Non-volatile random access memory and methods of making the same
By employing an alcohol-based and oxidative gradient dielectric layer formation method in a non-volatile random access memory, the interface state problem between the dielectric layer and the lower electrode is solved, thereby improving the overall performance and reliability of the device.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XING ZHI CUN CHU KE JI (SU ZHOU) YOU XIAN GONG SI
- Filing Date
- 2026-05-15
- Publication Date
- 2026-07-31
AI Technical Summary
Existing non-volatile random access memories suffer from interface state problems between the dielectric layer and the lower electrode, and the uneven oxygen concentration in the dielectric layer leads to insufficient device performance and reliability.
Atomic layer deposition (ALD) is employed, using alcohols as oxidants to form a bottom dielectric layer on the surface of the lower electrode. Then, a superimposed dielectric layer with an oxygen concentration gradient is formed by using different oxidants. The quality of the dielectric layer is optimized by combining an annealing process.
It improves the interface state between the dielectric layer and the lower electrode, enhances the performance and reliability of the device, reduces precursor residue, and improves the quality and consistency of the dielectric layer.
Smart Images
Figure CN122206174B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and in particular to a non-volatile random access memory and its fabrication method. Background Technology
[0002] With the rapid development of technologies such as big data, artificial intelligence, and the Internet of Things, traditional storage architectures are facing increasingly severe challenges in terms of performance and power consumption. Currently, the memory market is mainly dominated by DRAM and NAND Flash technologies, which together account for a large market share. DRAM, as the main system memory, has the advantages of fast read and write speeds and high write / erase cycles, but its data is immediately lost after power failure (volatility), and it requires continuous refreshing to maintain data, resulting in high power consumption. NAND Flash, as the mainstream non-volatile storage solution, can retain data after power failure, but its write speed is slow (milliseconds) and its write / erase cycle life is limited (approximately 1000 cycles). 3 ~10 5 The speed requirement (speed versus non-volatility) makes it difficult to meet the needs of applications requiring frequent, high-speed data read and write operations. This contradiction between speed and non-volatility has become a key bottleneck restricting further improvements in storage system performance.
[0003] To overcome these bottlenecks, researchers have successively developed a variety of novel non-volatile memory technologies, mainly including resistive random access memory (RRAM), ferroelectric random access memory (FRAM), and phase-change random access memory (PCRAM). These novel memories all attempt to achieve read / write speeds close to DRAM while maintaining non-volatility, and also possess advantages such as low power consumption and high durability.
[0004] Reverse RAM (Resistive Random Access Memory) utilizes the reversible formation and breakage of conductive filaments in a resistive switching dielectric layer to achieve data writing and erasure. It boasts advantages such as simple structure, good compatibility with CMOS processes, and ease of 3D stacking, demonstrating significant application potential in emerging fields such as in-memory computing and AI acceleration. Ferroelectric RAM (FRAM) stores data based on the polarization reversal mechanism of ferroelectric materials, featuring fast read / write speeds, extremely low power consumption, and extremely high write / erase cycles (up to 10^10). 15 With its outstanding advantages such as high durability (e.g., multiple times), PCRAM has been widely used in fields with stringent durability requirements, such as smart cards, industrial control, and medical equipment. PCRAM utilizes the resistance difference between crystalline and amorphous states of chalcogenide phase change materials to store information, possessing characteristics such as byte addressability, non-volatility, and high density. It is already in mass production applications in data centers and consumer electronics.
[0005] The aforementioned novel memory structure still faces many technical challenges in practical applications, such as poor consistency between devices, leakage current, and unstable data retention capabilities. The yield, reliability, and performance of the devices need to be further improved.
[0006] For example, in RRAM, FRAM, PCRAM and other processes, a sandwich structure of bottom electrode / dielectric layer / top electrode is usually used. The dielectric layer is usually an oxide thin film grown by atomic layer deposition (ALD), such as... Figure 1 As shown, the lower electrode 10 is first grown on the substrate; as Figure 2 As shown, a dielectric layer 11 is then grown on the lower electrode 10; as Figure 3 As shown, the upper electrode 12 is finally grown on the dielectric layer 11. Ideally, when growing the dielectric layer 11, there are no interface state problems between the dielectric layer 11 and the lower electrode 10. However, in practice, since the ALD growth temperature is typically between 200°C and 350°C, ... Figure 4 As shown, oxygen ions in the introduced oxidant will oxidize the lower electrode 10, forming a lower electrode oxide layer 13 on the surface of the lower electrode 10. Oxygen ions can even penetrate to a relatively deep position through the grain boundaries of the lower electrode 10, thus introducing a large number of defects 14 at the interface. In particular, when the device is erased or written, oxygen ions will leave their original position and return to the dielectric layer 11 due to the electric field, changing the distribution of oxygen in the dielectric layer 11, thereby affecting the performance and reliability of the device.
[0007] Furthermore, traditional fabrication methods produce dielectric layers with uniform oxygen concentrations. For RRAM devices, this makes it difficult to control the morphology of the conductive filaments, affecting device yield, performance, and reliability. Since ALD processes involve atomically layer-by-layer growth, conventional methods such as shortening the growth time of existing oxidant precursors or reducing gas flow rates to decrease oxygen concentration in the dielectric layer can easily lead to some metal precursors failing to oxidize, resulting in metal precursor residues, increased defects, and ultimately, leakage under initial conditions. Summary of the Invention
[0008] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a non-volatile random access memory and its fabrication method, which solves the interface state problem between the dielectric layer and the lower electrode in the prior art non-volatile random access memory devices, and the problem of how to form a dielectric layer with oxygen concentration variation.
[0009] To achieve the above and other related objectives, the present invention provides a method for fabricating a non-volatile random access memory, the method comprising:
[0010] A substrate is provided, and a lower electrode is formed on the substrate;
[0011] An atomic layer deposition process is used to form a bottom dielectric layer on the surface of the lower electrode. The oxidant used to form the bottom dielectric layer is an alcohol, and the alcohol reacts fully with the precursor.
[0012] An atomic layer deposition process is used to form a number of stacked dielectric layers on the surface of the bottom dielectric layer; wherein the bottom dielectric layer and all the stacked dielectric layers constitute the device dielectric layer of a non-volatile random access memory, and the oxygen concentration of the bottom dielectric layer is the lowest among the device dielectric layers, while the oxygen concentration of at least one of the stacked dielectric layers is greater than that of the bottom dielectric layer.
[0013] An upper electrode is formed on the surface of the dielectric layer of the device.
[0014] Optionally, the alcohol is ethanol.
[0015] Furthermore, when the oxygen concentration of the superimposed medium layer is greater than that of the bottom medium layer, the oxidant used to form the superimposed medium layer is water, oxygen, hydrogen peroxide, and / or ozone; when the oxygen concentration of the superimposed medium layer is equal to that of the bottom medium layer, the oxidant used to form the superimposed medium layer is the alcohol.
[0016] Furthermore, the non-volatile random access memory is RRAM, the oxygen concentration of all the superimposed dielectric layers is greater than that of the bottom dielectric layer, and the oxygen concentration of the superimposed dielectric layers gradually increases along the direction from the lower electrode to the upper electrode.
[0017] Furthermore, the oxygen concentration of the superimposed dielectric layer gradually increases along the direction from the lower electrode to the upper electrode by means that the higher the oxygen concentration, the stronger the oxidizing agent used in the formation of the superimposed dielectric layer.
[0018] Optionally, after forming the dielectric layer of the device, an annealing process is further included, and the annealing process is carried out in an oxygen atmosphere.
[0019] Optionally, the annealing process uses a temperature of 250℃~300℃ and a time of 1 second~10 minutes.
[0020] The present invention also provides a non-volatile random access memory, the memory comprising:
[0021] Lower electrode;
[0022] A device dielectric layer is located on the surface of the lower electrode. The device dielectric layer includes a bottom dielectric layer and at least one stacked dielectric layer. The bottom dielectric layer is located on the surface of the lower electrode, and all the stacked dielectric layers are sequentially stacked on the bottom dielectric layer. The device dielectric layer is formed by atomic layer deposition. The bottom dielectric layer is grown using an alcohol as an oxidant. The bottom dielectric layer has the lowest oxygen concentration among all the device dielectric layers. At the same time, the oxygen concentration of at least one of the stacked dielectric layers is greater than that of the bottom dielectric layer.
[0023] The upper electrode is located on the surface of the dielectric layer of the device.
[0024] Optionally, the device dielectric layer includes HfO. x HZO, AlO x TiO x Or TaO x One or more of the following, where x is greater than 0.
[0025] Optionally, the non-volatile random access memory is RRAM, and the oxygen concentration of all the superimposed dielectric layers is greater than that of the bottom dielectric layer, and the oxygen concentration of the superimposed dielectric layers gradually increases along the direction from the lower electrode to the upper electrode.
[0026] Optionally, the thickness of the dielectric layer of the device is 4 nm to 20 nm.
[0027] Optionally, the lower electrode is a TiN layer, and the upper electrode is a stacked structure of Ti layer / TiN layer.
[0028] As described above, the non-volatile random access memory and its fabrication method of the present invention have the following beneficial effects:
[0029] This invention employs atomic layer deposition (ALD) to fabricate the dielectric layer of a device. By using a weakly oxidizing alcohol as an oxidant to prepare the dielectric layer closest to the lower electrode, the oxidation of the lower electrode is reduced or even avoided. Simultaneously, the entry of oxygen from the oxidant into the lower electrode is reduced or even prevented, thereby improving the interface state problem between the dielectric layer and the lower electrode. Furthermore, using a weakly oxidizing alcohol as an oxidant also allows for the growth of a bottom dielectric layer with the lowest oxygen concentration. Combined with existing oxidants, this creates a dielectric layer with varying oxygen concentration, providing a feasible technical solution for fabricating a dielectric layer with adjustable oxygen concentration in non-volatile random access memory (NRAM). Moreover, using a weakly oxidizing alcohol as an oxidant effectively reduces oxygen concentration while fully oxidizing the metal precursor, reducing precursor residue and improving the quality of the dielectric layer, thus enhancing the overall performance of the device. Attached Figure Description
[0030] Figures 1 to 4The diagram shows a cross-sectional view of each step in the fabrication method of a non-volatile random access memory in the prior art.
[0031] Figures 5 to 12 The diagram shows a cross-sectional view of each step in the fabrication method of the non-volatile random access memory of the present invention.
[0032] Component designation explanation 10. Bottom electrode; 11. Dielectric layer; 12. Top electrode; 13. Bottom electrode oxide layer; 14. Defect; 20. Substrate; 30. Bottom electrode; 40. Device dielectric layer; 41. Bottom dielectric layer; 42. Stacked dielectric layer; 420. First stacked dielectric layer; 421. Second stacked dielectric layer; 422. Third stacked dielectric layer; 423. Fourth stacked dielectric layer; 43. Annealed layer; 50. Top electrode; 51. Ti layer; 52. TiN layer. Detailed Implementation
[0033] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.
[0034] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, whole, step, or component, but does not exclude the presence or addition of one or more other features, wholes, steps, or components.
[0035] Features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.
[0036] In the detailed description of embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged and not to scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.
[0037] For ease of description, spatial relation terms such as “below,” “under,” “lower than,” “below,” “above,” and “upper” may be used herein to describe the relationship between one element or feature shown in the accompanying drawings and other elements or features. It will be understood that these spatial relation terms are intended to include directions other than those depicted in the drawings for devices in use or operation. Furthermore, when a layer is referred to as being “between” two layers, it may be the only layer between the two layers, or there may be one or more layers in between.
[0038] In the context of this application, the structure described above the first feature may include embodiments in which the first and second features are formed in direct contact, or embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.
[0039] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.
[0040] Example 1
[0041] This embodiment provides a method for fabricating a non-volatile random access memory, the method comprising the following steps:
[0042] S1, providing a substrate and forming a lower electrode on the substrate;
[0043] S2, an atomic layer deposition process is used to form a bottom dielectric layer on the surface of the lower electrode, wherein the oxidant used to form the bottom dielectric layer is an alcohol, and the alcohol reacts fully with the precursor.
[0044] S3, using atomic layer deposition to form the required number of stacked dielectric layers on the surface of the bottom dielectric layer; wherein, the bottom dielectric layer and all the stacked dielectric layers constitute the device dielectric layer of a non-volatile random access memory, and the oxygen concentration of the bottom dielectric layer is the lowest among the device dielectric layers, while at least one of the stacked dielectric layers has a higher oxygen concentration than the bottom dielectric layer.
[0045] S4, an upper electrode is formed on the surface of the dielectric layer of the device.
[0046] The non-volatile random access memory (NRAM) fabrication method of this embodiment, when using atomic layer deposition (ALD) to fabricate the device dielectric layer, employs a weakly oxidizing alcohol as an oxidant to prepare the dielectric layer closest to the lower electrode. This reduces or even prevents the lower electrode from being oxidized, and simultaneously reduces or even prevents oxygen from the oxidant from entering the lower electrode, thereby improving the interface state problem between the device dielectric layer and the lower electrode. Furthermore, using a weakly oxidizing alcohol as an oxidant also allows for the growth of a bottom dielectric layer with the lowest oxygen concentration. Combined with existing oxidants, this forms a device dielectric layer with varying oxygen concentration, providing a feasible technical solution for fabricating a dielectric layer with adjustable oxygen concentration in non-volatile random access memory. Moreover, using a weakly oxidizing alcohol as an oxidant can effectively reduce oxygen concentration while fully oxidizing the metal precursor, reducing precursor residue, improving the quality of the dielectric layer, and thus enhancing the overall performance of the device.
[0047] The method for fabricating the non-volatile random access memory of this embodiment will be described in detail below with reference to the specific accompanying drawings.
[0048] like Figure 5 As shown, step S1 is performed first, a substrate 20 is provided, and a lower electrode 30 is formed on the substrate 20;
[0049] The substrate 20 serves as the carrier layer of the non-volatile random access memory. It can be made of commonly used substrate materials in the field, such as semiconductor substrates or insulating substrates, or it can be a metal interconnect layer of a chip. Other active devices and / or passive devices can be formed therein. It can be a single-layer structure or a composite structure, depending on the actual needs.
[0050] The lower electrode 30 can be formed using physical vapor deposition processes, such as electron beam evaporation and magnetron sputtering, or it can be formed using atomic layer deposition or chemical vapor deposition processes; no excessive restrictions are imposed here. The material of the lower electrode 30 can be titanium (Ti), tantalum (Ta), tungsten (W), ruthenium (Ru), iridium (Ir), aluminum (Al), copper (Cu), titanium nitride (TiN), tantalum nitride (TaN), or platinum (Pt), etc.; no excessive restrictions are imposed here, as long as the device's requirements for electrode conductivity are met. To reduce costs or better compatibility with CMOS processes, the lower electrode 30 in this embodiment is preferably a TiN layer.
[0051] like Figure 6 As shown, step S2 is then performed, in which an atomic layer deposition process is used to form a bottom dielectric layer 41 on the surface of the lower electrode 30. The oxidant used to form the bottom dielectric layer 41 is an alcohol, and the alcohol reacts fully with the precursor.
[0052] The alcohols used are not overly limited here; they can be fatty alcohols such as methanol and ethanol, polyols such as ethylene glycol and glycerol, or aromatic alcohols, etc. Considering cost, safety, and oxidizing power, ethanol is preferred in this embodiment. Compared to strong oxidants such as water and ozone, ethanol has a milder oxidizing effect. At the reaction temperature of the atomic layer deposition process, ethanol will only react fully with the metal precursor to achieve oxidation, without oxidizing the lower electrode below, nor will it penetrate along the grain boundaries of the lower electrode and introduce a large number of interface defects. This reduces or even prevents oxygen elements in the lower electrode from leaving their original positions and returning to the device dielectric layer due to the electric field during the erase / write process, thus changing the oxygen distribution in the device dielectric layer and effectively improving the interface state problem between the device dielectric layer and the lower electrode. Furthermore, since alcohols, such as ethanol, have a milder oxidizing effect compared to strong oxidants such as water and ozone, even though all metal precursors can be oxidized after ethanol reacts fully with the metal precursors at the reaction temperature of the atomic layer deposition process, the oxygen concentration is lower. Then, by using existing strong oxidants, a device dielectric layer with varying oxygen concentration can be achieved, providing a feasible technical solution for preparing a dielectric layer with adjustable oxygen concentration in non-volatile random access memory.
[0053] As an example, the material of the bottom dielectric layer 41 is preferably a transition metal oxide, such as HfO. x HZO, AlO x TiO x Or TaO x One or more of the following, wherein x is greater than 0. The precursor is a transition metal precursor, with HfO as an example. x For example, the precursor can be tetra(dimethylamino)hafnium or tetra(ethylmethylamino)hafnium, etc.
[0054] As an example, in the process of forming the bottom dielectric layer 41 using atomic layer deposition, in each atomic layer deposition cycle, a precursor is first introduced and adsorbed on the surface of the lower electrode 30, then excess precursor is removed by purging, and then ethanol is introduced as an oxidant. The purging time is ensured so that the ethanol can fully oxidize the precursor, thereby obtaining the bottom dielectric layer 41 with the lowest oxygen concentration and avoiding precursor residue, thus improving the quality of the bottom dielectric layer 41.
[0055] like Figure 7As shown, step S3 is then performed, in which an atomic layer deposition process is used to form the required number of stacked dielectric layers 42 on the surface of the bottom dielectric layer 41; wherein, the bottom dielectric layer 41 and all the stacked dielectric layers 42 constitute the device dielectric layer 40 of the non-volatile random access memory, and the oxygen concentration of the bottom dielectric layer 41 in the device dielectric layer 40 is the lowest, while the oxygen concentration of at least one of the stacked dielectric layers 42 is greater than that of the bottom dielectric layer 41.
[0056] The number of layers in the superimposed dielectric layer 42 can be selected according to the actual needs of oxygen concentration distribution in the device dielectric layer. It can be one, two, three, four, or more layers. For example, Figure 7 As shown, only one layer of the superimposed dielectric layer 42 can be grown on the bottom dielectric layer 41, and the oxygen concentration in the superimposed dielectric layer 42 is greater than the oxygen concentration in the bottom dielectric layer 41; alternatively, two layers of the superimposed dielectric layer 42 can be grown on the bottom dielectric layer 41, for example, in... Figure 8 A second stacked dielectric layer 421 is grown on the first stacked dielectric layer 420, resulting in a total of two stacked dielectric layers 42. The oxygen concentration in the first stacked dielectric layer 420 is greater than the oxygen concentration in the bottom dielectric layer 41. The oxygen concentration in the second stacked dielectric layer 421 can be greater than or less than the oxygen concentration in the first stacked dielectric layer 420, for example, equal to the oxygen concentration in the bottom dielectric layer 41. Figure 9 As shown, three or more layers of the superimposed dielectric layer 42 can also be grown on the bottom dielectric layer 41. The oxygen concentration in adjacent layers of the superimposed dielectric layer 42 can be different. The oxygen concentration in each layer of the superimposed dielectric layer 42 can be greater than or equal to the oxygen concentration in the bottom dielectric layer 41.
[0057] As an example, when the oxygen concentration of the superimposed dielectric layer 42 is greater than that of the bottom dielectric layer 41, the oxidant used to form the superimposed dielectric layer 42 is water, oxygen, hydrogen peroxide, and / or ozone; of course, any other suitable oxidant can also be selected. When the oxygen concentration of the superimposed dielectric layer 42 is equal to that of the bottom dielectric layer 41, the oxidant used to form the superimposed dielectric layer 42 is the alcohol. By using different oxidants to control the oxygen concentration change in the device dielectric layer 40, a feasible technical solution can be provided for preparing a dielectric layer with adjustable oxygen concentration in non-volatile random access memory.
[0058] like Figure 10As shown, taking the non-volatile random access memory (RRAM) as an example, the oxygen concentration of all the superimposed dielectric layers 42 can be selected to be greater than that of the bottom dielectric layer 41, and the oxygen concentration of the superimposed dielectric layers 42 gradually increases along the direction from the bottom electrode 30 to the top electrode 50, thereby forming the device dielectric layer 40 composed of the bottom dielectric layer 41 and the superimposed dielectric layer 42, where the oxygen concentration increases sequentially from the bottom electrode to the top electrode. This gradient oxygen concentration distribution can induce the conductive filaments to be oriented along the thickness direction to form a morphology that is thicker at the top and thinner at the bottom, avoiding disordered morphology of the conductive filaments and improving the consistency and stability of the device.
[0059] The oxygen concentration of the superimposed dielectric layer 42 gradually increases along the direction from the lower electrode 30 to the upper electrode 50 by using a stronger oxidant during the formation of the superimposed dielectric layer 42 with a higher oxygen concentration. By changing the oxidant to different oxidants, multiple layers of the superimposed dielectric layer 42 are sequentially deposited on the surface of the bottom dielectric layer 41. The superimposed dielectric layer 42 with a higher oxygen concentration uses a stronger oxidant during preparation. Since the oxidizing power of water, oxygen, hydrogen peroxide, and ozone increases sequentially, one to four layers of the superimposed dielectric layer 42 can be deposited. If only one layer of the superimposed dielectric layer 42 is deposited, any one of water, oxygen, hydrogen peroxide, or ozone can be selected for growth. If two layers of the superimposed dielectric layer 42 are deposited, two different oxidants can be selected from the four oxidants. For example, the first superimposed dielectric layer 420 can use water as the oxidant, while the second superimposed dielectric layer 421 needs to use one of oxygen, hydrogen peroxide, or ozone, which has a higher oxidizing power than water, as the oxidant. Figure 10 As shown, if four layers of the superimposed dielectric layer 42 are deposited, the first superimposed dielectric layer 420 selects water as the oxidant, the second superimposed dielectric layer 421 selects oxygen as the oxidant, the third superimposed dielectric layer 422 selects hydrogen peroxide as the oxidant, and the fourth superimposed dielectric layer 423 selects ozone as the oxidant. This allows the oxygen concentration of the superimposed dielectric layer 42 to gradually increase along the direction from the lower electrode 30 to the upper electrode 50.
[0060] Of course, depending on actual needs, the oxygen concentration of all the superimposed dielectric layers 42 can be gradually reduced along the direction from the lower electrode 30 to the upper electrode 50, inducing the conductive filaments to form a shape that is thicker at the bottom and thinner at the top. No excessive restrictions are imposed here.
[0061] As an example, the material of the superimposed dielectric layer 42 is preferably a transition metal oxide, such as HfO. x HZO, AlO x TiO x Or TaO xOne or more of the following, wherein x is greater than 0. For RRAM, the bottom dielectric layer 41 and the superimposed dielectric layer 42 are preferably made of the same material, more preferably HfO. x Where x is greater than 0, the oxygen concentration in the device dielectric layer varies depending on the oxidant, and its range can be selected as the ratio of metal atoms to oxygen atoms of 1:1 to 1:3. For example, the ratio of metal atoms to oxygen atoms in the bottom dielectric layer 41 is 1:1 to 1:2, and the ratio of metal atoms to oxygen atoms in the superimposed dielectric layer 42 is 1:2 to 1:3.
[0062] like Figure 11 As shown, after forming the device dielectric layer 40, an annealing process is further included. This annealing process is carried out in an oxygen atmosphere to reduce dangling bonds on the upper surface of the device dielectric layer 40, or to replace impurities such as hydrogen or carbon on the upper surface of the device dielectric layer 40, thereby improving the density and uniformity of the dielectric layer. Simultaneously, it can further increase the oxygen concentration on the upper surface of the device dielectric layer 40, thus forming an annealed layer 43 with a higher oxygen concentration. The annealing temperature and time can be designed according to actual needs; for example, the annealing temperature can be set to 250℃~300℃, and the annealing time can be set to 1 second~10 minutes.
[0063] The thickness of the device dielectric layer 40 can be selected from 4nm to 20nm. The thickness of the bottom dielectric layer 41 and each of the stacked dielectric layers 42 is not excessively limited and can be selected according to actual design needs. For example, the total thickness of the device dielectric layer 40 can be selected as 6nm, the thickness of the bottom dielectric layer 41 is 1nm to 2nm, and the thickness of all the stacked dielectric layers 42 is 4nm to 5nm.
[0064] like Figure 12 As shown, step S4 is performed to form the upper electrode 50 on the surface of the device dielectric layer 40. The material of the upper electrode 50 can be titanium (Ti), tantalum (Ta), tungsten (W), ruthenium (Ru), iridium (Ir), aluminum (Al), copper (Cu), titanium nitride (TiN), tantalum nitride (TaN), or platinum (Pt), depending on the actual needs. As a preferred example, the upper electrode 50 is preferably a stacked structure of Ti layer 51 / TiN layer 52, wherein Ti layer 51 serves as an oxygen storage layer. Oxygen ions in the device dielectric layer migrate to Ti layer 51 under the action of the electrode and are stored in Ti layer 51, preventing them from re-entering the device dielectric layer during subsequent device operation and affecting the distribution of oxygen vacancy concentration, thereby ensuring the stability of oxygen vacancy concentration distribution and improving the yield, performance, and reliability of the device.
[0065] Example 2
[0066] This embodiment provides a non-volatile random access memory (RAM). This RAM can be fabricated using the method described in Embodiment 1. Therefore, information regarding the materials and fabrication process of the RAM can be found in Embodiment 1. Of course, other fabrication processes can also be used as needed, as long as the RAM can be formed. The beneficial effects of this RAM can be found in Embodiment 1, and will not be repeated below.
[0067] like Figures 5 to 12 As shown, the memory includes:
[0068] Lower electrode 30;
[0069] A device dielectric layer 40 is located on the surface of the lower electrode 30. The device dielectric layer 40 includes a bottom dielectric layer 41 and at least one stacked dielectric layer 42. The bottom dielectric layer 41 is located on the surface of the lower electrode 30, and all the stacked dielectric layers 42 are sequentially stacked on the bottom dielectric layer 41. The device dielectric layer 40 is formed by atomic layer deposition, and the bottom dielectric layer 41 is grown using an alcohol as an oxidant. The bottom dielectric layer 41 has the lowest oxygen concentration among the device dielectric layers 40, and at least one of the stacked dielectric layers 42 has a higher oxygen concentration than the bottom dielectric layer 41.
[0070] The upper electrode 50 is located on the surface of the dielectric layer 40 of the device.
[0071] As an example, the device dielectric layer 40 includes HfO. x HZO, AlO x TiO x Or TaO x One or more of the following, where x is greater than 0.
[0072] As an example, the non-volatile random access memory is RRAM, the oxygen concentration of all the superimposed dielectric layers 42 is greater than that of the bottom dielectric layer 41, and the oxygen concentration of the superimposed dielectric layers 42 gradually increases along the direction from the lower electrode 30 to the upper electrode 50.
[0073] As an example, the thickness of the dielectric layer 40 of the device is 4nm to 20nm.
[0074] As an example, the lower electrode 30 is a TiN layer, and the upper electrode 50 is a stacked structure of Ti layer 51 / TiN layer 52.
[0075] In summary, this invention provides a non-volatile random access memory (RAM) and its fabrication method. When fabricating the device dielectric layer using atomic layer deposition (ALD), a weakly oxidizing alcohol is used as the oxidant to prepare the dielectric layer closest to the lower electrode. This reduces or even prevents the lower electrode from being oxidized, and simultaneously reduces or even prevents oxygen from the oxidant from entering the lower electrode, thereby improving the interface state problem between the device dielectric layer and the lower electrode. Furthermore, using a weakly oxidizing alcohol as the oxidant also allows for the growth of a bottom dielectric layer with the lowest oxygen concentration. Combined with existing oxidants, this forms a device dielectric layer with varying oxygen concentration, providing a feasible technical solution for fabricating a dielectric layer with adjustable oxygen concentration in non-volatile RAM. Moreover, using a weakly oxidizing alcohol as the oxidant can effectively reduce oxygen concentration while fully oxidizing the metal precursor, reducing precursor residue and improving the quality of the dielectric layer, thereby enhancing the overall performance of the device.
[0076] Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.
[0077] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.
Claims
1. A method for manufacturing a nonvolatile random access memory, characterized by: The preparation method includes: A substrate is provided, and a lower electrode is formed on the substrate; An atomic layer deposition process is used to form a bottom dielectric layer on the surface of the lower electrode. The oxidant used to form the bottom dielectric layer is an alcohol, and the alcohol reacts fully with the precursor. An atomic layer deposition process is used to form a number of stacked dielectric layers on the surface of the bottom dielectric layer; wherein the bottom dielectric layer and all the stacked dielectric layers constitute the device dielectric layer of a non-volatile random access memory, and the oxygen concentration of the bottom dielectric layer is the lowest among the device dielectric layers, while the oxygen concentration of at least one of the stacked dielectric layers is greater than that of the bottom dielectric layer. An upper electrode is formed on the surface of the dielectric layer of the device.
2. The method of claim 1, wherein: The alcohol is ethanol.
3. The method of claim 1 or 2, wherein: When the oxygen concentration of the superimposed medium layer is greater than that of the bottom medium layer, the oxidant used to form the superimposed medium layer is water, oxygen, hydrogen peroxide, and / or ozone; when the oxygen concentration of the superimposed medium layer is equal to that of the bottom medium layer, the oxidant used to form the superimposed medium layer is the alcohol.
4. The method of claim 3, wherein: The non-volatile random access memory is RRAM, and the oxygen concentration of all the superimposed dielectric layers is greater than that of the bottom dielectric layer. Furthermore, the oxygen concentration of the superimposed dielectric layers gradually increases along the direction from the bottom electrode to the top electrode.
5. The method of claim 4, wherein: The oxygen concentration of the superimposed dielectric layer gradually increases along the direction from the lower electrode to the upper electrode by means that the higher the oxygen concentration, the stronger the oxidizing agent used in the formation of the superimposed dielectric layer.
6. The method of claim 1, wherein: After the dielectric layer of the device is formed, an annealing process is also included, and the annealing process is carried out in an oxygen atmosphere.
7. The method of claim 6, wherein: The annealing process uses a temperature of 250℃~300℃ and a time of 1 second~10 minutes.
8. A non-volatile random access memory, comprising: The memory includes: Lower electrode; A device dielectric layer is located on the surface of the lower electrode. The device dielectric layer includes a bottom dielectric layer and at least one stacked dielectric layer. The bottom dielectric layer is located on the surface of the lower electrode, and all the stacked dielectric layers are sequentially stacked on the bottom dielectric layer. The device dielectric layer is formed by atomic layer deposition. The bottom dielectric layer is grown using an alcohol as an oxidant. The bottom dielectric layer has the lowest oxygen concentration among all the device dielectric layers. At the same time, the oxygen concentration of at least one of the stacked dielectric layers is greater than that of the bottom dielectric layer. The upper electrode is located on the surface of the dielectric layer of the device.
9. The nonvolatile random access memory of claim 8, wherein: The dielectric layer of the device includes HfO. x HZO, AlO x TiO x Or TaO x One or more of the following, where x is greater than 0.
10. The nonvolatile random access memory of claim 8, wherein: The non-volatile random access memory is RRAM, and the oxygen concentration of all the superimposed dielectric layers is greater than that of the bottom dielectric layer. Furthermore, the oxygen concentration of the superimposed dielectric layers gradually increases along the direction from the bottom electrode to the top electrode.
11. The nonvolatile random access memory of claim 8, wherein: The thickness of the dielectric layer of the device is 4nm to 20nm.
12. The nonvolatile random access memory of claim 8, wherein: The lower electrode is a TiN layer, and the upper electrode is a stacked structure of Ti layer / TiN layer.