Abstract:
The present disclosure is directed to, among other things, an illustrative method that includes forming an opening in a dielectric material of a contact level of a semiconductor device, and selectively depositing a conductive material in the opening to form a contact element therein, the contact element extending to a contact area of a circuit element and having a laterally restricted excess portion formed outside of the opening and above the dielectric material. The disclosed method further includes forming a sacrificial material layer above the dielectric material and the contact element, the sacrificial material layer surrounding the laterally restricted excess portion. Additionally, the method includes planarizing a surface topography of the contact level in the presence of the sacrificial material so as to remove the laterally restricted excess portion from above the dielectric material.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a divisional of co-pending application Ser. No. 12/962,968, filed Dec. 8, 2010, which claimed priority from German Patent Application No. 10 2010 003 556.4, filed March  31 ,  2010 . 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present disclosure generally relates to the fabrication of integrated circuits, and, more particularly, to the contact level of a semiconductor device, in which contact areas, such as gate electrodes and drain and source regions, are connected to the metallization system of the semiconductor device by means of contact elements formed on the basis of electrochemical deposition techniques. 
         [0004]    2. Description of the Related Art 
         [0005]    In modern integrated circuits, such as microprocessors, storage devices and the like, a very high number of circuit elements, especially transistors, are provided on a restricted chip area. Although immense progress has been made over recent decades with respect to increased performance and reduced feature sizes of the circuit elements, the ongoing demand for enhanced functionality of electronic devices forces semiconductor manufacturers to steadily reduce the dimensions of the circuit elements and to increase the operating speed thereof. The continuing scaling of feature sizes, however, involves great efforts in redesigning process techniques and developing new process strategies and tools so as to comply with new design rules. Generally, in complex circuitry including complex logic portions, MOS technology is presently a preferred manufacturing technique in view of device performance and/or power consumption and/or cost efficiency. In integrated circuits including logic portions fabricated by MOS technology, many field effect transistors (FETs) are provided that are typically operated in a switched mode, that is, these devices exhibit a highly conductive state (on-state) and a high impedance state (off-state). The state of the field effect transistor is controlled by a gate electrode, which controls, upon application of an appropriate control voltage, the conductivity of a channel region formed between a drain terminal and a source terminal. 
         [0006]    On the basis of the field effect transistors, more complex circuit components may be composed, such as inverters and the like, thereby forming complex logic circuitry, memory devices and the like. Due to the reduced dimensions, the operating speed of the circuit components has been increased with every new device generation, wherein, however, the limiting factor of the finally achieved operating speed of complex integrated circuits is no longer the individual transistor elements but the electrical performance of the complex wiring network, which may be formed above the device level including the actual semiconductor-based circuit elements, such as transistors and the like. Typically, due to the large number of circuit elements and the required complex layout of modern integrated circuits, the electrical connections of the individual circuit elements cannot be established within the same device level on which the circuit elements are manufactured, but require one or more additional metallization layers, which generally include metal-containing lines providing the inner-level electrical connection, and also include a plurality of inter-level connections, which are also referred to as vias. These interconnect structures comprise an appropriate metal and provide the electrical connection of the individual circuit elements and of the various stacked metallization layers. 
         [0007]    Furthermore, in order to establish a connection of the circuit elements with the metallization layers, an appropriate vertical contact structure is provided, which connects to a respective contact region of a circuit element, such as a gate electrode and/or the drain and source regions of transistors, and to a respective metal line in the metallization layer. The contact structure may comprise contact elements or contact plugs formed in an interlayer dielectric material that encloses and passivates the circuit elements. Upon shrinking the critical dimensions of the circuit elements in the device level, the dimensions of metal lines, vias and contact elements also have to be adapted to the reduced dimensions, thereby requiring sophisticated metal-containing materials and dielectric materials in order to reduce the parasitic capacitance in the metallization layers and provide sufficiently high conductivity of the individual metal lines and vias. For example, in complex metallization systems, copper in combination with low-k dielectric materials, which are to be understood as dielectric materials having a dielectric constant of approximately 3.0 or less, are typically used in order to achieve the required electrical performance and the electromigration behavior as is required in view of reliability of the integrated circuits. Consequently, in lower lying metallization levels, metal lines and vias having critical dimensions of approximately 100 nm and significantly less may have to be provided in order to achieve the required packing density in accordance with density of circuit elements in the device level. 
         [0008]    Upon further reducing the dimensions of the circuit elements, for instance using critical dimensions of 50 nm and less, the contact elements in the contact level may have to be provided with appropriate critical dimensions in the same order of magnitude. The contact elements may typically represent plugs, trenches and the like which are formed of an appropriate metal or metal composition, wherein, in sophisticated semiconductor devices, tungsten in combination with appropriate barrier materials has proven to be a viable contact metal. When forming tungsten-based contact elements, typically, the interlayer dielectric material may be formed first and may be patterned so as to receive contact openings, which may extend through the interlayer dielectric material to the corresponding contact areas of the circuit elements. For this purpose, openings of very different depth may have to be formed in the interlayer dielectric material in order to connect to gate electrode structures or any other conductive lines formed above the semiconductor layer, while other contact openings have to be extended down to a semiconductor layer, i.e., any contact areas formed therein. In particular, in densely packed device regions, the lateral size of the drain and source areas and thus the available area for the contact regions may be 100 nm and less, thereby requiring extremely complex lithography and etch techniques in order to form the contact openings with well-defined lateral dimensions and with a high degree of alignment accuracy, while the difference in etch depth may additionally contribute to the overall complexity of the patterning process. After exposing the contact areas, frequently provided in the form of metal silicide regions, a barrier material has to be provided, for instance in the form of a material system including titanium and titanium nitride, wherein the titanium material may provide the required adhesion characteristics, while the titanium nitride material may preserve integrity of the interlayer dielectric material during the subsequent deposition of the tungsten material, which may be accomplished on the basis of sophisticated chemical vapor deposition (CVD) techniques in which a direct contact between silicon dioxide-based materials and the deposition ambient for depositing the tungsten material is to be avoided. Typically, the actual deposition of the tungsten material may be preceded by the deposition of a nucleation layer based on tungsten, which may be accomplished by a dedicated deposition step, after which the actual fill material may be provided. After the deposition of these materials, any excess material is removed by chemical mechanical polishing (CMP), thereby forming the insulated contact elements in the interlayer dielectric material. Although the process sequence for patterning the contact openings and filling these openings with barrier materials and tungsten results in contact elements having a desired contact resistivity for semiconductor devices with critical dimensions of 50 nm, a further reduction of the size of the transistors may result in an increased contact resistivity, which may no longer be compatible with the device requirements. That is, upon further device scaling, the increased contact resistivity, which may result from conventional tungsten-based contact regimes, may represent a limiting factor of the operating speed of the integrated circuits, thereby at least partially offsetting many advantages obtained by the further reduction of the critical dimensions in the device level. 
         [0009]    One of the reasons for the inferior contact resistivity in tungsten-based contact technologies is the requirement for barrier materials, possibly in combination with a nucleation layer, which may have an increased resistivity compared to the subsequent tungsten fill material. Since a thickness of the barrier materials and the nucleation layer may not be arbitrarily reduced without jeopardizing the effect of this material system, the amount of less conductive materials relative to the tungsten material may thus increase, thereby over-proportionally contributing to an increased contact resistance. For these reasons, it has been suggested to use other materials or deposition regimes in which the presence of a barrier material of reduced conductivity can be avoided. For example, it has been proposed to use wet chemical deposition techniques, such as the electrochemical deposition in the form of an electroless plating process in order to fill in an appropriate metal material, thereby obtaining a superior fill behavior in order to avoid the creation of any voids or other deposition-related irregularities, which may frequently be observed in complex CVD-based techniques in which a complex material system may have to be deposited within sophisticated contact openings, in particular when these openings may have very different depths. Although the electroless deposition technique may be very advantageous with respect to the gap-filling capability and the selection of an appropriate contact material, thereby providing the possibility of avoiding any barrier materials, it turns out that the selective material growth generates in a non-continuous layer of excess metal, which in turn may result in significant contact failures, as will be described with reference to  FIGS. 1   a - 1   c  in more detail. 
         [0010]      FIG. 1   a  schematically illustrates a cross-sectional view of a semiconductor device  100  comprising a substrate  101  and a semiconductor layer  102 . The semiconductor layer  102  may comprise any appropriate semiconductor material, such as silicon, silicon/germanium and the like, as is required for forming therein and thereabove circuit elements  150 , for instance in the form of transistors, which, in the example shown in  FIG. 1   a , are illustrated as planar field effect transistors. It should be appreciated that the substrate  101  and the semiconductor layer  102  may represent a silicon- or semiconductor-on-insulator (SOI) configuration, when a buried insulating material (not shown) is provided between the semiconductor layer  102  and the substrate  101 . In other cases, the semiconductor material of the layer  102  may directly connect to a crystalline semiconductor material of the substrate  101 , thereby forming a bulk configuration. The semiconductor layer  102  comprises a plurality of semiconductor regions or active regions  102 A,  120 B,  102 C, which may be individually laterally delineated by isolation structures (not shown) or which may represent continuous semiconductor regions, depending on device requirements. The active regions  102 A,  102 B,  102 C are to be understood as semiconductor regions in which appropriate dopant profiles are established as required for the various circuit elements, such as the transistors  150 . For example, drain and source regions  151  may be provided with an appropriate vertical and lateral dopant profile in accordance with the required electronic characteristics of the transistors  150 . Furthermore, the drain and source regions  151  may have areas of superior conductivity, for instance provided in the form of a metal silicide, such as nickel silicide, indicated by  154 , which may at least partially act as a contact area for connecting to contact elements to be formed in a later manufacturing stage. Furthermore, the circuit elements  150 , for instance in the form of field effect transistors, may also comprise certain components formed above the semiconductor layer  102 , for instance in the form of a gate electrode structure  152 , which may control the current flow in the transistors  150  upon applying an appropriate control voltage. The gate electrode structures  152  may have any appropriate configuration, that is, they may comprise appropriate gate dielectric materials, for instance in the form of silicon dioxide, silicon oxynitride, high-k dielectric materials, which are to be understood as dielectric materials having a dielectric constant of 10.0 and higher, and the like. Moreover, appropriate electrode material or materials may be provided, for instance in the form of doped semiconductor materials, metal-containing materials, such as a metal silicide, electrode metals and the like. 
         [0011]    Moreover, in the manufacturing stage shown in  FIG. 1   a , a contact level  120  is provided in an intermediate manufacturing stage. The contact level  120  is to be understood as a device level of the semiconductor device  100  which provides for an appropriate isolation and passivation of the circuit elements  150  formed in and above the semiconductor layer  102 , while at the same time electrically connecting the circuit elements  150  to a metallization system (not shown) that is to be formed above the contact level  120  and which may comprise metal features provided in a plurality of metallization layers in order to form the complex interconnect structure as required by the circuit layout of the device  100 . The contact level  120  comprises one or more appropriate dielectric materials, such as a dielectric layer  121 , for instance in the form of a silicon nitride material, a nitrogen-enriched silicon carbide material and the like, in combination with a silicon dioxide layer  122 , as these materials represent well-established dielectric materials for the contact level of the semiconductor device  100 . Moreover, the contact level  120  is illustrated in the manufacturing stage in which contact openings  123 A,  123 B are provided so as to extend to the semiconductor layer  102 , i.e., to any contact areas formed therein, such as the metal silicide regions  154 . It should be appreciated that other contact openings (not shown) may extend to the gate electrode structures  152 , while, in other cases, any such contact elements extending to different gate levels within the semiconductor device  100  may be formed prior to or after providing the contact openings  123 A,  123 B. 
         [0012]    The semiconductor device  100  as illustrated in  FIG. 1   a  may be formed on the basis of the following process strategies. The active regions  102 A,  102 B,  102 C may be provided upon forming appropriate isolation structures (not shown), which may be accomplished by using sophisticated lithography, patterning, deposition and planarization techniques in order to form trenches in the semiconductor layer  102  so as to extend down to a desired depth and refilling the trenches with an appropriate dielectric material. Prior to or after forming the isolation structures, dopant species may be introduced into the active regions  102 A,  102 B,  102 C as required for adjusting the basic electronic characteristics of the circuit elements  150 . Next, the gate electrode structures  152  are formed by applying any appropriate process strategy, depending on the desired configuration of the gate electrode structures  152 . For example, appropriate gate dielectric materials may be formed, followed by the deposition of an electrode material, which may then be patterned on the basis of sophisticated lithography and etch techniques. Thereafter, the drain and source regions  151  may be formed, for instance by ion implantation and the like, and after any anneal processes, the metal silicide regions  154  may be provided by applying well-established silicidation techniques. Depending on the overall process strategy, metal silicide regions may also be formed in the gate electrode structures  152 , if required. Next, the dielectric materials  121 ,  122  may be formed, for instance, by plasma enhanced CVD techniques, sub-atmospheric CVD, high density plasma CVD and the like. If required, a planarization of the material  122  may be performed, for instance by using well established CMP techniques, in which well-established process recipes may be applied for removing a portion of the material  122 , for instance a silicon dioxide material, thereby obtaining a substantially planar surface topography of the contact level  120 . Next, a lithography process may be applied, for instance on the basis of hard mask materials, if required, in order to provide an etch mask (not shown) which defines the lateral position and size of the contact openings  123 A,  123 B. Next, a complex etch sequence may be applied so as to etch through the dielectric materials  122 ,  121 , thereby finally exposing a portion of the metal silicide regions  154 , which may thus act as contact areas. 
         [0013]    As previously discussed, the lateral dimensions of the contact openings  123 A,  123 B, at least in one dimension, i.e., in the horizontal direction of  FIG. 1   a , may have to be adapted to the reduced lateral dimensions of the circuit elements  150 , which may represent transistors formed on the basis of critical dimensions of 50 nm and less, if, for instance, the length of the gate electrode structures  152  is considered. Thus, the contact openings  123 A,  123 B also have to be formed on the basis of similar critical dimensions, which may increasingly result in reduced device performance caused by an increased contact resistivity when using well-established process strategies based on tungsten and CVD deposition techniques, as indicated above. Consequently, new materials and deposition strategies for the contact level  120  have been proposed in order to avoid the deposition of complex barrier materials and seed materials, as is typically associated with CVD-based tungsten deposition regimes. Therefore, selective deposition techniques have been developed in which appropriate materials may be directly formed on the contact areas  154 , without requiring additional barrier and seed materials on the sidewalls of the contact openings  123 A,  123 B. For example, electroless plating is an electrochemical deposition technique in which an appropriate electrolyte solution is provided, which comprises a reducing agent in combination with a salt including the desired metal component in addition with other chemical agents. Consequently, the deposition of the metal may be achieved on an appropriate surface, such as the contact area  154 , which thus acts as a catalyst material, thereby avoiding the application of an external electrical power and also the application of additional seed materials. Consequently, during the deposition process, the metal material is increasingly growing on the contact areas  154  on the basis of an autocatalytic reaction, wherein, during the further advance of the process, the appropriate reducing agent provides for the deposition of the contact metal on the previously deposited contact metal. Consequently, a superior growth behavior from bottom to top may be accomplished on the basis of the electroless deposition process, thereby avoiding any irregularities, such as voids and seams, which may thus result in superior uniformity of the contact metal. Due to the lack of any additional barrier and seed materials, a superior conductivity of the contact elements may be obtained, even if the specific resistivity of the contact metal may be somewhat higher compared to, for instance, a pure tungsten material. For example, cobalt may be efficiently deposited directly on metal silicide regions, such as the contact areas  154 , thereby obtaining contact elements of superior conductivity, even though cobalt has a higher specific resistivity compared to tungsten. 
         [0014]    Figure lb schematically illustrates the semiconductor device  100  in a further advanced manufacturing stage. As illustrated, contact elements  123  are formed in the contact openings  123 A,  123 B on the basis of an electroless plating process, wherein the selective growth behavior and the requirement for providing a certain degree of overgrowth in view of compensating for process and device non-uniformities, such as contact openings of different depth, different growth rates caused by different local growth conditions, which may be correlated with a different density of contact openings, and the like, may result in a “mushroom” like configuration of the contact elements  123 . In other words, the conductive contact metal may extend above the dielectric material of the contact level  120 , and may laterally extend along a portion of the contact level, however, without forming a continuous metal layer across the entire surface of the contact level  120 . The non-continuous configuration of the excess material of the contact elements  123 , however, may significantly influence the further processing of the device  100  when applying well-established CMP techniques for removing any excess metal from the contact level  120 . 
         [0015]      FIG. 1  c schematically illustrates a cross-sectional view of a portion of the semiconductor device  100  when performing a CMP process  103  in order to remove any excess material of the contact elements  123 . For convenience, a single contact element  123  is illustrated during the polishing process  103 , wherein, due to the “mushroom” like shape of the element  123 , significant forces, as indicated by  103 F, act on the contact element  123 . For example, significantly increased sheer forces may result in corresponding torque forces, which in turn may result in a significant displacement of the contact element  123 , as indicated by the dashed line. Consequently, significant contact failures may be created during the CMP process  103 , which may result in an unacceptable increase of yield losses. For these reasons, currently great efforts are being made in identifying appropriate process parameters for the CMP process  103 , for instance in terms of down force, slurry material and the like, in order to reduce the number of contact failures, which may be caused on the basis of CMP recipes that are typically applied in tungsten deposition regimes, in which a continuous tungsten layer is formed on the contact level  120 . 
         [0016]    The present disclosure is directed to various methods that may avoid, or at least reduce, the effects of one or more of the problems identified above. 
       SUMMARY OF THE INVENTION 
       [0017]    The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an exhaustive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later. 
         [0018]    Generally, the present disclosure provides manufacturing techniques in which contact elements of a semiconductor device may be formed on the basis of selective deposition techniques, such as electroless plating, wherein any undue mechanical stress during the planarization of the contact level after the deposition of the contact metal may be avoided. To this end, in some illustrative embodiments, the contact metal may be appropriately embedded in an appropriate material, such as the dielectric material of the contact level, possibly in combination with additional sacrificial materials, so as to enable the planarization of the contact level without applying undue mechanical stress to the contact metal. For example, by appropriately selecting the initial thickness of the dielectric material of the contact level, any overfilling of the contact openings may be avoided, so that the planarization of the contact level may be accomplished on the basis of an etch process and/or a polishing process in which any excess material of the contact level may be removed without mechanically stressing the contact metal. In other illustrative embodiments disclosed herein, the planarization of the contact level may be accomplished by removing any excess material of the contact metal on the basis of an electrochemical etch process, thereby also efficiently avoiding any undue mechanical stress for the contact elements. Consequently, selective deposition techniques, such as electroless plating, may be efficiently applied for depositing the contact metal with superior uniformity, while undue contact failures may be avoided during planarization of the contact level. 
         [0019]    In one illustrative embodiment, a method is disclosed that includes forming an opening in a dielectric material of a contact level of a semiconductor device, and selectively depositing a conductive material in the opening to form a contact element therein, the contact element extending to a contact area of a circuit element and having laterally restricted excess portion formed outside of the opening and above the dielectric material. The disclosed method further includes, among other things, forming a sacrificial material layer above the dielectric material and the contact element, the sacrificial material layer surrounding the laterally restricted excess portion. Additionally, the method includes planarizing a surface topography of the contact level in the presence of the sacrificial material so as to remove the laterally restricted excess portion from above the dielectric material. 
         [0020]    Another illustrative method disclosed herein includes, among other things, forming a contact opening in a dielectric material of a contact level of a semiconductor device. The method further includes overfilling the contact opening with a conductive contact material, wherein overfilling the contact opening includes forming a contact element portion of the conductive contact material inside of the contact opening and forming laterally restricted excess portion of the conductive contact material outside of the contact opening and above the contact element portion and the dielectric material. Additionally, the illustrative method includes forming a sacrificial material layer above the dielectric material, the sacrificial material layer surrounding and enclosing the laterally restricted excess portion of the conductive contact material, and performing a planarization process in the presence of the sacrificial material so as to remove the laterally restricted excess portion from above the contact element portion and the dielectric material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The disclosure may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which: 
           [0022]      FIGS. 1   a - 1   c  schematically illustrate cross-sectional views of a semiconductor device during various manufacturing stages in forming contact elements on the basis of an electroless plating process and a conventional CMP process for removing any excess material of the contact elements; 
           [0023]      FIGS. 2   a - 2   c  schematically illustrate cross-sectional views of a semiconductor device in various manufacturing stages for forming contact elements on the basis of a selective deposition technique, wherein the planarization of the contact level may be accomplished without exerting undue mechanical stress to the contact elements by laterally embedding the contact metal in the dielectric material of the contact level, according to illustrative embodiments; 
           [0024]      FIGS. 2   d - 2   e  schematically illustrate cross-sectional views of the semiconductor device according to illustrative embodiments in which the contact elements may be embedded on the basis of a sacrificial fill material so as to reduce undue mechanical stress upon planarizing the contact level; and 
           [0025]      FIGS. 2   f - 2   k  schematically illustrate a process strategy for planarizing the contact level of the semiconductor device on the basis of an electrochemical etch process, according to further illustrative embodiments. 
       
    
    
       [0026]    While the subject matter disclosed herein is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION 
       [0027]    Various illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. 
         [0028]    The present subject matter will now be described with reference to the attached figures. Various structures, systems and devices are schematically depicted in the drawings for purposes of explanation only and so as to not obscure the present disclosure with details that are well known to those skilled in the art. Nevertheless, the attached drawings are included to describe and explain illustrative examples of the present disclosure. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase. 
         [0029]    The present disclosure generally provides manufacturing strategies in which contact elements of a semiconductor device may be formed in the dielectric material of the contact level by applying selective deposition techniques, such as electroless plating and the like, while the planarization of the contact level may be accomplished without exerting undue mechanical stress to the contact elements. To this end, in some illustrative embodiments disclosed herein, the initial dielectric material of the contact level may be provided with excess height such that the contact metal may be filled into the contact openings, while reliably avoiding any overfilling of the contact openings. Consequently, the subsequent planarization of the contact level may be performed on the basis of any appropriate material removal process, in which, in some illustrative embodiments, only one dielectric material has to be removed, for instance on the basis of a CMP process, while at the same time the contact metal is laterally embedded in the dielectric material. In other illustrative embodiments, additionally to the lateral embedding of the contact elements in the initial dielectric material of the contact level, a sacrificial fill material, for instance in the form of a planarization material, may be applied and may be used during the planarization of the contact level, thereby providing an even further increased confinement of the contact elements. The sacrificial fill material and the excess material of the dielectric material of the contact level may be removed by using an etch process or a polishing process or a combination thereof 
         [0030]    In still other illustrative embodiments disclosed herein, the contact metal may be deposited on the basis of process parameters which may result in a certain degree of overfilling, while efficient embedding of the contact metal may be accomplished by providing a sacrificial planarization or fill material. Thereafter, an appropriate planarization process may be performed in the presence of the sacrificial material, which may then also be efficiently removed during the planarization process. The planarization process may comprise an etch process, a polishing process or a combination thereof, wherein the sacrificial material may reduce any lateral sheer forces when applying a polishing process. 
         [0031]    In still other illustrative embodiments disclosed herein, the contact metal may be embedded on the basis of a conductive material, such as a metal material, which may be deposited after providing the actual contact metal on the basis of any appropriate deposition technique so as to provide a continuous conductive layer on the dielectric material of the contact level. Based on the continuous conductive layer, an electrochemical etch process may be applied in order to removal any excess material of the contact elements, thereby providing a substantially planar surface topography of the contact level. In some illustrative embodiments, the electrochemical etch process may be performed on the basis of an additional sacrificial material, which may result in superior process conditions, for instance, by covering a portion of the conductive layer at an initial phase of the electrochemical etch process. 
         [0032]    Consequently, the concept of providing the contact metal on the basis of a selective deposition technique, such as an electroless plating process, may be efficiently applied with a high degree of flexibility, for instance with respect to the degree of overfilling of any contact openings and the like, since the planarization of the contact level may be performed on the basis of process strategies in which undue mechanical stresses, for instance caused by conventional CMP strategies, may be avoided. 
         [0033]    With reference to  FIGS. 2   a - 2   k,  further illustrative embodiments will now be described in more detail, wherein reference is also made to  FIGS. 1   a - 1   c  as required. 
         [0034]      FIG. 2   a  schematically illustrates a cross-sectional view of a semiconductor device  200  comprising a substrate  201  in combination with a semiconductor layer  202 , in and above which semiconductor-based circuit elements  250  may be provided. As explained before with reference to the semiconductor device  100 , the substrate  201  and the semiconductor layer  202  may have any appropriate configuration, such as an SOI configuration, a bulk configuration and the like. Furthermore, the circuit elements  250  may represent any circuit elements formed on the basis of a semiconductor material of the semiconductor layer  202 , such as field effect transistors, resistors, capacitors and the like, wherein at least some components may be formed in the semiconductor layer  202 . For example, a doped region  251 , for instance such as a drain or source region of a field effect transistor, may be provided in the semiconductor layer  202  and may represent a part of the circuit element  250 . Moreover, a contact area  252 , such as a metal silicide material, may be provided in the semiconductor layer  202  as a part of the circuit element  250 . It should be appreciated that any criteria discussed above with reference to the semiconductor device  100  and the corresponding circuit element  150  may also apply for the circuit elements  250 . It should further be noted that the circuit element  250  may also comprise any components, such as gate electrode structures and the like, which may be formed above the semiconductor layer  202  and which may require appropriately adapted contact elements, as is also discussed above. 
         [0035]    Moreover, the semiconductor device  200  may comprise a contact level  220 , which is to be understood as a dielectric material  222 , which may include two or more individual material layers, depending on the overall requirements and configuration of the contact level  220 . As also previously discussed with reference to the semiconductor device  100 , the contact level  220  and thus the dielectric material  222  may be formed above and laterally adjacent to any semiconductor-based circuit elements, thereby providing the desired passivation of the circuit elements  250 . For convenience, the dielectric material  222  is illustrated as representing a continuous material system, while, as is, for instance, explained above with reference to the semiconductor device  100 , two or more individual layers, such as an etch stop layer and the like, may be provided, as required for the patterning of the contact level  220 . In some cases, the dielectric material  222  or at least a portion thereof may be provided with a high internal stress level so as to increase performance of certain circuit elements, such as transistors and the like, when the stress level in the contact level  220  may provide superior charge carrier mobility in an associated portion of the semiconductor layer  202 . In the embodiment shown in  FIG. 2   a  and in the corresponding manufacturing stage, the contact level  220  is illustrated such that the dielectric material  222  may comprise an extra portion  222 E which may represent a sacrificial material portion of the contact level  220  to be removed in a later manufacturing stage. Furthermore, contact elements  223  are provided in the contact level  220  so as to connect to the contact areas  252  provided in the semiconductor layer  202 , while, in other cases, in addition to the contact elements  223 , any other contact elements may be provided, which may connect to other circuit components formed above the semiconductor layer  202 , such as gate electrode structures and the like, as is also previously explained. The contact elements  223  may represent a conductive material formed in corresponding contact openings  223 A,  223 B so as to extend to a desired height level without overfilling the contact openings  223 A,  223 B. The conductive material of the contact elements  223  may, in some illustrative embodiments, represent a substantially uniform material, thereby providing superior conductivity and thus contact resistivity of the contact level  220 . In this case, additional barrier materials and the like may not be provided in the contact elements  223 . To this end, any appropriate conductive materials, such as cobalt, or any other appropriate metals, such as aluminum and the like, may be provided. 
         [0036]    The semiconductor device  200  as illustrated in  FIG. 2   a  may be formed on the basis of the following processes. After completing the circuit elements  250  in and above the semiconductor layer  202 , which may be accomplished by using process techniques as also previously discussed with reference to the semiconductor device  100 , the dielectric material or materials of the contact level  220  may be deposited, wherein, contrary to the conventional strategies previously described, the sacrificial portion  222 E may be provided, for instance by increasing the thickness of the final material layer of the contact level  220  or by providing a separate material layer, wherein a thickness of the extra portion  222 E is selected such that a conductive material may be reliably confined within the contact openings  223 A,  223 B after patterning the same on the basis of any appropriate patterning regime. That is, the initial total height of the contact level  220  is selected such that the selective deposition of the conductive material of the contact elements  223  may not result in an overfilling of the contact openings  223 A,  223 B, irrespective of any process-related variations or irrespective of any difference in depth of contact openings, when any contact openings may have to be formed so as to extend to a lower depth, for instance when connecting to gate electrode structures and the like. After patterning the contact openings  223 A,  223 B, a selective deposition process, such as an electroless plating process, may be performed, wherein the exposed portion of the contact areas  252  may act as a catalyst material, thereby avoiding a separate provision of a catalyst material on the contact areas  252 . For example, metals such as cobalt may be directly formed on a metal silicide on the basis of well-established electrochemical deposition recipes. Consequently, during the deposition of the conductive material of the circuit elements  223 , a desired superior bottom-to-top fill behavior may be accomplished while avoiding or at least reducing any deposition-related irregularities as may typically occur in CVD-based techniques, when contact openings of reduced lateral dimensions are to be filled. Moreover, during the selective deposition, the process time may be appropriately controlled so as to achieve a desired fill height in any of the contact openings  223 A,  223 B, irrespective of the initial depth of the contact openings. On the other hand, the contact openings  223 A,  223 B may have an appropriate depth, due to the extra portion  222 E, so as to avoid any overfilling of the contact openings within the desired deposition time. It should be appreciated that the deposition rate may be readily determined in advance, for instance on the basis of experiments, thereby enabling a reliable estimation of a required process time in order to obtain a fill height within any of the contact openings  223 A,  223 B that corresponds to a desired height of the contact elements  223 . 
         [0037]      FIG. 2   b  schematically illustrates the semiconductor device  200  when performing a planarization process  203  in order to provide a planar surface topography for the contact level  220 . In some illustrative embodiments, the planarization process  203  may be performed on the basis of a CMP process, in which mainly material of the contact level  220 , i.e., the excess or sacrificial material portion  222 E, may be removed. To this end, a plurality of well-established CMP recipes are available, wherein the material removal may be accomplished without unduly affecting the contact elements  223 , since these elements are efficiently embedded in the contact level  220 . For example, well-established CMP techniques for removing silicon dioxide material may be applied, when providing the materials  222  and  222 E in the form of a silicon dioxide material. Consequently, during the planarization process  203 , a single material has to be removed at least during most of the removal process  203 , thereby finally exposing a top surface of the contact elements  223 . In some illustrative embodiments, the planarization process  203  performed on the basis of a CMP process may be continued so as to remove a certain portion of the material  222 , as indicated by  222 D, in order to compensate for certain differences in height level of the contact elements  223  within the contact openings  223 A,  223 B. The corresponding removal of a portion of the contact level may be accomplished by a certain degree of over-polishing, wherein a corresponding material loss may be taken into consideration by appropriately adjusting the initial height or thickness of the contact level  220 . It should be appreciated that also during the final phase of the planarization process  203 , any significant sheer forces with respect to the contact elements  223  may be avoided, since the contact elements  223  may still be laterally embedded in the dielectric material  222  of the contact level  220 . 
         [0038]      FIG. 2   c  schematically illustrates the semiconductor device  200  according to further illustrative embodiments in which an additional sacrificial material  224  may be provided above the contact level  220  prior to performing the planarization process  203 . For this purpose, the sacrificial material  224  may be provided in the form of a planarization material, i.e., a material that may be applied on the basis of spin-on techniques and the like, thereby providing a superior planar surface topography, for instance by completely filling the contact openings  223 A,  223 B. To this end, a plurality of polymer materials are available, which may be applied in a low viscous state and which may then be hardened, thereby providing a substantially planar surface topography. In some illustrative embodiments, the planarization process  203  may be performed on the basis of an etch process  203 A, in which the material  224 , and during the further advance of the etch process  203 A also the material  222 E, may be removed, without unduly exposing the contact elements  223  to the reactive process ambient of the process  203 A. For example, the material  224  may have a similar etch behavior as the material  222 E, thereby resulting in a superior surface topography. In other cases, the planarization process  203  may comprise a polishing process  203 B, in which the material  224  and finally the material  222 E may be efficiently removed, while providing superior integrity of the contact elements  223 , which may be exposed at a final phase of the polishing process  203 B only, thereby avoiding undue interaction of the process ambient of the process  203 B and the contact elements  223 . In other illustrative embodiments, the planarization process  203  may be performed on the basis of both the process  203 A and  203 B, for instance by first etching the materials  224 ,  222 E and subsequently applying the polishing process  203 B, during which a difference in height level of the contact elements  223  may be reduced, as is for instance previously described with reference to  FIG. 2   b . 
         [0039]      FIG. 2   d  schematically illustrates the semiconductor device  200  according to further illustrative embodiments. As shown, the contact level  220  may comprise the contact elements  223  having a substantially “mushroom” like configuration, which may be caused by a certain degree of overfilling of the contact openings  223 A,  223 B during the selective deposition process, as is for instance also described with reference to the semiconductor device  100 . Moreover, a sacrificial material  225 , such as a planarization material, may be formed above the contact level  220 , such that the contact elements  223  are embedded, i.e., are laterally embedded in the dielectric material  222  of the contact level  220  and in the sacrificial material  225 . To this end, after forming the contact elements  223  with a desired degree of overfilling, the material  225  may be deposited, for instance by spin-on techniques and the like, in order to provide a superior planar surface topography. In other cases, the material  225  may be provided by any other deposition technique, in combination with a planarization process, such as a polishing process and the like. Based on the configuration as shown in  FIG. 2   d , a further planarization process may be applied so as to provide a planar surface topography for the contact level  220 . 
         [0040]      FIG. 2   e  schematically illustrates the semiconductor device  200  at an intermediate phase of the planarization process  203 , which may be performed on the basis of an etch process  203 A and/or a polishing process  203 B. For example, when applying the etch process  203 A, an appropriate etch recipe may be applied, such as a plasma-assisted etch process, a wet chemical etch process, in which the material  225  and the conductive material of the contact elements  223  may have a very similar removal rate. Consequently, in the phase of the etch process  203 A as shown in  FIG. 2   e , the material  225  and the material of the contact elements  223  may be concurrently removed, wherein the corresponding etch process may be controlled on the basis of the material  222 , which may act as an efficient etch stop material. 
         [0041]    In other illustrative embodiments, the polishing process  203 B may be performed on the basis of a process recipe, in which substantially the same removal rate may be obtained for the material  225  and the contact elements  223 . For example, the characteristics of the sacrificial material  225  may be efficiently adjusted, for instance in terms of hardness and the like, by performing appropriate treatments when providing a polymer material and/or by selecting an appropriate basic material composition when using any other material. For example, the conductive material of the contact elements  223 , which may be provided in the form of a homogeneous metal, may have a reduced thickness and thus a polymer material may be appropriate for obtaining a similar removal rate on the basis of a polishing recipe, in which substantially the physical removal mechanism may be dominant. Consequently, any undue sheer forces during the process  203 B may be avoided, thereby reducing the probability of creating contact failures, as may be the case in the conventional strategy previously explained. Furthermore, in other illustrative embodiments, a combination of an etch process and a polishing process may be applied. 
         [0042]      FIG. 2   f  schematically illustrates the semiconductor device  200  according to further illustrative embodiments, in which the contact elements  223  may form a non-continuous material system above the contact level  220 , for instance caused by a certain degree of overfilling, as indicated above, wherein, additionally, a sacrificial material  226  may be provided in the form of a continuous conductive material layer. For this purpose, after forming the contact elements  223  on the basis of a selective deposition process, the continuous conductive layer  226  may be provided, for instance by applying any appropriate deposition technique, such as CVD, sputter deposition and the like so that contact elements  223  are “embedded” by means of the dielectric material  222  and the conductive material layer  226 . The conductive material layer  226  may be comprised of any appropriate conductive material, such as a metal layer and the like, which may act as a current distribution layer for a removal process performed on the basis of an electrochemical mechanism. 
         [0043]      FIG. 2   g  schematically illustrates a electrochemical etch system  260 , which may be configured to receive the substrate  201  in order to perform an electrochemical planarization process on the contact level  220  comprising the conductive sacrificial layer  226  as shown in  FIG. 2   f . The system  260  may comprise a support system  262  that is configured to receive the substrate  201 , wherein, in the embodiment shown, the surface to be treated, i.e., the contact level  220 , may be provided within a reactor or vessel  261 . Furthermore, the system  260  may comprise an electrode assembly  264 , which may represent a movable electrode assembly, which may be scanned across the substrate  201 , thereby forming a movable gap between the surface to be treated, i.e., the contact level  220 , and the moving electrode assembly  264 . Moreover, the electrode assembly  264  may be appropriate configured so as to provide one or more jets of appropriate fluids, as indicated by  265 , for instance for providing an electrolyte solution or any other appropriate process fluid required for initiating an electrochemical material removal process. For example, the electrolyte  265  may contain a mixture of an inert solvent and a conducting salt of a non-oxidizing acid. Furthermore, a power source  263  may be provided so as to enable the application of voltage and thus current pulses between the surface  220 , which may act as an anode, and the movable electrode assembly  264 , which may act as a cathode. Consequently, upon initiating an appropriate voltage or a sequence of voltage pulses, a current flow may be established between the surface to be treated, i.e., the contact level  220  comprising the conductive layer  226  and the excess material of the contact elements  223  ( FIG. 20  and the movable electrode assembly  264  via the process fluid  265 . Based on the corresponding scan speed, the sequence of voltage pulses, the composition of the electrolyte solution or generally the process fluid  265 , an efficient material removal of the layer  226  and the excess material of the contact elements  223  may be initiated, wherein preferably a material removal may be obtained for portions having an increased thickness of metal formed above the contact level  220 . Consequently, during the electrochemical etch process, the overall surface topography may be increasingly planarized, for instance by scanning across the substrate  201  several times, for instance by using different process conditions, such as pulse sequences, scan speeds and the like. 
         [0044]      FIG. 2   h  schematically illustrates the substrate  201  during a certain phase of an electrochemical etch process  267 , wherein the movable electrode assembly  264  may be moved along a scan direction  266  on the basis of process parameters, such as voltage and shape and frequency of pulses, scan speed along the direction  266  and the like. 
         [0045]      FIG. 2   i  schematically illustrates the substrate  201  in a further advanced stage of the electrochemical etch process  267 , wherein the movable electrode assembly  264  may be positioned at approximately the center of the substrate  201 . Consequently, by scanning across the substrate  201  one or several times, any excess material of the contact elements  223  and the sacrificial conductive material layer  226  ( FIG. 20  may be removed, thereby resulting in a substantially planar surface topography. It should be appreciated that appropriate process parameters may be readily established on the basis of experiments by performing electrochemical etch processes on the basis of different process parameter settings and observing the removal behavior and the planarization effect of the various parameter settings. 
         [0046]      FIG. 2   j  schematically illustrates the semiconductor device  200  with a planar surface topography, as indicated by  220 S. Consequently, also in this case, the contact elements  223  may be provided with a desired planar configuration without exerting any undue mechanical stress to the contact elements  223 . 
         [0047]      FIG. 2   k  schematically illustrates the semiconductor device  200  according to further illustrative embodiments, in which a further sacrificial material  227  may be formed above the conductive material layer  226 . The further sacrificial material  227  may be provided in the form of a planarization material, such as a polymer material, and may be etched back after application, so as to cover the material  226  at surface portions of the contact level  220  outside of the contact elements  223 , which may be advantageous when performing the electrochemical etch process  267 , as described above. That is, the electrochemical etch process may be initiated on the basis of any appropriate process parameters, wherein an initial material removal of the layer  226  may be suppressed due to the presence of the additional sacrificial material  227 . Consequently, in a corresponding phase of the electrochemical etch process, exposed portions of the material layer  226  and the excess material of the contact elements  223  may be preferably removed, thereby further enhancing the planarizing effect of the electrochemical etch process. The electrochemical etch process may have a substantially self-limiting behavior in that the conductive material around the contact elements  223  may be removed so as to finally interrupt the continuous layer  226  around the contact elements  223 . Thereafter, the layer  227  may be removed, for instance by wet chemical etch techniques, plasma-enhanced etch processes, and the like, followed by the removal of the remaining portions of the layer  226 , which may be accomplished by wet chemical etch processes, CMP and the like. In other cases, the electrochemical etch process may be interrupted so as to remove the material  227 , after a certain degree of planarization has been achieved, and thereafter the electrochemical etch process may be continued in order to remove the remaining material  226  and any undesired excess material of the contact elements  223 , however, on the basis of less sophisticated process conditions with respect to a height difference between the layer  226  and the contact elements  223 . 
         [0048]    As a result, the present disclosure provides process strategies in which contact elements may be formed on the basis of selective deposition techniques, such as electroless plating, wherein the subsequent planarization of the contact level may be accomplished without inducing undue mechanical stress in the contact element. To this end, in some illustrative embodiments, an appropriate embedding of the contact metal of the contact elements may be achieved, for instance by reliably avoiding an overfilling of the corresponding contact openings and/or by providing a sacrificial material, which may preserve integrity of the contact elements on performing a planarization process, for instance in the form of an etch process, a polishing process or a combination thereof. In still further illustrative embodiments, the removal of any excess material of the contact elements may be accomplished on the basis of electrochemical etch processes, wherein a sacrificial conductive layer may be used as a current distribution layer. Consequently, the further processing may then be continued on the basis of a planar surface topography of the contact level and thus the very first metallization layer of a metallization system may then be formed so as to appropriately connect to the contact elements in the contact level, which may have a superior conductivity due to the selective deposition technique used for forming the metal of the contact elements. 
         [0049]    The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. For example, the process steps set forth above may be performed in a different order. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. 
         [0050]    Accordingly, the protection sought herein is as set forth in the claims below.