12 may be one or plural. In addition, some of the plurality of nanowires 12 may be connected between the first and second electrodes 11 and 14 as shown in the figure, while others may be connected to the first and second electrodes 11 and 14. May not be connected between them (see dashed line in FIG. 1). This is because, as will be described later, the nanowire 12 may not grow in a certain direction and height depending on the manufacturing method. In the present invention, at least one of the plurality of nanowires 12 may be connected between the first and second electrodes 11 and 14.

In such a variable resistance memory device, the generation / destruction of the conductive filament F occurs only in the nanowires 12 connected therebetween according to the voltages applied to the first electrode 11 and the second electrode 14. The conductive filament F is not generated in the insulating layer 13 surrounding the nanowires 12 or the nanowires (see the dotted line in FIG. 1) that are not connected between the first and second electrodes 11 and 14. to be.

Therefore, since the position or size of the conductive filament F is limited by the width and position of the nanowire 12, the size or position of the conductive filament F is constant and switching accordingly even if a plurality of reset / reset operations are repeated. The uniformity of can be improved. In addition, even if a plurality of nanowires 12 are grown, if only a portion (eg, one) of them is connected between the first and second electrodes 11 and 14, the size of the conductive filament F becomes small. Since the flowing current is reduced, there is an advantage that the switching is easy and the operating power is reduced.

2 to 6 are cross-sectional views illustrating a method of manufacturing a variable resistance memory device according to an exemplary embodiment of the present invention. In particular, the present embodiment describes a manufacturing method in the case where the above-described nanowires are metal oxides exhibiting variable resistance characteristics.

Referring to FIG. 2, a first conductive layer 110 for forming a first electrode is formed on a substrate (not shown) having a predetermined lower structure.

Next, a metal layer 122 is formed on the first conductive film 110. The metal layer 122 is made of a metal (eg, tungsten) included in the nanowire when the nanowire is made of a predetermined metal oxide (eg, tungsten oxide). Formation of the metal layer 122 may be performed by a deposition method such as atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), or the like, and may be formed with a relatively thin thickness of 100 nm or less. .

Referring to FIG. 3, when the heat treatment process of the process resultant of FIG. 2 is performed over a predetermined threshold temperature (eg, 700 degrees) for several tens of seconds in an oxygen or nitrogen atmosphere, the metal layer 122 is oxidized to the nanowire 120. To grow. As a result, the nanowires 120 formed of the oxide of the metal layer 122 are formed on the first conductive film 110.

In the present embodiment, all of the metal layer 122 is oxidized to be transformed into the nanowire 120, but the present invention is not limited thereto. In another embodiment, only a part of the metal layer may be oxidized, which will be described later with reference to FIGS. 8 and 9.

In addition, in the present embodiment, eight nanowires 120 are formed at the same height, but the present invention is not limited thereto. In other embodiments, the number of nanowires 120 may be modified, and the height or growth direction of the nanowires 120 may also be variously modified.

Referring to FIG. 4, an insulating layer 130 covering the first conductive layer 110 on which the nanowires 120 are formed is formed. The insulating layer 130 may be formed by depositing an oxide film or a nitride film.

Referring to FIG. 5, the upper portion of the insulating layer 130 is removed until the top surface of the nanowire 120 is exposed. The removal process of the insulating layer 130 may be performed by chemical mechanical polishing (CMP) or etchback.

In this embodiment, since all the nanowires 120 are formed at the same height, the top surfaces of all the nanowires 120 are exposed by the insulating layer 130 removing process. However, as described above, when the heights of the nanowires 120 are different from each other, the process of removing the insulating layer 130 may be performed until the upper surface of some of the relatively high heights of the nanowires 120 is exposed. As a result, the remaining portion having a relatively low height may be covered with the insulating layer 130 so that the upper surface thereof may not be exposed. Generalizing this is as follows.

When a total of N nanowires are formed on the lower electrode 110, the nanowires are grouped in the order of height so that the first nanowire group, the second nanowire group, ..., the t-th nanowire group (t ≦ It is called N). Wherein each group of nanowires comprises one or more nanowires. The removal process of the insulating layer 130 may be performed until only the t-th nanowire group is exposed, or may be performed until the t-th to ti-th nanowire group 1≤i≤t-1. .

As a result, the number of exposed nanowires 120 may be adjusted by adjusting the thickness at which the insulating layer 130 is removed during the removal process of the insulating layer 130. Since the exposed nanowires 120 are directly connected to the upper electrode and become conductive filament regions by a subsequent process, the size or position of the conductive filaments may be further controlled through the removal process of the insulating layer 130.

Referring to FIG. 6, a second conductive layer 140 for forming a second electrode is formed on the process resultant of FIG. 5.

Subsequently, although not shown, the device as shown in FIG. 1 may be obtained by patterning the first conductive layer 110, the insulating layer 130 having the nanowires 120, and the second conductive layer 140. have.

Hereinafter, with reference to FIG. 7, specific experimental examples of the process of FIG. 3 will be described. In particular, it will be described that nanowires made of tungsten oxide can be formed experimentally.

FIG. 7 is a photograph showing that a tungsten oxide (WO 3) whisker is formed, and shows a result of heat treatment for 15 seconds at a temperature of 950 ° C. in a N 2 atmosphere after depositing tungsten by PVD.

Referring to FIG. 7, it can be seen that a plurality of tungsten oxide whiskers extending in various directions and having a predetermined length are formed. In particular, since the diameter of the tungsten oxide whisker is less than 10nm nm level, such a tungsten oxide whisker can be used as the nanowires described above.

8 and 9 are cross-sectional views illustrating a method of manufacturing a variable resistance memory device according to another exemplary embodiment of the present invention. In describing the present embodiment, the same parts as in the above-described embodiment of FIGS. 2 to 6 will be omitted and detailed descriptions will be made based on differences.

Referring to FIG. 8, a first conductive layer 110 for forming a first electrode is formed on a substrate (not shown) having a predetermined lower structure.

Subsequently, a metal layer 124 is formed on the first conductive film 110. In this case, the metal layer 124 may be the same as the metal layer 122 of FIG. 2 but larger in thickness.

Referring to FIG. 9, when the heat treatment process of the resultant of FIG. 8 is performed at a predetermined temperature (eg, 700 ° C.) or more for several tens of seconds in an oxygen or nitrogen atmosphere, the metal layer 124 is oxidized to the nanowire 120. To grow.

In this case, since the thickness of the metal layer 124 is relatively thick, only the upper portion of the metal layer 124 may be oxidized to be transformed into the nanowire 120, and the lower portion of the metal layer 124 may remain undeformed (see reference numeral 124 ′). . As a result, the nanowire 120 made of the residual metal layer 124 ′ and the metal oxide is formed on the first conductive film 110. The remaining metal layer 124 ′ may function as a lower electrode for applying a voltage to one end of the nanowire 120 together with the first conductive layer 110.

Subsequent processes are substantially the same as those of FIGS. 4 to 6, and thus detailed descriptions thereof will be omitted.

In the present exemplary embodiment, the process of forming the first conductive layer 110 may be omitted. That is, the metal layer 124 may be directly deposited on the substrate (not shown) on which the predetermined lower structure is formed, and the upper portion of the metal layer 124 may be transformed into the nanowire 120. In this case, since the remaining metal layer 124 'functions as a lower electrode, the process step is further reduced.

It is to be noted that the technical spirit of the present invention has been specifically described in accordance with the above-described preferred embodiments, but it is to be understood that the above-described embodiments are intended to be illustrative and not restrictive. In addition, it will be understood by those of ordinary skill in the art that various embodiments are possible within the scope of the technical idea of the present invention.

11: first electrode 12: nanowire
13: insulating layer 14: second electrode

Claims (5)

A first electrode;
A second electrode;
An insulating layer interposed between the first electrode and the second electrode; And
A nanowire connected between the first electrode and the second electrode through the insulating layer, the nanowire including a variable resistance material;
Variable resistance memory device.
The method according to claim 1,
The nanowire is a plurality,
At least one of the nanowires is connected between the first electrode and the second electrode
Variable resistance memory device.
Forming a conductive film for a first electrode on the substrate;
Forming a nanowire made of a variable resistance material on the conductive film for the first electrode;
Forming an insulating layer covering the nanowires on the conductive film for the first electrode;
Removing a portion of the insulating layer to expose the nanowires; And
Forming a conductive film for a second electrode on the partially removed insulating layer;
A method of manufacturing a variable resistance memory device.
The method of claim 3,
The nano wire is a plurality,
Part of removing the insulating layer,
Is performed until at least one of the plurality of nanowires is exposed.
A method of manufacturing a variable resistance memory device.
The method of claim 3,
The nanowire forming step,
Forming a metal layer on the conductive film for the first electrode; And
And heat-treating the resultant in which the metal layer is formed in an oxygen or nitrogen atmosphere to grow the nanowires formed of an oxide of the metal layer.
A method of manufacturing a variable resistance memory device.

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