Phase change memory devices and fabrication methods thereof
In a memory device, at least one conductive contact having a width of less than, or equal to, about 30 nm may be formed on a first electrode. A dielectric layer may be formed on the sides of the at least one conductive contact, and a phase change material film may be formed on the conductive contact. A second electrode may be formed on the phase change material.
This application claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2005-0013143, filed on Feb. 17, 2005, in the Korean Intellectual Property Office (KIPO), the entire contents of which are incorporated herein by reference.
BACKGROUND1. Field of the Invention
Example embodiments of the present invention relate to phase change memory devices and fabrication methods thereof.
2. Description of the Related Art
Semiconductor memory devices may be volatile or nonvolatile memory devices according to whether data is retained when powered off. Volatile memory devices include, for example, dynamic random access memories (DRAM), static random access memories (SDRAM), etc. Nonvolatile memory devices include, for example, flash memory devices. Related art memory devices represent logic or binary values “0” or “1” according to whether or not an electric charge is stored therein. In one example, a DRAM may require a higher charge storage capacity because it may need to be refreshed periodically. However, as charge storage capacity increases, so does surface area of a capacitor electrode of the DRAM. This may suppress integration of the DRAM.
In another example, a flash memory cell has a gate pattern including a gate insulating film, a floating gate, a dielectric film and a control gate, which may be sequentially deposited on a semiconductor substrate. Data may be written in or erased from the flash memory cell by tunneling of electric charges through the gate insulating film. To do so, an operating voltage higher than a source voltage may be required, and the flash memory device may need to have an amplifier circuit for generating voltages necessary for the data writing/erasing operations.
An example memory, which may have nonvolatile/random access characteristics, an increased integration degree and/or a simple structure is a phase change memory device using phase change material. The phase change material may become an amorphous state or a crystalline state according to strength of a current (e.g., joule's heat) provided thereto, and the amorphous phase change material may have an electrical conductivity different from that of the crystalline phase change material.
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The amorphous phase change material film may have a higher resistance than the crystalline phase change material film. Accordingly, whether data stored in the phase change memory cell is logic “1” or logic “0” may be determined by detecting a current flowing through the phase change material film. The phase change material film may be comprised of a chalcogenide or any other suitable substance having similar or substantially. similar properties. For example, the phase change material film may be comprised of a compound containing germanium (Ge), antimony (Sb), tellurium (Te) or any other suitable element, substance or compound having similar, or substantially similar, properties.
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In the example related art phase change memory device of
Example embodiments of the present invention provide phase change memory devices, and methods of fabricating the same, which may require a lower driving current pulse and/or consume less power.
A memory device according to an example embodiment of the present invention may include at least one conductive contact formed on a first electrode. The conductive contact may have a width of less than, or equal to, about 30 nm. A dielectric layer may be formed on the sides of the at least one conductive contact, and a phase change material film may be formed on the conductive contact. A second electrode may be formed on the phase change material film. A transistor may be electrically connected to the first electrode. A phase change catalyst may be formed between the sides of the conductive contact and the dielectric layer, such that the phase change catalyst contacts the phase change material film.
In a method for fabricating a phase change memory device according to an example embodiment of the present invention, a first electrode may be formed on a semiconductor substrate, which may include a transistor. At least one conductive contact may be formed on the first electrode, and the dielectric layer may be formed on first electrode such that the dielectric layer contacts the sides of the conductive contact. A phase change material film and a second electrode may be formed on the conductive contact and the dielectric layer. The phase change material film and the second electrode may be patterned.
In example embodiments of the present invention, a conductive contact layer, a first mask layer and a second mask layer may be sequentially formed on the first electrode. The second mask layer may have a width less than the first mask layer. An oxide layer may be formed on at least one side of the second mask layer and may have a width less than, or equal to, about 30 nm. The second mask layer may be removed, and the first mask layer and the conductive contact layer may be etched to form at least one stack. A dielectric layer may be formed on the at least one stack and the first electrode, and the dielectric layer and the at least one stack may be planarized.
In a method of forming a memory device, according to another example embodiment of the present invention, a first electrode may be formed on a semiconductor substrate including a transistor. A conductive contact may be formed on the first electrode, and a phase change catalyst may be formed on each side of the conductive contact. A dielectric layer may be formed on each side of the phase change catalyst, and a phase change material film and a second electrode may be formed on the conductive contact and the first electrode. The phase change material film and the second electrode may be patterned.
In example embodiments of the present invention, the phase change catalyst may include one of ZnS, ZnS+SiO2, and Al2O3, the first electrode, the second electrode and/or the conductive contact may be comprised of materials including at least Ti. The dielectric layer may include one of Si3N4 and TEOS oxide and/or the phase change material film is formed to have a thickness of about 1000 Å.
In example embodiments of the present invention, the conductive contact layer, a first mask layer and a second mask layer may be sequentially formed on the first electrode. The second mask layer may have a width less than the first mask layer. An oxide layer may be formed on at least one side of the second mask layer, the oxide layer having a width less than, or equal to, about 30 nm. The second mask layer may be removed and the first mask layer and the conductive contact layer may be etched to form at least one stack. A phase change catalyst layer may be formed on the first electrode and may cover the at least one stack. A portion of the phase change catalyst layer may be removed to form the phase change catalyst on each side of the conductive contact, and a dielectric layer covering the at least one stack and remaining portion of the phase change catalyst layer may be formed. The dielectric layer, the at least one stack, and the phase change catalyst layer may be planarized.
In example embodiments of the present invention, the oxide layer may be formed by depositing an oxide layer on the first and second mask layers, and etching the oxide layer to form an oxide layer on at least one side of the second mask layer. The oxide layer may be deposited to have a thickness of about 20 nm to about 50 nm, inclusive, or to have a thickness of less than, or equal to, about 30 nm. The oxide layer may be deposited using chemical vapor deposition or atomic layer deposition.
The present invention will become more apparent by describing in detail the example embodiments shown in the attached drawings in which:
Various example embodiments of the present invention will now be described more fully with reference to the accompanying drawings in which some example embodiments of the invention are shown. In the drawings, the thicknesses of layers and regions are exaggerated for clarity.
Detailed illustrative embodiments of the present invention are disclosed herein. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments of the present invention. This invention may, however, may be embodied in many alternate forms and should not be construed as limited to only the embodiments set forth herein.
Accordingly, while example embodiments of the invention are capable of various modifications and alternative forms, embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit example embodiments of the invention to the particular forms disclosed, but on the contrary, example embodiments of the invention are to cover all modifications, equivalents, and alternatives falling within the scope of the invention. Like numbers refer to like elements throughout the description of the figures.
It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments of the present invention. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
It will be understood that when an element or layer is referred to as being “formed on” another element or layer, it can be directly or indirectly formed on the other element or layer. That is, for example, intervening elements or layers may be present. In contrast, when an element or layer is referred to as being “directly formed on” to another element, there are no intervening elements or layers present. Other words used to describe the relationship between elements or layers should be interpreted in a like fashion (e.g., “between” versus “directly between”, “adjacent” versus “directly adjacent”, etc.).
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising,”, “includes” and/or “including”, when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the FIGS. For example, two FIGS. shown in succession may in fact be executed substantially concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
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A phase change catalyst 132 may be formed on each side of, or around, the conductive contact 130. A phase change material film 140 contacting the conductive contact 130 maybe formed on the insulation layer 120. An upper electrode 150 may be formed on the phase change material film 140.
The conductive contact 130 may be comprised of TiN, TiAIN or any other suitable material with similar, or substantially similar, conductive properties, and may have a width of about 30 nm or less. In an example embodiment of the present invention, the upper electrode 150 and/or the conductive contact 130 may be formed to have a contact surface 134 of about 200 nm×20 nm there between. The contact surface 134 may have a width of less than, or equal to, about 30 nm.
The phase change material film 140 may be comprised of a chalcogenide, or any other material with similar or substantially similar properties. Chalcogenide and similar substances are well known to those skilled in the art. The phase change catalyst 132 may be comprised of, for example, ZnS, ZnS+SiO2, or Al2O3, and may accelerate and/or improve a phase change of the phase change material film 140. Reference numeral 142 denotes an area in which the phase change material film 140 may be phase-changed in response to a current flow from, for example, the outside.
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Example embodiments of the present invention may provide a conductive contact having a width of less than, or equal to, 30 nm, reduce a contact area between the conductive contact and the phase change material film, increase a current density at the contact area, and/or reduce the strength of a current applied to the memory device.
In example embodiments, the phase change material film may include chalcogenide alloys such as germanium-antimony-tellurium (Ge—Sb—Te), arsenic-antimony-tellurium (As—Sb—Te), tin-antimony-tellurium (Sn—Sb—Te), or tin-indium-antimony-tellurium (Sn—In—Sb—Te), arsenic-germanium-antimony-tellurium (As—Ge—Sb—Te). Alternatively, the phase change material film may include an element in Group VA-antimony-tellurium such as tantalum-antimony-tellurium (Ta—Sb—Te), niobium-antimony-tellurium (Nb—Sb—Te) or vanadium-antimony-tellurium (V—Sb—Te) or an element in Group VA-antimony-selenium such as tantalum-antimony-selenium (Ta—Sb—Se), niobium-antimony-selenium (Nb—Sb—Se) or vanadium-antimony-selenium (V—Sb—Se). Further, the phase change material film may include an element in Group VIA-antimony-tellurium such as tungsten-antimony-tellurium (W—Sb—Te), molybdenum-antimony-tellurium (Mo—Sb—Te), or chrome-antimony-tellurium (Cr—Sb—Te) or an element in Group VIA-antimony-selenium such as tungsten-antimony-selenium (W—Sb—Se), molybdenum-antimony-selenium (Mo—Sb—Se) or chrome-antimony-selenium (Cr—Sb—Se).
Although the phase change material film is described above as being formed primarily of ternary phase-change chalcogenide alloys, the chalcogenide alloy of the phase change material could be selected from a binary phase-change chalcogenide alloy or a quaternary phase-change chalcogenide alloy. Example binary phase-change chalcogenide alloys may include one or more of Ga—Sb, In—Sb, In—Se, Sb2—Te3 or Ge—Te alloys; example quaternary phase-change chalcogenide alloys may include one or more of an Ag—In—Sb—Te, (Ge—Sn)—Sb—Te, Ge—Sb—(Se—Te) or Te81—Ge15—Sb2—S2 alloy, for example.
In an example embodiment, the phase change material film may be made of a transition metal oxide having multiple resistance states, as described above. For example, the phase change material may be made of at least one material selected from the group consisting of NiO, TiO2, HfO, Nb2O5, ZnO, WO3, and CoO or GST (Ge2Sb2Te5) or PCMO(PrxCa1−xMnO3). The phase change material film may be a chemical compound including one or more elements selected from the group consisting of S, Se, Te, As, Sb, Ge, Sn, In and Ag.
While example embodiments of the present invention have been particularly shown and described with reference to the drawings, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.
Claims
1. A memory device comprising:
- a first electrode;
- at least one conductive contact formed on the first electrode and having a width of less than, or equal to, about 30 nm;
- a dielectric layer formed on the sides of the at least one conductive contact;
- a phase change material film formed on the conductive contact;
- a second electrode formed on the phase change material film; and
- a transistor electrically connected to the first electrode.
2. The device of claim 1, further including
- a phase change catalyst formed between the sides of the conductive contact and the dielectric layer, such that the phase change catalyst contacts the phase change material film.
3. The device of claim 2, wherein the phase change catalyst includes one of ZnS, ZnS+SiO2, and Al2O3.
4. The memory device of claim 1, wherein the first electrode, the second electrode and the conductive contact are comprised of materials including at least Ti.
5. The memory device of claim 1, wherein the dielectric layer includes one of Si3N4 and TEOS oxide or the phase change material film is formed to have a thickness of about 1000 Å.
6-20. (canceled)
Type: Application
Filed: Oct 8, 2008
Publication Date: Feb 12, 2009
Inventors: Dong-Seok Suh (Seoul), Yeon-Ho Khang (Yongin-si), VassIII Leniachine (Suwon-si), Mi-Jeong Song (Suwon-si), Sergey Antonov (Petersburg)
Application Number: 12/285,523
International Classification: H01L 45/00 (20060101);