A method for forming a memory

Abstract

The present invention discloses a method for forming a memory, which includes: providing a semiconductor substrate with a lower electrode formed therein; depositing an oxide on the semiconductor substrate to form an oxygen barrier layer located on the semiconductor substrate; depositing a metal material on the oxygen barrier layer to form a precursor located on the oxygen barrier layer; performing a removal process on the surface of the precursor to remove the native oxide layer on the surface of the precursor; performing an oxidation process on the precursor to convert the precursor into a functional material layer; performing an annealing process on the functional material layer; forming an upper electrode on the functional material layer; patterning the upper electrode, the functional material layer, and the oxygen barrier layer to form a memory. Since the oxidizing gas used during the oxidation process of the precursor is isolated above the oxygen barrier layer, this method can prevent the lower electrode from being oxidized, improve the process controllability, and is beneficial to enhancing the memory characteristics.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor integrated circuit manufacturing, and in particular, to a method for forming a memory. Background Art

[0002] At present, memory manufacturing technology is an important part of semiconductor integrated circuit manufacturing. With the continuous development of Moore's Law, the operating frequency of the central processing unit (CPU) has been continuously increasing, and the performance requirements for memories are also getting higher and higher. It has become difficult for mainstream traditional memories to meet the performance requirements. The "memory wall" problem has become increasingly prominent, and thus various new memory technologies have emerged.

[0003] Currently, the main new memories include resistive random access memory (RRAM), magnetic random access memory (MRAM), phase change random access memory (PCRAM), ferroelectric random access memory (FeRAM), etc. In frontier research, these new memories have been proven to have more excellent characteristics and good application prospects. Among these new memories, except for the fact that Intel / Micron has mass-produced PCRAM, other types of new memories have not been widely applied yet. For new memories to achieve large-scale production, in addition to having a better cost performance than existing mainstream memories, their stable and reliable production processes are crucial.

[0004] Taking RRAM as an example, although the structure of the memory itself is very simple, how to controllably fabricate it is the key to large-scale production applications of the memory. In the prior art, a functional material layer of RRAM can be fabricated by first depositing a precursor and then oxidizing the precursor to form an oxide. However, in the production process, since the waiting time between process steps cannot be precisely controlled, the precursor will undergo different changes during different waiting times, which will affect subsequent process steps and ultimately affect the consistency between device characteristics and the memory. On the other hand, during the process of oxidizing the precursor to form an oxide, part of the lower electrode is easily oxidized at the same time, and the process controllability is poor, which affects the device characteristics. Therefore, how to effectively control the processing process of the functional material layer in existing memories is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] An embodiment of the present invention provides a method for forming a memory, which can avoid the oxidation of the lower electrode, improve the process controllability, and is beneficial to improving the memory characteristics.

[0006] In a first aspect, the present invention provides a method for forming a memory, the method comprising: providing a semiconductor substrate, in which a lower electrode is formed, and the lower electrode is close to the upper surface of the semiconductor substrate; depositing an oxide on the semiconductor substrate to form an oxygen barrier layer on the semiconductor substrate; depositing a metal material on the oxygen barrier layer to form a precursor on the oxygen barrier layer; performing a removal process on the surface of the precursor to remove the native oxide layer on the surface of the precursor; performing an oxidation process on the precursor to convert the precursor into a functional material layer; performing an annealing process on the functional material layer; forming an upper electrode on the functional material layer; etching and patterning the upper electrode, the functional material layer and the oxygen barrier layer to form a memory.

[0007] The beneficial effects of the method for forming a memory provided by the present invention are as follows: on the one hand, since the oxidizing gas used during the oxidation process of the precursor is isolated above the oxygen barrier layer, the lower electrode can be prevented from being oxidized; on the other hand, the native oxide layer on the surface of the functional material layer is removed, avoiding the influence of the change of the precursor of the functional layer over time on the process, improving the process controllability, and being beneficial to improving the memory characteristics.

[0008] Optionally, the specific manner of depositing an oxide on the semiconductor substrate may include: depositing an oxide on the semiconductor substrate by physical vapor deposition, chemical vapor deposition or atomic layer deposition.

[0009] Optionally, the oxide is at least one of silicon oxide, aluminum oxide, zinc oxide or indium tin oxide.

[0010] Optionally, the metal material is at least one of copper, aluminum, hafnium, titanium, tantalum, titanium nitride or tantalum nitride.

[0011] Optionally, the specific manner of removing the native oxide layer on the surface of the precursor may include: performing a removal process on the surface of the precursor with a reducing gas, and the temperature of the removal process is 100°C to 400°C, so that the native oxide layer on the surface of the precursor is removed. After the removal process is completed in this way, the semiconductor substrate is not exposed to the atmosphere, so a native oxide layer will not be generated on the surface again.

[0012] Optionally, the specific manner of performing an oxidation process on the precursor to convert the precursor into a functional material layer may include: performing an oxidation process on the precursor with an oxidizing gas, and the temperature of the oxidation process is 200°C to 400°C, so that the precursor is converted into a functional material layer.

[0013] Optionally, the above method further includes: using an endpoint detection technique to monitor the oxidation process of the oxidation process in real time, and when all the precursors are converted into oxides, the oxidation process is ended. This method is beneficial to improving the process controllability through real-time monitoring.

[0014] Optionally, the specific method for annealing the functional material layer may include: annealing the functional material layer with an oxidizing gas or an inert gas, and the annealing temperature is 100°C to 400°C. Generally, annealing the functional material layer with an inert gas can not only slow down the reaction, but also adjust the oxygen distribution of the oxide in the functional material layer. However, annealing the functional material layer with an oxidizing gas can also adjust the oxygen distribution of the oxide in the functional material layer.

[0015] Optionally, forming the upper electrode on the functional material layer includes: forming the upper electrode on the functional material layer by physical vapor deposition, metal organic chemical vapor deposition or atomic layer deposition.

[0016] Optionally, removing the natural oxide layer on the surface of the precursor and oxidizing the precursor are both carried out in the same cavity, and the cavity is a vacuum environment. Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 Schematic flow chart of a method for forming a memory provided by the prior art;

[0019] Figure 2 Schematic diagrams of each stage of the manufacturing process of a memory provided by the embodiments of the present invention.

[0020] Description of Component Labels

[0021] 100 Semiconductor substrate

[0022] 200 Lower electrode

[0023] 300 Oxygen barrier layer

[0024] 400 Precursor

[0025] 500 Natural oxide layer

[0026] 600 Functional material layer

[0027] 700 Upper electrode Detailed Embodiments

[0028] To make the content of the present invention clearer and easier to understand, the following further explains the content of the present invention in conjunction with the accompanying drawings of the specification. Of course, the present invention is not limited to this specific embodiment, and general substitutions well-known to those skilled in the art are also covered within the protection scope of the present invention.

[0029] It should be noted that in the following specific embodiments, when detailing the embodiments of the present invention, in order to clearly show the structure of the present invention for easy explanation, the structures in the drawings are not drawn according to the general scale, and local magnification, deformation, and simplification are performed. Therefore, it should be avoided to understand this as a limitation of the present invention.

[0030] To make the objectives, technical solutions, and advantages of the present invention clearer, the following further combines Figure 1 shows a schematic flow diagram of a method for forming a memory, Figure 2 shows a schematic diagram of the phased results at each process preparation stage in this example.

[0031] Refer to Figure 1 , the preparation process of the memory provided by the embodiment of the present invention includes the following steps:

[0032] S101, provide a semiconductor substrate 100, in which a lower electrode 200 is formed.

[0033] As shown in (a) of Figure 2 , the semiconductor substrate 100 can be an N-type or P-type silicon substrate. The material of the semiconductor substrate 100 includes one or a combination of silicon, germanium, silicon germanide, silicon carbide, gallium arsenide, indium gallium, and the semiconductor substrate 100 can also be a silicon-on-insulator semiconductor substrate or a germanium-on-insulator semiconductor substrate.

[0034] Specifically, the silicon substrate may have completed the manufacturing of the required CMOS processing circuit, and then a lower electrode 200 is formed on the silicon substrate. This lower electrode is a metal electrode. In this embodiment, exemplarily, a 12-inch silicon wafer can be used as the silicon substrate, and the CMOS control circuit has been fabricated in the silicon substrate. The CMOS circuit is connected to the lower metal electrode through metal. The metal electrode can be various metal materials such as copper, aluminum, titanium nitride, tantalum nitride, etc. In this embodiment, it is tantalum nitride with a thickness of 50 nanometers.

[0035] S102, deposit an oxide on the semiconductor substrate 100 to form an oxygen barrier layer 300 on the semiconductor substrate 100.

[0036] Refer to Figure 2As shown in (b), an oxide is deposited on the front surface of an N-type or P-type silicon substrate by physical vapor deposition, chemical vapor deposition, atomic layer deposition, etc., so as to deposit and form an oxygen barrier layer 300. The oxide can be at least one of silicon oxide, aluminum oxide, zinc oxide, indium tin oxide (ITO), etc. The thickness of the oxygen barrier layer 300 is 2 to 20 nanometers. In this embodiment, exemplarily, 3 nm of silicon dioxide (SiO2) is deposited on the front surface of an N-type or P-type silicon substrate by chemical vapor deposition (CVD) as the oxygen barrier layer.

[0037] S103, deposit a metal material on the oxygen barrier layer 300 to form a precursor 400 located on the oxygen barrier layer 300.

[0038] See Figure 2 As shown in (c) of the figure, specifically, a metal material is deposited by chemical vapor deposition, atomic layer deposition, etc. The metal material can be metal materials such as copper, aluminum, hafnium, titanium, tantalum, titanium nitride, tantalum nitride, etc., to form a precursor located on the oxygen barrier layer 300. In this embodiment, exemplarily, 10 nanometers of titanium is deposited by sputtering to form the precursor 400.

[0039] S104, perform a removal treatment on the surface of the precursor so that the natural oxide layer on the surface of the precursor is removed.

[0040] It should be noted that due to the inability to achieve precise waiting time control between process steps in large-scale production preparation, for the precursor 400 with relatively active metal properties, its surface is exposed to the atmospheric environment, so a natural oxide layer is easily formed on the surface of the precursor, and the thickness of this natural oxide layer will change with time. The natural oxide layer will affect the functional characteristics of the precursor, so the natural oxide layer needs to be further removed.

[0041] Specifically, a reducing gas such as hydrogen or ammonia can be used to perform a removal treatment on the precursor to convert the thin natural oxide layer on the surface into the precursor, that is, to remove the natural oxide layer on the surface, as Figure 2 shown in (d) of the figure. In this embodiment, exemplarily, the precursor is titanium metal, and hydrogen plasma gas is used to perform a removal treatment on titanium in a vacuum environment at 300 °C to remove titanium oxide (TiOx) on the surface of titanium. After the removal treatment is completed, the precursor Ti is no longer exposed to the atmospheric environment, so a natural oxide layer will not be generated on the surface again.

[0042] S105, perform an oxidation treatment on the precursor so that the precursor is converted into a functional material layer 600.

[0043] Specifically, a possible implementation manner, such as Figure 2As shown in (e) thereof. Oxidizing gases such as oxygen, ozone, nitrous oxide, etc. can be used to oxidize the precursor to transform it into the functional material layer 600. At the same time, when oxidizing the precursor, endpoint detection technology is used to monitor the oxidation process in real time, and the process is stopped when the precursor is transformed into the functional material layer. In this embodiment, exemplarily, when the material of the precursor is titanium, nitrous oxide is used to oxidize the precursor at 400 °C, so that the titanium in the precursor is transformed into titanium oxynitride. At the same time, endpoint detection technology is used to monitor the oxidation process in real time. When the titanium is transformed into titanium oxynitride (TiOxNy), the refractive index of the thin film changes significantly, and at this time, the oxidation process is stopped. Since there is an oxygen barrier layer 300 under the precursor, such as SiO2 with a thickness of 3 nm, the oxidizing gas is isolated above the oxygen barrier layer, preventing the lower electrode from being oxidized.

[0044] Furthermore, in another possible implementation, the oxidation treatment of the precursor and the removal of the natural oxide layer on the surface of the precursor can both be completed in the same cavity. Since the cavity is in a vacuum environment, the semiconductor substrate will not be oxidized again.

[0045] S106, annealing the functional material layer 600.

[0046] Specifically, in one possible implementation, oxidizing gases or inert gases such as oxygen, ozone, nitrous oxide, argon, or nitrogen can be used for annealing to adjust the defects and charges in the functional material layer. Generally, annealing the functional material layer with inert gas can not only slow down the reaction but also adjust the oxygen distribution of the oxide in the functional material layer. However, annealing the functional material layer with oxidizing gas can also increase the oxygen concentration on the surface of the functional material layer.

[0047] In this embodiment, exemplarily, when the material of the precursor is titanium, post-treatment of the titanium oxide in the functional material layer is carried out by decoupled plasma oxidation at 400 °C to re-adjust the defects and charges in the titanium oxide and improve the device characteristics.

[0048] S107, forming an upper electrode 700 on the functional material layer.

[0049] Specifically, in one possible implementation, as Figure 2 shown in (f) thereof, physical vapor deposition, metal-organic chemical vapor deposition, atomic layer deposition, or other methods can be used to deposit the upper metal electrode to form the upper electrode 700. In this embodiment, exemplarily, 50 nm of titanium nitride is deposited by physical vapor deposition as the upper electrode metal.

[0050] S108, patterning the upper electrode 700, the functional material layer 600, and the oxygen barrier layer 300 to form a memory.

[0051] Specifically, in a possible implementation manner, the upper electrode 700 is patterned by photolithography and etching to form a memory as shown in (g) of Figure 2 .

[0052] It should be noted that the temperature for oxidizing the precursor is generally higher than the temperature used for the removal process and the annealing process. For example, the temperature used for the removal process is 300 °C, and the temperature used for the oxidation process is 400 °C. Because the higher the temperature, the more intense the reaction and the shorter the reaction time. However, the temperature generally does not exceed 400 °C, mainly because once the temperature exceeds 400 °C, the metal properties may be damaged.

[0053] In summary, in the method for forming the memory provided by the present invention, by first performing a removal process on the functional material layer to remove the natural oxide layer on the surface of the precursor, then monitoring in real time to convert the precursor into the functional material layer without oxidizing the lower electrode material, and finally performing a post-annealing treatment on the functional material layer, the influence of the precursor of the functional layer on the process over time is avoided, the difference in the composition of the functional material caused by the existence of the natural oxide layer is avoided, and the lower electrode is also prevented from being oxidized, improving the process controllability and being beneficial to improving the memory characteristics.

[0054] The above are only the preferred embodiments of the present invention, and the embodiments are not intended to limit the patent protection scope of the present invention. Therefore, any equivalent structural changes made by using the description and drawings of the present invention should similarly be included in the protection scope of the present invention.

[0055] Various modifications to these embodiments will be obvious to those of ordinary skill in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

Claims

1. A method for forming a memory, characterized in that, Including: Providing a semiconductor substrate, in which a lower electrode is formed, and the lower electrode is close to the upper surface of the semiconductor substrate; Depositing an oxide on the semiconductor substrate to form an oxygen barrier layer on the semiconductor substrate, wherein the oxide is at least one of silicon oxide, aluminum oxide, zinc oxide or indium tin oxide; Depositing a metal material on the oxygen barrier layer to form a precursor on the oxygen barrier layer; Performing a removal process on the surface of the precursor so that the natural oxide layer on the surface of the precursor is removed; Performing an oxidation process on the precursor so that the precursor is converted into a functional material layer; wherein, the oxidation process of the oxidation process is monitored in real time by an endpoint detection technique, and when the precursor is converted into a functional material layer, the refractive index changes significantly, and the process corresponding to the oxidation process is stopped; Performing an annealing process on the functional material layer; Forming an upper electrode on the functional material layer; Patterning the upper electrode, the functional material layer and the oxygen barrier layer to form a memory.

2. The forming method according to claim 1, wherein Depositing an oxide on the semiconductor substrate, including: Depositing an oxide on the semiconductor substrate by any one of physical vapor deposition, chemical vapor deposition or atomic layer deposition.

3. The forming method according to any one of claims 1 to 2, characterized in that The material of the precursor is at least one of copper, aluminum, hafnium, titanium, tantalum, titanium nitride or tantalum nitride.

4. The forming method according to claim 1, wherein Performing a removal process on the surface of the precursor so that the natural oxide layer on the surface of the precursor is removed, including: Performing a removal process on the surface of the precursor with a reducing gas, and the temperature of the removal process is 100°C to 400°C, so that the natural oxide layer on the surface of the precursor is removed.

5. The forming method according to any one of claims 1 to 2, characterized in that, Performing an oxidation process on the precursor so that the precursor is converted into a functional material layer, including: Performing an oxidation process on the precursor with an oxidizing gas, and the temperature of the oxidation process is 200°C to 400°C, so that the precursor is converted into a functional material layer.

6. The forming method according to any one of claims 1 to 2, characterized in that, Performing an annealing process on the functional material layer, including: Performing an annealing process on the functional material layer with an oxidizing gas or an inert gas, and the temperature of the annealing process is 100°C to 400°C.

7. The forming method according to any one of claims 1 to 2, characterized in that, Forming an upper electrode on the functional material layer, including: Forming an upper electrode on the functional material layer by physical vapor deposition, chemical vapor deposition or atomic layer deposition.

8. The forming method according to any one of claims 1 to 2, characterized in that, Removing the natural oxide layer on the surface of the precursor and performing the oxidation process on the precursor are both carried out in a cavity, and the cavity is a vacuum environment.

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