[0001]    This application is a continuation application claiming priority to Ser. No. 11/870,551, filed Oct. 11, 2007. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to material compositions and methods for forming metal contacts in semiconductor materials. 
       BACKGROUND OF THE INVENTION 
       [0003]    As via sizes in semiconductor manufacturing reduces in scale with the technology node, the demand for smaller contact structures has increased. Tungsten may provide sufficient contact metallurgy down to about 45 nanometers (nm), where modeling has suggested copper may be used for the 32 nm mode since the resistively of plated copper may be significantly lower than chemical vapor deposited tungsten. However as the dimension of the via/line continues to reduce, surface and grain boundary scattering of electron and phonon in copper may significantly increase. There exists a need for a contact structure which offers reduced electrical resistance. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention relates to a method of forming contact structures, comprising: 
         [0005]    depositing a silicide layer onto a substrate, said silicide layer having a first surface; 
         [0006]    depositing an electrically insulating layer over said first surface of said silicide layer, said insulating layer having a second surface; 
         [0007]    forming a via through said insulating layer, said via having a bottom defined by a portion of said first surface, wherein said via extends from said second surface to said first surface, wherein said forming exposes said portion of said first surface, said via having at least one vertical wall; 
         [0008]    depositing an electrically conductive layer onto said second surface and inside said via, wherein said conductive layer covers said bottom of said via and said at least one vertical wall of said via; 
         [0009]    removing said conductive layer from said second surface and said bottom of said via, said conductive layer remaining on said at least one vertical wall of said via, resulting in said portion of said silicide being exposed; and 
         [0010]    filling said via with aluminum, said aluminum directly contacting said first surface of said silicide layer. 
         [0011]    The present invention relates to a layered structure, comprising: 
         [0012]    a silicide layer disposed on a first surface of a substrate, said silicide layer having a second surface; 
         [0013]    an electrically insulating layer disposed over said second surface of said silicide layer, said insulating layer having a third surface; 
         [0014]    an aluminum plug extending from said third surface through said electrically insulating layer to said second surface, wherein said plug directly contacts said silicide layer; and 
         [0015]    an electrically conductive layer disposed between said aluminum plug and said insulating layer. 
         [0016]    The present invention relates to a method for forming a contact structure, comprising: 
         [0017]    providing a substrate, said substrate having an electrically insulating layer disposed thereon, said electrically insulating layer having a first surface, wherein said electrically insulating layer comprises at least one trench disposed thereon and extending from said first surface to a bottom of said at least one trench, said at least one trench defined by at least one sidewall and said bottom, said bottom having a silicide layer disposed thereon; 
         [0018]    depositing an electrically conductive layer into said at least one trench, said conductive layer adhering to said silicide layer, said at least one sidewall of said at least one trench, and said first surface; 
         [0019]    etching selectively said electrically conductive layer from said silicide layer and said first surface; and 
         [0020]    depositing aluminum into said at least one trench, wherein responsive to said depositing, an aluminum layer grows selectively from said silicide layer and said at least one sidewall, said aluminum in direct contact with said silicide layer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The features of the invention are set forth in the appended claims. The invention itself, however, will be best understood by reference to the following detailed description of illustrative embodiments when read in conjunction with the accompanying drawings. 
           [0022]      FIG. 1A  is an illustration of a cross-section of a substrate  105 , in accordance with embodiments of the present invention. 
           [0023]      FIG. 1B  is an illustration of the substrate of  FIG. 1A  where a silicide layer has been deposited onto a surface of the substrate, in accordance with embodiments of the present invention. 
           [0024]      FIG. 1C  is an illustration of the substrate and silicide layer of  FIG. 1B  where an electrically insulating layer has been deposited over the surface of the silicide layer, in accordance with embodiments of the present invention. 
           [0025]      FIG. 1D  is an illustration of the layers in  FIG. 1C  where a via has been formed through the insulating layer, in accordance with embodiments of the present invention. 
           [0026]      FIG. 1E  is an illustration of the layered structure of  FIG. 1D  where an electrically conductive layer has been deposited onto the surface of the electrically insulating layer and inside the via, in accordance with embodiments of the present invention. 
           [0027]      FIG. 1F  is an illustration of the structure of  FIG. 1E  where the electrically conductive layer has been substantially and selectively removed, in accordance with embodiments of the present invention. 
           [0028]      FIG. 1G  is an illustration of a layered structure which may be formed by filling the via of  FIG. 1F , in accordance with embodiments of the present invention. 
           [0029]      FIG. 2  is a flow chart illustrating steps for a method of forming contact structures, in accordance with embodiments of the present invention. 
           [0030]      FIG. 3A  is an illustration of a substrate having an electrically insulating layer disposed thereon, in accordance with embodiments of the present invention. 
           [0031]      FIG. 3B  is an illustration of an electrically conductive layer deposited into the at least one trench of  FIG. 3A , in accordance with embodiments of the present invention. 
           [0032]      FIG. 3C  is an illustration of the electrically conductive layer of  FIG. 3B  after it has been selectively etched from the silicide layer and the surface of the insulating layer, in accordance with embodiments of the present invention. 
           [0033]      FIG. 3D  is an illustration of  FIG. 3C  after depositing aluminum into the at least one trench, in accordance with embodiments of the present invention. 
           [0034]      FIG. 4  is a flow chart illustrating a method for forming a contact structure, in accordance with embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0035]    Although certain embodiments of the present invention will be shown and described in detail, it should be understood that various changes and modifications may be made without departing from the scope of the appended claims. The scope of the present invention will in no way be limited to the number of constituting components, the materials thereof, the shapes thereof, the relative arrangement thereof, etc., and are disclosed simply as examples of embodiments. The features and advantages of the present invention are illustrated in detail in the accompanying drawings, wherein like reference numerals refer to like elements throughout the drawings. Although the drawings are intended to illustrate the present invention, the drawings are not necessarily drawn to scale. 
         [0036]      FIG. 1A  is an illustration of a cross-section of a substrate  105 . The substrate  105  may comprise multiple layers such as layers  106  and  107  shown in the example illustrated in  FIG. 1A , or the substrate may comprise a single layer. The substrate  105  may include a semiconducting material, an insulating material, a conductive material or any combination thereof, including multilayered structures. Thus, for example, substrate  105  may be a semiconducting material such as Si, SiGe, SiGeC, SiC, GaAs, InAs, InP and other III/V or II/VI compound semiconductors. The substrate  105  may be, for example, a silicon wafer or process wafer such as that produced in various steps of a semiconductor manufacturing process, such as an integrated semiconductor wafer. The substrate  105  may be a layered substrate such as, for example, Si/SiGe, Si/SiC, silicon-on-insulators (SOIs) or silicon germanium-on-insulators (SGOIs). The substrate  105  may comprise layers such as a dielectric layer, a barrier layer for copper such as SiC, a metal layer such as copper, a silicon layer, a silicon oxide layer, the like, or combinations thereof. The substrate  105  may comprise an insulating material such as an organic insulator, an inorganic insulator or a combination thereof including multilayers. The substrate  105  may comprise a conductive material, for example, polycrystalline silicon (polySi), an elemental metal, alloys of elemental metals, a metal silicide, a metal nitride, or combinations thereof, including multilayers. The substrate may comprise ion implanted areas, such as ion implanted source/drain areas having P-type or N-type diffusions active to the surface of the substrate. 
         [0037]    In some embodiments, the substrate  105  may include a combination of a semiconducting material and an insulating material, a combination of a semiconducting material and a conductive material or a combination of a semiconducting material, an insulating material and a conductive material. An example of a substrate that includes a combination of the above is an interconnect structure. 
         [0038]      FIG. 1B  is an illustration of the substrate  105  of  FIG. 1A  where a silicide layer  110  has been deposited onto a surface of the substrate  105 . The silicide layer  110  may comprise a material such as NiPt, NiPtRe, NiSi, CoSi 2 , YtSi, ErSi, TiSi 2 , tungsten silicides, or combinations thereof. 
         [0039]      FIG. 1C  is an illustration of the substrate  105  and silicide layer  110  of  FIG. 1B  where an electrically insulating layer  115  has been deposited over the surface of the silicide layer  110 , where the insulating layer has a surface  145 . The electrically insulating layer  115  may, for example, comprise a dielectric layer such as a carbon-doped oxide dielectric material comprising Si, C, O, and H, undoped silicate glass (USG), a stress liner such as a compressive or tensile nitride of silicon, or combinations thereof. 
         [0040]      FIG. 1D  is an illustration of the layers in  FIG. 1C  where a via  130  has been formed through the insulating layer  115 . The via  130  may extend from the surface  145  of the insulating layer  115  to the surface of the silicide layer  110 . The via  130  may have a bottom  117  defined by an exposed portion of the surface of the silicide layer  110  and may have at least one substantially vertical wall  140 . The via  130  may be formed by processes such as wet etching, dry etching, reactive ion etching, photolithography, and similar processes known to those skilled in the art. 
         [0041]      FIG. 1E  is an illustration of the layered structure of  FIG. 1D  where an electrically conductive layer  120  has been deposited onto the surface  145  of the electrically insulating layer  115  and inside the via  130 . The electrically conductive layer  120  may substantially cover the bottom  117  of the via  130  and substantially cover the at least one vertical sidewall  140  of the via  130 . 
         [0042]    The electrically conductive layer  120  may be deposited using processes such as atomic layer deposition (ALD), chemical vapor deposition (CVD), or a combination of these processes. The electrically conductive layer may comprise conductive materials such as titanium nitride, ruthenium, or a combination thereof. 
         [0043]      FIG. 1F  is an illustration of the structure of  FIG. 1E  where the electrically conductive layer  120  has been substantially and selectively removed from the surface  145  of the electrically insulating layer  115  and from the portion of the surface of the silicide layer  110  at the bottom  117  of the via  130 , where the portion of the silicide layer  110  at the bottom  117  may be exposed after the removing. The electrically conductive layer  120  may remain on the at least one side wall ( 140  in  FIG. 1D ) after the removing. 
         [0044]    The electrically conductive layer  120  may be selectively removed using processes such as sputtering, for example argon sputtering. Removing the electrically conducting layer  120  may comprise etching selectively the electrically conductive layer  120  from the silicide layer  110  and from the surface  145  of the electrically insulating layer  115 . Those skilled in the art will recognize other removal methods which may selectively remove the electrically conductive layer  120  from the surface  145  and the portion of silicide layer  110  at the bottom  117  of the via  130 , where such methods are intended to be included within the scope of the present invention. 
         [0045]      FIG. 1G  is an illustration of a layered structure  100  which may be formed by filling the via  130  of  FIG. 1F . The via  130  of FIG. F may be filled with aluminum forming an aluminum plug  125  or column, where the aluminum plug  125  may directly contact the portion of the surface of the silicide layer  110  defining the bottom  117  of the via  130 . At film thicknesses of 25 nm, the electrical resistivity of aluminum is approximately equivalent to that of copper, whereas for films thinner than about 25 nm the resistivity of aluminum is significantly lower than that of copper. For example, calculated electrical resistivities of 5 nm films of copper and aluminum are approximately 14.96 μΩ-cm and 10.69 μΩ-cm, respectively. Thus, the contact structures described herein using aluminum provides superior conductivity over analogous copper structures. In addition, a structure employing a barrier layer or liner disposed between the aluminum plug  125  and the silicide layer  110  would suffer from increased electrical resistance due to the added layer and interfacial resistance 
         [0046]    The layered structure  100  may comprise the silicide layer  110  disposed on the surface of the substrate  105 , the electrically insulating layer  115  having a surface  145  and being disposed over the surface of the silicide layer  110 , an aluminum plug  125  extending from the surface  145  of the electrically insulating layer  115  through the electrically insulating layer  115  to the surface of the silicide layer  110 , where the plug  125  may directly contact the silicide layer  110 , and an electrically conductive layer  120  disposed between the aluminum plug  125  and the electrically insulating layer  115 . 
         [0047]    Filling the via  130  may comprise a process such as chemical vapor deposition, physical vapor deposition, or a combination of these. For example, the via  130  may be filled by chemical vapor deposition of dimethylaluminum hydride, methylpyrroridine alane, or a combination thereof. 
         [0048]      FIG. 2  is a flow chart illustrating steps for a method of forming contact structures. In step  200  a silicide layer is deposited onto a substrate. The substrate may be as that described above and illustrated in  FIG. 1A , for example. The silicide layer may comprise a material such as NiPt, NiPtRe, NiSi, CoSi 2 , YtSi, ErSi, TiSi 2 , tungsten silicides, or combinations thereof, such as that described above and illustrated in  FIGS. 1B ,  1 C,  1 D,  1 E,  1 F, and  1 G. 
         [0049]    In step  205  an electrically insulating layer is deposited on a surface of the silicide layer deposited in step  200 , such as is described above and illustrated in  FIGS. 1C ,  1 D,  1 E,  1 F, and  1 G. 
         [0050]    In step  210 , a via is formed through the insulating layer. The via may extend from the surface of the electrically insulating layer to the surface of the silicide layer, such as that illustrated in  FIGS. 1D ,  1 E, and  1 F. Forming the via may expose a portion of the surface of the silicide layer, where the via may have a bottom defined by the exposed portion of the surface of the silicide layer. The via may have at least one vertical sidewall. 
         [0051]    In step  215 , an electrically conductive layer is deposited onto the surface of the electrically insulating layer and inside the via formed in step  210 , such as that illustrated in  FIG. 1E  and as described above. The electrically conductive layer may conformally and substantially cover the surface of the electrically insulating layer, the at least one side wall of the via and the bottom of the via. 
         [0052]    In step  220 , the conductive layer is selectively removed from the bottom of the via and from the surface of the insulating layer, such as described above and illustrated in  FIG. 1F . The conductive layer may remain on the at least one sidewalls after the conductive layer is removed from the bottom of the via and the surface of the insulating layer. Removing the conductive layer from the bottom of the via may expose a surface of the silicide layer. 
         [0053]    In step  225 , the via is filled with aluminum where the aluminum may directly contact the surface of the silicide layer on the bottom of the via. The via may be filled using methods described above and illustrated in  FIG. 1G . 
         [0054]      FIG. 3A  is an illustration of a substrate  105  having an electrically insulating layer  115  disposed thereon. The substrate  115  may comprise materials described above and may comprise a plurality of layers such as layers  106  and  107  illustrated in the example of  FIG. 3A , or the substrate  105  may comprise a single layer. The electrically insulating layer  115  may have a surface  145  and at least one trench  400 , where the trench  400  may extend from the surface  145  of the insulating layer  115  to a bottom having a silicide layer  110  disposed thereon. The trench  400  may be defined by at least one sidewall  405  and the bottom having the silicide layer  110 . 
         [0055]      FIG. 3B  is an illustration of an electrically conductive layer  120  deposited into the at least one trench  400  of  FIG. 3A . The electrically conductive layer  120  may adhere to the silicide layer  110 , the at least one sidewall  405 , and the surface  145  of the insulating layer  115 . 
         [0056]      FIG. 3C  is an illustration of the electrically conductive layer  120  of  FIG. 3B  after it has been selectively etched from the silicide layer  110  and the surface of the insulating layer  115 . 
         [0057]      FIG. 3D  is an illustration of  FIG. 3C  after depositing aluminum  410  into the at least one trench  400 . As the aluminum  410  is deposited into the trench  400 , an aluminum layer may selectively grow from the electrically conductive layer  120  on the at least one sidewall  405  of the trench  400  and from the silicide layer  110  on the bottom of the trench  400 . The aluminum  410  may be in direct contact with the silicide layer  110 . 
         [0058]      FIG. 4  is a flow chart illustrating a method for forming a contact structure. Step  400  provides a substrate, such as that described above and illustrated in  FIG. 3A  and  FIG. 1D . The substrate may have an electrically insulating layer disposed thereon. The electrically insulating layer may have a surface and at least one trench, where the trench may extend from the surface of the insulating layer to a bottom having a silicide layer disposed thereon. The trench may be defined by at least one sidewall and the bottom having the silicide layer. 
         [0059]    In step  405 , an electrically conductive layer is deposited into the at least one trench, where the conductive layer may adhere to the silicide layer, the at least one side wall of the trench, and to the surface of the electrically insulating layer, such as the examples illustrated in  FIG. 1E  and  FIG. 3B . 
         [0060]    In step  410 , the electrically conductively layer may be selectively etched from the silicide layer and the surface of the electrically insulating layer, where the surface of the silicide layer may be exposed after the selective etching. The etching may be a dry etching process such as plasma etching, plasma sputtering, reactive ion etching, combinations of theses, and the like. The electrically conductive layer may remain on the at least one side wall of the at least one trench after the selective etching, such as the examples illustrated in  FIG. 1F  and  FIG. 3C . 
         [0061]    In step  415 , aluminum is deposited into the at least one trench. As the aluminum is deposited, an aluminum layer may grow selectively from the electrically conductive layer on the at least one sidewall and from the silicide layer on the bottom of the at least one trench. The aluminum may be in direct contact with the silicide layer, such as is illustrated in the examples in  FIG. 1G  and  FIG. 3D . The electrically conductive layer and the silicide layer may provide preferred nucleation sites for the aluminum. For example, the substrate may be a semiconductor process wafer, where after aluminum deposition in a trench and selective film growth, the wafer may not require additional chemical mechanical polishing since aluminum may not form on the electrically insulating surface. In addition, hot reflow of aluminum may not be required since the aluminum deposition may substantially fill the trench. 
         [0062]    The foregoing description of the embodiments of this invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously, many modifications and variations are possible. Such modifications and variations that may be apparent to a person skilled in the art are intended to be included within the scope of this invention as defined by the accompanying claims.
A contact structure and a method of forming the contact structure. The structure includes: a silicide layer on and in direct physical contact with a top substrate surface of a substrate; an electrically insulating layer on the substrate; and an aluminum plug within the insulating layer. The aluminum plug has a thickness not exceeding 25 nanometers in a direction perpendicular to the top substrate surface. The aluminum plug extends from a top surface of the silicide layer to a top surface of the insulating layer. The aluminum plug is in direct physical contact with the top surface of the silicide layer and is in direct physical contact with the silicide layer. The method includes: forming the silicide layer on and in direct physical contact with the top substrate surface of the substrate; forming the electrically insulating layer on the substrate; and forming the aluminum plug within the insulating layer.