TWI743591B - Resistive random access memory - Google Patents

Abstract

A resistive random access memory including first and second electrodes, a resistance variable layer, first and second metal layers and a resistance stabilizing layer is provided. The second electrode is disposed on the first electrode. The resistance variable layer is disposed between the first and second electrodes. The first metal layer is disposed between the resistance variable layer and the second electrode. The second metal layer is disposed between the first metal layer and the second electrode. The resistance stabilizing layer is disposed between the first and second metal layers. The oxygen content of the resistance variable layer is higher than that of the first metal layer, the oxygen content of the first metal layer is higher than that of the resistance stabilizing layer, the oxygen content of the resistance stabilizing layer is higher than that of the second metal layer.

Description

Resistive random access memory

The present invention relates to a memory, and more particularly to a resistive random access memory (RRAM).

RRAM has the advantages of fast operation speed and low power consumption, and has become a non-volatile memory that has been widely studied in recent years. However, RRAM has an increasing probability that it is difficult to return to a high resistance state after multiple SET/RESET cycle operations, which limits the durability and data retention capability. Therefore, how to improve the durability and data retention capability of RRAM is a goal that the industry is actively pursuing.

The present invention provides a resistive random access memory, which has good durability, reset characteristics and data retention capabilities.

The resistive random access memory of the present invention includes a first electrode, a second electrode, a variable resistance layer, a first metal layer, a second metal layer, and a resistance stabilizing layer. The second electrode is disposed on the first electrode. The variable resistance layer is disposed on the first electrode and the second electrode between. The first metal layer is disposed between the variable resistance layer and the second electrode. The second metal layer is disposed between the first metal layer and the second electrode. The resistance stabilizing layer is disposed between the first metal layer and the second metal layer. The oxygen content of the variable resistance layer is higher than the oxygen content of the first metal layer, the oxygen content of the first metal layer is higher than the oxygen content of the resistance stabilizing layer, and the oxygen content of the resistance stabilizing layer is higher than the oxygen content of the second metal layer.

Based on the above, the resistive random access memory proposed by the present invention includes a first electrode, a second electrode, a variable resistance layer, a first metal layer, a second metal layer, and a resistance stabilizing layer, wherein the resistance of the variable resistance layer The oxygen content is higher than the oxygen content of the first metal layer, the oxygen content of the first metal layer is higher than the oxygen content of the resistance stabilizing layer, and the oxygen content of the resistance stabilizing layer is higher than the oxygen content of the second metal layer. The random access memory undergoes multiple set/reset cycles, which causes damage to the variable resistance layer, resulting in additional oxygen vacancies (ie defects). When the resistive random access memory performs a reset operation, the first metal There are enough oxygen ions in the layer to quickly enter the variable resistance layer, so that the variable resistance layer can be smoothly converted to a high resistance state (High Resistance State, HRS). In this way, the resistive random access memory of the present invention can have good durability, reset characteristics and data retention capabilities.

In order to make the above-mentioned features and advantages of the present invention more comprehensible, the following specific embodiments are described in detail in conjunction with the accompanying drawings.

100: Resistive random access memory

102: first electrode

104: second electrode

106: variable resistance layer

108: The first metal layer

110: Resistance stabilization layer

112: second metal layer

114: barrier layer

FIG. 1 is a diagram of a resistive random access memory according to an embodiment of the present invention Schematic cross-section.

2 is a schematic diagram showing the distribution of oxygen content of a resistive random access memory according to an embodiment of the present invention as a function of position.

Hereinafter, exemplary embodiments of the present invention will be described more fully with reference to the accompanying drawings; however, the present invention may be embodied in different forms and is not limited to the embodiments set forth herein.

FIG. 1 is a schematic cross-sectional view of a resistive random access memory according to an embodiment of the present invention. 2 is a schematic diagram showing the distribution of oxygen content of a resistive random access memory according to an embodiment of the present invention as a function of position.

1, the resistive random access memory 100 includes a first electrode 102, a second electrode 104, a variable resistance layer 106, a first metal layer 108, a resistance stabilizing layer 110, a second metal layer 112, and a barrier layer 114.

The material of the first electrode 102 is not particularly limited, and any conductive material can be used. For example, the material of the first electrode 102 may be titanium nitride (TiN), tantalum nitride (TaN), titanium aluminum nitride (TiAlN), titanium tungsten (TiW) alloy, tungsten (W), ruthenium (Ru) , Platinum (Pt), iridium (Ir), graphite, or a mixture or laminate of the above materials, among which titanium nitride, tantalum nitride, platinum, iridium, graphite or a combination thereof is preferred. The method of forming the first electrode 102 is not particularly limited, and common ones are physical vapor deposition (PVD) or chemical vapor deposition (CVD). The thickness of the first electrode 102 is also not particularly limited, but is usually between 5 nanometers (nm) and 500 nanometers.

The second electrode 104 is disposed on the first electrode 102. The material of the second electrode 104 is not particularly limited, and any conductive material can be used. For example, the material of the second electrode 104 may be titanium nitride (TiN), tantalum nitride (TaN), titanium aluminum nitride (TiAlN), titanium tungsten (TiW) alloy, tungsten (W), ruthenium (Ru) , Platinum (Pt), iridium (Ir), graphite, or a mixture or laminate of the above materials, among which titanium nitride, tantalum nitride, platinum, iridium, graphite or a combination thereof is preferred. The method for forming the second electrode 104 is not particularly limited, and common ones are physical vapor deposition, chemical vapor deposition, or atomic layer deposition. The thickness of the second electrode 104 is also not particularly limited, but is usually between 5 nm and 500 nm.

The variable resistance layer 106 is disposed between the first electrode 102 and the second electrode 104. The material of the variable resistance layer 106 is not particularly limited, and any material that can change its own resistance through the application of voltage can be used. In this embodiment, the material of the variable resistance layer 106 includes, for example, hafnium oxide (HfO ₂ ), tantalum oxide (Ta ₂ O ₅ ), titanium oxide (TiO ₂ ), magnesium oxide (MgO), nickel oxide (NiO), Niobium oxide (Nb ₂ O ₅ ), aluminum oxide (Al ₂ O ₃ ), vanadium oxide (V ₂ O ₅ ), tungsten oxide (WO ₃ ), zinc oxide (ZnO), or cobalt oxide (CoO). In detail, the variable resistance layer 106 may have the following characteristics: when a positive bias is applied to the resistive random access memory 100, oxygen ions are attracted away from the variable resistance layer 106 by the positive bias, and oxygen vacancies are generated. vacancy), forming a filament structure and presenting a conducting state. At this time, the variable resistance layer 106 is converted from a high resistance state (High Resistance State, HRS) to a low resistance state (Low Resistance State, LRS); and when a negative bias is applied In the resistive random access memory 100, oxygen ions will enter the variable resistance layer 106, breaking the filament structure and presenting a non-conducting state. At this time, the variable resistance layer 106 is converted from LRS to HRS. Generally speaking, the conversion of the variable resistance layer 106 from HRS to LRS is referred to as a set (hereinafter referred to as SET) operation, and the conversion of the variable resistance layer 106 from LRS to HRS is referred to as a reset (hereinafter referred to as RESET) operation. In addition, in this embodiment, the oxygen content of the variable resistance layer 106 may be about 75 atomic percent (at%) to about 100 atomic percent. In an embodiment, the variable resistance layer 106 may be formed by a physical vapor deposition method or a chemical vapor deposition method. In another embodiment, considering that the thickness of the variable resistance layer 106 usually needs to be limited to a very thin range (for example, 2 nm to 10 nm), it can be formed by atomic layer deposition.

The first metal layer 108 is disposed between the variable resistance layer 106 and the second electrode 104. In this embodiment, the material of the first metal layer 108 may be a material that is easier to bond with oxygen than the variable resistance layer 106. In this way, when the resistive random access memory 100 performs a SET operation, the oxygen ions in the variable resistance layer 106 will enter the first metal layer 108 when attracted by the positive bias voltage to leave the variable resistance layer 106; When the resistive random access memory 100 performs a RESET operation, the oxygen ions in the first metal layer 108 will return to the variable resistance layer 106.

As shown in FIG. 2, the oxygen content of the variable resistance layer 106 is higher than the oxygen content of the first metal layer 108. In this embodiment, the oxygen content of the first metal layer 108 may be about 70 atomic percent (at%) to about 85 atomic percent. The oxygen content passing through the first metal layer 108 is within the aforementioned range, thereby enhancing the ability of oxygen ions to return to the variable resistance layer 106.

In this embodiment, the material of the first metal layer 108 may include an incompletely oxidized metal oxide. In other words, the first metal layer 108 itself is a metal layer containing oxygen ions. In this way, when the resistive random access memory 100 performs a RESET operation, enough oxygen ions in the first metal layer 108 can enter the variable resistance layer 106, because the first metal layer 108 contains oxygen ions from the variable resistance layer. 106 oxygen ions and its own oxygen ions. Specifically, in this embodiment, the material of the first metal layer 108 may include, for example, TiO _2-x , HfO _2-x or TaO _2-x , where x is 0.2 to 0.7.

In this embodiment, the method for forming the first metal layer 108 may include the following steps: after a metal material layer (not shown) is formed on the variable resistance layer 106, the metal material layer is doped with oxygen ions. The material of the metal material layer may include titanium (Ti), hafnium (Hf), or tantalum (Ta). The method for forming the metal material layer is not particularly limited, and common ones are physical vapor deposition or chemical vapor deposition. The method for doping the metal material layer with oxygen ions is, for example, an ionized metal plasma (IMP) method or a thermal diffusion method. In the embodiment in which the metal material layer is doped with oxygen ions by the ionized metal plasma method, the doping energy of the oxygen ions is greater than about 7 kV to less than about 10 kV, whereby the oxygen ions are only doped to the variable resistor. The metal material layer on the layer 106 is not doped to the variable resistance layer 106. In the embodiment of doping the metal material layer with oxygen ions by the thermal diffusion method, the process temperature is about 250° C. to about 400° C., and the dopant concentration (that is, the oxygen ion concentration) is about 10E3/cm ² to about 10E5/cm2. cm ² , whereby oxygen ions are only doped to the metal material layer on the variable resistance layer 106, but not to the variable resistance layer 106.

In addition, in this embodiment, the thickness of the first metal layer 108 is, for example, about 10 nanometers to about 50 nanometers. The thickness of the penetrating first metal layer 108 is within the aforementioned range In this way, when the resistive random access memory 100 performs a RESET operation, oxygen ions can quickly enter the variable resistance layer 106 to improve the reset characteristic.

The resistance stabilizing layer 110 is disposed between the first metal layer 108 and the second electrode 104. In this embodiment, the resistance stabilizing layer 110 can be used to block the oxygen ions in the first metal layer 108 from diffusing to the second metal layer 112 (related description will be described below) to avoid unstable resistance. In this embodiment, the thickness of the resistance stabilizing layer 110 is, for example, about 0.3 nanometers to about 10 nanometers. In this embodiment, the method for forming the resistance stabilizing layer 110 is, for example, a chemical vapor deposition method, a physical vapor deposition method, or an atomic layer deposition method. In this embodiment, the resistance value of the resistance stabilizing layer 110 is, for example, about 0.5 ohm to 5 ohm.

As shown in FIG. 2, the oxygen content of the first metal layer 108 is higher than the oxygen content of the resistance stabilizing layer 110. In this embodiment, the oxygen content of the resistance stabilizing layer 110 may be about 20 atomic percent (at%) to about 60 atomic percent. The oxygen content passing through the resistance stabilizing layer 110 is within the aforementioned range, so that the amount of oxygen ions diffused to the second metal layer 112 can be controlled. In this embodiment, the material of the resistance stabilizing layer 110 may include metal oxynitride, for example. Specifically, the metal oxynitride includes, for example, tantalum oxynitride, hafnium oxynitride, or titanium oxynitride. In addition, in this embodiment, the nitrogen content of the resistance stabilizing layer 110 may be about 30 atomic percent (at%) to about 50 atomic percent.

The second metal layer 112 is disposed between the resistance stabilizing layer 110 and the second electrode 104. In detail, as shown in FIG. 1, the second metal layer 112 is disposed between the first metal layer 108 and the second electrode 104, and the resistance stabilizing layer 110 is disposed between the first metal layer 108 and the second metal layer 112 .

In this embodiment, the material of the second metal layer 112 may include Ta, Hf, or Ti, for example. In this embodiment, the thickness of the second metal layer 112 is, for example, about 10 nanometers to about 50 nanometers. In this embodiment, the method for forming the second metal layer 112 is, for example, a physical vapor deposition method. As shown in FIG. 2, the oxygen content of the resistance stabilizing layer 110 is higher than the oxygen content of the second metal layer 112. In this embodiment, the oxygen content of the second metal layer 112 may be about 10 atomic percent (at%) to about 40 atomic percent. The oxygen content passing through the second metal layer 112 is within the aforementioned range, so that the oxygen content of the first metal layer 108 can be adjusted. It is worth mentioning that in the process of forming the second metal layer 112 by physical vapor deposition, oxygen usually still enters. Therefore, even if the second metal layer 112 to be formed is a pure metal layer (such as a Ta layer, Hf layer or Ti layer), the formed second metal layer 112 will still contain oxygen.

In addition, in this embodiment, the atomic number of the metal in the second metal layer 112 may be greater than the atomic number of the metal in the first metal layer 108. At this time, the oxygen affinity of the metal in the second metal layer 112 is smaller than the oxygen affinity of the metal in the first metal layer 108. In this way, when the resistive random access memory 100 performs the RESET operation, in addition to the resistance stabilizing layer 110 preventing the oxygen ions in the first metal layer 108 from diffusing to the second metal layer 112, the choice of materials can further reduce The second metal layer 112 attracts oxygen ions. For example, in one embodiment, when the material of the second metal layer 112 includes Ta, the material of the first metal layer 108 may be TiO _2-x or HfO _2-x ; in another embodiment, when the The material of the second metal layer 112 includes Hf, and the material of the first metal layer 108 may be TiO _2-x .

In addition, as mentioned above, in the resistive random access memory 100, The oxygen content of the variable resistance layer 106 is higher than the oxygen content of the first metal layer 108, the oxygen content of the first metal layer 108 is higher than the oxygen content of the resistance stabilizing layer 110, and the oxygen content of the resistance stabilizing layer 110 is higher than that of the second metal The oxygen content of the layer 112, whereby the variable resistance layer 106, the first metal layer 108, the resistance stabilizing layer 110, and the second metal layer 112 together form an oxygen content gradient, as shown in FIG. 2. The resistive random access memory 100 has an oxygen content gradient, whereby when the resistive random access memory 100 performs a RESET operation, oxygen ions in the first metal layer 108 can quickly enter the variable resistance layer 106, and Even if the resistive random access memory 100 undergoes multiple SET/RESET cycle operations, the variable resistance layer 106 is damaged and additional oxygen vacancies (ie defects) are generated, when the resistive random access memory 100 performs a RESET operation , The first metal layer 108 can provide enough oxygen ions to enter the variable resistance layer 106 to break the filament structure and assume a non-conducting state, that is, to switch to HRS. In this way, the resistive random access memory 100 can have good durability, reset characteristics, and data retention capabilities.

The barrier layer 114 is disposed between the second metal layer 112 and the second electrode 104. In this embodiment, the thickness of the barrier layer 114 is, for example, about 0.5 nanometers to about 5 nanometers. In this embodiment, the material of the barrier layer 114 may include, for example, aluminum oxide (Al ₂ O ₃ ), hafnium oxide (HfO ₂ ), or zirconium oxide (ZrO ₂ ). As shown in FIG. 2, the oxygen content of the barrier layer 114 is higher than the oxygen content of the second metal layer 112. In one embodiment, the oxygen content of the barrier layer 114 is lower than the oxygen content of the resistance stabilizing layer 110. In this embodiment, the method for forming the barrier layer 114 is, for example, a chemical vapor deposition method or an atomic deposition method. When the resistive random access memory 100 performs a RESET operation, the barrier layer 114 prevents the oxygen ions in the second metal layer 112 from diffusing to the second electrode 104.

It is worth noting that, as mentioned above, in the resistive random access memory 100, the second electrode 104 is disposed on the first electrode 102, and the variable resistance layer 106 is disposed between the first electrode 102 and the second electrode 104. Meanwhile, the first metal layer 108 is disposed between the variable resistance layer 106 and the second electrode 104, the second metal layer 112 is disposed between the first metal layer 108 and the second electrode 104, and the resistance stabilizing layer 110 is disposed on the first Between the metal layer 108 and the second metal layer 112, and the variable resistance layer 106, the first metal layer 108, the resistance stabilizing layer 110, and the second metal layer 112 together form an oxygen content gradient, thereby resistive random access memory The body 100 can not only perform the SET/RESET cycle operation, even if the resistive random access memory 100 undergoes multiple SET/RESET cycle operations, the variable resistance layer 106 is damaged and additional oxygen vacancies (ie defects) are generated. When the type random access memory 100 performs a RESET operation, enough oxygen ions in the first metal layer 108 can quickly enter the variable resistance layer 106, so that the filament structure is broken and presents a non-conducting state, that is, it switches to HRS . In this way, the resistive random access memory 100 can have good durability, reset characteristics, and data retention capabilities.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the relevant technical field can make some changes and modifications without departing from the spirit and scope of the present invention. The protection scope of the present invention shall be subject to those defined by the attached patent application scope.

100: Resistive random access memory

102: first electrode

104: second electrode

106: variable resistance layer

108: The first metal layer

110: Resistance stabilization layer

112: second metal layer

114: barrier layer

Claims (11)

A resistive random access memory includes: a first electrode; a second electrode arranged on the first electrode; a variable resistance layer arranged between the first electrode and the second electrode; A metal layer disposed between the variable resistance layer and the second electrode, wherein the material of the first metal layer includes TiO _2-x , HfO _2-x or TaO _2-x ; the second metal layer , Configured between the first metal layer and the second electrode; a barrier layer, configured between the second metal layer and the second electrode, wherein the material of the barrier layer is a metal oxide layer , And the oxygen content of the barrier layer is higher than the oxygen content of the second metal layer; and the resistance stabilizing layer is disposed between the first metal layer and the second metal layer, wherein the variable resistor The oxygen content of the layer is higher than the oxygen content of the first metal layer, the oxygen content of the first metal layer is higher than the oxygen content of the resistance stabilizing layer, and the oxygen content of the resistance stabilizing layer is higher than that of the second metal layer. The oxygen content of the metal layer. The resistive random access memory according to the first item of the scope of patent application, wherein the doping energy of oxygen ions in the first metal layer is greater than 7 kV to less than 10 kV. According to the resistive random access memory described in claim 1, wherein the material of the second metal layer includes Ta, Hf or Ti. The resistive random access memory according to the first item of the patent application, wherein the atomic number of the metal in the second metal layer is greater than the atomic number of the metal in the first metal layer. The resistive random access memory described in the first item of the scope of patent application, wherein the material of the resistance stabilizing layer includes metal oxynitride. The resistive random access memory described in the first item of the scope of patent application, wherein the oxygen content of the variable resistance layer is 75 atomic percent (at%) to 100 atomic percent. According to the resistive random access memory described in claim 1, wherein the oxygen content of the first metal layer is 70 atomic percent to 85 atomic percent. In the resistive random access memory described in the first item of the patent application, the oxygen content of the resistance stabilizing layer is 20 atomic percent to 60 atomic percent. According to the resistive random access memory described in claim 1, wherein the oxygen content of the second metal layer is 10 atomic percent to 40 atomic percent. In the resistive random access memory described in item 1 of the scope of patent application, x is 0.2 to 0.7. The resistive random access memory according to the first item of the scope of patent application, wherein the oxygen content of the barrier layer is lower than the oxygen content of the resistance stabilizing layer.

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