A method for reducing damage to MRAM magnetic tunnel junctions
By forming a modified layer on the sidewall of the MTJ layer of the MRAM, the problem of crystal structure destruction in the MRAM process is solved, the MTJ layer is protected, and the performance of the MRAM device is improved.
Patent Information
- Application Number
- CN202110962630.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-08-20
- Publication Date
- 2025-10-10
- Estimated Expiration
- 2041-08-20
Smart Images
Figure CN115715141B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of semiconductor chip production, and more particularly to a method for reducing damage to an MRAM magnetic tunnel junction. Background Art
[0002] With the continuous development of science and technology, various types of memory have been widely used in people's lives and work, bringing great convenience to people's lives.
[0003] Magnetic Random Access Memory (MRAM) is a relatively new type of RAM in the RAM market. Compared to traditional dynamic random access memory (DRAM), static random access memory (SRAM), and flash memory, MRAM boasts higher read and write speeds than flash memory, as well as radiation resistance and non-volatility that SRAM and DRAM lack. Therefore, many storage needs that currently require a combination of these three types of memory can often be met with MRAM alone.
[0004] However, during the current manufacturing process of the MRAM magnetic tunnel junction, the process will destroy the crystal structure of the sidewall area of the magnetic tunnel junction, thereby causing the MRAM device to fail. Summary of the Invention
[0005] In view of this, in order to solve the above problems, the present invention provides a method for reducing MRAM magnetic tunnel junction damage, and the technical solution is as follows:
[0006] A method for reducing damage to an MRAM magnetic tunnel junction, the method comprising:
[0007] Providing a basic structure, the basic structure comprising a substrate, a lower electrode, an MTJ layer, and an upper electrode arranged in sequence in a first direction, wherein the first direction is perpendicular to the substrate and points from the substrate to the lower electrode;
[0008] Performing a first etching process on a surface of the upper electrode facing away from the substrate until the lower electrode is exposed;
[0009] Pre-treating the sidewall of the MTJ layer to react the sidewall of the MTJ layer to form a modified layer with a preset thickness;
[0010] A second etching process is performed until the substrate is exposed.
[0011] Preferably, in the above method, the first etching process comprises:
[0012] The first etching process is performed on the surface of the upper electrode away from the substrate by using a plasma beam etching method until the lower electrode is exposed.
[0013] In the plasma beam etching method, the ion beam angle is 10°-60°.
[0014] The ion energy is 50V-600V.
[0015] The ion acceleration bias is 50V-1000V.
[0016] The gas flow rate is 10sccm-500sccm.
[0017] In the plasma beam etching method, the gas is an inert gas, nitrogen, oxygen, a fluorine-based gas, an amino gas, carbon monoxide, carbon dioxide, an alcohol gas, or a different combination of the above gases.
[0018] Preferably, in the above method, the first etching process comprises:
[0019] The first etching process is performed on the surface of the upper electrode away from the substrate by using a reactive ion etching method until the lower electrode is exposed.
[0020] In the reactive ion etching method, the source electrode power is 500W-2000W.
[0021] The bias electrode power is 100W-2000W.
[0022] The etching chamber pressure is 2mT-20mT.
[0023] The gas flow rate is 10sccm-500sccm.
[0024] In the reactive ion etching method, the gas is an inert gas, nitrogen, oxygen, a fluorine-based gas, an amino gas, carbon monoxide, carbon dioxide, an alcohol gas, or a different combination of the above gases.
[0025] Preferably, in the above method, the pretreatment of the sidewall of the MTJ layer to make the sidewall of the MTJ layer react to form a modified layer with a predetermined thickness comprises:
[0026] After the sidewall of the MTJ layer is completely exposed, the sidewall of the MTJ layer is pretreated by using a plasma beam etching method to react with the sidewall of the MTJ layer to form a modified layer with a predetermined thickness.
[0027] Preferably, in the above method, in the plasma beam etching method, the ion beam angle is 30°-60°;
[0028] Ion energy is 30V-100V;
[0029] Ion acceleration bias is 50V-1000V;
[0030] The gas flow rate is 10 sccm-500 sccm.
[0031] Preferably, in the above method, in the plasma beam etching mode, the gas is nitrogen, oxygen, hydrogen or different combinations of the above gases.
[0032] Preferably, in the above method, the etching time for pre-treating the sidewall of the MTJ layer by plasma beam etching is less than or equal to 120 seconds.
[0033] Preferably, in the above method, the thickness of the modified layer is 1 nm-2 nm.
[0034] Preferably, in the above method, the second etching process includes:
[0035] Performing a second etching process using a plasma beam etching method until the substrate is exposed;
[0036] In the plasma beam etching method, the ion beam angle is 10°-60°;
[0037] Ion energy is 50V-600V;
[0038] Ion acceleration bias is 50V-1000V;
[0039] Gas flow rate is 10 sccm-500 sccm;
[0040] In the plasma beam etching method, the gas is an inert gas, nitrogen, oxygen, fluorine-based gas, amino gas, carbon monoxide, carbon dioxide, alcohol gas or different combinations of the above gases.
[0041] Preferably, in the above method, the second etching process includes:
[0042] Performing a second etching process by reactive ion etching until the substrate is exposed;
[0043] In the reactive ion etching method, the source electrode power is 500W-2000W;
[0044] Bias electrode power is 100W-2000W;
[0045] The etching chamber pressure is 2mT-20mT;
[0046] Gas flow rate is 10 sccm-500 sccm;
[0047] In the reactive ion etching method, the gas is an inert gas, nitrogen, oxygen, fluorine-based gas, amino gas, carbon monoxide, carbon dioxide, alcohol gas or different combinations of the above gases.
[0048] Compared with the prior art, the present invention has the following beneficial effects:
[0049] The present invention provides a method for reducing damage to an MRAM magnetic tunnel junction, comprising: providing a basic structure, the basic structure comprising a substrate, a lower electrode, an MTJ layer, and an upper electrode arranged in sequence in a first direction, wherein the first direction is perpendicular to the substrate and points from the substrate to the lower electrode; performing a first etching process on a surface of the upper electrode facing away from the substrate until the lower electrode is exposed; pre-treating the sidewalls of the MTJ layer so that the sidewalls of the MTJ layer react to form a modified layer of a preset thickness; and performing a second etching process until the substrate is exposed.
[0050] The method pre-treats the sidewalls of the MTJ layer to react and form a modified layer of a preset thickness. The modified layer can scatter incident ions in a subsequent etching process to minimize MTJ damage. BRIEF DESCRIPTION OF THE DRAWINGS
[0051] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.
[0052] Figure 1 A simplified schematic diagram of the structure of a single byte of an MRAM;
[0053] Figure 2 Schematic diagram of the working principle of MTJ;
[0054] Figure 3 A simplified schematic diagram of a single byte of another type of MRAM;
[0055] Figure 4 This is a schematic diagram of damage caused during the MRAM process. Generally, this part of the damaged structure is called MTJ damage;
[0056] Figure 5A flowchart of a method for reducing damage of a magnetic tunnel junction of an MRAM is provided in an embodiment of the present application.
[0057] Figure 6-Figure 9 A flowchart of a method for reducing damage of a magnetic tunnel junction of an MRAM is provided in an embodiment of the present application. Figure 5 A flowchart of a method for reducing damage of a magnetic tunnel junction of an MRAM is provided in an embodiment of the present application.
[0058] Figure 10 A flowchart of a method for reducing damage of a magnetic tunnel junction of an MRAM is provided in an embodiment of the present application. DETAILED DESCRIPTION
[0059] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort fall within the protection scope of the present application.
[0060] Based on the content described in the background, reference is made to Figure 1 , Figure 1 A flowchart of a method for reducing damage of a magnetic tunnel junction of an MRAM is provided in an embodiment of the present application. Figure 1 As shown in the figure, the whole MRAM structure is located on a substrate, and a lower electrode, a magnetic tunnel junction (MTJ) and an upper electrode are sequentially arranged in a direction; wherein, the MTJ is a key structure of the MRAM device, as shown in the figure, in the direction, the MTJ includes a fixed magnetic layer, an insulating layer and a free magnetic layer. Figure 1
[0061] It should be noted that the direction is perpendicular to the substrate and points from the substrate to the lower electrode.
[0062] Based on the MRAM structure shown in the figure, reference is made to Figure 1 , Figure 2 , Figure 2 A flowchart of a method for reducing damage of a magnetic tunnel junction of an MRAM is provided in an embodiment of the present application. Figure 2 As shown in the figure, when a current is applied to the MTJ layer, the current can pass through in a tunneling manner due to the very thin thickness (usually several nanometers) of the insulating layer; wherein, the magnetic pole direction of the fixed magnetic layer is fixed, and the magnetic pole direction of the free magnetic layer can be changed.
[0063] When the magnetic pole directions of the fixed magnetic layer and the free magnetic layer are parallel, the MTJ presents a smaller resistance (Rp) and a larger tunneling current (Ip), at this time, the whole structure can be regarded as a conduction state, representing a binary byte of "1".
[0064] When the magnetic poles of the fixed magnetic layer and the free magnetic layer are in opposite directions (anti-parallel), the MTJ exhibits a larger resistance (Rap) and a smaller tunneling current (Iap). At this time, the entire structure can be regarded as a non-conducting state, representing a binary byte "0".
[0065] From this we can see that the performance of MTJ is measured by tunneling magnetoresistance (TMR). The formula of TMR can be written as:
[0066]
[0067] The larger the TMR, the better the MRAM performance.
[0068] As can be seen from the above formula, the inventors have discovered that the greater the difference between the on-state resistance (Rp) and the non-conducting state resistance (Rap), the better the device performance.
[0069] From the working principle of MTJ, we can know that the key to the operation of MTJ is the good insulation of the insulating layer, so that electrons can only tunnel through this path, rather than directly passing through the insulating layer (leakage) to directly connect the fixed magnetic layer and the free magnetic layer.
[0070] The performance index of the insulating layer is generally represented by RA. Specifically, RA is the product of the insulation layer resistance (R) and area (A). The larger RA is, the better the device performance is.
[0071] refer to Figure 3 , Figure 3 A simplified structural diagram of a single byte of another MRAM is shown. Figure 1 The multiple MRAM single-byte structures shown are arranged into an array and connected by wires to form a Figure 3 The simple MRAM storage structure shown.
[0072] like Figure 3 As shown, a trench morphology is formed between multiple MRAM single-byte structures, which can also be understood as the magnetic tunnel node structure of MRAM.
[0073] Typically, the manufacturing process of MRAM generally requires the use of plasma beam etching process. During this etching process, ions with a certain energy will destroy the crystal structure of the MTJ layer sidewall. Figure 4 , Figure 4 This is a schematic diagram of damage caused during the MRAM process. Usually, this part of the damaged structure is called MTJ damage.
[0074] The MTJ damage reduces the area (A) of the insulating layer, thereby reducing RA, resulting in poor device performance.
[0075] Based on this, one solution in the prior art is to use low-energy ions as much as possible during the etching process to reduce damage; however, the main problem with this solution is that reducing the ion energy will also reduce the etching rate accordingly, which will reduce production capacity.
[0076] Another solution in the prior art is to use some chemical means to remove the damage after the MTJ damage is formed; however, this solution only treats the symptoms and not the root cause, because they do not reduce the damage. They only remove the damaged structure after the damage occurs, which still leads to a reduction in the area of the insulating layer.
[0077] Based on this, the present invention provides a method for reducing MRAM magnetic tunnel junction damage, which can greatly reduce MTJ damage and thereby improve MRAM device performance.
[0078] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.
[0079] refer to Figure 5 , Figure 5 A flow chart of a method for reducing damage to an MRAM magnetic tunnel junction provided by an embodiment of the present invention.
[0080] The method comprises:
[0081] S101: If Figure 6 As shown, a basic structure is provided, which includes a substrate, a lower electrode, an MTJ layer and an upper electrode arranged in sequence in a first direction, where the first direction is perpendicular to the substrate and points from the substrate to the lower electrode.
[0082] In this step, before performing the first etching process, a mask layer is provided on the surface of the upper electrode facing away from the substrate, and the mask layer includes a plurality of mask units.
[0083] That is to say, a mask layer is provided above the basic structure, that is, on the surface of the upper electrode facing away from the MTJ layer. Depending on different situations, the material of the mask can be TiN, Ta, C, Si, SiO, SiN or different combinations of the above materials, which is not limited in the embodiments of the present invention.
[0084] S102: Figure 7 As shown, a first etching process is performed on the surface of the upper electrode facing away from the substrate until the lower electrode is exposed.
[0085] In this step, the etching amount of the first etching treatment needs to be determined according to actual conditions, but it is necessary to ensure that the etching stops at the interface between the MTJ layer and the lower electrode.
[0086] Optionally, the first etching treatment comprises:
[0087] The first etching treatment is performed from the surface of the upper electrode away from the substrate side by using a plasma beam etching method until the lower electrode is exposed.
[0088] That is, the etching method of the first etching treatment is an ion beam etching method (IBE), specifically:
[0089] In the ion beam etching method, the ion beam angle is 10°-60°;
[0090] The ion energy is 50V-600V;
[0091] The ion acceleration bias is 50V-1000V;
[0092] The gas flow is 10sccm-500sccm;
[0093] In the ion beam etching method, the gas is an inert gas, nitrogen, oxygen, a fluorine-based gas, an amino gas, carbon monoxide, carbon dioxide, an alcohol gas, or a different combination of the above gases.
[0094] Or,
[0095] Optionally, the first etching treatment comprises:
[0096] The first etching treatment is performed from the surface of the upper electrode away from the substrate side by using a reactive ion etching method until the lower electrode is exposed.
[0097] That is, the etching method of the first etching treatment is a reactive ion etching method (RIE), specifically:
[0098] In the reactive ion etching method, the source electrode power is 500W-2000W;
[0099] The bias electrode power is 100W-2000W;
[0100] The etching chamber pressure is 2mT-20mT;
[0101] The gas flow is 10sccm-500sccm;
[0102] In the reactive ion etching method, the gas is an inert gas, nitrogen, oxygen, fluorine-based gas, amino gas, carbon monoxide, carbon dioxide, alcohol gas or different combinations of the above gases.
[0103] S103: If Figure 8 As shown, the sidewall of the MTJ layer is pre-treated to react with the sidewall of the MTJ layer to form a modified layer with a preset thickness.
[0104] S104: Figure 9 As shown, a second etching process is performed until the substrate is exposed.
[0105] In this step, the etching amount of the second etching process needs to be determined according to the actual situation, but it needs to be ensured that the etching stops at the interface between the lower electrode and the substrate.
[0106] Optionally, the second etching process includes:
[0107] A second etching process is performed by using a plasma beam etching method until the substrate is exposed.
[0108] That is to say, the etching method of the second etching process is plasma beam etching (IBE), specifically:
[0109] In the plasma beam etching method, the ion beam angle is 10°-60°;
[0110] Ion energy is 50V-600V;
[0111] Ion acceleration bias is 50V-1000V;
[0112] Gas flow rate is 10 sccm-500 sccm;
[0113] In the plasma beam etching method, the gas is an inert gas, nitrogen, oxygen, fluorine-based gas, amino gas, carbon monoxide, carbon dioxide, alcohol gas or different combinations of the above gases.
[0114] or,
[0115] Optionally, the second etching process includes:
[0116] A second etching process is performed by using reactive ion etching until the substrate is exposed.
[0117] That is to say, the etching method of the second etching process is reactive ion etching (RIE), specifically:
[0118] In the reactive ion etching method, the source electrode power is 500W-2000W;
[0119] Bias electrode power is 100W-2000W;
[0120] The etching chamber pressure is 2mT-20mT;
[0121] Gas flow rate is 10 sccm-500 sccm;
[0122] In the reactive ion etching method, the gas is an inert gas, nitrogen, oxygen, fluorine-based gas, amino gas, carbon monoxide, carbon dioxide, alcohol gas or different combinations of the above gases.
[0123] In this embodiment, the sidewalls of the MTJ layer are pre-treated to react with each other to form a modified layer of a preset thickness. The modified layer can scatter incident ions in subsequent etching processes to minimize MTJ damage.
[0124] Optionally, in another embodiment of the present invention, pre-treating the sidewall of the MTJ layer to react the sidewall of the MTJ layer to form a modified layer of a preset thickness includes:
[0125] After the sidewalls of the MTJ layer are completely exposed, the sidewalls of the MTJ layer are pre-treated by plasma beam etching to react with the sidewalls of the MTJ layer to form a modified layer with a preset thickness.
[0126] Optionally, in the plasma beam etching method, the ion beam angle is 30°-60°;
[0127] Ion energy is 30V-100V;
[0128] Ion acceleration bias is 50V-1000V;
[0129] The gas flow rate is 10 sccm-500 sccm.
[0130] Optionally, in the plasma beam etching method, the gas is nitrogen, oxygen, hydrogen or different combinations of the above gases.
[0131] In this embodiment, reference Figure 10 , Figure 10 A schematic diagram of the effect of an MTJ layer with or without pretreatment provided by an embodiment of the present invention; Figure 10As shown in FIG, the lattice structure of the sidewall of the MTJ layer that has not been pre-treated is neatly arranged, and the incident ions can relatively easily penetrate along the lattice in the subsequent etching process. This is called the passage effect. In this case, the incident ions in the subsequent etching process can cause deep MTJ damage to the MTJ layer.
[0132] The lattice structure of the sidewall of the pre-treated MTJ layer is changed by nitrogen, oxygen, hydrogen or different combinations of the above gases to form a modified layer of preset thickness. In the subsequent etching process, the incident ions are scattered by the modified layer, resulting in a weakened channel effect, thereby minimizing MTJ damage and improving device performance.
[0133] Optionally, in another embodiment of the present invention, the etching time of pre-treating the sidewall of the MTJ layer by plasma beam etching is less than or equal to 120 seconds.
[0134] In this embodiment, the etching time of the plasma beam etching method for pre-treating the sidewall of the MTJ layer is controlled to control the thickness of the modified layer and achieve the selection of the optimal thickness.
[0135] If the etching time is greater than 120 seconds, the thickness of the modified layer is relatively thick, which is actually MTJ damage. Therefore, the etching time should be reasonably controlled to control the thickness of the modified layer to prevent the expansion of MTJ damage in subsequent processes to the greatest extent.
[0136] Optionally, the thickness of the modified layer is 1 nm-2 nm.
[0137] It should be noted that the substrate in the embodiment of the present invention can be a dielectric layer of various materials, and is therefore illustrated as "substrate / dielectric" in the accompanying drawings. The specific material is not limited in the embodiment of the present invention.
[0138] The above describes in detail a method for reducing MRAM magnetic tunnel junction damage provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will appreciate that the specific implementation methods and application scopes may vary based on the concepts of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.
[0139] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.
[0140] It should also be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that the process, method, article, or apparatus comprising a series of elements inherent to the elements, or also including elements inherent to these processes, methods, articles, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus comprising the element.
[0141] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A method for reducing damage to an MRAM magnetic tunnel junction, characterized in that: The method comprises: Providing a basic structure, the basic structure comprising a substrate, a lower electrode, an MTJ layer, and an upper electrode arranged in sequence in a first direction, wherein the first direction is perpendicular to the substrate and points from the substrate to the lower electrode; Performing a first etching process on a surface of the upper electrode facing away from the substrate until the lower electrode is exposed; Pre-treating the sidewalls of the MTJ layer so that the sidewalls of the MTJ layer react to form a modified layer of a preset thickness; wherein the pre-treating the sidewalls of the MTJ layer so that the sidewalls of the MTJ layer react to form a modified layer of a preset thickness comprises: after all the sidewalls of the MTJ layer are exposed, pre-treating the sidewalls of the MTJ layer by plasma beam etching to react with the sidewalls of the MTJ layer to form a modified layer of a preset thickness; the modified layer is used to scatter incident ions in a subsequent etching process; A second etching process is performed until the substrate is exposed.
2. The method according to claim 1, characterized in that The first etching process includes: Performing a first etching process on a surface of the upper electrode facing away from the substrate by plasma beam etching until the lower electrode is exposed; In the plasma beam etching method, the ion beam angle is 10°-60°; Ion energy is 50V-600V; Ion acceleration bias is 50V-1000V; Gas flow rate is 10 sccm-500 sccm; In the plasma beam etching method, the gas is an inert gas, nitrogen, oxygen, fluorine-based gas, amino gas, carbon monoxide, carbon dioxide, alcohol gas or different combinations of the above gases.
3. The method according to claim 1, characterized in that The first etching process includes: Performing a first etching process on the surface of the upper electrode facing away from the substrate by reactive ion etching until the lower electrode is exposed; In the reactive ion etching method, the source electrode power is 500W-2000W; Bias electrode power is 100W-2000W; The etching chamber pressure is 2mT-20mT; Gas flow rate is 10 sccm-500 sccm; In the reactive ion etching method, the gas is an inert gas, nitrogen, oxygen, fluorine-based gas, amino gas, carbon monoxide, carbon dioxide, alcohol gas or different combinations of the above gases.
4. The method according to claim 1, wherein In the plasma beam etching method, the ion beam angle is 30°-60°; Ion energy is 30V-100V; Ion acceleration bias is 50V-1000V; The gas flow rate is 10 sccm-500 sccm.
5. The method according to claim 1, wherein In the plasma beam etching method, the gas is nitrogen, oxygen, hydrogen or different combinations of the above gases.
6. The method according to claim 1, characterized in that The etching time for pre-treating the sidewall of the MTJ layer by plasma beam etching is less than or equal to 120 seconds.
7. The method according to claim 1, characterized in that The thickness of the modified layer is 1 nm to 2 nm.
8. The method according to claim 1, characterized in that The second etching process includes: Performing a second etching process using a plasma beam etching method until the substrate is exposed; In the plasma beam etching method, the ion beam angle is 10°-60°; Ion energy is 50V-600V; Ion acceleration bias is 50V-1000V; Gas flow rate is 10 sccm-500 sccm; In the plasma beam etching method, the gas is an inert gas, nitrogen, oxygen, fluorine-based gas, amino gas, carbon monoxide, carbon dioxide, alcohol gas or different combinations of the above gases.
9. The method according to claim 1, characterized in that The second etching process includes: Performing a second etching process by reactive ion etching until the substrate is exposed; In the reactive ion etching method, the source electrode power is 500W-2000W; Bias electrode power is 100W-2000W; The etching chamber pressure is 2mT-20mT; Gas flow rate is 10 sccm-500 sccm; In the reactive ion etching method, the gas is an inert gas, nitrogen, oxygen, fluorine-based gas, amino gas, carbon monoxide, carbon dioxide, alcohol gas or different combinations of the above gases.
Citation Information
Patent Citations
Method for manufacturing ultra-small magnetic random access memory array
CN111490151A