Storage nodes and methods of manufacturing and operating the same, phase change memory devices and methods of manufacturing and operating the same
In various embodiments, the present disclosure may provide a storage node. In various implementations, the storage node may include a bottom electrode having a non-planar bottom surface that conforms with and is connected to a non-planar top surface of a diode electrode of a memory device. The storage node may further include a phase change layer on top of a bottom diode and a top electrode on a top surface of a phase change layer.
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This application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2006-0130443, filed on Dec. 19, 2006, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
BACKGROUND1. Field
The present disclosure relates to a semiconductor memory devices and methods of manufacturing and operating the same.
2. Description of the Related Art
Non-volatile memory devices may retain data stored therein even when not powered. Representative examples of non-volatile memory devices include flash memory devices and phase change memory devices. A unit cell of phase change memory devices may include a cell switching device and a storage node electrically connected to the switching device. The storage node may include a phase change material layer, a top electrode, and/or a bottom electrode. The phase change material layer may be disposed between the top and bottom electrodes. The cell switching device may be an active device such as a transistor or a vertical diode that must be electrically operated to record data to the phase change memory cell.
SUMMARYIn various embodiments, the present disclosure provides a storage node. In various implementations, the storage node may include a bottom electrode having a non-planar bottom surface that is connected to a switching device of a memory device. The storage node may further include a phase change layer on top of the bottom electrode and a top electrode on a top surface of the phase change layer.
In accordance with various other embodiments of the present disclosure, a phase change memory device is provided. In various implementations the phase change memory devices may include a semiconductor substrate and storage node that may include a bottom electrode having a non-planar bottom surface that is connected to a switching device of the memory device. The storage node may further include a phase change layer on top of the bottom electrode and a top electrode on a top surface of the phase change layer.
In still other various embodiments, the present disclosure provides methods for manufacturing a phase change memory device may include forming an insulating interlayer on a semiconductor substrate, forming a hole in the insulating interlayer to expose the semiconductor substrate, forming a diode in a lower region of the hole, forming a diode electrode on the diode so that an exposed surface of the diode electrode is not planar, forming a bottom electrode to cover an exposed surface of the diode electrode, and sequentially forming a phase change layer and a top electrode on the bottom electrode.
In yet other various embodiments, the present disclosure provides a method of operating a phase change memory device including a diode and a storage node connected to the diode. The method may include applying an operating voltage to the storage node in a direction in which the diode can be turned on, wherein the storage node is connected to the diode by a diode electrode, and an interface between the storage node and the diode electrode is curved.
Accordingly, because a contact area between the bottom electrode of the storage node and the diode that is a switching device is increased and a contact resistance between the bottom electrode and the diode is reduced, a current flowing through a contact region between the bottom electrode and the diode can be increased, thereby improving the integration density of the phase change memory device.
The above and other features and advantages of the present disclosure will become more apparent by describing in detail example embodiments thereof with reference to the attached drawings.
The present disclosure will now be described more fully with reference to the accompanying drawings, in which example embodiments are shown. In the drawings, the thicknesses of layers or regions are exaggerated for clarity. The following embodiments should not be construed as limiting the scope of the present disclosure.
Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. The example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90° or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. 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.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Referring to
In various embodiments, the first semiconductor layer 16n may include any one of the first and second conductive impurities, and may have an impurity concentration lower than that of each of the semiconductor substrate 10 and the second semiconductor layer 16p. Such a configuration of the first semiconductor layer 16n will minimize leakage current through the diode D when a reverse bias voltage is applied to the diode D. In various forms, a top surface of the second semiconductor layer 16p may be non-planar and may have a diode electrode 18 disposed on the non-planar top surface of the second semiconductor layer 16p. For example, in various embodiments, the top surface of the second semiconductor layer 16p may be concave and the diode electrode 18 may thinly cover the concave top surface of the second semiconductor layer 16p without completely filling a concave portion of the second semiconductor layer 16p. In various embodiments, the diode electrode 18 may be thicker than the second semiconductor layer 16p if the recess G of the top surface of the diode D is maintained.
Accordingly, the diode electrode 18 may have a concave top surface conforming to the concave top surface of the second semiconductor layer 16p. In various alternative embodiments, the top surface of the second semiconductor layer 16p may be upwardly convex, rather than concave. More particularly, the top surface of the second semiconductor layer 16p may be non-planar, for example the top surface may be concave or convex. The concavity or convexity may be formed as a smooth surface, e.g., a rounded bowl or dome, or may be formed to have sides that join each other and a bottom at angled corners.
The diode electrode 18 may be a conductive layer, for example, a metal silicide layer. The metal silicide layer may be any suitable metal silicide layer such as a cobalt silicide (CoSi2) layer, a titanium silicide (TiSi2) layer, or a nickel silicide (NiSi2) layer. Alternatively, the diode electrode 18 may be formed of at least one of TiSi2, CoSi2, and NiSi2. The diode electrode 18 need not completely fill the hole 14h. Accordingly, the diode electrode 18 may have a top surface lower than a top surface of the first insulating interlayer 14. In some embodiments, a sidewall of the hole 14h over the diode electrode 18 may be covered by an annular spacer 20 that covers an edge of the diode electrode 18. Additionally, in various embodiments, the exposed non-planar surface of the diode electrode 18 inside the spacer 20 may be covered by a bottom electrode 22a. In accordance with various implementations, an upper region of the hole 14h over the bottom electrode 22a and surrounded by the spacer 20 may be filled with a phase change layer 24. As a result, the spacer 20 may be disposed between the bottom electrode 22a and the phase layer 24 and the sidewall of the hole 14h facing the bottom electrode 22a and the phase change layer 24. In various example configurations, the phase change layer 24 may extend beyond the first insulating interlayer 14 around the hole 14h and a top electrode 26 may be disposed on the phase change layer 24.
Because the bottom electrode 22a may cover the non-planar top surface of the diode electrode 18, the bottom electrode 22a and the diode electrode 18 may have a non-planar interface therebetween. Additionally, regions for forming the bottom electrode 22a and the phase change layer are limited by the spacer 20.
In accordance with various embodiments, the bottom electrode 22a may be formed of a conductive material that does not react with the phase change layer 24. For example, the bottom electrode 22a may be a titanium nitride (TiN) electrode or a titanium aluminum nitride (TiAlN) electrode. Accordingly, the bottom electrode 22a may act as a thermally stable heater. The bottom electrode 22a, the phase change layer 24, and/or the top electrode 26 sequentially stacked on the diode electrode 18 collectively function as a storage node Rp in which data is stored.
As shown in
In various implementations, the phase change layer 24 may be a germanium-antimony-tellurium (GeSbTe, GST) layer or a chalcogenide layer and the top electrode 26 may be an electrode formed of a conductive material that does not react with the phase change layer 24, for example, a TiN electrode or a TiAlN electrode.
As described above, because the spacer 20 may be disposed between the sidewall of the hole 14h and the bottom electrode 22a and the phase change layer 24, a contact area between the phase change layer 24 and the bottom electrode 22a may be reduced. As a result, heat generation efficiency in an interface between the bottom electrode 22a and the phase change layer 24 is increased, thereby reducing a program current.
Referring to
Referring to
Generally, each of the respective first semiconductor layer 16n, the second semiconductor layer 6p and the semiconductor substrate 10 can be doped with n or p impurities such that the combination of any two or more of the respective semiconductor layers 16n/16p and/or the substrate 10 form a diode.
When the first and second conductive impurities doped into the first and second semiconductor layers 16n and 16p are the same type as each other, for example, a p-type impurity, and different from an impurity, for example, n-type impurity, implanted into the semiconductor substrate 10, the semiconductor substrate 10 and the first semiconductor layer 16n contacting the semiconductor substrate 10 constitute a diode D.
During the ion implantation, the first semiconductor layer 16n may be doped with a concentration lower than that of each of the semiconductor substrate 10 and the second semiconductor layer 16p in order to reduce or minimize current leakage through the diode D when a reverse bias voltage is applied to the diode D.
Referring to
For example, the spacer 20 may be formed by forming the insulating layer 14 on the semiconductor substrate 10 having the hole 14h and anisotropically etching an entire top surface of the insulating layer 14. The spacer 20 may cover an edge of the second semiconductor layer 16p. Accordingly, the area of the second semiconductor layer 16p exposed through the hole 14h may be less than that before the spacer 20 is formed.
Referring to
Referring to
The diode electrode 18 may be formed of any suitable metal silicide such as CoSi2, NiSi2, or TiSi2 utilizing any suitable self-aligned silicide (salicide) forming method. As illustrated in
Referring to
Referring to
A method of operating the phase change memory device of
While the present disclosure has been particularly shown and described with reference to exemplary embodiments thereof, 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 disclosure as defined by the following claims.
As described above, the interface between the bottom electrode 22a and the diode electrode 18 of the phase change memory device, need not be planar but rather non-planar. Hence, the contact area between the bottom electrode 22a and the diode electrode 18 is larger than a contact area between the bottom electrode 22a and the diode electrode 18 when the interface therebetween is planar.
Accordingly, a contact resistance between the bottom electrode 22a and the diode electrode 18 is reduced and thus current flowing through the interface between the bottom electrode 22a and the diode electrode 18 may be increased. Consequentially, the phase change memory device of the present disclosure may perform a desired operation over a greater range operating voltages, thereby improving reliability.
Also, because the spacer 20 covers the upper sidewall of the hole 14h, during manufacturing the phase change memory device, the bottom electrode 22a, the phase change layer 24, and the top electrode 26 may be self-aligned and formed at correct positions. Hence, the method of manufacturing the phase change memory device according to the present disclosure may improve reproducibility.
Further, because the width of each of the bottom electrode 22a and the phase change layer 24 may be controlled by adjusting the thickness of the spacer 20 during the forming of the spacer 20, heat generation efficiency in the interface between the bottom electrode 22a and the phase change layer 24 may be enhanced by reducing the width of each of the bottom electrode 22a and the phase change layer 24, thereby reducing a reset current.
While example embodiments have been particularly shown and described with reference to example embodiments thereof, 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 following claims. Therefore, the scope shall be defined by the technical idea as described in the claims and not by the example embodiments.
Claims
1. A storage node, comprising:
- a bottom electrode having a non-planar bottom surface that is connected to a switching device of a memory device;
- a phase change layer on top of the bottom electrode; and
- a top electrode on a top surface of the phase change layer.
2. The storage node of claim 1, wherein a bottom surface of the bottom electrode is concave or upwardly convex.
3. The storage node of claim 1, wherein further comprising a spacer surrounding the bottom electrode and at least portion of the phase change layer.
4. The storage node of claim 1, wherein the bottom electrode is formed of a compound including at least one of titanium (Ti) and a nitride (N).
5. The storage node of claim 4, wherein the bottom electrode is formed of one of titanium nitride (TiN) and titanium aluminum nitride (TiAlN).
6. A phase change memory device comprising:
- a switching device formed on a semiconductor substrate; and
- the storage node of claim 1 connected to the switching device.
7. The phase change memory device of claim 6 further comprising:
- a first insulating interlayer having a hole having at least portion of the storage node therewithin;
- a diode filling a lower region of the hole; and
- the diode electrode on the diode.
8. The phase change memory device of claim 7, further comprising a spacer annularly disposed along a sidewall of the hole between the sidewall and the phase change layer.
9. The phase change memory device of claim 7, wherein an interface connecting the diode electrode with the bottom electrode is concave or upwardly convex.
10. The phase change memory device of claim 7, wherein the diode electrode includes silicon (Si).
11. The phase change memory device of claim 10, wherein the diode electrode includes metal silicide.
12. The phase change memory device of claim 11, wherein the diode electrode is formed of at least one of TiSi2, CoSi2, and NiSi2.
13. The phase change memory device of claim 7, wherein an area of a top surface of the diode electrode is equal to an area of a bottom surface of the bottom electrode.
14. A method of manufacturing a phase change memory device, the method comprising:
- forming an insulating interlayer on a semiconductor substrate;
- forming a hole in the insulating interlayer to expose the semiconductor substrate;
- forming a diode in a lower region of the hole;
- forming a diode electrode on the diode so that an exposed surface of the diode electrode is non-planar;
- forming a bottom electrode in contact with and conforming to the non-planar surface of the diode electrode; and
- sequentially forming a phase change layer and a top electrode on the bottom electrode.
15. The method of claim 14, wherein the forming the diode comprises:
- filling the lower region of the hole with a semiconductor layer;
- doping a lower region of the semiconductor layer with a first conductive impurity; and
- doping an upper region of the semiconductor layer with a second conductive impurity.
16. The method of claim 15, wherein the filling the lower region of the hole with the semiconductor layer comprises:
- filling the hole with a single crystal semiconductor layer using a selective epitaxial growth method;
- planarizing a top surface of the single crystal semiconductor layer until a top surface of the first insulating interlayer is exposed; and
- removing a part of the planarized single crystal semiconductor layer from the hole.
17. The method of claim 14, wherein the forming the diode electrode comprises:
- forming an annular spacer so that the spacer contacts the diode and covers a sidewall of the hole;
- forming a recess in a top surface of the diode inside the spacer; and
- covering a surface of the recess with a conductive layer.
18. The method of claim 14, wherein the diode electrode includes silicon.
19. The method of claim 18, wherein the diode electrode is formed of metal silicide.
20. The method of claim 19, wherein the metal silicide comprises at least one of TiSi2, CoSi2, and NiSi2.
21. The method of claim 14, wherein sequentially forming the phase change layer and the top electrode comprises:
- filling the hole and covering a top surface of the insulating interlayer with the phase change layer;
- forming the top electrode on a top surface of the phase change layer; and
- etching a portion of the top diode and the phase change layer to expose a top surface of the insulating interlayer.
22. The method of claim 21, wherein etching a portion of the top electrode and the phase change layer comprises:
- forming a photosensitive layer pattern on a top surface of the top electrode;
- etching the of the top electrode and the phase change layer around the photosensitive layer pattern to define a storage node region of the phase change memory device; and
- removing the photosensitive layer pattern to expose the storage node region.
23. The method of claim 14, wherein the sequentially forming the phase change layer and the top electrode comprises:
- filling the hole to a top surface of the insulating interlayer with the phase change layer;
- forming the top electrode on top surfaces of the phase change layer and the insulating interlayer; and
- etching a portion of the top electrode to expose a top surface of the insulating interlayer.
24. A method of operating a phase change memory device, the method comprising:
- applying an operating voltage to a storage node of a phase change memory device, the applied voltage inducing a current flow through the storage node and a non-planar interface between the storage node and a diode electrode connecting a diode with the storage node, the induced current turning the diode on.
25. The method of claim 24, wherein the operating voltage is one of:
- a write voltage for inducing a current to store data on the storage node;
- a read voltage for inducing a current to read data stored on the storage node; and
- an erase voltage for inducing a current to erase data stored on the storage node.
Type: Application
Filed: Dec 18, 2007
Publication Date: Sep 4, 2008
Applicant:
Inventors: Jun-ho Lee (Seoul), Sung-kwan Kang (Seoul), Hion-suck Baik (Cheonan-si), Jong-wook Lee (Yongin-si)
Application Number: 12/000,829
International Classification: H01L 47/00 (20060101); H01L 21/28 (20060101); G11C 11/00 (20060101);