Protruding liner on the side wall of a phase-change memory cell

Abstract

A phase change memory (PCM) cell having a mushroom structure includes a first electrode, a heater electrically connected to the first electrode, a first protruding liner electrically connected to the heater, a PCM material electrically connected to the first protruding liner, a second electrode electrically connected to the PCM material, and a second protruding liner electrically connected to the first protruding liner and the second electrode.

Description

Technical Field

[0001] The present invention relates to computer memory, and more particularly to a phase change material memory device having a protruding liner.

[0002] Phase Change Memory (PCM) can be used for both training and inference in analog computing for artificial intelligence. The PCM structure can include a phase change memory cell device with an adjustable conductivity and an overall high device resistance with a high retention force to minimize energy consumption. The adjustment can be achieved by changing the ratio of the crystalline and amorphous phases of the PCM material to form different structural states. However, the PCM material can be affected by resistance drift and can adversely affect the fidelity of the adjustment.

Summary of the Invention

[0003] According to an embodiment of the present disclosure, a PCM cell having a mushroom structure includes a first electrode, a heater electrically connected to the first electrode, a first protruding liner electrically connected to the heater, a PCM material electrically connected to the first protruding liner, a second electrode electrically connected to the PCM material, and a second protruding liner electrically connected to the first protruding liner and the second electrode.

[0004] According to an embodiment of the present disclosure, a PCM cell includes a first electrode, a first protruding liner electrically connected to the first electrode (the first protruding liner including a first material), a PCM material electrically connected to the first protruding liner, a second electrode electrically connected to the PCM material, and a second protruding liner electrically connected to the first protruding liner and the second electrode (the second protruding liner including a second material), and the second material is different from the first material.

[0005] According to embodiments of the present disclosure, a method for manufacturing a PCM cell includes the steps of forming a first electrode, forming a first protruding liner electrically connected to the first electrode, forming a PCM material on the first protruding liner, forming a second electrode on the PCM material, and forming a second protruding liner (in contact with the first protruding liner, the PCM material, and the second electrode). [Brief explanation of the drawing]

[0006] [Figure 1A] This is a cross-sectional view of a PCM cell including a sidewall protruding liner according to an embodiment of the present disclosure.

[0007] [Figure 1B] This is a cross-sectional view of the PCM cell of Figure 1A, which includes a smaller amorphous region, according to an embodiment of the present disclosure.

[0008] [Figure 1C] This is a cross-sectional view of the PCM cell of Figure 1A, which includes a larger amorphous region, according to an embodiment of the present disclosure.

[0009] [Figure 2] This is a flowchart of a method for manufacturing the PCM cell shown in Figure 1A according to an embodiment of the present disclosure.

[0010] [Figure 3A] Figure 2 shows a series of cross-sectional views of the method for manufacturing a PCM cell according to an embodiment of the present disclosure. [Figure 3B] Figure 2 shows a series of cross-sectional views of the method for manufacturing a PCM cell according to an embodiment of the present disclosure. [Figure 3C] Figure 2 shows a series of cross-sectional views of the method for manufacturing a PCM cell according to an embodiment of the present disclosure. [Figure 3D] Figure 2 shows a series of cross-sectional views of the method for manufacturing a PCM cell according to an embodiment of the present disclosure. [Figure 3E] Figure 2 shows a series of cross-sectional views of the method for manufacturing a PCM cell according to an embodiment of the present disclosure. [Figure 3F]Figure 2 shows a series of cross-sectional views of the method for manufacturing a PCM cell according to an embodiment of the present disclosure. [Figure 3G] Figure 2 shows a series of cross-sectional views of the method for manufacturing a PCM cell according to an embodiment of the present disclosure. [Figure 3H] Figure 2 shows a series of cross-sectional views of the method for manufacturing a PCM cell according to an embodiment of the present disclosure. [Figure 3I] Figure 2 shows a series of cross-sectional views of the method for manufacturing a PCM cell according to an embodiment of the present disclosure.

[0011] [Figure 4A] Figure 1A shows a graph of resistance versus current for various liner electrical resistivity of the PCM cell according to an embodiment of the present disclosure.

[0012] [Figure 4B] Figure 1A shows a graph of resistance versus current for various liner thickness ratios of the PCM cell according to an embodiment of the present disclosure. [Modes for carrying out the invention]

[0013] Various embodiments of this disclosure are described herein with reference to the relevant drawings. Alternative embodiments can be devised without departing from the scope of this disclosure. Note that various connections and positional relationships (e.g., above, below, adjacent, etc.) are shown between elements in the following description and drawings. These connections and / or positional relationships may be direct or indirect unless otherwise specified, and this disclosure is not intended to limit them in this respect. Thus, a joining of entities may refer to either a direct or indirect joining, and a positional relationship between entities may be a direct or indirect positional relationship. As an example of an indirect positional relationship, a reference herein to forming layer "A" above layer "B" includes a situation in which one or more intermediate layers (e.g., layers "C" and "D") are between layers "A" and "B", provided that the relevant properties and functions of layers "A" and "B" are not substantially altered by the intermediate layers.

[0014] The following definitions and abbreviations are for use in interpreting the claims and specification. Where used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having,” “contains,” or “containing,” or any other variation thereof, are intended to encompass non-exclusive inclusion. For example, a composition, mixture, process, method, article, or apparatus containing a list of elements is not necessarily limited to those elements alone, but may include other elements not expressly listed, or other elements specific to such composition, mixture, process, method, article, or apparatus. Furthermore, any numerical ranges included herein, unless otherwise expressly stated, include their boundaries.

[0015] For the purposes of the following explanation, the terms “upper,” “lower,” “right,” “left,” “vertical,” “horizontal,” “top,” and “bottom,” and their derivatives, shall be used in relation to the structures and methods described, as oriented within the drawings. The terms “overlying,” “atop,” “on top,” “positioned on,” or “positioned atop” mean that a first element, such as a first structure, is located on a second element, such as a second structure, and an intervening element, such as an interface structure, may be located between the first and second elements. The term “direct contact” means that a first element, such as a first structure, and a second element, such as a second structure, are connected at the contact surface of the two elements without any intermediate conductive, insulating, or semiconductor layers. For example, the term "selective" in phrases like "a first element selective to a second element" means that the first element can be etched and the second element can act as an etch stop.

[0016] For the sake of brevity, the prior art related to the manufacture of semiconductor devices and integrated circuits (ICs) may or may not be described in detail herein. Further, the various tasks and process steps described herein can be incorporated into more comprehensive procedures or processes having additional steps or functions not described in detail herein. Specifically, since the various steps in the manufacture of semiconductor devices and semiconductor-based ICs are well known, for the sake of brevity, many of the conventional steps will only be briefly described herein or completely omitted without providing details of well-known processes.

[0017] Generally, the various processes used to form microchips that are packaged into ICs are classified into four general categories: namely, film deposition, removal / etching, semiconductor doping, and patterning / lithography.

[0018] Deposition can be any process of growing, coating, or otherwise transferring a material onto a wafer. Available techniques include Physical Vapor Deposition (PVD), Chemical Vapor Deposition (CVD), Electrochemical Deposition (ECD), Molecular Beam Epitaxy (MBE), and more recently Atomic Layer Deposition (ALD). Another deposition technique is Plasma Enhanced Chemical Vapor Deposition (PECVD), which is a process that uses the energy in a plasma to induce reactions on the wafer surface that would normally require higher temperatures associated with conventional CVD. The electrical and mechanical properties of the film can also be improved by the high-energy ion bombardment during PECVD deposition.

[0019] Removal / etching can be any process that removes material from a wafer. Examples include etching processes (either wet or dry), Chemical Mechanical Planarization (CMP), and the like. An example of a removal process is Ion Beam Etching (IBE). Generally, IBE (or milling) refers to a dry plasma etching method that utilizes a remote broad beam ion / plasma source to remove substrate material by means of a physically inert gas and / or a chemically reactive gas means. Like other dry plasma etching techniques, IBE has advantages such as etching rate, anisotropy, selectivity, uniformity, aspect ratio, and minimization of substrate damage. Another example of a dry removal process is Reactive Ion Etching (RIE). Generally, RIE uses a chemically reactive plasma to remove material deposited on a wafer. In RIE, the plasma is generated by an electromagnetic field under low pressure (vacuum). High energy ions from the RIE plasma attack the wafer surface and react with the wafer surface to remove the material.

[0020] Semiconductor doping can be, for example, generally a modification of electrical characteristics by doping the source and drain of a transistor, for example, by diffusion and / or ion implantation. Following these doping processes, furnace annealing or Rapid Thermal Annealing ("RTA") is performed. Annealing helps to activate the implanted dopants. To connect and insulate transistors and their components, films of both conductors (e.g., polysilicon, aluminum, copper, etc.) and insulators (e.g., various forms of silicon dioxide, silicon nitride, etc.) are used. By selectively doping various regions of a semiconductor substrate, the conductivity of the substrate can be changed by applying a voltage. By creating the structures of these various components, millions of transistors can be constructed and wired together to form the complex circuits of state-of-the-art microelectronic devices.

[0021] Semiconductor lithography allows for the formation of three-dimensional relief images or patterns on a semiconductor substrate, and then the transfer of these patterns to the substrate. In semiconductor lithography, patterns are formed using a photosensitive polymer called photoresist. The lithography and etching pattern transfer steps are repeated multiple times to construct the complex structures that make up transistors and the numerous wires that connect millions of transistors in a circuit. Each pattern printed on the wafer is aligned with previously formed patterns, and conductors, insulators, and selectively doped areas are gradually constructed to form the final device.

[0022] Figures 1A to 1C are cross-sectional views of a PCM cell 100 for use in an integrated circuit (not shown), for example. In the illustrated embodiment, the PCM cell 100 comprises a bottom wiring 102, a bottom electrode 104, an insulator 106, a heater 108, an insulator 110, a bottom protruding liner (PL) 112, a PCM material 114, a side wall PL 116, an insulator 120, an upper electrode 122, and an upper wiring 124.

[0023] In the illustrated embodiment, the bottom of the bottom electrode 104 is in direct contact with and electrically connected to the top of the bottom wiring 102, which can receive electrical signals from other components of the integrated circuit (not shown). The bottom of the heater 108 is in direct contact with and electrically connected to the top of the bottom electrode 104. The bottom of the bottom PL 112 is in direct contact with and electrically and thermally connected to the top of the heater 108. The bottom of the PCM material 114 is in direct contact with and electrically and thermally connected to the top of the bottom PL 112. The bottom of the top electrode 122 is in direct contact with and electrically connected to the top of the PCM material 114. The bottom of the top wiring 124 is in direct contact with and electrically connected to the top of the top electrode 122, and the top wiring 124 can transmit electrical signals from the PCM cell 100 to other components of the integrated circuit (not shown).

[0024] In the illustrated embodiment, the lowest part of the side wall PL116 is in direct contact with the uppermost part of the lowermost PL112 and is electrically and thermally connected. Furthermore, the inside of the side wall PL116 is in direct contact with the outside of the PCM material 114 and is electrically and thermally connected, so that the side wall PL116 laterally surrounds the outside of the PCM material 114. Thereafter, the side wall PL116 surrounds all parallel sides in one direction along the entire longitudinal length of the PCM material 114 (e.g., the vertically extending sides as shown in Figure 1A) and is adjacent to the end of the PCM material 114 covered by the lowermost PL112 (e.g., the horizontally extending lowermost part as shown in Figure 1A). In the illustrated embodiment, the PCM material 114 has a cylindrical shape (e.g., as opposed to a prismatic shape), which means that it is surrounded on only one lateral outer side. Furthermore, the inside of the side wall PL116 is in direct contact with the outside of the uppermost electrode 122 and is electrically connected.

[0025] In the illustrated embodiment, the insulators 106, 110, and 120 selectively structurally support and electrically insulate other components of the PCM cell 100, filling the spaces between them as needed. Thus, the outside of the bottom electrode 104 is in direct contact with insulator 106 and is laterally surrounded by insulator 106, and the outside of the heater 108 is in direct contact with insulator 110 and is laterally surrounded by insulator 110. Furthermore, the bottom side of the bottom PL 112 is in direct contact with insulator 110 and is axially adjacent to it, and the side wall PL and top wiring 124 are in direct contact with insulator 120 and are laterally and axially adjacent to insulator 120.

[0026] In the illustrated embodiment, the cross-section of the PCM cell 100 (in the plane of paper from Figures 1A to 1C) may be circular, but in other embodiments, it may be rectangular, square, elliptical, or any other suitable shape. Furthermore, while the widths of the PCM material 114, the bottom PL 112, and the top electrode 122 are the same, the width of the heater 108 is substantially reduced (e.g., 3 to 7 times smaller, or about 5 times smaller). Thus, it can be said that the PCM cell 100 has a mushroom structure through which electrical signals (i.e., current) can flow from the bottom electrode 104 to the top electrode 122 via the heater 108, the bottom PL 112, and the PCM material 114.

[0027] In the illustrated embodiment, the lower electrode 104 and the uppermost electrode 122 are made of a highly conductive material, such as a metal or metal compound, for example, titanium nitride (TiN) or tungsten (W). The heater 108 is made of TiN, or a high-resistance metal such as titanium tungsten (TiW), tantalum nitride (TaN), or titanium aluminide (TiAl), and is an electrode with a relatively narrow cross-sectional area that concentrates the current flowing through the PCM cell 100. This allows the heater 108 to generate heat by resistive heating during an electrical pulse, which can be used to selectively change the temperature of the PCM material 114 to a temperature exceeding, for example, the crystallization temperature and melting temperature of the PCM material 114. Furthermore, the heater 108 may be made of multiple different conductive materials that can be arranged in a multilayer structure.

[0028] In the illustrated embodiments, the insulators 106, 110, and 120 are composed of dielectric (electrically insulating) materials such as silicon nitride (SiN), silicon oxide (SiO2), silicon carbide nitride (SiNC), or tetraethyl orthosilicate (TEOS). In some embodiments, all of the insulators 106, 110, and 120 are made of the same material, while in other embodiments, different materials are used for some or all of the insulators 106, 110, and 120. Furthermore, the bottom PL112 and sidewall PL116 are composed of moderately electrically resistive materials such as metals and / or semiconductors (e.g., TaN; tungsten nitride (WN); amorphous carbon (aC); doped aC; tin-doped indium oxide (ITO), aluminum zirconium oxide (AZO), and transparent conductive oxides such as high-resistance metal chalcogenides (e.g., titanium selenide (TiSe)) and other low-conductivity metal nitrides). The materials constituting the bottom PL112 and the side wall PL116 may be the same or different. Furthermore, the materials constituting the bottom PL112 and the side wall PL116 have a higher electrical resistivity than the polycrystalline phase of the PCM material 114, but a lower electrical resistivity than the amorphous phase of the PCM material 114.

[0029] In the illustrated embodiment, the PCM material 114 is essentially composed of a phase-change material such as germanium-antimony-tellurium (GST), gallium-antimony-tellurium (GaST), or silver-iridium-antimony-telluride (AIST) material, but other materials may be used as needed. Other examples of PCM materials may include, but are not limited to, germanium-tellurium compound materials (GeTe), silicon-antimony-tellurium (Si-Sb-Te) alloys, gallium-antimony-tellurium (Ga-Sb-Te) alloys, germanium-bismuth-tellurium (Ge-Bi-Te) alloys, indium-tellurium (In-Te) alloys, arsenic-antimony-tellurium (As-Sb-Te) alloys, silver-indium-antimony-tellurium (Ag-In-Sb-Te) alloys, Ge-In-Sb-Te alloys, Ge-Sb alloys, Sb-Te alloys, Si-Sb alloys, Ge-Te alloys, and combinations thereof. PCM material 114 may be undoped or doped (e.g., doped with one or more of oxygen (O), nitrogen (N), silicon (Si), or Ti). The terms “essentially composed” and “essentially made” as used herein with respect to materials of different layers indicate that, even if other materials are present, they do not substantially alter the fundamental properties of the enumerated materials. For example, PCM material 114, which is essentially composed of GST material, does not contain any other materials that substantially alter the fundamental properties of the GST material.

[0030] In the illustrated embodiment, the PCM cell 100 can be operated as a memory cell by passing a current pulse from the bottom electrode 104 to the top electrode 122 in order to program the PCM cell 100. This can be done at various voltages and / or for various durations to read or write values ​​on the PCM cell 100. For example, a high voltage (e.g., 1 volt (V) to 4 V) can be used for a short period of time for writing, which allows the heater 108 to locally heat the PCM material 114 above its melting point. When the current flow stops, the PCM material 114 cools rapidly, and an amorphous region 126 may be formed in a process called "reset". Region 126 is a dome-shaped region of the PCM material 114 having an amorphous structure, while the rest of the PCM material 114 still has a polycrystalline structure (labeled "126B" in Figure 1B and "126C" in Figure 1C). Generally, this amorphous structure does not have a distinct structure. However, region 126 may contain localized, isolated crystal nuclei (i.e., small crystallized regions of the phase-change material 114). The formation of region 126 may increase the overall electrical resistance of the PCM cell 100 compared to a single polycrystalline structure (as in the PCM cell 100 in Figure 1A). These resistance values ​​of the PCM cell 100 can be read without changing the state of the PCM material 114 (including the state of region 126) or the resistance value of the PCM cell 100, for example, by sending a current pulse at a low voltage (e.g., 0.2V) from the bottom electrode 104 to the top electrode 122.

[0031] Furthermore, by "setting" the PCM cell 100, the PCM material 114 can be rewritten to a single polycrystalline structure. One way to rewrite the PCM material 114 is to use a high-voltage electrical pulse (e.g., 1V to 4V) for a short period (e.g., 10 nanoseconds (ns)), which heats the PCM material 114 above its crystallization point but not to its melting point. Since the crystallization temperature is lower than the melting temperature, when the current flow stops, the PCM material 114 can be annealed and crystals can be formed. Another way to rewrite the PCM material 114 is to use an electrical pulse with a relatively long trailing edge (e.g., 1 microsecond) that is strong enough to heat the PCM material 114 above its melting point (in contrast to a square pulse with a relatively short trailing edge on the order of nanoseconds), after which the PCM material 114 can be slowly cooled and crystals can be formed. In either of these processes, the overall electrical resistance of the PCM cell 100 is reduced compared to when it has amorphous regions 126. Subsequently, this new resistance value can be read using a current at a low voltage (e.g., 0.2V) without changing the state of the PCM material 114 or the resistance value of the PCM cell 100.

[0032] In some embodiments, the melting temperature of the PCM material 114 is approximately 600°C. In some embodiments, the crystallization temperature of the PCM material 114 is approximately 180°C. Furthermore, the process of setting and resetting the PCM cell 100 can be repeated, and in some embodiments, different regions 126 having different resistances can be generated within the PCM material 114 (for example, by having regions 126 of different sizes and / or amounts of crystallization nuclei within the regions 126). This allows the PCM cell 100 to have a variety of different resistances that can be generated by changing the reset parameter. Thus, if the PCM cell 100 is considered to represent an information digit, these digits can be non-binary (as opposed to conventional bits). However, in some embodiments, the PCM cell 100 can be used as a bit by either having or not having a uniform region 126 in the PCM material 114. In such embodiments, the PCM cell 100 may have high resistance (also known as low voltage output or "0") or low resistance (also known as high voltage output or "1").

[0033] The components and configuration of the PCM cell 100 allow for the addition of current paths through the PCM cell 100. Instead of current flowing only from the bottom PL112 to the top electrode 122 via the PCM material 114, current can also flow from the bottom PL112 to the top electrode 122 via the side wall PL116. As previously mentioned, the side wall PL116 has electrical resistivity between the polycrystalline PCM material 114 and the amorphous PCM material 114 (e.g., region 126). Thus, if there is contact with the bottom PL112 (as in region 126B), the current can mainly pass through the PCM material 114, but if region 126 covers the entire bottom PL112 (as in region 126C), the current can mainly pass through at least a portion of the side wall PL116.

[0034] Such capability may be beneficial, considering that the PCM cell 100 may be affected by resistive drift due to the intrinsic drift of the amorphous PCM material (i.e., region 126B), resulting in increased resistance. The PCM cell 100 may also be affected by circuit noise, which can be mitigated by incorporating the bottom PL112 and sidewall PL116. The drift problem is further exacerbated by reducing the PCM cell 100 to a small size of less than approximately 60 nanometers (nm), where the amorphous volume of the PCM material may extend across the entire width of the PCM material 114, forming region 126C. In the absence of sidewall PL116, region 126C would result in a major current flow across the amorphous PCM material, leading to resistive drift within the PCM cell 100. Larger PCM cells may only have a bottom PL (as the amorphous region does not cover the entire width of the PCM material), whereas PCM cell 100 uses sidewall PL 116 to extend the advantages of the bottom PL 112 to the sides of the PCM material 114. These advantages may include reducing resistance drift, lowering the read resistance (resulting in the use of low-current pulses for reading PCM cell 100, which reduces the impact of the read pulse on region 126), reducing noise during reading, increasing control of heater 108, lowering the setting resistance, and increasing the dynamic range of PCM cell 100.

[0035] Figures 1A to 1C illustrate one embodiment of the present disclosure, but alternative embodiments exist. For example, the PCM cell 100 may have a non-mushroom structure, such as a confined cell. Such a structure may not have a separate heater and instead rely on a bottom electrode to prepare the PCM material.

[0036] Figure 2 is a flowchart of method 200 for manufacturing PCM cell 100. Figures 3A to 3I are a series of diagrams of method 200 for manufacturing PCM cell 100. Here, Figures 2 and 3A to 3I will be explained in relation to each other, but each operation of method 200 will be shown by one of Figures 3A to 3I. Furthermore, during this discussion, the features of PCM cell 100 shown in Figures 1A to 1C may be mentioned.

[0037] In the illustrated embodiment, method 200 begins with operation 202, in which an insulating layer 328 is formed on the bottom electrode 104 and insulator 106. In operation 204, vias 330 are formed within the insulating layer 328, for example, by etching to form insulator 110. In operation 206, a heater layer (not shown) is formed on insulator 110, including the vias 330, up to the bottom electrode 104, and chemical mechanical polishing (CMP) is performed to remove excess metal, forming heater 108 adjacent to insulator 110. In operation 208, a bottom PL layer 334 is formed on heater 108 and insulator 110. Furthermore, a PCM layer 336, a TiN layer 338, and a SiN layer 340 are formed on bottom PL 112. In some embodiments, the thickness of the PCM layer 336 is approximately 80 nm, the thickness of the TiN layer 338 is approximately 75 nm, and the thickness of the SiN layer 340 is approximately 220 nm. In operation 210, masking and etching are performed to form the lower PL112, PCM material 114, and uppermost electrode 122.

[0038] In the illustrated embodiment, in operation 212, the sidewall PL layer 342 is formed (for example, using ALD) so as to be in contact with the insulator 110, the bottom PL 112, the PCM material 114, and the top electrode 122. In operation 214, a portion of the sidewall PL layer 342 is selectively removed (for example, using directional RIE or directional sputter etching) to form the sidewall PL 116. In operation 216, the insulator 110, the sidewall PL 116, and the top electrode 122 are sealed by forming an insulating layer 344 on top of them. In operation 218, holes 346 are formed in the insulating layer 344 to form the insulator 120, and the top wiring 124 is formed inside the holes 346 and on the top electrode 122.

[0039] The components, configuration, and operation of the PCM cell 100 and method 200 make it possible to form the side wall PL116 independently of the bottom PL112. This means that some or all of the parameters and properties of the side wall PL116 (e.g., material, thickness, etc.) may be the same as or different from those of the bottom PL112, as needed. Changing such parameters / properties may result in differences between the bottom PL112 and the side wall PL116, for example, their electrical resistivity and / or electrical resistance.

[0040] Figure 4A is a resistance-to-current graph of various possible liner electrical resistivity for PCM cell 100 (shown in Figure 1A). Since resistance is equal to resistivity × length divided by area, the graph is constructed assuming that the dimensions of the side wall PL116 and bottom PL112 remain constant even as their resistance ratio changes. Figure 4A includes curve 448 representing the 1:1 ratio of the resistivity of side wall PL116 (shown in Figure 1A) to the resistivity of bottom PL112 (shown in Figure 1A), curve 450 representing the 2:1 ratio of the resistivity of side wall PL116 to the resistivity of bottom PL112, and curve 452 representing the 4:1 ratio of the resistivity of side wall PL116 to the resistivity of bottom PL112. In some embodiments, the sidewall PL116 may be an ALD film (for conformability, e.g., AlN, TiN, or TaN), and the bottom PL112 may be a PVD film (for example, aC or TaN). The resistivity of the sidewall PL116 and the bottom PL112 can then be adjusted, for example, by doping, to obtain the ratios of curves 448, 450, and 452.

[0041] In the illustrated embodiment, current is shown using a uniform scale, while resistance is shown using a logarithmic scale. Although not shown in the graph, if PCM cell 100 did not contain sidewall PL116 at all, the resistance would be substantially higher than curve 452 at higher currents. Furthermore, if the ratio of the resistivity of sidewall PL116 to the resistivity of the bottom PL112 decreases to less than 1:1, the resistance would be lower than curve 448 at higher currents.

[0042] As shown in the graph, assuming that region 126C reaches the edge of the PCM material 114 (as shown in Figure 1C), increasing the relative resistivity of the sidewall PL116 allows for a higher dynamic range and resolution / contrast between tuned states. However, such a configuration may lead to increased resistive drift, so various configurations (e.g., resistance ratios) can be selected based on their respective advantages and disadvantages.

[0043] Figure 4B is a resistance-to-current graph for various possible liner thickness ratios of PCM cell 100 (shown in Figure 1A). Since resistance is equal to resistivity × length divided by area, this graph is constructed assuming that the resistivity, length, and diameter of the sidewall PL116 and bottom PL112 remain constant even as their thickness ratios change. Figure 4B includes curve 454 representing the 1:1 ratio of the thickness of sidewall PL116 (shown in Figure 1A) to the thickness of bottom PL112 (shown in Figure 1A), curve 456 representing the 1:2 ratio of the thickness of sidewall PL116 to the thickness of bottom PL112, and curve 458 representing the 1:4 ratio of the thickness of sidewall PL116 to the thickness of bottom PL112. In some embodiments, the thickness of sidewall PL116 may be between 1 nm and 10 nm, and the thickness of bottom PL112 may be between 1 nm and 5 nm. For example, curve 454 can be obtained using a sidewall PL116 with a thickness of 4 nm and a bottom PL112 with a thickness of 4 nm, curve 456 can be obtained using a sidewall PL116 with a thickness of 2 nm and a bottom PL112 with a thickness of 4 nm, and curve 458 can be obtained using a sidewall PL116 with a thickness of 1 nm and a bottom PL112 with a thickness of 4 nm.

[0044] In the illustrated embodiment, current is shown using a uniform scale, while resistance is shown using a logarithmic scale. Although not shown in the graph, if PCM cell 100 did not include the side wall PL116 at all, the resistance would be substantially higher than curve 458 at higher currents. Furthermore, if the ratio of the thickness of the side wall PL116 to the thickness of the bottom PL112 increases beyond 1:1, the resistance would be lower than curve 454 at higher currents.

[0045] As shown in the graph, assuming that region 126C reaches the edge of the PCM material 114 (as shown in Figure 1C), increasing the relative thickness of the sidewall PL116 allows for a higher dynamic range and resolution / contrast between tuned states. However, such a configuration may lead to increased resistive drift, so various configurations (e.g., thickness ratios) can be selected based on their respective advantages and disadvantages. Furthermore, by varying both the thickness and electrical resistivity, appropriate electrical resistance can be obtained for the sidewall PL116 and bottom PL112 of a given structure.

[0046] The descriptions of various embodiments of the present invention are presented for illustrative purposes only and are not intended to be exhaustive or limit to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the embodiments described. The terms used herein have been selected to best describe the principles of the embodiments, their practical applications, or any technical improvements beyond the technology available on the market, or to enable other those skilled in the art to understand the embodiments disclosed herein. (Other possible items) (Item 1) A phase-change memory (PCM) cell having a mushroom structure, wherein the PCM cell is First electrode; A heater electrically connected to the first electrode; A first protruding liner electrically connected to the heater; A PCM material electrically connected to the first protruding liner; A second electrode electrically connected to the PCM material; and A second protruding liner electrically connected to the first protruding liner and the second electrode. A PCM cell equipped with this feature. (Item 2) The heater has a first width; The PCM material has a second width; The PCM cell described in item 1, wherein the second width is greater than or equal to three times the first width. (Item 3) The second width is approximately five times larger than the first width, and is a PCM cell as described in item 2. (Item 4) The first protruding liner is made of a first material; The second protruding liner is made of the second material; and The second material is a PCM cell as described in any one of items 1 to 3, which is different from the first material. (Item 5) The first material has a higher electrical resistivity than the PCM material in the polycrystalline phase and a lower electrical resistivity than the PCM material in the amorphous phase; and The PCM cell according to item 4, wherein the second material has a higher electrical resistivity than the PCM material in the polycrystalline phase and a lower electrical resistivity than the PCM material in the amorphous phase. (Item 6) The first protruding liner extends along the edge of the PCM material; The second protruding liner is a PCM cell according to any one of items 1 to 5, extending along the side surface of the PCM material adjacent to the end. (Item 7) The first protruding liner covers the end of the PCM material; The PCM cell according to item 6, wherein the second protruding liner surrounds the side surface of the PCM material along its entire longitudinal length. (Item 8) First electrode; A first protruding liner electrically connected to the first electrode, the first protruding liner having a first material; A PCM material electrically connected to the first protruding liner; A second electrode electrically connected to the PCM material; and A second protruding liner electrically connected to the first protruding liner and the second electrode, the second protruding liner having a second material; Here, the second material is different from the first material. A phase-change memory (PCM) cell equipped with [a specific feature]. (Item 9) The PCM cell according to item 8, further comprising a heater electrically connected to the first electrode and the first protruding liner. (Item 10) The heater has a first width; The PCM material has a second width; The PCM cell described in item 9, wherein the second width is greater than or equal to three times the first width. (Item 11) The first protruding liner covers the end of the PCM material; and The PCM cell according to any one of items 8 to 10, wherein the second protruding liner surrounds the side of the PCM material adjacent to the end over its entire longitudinal length. (Item 12) The first material has a higher electrical resistivity than the PCM material in the polycrystalline phase and a lower electrical resistivity than the PCM material in the amorphous phase; and The PCM cell according to any one of items 8 to 11, wherein the second material has a higher electrical resistivity than the PCM material in the polycrystalline phase and a lower electrical resistivity than the PCM material in the amorphous phase. (Item 13) The first material has a first electrical resistivity; The second material has a second electrical resistivity; A PCM cell according to any one of items 8 to 12, wherein the second electrical resistivity is greater than or equal to twice the first electrical resistivity. (Item 14) The first protruding liner has a first thickness; The second protruding liner has a second thickness; A PCM cell as described in any one of items 8 to 13, wherein the second thickness is less than or equal to half the first thickness. (Item 15) A method for manufacturing a phase-change memory (PCM) cell, the method comprising the step of forming a first electrode; A step of forming a first protruding liner electrically connected to the first electrode; The step of forming the PCM material on the first protruding liner; The step of forming a second electrode on the PCM material; and A method comprising the step of forming a second protruding liner so as to be in contact with the first protruding liner, the PCM material, and the second electrode. (Item 16) The method according to item 15, further comprising the step of forming a heater on the first electrode, wherein the first protruding liner is formed on the heater. (Item 17) The heater has a first width; The method according to item 16, wherein the PCM material has a second width; the second width is greater than or equal to three times the first width. (Item 18) The first protruding liner is made of a first material; The second protruding liner is made of the second material; and The method described in any one of items 15 to 17, wherein the second material is different from the first material. (Item 19) The method according to item 18, wherein the second material has a higher electrical resistivity than the PCM material in the polycrystalline phase and a lower electrical resistivity than the PCM material in the amorphous phase. (Item 20) The method according to item 19, wherein the first material has a higher electrical resistivity than the PCM material in the polycrystalline phase and a lower electrical resistivity than the PCM material in the amorphous phase.

Claims

1. A phase-change memory (PCM) cell having a mushroom structure, wherein the PCM cell is First electrode; A heater electrically connected to the first electrode; A first protruding liner electrically connected to the heater; A PCM material electrically connected to the first protruding liner; A second electrode electrically connected to the PCM material; and A second protruding liner electrically connected to the first protruding liner and the second electrode. Equipped with, The first protruding liner is made of the first material, The second protruding liner is made of the second material, The second material has a higher electrical resistivity than the PCM material in the polycrystalline phase and a lower electrical resistivity than the PCM material in the amorphous phase. The first material has a first electrical resistivity, The second material has a second electrical resistivity, A PCM cell in which the second electrical resistivity is greater than or equal to twice the first electrical resistivity.

2. The heater has a first width; The PCM material has a second width; The PCM cell according to claim 1, wherein the second width is greater than or equal to three times the first width.

3. The PCM cell according to claim 2, wherein the second width is approximately five times larger than the first width.

4. The PCM cell according to claim 1, wherein the second material is different from the first material.

5. The PCM cell according to claim 4, wherein the first material has a higher electrical resistivity than the PCM material in the polycrystalline phase and a lower electrical resistivity than the PCM material in the amorphous phase.

6. The first protruding liner extends along the edge of the PCM material; The PCM cell according to claim 1, wherein the second protruding liner extends along the side surface of the PCM material adjacent to the end.

7. The first protruding liner covers the end of the PCM material; The PCM cell according to claim 6, wherein the second protruding liner surrounds the side surface of the PCM material along its entire longitudinal length.

8. First electrode; A first protruding liner electrically connected to the first electrode, the first protruding liner having a first material; A PCM material electrically connected to the first protruding liner; A second electrode electrically connected to the PCM material; and A second protruding liner electrically connected to the first protruding liner and the second electrode, the second protruding liner having a second material; Here, the second material is different from the first material. Equipped with, The second material has a higher electrical resistivity than the PCM material in the polycrystalline phase and a lower electrical resistivity than the PCM material in the amorphous phase. The first material has a first electrical resistivity, The second material has a second electrical resistivity, A phase-change memory (PCM) cell in which the second electrical resistivity is greater than or equal to twice the first electrical resistivity.

9. The PCM cell according to claim 8, further comprising a heater electrically connected to the first electrode and the first protruding liner.

10. The heater has a first width; The PCM material has a second width; The PCM cell according to claim 9, wherein the second width is greater than or equal to three times the first width.

11. The first protruding liner covers the end of the PCM material; and The PCM cell according to claim 8, wherein the second protruding liner surrounds the side surface of the PCM material adjacent to the end over its entire longitudinal length.

12. The PCM cell according to claim 8, wherein the first material has a higher electrical resistivity than the PCM material in the polycrystalline phase and a lower electrical resistivity than the PCM material in the amorphous phase.

13. The first protruding liner has a first thickness; The second protruding liner has a second thickness; The PCM cell according to claim 8, wherein the second thickness is less than or equal to half of the first thickness.

14. A method for manufacturing a phase-change memory (PCM) cell, the method comprising the step of forming a first electrode; A step of forming a first protruding liner electrically connected to the first electrode; Steps include forming the PCM material on the first protruding liner; The step of forming a second electrode on the PCM material; and The process includes the step of forming a second protruding liner so as to be in contact with the first protruding liner, the PCM material, and the second electrode, The first protruding liner is made of the first material, The second protruding liner is made of the second material, The second material has a higher electrical resistivity than the PCM material in the polycrystalline phase and a lower electrical resistivity than the PCM material in the amorphous phase. The first material has a first electrical resistivity, The second material has a second electrical resistivity, A method wherein the second electrical resistivity is greater than or equal to twice the first electrical resistivity.

15. The method according to claim 14, further comprising the step of forming a heater on the first electrode, wherein the first protruding liner is formed on the heater.

16. The heater has a first width; The method according to claim 15, wherein the PCM material has a second width; the second width is greater than or equal to three times the first width.

17. The method according to claim 14, wherein the second material is different from the first material.

18. The method according to claim 14, wherein the first material has a higher electrical resistivity than the PCM material in the polycrystalline phase and a lower electrical resistivity than the PCM material in the amorphous phase.

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