Abstract:
The nanoparticle structure includes: a substrate; and nanoparticles formed on the substrate, wherein the nanoparticles include silicide. The method of manufacturing the nanoparticle structure includes: forming an Si source layer to a predetermined thickness; forming nanoparticles using a predetermined metal and silicon; depositing the nanoparticles on the Si source layer; and growing the nanoparticles to form silicide. Nanoparticles having a desired size can be easily obtained by adjusting the thickness of the silicon source layer.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS  
       [0001]     Priority is claimed to Korean Patent Application No. 10-2005-0013900, filed on Feb. 19, 2005, in the Korean Intellectual Property Office, the disclosure of which incorporated herein in its entirety by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Disclosure  
         [0003]     The present disclosure relates to a nanoparticle structure, and more particularly, to a stack structure of self-limiting nanoparticles using a predetermined metal and silicon and a method of manufacturing the same.  
         [0004]     2. Description of the Related Art  
         [0005]     In general, methods of manufacturing nanoparticles include thermal decomposition and laser ablation.  
         [0006]     In thermal decomposition, nanoparticles are manufactured using a precursor. This method is comparatively simple; however, due to the low concentration of the precursor, the yield of nanoparticles is low.  
         [0007]     In laser ablation, a target is sputtered by using a laser beam and nanoparticles are obtained from the target. In this case, the density of nanoparticles to be formed on a wafer is low, and in order to increase the density of nanoparticles, a time required for depositing the nanoparticles on the wafer should be increased. However, since laser ablation is performed within a very short time, it is difficult to obtain nanoparticles having a desired size.  
       SUMMARY OF THE DISCLOSURE  
       [0008]     The present disclosure provides a nanoparticle structure of which nanoparticles have a predetermined size obtained by adjusting the thickness of a silicon source layer, and a method of manufacturing the nanoparticle structure.  
         [0009]     According to an aspect of the present disclosure, there is provided a nanoparticle structure including: a substrate; and nanoparticles formed on the substrate, wherein the nanoparticles include silicide.  
         [0010]     The silicide may be a silicide of one element selected from the group consisting of Au, Fe, Al, Co, Ni, Cu, Ag, and Pt.  
         [0011]     The nanoparticles may be formed through laser ablation.  
         [0012]     The nanoparticles may be grown through post annealing.  
         [0013]     A post annealing temperature may be 360° C. to 1400° C., for example, 600° C. to 800° C.  
         [0014]     The substrate may include silicon.  
         [0015]     The nanoparticle structure may further include an insulating layer between the nanoparticles and the substrate.  
         [0016]     The insulating layer may be formed of at least one high-dielectric material selected from the group consisting of SiO 2 , Si 3 N 4 , Ta 2 O 3 , ZrO 2 , Al 2 O 3 , HfO 2 , HfSiO 4 , and HfAlO 4 .  
         [0017]     The nanoparticles may be substantially formed in a spherical form.  
         [0018]     According to another aspect of the present invention, there is proved a method of manufacturing a nanoparticle structure, the method including: forming an Si source layer to a predetermined thickness; forming nanoparticles using a predetermined metal and silicon; depositing the nanoparticles on the Si source layer; and growing the nanoparticles to form silicide.  
         [0019]     The metal may include at least one selected from the group consisting of Au, Fe, Al, Co, Ni, Cu, Ag, and Pt.  
         [0020]     The forming of the nanoparticles may be performed through laser ablation.  
         [0021]     The growing of the nanoparticles may be performed through post annealing.  
         [0022]     A post annealing temperature may be 360° C. to 1400° C.  
         [0023]     The forming of the Si source layer may include: preparing a substrate; and forming an insulating layer on the substrate; and forming the Si source layer on the insulating layer.  
         [0024]     The substrate may include silicon.  
         [0025]     The insulating layer may be formed of at least one high-dielectric material selected from the group consisting of SiO 2 , Si 3 N 4 , Ta 2 O 3 , ZrO 2 , Al 2 O 3 , HfO 2 , HfSiO 4 , and HfAlO 4 .  
         [0026]     In the nanoparticle structure and the method of manufacturing the same according to the present disclosure, the size of nanoparticles can be adjusted by adjusting the thickness of the silicon source layer such that nanoparticles having a desired size can be easily obtained. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]     The above and other aspects of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:  
         [0028]      FIGS. 1A through 1C  illustrate a method of manufacturing nanoparticles according to an embodiment of the present invention;  
         [0029]      FIGS. 2A through 2E  illustrate a method of manufacturing a nanoparticle structure according to another embodiment of the present invention;  
         [0030]      FIGS. 3A and 3B  illustrate experimental examples of the size of nanoparticles using different thicknesses of a silicon source layer in a nanoparticle structure and a method of manufacturing the nanoparticle structure according to the present disclosure;  
         [0031]      FIGS. 4A through 4D  illustrate experimental examples of the size of nanoparticles using different internal temperatures of a furnace in which a post annealing operation is performed, in a nanoparticle structure and a method of manufacturing the nanoparticle structure according to the present disclosure; and  
         [0032]      FIG. 5  is a graph showing the results of  FIGS. 4A through 4D . 
     
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0033]     Hereinafter, the present invention will be described in detail by explaining exemplary embodiments of the invention with reference to the attached drawings. Like reference numerals in the drawings denote like elements.  
         [0034]      FIGS. 1A through 1C  illustrate a method of manufacturing a nanoparticle structure according to an embodiment of the present invention.  
         [0035]     Referring to  FIG. 1A , first, a substrate  10  is prepared. The substrate  10  includes silicon (Si) and serves as an Si source layer for forming nanoparticles  21 .  
         [0036]     Referring to  FIG. 1B , the nanoparticles  21  are deposited on the substrate  10 , a plurality of the nanoparticles  21  forming a nanoparticle layer  20 .  
         [0037]     In an embodiment of the present invention, the nanoparticles  21  may be formed through laser ablation. Specifically, if a powder target formed of Au and Si is laser-ablated, nanolevel particles are formed. If the nanolevel particles formed in this way are deposited on the substrate  10 , the nanoparticles  21  are formed of Au and Si.  
         [0038]     Although the nanoparticles  21  are formed of Au and Si in the present embodiment, other powder metals may be used instead of the Au powder target.  
         [0039]     Referring to  FIG. 1C , the nanoparticles  21  are grown on the substrate  10 . In an embodiment of the present invention, the nanoparticles  21  may be grown by performing a post annealing operation, which may be performed in an Ar, N 2 , or He atmosphere. An internal temperature of a furnace in which the post annealing operation is performed may be from 360° C. to 1400° C., preferably, 600° C. to 800° C. This will be described later with reference to  FIGS. 4A through 4D  and  FIG. 5 .  
         [0040]     In an embodiment of the present invention, the nanoparticles  21  formed of Au and Si serve as seeds and silicon is supplied to the nanoparticles  21  from the substrate  10  to grow the nanoparticles  21 . In this case, the nanoparticels  21  become Au-silicide. When the nanoparticles  21  are grown as described above, the nanoparticles  21  may be grown in a spherical form.  
         [0041]     A thickness of the substrate  10  is adjusted so that the size of the nanoparticles  21  obtained by growing the nanoparticles  21  can be adjusted. This will be described later with reference to  FIGS. 3A and 3B .  
         [0042]      FIGS. 3A and 3B  illustrate experimental examples of the size of nanoparticles using different thicknesses of a silicon source layer in a nanoparticle structure and a method of manufacturing the nanoparticle structure according to the present disclosure.  
         [0043]      FIG. 3A  shows an experimental result of the size of nanoparticles in which the thickness of the silicon source layer is set to 2 nm, and  FIG. 3B  shows an experimental result of the size of nanoparticles in which the thickness of the silicon source layer is set to 8 nm. Only the thickness of the silicon source layer shown in  FIGS. 3A and 3B , respectively, as described above, is different, and other experimental conditions are the same.  
         [0044]     Referring to  FIGS. 3A and 3B , the size of nanoparticles to be formed when the thickness of the silicon source layer is 8 nm is larger than the size of nanoparticles formed when the thickness of the silicon source layer is 2 nm. That is, the size of the nanoparticles is determined according to the thickness of the silicon source layer. Thus, by adjusting the thickness of the silicon source layer, the nanoparticles having a required size can be easily obtained.  
         [0045]     Referring to  FIGS. 3A and 3B , according to the present disclosure, the nanoparticles can be formed in a spherical form.  
         [0046]      FIGS. 4A through 4D  illustrate experimental examples of the size or density of nanoparticles using different internal temperatures of a furnace in which a post annealing operation is performed, in a nanoparticle structure and a method of manufacturing the nanoparticle structure according to the present disclosure, and  FIG. 5  is a graph showing the results of  FIGS. 4A through 4D .  
         [0047]      FIG. 4A  shows an experimental result of the size of nanoparticles in which nanoparticles are deposited through laser ablation and a post annealing operation is not performed,  FIG. 4B  shows an experimental result of the size of nanoparticles in which the internal temperature of a furnace in which a post annealing operation is performed is set to 400° C.,  FIG. 4C  shows an experimental result of the size of nanoparticles in which the internal temperature of a furnace in which a post annealing operation is performed is set to 650° C., and  FIG. 4D  shows an experimental result of the size of nanoparticles in which the internal temperature of a furnace in which a post annealing operation is performed is set to 1000° C.  
         [0048]     The experimental examples will now be described in detail.  
         [0049]     First, Au powder (1-3 μm, 99.9%, Sigma Aldrich) and silicon powder (1 μm, 99%, Sigma Aldrich) are mixed with each other to manufacture a target for laser ablation.  
         [0050]     After that, nanoparticles formed by laser-ablating the Au/silicon target are deposited on a silicon/SiO 2 /silicon wafer for 20 seconds.  
         [0051]     After that, the nanoparticles are annealed at 450° C. to 1000° C. in an Ar atmosphere.  
         [0052]     Referring to  FIGS. 4A and 4B , the size or density of the nanoparticles does not change before and after performing the post annealing operation at 450° C. When the post annealing operation is performed at 650° C., according to  FIG. 4C , the density of the nanoparticles increase greatly and the size thereof also increases. Referring to  FIG. 4D , when the post annealing operation is performed at 1000° C., the nanoparticles are coagulated and the size of the nanoparticles also increases greatly. As such, a proper temperature required for growing nanoparticles is about 650° C. and the temperature has a close relation with a phase diagram of Au and Si. Au/Si nanoparticles are grown at a temperature at which Au/Si nanoparticles are in a liquid state and Si nanoparticles are in a solid state.  
         [0053]      FIGS. 2A through 2E  illustrate a method of manufacturing a nanoparticle structure according to another embodiment of the present invention.  
         [0054]     Referring to  FIG. 2A , first, a substrate  30  is prepared.  
         [0055]     Referring to  FIGS. 2B and 2C , an insulating layer  40  is formed on the substrate  30 , and a silicon source layer  50  is formed on the insulating layer  40 . The insulating layer  40  may be formed of SiO 2 .  
         [0056]     The silicon source layer  50  includes silicon and supplies silicon required for growing nanoparticles  61 .  
         [0057]     Referring to  FIG. 2D , the nanoparticles  61  are deposited on the silicon source layer  50 , thereby forming a nanoparticle layer  60 . The nanoparticles  61  may be obtained by performing laser ablation on the target formed of Au and silicon.  
         [0058]     Referring to  FIG. 2E , the nanoparticles  61  are grown. The growth size of the nanoparticles  61  may be determined according to a thickness of the silicon source layer  50 .  
         [0059]     In an embodiment of the present invention, the size of the nanoparticles  61  can be adjusted by adjusting the thickness of the silicon source layer  50 . In addition, since the substrate  30  and the nanoparticles  61  are isolated by the insulating layer  40  from each other, the nanoparticles  61  can be applied to a variety of devices.  
         [0060]     As described above, in the nanoparticle structure and the method of manufacturing the nanoparticle structure according to the present disclosure, the size of nanoparticles can be adjusted by adjusting the thickness of the silicon source layer such that nanoparticles having a desired size can be easily obtained.  
         [0061]     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 following claims.