Patent Document

CROSS REFERENCE 
       [0001]    The present application is a divisional of and claims priority under 35 U.S.C. §120 of U.S. patent application Ser. No. 13/525,823, titled IMPROVED SIDEWALLS OF ELECTROPLATED COPPER INTERCONNECTS, filed on Jun. 18, 2012, which is incorporated by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The present invention generally relates to integrated circuits, and more particularly to electroplating copper interconnects. 
         [0004]    2. Background of Invention 
         [0005]    Advancements in the area of semiconductor fabrication have enabled the manufacturing of integrated circuits that have a high density of electronic components. The length and number of interconnect wiring increases in high density integrated circuits. Three-dimensional (3D) stacking of integrated circuits has been created to address these challenges. Fabrication of 3D integrated circuits includes at least two silicon chips stacked vertically. Vertically stacked chips can reduce interconnect wiring length and increase device density. Deep through-substrate vias (TSVs) can provide interconnections and electrical connectivity between the electronic components of the vertically stacked chips. Such vias may require high aspect ratios, where the via height is large with respect to the via width, to save valuable area on the silicon substrate. TSVs enable increased device density while reducing the total length of interconnect wiring. 
         [0006]    However, fabrication techniques such as chemical vapor deposition (CVD) are unable to fill high aspect ratio TSVs without the risk of pinch-off. Pinch-off refers to build up of deposited material at an opening of a trench or a via hole (e.g., TSV). Pinch-off can result in the formation of voids, where some volume of a trench or a via hole (e.g., TSV) remain unfilled with the deposited material. Void formation can reduce the conductive cross section and if large enough may constitute a short and sever the interconnect structure. Thus, void formation can reduce integrated circuit performance, decrease reliability of interconnects, cause sudden data loss, and reduce the useful life of semiconductor integrated circuit products. In addition, pinch-off can result in undesired process chemicals to be trapped within a trench or a via hole (e.g., TSV). 
         [0007]    An alternative technique for filling TSVs with conductive material may include electroplating. Electroplating techniques require a cathode. IF the part to be plated is conductive, it can serve as the cathode. The cathode can be connected to a negative terminal of an external power supply and thus must be electrically conductive. A seed layer can be deposited to serve as the cathode. For example, a copper film may be deposited using physical vapor deposition or other known deposition techniques to form the requisite cathode, or seed layer, in preparation for electroplating. When electroplating a trench or via hole an electrical potential is applied to the cathode while the structure is exposed to an electrolyte solution where the desired plating material can plate out onto the cathode. However, in high aspect ratio features, the risk of pinch-off remains because the deposition on sidewalls and bottom can proceed roughly at the same rate, so the feature closes from the sides before fully filling from the bottom (this tendency is exacerbated by mass transfer limitations at the remote end of a deep feature). 
         [0008]    Accordingly, current fabrication techniques for filling high aspect ratio TSVs with a conductive material show risks and disadvantages. Despite achievements that have been made in 3D integrated circuit technology, to increase device density and reduce the length of interconnection wiring, the challenge of fabricating and filling high aspect ratio TSVs without void formation and chemical entrapment continues to persist. 
       SUMMARY 
       [0009]    According one embodiment of the present invention, a structure formed in an opening, the opening having a substantially vertical sidewall defined by a non-metallic material and having a substantially horizontal bottom defined by a conductive pad, the structure comprising a diffusion barrier covering the sidewall and a fill composed of conductive material is provided. The structure may include a first intermetallic compound separating the diffusion barrier from the conductive material, wherein the first intermetallic compound comprises an alloying material and the conductive material, and is mechanically bound to the conductive material, wherein the alloying material is at least one of the materials selected from the group consisting of chromium, tin, nickel, magnesium, cobalt, aluminum, manganese, titanium, zirconium, indium, palladium, and silver; and a first high friction interface located between the diffusion barrier and the first intermetallic compound and parallel to the sidewall of the opening, wherein the first high friction interface results in a mechanical bond between the diffusion barrier and the first intermetallic compound. 
         [0010]    According another exemplary embodiment, structure formed in an opening, the opening having a substantially vertical sidewall defined by a non-metallic material and having a substantially horizontal bottom defined by the non-metallic material, the structure comprising a diffusion barrier covering the sidewall and bottom, and a fill composed of conductive material is provided. The structure may include a seed layer located directly on top of and conformal to the diffusion barrier, wherein the seed layer is parallel to the sidewall and bottom of the opening; a first intermetallic compound separating the seed layer and the conductive material and parallel to the sidewall of the opening, wherein the first intermetallic compound comprises an alloying material and the conductive material, and is mechanically bound to the conductive material, wherein the alloying material is at least one of the materials selected from the group consisting of chromium, tin, nickel, magnesium, cobalt, aluminum, manganese, titanium, zirconium, indium, palladium, and silver; and a first high friction interface located between the seed layer and the first intermetallic compound and parallel to the sidewall of the opening, wherein the first high friction interface results in a mechanical bond between the seed layer and the first intermetallic compound. 
         [0011]    According another exemplary embodiment, a method of plating a structure comprising an opening etched in a nonmetallic material, a diffusion barrier deposited along a sidewall of the opening, and a conductive pad located at a bottom of the opening is provided. The method may include depositing an alloying material on top of the diffusion barrier, wherein the alloying material comprises an incorrect crystalline structure to serve as a seed for plating the conductive material, exposing the opening to an electroplating solution comprising the conductive material, and applying an electrical potential to the conductive pad causing the conductive material to deposit from the electroplating solution onto the conductive pad and causing the opening to fill with the conductive material. The method may further include forming a first intermetallic compound along an intersection of the alloying material and the conductive material, the first intermetallic compound comprising the alloying material and the conductive material, 
         [0012]    According another exemplary embodiment, a method of plating a structure comprising an opening etched in a nonmetallic material and a diffusion barrier deposited along a sidewall and along a bottom of the opening is provided. The method may include depositing a seed layer along the sidewall and the bottom of the opening, wherein the seed layer comprises a correct crystalline structure to seed copper, depositing an alloying material on top of the diffusion barrier and parallel to the sidewall of the opening, wherein the alloying material comprises an incorrect crystalline structure to serve as a seed for plating the conductive material, and exposing the opening to an electroplating solution comprising the conductive material. The method may further include applying an electrical potential to the seed layer causing the conductive material to deposit from the electroplating solution onto the seed layer exposed at the bottom of the opening and causing the opening to fill with the conductive material, and forming a first intermetallic compound along an intersection between the alloying material and the conductive material, the first intermetallic compound comprising the alloying material and the conductive material. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0013]    The following detailed description, given by way of example and not intend to limit the disclosure solely thereto, will best be appreciated in conjunction with the accompanying drawings, in which: 
           [0014]      FIGS. 1A-1D  illustrate the steps of a method of forming a copper interconnect structure according to one embodiment. 
           [0015]      FIG. 1A  illustrates a step in the formation of a copper interconnect structure according to one embodiment. 
           [0016]      FIG. 1B  illustrates a step in the formation of a copper interconnect structure according to one embodiment. 
           [0017]      FIG. 1C  illustrates a step in the formation of a copper interconnect structure according to one embodiment. 
           [0018]      FIG. 1D  illustrates a step in the formation of a copper interconnect structure according to one embodiment. 
           [0019]      FIG. 2  illustrates a copper interconnect structure according to one embodiment. 
           [0020]      FIG. 3  illustrates a copper interconnect structure according to one embodiment. 
           [0021]      FIG. 4  illustrates a copper interconnect structure according to one embodiment. 
           [0022]      FIG. 5  illustrates a copper interconnect structure according to one embodiment. 
           [0023]      FIG. 6  illustrates a copper interconnect structure according to one embodiment. 
           [0024]      FIG. 7A-7E  illustrate the steps of a method of forming a copper interconnect structure according to one embodiment. 
           [0025]      FIG. 7A  illustrates a step in the formation of a copper interconnect structure according to one embodiment. 
           [0026]      FIG. 7B  illustrates a step in the formation of a copper interconnect structure according to one embodiment. 
           [0027]      FIG. 7C  illustrates a step in the formation of a copper interconnect structure according to one embodiment. 
           [0028]      FIG. 7D  illustrates a step in the formation of a copper interconnect structure according to one embodiment. 
           [0029]      FIG. 7E  illustrates a step in the formation of a copper interconnect structure according to one embodiment. 
           [0030]      FIG. 8  illustrates a copper interconnect structure according to one embodiment. 
           [0031]      FIG. 9  illustrates a copper interconnect structure according to one embodiment. 
           [0032]      FIG. 10  illustrates a copper interconnect structure according to one embodiment. 
           [0033]      FIG. 11  illustrates a copper interconnect structure according to one embodiment. 
           [0034]      FIG. 12  illustrates a copper interconnect structure according to one embodiment. 
       
    
    
       [0035]    The drawings are not necessarily to scale. The drawings are merely schematic representations, not intended to portray specific parameters of the invention. The drawings are intended to depict only typical embodiments of the invention. In the drawings, like numbering represents like elements. 
       DETAILED DESCRIPTION 
       [0036]    Detailed embodiments of the claimed structures and methods are disclosed herein; however, it is understood that the disclosed embodiments are merely illustrative of the claimed structures and methods that may be embodied in various forms. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiment set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of this disclosure to those skilled in the art. In the description, details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the presented embodiments. 
         [0037]    Referring to  FIGS. 1A-1D , multiple steps of a method of forming an interconnect structure are shown. Now referring to  FIG. 1A , a cross-sectional view of an interconnect structure  100  having an opening  106  in a nonmetallic material  102  and a conductive pad  104  positioned at a bottom  108  of the opening  106  is shown. The interconnect structure  100  may include lines, wires, vias or through-substrate vias (TSVs). In one embodiment, the nonmetallic material  102  may be made from any of several known semiconductor materials such as, for example, silicon (e.g. a bulk silicon substrate), germanium, silicon-germanium alloy, silicon carbide, silicon-germanium carbide alloy, and compound (e.g. III-V and II-VI) semiconductor materials. In one embodiment, the nonmetallic material  102  may be made from any dielectric material know to a person having ordinary skill in the art. The conductive pad  104  itself may include a line, a wire or a via. Alternatively, the interconnect structure  100  may include a trench formed in the nonmetallic material  102  without the conductive pad  104 , as described below (see  FIGS. 7A-7E ,  8 - 12 ). An optional electrically insulating liner  110  (not shown) may be deposited along a sidewall  109  of the opening  106  and on top of the nonmetallic material  102 . 
         [0038]    Now referring to  FIG. 1B , a diffusion barrier  112  may be deposited along the sidewall  109  of the opening  106  and on top of the nonmetallic material  102 . The diffusion barrier  112  may be deposited only on the nonmetallic material  102  and not on the conductive pad  104 . The diffusion barrier  112  may include any material that which prohibits contamination of a copper material by the nonmetallic material  102 . In one embodiment, the diffusion barrier  112  may be made from a material including tantalum nitride deposited by physical vapor deposition (PVD). In one embodiment, the diffusion barrier  112  may be deposited by an alternative deposition technique, for example chemical vapor deposition (CVD) or atomic layer deposition (ALD). 
         [0039]    Now referring to  FIG. 1C , an alloying material  114  may be deposited on top of the diffusion barrier  112 . In one embodiment, the alloying material  114  may be deposited only on the diffusion barrier  112  and not on the conductive pad  104 . In one embodiment, the alloying material  114  may be made from a material including chromium deposited in a vacuum using a sputter deposition technique. In one embodiment, the alloying material  114  may be made from a material including chromium, copper, nickel, tin, magnesium, cobalt, aluminum, manganese, titanium, zirconium, indium, palladium, gold, or some combination thereof. The alloying material  114  may not have the correct crystalline structure to serve as a seed for copper plating. In other words, the crystal face orientation of the alloying material  114  may not mimic the crystal face orientation of copper; such that the surface of the alloying material  114  will not allow copper to grow from the its face. For example, Cr has a BCC (Body Centered Cubic) lattice whereas Cu has an FCC (Face Centered Cubic) lattice. These two lattice structures are inherently incompatible, i.e. Cr cannot act as a seed for Cu plating. 
         [0040]    In one embodiment, an optional adhesive liner such as gold (not shown) may be used prior to depositing the alloying material  114 . The alloying material  114  may have a thickness ranging from about 50 angstroms to about 300 angstroms. 
         [0041]    In one embodiment, the diffusion barrier  112  and the alloying material  114  may be deposited on the sidewall  109  and the bottom  108  of the opening  106 . In such embodiments, the diffusion barrier  112  and the alloying material  114  may be subsequently removed from the bottom  108  of the opening  106 . For example, an anisotropic etch may be used to remove the diffusion barrier  112  and the alloying material  114  from the bottom  108  to expose the conductive pad  104  without removing the diffusion barrier  112  and the alloying material  114  from the sidewall  109  of the opening  106 . This anisotropic etch may be performed after all layers are deposited or immediately following the deposition of each layer. 
         [0042]    Now referring to  FIG. 1D , a copper material  116  may be deposited on the conductive pad  104  within the opening  106  (shown in  FIG. 1C ) using an electroplating technique. The conductive pad  104  may serve as a cathode to which an electrical potential is applied during the electroplating technique. Specifically, a negative voltage may be applied to the conductive pad  104 . The conductive pad  104  may also serve as a copper seed. Because the specific alloying material  114  chosen may not have the correct crystalline structure to serve as a seed for copper plating, a bottom-up plating technique, free of voiding or pinch-off, may therefore be achieved. The bottom-up plating technique results in filling the opening  106  (shown in  FIG. 1C ) with the copper material  116 . After the electroplating technique a chemical mechanical polishing (CMP) technique may be used to remove excess copper from the surface of the substrate. The CMP technique can remove the diffusion barrier  112 , the alloying material  114 , and excess copper material  116  selective to the top surface of the nonmetallic material  102 . 
         [0043]    The alloying material  114  may be used to form a mechanical bond between the copper material  116  and the sidewall  109  of the opening  106 . The mechanical bond can be created either by forming an intermetallic compound or by creating a high friction interface caused by an extremely close contact between layers. Extremely close contact may be defined as maximizing interfacial surface contact while minimizing foreign contaminants between two layers. The mechanical bond may be created at an intersection  124  or an intersection  126 . Lack of a mechanical bond between the copper material  116  and the sidewall  109  of the opening  106  may result in a pistoning effect where the copper material  116  moves vertically within the opening  106  during thermal cycling due to copper&#39;s relatively high coefficient of thermal expansion in comparison to surrounding semiconductor materials (e.g. silicon, silicon oxides, and silicon nitrides). Thermal expansion and contraction is inevitable when building or operating integrated circuits. Pistoning of the copper material  116  may impose stress and strain on corresponding components that may be connected to the copper material  116  and over time will cause a failure in these connections. 
         [0044]    Referring to  FIGS. 2-6 , multiple different embodiments of the interconnect structure  100  are shown. Now referring to  FIG. 2 , one embodiment of the interconnect structure  100  is shown. A first interaction may occur between the alloying material  114  (shown in  FIG. 1D ) and the copper material  116  at the intersection  124  (shown in  FIG. 1D ). The first interaction may produce a first intermetallic compound  118  formed from the alloying material  114  (shown in  FIG. 1D ) and the copper material  116  at the intersection  124  (shown in  FIG. 1D ). The first intermetallic compound  118  may include the alloying material  114  (shown in  FIG. 1D ) and the copper material  116 . The first intermetallic compound  118  can form a mechanical bond between the alloying material  114  (shown in  FIG. 1D ) and the copper material  116 . The first intermetallic compound  118  may be formed either simultaneously while plating the copper material  116  or any time thereafter, for example during a subsequent annealing process. 
         [0045]    Formation of the intermetallic compound  118  between the alloying material  114  (shown in  FIG. 1D ) and the copper material  116  may occur when favorable thermodynamic and kinetic conditions exist for the compounds to form as a precipitate within a solid solution of the two materials, in this case the alloying material  114  (shown in  FIG. 1D ) and the copper material  116 . Intermetallic compounds may be stoichiometric or non-stoichiometric. For example, Ag 3 Sn is an intermetallic compound that may form when Ag and Sn are in a solid solution. 
         [0046]    A second interaction may occur between the diffusion barrier  112  and the alloying material  114  (shown in  FIG. 1D ) at the intersection  126  (shown in  FIG. 1D ). The second interaction may involve extremely close contact between the diffusion barrier  112  and the alloying material  114  (shown in  FIG. 1D ) at the intersection  126  (shown in  FIG. 1D ). Extremely close contact may create an area of high friction which may result in a mechanical bond between the diffusion barrier  112  and the alloying material  114  (shown in  FIG. 1D ). In one embodiment, extremely close contact may be achieved by depositing one material on top of another material in a vacuum using a sputter deposition technique. If one material is deposited on another material with either vacuum interruption or via an aqueous system, the possibility for extremely close contact is significantly diminished by native oxides or third body interference films, e.g. water may be present between the interfaces. The alloying material  114  (shown in  FIG. 1D ) may be deposited on top of the diffusion barrier  112  in a vacuum using the sputter deposition technique, and resulting in extremely close contact. 
         [0047]    With continued reference to  FIG. 2 , the diffusion barrier  112  may be deposited with uniform, or near uniform, thickness. The first intermetallic compound  118  may have a non-uniform thickness and can mechanically join the alloying material  114  (shown in  FIG. 1D ) with the copper material  116 . Formation of the first intermetallic compound  118  may consume all or some of the alloying material  114  (shown in  FIG. 1D ). In one embodiment, the alloying material  114  (shown in  FIG. 1D ) is entirely consumed by the formation of the first intermetallic compound  118 , as shown in  FIG. 2 . The mechanical bond created by the first intermetallic compound  118  and extremely close contact between the diffusion barrier  112  and the alloying material  114  (shown in  FIG. 1D ) can minimize the pistoning effect described above. The integrity of chip interconnects can be greatly improved by minimizing the pistoning effect because of the reduced risk of interconnect failure due to thermal expansion and contraction. 
         [0048]    Now referring to  FIG. 3 , one embodiment of the interconnect structure  100  is shown. A first interaction may occur between the alloying material  114  and the copper material  116  at the intersection  124  (shown in  FIG. 1D ). The first interaction may produce the first intermetallic compound  118  formed from the alloying material  114  and the copper material  116  at the intersection  124  (shown in  FIG. 1D ). The first intermetallic compound  118  may include the alloying material  114  and the copper material  116 . The first intermetallic compound  118  can form a mechanical bond between the alloying material  114  and the copper material  116 . The first intermetallic compound  118  may be formed either simultaneously while plating the copper material  116  or any time thereafter, for example during a subsequent annealing process. 
         [0049]    A second interaction may occur between the diffusion barrier  112  and the alloying material  114  at the intersection  126 . The second interaction may involve extremely close contact between the diffusion barrier  112  and the alloying material  114  at the intersection  126 . Extremely close contact may create an area of high friction which may result in a mechanical bond between the diffusion barrier  112  and the alloying material  114 . 
         [0050]    With continued reference to  FIG. 3 , the diffusion barrier  112  may be deposited with uniform, or near uniform, thickness. The first intermetallic compound  118  may have a non-uniform thickness and can mechanically join the alloying material  114  with the copper material  116 . Formation of the first intermetallic compound  118  may consume all or some of the alloying material  114 . In one embodiment, the alloying material  114  is not entirely consumed by the formation of the first intermetallic compound  118  such that some of the alloying material  114  remains between the first intermetallic compound  118  and the diffusion barrier  112 , as shown in  FIG. 3 . The mechanical bond created by the first intermetallic compound  118  and extremely close contact between the diffusion barrier  112  and the alloying material  114  can minimize the pistoning effect described above. The integrity of chip interconnects can be greatly improved by minimizing the pistoning effect because of the reduced risk of interconnect failure due to thermal expansion and contraction. 
         [0051]    Now referring to  FIG. 4 , one embodiment of the interconnect structure  100  is shown. A first interaction may occur between the alloying material  114  (shown in  FIG. 1D ) and the copper material  116  at the intersection  124  (shown in  FIG. 1D ). The first interaction may produce the first intermetallic compound  118  formed from the alloying material  114  (shown in  FIG. 1D ) and the copper material  116  at the intersection  124  (shown in  FIG. 1D ). The first intermetallic compound  118  may include the alloying material  114  (shown in  FIG. 1D ) and the copper material  116 . The first intermetallic compound  118  can form a mechanical bond between the alloying material  114  (shown in  FIG. 1D ) and the copper material  116 . The first intermetallic compound  118  may be formed either simultaneously while plating the copper material  116  or any time thereafter, for example during a subsequent annealing process. 
         [0052]    A second interaction may occur between the diffusion barrier  112  and the alloying material  114  (shown in  FIG. 1D ) at the intersection  126  (shown in  FIG. 1D ). The second interaction may produce a second intermetallic compound  120  formed from the diffusion barrier  112  and the alloying material  114  (shown in  FIG. 1D ) at the intersection  126  (shown in  FIG. 1D ). The second intermetallic compound  120  may include the diffusion barrier  112  and the alloying material  114  (shown in  FIG. 1D ). The second intermetallic compound  120  can form a mechanical bond between the diffusion barrier  112  and the alloying material  114  (shown in  FIG. 1D ). The second intermetallic compound  120  may be formed either simultaneously while depositing the alloying material  114  (shown in  FIG. 1D ) or any time thereafter, for example during a subsequent annealing process. 
         [0053]    With continued reference to  FIG. 4 , the diffusion barrier  112  may be deposited with uniform, or near uniform, thickness. The first intermetallic compound  118  may have a non-uniform thickness and can mechanically join the alloying material  114  (shown in  FIG. 1D ) with the copper material  116 . The second intermetallic compound  120  may have a non-uniform thickness and can mechanically join the diffusion barrier  112  with the alloying material  114  (shown in  FIG. 1D ). Formation of the intermetallic compounds  118 ,  120  may consume all or some of the alloying material  114  (shown in  FIG. 1D ). In one embodiment, the alloying material  114  (shown in  FIG. 1D ) is entirely consumed by the formation of the intermetallic compounds  118 ,  120 , as shown in  FIG. 4 . The mechanical bond created by the intermetallic compounds  118 ,  120  can minimize the pistoning effect described above. The integrity of chip interconnects can be greatly improved by minimizing the pistoning effect because of the reduced risk of interconnect failure due to thermal expansion and contraction. 
         [0054]    Now referring to  FIG. 5 , one embodiment of the interconnect structure  100  is shown. A first interaction may occur between the alloying material  114  and the copper material  116  at the intersection  124  (shown in  FIG. 1D ). The first interaction may produce the first intermetallic compound  118  formed from the alloying material  114  and the copper material  116  at the intersection  124  (shown in  FIG. 1D ). The first intermetallic compound  118  may include the alloying material  114  and the copper material  116 . The first intermetallic compound  118  can form a mechanical bond between the alloying material  114  and the copper material  116 . The first intermetallic compound  118  may be formed either simultaneously while plating the copper material  116  or any time thereafter, for example during a subsequent annealing process. 
         [0055]    A second interaction may occur between the diffusion barrier  112  and the alloying material  114  at the intersection  126  (shown in  FIG. 1D ). The second interaction may produce the second intermetallic compound  120  formed from the diffusion barrier  112  and the alloying material  114  at the intersection  126  (shown in  FIG. 1D ). The second intermetallic compound  120  may include the diffusion barrier  112  and the alloying material  114 . The second intermetallic compound  120  can form a mechanical bond between the diffusion barrier  112  and the alloying material  114 . The second intermetallic compound  120  may be formed either simultaneously while depositing the alloying material  114  or any time thereafter, for example during a subsequent annealing process. 
         [0056]    With continued reference to  FIG. 5 , the diffusion barrier  112  may be deposited with uniform, or near uniform, thickness. The first intermetallic compound  118  may have a non-uniform thickness and can mechanically join the alloying material  114  with the copper material  116 . The second intermetallic compound  120  may have a non-uniform thickness and can mechanically join the diffusion barrier  112  with the alloying material  114 . Formation of the intermetallic compounds  118 ,  120  may consume all or some of the alloying material  114 . In one embodiment, the alloying material  114  is not entirely consumed by the formation of the intermetallic compounds  118 ,  120  such that some of the alloying material  114  remains between the first intermetallic compound  118  and the second intermetallic compound  120 , as shown in  FIG. 5 . The mechanical bond created by the intermetallic compounds  118 ,  120  can minimize the pistoning effect described above. The integrity of chip interconnects can be greatly improved by minimizing the pistoning effect because of the reduced risk of interconnect failure due to thermal expansion and contraction. 
         [0057]    Now referring to  FIG. 6 , one embodiment of the interconnect structure  100  is shown. A first interaction may occur between the alloying material  114  and the copper material  116  at the intersection  124  (shown in  FIG. 1D ). The first interaction may produce the first intermetallic compound  118  formed from the alloying material  114  and the copper material  116  at the intersection  124  (shown in  FIG. 1D ). The first intermetallic compound  118  may include the alloying material  114  and the copper material  116 . The first intermetallic compound  118  can form a mechanical bond between the alloying material  114  and the copper material  116 . The first intermetallic compound  118  may be formed either simultaneously while plating the copper material  116  or any time thereafter, for example during a subsequent annealing process. 
         [0058]    A second interaction may occur between the diffusion barrier  112  and the alloying material  114  at the intersection  126 . The second interaction may involve extremely close contact between the diffusion barrier  112  and the alloying material  114  at the intersection  126 . Extremely close contact may create an area of high friction which may result in a mechanical bond between the diffusion barrier  112  and the alloying material  114 . 
         [0059]    The optional electrically insulating liner  110  may be deposited on top of the nonmetallic material  102  and not on the conductive pad  104  prior to depositing the diffusion barrier  112 . In one embodiment, the electrically insulating liner  110  may be deposited on the sidewall  109  and the bottom  108  of the opening  106 . In such embodiments the electrically insulating liner  110 , along with the diffusion barrier  112  and the alloying material  114 , may be subsequently removed from the bottom  108  of the opening  106 . For example, an anisotropic etch may be used to remove the electrically insulating liner  110 , the diffusion barrier  112 , and the alloying material  114  from the bottom  108  to expose the conductive pad  104  without removing material from the sidewall of the opening  106 . Alternatively, the anisotropic etch may be performed to remove each of the deposited layers from the bottom  108  of the opening  106  immediately following their deposition. 
         [0060]    The electrically insulating liner  110  may include any material that which prohibits the conduction of electricity between a copper material and a semi-conductive nonmetallic material. Therefore, if the nonmetallic material  102  is itself electrically insulating, the electrically insulating liner  110  may not be used. The electrically insulating liner  110  may be made from an oxide, nitride, or insulating polymer. Deposition techniques such as, for example, chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD), may be used to deposit the electrically insulating liner  110 . 
         [0061]    With continued reference to  FIG. 6 , the diffusion barrier  112  may be deposited on top of the electrically insulating liner  110  with uniform, or near uniform, thickness. The first intermetallic compound  118  may have a non-uniform thickness and can mechanically join the alloying material  114  with the copper material  116 . Formation of the first intermetallic compound  118  may consume all or some of the alloying material  114 . In one embodiment, the alloying material  114  is not entirely consumed by the formation of the first intermetallic compound  118  such that some of the alloying material  114  remains between the first intermetallic compound  118  and the diffusion barrier  112 , as shown in  FIG. 6 . The mechanical bond created by the first intermetallic compound  118  and extremely close contact between the diffusion barrier  112  and the alloying material  114  can minimize the pistoning effect described above. The integrity of chip interconnects can be greatly improved by minimizing the pistoning effect because of the reduced risk of interconnect failure due to thermal expansion and contraction. 
         [0062]    Referring to  FIGS. 7A-7E , multiple steps of a method of forming a copper interconnect structure are shown. Now referring to  FIG. 7A , a cross-sectional view of an interconnect structure  200  having an opening  206  in a nonmetallic material  202 . The interconnect structure  200  may include lines or wires. In one embodiment, the nonmetallic material  202  may be made from any of several known semiconductor materials such as, for example, a bulk silicon substrate. Non-limiting examples include silicon, germanium, silicon-germanium alloy, silicon carbide, silicon-germanium carbide alloy, and compound (e.g. III-V and II-VI) semiconductor materials. In one embodiment, the nonmetallic material  202  may be made from a dielectric material know to a person having ordinary skill in the art. An optional electrically insulating liner (not shown) may be deposited along a sidewall  209  and on top of the nonmetallic material  202  within the opening  206 . 
         [0063]    Now referring to  FIG. 7B , a diffusion barrier  212  may be deposited along the sidewall  209  and on top of the nonmetallic material  202 . The diffusion barrier  212  may be deposited along the sidewall  209  and a bottom  208  of the opening  206 . The diffusion barrier  212  may include any material that which prohibits contamination of a copper material by the nonmetallic material  202 . In one embodiment, the diffusion barrier  212  may be made from a material including tantalum nitride deposited by physical vapor deposition (PVD). In one embodiment, the diffusion barrier  212  may be deposited by an alternative deposition technique, for example chemical vapor deposition (CVD) or atomic layer deposition (ALD). 
         [0064]    Now referring to  FIG. 7C , a seed layer  222  may be deposited on top of the diffusion barrier  212  and along the sidewall  209  and the bottom  208  of the opening  206 . In one embodiment, the seed layer  222  may be made form a material including copper or any other element capable of seeding copper, i.e. having the correct crystalline structure to seed copper. In other words, the crystal face orientation of the seed layer  222  will mimic the crystal face orientation of copper; such that the surface of the seed layer  222  will allow copper to grow from the its face. In one embodiment, the seed layer  222  may be made from a material including copper and deposited by PVD. In one embodiment, the seed layer  222  may be deposited by CVD or ALD. 
         [0065]    Now referring to  FIG. 7D , an alloying material  214  may be deposited on top of the seed layer  222 , but only along the sidewall  209  of the opening  206 . In one embodiment, the alloying material  214  may be deposited along the sidewall  209  and the bottom  208  of the opening  206 . In such embodiments the alloying material  214  may be subsequently removed from the bottom  208  only by using an anisotropic etch technique selective to the seed layer  222 . In one embodiment, the alloying material  214  may be made from a material including chromium deposited in a vacuum using a sputter deposition technique. In one embodiment, the alloying material  214  may be made from a material including chromium, copper, nickel, tin, magnesium, cobalt, aluminum, manganese, titanium, zirconium, indium, palladium, gold or some combination thereof. The alloying material  214  may not have the correct crystalline structure to serve as a seed for copper plating. In one embodiment, an optional adhesive liner such as gold (not shown) may be used prior to depositing the alloying material  214 . The thickness of the alloying material  214  may be between 50 to about 300 angstroms. 
         [0066]    Now referring to  FIG. 7E , a copper material  216  may be deposited on the seed layer  222  and within the opening  206  (shown in  FIG. 7D ) using an electroplating technique. The seed layer  222  may serve as a cathode to which an electrical potential is applied during an electroplating technique. Specifically, a negative voltage is applied to the seed layer  222 . Because the specific alloying material  214  chosen may not have the correct crystalline structure to serve as a seed for copper plating, a bottom-up plating technique, free of voiding or pinch-off, may therefore be achieved. The bottom-up plating technique results in filling the opening  206  (shown in  FIG. 7D ) with the copper material  216 . After the electroplating technique a chemical mechanical polishing (CMP) technique may be used to remove excess copper from the surface of the substrate. The CMP technique can remove the diffusion barrier  212 , the seed layer  222 , the alloying material  214 , and excess copper material  216  selective to the top surface of the nonmetallic material  202 . 
         [0067]    The alloying material  214  may be used to form a mechanical bond between the copper material  216  and the sidewall  209  of the opening  206 . The mechanical bond can be created either by forming an intermetallic compound or by creating a high friction interface caused by extremely close contact between layers. Extremely close contact may be defined as maximizing interfacial surface contact while minimizing foreign contaminants between two layers. The mechanical bond may be created at an intersection  224  and an intersection  226 . Lack of a mechanical bond between the copper material  216  and the sidewall  209  of the opening  206  may result in a pistoning effect where the copper material  216  moves vertically within the opening  206  during thermal cycling due to copper&#39;s relatively high coefficient of thermal expansion in comparison to surrounding semiconductor materials (e.g. silicon, silicon oxides, and silicon nitrides). Thermal expansion and contraction is inevitable when building or operating integrated circuits. Pistoning of the copper material  216  may impose stress and strain on corresponding components that may be connected to the copper material  216  and over time will cause a failure in these connections. 
         [0068]    Referring to  FIGS. 8-12 , multiple different embodiments of the interconnect structure  200  are shown. Now referring to  FIG. 8 , one embodiment of the interconnect structure  200  is shown. A first interaction may occur between the alloying material  214  (shown in  FIG. 7E ) and the copper material  216  at the intersection  224  (shown in  FIG. 7E ). The first interaction may produce a first intermetallic compound  218  formed from the alloying material  214  (shown in  FIG. 7E ) and the copper material  216  at the intersection  224  (shown in  FIG. 7E ). The first intermetallic compound  218  may include the alloying material  214  (shown in  FIG. 7E ) and the copper material  216 . The first intermetallic compound  218  can form a mechanical bond between the alloying material  214  (shown in  FIG. 7E ) and the copper material  216 . The first intermetallic compound  218  may be formed either simultaneously while plating the copper material  216  or any time thereafter, for example during a subsequent annealing process. 
         [0069]    Formation of the intermetallic compound  218  between the alloying material  214  (shown in  FIG. 7E ) and the copper material  216  may occur when favorable thermodynamic and kinetic conditions exist for the compounds to form as a precipitate within a solid solution of the two materials, in this case the alloying material  214  (shown in  FIG. 7E ) and the copper material  216 . Intermetallic compounds may be stoichiometric or non-stoichiometric. For example, Ag 3 Sn is an intermetallic compound that may form when Ag and Sn are in a solid solution. 
         [0070]    A second interaction may occur between the diffusion barrier  212  and the seed layer  222  at the intersection  226 . The second interaction may involve extremely close contact between the seed layer  222  and the alloying material  214  (shown in  FIG. 7E ) at the intersection  226  (shown in  FIG. 7E ). Extremely close contact may create an area of high friction which may result in a mechanical bond between the seed layer  222  and the alloying material  214  (shown in  FIG. 7E ). Extremely close contact may be achieved by depositing one material on top of another material in a vacuum using a sputter deposition technique. If one material is deposited on another material with either vacuum interruption or via an aqueous system, the possibility for extremely close contact is significantly diminished by native oxides or third body interference films, e.g. water may be present between the interfaces. The seed layer  222  may be deposited on top of the diffusion barrier  112  in a vacuum using the sputter deposition technique, and resulting in an extremely close physical interface. 
         [0071]    With continued reference to  FIG. 8 , the diffusion barrier  212  may be deposited with uniform, or near uniform, thickness. The seed layer  222  may be deposited with uniform, or near uniform, thickness. The first intermetallic compound  218  may have a non-uniform thickness and can mechanically join the alloying material  214  (shown in  FIG. 7E ) with the copper material  216 . Formation of the first intermetallic compound  218  may consume all or some of the alloying material  214  (shown in  FIG. 7E ). In one embodiment, the alloying material  214  (shown in  FIG. 7E ) is entirely consumed by the formation of the first intermetallic compound  218 , as shown in  FIG. 8 . The mechanical bond created by the first intermetallic compound  218  and extremely close contact between the seed layer  222  and the alloying material  214  (shown in  FIG. 7E ) can minimize the pistoning effect described above. The integrity of chip interconnects can be greatly improved by minimizing the pistoning effect because of the reduced risk of interconnect failure due to thermal expansion and contraction. 
         [0072]    Now referring to  FIG. 9 , one embodiment of the interconnect structure  200  is shown. A first interaction may occur between the alloying material  214  and the copper material  216  at the intersection  224  (shown in  FIG. 7E ). The first interaction may produce a first intermetallic compound  218  formed from the alloying material  214  and the copper material  216  at the intersection  224  (shown in  FIG. 7E ). The first intermetallic compound  218  may include the alloying material  214  and the copper material  216 . The first intermetallic compound  218  can form a mechanical bond between the alloying material  214  and the copper material  216 . The first intermetallic compound  218  may be formed either simultaneously while plating the copper material  216  or any time thereafter, for example during a subsequent annealing process. 
         [0073]    A second interaction may occur between the seed layer  222  and the alloying material  214  at the intersection  226 . The second interaction may involve extremely close contact between the seed layer  222  and the alloying material  214  at the intersection  226 . Extremely close contact may create an area of high friction which may result in a mechanical bond between the seed layer  222  and the alloying material  214 . 
         [0074]    With continued reference to  FIG. 9 , the diffusion barrier  212  may be deposited with uniform, or near uniform, thickness. The seed layer  222  may be deposited with uniform, or near uniform, thickness. The first intermetallic compound  218  may have a non-uniform thickness and can mechanically join the alloying material  214  with the copper material  216 . Formation of the first intermetallic compound  218  may consume all or some of the alloying material  214 . In one embodiment, the alloying material  214  is not entirely consumed by the formation of the first intermetallic compound  218  such that some of the alloying material  214  remains between the first intermetallic compound  218  and the seed layer  222 , as shown in  FIG. 9 . The mechanical bond created by the first intermetallic compound  218  and extremely close contact between the seed layer  222  and the alloying material  214  can minimize the pistoning effect described above. The integrity of chip interconnects can be greatly improved by minimizing the pistoning effect because of the reduced risk of interconnect failure due to thermal expansion and contraction. 
         [0075]    Now referring to  FIG. 10 , one embodiment of the interconnect structure  200  is shown. A first interaction may occur between the alloying material  214  (shown in  FIG. 7E ) and the copper material  216  at the intersection  224  (shown in  FIG. 7E ). The first interaction may produce a first intermetallic compound  218  formed from the alloying material  214  (shown in  FIG. 7E ) and the copper material  216  at the intersection  224  (shown in  FIG. 7E ). The first intermetallic compound  218  may include the alloying material  214  (shown in  FIG. 7E ) and the copper material  216 . The first intermetallic compound  218  can form a mechanical bond between the alloying material  214  (shown in  FIG. 7E ) and the copper material  216 . The first intermetallic compound  218  may be formed either simultaneously while plating the copper material  216  or any time thereafter, for example during a subsequent annealing process. 
         [0076]    A second interaction may occur between the seed layer  222  and the alloying material  214  (shown in  FIG. 7E ) at the intersection  226  (shown in  FIG. 7E ). The second interaction may produce a second intermetallic compound  220  formed from the seed layer  222  and the alloying material  214  (shown in  FIG. 7E ) at the intersection  226  (shown in  FIG. 7E ). The second intermetallic compound  220  may include the seed layer  222  and the alloying material  214  (shown in  FIG. 7E ). The second intermetallic compound  220  can form a mechanical bond between the seed layer  222  and the alloying material  214  (shown in  FIG. 7E ). The second intermetallic compound  220  may be formed either simultaneously while depositing the alloying material  214  (shown in  FIG. 7E ) or any time thereafter, for example during a subsequent annealing process. 
         [0077]    With continued reference to  FIG. 10  the diffusion barrier  212  may be deposited with uniform, or near uniform, thickness. The seed layer  222  may be deposited with uniform, or near uniform, thickness. The first intermetallic compound  218  may have a non-uniform thickness and can mechanically join the alloying material  214  (shown in  FIG. 7E ) with the copper material  216 . The second intermetallic compound  220  may have a non-uniform thickness and can mechanically join the seed layer  222  with the alloying material  214  (shown in  FIG. 7E ). Formation of the intermetallic compounds  218 ,  220  may consume all or some of the alloying material  214  (shown in  FIG. 7E ). In one embodiment, the alloying material  214  (shown in  FIG. 7E ) is entirely consumed by the formation of the intermetallic compounds  218 ,  220 , as shown in  FIG. 10 . The mechanical bond created by the intermetallic compounds  218 ,  220  can minimize the pistoning effect described above. The integrity of chip interconnects can be greatly improved by minimizing the pistoning effect because of the reduced risk of interconnect failure due to thermal expansion and contraction. 
         [0078]    Now referring to  FIG. 11 , one embodiment of the interconnect structure  200  is shown. A first interaction may occur between the alloying material  214  and the copper material  216  at the intersection  224  (shown in  FIG. 7E ). The first interaction may produce a first intermetallic compound  218  formed from the alloying material  214  and the copper material  216  at the intersection  224  (shown in  FIG. 7E ). The first intermetallic compound  218  may include the alloying material  214  and the copper material  216 . The first intermetallic compound  218  can form a mechanical bond between the alloying material  214  and the copper material  216 . The first intermetallic compound  218  may be formed either simultaneously while plating the copper material  216  or any time thereafter, for example during a subsequent annealing process. 
         [0079]    A second interaction may occur between the seed layer  222  and the alloying material  214  at the intersection  226  (shown in  FIG. 7E ). The second interaction may produce the second intermetallic compound  220  formed from the seed layer  222  and the alloying material  214  at the intersection  226  (shown in  FIG. 7E ). The second intermetallic compound  220  may include the seed layer  222  and the alloying material  214 . The second intermetallic compound  220  can form a mechanical bond between the seed layer  222  and the alloying material  214 . The second intermetallic compound  220  may be formed either simultaneously while depositing the alloying material  114  or any time thereafter, for example during a subsequent annealing process. 
         [0080]    With continued reference to  FIG. 11 , the diffusion barrier  212  may be deposited with uniform, or near uniform, thickness. The seed layer  222  may be deposited with uniform, or near uniform, thickness. The first intermetallic compound  218  may have a non-uniform thickness and can mechanically join the alloying material  214  with the copper material  216 . The second intermetallic compound  220  may have a non-uniform thickness and can mechanically join the seed layer  222  with the alloying material  214 . Formation of the intermetallic compounds  218 ,  220  may consume all or some of the alloying material  214 . In one embodiment, the alloying material  214  is not entirely consumed by the formation of the intermetallic compounds  218 ,  220  such that some of the alloying material  214  remains between the first intermetallic compound  218  and the second intermetallic compound  220  as shown in  FIG. 11 . The mechanical bond created by the intermetallic compounds  218 ,  220  can minimize the pistoning effect described above. The integrity of chip interconnects can be greatly improved by minimizing the pistoning effect because of the reduced risk of interconnect failure due to thermal expansion and contraction. 
         [0081]    Now referring to  FIG. 12 , one embodiment of the interconnect structure  200  is shown. A first interaction may occur between the alloying material  214  and the copper material  216  at the intersection  224  (shown in  FIG. 7E ). The first interaction may produce a first intermetallic compound  218  formed from the alloying material  214  and the copper material  216  at the intersection  224  (shown in  FIG. 7E ). The first intermetallic compound  218  may include the alloying material  214  and the copper material  216 . The first intermetallic compound  218  can form a mechanical bond between the alloying material  214  and the copper material  116 . The first intermetallic compound  218  may be formed either simultaneously while plating the copper material  216  or any time thereafter, for example during a subsequent annealing process. 
         [0082]    A second interaction may occur between the seed layer  222  and the alloying material  214  at the intersection  226 . The second interaction may involve extremely close contact between the seed layer  222  and the alloying material  214  at the intersection  226 . Extremely close contact may create an area of high friction which may result in a mechanical bond between the seed layer  222  and the alloying material  214 . 
         [0083]    The optional electrically insulating liner  210  may be deposited on top of the nonmetallic material  202  prior to depositing the diffusion barrier  212 . The electrically insulating liner  210  may include any material that which prohibits the conduction of electricity between a copper material and a semi-conductive nonmetallic material. Therefore, if the nonmetallic material  202  is itself electrically insulating, the electrically insulating liner  210  may not be used. The electrically insulating liner  210  may be made from an oxide, nitride, or insulating polymer. Deposition techniques such as, for example, chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD), may be used to deposit the electrically insulating liner  210 . 
         [0084]    With continued reference to  FIG. 12 , the diffusion barrier  212  may be deposited on top of the electrically insulating liner  210  with uniform, or near uniform, thickness. The first intermetallic compound  218  may have a non-uniform thickness and can mechanically join the alloying material  214  with the copper material  216 . Formation of the first intermetallic compound  218  may consume all or some of the alloying material  214 . In one embodiment, the alloying material  214  is not entirely consumed by the formation of the first intermetallic compound  218  such that some alloying material  214  remains between the first intermetallic compound  218  and the seed layer  222 , as shown in  FIG. 12 . The mechanical bond created by the first intermetallic compound  218  and extremely close contact between the seed layer  222  and the alloying material  214  can minimize the pistoning effect described above. The integrity of chip interconnects can be greatly improved by minimizing the pistoning effect because of the reduced risk of interconnect failure due to thermal expansion and contraction. 
         [0085]    The descriptions of the various embodiments of the present invention have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiment, the practical application or technical improvement over technologies found in the marketplace, or to enable other of ordinary skill in the art to understand the embodiments disclosed herein.

Technology Category: 4