KR20240037606A - Ovonic threshold switching device and memory device having the ovonic threshold switching device - Google Patents

Abstract

An ovonic threshold switching device is disclosed. The ovonic threshold switching element has first and second electrode layers spaced apart from each other and a switching layer disposed between them, the switching layer being an amorphous chalcogenide-based semiconductor material comprising an alloy made of ZnTe and CrTe. is formed by

Description

OVONIC THRESHOLD SWITCHING DEVICE AND MEMORY DEVICE HAVING THE OVONIC THRESHOLD SWITCHING DEVICE}

The present invention relates to an ovonic threshold switching device based on a reversible switching phenomenon occurring at a metal/amorphous chalcogenide/metal junction and a non-volatile memory device including the same.

The 3D crossbar array structure is a next-generation memory device structure and is expected to become more competitive in the future due to its simple structure and high integration. According to this trend, the development of 3D crossbar array non-volatile memory has recently accelerated. However, such a memory device based on a three-dimensional crossbar structure necessarily requires the introduction of a selection device due to leakage current generated during the memory reading operation.

Meanwhile, in the case of the 1S1R structure among the three-dimensional crossbar structures, the read margin and read window are greatly affected by the difference between V _SET of the memory element and V _TH of the selection element. Therefore, in order to obtain a high read margin and read window, the threshold voltage can be adjusted according to various set voltages depending on the memory material, and the characteristics can be improved when bonded to the memory device. There is a need for research on available selection elements.

One object of the present invention is to provide an ovonic threshold switching device that can stably perform a threshold switching operation by adjusting the threshold voltage and has improved characteristics when bonded to a memory device.

Another object of the present invention is to provide a non-volatile memory device including the ovonic threshold switching device.

The ovonic threshold switching element according to an embodiment of the present invention includes first and second electrode layers spaced apart from each other, and an amorphous chalcolithic layer disposed between the first and second electrode layers and including an alloy made of ZnTe and CrTe. It may include a switching layer formed of a chalcogenide-based semiconductor material.

In one embodiment, the amorphous chalcogenide-based semiconductor material may have the composition of Formula 1 below.

[Formula 1]

(ZnTe) _x (CrTe) _1-x

In Formula 1, 0 < x < 1.

In one embodiment, in Formula 1, 0.3 < x < 0.6.

In one embodiment, the switching layer may be formed through a co-sputtering process using a ZnTe target and a CrTe target.

In one embodiment, the first and second electrodes are independently selected from aluminum (Al), molybdenum (Mo), tungsten (W), titanium (Ti), platinum (Pt), chromium (Cr), and silicon (Si). ), their nitrides, their carbides, and carbon (C)-based materials.

In one embodiment, at least one of the first and second electrodes may have a stacked structure of different materials.

Meanwhile, a non-volatile memory device according to another embodiment of the present invention includes a first signal line and a second signal line spaced apart from each other, a non-volatile memory cell electrically connected to the first signal line, and a non-volatile memory cell electrically connected to the memory cell. A switching element comprising a first electrode connected, a second electrode electrically connected to the second signal line, and a switching layer disposed between the first electrode and the second electrode, wherein the switching layer is made of ZnTe and CrTe. It may be formed of an amorphous chalcogenide-based semiconductor material containing an alloy.

In one embodiment, the amorphous chalcogenide-based semiconductor material may have the composition of Formula 1 below.

[Formula 1]

(ZnTe) _x (CrTe) _1-x

In Formula 1, 0 < x < 1.

In one embodiment, in Formula 1, 0.3 < x < 0.6.

In one embodiment, the first and second electrodes are independently selected from aluminum (Al), molybdenum (Mo), tungsten (W), titanium (Ti), platinum (Pt), chromium (Cr), and silicon (Si). ), their nitrides, their carbides, and carbon (C)-based materials.

In one embodiment, the first signal line may extend in a first direction, and the second signal line may extend in a second direction intersecting the first direction.

In one embodiment, the memory cell may include Phase change Random Access Memory (PRAM) or Resistive switching Random Access Memory (RRAM).

According to the present invention, by implementing an ovonic threshold switching element with an amorphous chalcogenide-based semiconductor material containing ZnTe-CrTe alloy, the threshold voltage can be adjusted according to various set voltages depending on the memory material. As a result, leakage current of memory devices can be suppressed through improved read margin and read window.

Therefore, it can exhibit excellent reliability and uniformity characteristics when driving memory elements, and can be applied to all fields where non-volatile memory is used, such as personal computers and data centers.

FIG. 1A is a cross-sectional view illustrating an ovonic threshold switching device according to an embodiment of the present invention.
Figure 1b is a perspective view for explaining an ovonic threshold switching device according to an embodiment of the present invention.
Figure 2 is a schematic diagram illustrating a method of manufacturing an ovonic threshold switching element according to an embodiment of the present invention.
Figure 3 is a voltage-current graph measured for the ovonic threshold switching device of Example 1 and Comparative Examples 1 and 2.
Figure 4 is a graph showing the threshold voltage (V _TH ) measured for the ovonic threshold switching device of Example 1 and Comparative Examples 1 and 2.
Figure 5 is a graph measuring I _on and I _off changes according to the DC cycle for the ovonic threshold switching devices of Example 1 and Comparative Examples 1 and 2.
Figure 6 is a voltage-current graph measured for an ovonic threshold switching device manufactured by differently adjusting the composition ratio of CrTe and ZnTe when forming a CrTe-ZnTe alloy.
Figure 7 is a perspective view to explain a non-volatile memory device according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. Since the present invention can be subject to various changes and can have various forms, specific embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention. While describing each drawing, similar reference numerals are used for similar components. In the attached drawings, the dimensions of the structures are enlarged from the actual size for clarity of the present invention.

The terms used in this application are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, or a combination thereof described in the specification, but are not intended to indicate the presence of one or more other features or numbers. It should be understood that this does not exclude in advance the possibility of the existence or addition of steps, operations, components, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and unless explicitly defined in the present application, should not be interpreted in an ideal or excessively formal sense. No.

FIG. 1A is a cross-sectional view illustrating an Ovonic threshold switching device according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view showing an Ovonic threshold switching device according to an embodiment of the present invention. This is a perspective view for explanation.

Referring to FIGS. 1A and 1B, the ovonic threshold switching element 100 according to an embodiment of the present invention includes a first electrode 110, a second electrode 120, and a switching layer 130.

The first and second electrodes 110 and 120 may be spaced apart from each other and may be made of an electrically conductive material. For example, the first and second electrodes 110 and 120 are independently formed of aluminum (Al), molybdenum (Mo), tungsten (W), titanium (Ti), platinum (Pt), chromium (Cr), It may be formed of one or more materials selected from the group consisting of silicon (Si), their nitrides or carbides, and carbon (C)-based materials. The carbon-based material may include graphite, carbon nanotubes, graphene, etc. Meanwhile, the material forming the first electrode 110 and the material forming the second electrode 120 may be the same or different from each other. Additionally, the first electrode layer 110 or the second electrode layer 120 may have a stacked structure of different materials among the above materials.

The switching layer 130 may be formed of an amorphous chalcogenide-based semiconductor material containing an alloy made of ZnTe and CrTe.

In one embodiment, the switching layer 130 may be formed of an amorphous chalcogenide-based semiconductor material having the composition of Formula 1 below.

[Formula 1]

(ZnTe) _x (CrTe) _1-x

In Formula 1, 0 < x < 1.

In one embodiment, when the switching layer 130 is formed of a material having the composition of Formula 1, as the molar ratio of ZnTe (x in Formula 1) of the switching layer 130 increases, the switching element 100 The threshold voltage of increases and I _off may decrease. Therefore, according to the present invention, the threshold voltage is adjusted by appropriately adjusting the composition ratio of ZnTe and CrTe of the amorphous chalcogenide-based semiconductor material forming the switching layer 130 and has various set voltages (V _set ). Bonding properties with memory elements can be improved. Preferably, x in Formula 1 may be a molar ratio of 0.3 < x < 0.6.

In one embodiment, the switching layer 130 may be manufactured through a co-sputtering process using a ZnTe target and a CrTe target simultaneously, or a general sputtering process using the targets.

Below, some embodiments of the present invention will be described in detail. However, the following examples are only some examples of the present invention and should not be construed as limiting the scope of the present invention to the following examples.

[Example 1]

After spin coating a photoresist (PR) on a 75 nm thick TiN lower electrode, UV was irradiated using a mask aligner. Afterwards, the photoresist (PR) was stripped and patterning was performed to form the MIM structure.

Next, ZnTe A 30 nm thick ZnTe-CrTe alloy thin film was formed through an RF magnetron co-sputtering process using a target and a CrTe target, and then a DC magnetron sputtering process using a Ti metal target was performed on the alloy thin film under a nitrogen atmosphere. A 100-nm-thick TiN upper electrode was formed through a 100-nm-thick TiN upper electrode, and the photoresist (PR) was removed through a lift-off method to manufacture an ovonic threshold switching device. (See Figure 2) The manufactured switching element has an area of approximately 220 nm x 220 nm.

[Comparative Example 1]

The same patterning process as Example 1 was performed on a 75 nm thick TiN lower electrode, and the ZnTe After forming a single ZnTe thin film with a thickness of 30 nm through an RF magnetron sputtering process using a target, a TiN upper electrode with a thickness of 100 nm was formed on it in the same manner as in Example 1, and the photoresist (PR) was removed through a lift-off method. Thus, an ovonic threshold switching device was manufactured.

[Comparative Example 2]

The same patterning process as Example 1 was performed on a 75 nm thick TiN lower electrode, and CrTe After forming a single CrTe thin film with a thickness of 30 nm through an RF magnetron sputtering process using a target, a 100 nm thick TiN upper electrode was formed on it in the same manner as in Example 1, and the photoresist (PR) was removed through a lift-off method. Thus, an ovonic threshold switching device was manufactured.

[Experimental Example 1]

Figure 3 is a voltage-current graph measured for the ovonic threshold switching device of Example 1 and Comparative Examples 1 and 2. The graph in Figure 3 is the result measured by increasing the voltage from 0V to +3V, then decreasing the voltage again to 0V, then further decreasing the voltage to -3V, and then increasing the voltage to 0V.

Referring to FIG. 3, in the case of Comparative Example 1 device (a) including a single ZnTe thin film, the threshold voltage (V _TH ) was measured to be 1.1 V, the sustain voltage (V _H ) was measured to be 0.7 V, and the device included a single CrTe thin film. In the case of device (c) of Comparative Example 2, the measured results can be confirmed as the threshold voltage (V _TH ) of 0.6V and the maintenance voltage (V _H ) of 0.5V. On the other hand, in the case of the ZnTe-CrTe alloy thin film device (b) according to Example 1 of the present invention, the threshold voltage (V _TH ) was measured to be 0.7V and the sustain voltage (V _H ) was measured to be 0.5V. Through these results, it was confirmed that the threshold voltage (V _TH ) of the switching element can be appropriately adjusted through the ZnTe-CrTe alloy thin film.

[Experimental Example 2]

Figure 4 is a graph showing the threshold voltage (V _TH ) measured for the ovonic threshold switching device of Example 1 and Comparative Examples 1 and 2, and Figure 5 is a graph showing the ovonic threshold switching device of Example 1 and Comparative Examples 1 and 2. This is a graph measuring the I _on and I _off changes according to the DC cycle for the device.

Referring to FIG. 4, the difference in threshold voltage (V _Th ) of the ovonic threshold switching elements of Example 1 ((CrTe) _0.43 - (ZnTe) _0.57 ), Comparative Example 1 (ZnTe), and Comparative Example 2 (CrTe) is You can check it.

Meanwhile, referring to FIG. 5, I _off is 10 nA for the device of Comparative Example 1 including a single ZnTe thin film, and 50 μA for the device of Comparative Example 2 including a single CrTe thin film. In Example 1 of the present invention, I off is 10 nA. In the case of the ZnTe-CrTe alloy thin film device, it can be confirmed that it is about 5 μA. Looking at these results, it can be seen that the threshold voltage (V _Th ) and I _off can be appropriately adjusted through ZnTe and CrTe alloy thin films.

[Experimental Example 3]

Figure 6 is a voltage-current graph measured for an ovonic threshold switching device manufactured by differently adjusting the composition ratio of CrTe and ZnTe when forming a CrTe-ZnTe alloy.

Looking at Figure 6, compared to the ovonic threshold switching element formed of (CrTe) _0.68 (ZnTe) _0.32 alloy, the threshold voltage (V _Th ) of the ovonic threshold switching element formed of (CrTe) _0.43 (ZnTe) _0.57 alloy increases. , I _off can confirm the decreasing result.

In addition, compared to the results of the ovonic threshold switching devices of Comparative Examples 1 and 2, which were composed of a single ZnTe thin film and a single CrTe thin film, respectively, as the ZnTe molar ratio of the switching layer increases, the threshold voltage (V _TH ) increases, I _off showed a decreasing trend.

Figure 7 is a perspective view to explain a non-volatile memory device according to an embodiment of the present invention.

Referring to FIG. 7, a non-volatile memory device 1000 according to an embodiment of the present invention includes a memory cell 1100, a switching device 1200, a first signal line 1300, and a second signal line 1400. do. The memory cell 1100 and the switching element 1200 may be disposed between the first signal line 1300 and the second signal line 1400.

The memory cell 1100 may include PRAM (Phase change Random Access Memory), RRAM (Resistive switching Random Access Memory), etc., which have non-volatile characteristics, and its structure or material is not particularly limited. . The memory cell 1100 may be electrically connected to the first signal line 1300.

The switching element 1200 may include a first electrode 1210, a second electrode 1220, and a switching layer 1230. The first electrode 1210, the second electrode 1220, and the switching layer 1230 of the switching element 1200 are the first electrode 110 and the second electrode 1230 of the ovonic threshold switching element 100 described with reference to FIG. 1. Since they are substantially the same as the two electrodes 120 and the switching layer 130, detailed detailed descriptions thereof will be omitted below.

The switching element 1200 may be disposed between the memory cell 1100 and the second signal line 1400, and the first electrode 1210 of the switching element 1200 is connected to the memory cell 1100 and the second signal line 1400. It may be electrically connected, and the second electrode 1220 of the switching element 1200 may be electrically connected to the second signal line 1400.

The first signal line 1300 and the second signal line 1400 may extend in a direction that intersects each other. For example, the first signal line 1300 may extend in a first direction (X), and the second signal line 1400 may extend in a second direction (Y) perpendicular to the first direction. You can.

Meanwhile, in FIG. 7, the first signal line 1300 is shown as being electrically connected to one memory cell 1100 and the second signal line 1400, but the first signal line 1300 is connected to the second signal line 1400. It may be electrically connected to a plurality of memory cells arranged in a row along the second direction (Y). And in FIG. 7, the second signal line 1400 is shown as being electrically connected to one switching element 1200, but the second signal line 1400 is arranged in a row along the first direction (X). It can be electrically connected to a plurality of switching elements.

In the conventional non-volatile memory device with a three-dimensional crossbar array structure, the memory cell is a two-terminal device and is influenced by sneak current from adjacent peripheral memory cells, etc. to read the information stored in the memory cell. There was a problem that caused an error in the process.

However, as in the present invention, when applying the switching element 1200 that performs an ovonic threshold switching operation, interference with adjacent peripheral memory cells is minimized to eliminate the influence of the sneak current. When programming the memory cell 1100, a high current can be passed to enable programming.

According to the present invention, by implementing an ovonic threshold switching element with an amorphous chalcogenide-based semiconductor material containing ZnTe-CrTe alloy, the threshold voltage can be adjusted according to various set voltages depending on the memory material. As a result, leakage current of memory devices can be suppressed through improved read margin and read window.

Therefore, it can exhibit excellent reliability and uniformity characteristics when driving memory elements, and can be applied to all fields where non-volatile memory is used, such as personal computers and data centers.

Although the present invention has been described above with reference to preferred embodiments, those skilled in the art can make various modifications and changes to the present invention without departing from the spirit and scope of the present invention as set forth in the following patent claims. You will understand that it is possible.

100: ovonic threshold switching element 110, 1210: first electrode
120, 1220: second electrode 130, 1230: switching layer
1000: non-volatile memory element 1100: memory cell
1200: switching element 1300: first signal line
1400: 2nd signal line

Claims (12)

first and second electrode layers spaced apart from each other; and
Disposed between the first and second electrode layers, comprising a switching layer formed of an amorphous chalcogenide-based semiconductor material containing an alloy made of ZnTe and CrTe,
Ovonic threshold switching element. According to paragraph 1,
The amorphous chalcogenide-based semiconductor material is an ovonic threshold switching device, characterized in that it has the composition of the following formula (1):
[Formula 1]
(ZnTe) _x (CrTe) _1-x
In Formula 1, 0 < x < 1. According to paragraph 2,
In Formula 1, characterized in that 0.3 < x < 0.6,
Ovonic threshold switching element. According to paragraph 2,
An ovonic threshold switching device, wherein the switching layer is formed through a co-sputtering process using a ZnTe target and a CrTe target. According to paragraph 1,
The first and second electrodes are independently selected from aluminum (Al), molybdenum (Mo), tungsten (W), titanium (Ti), platinum (Pt), chromium (Cr), silicon (Si), and nitrides thereof, An ovonic threshold switching element, characterized in that it is formed of one or more materials selected from the group consisting of carbides and carbon (C)-based materials. According to clause 5,
An ovonic threshold switching element, characterized in that at least one of the first and second electrodes has a stacked structure of different materials. a first signal line and a second signal line spaced apart from each other;
a non-volatile memory cell electrically connected to the first signal line; and
A switching element including a first electrode electrically connected to the memory cell, a second electrode electrically connected to the second signal line, and a switching layer disposed between the first electrode and the second electrode,
A non-volatile memory device, wherein the switching layer is formed of an amorphous chalcogenide-based semiconductor material containing an alloy made of ZnTe and CrTe. In clause 7,
A non-volatile memory device, characterized in that the amorphous chalcogenide-based semiconductor material has the composition of the following formula (1):
[Formula 1]
(ZnTe) _x (CrTe) _1-x
In Formula 1, 0 < x < 1. According to clause 8,
In Formula 1, characterized in that 0.3 < x < 0.6,
Non-volatile memory device. In clause 7,
The first and second electrodes are independently selected from aluminum (Al), molybdenum (Mo), tungsten (W), titanium (Ti), platinum (Pt), chromium (Cr), silicon (Si), and nitrides thereof, A non-volatile memory device, characterized in that it is formed of one or more materials selected from the group consisting of carbides and carbon (C)-based materials. In clause 7,
The first signal line extends in a first direction, and the second signal line extends in a second direction intersecting the first direction. In clause 7,
A non-volatile memory device, wherein the memory cell includes PRAM (Phase change Random Access Memory) or RRAM (Resistive switching Random Access Memory).