阅读说明：本技术 电阻式随机存取存储器及其制作方法 (Resistive random access memory and manufacturing method thereof ) 是由 孔德锦 欧阳锦坚 孔祥波 谈文毅 于 2021-04-16 设计创作，主要内容包括：本发明公开一种电阻式随机存取存储器及其制作方法,其中该电阻式随机存取存储器,包括一底电极、一可变电阻层位于该底电极上并且包括一U型剖面轮廓,以及一顶电极位于该可变电阻层上并且填满该可变电阻层的一凹槽。(The invention discloses a resistance random access memory and a manufacturing method thereof, wherein the resistance random access memory comprises a bottom electrode, a variable resistance layer which is positioned on the bottom electrode and comprises a U-shaped section outline, and a top electrode which is positioned on the variable resistance layer and fills a groove of the variable resistance layer.)

1. A resistive random access memory, comprising:

a bottom electrode;

a variable resistance layer on the bottom electrode and including a U-shaped cross-sectional profile; and

and the top electrode is positioned on the variable resistance layer and fills the groove of the variable resistance layer.

2. The rram as recited in claim 1, wherein the top surface of the top electrode is aligned with the top surface of the varistor layer.

3. The resistive random access memory of claim 1 wherein the top electrode is completely surrounded by the variable resistance layer in a top plan view.

4. The resistance random access memory according to claim 1, further comprising spacers disposed on the bottom electrode and on both sides of the variable resistance layer, wherein inner sidewalls of the spacers contacting the variable resistance layer comprise a curved cross-sectional profile.

5. The resistive random access memory of claim 4 further comprising:

a first dielectric layer located below the bottom electrode;

a second dielectric layer on the first dielectric layer and surrounding the bottom electrode and the spacer, wherein the outer sidewall of the spacer contacting the second dielectric layer comprises a linear cross-sectional profile.

6. The resistive random access memory as defined in claim 4 wherein the top corners of the bottom electrode are covered by the second dielectric layer.

7. The rram as claimed in claim 4, wherein the top surface of the second dielectric layer, the top surface of the top electrode, the top surface of the varistor layer and the top surface of the spacer are aligned.

8. The rram as claimed in claim 4, further comprising a third dielectric layer disposed on the second dielectric layer and directly contacting the top surface of the top electrode, the top surface of the variable resistance layer and the top surface of the spacer.

9. The resistive random access memory of claim 8 wherein the second dielectric layer and the third dielectric layer comprise the same material.

10. The resistive random access memory of claim 4 wherein the variable resistance layer comprises:

a horizontal portion located between the top electrode and the bottom electrode; and

and a vertical part located on the horizontal part and between the top electrode and the spacer, wherein the thickness of the horizontal part along the vertical direction is greater than that of the vertical part along the horizontal direction.

11. The RRAM of claim 4, wherein the spacer material comprises aluminum oxide (Al)₂O₃) Or silicon oxide (SiO)₂)。

12. The rram as recited in claim 1, wherein the material of the top and bottom electrodes comprises titanium nitride (TiN).

13. The resistive random access memory according to claim 1, wherein the material of the variable resistance layer comprises Transition Metal Oxide (TMO).

14. A method for manufacturing a resistive random access memory comprises the following steps:

forming a bottom electrode on the first dielectric layer;

forming a second dielectric layer on the first dielectric layer and covering the bottom electrode;

forming an opening in the second dielectric layer exposing a top surface of the bottom electrode;

forming a spacer covering the sidewall of the opening;

forming a variable resistance layer to cover the top surface of the bottom electrode and the spacer; and

forming a top electrode on the variable resistance layer and filling the opening.

15. The method of claim 14, wherein the width of the opening is smaller than the width of the bottom electrode.

16. The method according to claim 14, wherein the variable resistance layer comprises a U-shaped cross-sectional profile.

17. The method according to claim 14, wherein the spacer comprises an inner sidewall contacting the variable resistance layer and comprising a curved cross-sectional profile, and an outer sidewall contacting the second dielectric layer comprises a straight cross-sectional profile.

18. The method of claim 14, wherein the step of forming the variable resistance layer and the top electrode comprises:

forming a variable resistance material layer on the second dielectric layer and filling the opening;

forming a top electrode material layer on the variable resistance material layer and filling the opening; and

removing the variable resistance material layer and the top electrode material layer outside the opening.

19. The method of claim 14, further comprising forming a third dielectric layer on the second dielectric layer and directly contacting the top surface of the top electrode, the top surface of the variable resistance layer, and the top surface of the spacer.

20. The method of claim 19, wherein the second dielectric layer and the third dielectric layer comprise the same material.

Technical Field

The present invention relates to semiconductor devices and methods of fabricating the same, and more particularly, to a resistive random access memory and a method of fabricating the same.

Background

A Resistive Random Access Memory (RRAM) belongs to a non-volatile memory (NVM), and has characteristics of smaller size, fast read/write, long data storage time, low power consumption, good reliability, and compatibility with a semiconductor manufacturing process, and thus gradually receives attention in the field. The basic structure of the resistance random access memory is that a variable resistance layer is clamped between an upper electrode and a lower electrode, the variable resistance material is switched between a High Resistance State (HRS) and a Low Resistance State (LRS) through an applied voltage, and then different resistance states are compiled into 1 or 0 to achieve the purposes of storing and distinguishing data.

Currently, a conventional embedded resistive random access memory (embedded) is fabricated by integrating a back-end-of-line (BEOL) process into an interlayer dielectric layer of an interconnect structure of a semiconductor device. However, as the density of the memory cell array gradually increases, the distance between the memory cells gradually decreases, which has made the gap fill (gap fill) capability of the conventional dielectric layer deposition process challenging. If the dielectric layer is not well filled, gaps (void) are formed between the memory cells, which affects the yield of the product.

Disclosure of Invention

The invention provides a resistive random access memory and a manufacturing method thereof, which mainly forms an opening for forming a memory cell in advance in a dielectric layer and then manufactures individual memory cells in the opening, thereby omitting the step of filling gaps among the memory cells with the dielectric layer and avoiding the defects caused by insufficient gap filling capability of the dielectric layer.

To achieve the above objective, an embodiment of the present invention provides a resistance random access memory, which includes a bottom electrode, a variable resistance layer on the bottom electrode and having a U-shaped cross-sectional profile, and a top electrode on the variable resistance layer and filling a recess of the variable resistance layer.

Another embodiment of the present invention provides a method for fabricating a resistive random access memory, which includes forming a bottom electrode on a first dielectric layer, forming a second dielectric layer on the first dielectric layer and covering the bottom electrode, forming an opening in the second dielectric layer to expose a top surface of the bottom electrode, forming a spacer to cover a sidewall of the opening, forming a variable resistance layer to cover the top surface of the bottom electrode and the spacer, and forming a top electrode on the variable resistance layer and filling the opening.

Drawings

Fig. 1 to 7 are schematic diagrams illustrating steps of a method for manufacturing a rram according to an embodiment of the invention;

fig. 8, 9 and 10 are top plan views of the resistance random access memory of some embodiments of the invention at the step shown in fig. 6.

Description of the main elements

10 base

12 conductive structure

14 dielectric layer

16 first dielectric layer

16a etch stop layer

16b cushion layer

18 conductive plug

20 bottom electrode

20a top surface

20b top corner

22 second dielectric layer

24 opening

24a side wall

26 spacer

26a inner side wall

26b outer side wall

28 variable resistance material layer

28a variable resistance layer

28b horizontal part

28c vertical part

28R groove

30 top electrode material layer

30a top electrode

32 third dielectric layer

34 conductive plug

T1 thickness

T2 thickness

100 memory cell

Distance S1

Detailed Description

In order to make the present invention more comprehensible to those skilled in the art, several preferred embodiments accompanied with figures are described in detail below to explain the present invention and its intended effects. Structural, logical, and electrical changes may be made in other embodiments without departing from the scope of the present invention. The drawings of the present invention are merely schematic representations, the detailed scale of which may be adjusted according to design requirements. The description of the drawings is for the purpose of illustrating the relative positions of elements in the drawings, and it will be understood by those skilled in the art that the relative positions of the elements may be reversed to represent the same elements, and thus the scope of the disclosure should be accorded the full scope of the disclosure.

Fig. 1 to 7 are schematic diagrams illustrating steps of a method for manufacturing a resistance random access memory according to an embodiment of the invention. Referring to fig. 1, a substrate 10 is provided, a first dielectric layer 16 is formed on the substrate 10, and a bottom electrode 20 is formed on the first dielectric layer 16.

According to an embodiment of the present invention, the rram is formed in a dielectric layer of an interconnect structure, and thus the substrate 10 may be a semiconductor substrate completed to a certain stage of a fabrication process, such as a semiconductor substrate that has been completed in a front-end-of-line fabrication process (FEOL) and a portion of a back-end-of-line fabrication process (BEOL). For simplicity, fig. 1 only illustrates a dielectric layer 14 of the substrate 10 and the conductive structure 12 formed in the dielectric layer 14. The first dielectric layer 16 may include an etch stop layer 16a and a liner layer 16b overlying the etch stop layer 16 a. A conductive plug 18 may be disposed within the first dielectric layer 16 through the liner layer 16b and the etch stop layer 16a to electrically connect the bottom electrode 20 and the conductive structure 12.

The dielectric layer 14 and the liner layer 16b may each comprise a dielectric material, such as silicon oxide (SiO)₂) Non-doped silicon glass (USG), or low-k dielectric materials such as Fluorinated Silicon Glass (FSG), silicon carbon oxide (SiCOH), spin-on glass (spin-on glass), porous low-k dielectric materials, or organic polymer dielectric materials, but not limited thereto. In accordance with an embodiment of the present invention, the dielectric layer 14 comprises a low dielectric constant (low-k) dielectric material and the liner layer 16b comprises silicon oxide. Etch stop layer 16a may comprise a nitrogen-containing dielectric material, such as, but not limited to, silicon nitride (SiN), silicon oxynitride (SiON), silicon carbide nitride (SiCN), or silicon carbide Nitride (NDC)This is done. In accordance with an embodiment of the present invention, the etch stop layer 16a comprises nitrogen doped silicon carbide (NDC). Bottom electrode 20, conductive structure 12, and conductive plug 18 may each include a conductive material, such as, but not limited to, cobalt (Co), copper (Cu), aluminum (Al), tungsten (W), nickel (Ni), platinum (Pt), tantalum (Ta), titanium (Ti), a compound, a composite layer, or an alloy thereof. In some embodiments, bottom electrode 20 may comprise titanium nitride (TiN), conductive structure 12 may comprise copper (Cu), and conductive plug 18 may comprise tungsten (W). In accordance with an embodiment of the present invention, a barrier layer (not shown), such as a single layer or a composite layer of ti, tin, ta, and/or tan, may be included between the conductive plug 18 and the first dielectric layer 16 and the conductive structure 12.

Please refer to fig. 2. Next, a second dielectric layer 22 is formed on the first dielectric layer 16 and covers the bottom electrode 20. The material of the second dielectric layer 22 may be selected from the dielectric materials selected above with respect to the dielectric layer 14 and the liner layer 16b, and will not be repeated here for simplicity of description. According to an embodiment of the present invention, the second dielectric layer 22 may comprise a low-k dielectric material.

Please refer to fig. 3. Next, a patterning process (e.g., a photolithography and etching process) may be performed on the second dielectric layer 22 to form an opening 24 in the second dielectric layer 22 directly above the bottom electrode 20, exposing a portion of the top surface 20a of the bottom electrode 20. The width of the opening 24 may be substantially equal to or less than the width of the bottom electrode 20. Fig. 3 shows that when the width of the opening 24 is smaller than the width of the bottom electrode 20, the sidewall 24a of the opening is located on the top surface 20a of the bottom electrode 20 and is not aligned with the sidewall of the bottom electrode 20, and the top corner 20b of the bottom electrode 20 is covered by the second dielectric layer 22 and is not exposed.

Please refer to fig. 4. Next, spacers 26 are formed on the side walls 24a of the opening 24. According to an embodiment of the present invention, the spacers 26 may be formed by a self-aligned spacer (self-aligned spacer) process, such as Atomic Layer Deposition (ALD) to form a spacer material layer (not shown) conformally covering the top surface of the second dielectric layer 22, the sidewalls 24a of the openings 24 and the top surface 20a of the bottom electrode 20, and then performing an anisotropic etching process on the second dielectric layer 22 until the second dielectric layer is exposed22 and the top surface 20a of the bottom electrode 20 and leaves a portion of the spacer material layer on the sidewalls 24a of the opening 24 to form the spacers 26. It is to be understood that the spacer 26 completely surrounds the opening 24 along the side wall 24 a. According to an embodiment of the present invention, the material of the spacer 26 may include aluminum oxide (Al)₂O₃) Or silicon oxide (SiO)₂) But is not limited thereto. It is noted that the sidewall 26a of the spacer 26 facing the opening 24 has a curved cross-sectional profile due to the anisotropic etching process, and the sidewall 26b of the spacer 26 contacting the second dielectric layer 22 has a linear cross-sectional profile following the sidewall 24a of the opening 24.

Please refer to fig. 5. After forming the spacer 26, a variable resistance material layer 28 is formed on the second dielectric layer 22, such that the variable resistance material layer 28 partially fills the opening 24 and covers along the outer sidewall 26a of the spacer 26 and the top surface 20a of the bottom electrode 20, and then a top electrode material layer 30 is formed on the variable resistance material layer 28 such that the top electrode material layer 30 completely fills the opening 24. The variable resistance material layer 28 may include Transition Metal Oxide (TMO) such as nickel oxide (NiO), titanium oxide (TiO), zinc oxide (ZnO), zirconium oxide (ZrO), hafnium oxide (HfO), tantalum oxide (TaO), but is not limited thereto. According to an embodiment of the present invention, the material of the top electrode material layer 30 may be selected from the conductive materials selected above with respect to the bottom electrode 20, such as titanium nitride (TiN).

Please refer to fig. 6. Next, a planarization process, such as a Chemical Mechanical Polishing (CMP) process, may be performed to remove the top electrode material layer 30 and the variable resistance material layer 28 outside the opening 24 until the top surface of the second dielectric layer 22 is exposed. The top electrode material layer 30 and the variable resistance material layer 28 remaining in the opening become a top electrode 30a and a variable resistance layer 28a, respectively. In some embodiments, after a Chemical Mechanical Polishing (CMP) process, the top surfaces of the spacers 26 are exposed between the top electrode 30a and the second dielectric layer 22 and are horizontally aligned with the top surface of the top electrode 30a, the top surface of the variable resistance layer 28a, and the top surface of the second dielectric layer 22.

As shown in fig. 6, a memory cell 100 of a resistance random access memory according to an embodiment of the present invention includes a bottom electrode 20, a variable resistance layer 28a on the bottom electrode 20 and having a U-shaped cross-sectional profile, a top electrode 30a on the variable resistance layer 28a and filling up a recess 28R in the variable resistance layer 28a, and spacers 26 on the bottom electrode 20 and on two sides of the variable resistance layer 28 a. In detail, the variable resistance layer 28a may include a horizontal portion 28b and a vertical portion 28c on the horizontal portion 28b, wherein the horizontal portion 28b is substantially located between the top electrode 30b and the bottom electrode 20 in the vertical direction, and the vertical portion 28c is substantially located between the top electrode 30a and the spacer 26 in the horizontal direction. It should be noted that, by adjusting the manufacturing process parameters for manufacturing the variable-resistance material layer 28 (refer to fig. 5), the thickness T1 of the horizontal portion 28b of the variable-resistance layer 28a along the vertical direction is greater than the thickness T2 of the vertical portion 28c along the horizontal direction, so that the recess 28R can have a sufficient width when the horizontal portion 28b reaches the required thickness specification, and the top electrode 30a in the recess 28R can have a sufficient width to facilitate the landing and electrical connection of the subsequent conductive plug 34 (refer to fig. 7). According to an embodiment of the invention, the thickness T2 may be approximately between 1/4 and 1/10 of the thickness T1.

Please refer to fig. 7. Next, a third dielectric layer 32 is formed on the second dielectric layer 22, and then a conductive plug 34 is formed in the third dielectric layer 32 directly above the top electrode 30a and electrically connects the conductive plug 34 and the top electrode 30 a. The material of the third dielectric layer 32 may be selected from the dielectric materials selected above with respect to the dielectric layer 14 and the liner layer 16b, and will not be repeated herein for simplicity of description. According to an embodiment of the present invention, the second dielectric layer 22 and the third dielectric layer 32 may comprise the same low dielectric constant (low-k) dielectric material. It is noted that the third dielectric layer 32 is in direct contact with the top surface of the top electrode 30a, the top surface of the vertical portion 28c of the variable-resistance layer 28a, and the top surface of the spacer 26. The material of conductive plug 34 may be selected from the materials previously selected for conductive structure 12, and may include, for example, copper (Cu). According to an embodiment of the present invention, a barrier layer (not shown) may be included between the conductive plug 34 and the third dielectric layer 32 and the top electrode 30a, such as a single layer or a composite layer of ti, tin, ta, and/or tan.

Referring to fig. 8, 9 and 10, top plan views of the rram at the steps shown in fig. 6 are shown according to some embodiments of the present invention. The resistive random access memory includes a plurality of memory cells 100 arranged in an array and separated from each other by a distance S1 when viewed from a top view. The shape of the top electrode 30a of the memory cell 100 is generally determined by the shape of the opening 24, and may have, for example, a generally circular (FIG. 8), square (FIG. 9), or rectangular (FIG. 10) shape, but is not limited thereto, and the top electrode 30a has a smaller area than the opening 24 due to the relationship between the spacers 26 formed in the opening 24. It is to be noted that, in any shape of the top electrode 30a, it is completely surrounded by the variable resistance layer 28 (the vertical portion 28c), and then the variable resistance layer 28 is completely surrounded by the spacer 26. The present invention first deposits the second dielectric layer 22 (refer to fig. 2) globally, then forms the opening 24 in the second dielectric layer 22, and then manufactures the memory cell 100 of the rram in the opening 24 in a manner similar to the damascene (damascone) manufacturing process, that is, the present invention does not need to fill the gap between the memory cells 100 through the dielectric layer gap filling step, so the gap (void) problem caused by the insufficient gap filling (gap fill) capability of the dielectric layer does not exist. Therefore, the present invention is not limited by the gap fill capability of the dielectric layer, and the distance S1 between the memory cells 100 is further reduced to obtain higher array density.

The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in the claims of the present invention should be covered by the present invention.