CN111987217A - RRAM cell structure and method of making same - Google Patents

Abstract

The invention discloses an RRAM cell structure, which includes a top-to-bottom metal top electrode, an oxide resistance change layer and a metal bottom electrode, the metal bottom electrode forms a convex structure, and the convex part of the convex structure extends into the oxide resistance in the changing layer. The invention also discloses a manufacturing method of the RRAM cell structure. The invention can improve the working stability and retention characteristics of the device by indirectly fixing the conductive channel.

Description

RRAM cell structure and manufacturing method thereof

technical field

The present invention relates to the field of semiconductor manufacturing, in particular to an RRAM cell structure. The invention also relates to a manufacturing method of the RRAM cell structure.

Background technique

With the development of integrated circuits, mobile communications, and the Internet of Things, the demand for non-volatile memory is increasingly shifting to the direction of large capacity, low power consumption, high density and low cost. Metal oxide resistive device is a new type of non-volatile memory with great application potential, and its typical structure is metal electrode-oxide-metal electrode. Under the excitation of an external electric field, the device can undergo a reversible transition between high and low resistance states, and its high and low resistance states can still be maintained after the electric field is removed. The Forming process refers to the process that the RRAM jumps from the initial high-resistance state to the low-resistance state for the first time. On the contrary, the RRAM in the low-resistance state can be converted to the high-resistance state after being excited by a certain voltage, and the low-resistance state jumps. The process to the high resistance state is called Reset. After the Reset process, the RRAM that enters the high-impedance state can also be converted to the low-impedance state by applying voltage excitation, and this process is different from the first high-impedance transition to the low-impedance state, which is called the Set process. However, the operating voltage (Forming, Set, Reset) of the traditional structure RRAM device is too high to meet the maximum voltage limit that the LP 40nm process can provide, and it is difficult to modulate various device characteristics by adjusting a single resistive material layer. , Figure 1 is a schematic diagram of the RRAM cell structure.

The I-V curve of the transition characteristics of RRAM is shown in Figure 2, and its device characteristics include Forming voltage/current, Set&Reset voltage/current, MW (Memory Window) storage window, read and write speed, etc.

The RRAM device based on tantalum oxide TaOx material is a typical metal oxide non-conductive channel. The principle is to realize different resistance states through the on-off of the conductive channel formed by the excitation of lattice oxygen to generate oxygen vacancies, as shown in Figure 3. Show. In the case of an external electric field, the oxygen ions in the resistance switching layer TaOx will move to the interface layer (depending on the polarity) for storage, and a conductive channel formed by oxygen vacancies will appear in TaO2, and the resistance of TaOx will change from a high resistance state. (HRS) becomes the low resistance state (LRS), the resistance of the device completes the transition, and then the reset/set voltage of opposite polarity (generally lower than the Forming voltage) is applied in turn, which can make the oxygen vacancy channel break and form again, which can make the oxygen vacancy channel broken and formed again. The resistive layer changes in HRS and LRS to form a cycle to store 0 and 1; RRAM is integrated in the back stage, and the structure is simple and cost controllable, so it can be used as an embedded storage device and has great commercial potential.

40LP RRAM and below node projects currently use the lower electrode (TaN)/resistive switching layer (TaOx)/upper electrode (TiN) scheme. The tape-out test results show that the working stability, retention characteristics and erasing characteristics of this scheme are The key is that the components of the tantalum oxide resistive layer material formed by oxidation are not very different, resulting in unstable conductive channels. It can be seen that the existing structure and integration scheme have problems of working stability.

SUMMARY OF THE INVENTION

A series of concepts in simplified form are introduced in the summary of the invention, and the concepts in the simplified form are all simplifications of the prior art in the art, which will be further described in detail in the detailed description. The Summary of the Invention section of the present invention is not intended to attempt to limit the key features and essential technical features of the claimed technical solution, nor is it intended to attempt to determine the protection scope of the claimed technical solution.

The technical problem to be solved by the present invention is to provide an RRAM cell structure that can improve working stability and retention characteristics by indirectly fixing conductive channels.

Another technical problem to be solved by the present invention is to provide a manufacturing method of an RRAM cell structure which can improve the working stability and retention characteristics by indirectly fixing the conductive channel.

In order to solve the above technical problems, the RRAM cell structure provided by the present invention includes forming a metal top electrode, an oxide resistive layer and a metal bottom electrode from top to bottom, and the metal bottom electrode forms a convex structure, and the convex part of the convex structure extends. into the oxide resistive layer.

Optionally, to further improve the RRAM cell structure, the oxide resistive layer is nickel oxide (NiO), titanium oxide (TiOx), hafnium oxide (HfOx) or tantalum oxide (TaOx).

Optionally, to further improve the RRAM cell structure, the metal top electrode is tantalum nitride (TaN) or titanium nitride (TiN).

Optionally, to further improve the RRAM cell structure, the metal bottom electrode is tantalum nitride (TaN) or titanium nitride (TiN).

The present invention provides a method for manufacturing an RRAM cell structure, comprising the following steps:

S1, depositing a metal bottom electrode, and etching the metal bottom electrode to form a convex structure;

S2, depositing the metal of the resistive switching layer, and oxidizing to form an oxide resistive switching layer;

S3, grinding and planarizing the top of the oxide resistive layer;

S4, depositing a metal top electrode.

Optionally, in the further described RRAM cell structure manufacturing method, when step S1 is performed, tantalum nitride (TaN) or titanium nitride (TiN) is used to form the metal bottom electrode.

Optionally, in the further described RRAM cell structure manufacturing method, when step S3 is performed, nickel oxide (NiO), titanium oxide (TiOx), hafnium oxide (HfOx) or tantalum oxide (TaOx) are formed by oxidation as the oxide resistive layer .

Optionally, in the further described RRAM cell structure manufacturing method, when step S4 is performed, chemical mechanical polishing is used to planarize the top of the oxide resistive switching layer.

Optionally, in the further described RRAM cell structure manufacturing method, when step S5 is performed, tantalum nitride (TaN) or titanium nitride (TiN) is used to form the metal top electrode.

As shown in Figure 4, the traditional RRAM cell structure is a three-layer structure at both ends-upper electrode/resistance switching layer/lower electrode, the electrode is made of TiN material, and the resistance switching layer is tantalum oxide as an example, the main reason for its poor retention characteristics The reason is that the conduction path is not stable.

The metal bottom electrode of the convex structure of the present invention is titanium nitride TiN, the oxide resistance change layer is tantalum oxide TaOx, the metal upper electrode is titanium nitride TiN, the metal bottom electrode of the convex structure and the resistance change formed by first oxidation and then CMP By utilizing the characteristics of unevenly distributed electric field and the small resistance value of the central oxidation state, the conductive path connecting the active electrode and the lower electrode is formed to be fixed, and then the conductive path of the resistive layer can be fixed, which improves the stability of the resistive memory. and retention characteristics. The reliability and stability of the device can be improved by utilizing the physical structure and the oxidation characteristics to stabilize the conductive channel, and because of the oxidation characteristics, the oxidation parameters can be more conveniently modulated to modulate various parameters of the resistive memory. For example, the initial resistance of RRAM can be adjusted, and the initial resistance of RRAM will significantly affect the storage window. Obtaining a suitable initial resistance by adjusting the process structure can effectively increase the storage window, which is of great significance to the anti-noise characteristics of the circuit.

Description of drawings

The drawings of the present invention are intended to supplement the description in the specification by illustrating the general characteristics of methods, structures and/or materials used in certain exemplary embodiments according to the present invention. However, the drawings of the present invention are schematic representations not to scale and thus may not accurately reflect the precise structural or performance characteristics of any given embodiment, and the drawings of the present invention should not be construed as limiting or limiting by the present invention. The range of values or properties encompassed by the exemplary embodiments. The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments:

FIG. 1 is a schematic diagram of the structure of an RRAM cell.

Fig. 2 is the transition characteristic I-V curve of RRAM.

FIG. 3 is a schematic diagram of the principle of on-off RRAM based on the generation and recombination of oxygen vacancies.

FIG. 4 is a schematic diagram of an RRAM cell structure using traditional tantalum oxide as a resistive switching layer.

Figure 5 is a schematic view of the structure of the present invention.

Figure 6 is a schematic flow chart of the present invention.

Detailed ways

The embodiments of the present invention are described below through specific specific embodiments, and those skilled in the art can fully understand other advantages and technical effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through different specific embodiments, and various details in this specification can also be applied based on different viewpoints, and various modifications or changes can be made without departing from the general design idea of the invention. It should be noted that the following embodiments and features in the embodiments may be combined with each other under the condition of no conflict. The following exemplary embodiments of the present invention may be embodied in many different forms and should not be construed as limited to the specific embodiments set forth herein. It should be understood that these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the technical solutions of these exemplary embodiments to those skilled in the art.

In the first embodiment, as shown in FIG. 5 , the present invention provides an RRAM cell structure, including forming a top metal electrode, an oxide resistive layer and a bottom metal electrode from top to bottom, and the bottom metal electrode forms a convex structure. The convex portion of the shaped structure protrudes into the oxide resistive switching layer.

In the second embodiment, the present invention provides an RRAM cell structure, including forming a top metal electrode, an oxide resistive layer and a bottom metal electrode from top to bottom, wherein the bottom metal electrode forms a convex structure, and the convex portion of the convex structure extends into the oxide resistive layer;

Wherein, the oxide resistive layer is nickel oxide (NiO), titanium oxide (TiOx), hafnium oxide (HfOx) or tantalum oxide (TaOx); the metal top electrode is tantalum nitride (TaN) or titanium nitride (TiN); The metal bottom electrode is tantalum nitride (TaN) or titanium nitride (TiN).

The third embodiment, as shown in FIG. 6 , the present invention provides a method for manufacturing an RRAM cell structure, comprising the following steps:

S1, depositing a metal bottom electrode, and etching the metal bottom electrode to form a convex structure;

S2, depositing the metal of the resistive switching layer, and oxidizing to form an oxide resistive switching layer;

S3, grinding and planarizing the top of the oxide resistive layer;

S4, depositing a metal top electrode.

In the fourth embodiment, the present invention provides a method for manufacturing an RRAM cell structure, comprising the following steps:

S1, tantalum nitride (TaN) is deposited to form a metal bottom electrode, and the metal bottom electrode is etched to form a convex structure;

S2, depositing the resistive layer metal tantalum (Ta), and oxidizing to form a tantalum oxide (TaOx) resistive layer;

S3, chemical mechanical polishing to planarize the top of the tantalum oxide (TaOx) resistive switching layer;

S4, using tantalum nitride (TaN) deposition to fabricate a metal top electrode.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will also be understood that, unless expressly defined herein, terms such as those defined in a general dictionary should be construed to have meanings consistent with their meanings in the relevant art context, rather than ideally or excessively The formal meaning is explained.

The present invention has been described in detail above through specific embodiments and examples, but these are not intended to limit the present invention. Without departing from the principles of the present invention, those skilled in the art can also make many modifications and improvements, which should also be regarded as the protection scope of the present invention.

Claims (9)

1. an RRAM cell structure, comprising forming a metal top electrode, an oxide resistive layer and a metal bottom electrode from top to bottom, it is characterized in that: the metal bottom electrode forms a convex structure, and the convex part of this convex structure extends into the oxidation in the resistive layer. 2 . The RRAM cell structure according to claim 1 , wherein the oxide resistive switching layer is nickel oxide (NiO), titanium oxide (TiOx), hafnium oxide (HfOx) or tantalum oxide (TaOx). 3 . 3. The RRAM cell structure of claim 1, wherein the metal top electrode is tantalum nitride (TaN) or titanium nitride (TiN). 4. The RRAM cell structure of claim 1, wherein the metal bottom electrode is tantalum nitride (TaN) or titanium nitride (TiN). 5. a RRAM cell structure manufacturing method, is characterized in that, comprises the following steps: S1, depositing a metal bottom electrode, and etching the metal bottom electrode to form a convex structure; S2, depositing the metal of the resistive switching layer, and oxidizing to form an oxide resistive switching layer; S3, grinding and planarizing the top of the oxide resistive layer; S4, depositing a metal top electrode. 6 . The method for manufacturing an RRAM cell structure according to claim 5 , wherein when step S1 is performed, tantalum nitride (TaN) or titanium nitride (TiN) is used to form the metal bottom electrode. 7 . 7. The method for manufacturing an RRAM cell structure as claimed in claim 5, wherein when step S3 is implemented, nickel oxide (NiO), titanium oxide (TiOx), hafnium oxide (HfOx) or tantalum oxide (TaOx) are formed by oxidation as oxide resistive layer. 8 . The method for manufacturing an RRAM cell structure according to claim 5 , wherein when step S4 is performed, chemical mechanical polishing is used to planarize the top of the oxide resistive switching layer. 9 . 9 . The method for manufacturing an RRAM cell structure according to claim 5 , wherein when step S5 is performed, tantalum nitride (TaN) or titanium nitride (TiN) is used to form the top metal electrode. 10 .

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