TW201545388A - Resistive ram and method of manufacturing the same - Google Patents

Abstract

A resistive RAM and a method of manufacturing the same are provided. The resistive RAM includes a first electrode, a second electrode, and a transition metal oxide (TMO) layer between the first and the second electrodes. The resistive RAM further includes an activated metal layer between the first electrode and the TMO layer, and a metal oxynitride layer which is formed at a surface of the activated metal layer in the gas environment containing nitrogen and oxygen elements.

Description

Resistive random access memory and manufacturing method thereof

The present invention relates to a resistive random access memory (RRAM) technology, and more particularly to a resistive random access memory and a method of fabricating the same.

The resistive random access memory is generally composed of a transition metal oxide (TMO), a top electrode (TE), and a bottom electrode (BE), and the above wires are connected to the lower wires. The resistive random access memory can perform a resistance state of 0 to 1 or 1 to 0 switching by an applied operating voltage/current. Since the conductive path controls the low resistance state (LRS) by oxygen vacancy, once the oxygen ions are diffused into the transition metal oxide layer due to high temperature, the internal oxygen vacancy will be reduced. To make the operation of the memory unstable.

Therefore, there are currently several techniques for reducing the diffusion of oxygen ions into the transition metal oxide, such as increasing the set power, but will affect the yield of the reset. In addition, there is also an oxide layer as a technique for blocking diffusion of oxygen ions, but This will cause an impact on the overall conductivity of the memory.

Among various types of resistive random access memories, the transition metal oxide (TMO) layer is a yttria-type resistive random access memory, which is attracting attention due to its excellent durability and fast switching speed. However, the titanium/yttria (Ti/HfO ₂ ) type resistive random access memory used at present is often difficult to maintain in a low resistance state at a high temperature, causing deterioration of so-called "high temperature data retention capability". In this regard, there is a need to conduct research and improve it.

The invention provides a resistive random access memory, which can improve data persistence and improve electrical conductivity.

The present invention further provides a method of manufacturing a resistive random access memory, which is capable of producing a memory having a good data retention rate and a low operating voltage.

The resistive random access memory of the present invention includes a first electrode, a second electrode, and a transition metal oxide layer interposed between the first and second electrodes. The resistive random access memory further includes an activated metal layer between the first electrode and the transition metal oxide layer and a metal oxynitride layer. The metal oxynitride layer is composed of an oxygen element and a nitrogen element. It is formed on the surface of the activated metal layer in a gaseous environment.

In an embodiment of the invention, the metal oxynitride layer has a thickness of between about 1 nm and 20 nm.

In an embodiment of the invention, the material of the activated metal layer comprises titanium, tantalum, tungsten, niobium, nickel, aluminum, vanadium, cobalt, zirconium or hafnium.

In an embodiment of the invention, the metal oxynitride layer further includes Between the second electrode and the transition metal oxide layer.

In an embodiment of the invention, the first electrode is an upper electrode and the second electrode is a lower electrode.

In an embodiment of the invention, the first electrode is a lower electrode and the second electrode is an upper electrode.

In an embodiment of the invention, the material of the first electrode and the material of the active metal layer may be the same.

In an embodiment of the invention, the resistive random access memory further includes a first buffer layer between the transition metal oxide layer and the metal oxynitride layer. The material of the first buffer layer may be the same as the material of the first electrode.

In an embodiment of the invention, the activated metal layer further includes a second buffer layer located in direct contact with the metal oxynitride layer at the surface.

The method for fabricating a resistive random access memory of the present invention comprises sequentially forming a first electrode, a transition metal oxide layer and a second electrode, and the manufacturing method further comprises forming a first electrode or a transition metal oxide layer. After the step, an activated metal layer is formed, and a metal oxynitride layer is formed on the surface of the activated metal layer in a gas atmosphere containing an oxygen element and a nitrogen element.

In another embodiment of the present invention, the gas is N ₂ O, NO ₂ , NO, N ₂ O ₂ , N ₂ /O ₂ , N ₂ /O ₃ , N ₂ , NH ₃ , O ₂ , H ₂ O, the gas group consisting of H ₂ O ₂ and O ₃ in the selected at least one.

In another embodiment of the present invention, the above method of forming a metal oxynitride layer may also be used in combination with a plasma.

In another embodiment of the present invention, a first buffer layer may be formed on the metal oxynitride layer after forming the metal oxynitride layer.

In another embodiment of the invention, the step of forming the activated metal layer further includes forming a second buffer layer at the surface.

Based on the above, the present invention suppresses oxygen ion diffusion by a metal oxynitride layer formed in a gas atmosphere containing oxygen and nitrogen, thereby improving high temperature data persistence (HTDR) of low resistance state (LRS). Moreover, since the thickness of the metal oxynitride layer of the present invention can be controlled to be extremely thin, the durability of the data can be improved without affecting the conductivity of the memory itself.

The above described features and advantages of the invention will be apparent from the following description.

100, 110, 120, 130, 140‧‧‧ resistive random access memory

102‧‧‧ lower electrode

102a, 107a, 126a, 146a, 204a‧‧‧ surface

104‧‧‧Upper electrode

106, 202‧‧‧Transition of metal oxide layers

107, 126, 146, 204‧‧‧ Activated metal layers

108, 122, 124, 132, 142, 144, 208, 302‧‧‧ metal oxynitride

134‧‧‧First buffer layer

200‧‧‧first electrode

206‧‧‧ gas

210‧‧‧second electrode

300‧‧‧Second buffer layer

T‧‧‧thickness

1A-1E are schematic cross-sectional views of five resistive random access memories in accordance with an embodiment of the present invention.

2A through 2C are cross-sectional views showing a manufacturing process of a resistive random access memory in accordance with another embodiment of the present invention.

3 is a cross-sectional view showing a manufacturing process of a resistive random access memory in accordance with still another embodiment of the present invention.

4 is a graph comparing the data persistence yields of Experimental Example 1 and Comparative Example 1.

Figure 5 is a comparison of the data persistence yields of Experimental Example 1 and Comparative Example 2. Figure.

Fig. 6 is a graph showing the comparison of the standard deviation percentage of the high resistance state of the experimental example 1, the comparative example 1 and the comparative example 2.

The embodiments of the present invention are shown in the accompanying drawings. However, the invention may be practiced in many different forms and should not be construed as being limited to the embodiments described. Rather, the embodiments are provided so that this disclosure will be thorough and complete, and the scope of the invention will be fully conveyed to those of ordinary skill in the art.

In the drawings, the dimensions and relative dimensions of the various layers and regions may be exaggerated for clarity.

1A, 1B, 1C, 1D, and 1E are schematic cross-sectional views of five resistive random access memories, respectively, in accordance with an embodiment of the present invention.

Referring first to FIG. 1A, the resistive random access memory 100 includes a second electrode as the lower electrode 102, a first electrode as the upper electrode 104, and a transition metal oxidation between the first and second electrodes 104 and 102. (TMO) layer 106. The upper electrode 104 (first electrode) and the lower electrode 102 (second electrode) may each be a material layer such as titanium, tantalum, titanium nitride or tantalum nitride, and the material of the transition metal oxide (TMO) layer 106 is Such as HfO _x or other suitable metal oxides. The thicknesses of the upper and lower electrodes 104 and 102 are respectively exemplified, but not limited to, between 10 nm and 100 nm. The thickness of the transition metal oxide (TMO) layer 106 can be exemplified, but not limited to, between 3 nm and 11 nm.

In FIG. 1A, the resistive random access memory 100 further has an activated metal layer 107 and a metal oxynitride layer 108, wherein the activated metal layer 107 is interposed between the upper electrode 104 (first electrode) and the transition. The metal oxide layer 106 is formed on the surface 107a of the activated metal layer 107 in a gas atmosphere containing oxygen and nitrogen to block oxygen ions in the activated metal layer 107. It is diffused to the upper electrode 104 (first electrode). In the present embodiment, the material of the activated metal layer 107 is, for example, titanium (Ti), tantalum (Ta), tungsten (W), hafnium (Hf), nickel (Ni), aluminum (Al), vanadium (V), cobalt. (Co), zirconium (Zr) or bismuth (Si); the thickness of the activated metal layer 107 is between about 5 nm and 45 nm; preferably titanium (Ti) or tantalum (Ta). Since the metal oxynitride layer 108 is formed, a thinner film layer can be obtained than a conventional deposition process using sputtering; for example, the metal oxynitride layer 108 has a thickness t of about 1 nm to 20 nm. between. The atomic ratio of oxygen in the metal oxynitride layer 108 is between about 10% and 60%, and the atomic proportion of nitrogen is between about 15% and 60%.

Next, referring to FIG. 1B, the resistive random access memory 110 shown in the figure has the following electrodes 102 as a first electrode and an upper electrode 104 as a second electrode. Moreover, when the material of the lower electrode 102 (first electrode) is the same as the material of the active metal layer, the metal oxynitride layer 108 may be formed on the surface 102a of the lower electrode 102, that is, the lower electrode 102 of FIG. 1B may simultaneously The first electrode and the activated metal layer are regarded as the active metal layer. At this time, the metal oxynitride layer 108 can be used to block diffusion of oxygen ions in the transition metal oxide layer 106 to the lower electrode 102 (first electrode). For parameters such as material and thickness of other film layers, reference may be made to FIG. 1A.

In the resistive random access memory 120 of FIG. 1C, in combination with FIG. 1A and Figure 1B features. That is, there is a metal oxynitride layer 122 between the upper electrode 104 and the transition metal oxide layer 106, and a metal oxynitride layer 124 between the lower electrode 102 and the transition metal oxide layer 106. The metal oxynitride layer 122 is formed on the surface 126a of the active metal layer 126 in a gas atmosphere containing oxygen and nitrogen. The metal oxynitride layer 124 is also formed in a gas atmosphere containing oxygen and nitrogen. The activated metal layer is the same material as the surface 102a of the electrode 102. Therefore, the transition metal oxide layer 106 of the resistive random access memory 120 is protected by the upper and lower layers of the metal oxynitride layers 122 and 124, and should have a high resistance data durability (HTDR) in the low resistance state (LRS). The effect is better than that of FIGS. 1A and 1B.

As for the resistive random access memory 130 of FIG. 1D, which is close to the structure of FIG. 1B, it has a metal oxynitride layer 132 formed on the surface 102a of the lower electrode 102 in a gas atmosphere containing oxygen and nitrogen, but the difference is The first buffer layer 134 is disposed between the transition metal oxide layer 106 and the metal oxynitride layer 132. The material of the first buffer layer 134 may be the same as the material of the lower electrode 102, so that the transition metal oxide layer 106 can obtain better electrical and thermal conductivity during deposition.

In the resistive random access memory 140 of FIG. 1E, the features of FIGS. 1A and 1D are combined. That is, there is a metal oxynitride layer 142 between the upper electrode 104 and the transition metal oxide layer 106, and a metal oxynitride layer 144 between the lower electrode 102 and the transition metal oxide layer 106. In addition, a first buffer layer 148 is provided between the transition metal oxide layer 106 and the metal oxynitride layer 144. Since the metal oxynitride layer 142 is formed on the surface 146a of the active metal layer 146 in a gas atmosphere containing oxygen and nitrogen, the metal oxynitride layer 144 is also in a gas atmosphere containing oxygen and nitrogen. Since it is formed on the surface 102a of the lower electrode 102, the resistive random access memory 140 has excellent data durability.

The metal oxynitride layer in the above formula is formed in a gas atmosphere containing an oxygen element and a nitrogen element. Therefore, in order to succinctly describe the process of the metal oxynitride layer, the following embodiment only takes the structure of FIG. 1A as an example, and It is applied to the fabrication of the structure of Figures 1B to 1E.

2A through 2C are cross-sectional views showing a manufacturing process of a resistive random access memory in accordance with another embodiment of the present invention.

Referring first to FIG. 2A, after the first electrode 200 and the transition metal oxide layer 202 are sequentially formed, a layer of the activated metal layer 204 is formed. The first electrode 200 is a material layer such as titanium, tantalum, titanium nitride or tantalum nitride, and the material of the metal oxide layer 202 is transformed, such as HfO _x or other suitable metal oxide. As the material of the activated metal layer 204, for example, titanium (Ti), tantalum (Ta), tungsten (W), hafnium (Hf), nickel (Ni), aluminum (Al), vanadium (V), cobalt (Co), zirconium (Zr) or bismuth (Si); preferably titanium (Ti) or tantalum (Ta).

Then, referring to FIG. 2B, a metal oxynitride layer 208 is formed on the surface 204a of the activated metal layer 204 in the atmosphere 206 of the oxygen-containing element and the nitrogen element. In the present embodiment, the gas 206 is, for example, N ₂ O, NO ₂ , NO, N ₂ O ₂ , N ₂ /O ₂ , N ₂ /O ₃ , N ₂ , NH ₃ , O ₂ , H ₂ O, At least one selected from the group consisting of H ₂ O ₂ and O ₃ , the oblique line "/" represents the meaning of simultaneous inclusion. For example, a gas 206 containing an oxygen element and a nitrogen element may be used alone to form the metal oxynitride layer 208, or a different gas 206 such as oxygen (O ₂ ) and nitrogen (N ₂ ) may be simultaneously introduced, but the present invention It is not limited thereto, and different gases 206 may be introduced in order. The foregoing process of introducing the gas 206 may also be combined with or without plasma. The plasma can shorten the reaction time or form a thicker metal oxynitride layer.

Next, referring to FIG. 2C, a second electrode 210 is formed on the metal oxynitride layer 208 to obtain a resistive random access memory as shown in FIG. 1A.

If the resistive random access memory of FIG. 1B is to be formed, it is necessary to form an active metal layer after the step of forming the first electrode (200), and when the first electrode and the active metal layer belong to the same material, this The two layers can be regarded as the same material layer, and then the steps of FIG. 2B are performed to form a metal oxynitride layer. The subsequent steps can be referred to known techniques, and thus will not be described again.

If the resistive random access memory of FIG. 1D is to be formed, the first buffer layer may be formed on the metal oxynitride layer after the metal oxynitride layer is formed. The rest of the steps can be referred to the above technology, and therefore will not be described again.

However, the manufacturing method of the present invention is not limited to the above steps, and a second buffer layer 300 may be formed on the surface 204a of the activated metal layer 204 before forming the metal oxynitride layer, as shown in FIG. Thereafter, a metal oxynitride layer 302 is formed in the atmosphere of a gas 206 containing an oxygen element and a nitrogen element. Therefore, the second buffer layer 300 is located at the surface 204a and is in direct contact with the metal oxynitride 302. The second buffer layer 300 is, for example, an extremely thin TiN layer deposited by sputtering, a TiO _x layer (x<2), a TiN _x O _y layer (x is not 0 and x+y<2), etc. The second buffer layer 300 can slow down the reaction rate of the metal oxynitride 302.

Several experiments are listed below to verify the effects of the present invention, but do not limit the scope of the present invention.

Experimental example 1

A resistive random access memory as shown in FIG. 1A is fabricated, wherein the metal oxynitride layer is titanium oxynitride, and the titanium oxynitride layer is in an oxygen-containing and nitrogen-containing atmosphere at 300 ° C for 5 minutes in the activated metal titanium. A thickness of about 5 nm is formed.

Comparative example 1

A resistive random access memory as in Experimental Example 1 was fabricated, but without a metal oxynitride layer.

Comparative example 2

A resistive random access memory as in Experimental Example 1 was fabricated, but the metal oxynitride layer was changed to an aluminum oxide layer, and the thickness of the alumina was about 1.5 nm.

Result 1: Data persistence

After high-temperature heat treatment (baking), the measurement of the data durability yield was carried out, and the results are shown in Figs. 4 and 5.

As apparent from Fig. 4, the data durability yield of Experimental Example 1 of the present invention was significantly higher than that of Comparative Example 1.

As apparent from Fig. 5, the raw material durability yield of Experimental Example 1 of the present invention was significantly higher than that of Comparative Example 2.

Result 2: Percentage of standard deviation of high resistance current; the lower the standard deviation percentage, the more undisturbed when reading at high temperature.

After high-temperature heat treatment (baking), 21 high-resistance current measurements were performed, and the results are shown in Fig. 6 as a percentage of standard deviation.

6 shows the current standard of the high resistance state of Experimental Example 1 of the present invention. The percentage difference was significantly lower than that of Comparative Example 1 and Comparative Example 2.

In summary, the present invention forms a metal oxynitride layer formed on the surface of the activated metal layer, which not only blocks the diffusion of oxygen ions in the active metal layer to the electrode, but also enhances data persistence, and is also extremely thin. The metal oxynitride layer reduces the impact on the conductivity of the memory.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

100‧‧‧Resistive random access memory

102‧‧‧ lower electrode

104‧‧‧Upper electrode

106‧‧‧Transition of metal oxide layers

107‧‧‧Activating metal layer

107a‧‧‧ surface

108‧‧‧metal oxynitride

T‧‧‧thickness

Claims (15)

A resistive random access memory, comprising a first electrode, a second electrode, and a transition metal oxide layer between the first electrode and the second electrode, the resistive random access memory further comprising: An activated metal layer interposed between the first electrode and the transition metal oxide layer; and a metal oxynitride layer formed on a surface of the activated metal layer in a gas atmosphere containing oxygen and nitrogen. The resistive random access memory according to claim 1, wherein the metal oxynitride layer has a thickness of between 1 nm and 20 nm. The resistive random access memory according to claim 1, wherein the material of the active metal layer comprises titanium, tantalum, tungsten, niobium, nickel, aluminum, vanadium, cobalt, zirconium or hafnium. The resistive random access memory of claim 1, wherein the metal oxynitride layer further comprises between the second electrode and the transition metal oxide layer. The resistive random access memory of claim 1, wherein the first electrode is an upper electrode and the second electrode is a lower electrode. The resistive random access memory of claim 1, wherein the first electrode is a lower electrode and the second electrode is an upper electrode. The resistive random access memory according to claim 6, wherein the material of the first electrode is the same as the material of the active metal layer. The resistive random access memory of claim 6, further comprising a first buffer layer between the transition metal oxide layer and the metal oxynitride layer. The resistive random access memory of claim 6, wherein the material of the first electrode is the same as the material of the first buffer layer. The resistive random access memory of claim 6, wherein the active metal layer further comprises a second buffer layer located at the surface in direct contact with the metal oxynitride layer. A manufacturing method of a resistive random access memory, comprising: sequentially forming a first electrode, a transition metal oxide layer and a second electrode, and the manufacturing method further comprises: forming the first electrode and the transition metal oxide After the step of at least one of the layers, the activated metal layer is formed; and in the gas atmosphere containing the oxygen element and the nitrogen element, a metal oxynitride layer is formed on the surface of the activated metal layer. The method of manufacturing a resistive random access memory according to claim 11, wherein the gas is N ₂ O, NO ₂ , NO, N ₂ O ₂ , N ₂ /O ₂ , N ₂ /O _{3, N 2, NH 3,} O 2, H 2 O, the gas group consisting of H ₂ O ₂ and O ₃ in the selected at least one. The method of manufacturing a resistive random access memory according to claim 11, wherein the method of forming the metal oxynitride layer further comprises using a plasma. Resistive random access memory according to claim 11 of the patent application scope The manufacturing method further comprises: after forming the metal oxynitride layer, forming a first buffer layer on the metal oxynitride layer. The method of manufacturing a resistive random access memory according to claim 11, wherein the step of forming the activated metal layer further comprises forming a second buffer layer at the surface.