Integrated Diode-Memory Device

Abstract

The nonvolatile memory structure can include a phase change memory comprising a phase change material. The nonvolatile memory structure can include a Schottky diode in series with the phase change memory, with the Schottky barrier of the Schottky diode being the surface of the phase change memory. This can be achieved by properly selecting materials for the contacts of the phase change memory. This can form an integrated diode-memory structure that can control the direction of current flow without penalizing the footprint of the structure.

Description

Technical Field

[0001] The present invention relates to non-volatile memories, and more particularly to memristive devices for neuromorphic computing.

Background Art

[0002] “Machine learning” is used to broadly describe the main functions of electronic systems that learn from data. In accelerated machine learning and cognitive science, an artificial neural network (ANN) is a type of statistical learning model inspired by the biological neural networks of animals, particularly the brain. An ANN is a system and function that depends on a large number of inputs and can be used for the purpose of estimating or approximating systems and functions that are not generally known. ANN architectures, neuromorphic microchips, and ultra-high density non-volatile memories can be formed by a high-density, low-cost circuit architecture known as a cross-bar array. A basic cross-bar array configuration includes a set of conductive row wires and a set of conductive column wires formed to intersect the set of conductive row wires. The intersections between these two sets of wires are separated by so-called crosspoint devices that can be formed from thin film materials. Crosspoint devices can be implemented as so-called memristive devices. The characteristics of memristive devices include being non-volatile, being able to store variable resistance values, and being able to tune the resistance up or down using current or voltage pulses.

Summary of the Invention

[0003] The non-volatile memory structure can include phase change memory comprising a phase change material. This non-volatile memory structure can include a Schottky diode in series with the phase change memory, and the Schottky barrier of this Schottky diode is the surface of the phase change memory. This can form an integrated diode-memory structure that can control the direction of current without disadvantaging the footprint of the structure.

[0004] The non-volatile memory structure of paragraph

[0003] can have the Schottky barrier as the interface between the phase change material and the contact. This can form an integrated diode-memory structure that can control the direction of current without disadvantaging the footprint of the structure.

[0005] The non-volatile memory structure of paragraph

[0004] can have a contact having a material with a work function 0.3 to 1 eV lower than the work function of the phase change material. This can form a p-type integrated diode-memory structure that can control the direction of current without disadvantaging the footprint of the structure.

[0006] The non-volatile memory structure of paragraph

[0004] can have a contact having a material selected from titanium, molybdenum, aluminum, tantalum, tungsten, manganese, zirconium, and hafnium. This can form a p-type integrated diode-memory structure that can control the direction of current without disadvantaging the footprint of the structure.

[0007] The non-volatile memory structure of paragraph

[0004] can have a contact having a material with a work function 0.3 to 1 eV higher than the work function of the phase change material. This can form an n-type integrated diode-memory structure that can control the direction of current without disadvantaging the footprint of the structure.

[0008] The non-volatile memory structure of paragraph

[0004] can have a contact having a material selected from molybdenum, titanium nitride, tungsten, gold, cobalt, copper, nickel, palladium, and iridium. This can form an n-type integrated diode-memory structure, which can control the direction of current without disadvantaging the footprint of the structure.

[0009] The non-volatile memory structure can include a phase change material placed between a first contact and a second contact, where the first contact and the second contact are of different materials. This can form an integrated diode-memory structure, which can control the direction of current without disadvantaging the footprint of the structure.

[0010] The non-volatile memory structure of paragraph

[0009] can have a Schottky barrier as an interface between the phase change material and the contact. This can form an integrated diode-memory structure, which can control the direction of current without disadvantaging the footprint of the structure.

[0011] The non-volatile memory structure of paragraph

[0010] can have a contact having a material with a work function 0.3 to 1 eV lower than that of the phase change material. This can form a p-type integrated diode-memory structure, which can control the direction of current without disadvantaging the footprint of the structure.

[0012] The non-volatile memory structure of paragraph

[0010] can have a contact having a material selected from titanium, molybdenum, aluminum, tantalum, tungsten, manganese, zirconium, and hafnium. This can form a p-type integrated diode-memory structure, which can control the direction of current without disadvantaging the footprint of the structure.

[0013] The non-volatile memory structure of paragraph

[0010] can have a contact having a material with a work function 0.3 to 1 eV higher than the work function of the phase change material. This can form an n-type integrated diode-memory structure, which can control the direction of current without disadvantaging the footprint of the structure.

[0014] The non-volatile memory structure of paragraph

[0010] can have a contact having a material selected from molybdenum, titanium nitride, tungsten, gold, cobalt, copper, nickel, palladium, and iridium. This can form an n-type integrated diode-memory structure, which can control the direction of current without disadvantaging the footprint of the structure.

[0015] The non-volatile memory structure can include a plurality of bit lines and a plurality of word lines. A PCM memory structure is placed between the plurality of bit lines and the plurality of word lines. The PCM memory structure can include a phase change material placed between a first contact and a second contact. The first contact and the second contact are of different materials. This can form an integrated diode-memory structure, which can control the direction of current without disadvantaging the footprint of the structure.

[0016] The non-volatile memory structure of paragraph

[0015] can have a Schottky barrier as the interface between the phase change material and the contact. This can form an integrated diode-memory structure, which can control the direction of current without disadvantaging the footprint of the structure.

[0017] The non-volatile memory structure of paragraph

[0016] can have a contact having a material with a work function that is 0.3 to 1 eV lower than the work function of the phase change material. This can form a p-type integrated diode-memory structure that can control the direction of current without disadvantaging the footprint of the structure.

[0018] The non-volatile memory structure of paragraph

[0016] can have a contact having a material selected from titanium, molybdenum, aluminum, tantalum, tungsten, manganese, zirconium, and hafnium. This can form a p-type integrated diode-memory structure that can control the direction of current without disadvantaging the footprint of the structure.

[0019] The non-volatile memory structure of paragraph

[0016] can have a contact having a material with a work function that is 0.3 to 1 eV higher than the work function of the phase change material. This can form an n-type integrated diode-memory structure that can control the direction of current without disadvantaging the footprint of the structure.

[0020] The non-volatile memory structure of paragraph

[0016] can have a contact having a material selected from molybdenum, titanium nitride, tungsten, gold, cobalt, copper, nickel, palladium, and iridium. This can form an n-type integrated diode-memory structure that can control the direction of current without disadvantaging the footprint of the structure.

[0021] The non-volatile memory structure can include a plurality of bit lines and a plurality of word lines. A PCM memory structure is disposed between the plurality of bit lines and the plurality of word lines. The PCM memory structure can include a phase change material and a Schottky diode in series with the phase change memory. The Schottky barrier of the Schottky diode is the surface of the phase change memory. The Schottky barrier is the interface between the phase change material and the contact. This can form an integrated diode-memory structure that can control the direction of current without disadvantaging the footprint of the structure.

[0022] The non-volatile memory structure of paragraph

[0021] can have the Schottky barrier as the interface between the phase change material and the contact. This can form an integrated diode-memory structure that can control the direction of current without disadvantaging the footprint of the structure.

[0023] The non-volatile memory structure of paragraph

[0021] can have a contact having a material with a work function 0.3 to 1 eV lower than the work function of the phase change material. This can form a p-type integrated diode-memory structure that can control the direction of current without disadvantaging the footprint of the structure.

[0024] The non-volatile memory structure of paragraph

[0021] can have a contact having a material selected from titanium, molybdenum, aluminum, tantalum, tungsten, manganese, zirconium, and hafnium. This can form a p-type integrated diode-memory structure that can control the direction of current without disadvantaging the footprint of the structure.

[0025] The non-volatile memory structure of paragraph

[0021] can have a contact having a material with a work function 0.3 to 1 eV higher than the work function of the phase change material. This can form an n-type integrated diode-memory structure that can control the direction of current without disadvantaging the footprint of the structure.

[0026] The non-volatile memory structure of paragraph

[0021] can have a contact having a material selected from molybdenum, titanium nitride, tungsten, gold, cobalt, copper, nickel, palladium, and iridium. This can form an n-type integrated diode-memory structure that can control the direction of current without disadvantaging the footprint of the structure.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0028] The elements of the figures are not necessarily drawn to a fixed scale, and it is not intended that the elements of the figures represent specific parameters of the present invention. For clarity and ease of illustration, the dimensions of the elements may be exaggerated. Reference should be made to the following detailed description for exact dimensions. The drawings are intended to show only typical embodiments of the present invention, and thus the drawings should not be considered as limiting the scope of the present invention. The same reference numerals in the drawings represent the same elements.

[0029] Next, exemplary embodiments will be described in more detail with reference to the accompanying drawings in which those exemplary embodiments are shown. However, the present disclosure can be implemented in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. These exemplary embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art. In this description, well-known features and techniques may sometimes be omitted to prevent the presented embodiments from being unnecessarily obscured.

[0030] For the purposes of the following description, terms such as "upper", "lower", "right", "left", "vertical", "horizontal", "top", "bottom", and derivatives of these terms relate to the disclosed structures and methods when arranged in the drawings. Terms such as "above", "overlying", "atop", "on top", "positioned on", or "positioned atop" mean that a first element, such as a first structure, is over a second element, such as a second structure, and there may be an intervening element, such as an interface structure, 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 without an intermediate conductive layer, insulating layer, or semiconductor layer existing at the interface of the two elements.

[0031] To avoid obscuring the presentation of embodiments of the present invention, in the following detailed description, some process steps or operations known in the art may be combined together for purposes of presentation and illustration, and in some instances, some process steps or operations known in the art may not be described in detail. In other instances, some process steps or operations known in the art may not be described at all. Rather, the following description should be understood to focus on the differential features or elements of the various embodiments of the present invention.

[0032] Analog computing uses memory devices such as memristors that store information as the conductance range of a memory device. Such memory devices are often arranged as cross-point arrays with a number of word lines and bit lines arranged in a grid pattern, and a single memory device can be read simultaneously as current flows through one word line and one bit line. For example, FIG. 1 shows a simplified cross-point array having a first word line 10A, a second word line 10B, a first memory device 20A, a second memory device 20B, a third memory device 20C, a fourth memory device 20D, a first bit line 30A, and a second bit line 30B. In the example shown in FIG. 1, a desired read path P1 for the fourth memory device 20D is shown. However, during the read state of the fourth memory device 20D, there may be a sneak path P2 through the first memory device 20A, the second memory device 20B, and the third memory device 20C. The combination of the read path P1 and the sneak path P2 is shown in FIG. 2, which shows a first conductance G A of the first memory device 20A, a second conductance G B of the second memory device 20B, a third conductance G C of the third memory device 20C, and a fourth conductance G D of the fourth memory device 20D. Thus, in the exemplary layout shown in FIG. 1, instead of reading the memory state of the fourth memory device 20D as the fourth conductance G D , the fourth conductance G D represented by the formula

Number

[0033]

[0034] ​FIG. 3 shows a cross-sectional view of an integrated diode phase change memory structure according to an exemplary embodiment. The material stack includes a bottom electrode 110, a top electrode 120, a phase change material 130, and an interlayer dielectric (ILD) 140.

[0035] The ILD 140 can be used to isolate integrated diode-memory cells. Suitable ILD materials include, but are not limited to, oxide low-k materials such as silicon oxide (SiOx), SiOCH or oxide ultralow-k interlayer dielectric (ULK-ILD) materials, or combinations thereof, for example, oxide low-k materials having a dielectric constant k of less than 2.7. In comparison, silicon dioxide (SiO2) has a dielectric constant k value of 3.9. Suitable ultralow-k dielectric materials include, but are not limited to, porous organosilicate glass (pSiCOH).

[0036] According to an exemplary embodiment, a phase change material 130 can be placed above a bottom electrode 110. The phase change material 130 can include a material that can be programmed into an amorphous (high resistance) state or a crystalline (low resistance) state by heating, such as, for example, a chalcogenide-based material. Exemplary chalcogenide-based materials include, but are not limited to, Ge2Sb2Te5 (GST), SbTe, and In2Se3. The phase change material can include a Ge—Sb—Te (germanium-antimony-tellurium or “GST,” such as Ge2Sb2Te5) alloy. Alternatively, other suitable materials for the phase change material can include Si—Sb—Te (silicon-antimony-tellurium) alloys, Ga—Sb—Te (gallium-antimony-tellurium) alloys, Ge—Bi—Te (germanium-bismuth-tellurium) alloys, In—Se (indium-selenium) alloys, As—Sb—Te (arsenic-antimony-tellurium) alloys, Ag—In—Sb—Te (silver-indium-antimony-tellurium) alloys, Ge—In—Sb—Te alloys, Ge—Sb alloys, Sb—Te alloys, Si—Sb alloys, and combinations thereof. In some embodiments, the phase change material can further include nitrogen, carbon, or oxygen, or combinations thereof. In some embodiments, a dielectric material including, but not limited to, aluminum oxide (Al2O3), silicon oxide (SiO2), tantalum oxide (Ta2O5), hafnium oxide (HfO2), zirconium oxide (ZrO2), cerium oxide (CeO2), silicon nitride (SiN), silicon oxynitride (SiON), etc., can be doped into the phase change material.

[0037] The bottom electrode 110 and the top electrode 120 are selected to form a Schottky barrier together with the surface of the phase change material 130. To achieve this, one of the bottom electrode 110 and the top electrode 120 can include a low-resistance metal, and the other is selected to be formed of a contact diode material. The low-resistance metal can be Al, W, Cu, TiN, TaN, or other suitable materials. The contact diode material can be selected based on whether the PCM device is an n-type device or a p-type device. For a p-type device, the diode contact material can include a material having a work function lower than the barrier height of the phase change material. In some embodiments, the diode contact material can be selected to have a work function 0.3 to 1 eV lower than that of the phase change material. For the above-described PCM materials, such a diode contact material can be, for example, titanium, molybdenum, aluminum, tantalum, tungsten, manganese, zirconium, and hafnium. For an n-type device, the diode contact material can include a material having a work function higher than the barrier height of the phase change material. In some embodiments, the diode contact material can be selected to have a work function 0.3 to 1 eV higher than that of the phase change material. For the above-described PCM materials, such a material can be, for example, molybdenum, titanium nitride, tungsten, gold, cobalt, copper, nickel, palladium, and iridium.

[0038] As described above, the bottom electrode 110 and the top electrode 120 are different contact materials in order to enable a Schottky barrier formed at the interface between the electrode made of the diode contact material and the phase change material 130 to function as a Schottky diode. Thus, in one example, the bottom electrode 110 is a low-resistance metal and the top electrode 120 is a diode contact material. Thus, in another example, the top electrode 120 is a low-resistance metal and the bottom electrode 110 is a diode contact material. The bottom electrode 110 and the top electrode 120 may be separate layers and materials from the word lines and bit lines attached to these electrodes, or may not be clearly distinguishable from the word lines and bit lines to which these electrodes are attached (for example, the word lines or bit lines may be a diode contact material or a low-resistance metal or both). It should be noted that.

[0039] FIG. 4 shows a cross-sectional view of an integrated diode-mushroom cell phase change memory structure according to an exemplary embodiment. This material stack includes a bottom electrode 210, a top electrode 220, a phase change material 230, a PCM heater 231, a PCM dielectric 232, and an interlayer dielectric (ILD) 240.

[0040] The ILD 240 can be used to isolate integrated diode memory cells. Suitable ILD materials include, but are not limited to, oxide low-k materials such as silicon oxide (SiOx), SiOCH or oxide ultra-low k interlayer dielectric (ULK-ILD) materials, or combinations thereof, for example, oxide low-k materials having a dielectric constant k of less than 2.7. In comparison, silicon dioxide (SiO2) has a dielectric constant k value of 3.9. Suitable ultra-low k dielectric materials include, but are not limited to, porous organosilicate glass (pSiCOH).

[0041] The PCM dielectric 232 can be selected to withstand the heating provided by the PCM heater 231 to change the state of the phase change material 230. The PCM dielectric can include, but is not limited to, oxide low-k materials such as silicon oxide (SiOx).

[0042] According to an exemplary embodiment, the phase change material 230 can be placed above the PCM heater 231. The phase change material 230 can include materials that can be programmed into an amorphous (high resistance) state or a crystalline (low resistance) state by heating, such as, for example, chalcogenide-based materials. Exemplary chalcogenide-based materials include, but are not limited to, Ge2Sb2Te5 (GST), SbTe, and In2Se3. The phase change material can include a Ge-Sb-Te (germanium-antimony-tellurium or "GST", such as Ge2Sb2Te5) alloy. Alternatively, other suitable materials for the phase change material can include Si-Sb-Te (silicon-antimony-tellurium) alloys, Ga-Sb-Te (gallium-antimony-tellurium) alloys, Ge-Bi-Te (germanium-bismuth-tellurium) alloys, In-Se (indium-tellurium) alloys, As-Sb-Te (arsenic-antimony-tellurium) alloys, Ag-In-Sb-Te (silver-indium-antimony-tellurium) alloys, Ge-In-Sb-Te alloys, Ge-Sb alloys, Sb-Te alloys, Si-Sb alloys, and combinations thereof. In some embodiments, the phase change material can further include nitrogen, carbon, or oxygen, or combinations thereof. In some embodiments, dielectric materials including, but not limited to, aluminum oxide (Al2O3), silicon oxide (SiO2), tantalum oxide (Ta2O5), hafnium oxide (HfO2), zirconium oxide (ZrO2), cerium oxide (CeO2), silicon nitride (SiN), silicon oxynitride (SiON), etc. can be doped into the phase change material.

[0043] The PCM heater 231 and the top electrode 220 are selected to form a Schottky barrier together with the surface of the phase change material 230. To achieve this, the PCM heater 231 and the top electrode 220 are selected such that one can include a low-resistance metal and the other is formed of a contact diode material. The low-resistance metal can be Al, W, Cu, TiN, TaN, or other suitable materials. The contact diode material can be selected based on whether the PCM device is an n-type device or a p-type device. For a p-type device, the diode contact material can include a material having a work function lower than the barrier height of the phase change material, and in some embodiments, the diode contact material can be selected to have a work function 0.3 to 1 eV lower than that of the phase change material. For the above-described PCM materials, such a diode contact material can be, for example, titanium, molybdenum, aluminum, tantalum, tungsten, manganese, zirconium, and hafnium. For an n-type device, the diode contact material can include a material having a work function higher than the barrier height of the phase change material, and in some embodiments, the diode contact material can be selected to have a work function 0.3 to 1 eV higher than that of the phase change material. For the above-described PCM materials, such a material can be, for example, molybdenum, titanium nitride, tungsten, gold, cobalt, copper, nickel, palladium, and iridium.

[0044] As described above, the PCM heater 231 and the top electrode 220 are different contact materials in order to enable the Schottky barrier formed at the interface between the electrode made of the diode contact material and the phase change material 230 to function as a Schottky diode. Thus, in one example, the PCM heater 231 is a low-resistance metal and the top electrode 220 is a diode contact material. Thus, in another example, the top electrode 220 is a low-resistance metal and the PCM heater 231 is a diode contact material.

[0045] The bottom electrode 210 can be selected as a low-resistance metal such as, for example, Al, W, Cu, TiN, TaN, or other suitable materials. The bottom electrode 210 and the top electrode 220 may be separate layers and materials from the word lines and bit lines attached to these electrodes, or they may not be clearly distinguishable from the word lines and bit lines to which these electrodes are attached (for example, the word lines or bit lines may be diode contact materials or low-resistance metals or both). It should be noted that this is the case.

[0046] FIG. 5 shows a cross-sectional view of an integrated diode-mushroom cell phase change memory structure according to an exemplary embodiment. This material stack includes a bottom electrode 310, a top electrode 320, a phase change material 330, a liner 331, a PCM dielectric 332, and an interlayer dielectric (ILD) 340.

[0047] The ILD 340 can be used to isolate the integrated diode memory cells. Suitable ILD materials include, but are not limited to, oxide low-k materials such as silicon oxide (SiOx), SiOCH, or oxide ultra-low-k interlayer dielectric (ULK-ILD) materials, or combinations thereof, for example, oxide low-k materials having a dielectric constant k of less than 3.7. In comparison, silicon dioxide (SiO2) has a dielectric constant k value of 3.9. Suitable ultra-low-k dielectric materials include, but are not limited to, porous organosilicate glass (pSiCOH).

[0048] The PCM dielectric 332 can be selected to withstand the heating provided by the PCM heater (liner) 331 to change the state of the phase change material 330. The PCM dielectric can include, but is not limited to, oxide low-k materials such as silicon oxide (SiOx).

[0049] According to an exemplary embodiment, the phase change material 330 can be placed above the PCM heater (liner) 331. The phase change material 330 can include materials that can be programmed into an amorphous (high resistance) state or a crystalline (low resistance) state by heating, such as, for example, chalcogenide-based materials. Exemplary chalcogenide-based materials include, but are not limited to, Ge2Sb2Te5 (GST), SbTe, and In2Se3. The phase change material can include a Ge-Sb-Te (germanium-antimony-tellurium or "GST", such as Ge2Sb2Te5) alloy. Alternatively, other suitable materials for the phase change material can include Si-Sb-Te (silicon-antimony-tellurium) alloys, Ga-Sb-Te (gallium-antimony-tellurium) alloys, Ge-Bi-Te (germanium-bismuth-tellurium) alloys, In-Se (indium-tellurium) alloys, As-Sb-Te (arsenic-antimony-tellurium) alloys, Ag-In-Sb-Te (silver-indium-antimony-tellurium) alloys, Ge-In-Sb-Te alloys, Ge-Sb alloys, Sb-Te alloys, Si-Sb alloys, and combinations thereof. In some embodiments, the phase change material can further include nitrogen, carbon, or oxygen, or combinations thereof. In some embodiments, a dielectric material, including, but not limited to, aluminum oxide (Al2O3), silicon oxide (SiO2), tantalum oxide (Ta2O5), hafnium oxide (HfO2), zirconium oxide (ZrO2), cerium oxide (CeO2), silicon nitride (SiN), silicon oxynitride (SiON), etc., can be doped into the phase change material.

[0050] The top electrode 320 and the liner 331 or the bottom electrode 310 are selected to form a Schottky barrier together with the surface of the phase change material 330. To achieve this, the top electrode 320 and the liner 331 or the bottom electrode 310 are selected such that one can include a low-resistance metal and the other is formed of a contact diode material. The low-resistance metal can be Al, W, Cu, TiN, TaN, or other suitable materials. The contact diode material can be selected based on whether the PCM device is an n-type device or a p-type device. For a p-type device, the diode contact material can include a material having a work function lower than the barrier height of the phase change material, and in some embodiments, the diode contact material can be selected to have a work function 0.3 to 1 eV lower than that of the phase change material. For the above-described PCM materials, such a diode contact material can be, for example, titanium, molybdenum, aluminum, tantalum, tungsten, manganese, zirconium, and hafnium. For an n-type device, the diode contact material can include a material having a work function higher than the barrier height of the phase change material, and in some embodiments, the diode contact material can be selected to have a work function 0.3 to 1 eV higher than that of the phase change material. For the above-described PCM materials, such a material can be, for example, molybdenum, titanium nitride, tungsten, gold, cobalt, copper, nickel, palladium, and iridium.

[0051] As described above, the top electrode 320 and the liner 331 or the bottom electrode 310 are different contact materials in order to enable the Schottky barrier formed at the interface between the electrode made of the diode contact material and the phase change material 330 to function as a Schottky diode. Thus, in one example, the liner 331 is a low-resistance metal and the top electrode 320 is a diode contact material. Thus, in another example, the top electrode 320 is a low-resistance metal and the liner 331 is a diode contact material.

[0052] The bottom electrode 310 can be selected as a low-resistance metal such as, for example, Al, W, Cu, TiN, TaN, or other suitable materials. The bottom electrode 310 and the top electrode 320 may be separate layers and materials from the word lines and bit lines attached to these electrodes, or may not be clearly distinguishable from the word lines and bit lines to which these electrodes are attached (for example, the word lines or bit lines may be diode contact materials or low-resistance metals or both). It should be noted that this is the case.

[0053] FIG. 6 shows a cross-sectional view of an integrated diode phase change memory structure according to an exemplary embodiment. This material stack includes a first electrode 410, a second electrode 420, a phase change material 430, and an interlayer dielectric (ILD) 440.

[0054] The ILD 440 can be used to isolate integrated diode memory cells. Suitable ILD materials include, but are not limited to, oxide low-k materials such as silicon oxide (SiOx), SiOCH, or oxide ultra-low-k interlayer dielectric (ULK-ILD) materials, or combinations thereof, for example, oxide low-k materials having a dielectric constant k of less than 2.7. In comparison, silicon dioxide (SiO2) has a dielectric constant k value of 3.9. Suitable ultra-low-k dielectric materials include, but are not limited to, porous organosilicate glass (pSiCOH).

[0055] According to an exemplary embodiment, a phase change material 430 can be placed above the first electrode 410. The phase change material 430 can include a material that can be programmed into an amorphous (high resistance) state or a crystalline (low resistance) state by heating, such as, for example, a chalcogenide-based material. Exemplary chalcogenide-based materials include, but are not limited to, Ge2Sb2Te5 (GST), SbTe, and In2Se3. The phase change material can include a Ge-Sb-Te (germanium-antimony-tellurium or "GST", such as Ge2Sb2Te5) alloy. Alternatively, other suitable materials for the phase change material can include Si-Sb-Te (silicon-antimony-tellurium) alloy, Ga-Sb-Te (gallium-antimony-tellurium) alloy, Ge-Bi-Te (germanium-bismuth-tellurium) alloy, In-Se (indium-tellurium) alloy, As-Sb-Te (arsenic-antimony-tellurium) alloy, Ag-In-Sb-Te (silver-indium-antimony-tellurium) alloy, Ge-In-Sb-Te alloy, Ge-Sb alloy, Sb-Te alloy, Si-Sb alloy, and combinations thereof. In some embodiments, the phase change material can further include nitrogen, carbon, or oxygen, or combinations thereof. In some embodiments, a dielectric material including, but not limited to, aluminum oxide (Al2O3), silicon oxide (SiO2), tantalum oxide (Ta2O5), hafnium oxide (HfO2), zirconium oxide (ZrO2), cerium oxide (CeO2), silicon nitride (SiN), silicon oxynitride (SiON), etc., can be doped into the phase change material.

[0056] The first electrode 410 and the second electrode 420 are selected to form a Schottky barrier together with the surface of the phase change material 430. To achieve this, the first electrode 410 and the second electrode 420 are selected such that one can include a low-resistance metal and the other is formed of a contact diode material. The low-resistance metal can be Al, W, Cu, TiN, TaN, or other suitable materials. The contact diode material can be selected based on whether the PCM device is an n-type device or a p-type device. For a p-type device, the diode contact material can include a material having a work function lower than the barrier height of the phase change material. In some embodiments, the diode contact material can be selected to have a work function 0.3 to 1 eV lower than that of the phase change material. For the above-described PCM materials, such a diode contact material can be, for example, titanium, molybdenum, aluminum, tantalum, tungsten, manganese, zirconium, and hafnium. For an n-type device, the diode contact material can include a material having a work function higher than the barrier height of the phase change material. In some embodiments, the diode contact material can be selected to have a work function 0.3 to 1 eV higher than that of the phase change material. For the above-described PCM materials, such a material can be, for example, Mo, TiN, W, Au, Co, Cu, Ni, Pd, Ir, or other suitable materials.

[0057] As described above, in order for the Schottky barrier formed at the interface between the electrode made of the diode contact material and the phase change material 430 to function as a Schottky diode, the first electrode 410 and the second electrode 420 are made of different contact materials. Thus, in one example, the first electrode 410 is a low-resistance metal and the second electrode 420 is a diode contact material. Thus, in another example, the second electrode 420 is a low-resistance metal and the first electrode 410 is a diode contact material. The first electrode 410 and the second electrode 420 may be separate layers and materials from the word lines and bit lines attached to these electrodes, or may not be clearly distinguishable from the word lines and bit lines to which these electrodes are attached (for example, the word lines or bit lines may be made of a diode contact material or a low-resistance metal or both). It should be noted that this is the case.

[0058] The above description of various embodiments of the present invention has been presented for purposes of illustration, and it is not intended that the above description be exhaustive or that the above description be limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art that do not depart from the scope of the described embodiments. The terms used herein have been selected to best explain the principles of the embodiments, practical applications, or technical improvements not found in commercially available technologies, or to enable those skilled in the art to understand the embodiments disclosed herein. Therefore, it is intended that the present invention not be limited to the exact forms and details described and illustrated, and that it be included within the scope of the appended claims.

[0059] In a preferred embodiment of the present invention, a non-volatile memory structure is provided, which includes a phase change memory comprising a phase change material and a Schottky diode in series with the phase change memory, and the Schottky barrier of the Schottky diode is the surface of the phase change memory. The Schottky barrier is preferably the interface between the phase change material and the contact. The work function of the contact material is preferably 0.3 to 1 eV lower than the work function of the phase change material. The contact material can be selected from the group consisting of titanium, molybdenum, aluminum, tantalum, tungsten, manganese, zirconium and hafnium. The work function of the contact material is preferably 0.3 to 1 eV higher than the work function of the phase change material. The contact material can be selected from the group consisting of molybdenum, titanium nitride, tungsten, gold, cobalt, copper, nickel, palladium and iridium.

[0060] In another preferred embodiment of the present invention, a non-volatile memory structure including a plurality of bit lines and a plurality of word lines is provided, and a PCM memory structure is disposed between the plurality of bit lines and the plurality of word lines. The PCM memory structure includes a phase change material and a Schottky diode in series with the PCM memory, and the Schottky barrier is the interface between the phase change material and the contact. The work function of the contact material is preferably 0.3 to 1 eV lower than the work function of the phase change material. The work function of the contact material is preferably 0.3 to 1 eV higher than the work function of the phase change material.

Claims

1. A non-volatile memory structure comprising: A phase change memory including a phase change material; A first electrode that is in direct contact with a first surface of the phase change material and has a width equal to the width of the phase change material; A phase change material (PCM) heater that is in direct contact with a second surface of the phase change material, wherein the second surface of the phase change material is on the side opposite to the first surface of the phase change material, the PCM heater; Including The first electrode and the PCM heater are made of different materials; A non-volatile memory structure.

2. A non-volatile memory structure comprising: A phase change memory including a phase change material; A first electrode that is in direct contact with the upper surface of the phase change material; A phase change material (PCM) heater that is in direct contact with the side wall and the bottom surface of the phase change material; Including The first electrode and the PCM heater are made of different materials; A non-volatile memory structure.

3. The work function of the material of the PCM heater is 0.3 to 1 eV lower than the work function of the phase change material, the structure according to claim 1 or 2.

4. The material of the first electrode is selected from the group consisting of aluminum, tungsten, copper, titanium nitride, and tantalum nitride, and the material of the PCM heater is selected from the group consisting of molybdenum, tantalum, tungsten, manganese, zirconium, and hafnium, the structure according to claim 3.

5. The work function of the material of the PCM heater is 0.3 to 1 eV higher than the work function of the phase change material, the structure according to claim 1 or 2.

6. The material of the first electrode is selected from the group consisting of aluminum, tungsten, copper, titanium nitride, and tantalum nitride, and the material of the PCM heater is selected from the group consisting of molybdenum, tungsten, gold, cobalt, copper, nickel, palladium, and iridium, the structure according to claim 5.

7. A second electrode that is in direct contact with the PCM heater, wherein the first electrode and the second electrode are made of a first material, and the PCM heater is made of a second material, the structure according to claim 1.

8. A second electrode that is in direct contact with the bottom surface of the PCM heater, wherein the first electrode and the second electrode are made of a first material, and the PCM heater is made of a second material, the structure according to claim 2.

9. A non-volatile memory structure comprising: A non-volatile memory structure comprising a phase change material disposed between a first electrode and a second electrode, wherein an upper surface of the first electrode is in direct contact with a bottom surface of the phase change material, the bottom surface of the phase change material is in direct contact with an upper surface of the second electrode, and the first electrode and the second electrode are made of different materials. Non-volatile memory structure.

Images