Integrated Circuit Memory Devices and Capacitors Having Carbon Nanotube Electrodes
An integrated circuit capacitor includes first and second electrodes and at least one dielectric layer extending between the first and second electrodes. The first electrode includes at least one carbon nanotube. The capacitor further includes an electrically conductive catalyst material. This catalyst material may be selected from the group consisting of iron, nickel and cobalt and alloys thereof.
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This application is a divisional of U.S. patent application Ser. No. 11/205,253, filed Aug. 16, 2005, which claims priority to Korean Patent Application No. 2004-71892, filed Sep. 8, 2004, the disclosures of which are hereby incorporated herein by reference.
FIELD OF THE INVENTIONThe present invention relates to integrated circuit devices and methods of forming integrated circuit devices and, more particularly, to integrated circuit devices having on-chip capacitors and methods of forming integrated circuit devices having on-chip capacitors.
BACKGROUND OF THE INVENTIONA carbon nanotube (CNT) has a tube structure in which carbon atoms are combined with others in a form of a hexagonal lattice. The carbon nanotube may have a diameter of several nanometers. The carbon nanotube may be known as a defect-free material having superior mechanical strength, high electrical selectivity, excellent field-emission performance, and efficient hydrogen storage capability. The carbon nanotube is usually manufactured by high synthesis technologies such as arc discharge, pyrolysis, laser deposition, plasma enhanced chemical vapor deposition, thermal chemical vapor deposition, electrolysis, and flame synthesis.
Efforts to use the aforementioned properties of the carbon nanotube have been made in a variety of fields. For example, U.S. Patent Publication No. 2003/0100189 A1 discloses a method of forming a catalyst metal on a substrate and growing a carbon nanotube thereon. At least one problem with the method disclosed in this document is that it is difficult to obtain a carbon nanotube vertically oriented against the substrate.
SUMMARY OF THE INVENTIONEmbodiments of the invention include a semiconductor memory device having a cell transistor formed on a semiconductor substrate and having a source region, a drain region, and a word line traversing an upper portion of a channel region provided between the source region and the drain region. A bit line is electrically connected to the drain region of the cell transistor via a bit line contact plug. A storage region is electrically connected to the source region via a buried contact plug. The storage region includes a carbon nanotube.
Additional embodiments of the invention include methods of manufacturing a semiconductor memory device. These methods include forming a cell transistor on a semiconductor substrate. The cell transistor includes a source region, a drain region, and a word line traversing an upper portion of a channel region provided between the source region and the drain region. An insulating layer is also formed on the substrate. A buried contact plug is formed in the insulating layer. The buried contact plug is electrically connected to the drain region. A lower electrode having a carbon nanotube is formed on the buried contact plug. A step is then performed to form a storage dielectric layer on a surface of the lower electrode. An upper capacitor electrode is then formed on the storage dielectric layer.
Still further embodiments of the invention include an integrated circuit device having an integrated circuit capacitor therein. This integrated circuit capacitor includes first and second electrodes and at least one dielectric layer extending between the first and second electrodes. The first electrode includes at least two carbon nanotubes and an electrically conductive diffusion layer in gaps between the at least two carbon nanotubes. The integrated circuit device further includes a semiconductor substrate and an electrically conductive plug. This conductive plug electrically connects the first electrode to the semiconductor substrate. The capacitor further includes an electrically conductive catalyst material. This electrically conductive catalyst material extends between the electrically conductive plug and the at least two carbon nanotubes. This catalyst material may be selected from the group consisting of iron, nickel and cobalt and alloys thereof. The conductive plug may also include a material selected from the group consisting of tungsten, titanium, tantalum and polysilicon.
The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the thickness of layers and regions are exaggerated for clarity. Like numbers refer to like elements throughout. It will be understood that when an element such as a layer, region or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. Moreover, each embodiment described and illustrated herein includes its complementary conductivity type embodiment as well.
A transistor is defined by the source 103, the drain 105, and the gate provided on the active region. Furthermore, a first interlayer insulating layer 115 covering the transistor is formed thereon. The upper surface of the first insulating interlayer 115 is provided with a bit line 117, which is electrically connected to the drain 105 via a bit line contact plug 118. Preferably, the bit line 117 is provided with a conductor for electrical connection with the bit line contact plug 118 and a bit line spacer for protecting the conductor.
On the upper surface of the bit line 117, a second interlayer insulating layer 119 is provided to fully cover the bit line 117. Subsequently, a buried contact plug 121 is provided by a self-aligned contact process. The self-aligned contact process is a technique that makes it possible to form bit lines and word lines, and then form contact holes by using the bit lines and the word lines as an etching mask. In case the contact holes are filled with a conductive material, plugs are formed and they can be electrically connected to the source or the drain of the active region located under the interlayer insulating layers.
On the buried contact plug 121 formed by the self-aligned contact process, a lower electrode 123 is formed. The lower electrode 123 has at least one carbon nanotube therein. More specifically, the lower electrode 123 may be made of only one carbon nanotube or two or more carbon nanotubes.
If the lower electrode 123 has two or more carbon nanotubes, a diffusion barrier 125 may be formed to fill the gaps between the carbon nanotubes, and to prevent oxygen atoms contained in a dielectric material from being diffused into the lower electrode 123 and to facilitate a bonding between the lower electrode 123 and the dielectric film. The diffusion barrier 125 may be made of a predetermined conductive material by chemical vapor deposition or atomic layer deposition. Specifically, on the surface of the diffusion barrier 125, a dielectric film 127 is provided. In addition, an upper electrode 129 is formed on the surface of the dielectric film 127. An etching protection layer 131 is also provided under the upper electrode 129. The etching protection layer 131 protects the second insulating interlayer 119 during an etching process for forming the upper electrode 129. If the lower electrode 123 has only one carbon nanotube, a dielectric film may be provided on the surface of the carbon nanotube, and an upper electrode may be provided on the surface of the dielectric film. Alternatively, the diffusion barrier is provided on the surface of the carbon nanotube, and the upper electrode is provided on the diffusion barrier.
A buried contact hole is formed in the second interlayer insulating layer 201. The buried contact hole may be formed by depositing a photoresist layer (not shown) on the second interlayer insulating layer 201 and then patterning the photoresist layer by a photolithography process. By the patterning process, predetermined portions of the second interlayer insulating layer 201 are exposed. Then, anisotropic dry etching is applied to the exposed portions of the second interlayer insulating layer 201 to define opening therein. Subsequently, anisotropic dry etching is applied to the first interlayer insulating layer disposed underneath the second insulating interlayer 201 to thereby expose a source region of a cell transistor. (See also
The buried contact hole formed by the anisotropic dry etching is then filled with a conductive material, which is patterned to define a buried contact plug 203. The conductive material may be selected from a group consisting of W, Ti, Ta and poly-silicon. Preferably, the buried contact plug 203 is made of tungsten (W) due to its good step coverage. Also, the buried contact plug 203 may be formed by filling the buried contact hole and extending it to the upper surface of the second interlayer insulating layer 201. If the buried contact plug 203 is made of poly-silicon, silicide (not shown) may be provided by depositing Ni or Co metal on the buried contact plug 203 and then performing heat treatment to convert the metal to a metal silicide.
Referring to
Referring to
Referring to
Then, an etching process is performed to provide a catalyst metal particle 211 in each guide pattern 209. Preferably, the etching process may be a wet etching process using an HF aqueous solution. More specifically, the substrate on which the catalyst metal material is deposited can be dipped into the HF aqueous solution for several tens or hundreds seconds to perform a wet etching for the surface of the catalyst metal material. The dipping time may be appropriately controlled depending on the number and the sizes of the catalyst metal particles that will be formed. The dipping time necessary to form one catalyst metal particle 211 in the guide pattern 209 may be 10 through 200 seconds.
After the wet etching using the HF aqueous solution, dry etching using an NH3 gas may be performed for the directional growth of the carbon nanotube. The wet etching using the HF aqueous solution can provide the catalyst metal particle 211. However, its surface may be rough. Therefore, an NH3 gas is supplied to the substrate and guide patterns 209 with a predetermined flux for several tens of minutes to obtain the catalyst metal particle 211 having a smooth hemispherical shape. By performing wet etching using the HF aqueous solution and/or the dry etching using an NH3 gas, it is possible to remove the catalyst metal materials formed on the side-walls of the guide patterns 209.
Referring to
Referring to
The entire surface of the etching protection layer 205 and the dielectric film 215 are covered with a conducting material to form an upper capacitor electrode 217. As a result, it is possible to provide a semiconductor memory device having a carbon nanotube 213 that operates as a capacitor electrode with a memory cell. Alternatively, the method of growing the carbon nanotube 213 using the guide pattern 209 may be modified. More specifically, a process of removing a portion of the carbon nanotube protruding from the third interlayer insulating layer 207 (see
After the wet etching using the HF aqueous solution, a dry etching using an NH3 gas may be performed for the directional growth of the carbon nanotubes. The wet etching using the HF aqueous solution can provide catalyst metal particles 311. However, their surfaces may be rough. To remedy this roughness, an NH3 gas is supplied to the semiconductor substrate with a predetermined flux for at least several minutes to obtain a plurality of catalyst metal particles 311 having smooth hemispherical shapes.
Referring to
Referring to
Alternatively, the method of growing the carbon nanotubes 313 using the guide pattern 309 may be differently embodied. More specifically, a process of removing portions of the carbon nanotubes 313 protruding from the third interlayer insulating layer may be added after the carbon nanotubes of a predetermined length are synthesized. The length of the carbon nanotubes 313 can be controlled by chemical mechanical polishing. Processes for depositing the dielectric film 315 and forming the upper capacitor electrode after controlling the length of the carbon nanotubes 313 are similar to those of the aforementioned embodiment.
Thus, as described herein, guide patterns are used to induce the directional growth of carbon nanotubes, and catalyst metal particles are used to support formation of a lower capacitor electrode of a semiconductor memory device. As a result, it is possible to obtain a semiconductor memory device having a carbon nanotube used as a lower capacitor electrode. The carbon nanotube has a cylindrical shape with a high aspect ratio. Therefore, it is possible to obtain a storage capacitor having high capacitance. Since a work function of the carbon nanotube is typically 4.7 through 5.0 eV, it is possible to reduce leakage currents that can occur between the lower capacitor electrode and the dielectric film. Furthermore, since the carbon nanotube has a π bonding structure which is chemically stable, it provides tolerance of chemical influences in subsequent fabrication processes and excellent stability for heat flux.
While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The exemplary embodiments should be considered in descriptive sense only and not for purposes of limitation. Therefore, the scope of the invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being included in the present invention.
Claims
1. An integrated circuit device, comprising:
- an integrated circuit capacitor having first and second electrodes and at least one dielectric layer extending between the first and second electrodes, said first electrode comprising at least two carbon nanotubes and an electrically conductive diffusion barrier layer interposed between the carbon nanotube and the dielectric layer.
2. The device of claim 1, further comprising:
- a semiconductor substrate; and
- an electrically conductive plug electrically connecting said first electrode to said semiconductor substrate.
3. The device of claim 2, further comprising an electrically conductive catalyst material extending between said electrically conductive plug and the at least two carbon nanotubes.
4. The device of claim 3, wherein the catalyst material is selected from the group consisting of iron, nickel and cobalt and alloys thereof.
5. The device of claim 4, wherein said electrically conductive plug comprises a material selected from the group consisting of tungsten, titanium, tantalum and polysilicon.
6. The device of claim 2, wherein said electrically conductive plug comprises a material selected from the group consisting of tungsten, titanium, tantalum and polysilicon.
7. An integrated circuit device, comprising:
- a semiconductor substrate having a field effect transistor adjacent a surface thereof, said field effect transistor comprising source and drain regions in said semiconductor substrate and an insulated gate electrode on the surface, between the source and drain regions;
- a first interlayer insulating layer on said semiconductor substrate;
- a bit line on said first interlayer insulating layer;
- a bit line contact plug that extends through said first interlayer insulating layer and electrically connects said bit line to the drain region;
- a second interlayer insulating layer on said first interlayer insulating layer and said bit line;
- a buried contact plug that extends through said first and second interlayer insulating layers and contacts the source region; and
- a storage capacitor on said buried contact plug, said storage capacitor comprising a lower carbon nanotube electrode electrically connected to said buried contact plug, a dielectric layer on the lower carbon nanotube electrode and an upper electrode on the dielectric layer.
8. The device of claim 7, further comprising an electrically conductive catalyst material extending between said buried contact plug and the lower carbon nanotube electrode.
9. The device of claim 8, wherein the catalyst material is selected from the group consisting of iron, nickel and cobalt and alloys thereof.
10. The device of claim 9, wherein said buried contact plug comprises a material selected from the group consisting of tungsten, titanium, tantalum and polysilicon.
Type: Application
Filed: Feb 6, 2008
Publication Date: Jun 19, 2008
Applicant:
Inventors: Young-Moon Choi (Seoul), In-Seok Yeo (Seoul), Sun-Woo Lee (Gyeonggi-do)
Application Number: 12/026,563
International Classification: H01L 29/94 (20060101);