Abstract:
Interconnects containing ruthenium and methods of forming can include utilization of a sacrificial protective material. Planarization or other material removal operations can be performed on a substrate having a recess, the recess containing a ruthenium containing material along with the sacrificial protective material. The protective material is later removed, and a conductor can be filled in the remaining recess.

Description:
TECHNICAL FIELD 
       [0001]    Various embodiments described herein relate to apparatus, systems, and methods associated with interconnects, such as contacts and interconnection lines. 
       BACKGROUND 
       [0002]    Ruthenium has been investigated as a barrier and/or seed material. Using ruthenium in place of other barrier metals such as tantalum can lower contact resistance, improve adhesion of subsequent conductors, and improve gap filling capability due to its seed enhancement at small dimensions. 
         [0003]    Ruthenium is a rare transition metal of the platinum group of the periodic table and chemically resistant to most other chemicals. Compared to ruthenium, copper is a more reactive metal. Copper is more easily corroded under either acidic and alkali conditions. When ruthenium is used as barrier for copper interconnects, processing operations such as slurry polishing and post chemical mechanical processing (CMP) chemistry clean accelerates copper chemical dissolution much faster than ruthenium, resulting in preferential material removal, such as dishing, voiding and corrosion of copper structures, while ruthenium is removed much slower. 
         [0004]    It is desirable to improve processes using ruthenium in interconnects. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIGS. 1-2  show a substrate in various stages of processing according to an embodiment of the invention. 
           [0006]      FIG. 3A  shows a substrate in a stage of processing with a protective material according to an embodiment of the invention. 
           [0007]      FIG. 3B  shows another substrate in a stage of processing with a protective material according to an embodiment of the invention. 
           [0008]      FIGS. 4-7  show a substrate in various stages of processing according to an embodiment of the invention. 
           [0009]      FIG. 8  shows an information handling system utilizing interconnects formed according to embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    In the following detailed description of the invention, reference is made to the accompanying drawings that form a part hereof and in which are shown, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and structural, logical, and electrical changes may be made. 
         [0011]    The term “horizontal” as used in this application is defined as a plane parallel to the conventional plane or surface of a substrate, such as a wafer or die, regardless of the orientation of the substrate. The term “vertical” refers to a direction perpendicular to the horizontal as defined above. Prepositions, such as “on”, “side” (as in “sidewall”), “higher”, “lower”, “over” and “under” are defined with respect to the conventional plane or surface being on the top surface of the substrate, regardless of the orientation of the substrate. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled. 
         [0012]      FIG. 1  shows a substrate  100 , including an interconnect, such as an electrical contact  112 , and an electrical isolation region  110 . The electrical contact  112  is located within a recess  101  of the isolation region  110 . In one example, the recess is part of a contact (e.g. a via) in a semiconductor device used to electrically connect an electronic device such as a transistor, capacitor, memory cell, etc. with other components. In one example the recess  101  includes an elongated recess (e.g. trench) used to form an interconnect such as an interconnection line in an electronic device. 
         [0013]    Examples of electrical contacts  112  can include tungsten or tungsten alloy contacts. Although the contact  112  of  FIG. 1  is shown as a single block, in one example, the electrical contact  112  can include layers of material. In selected examples, the isolation region  110  includes a dielectric material, such as silicon oxide, silicon nitride, or other electrically insulating materials. 
         [0014]      FIG. 2  shows a material  120  containing ruthenium formed (e.g., deposited) over the electrical contact  112  in the recess  101 . In one example the material  120  serves as an adhesion layer and/or a barrier layer to prevent or reduce diffusion or migration of materials above and/or below the material  120 . In one example, the material  120  containing ruthenium comprises, consists, or consists essentially of substantially pure ruthenium metal. In other examples, the material  120  comprises, consists, or consists essentially of a ruthenium alloy of two or more components. In other examples, the material  120  containing ruthenium includes two or more conductive layers. One layered example comprises, consists, or consists essentially of a ruthenium containing layer and a titanium nitride layer. Another layered example comprises, consists, or consists essentially of a ruthenium containing layer and a tantalum nitride layer. Another layered example comprises, consists, or consists essentially of a ruthenium containing layer and a tantalum layer. In selected layer examples, the ruthenium containing layer comprises, consists, or consists essentially of ruthenium metal or a ruthenium alloy. 
         [0015]      FIG. 2  shows the material  120  containing ruthenium deposited as a conformal layer, covering at least a portion of a top surface  114  and sidewalls  116  of the isolation region  110 , and a top surface  113  of the electrical contact  112 . Although a thickness of the material  120  is shown as substantially uniform, other examples may include anisotropic deposition. In one example, the thickness of the coating  120  is between 100 and 130 angstroms. 
         [0016]    In one example, the material  120  containing ruthenium is deposited using chemical vapor deposition. Other deposition methods include, but are not limited to, atomic layer deposition (ALD) and physical vapor deposition. 
         [0017]      FIGS. 3A and 3B  show examples of a protective material formed over the material  120  containing ruthenium. In  FIG. 3A , a conformal coating of protective material  130  is shown covering the material  120  at a substantially uniform thickness. The example configuration of  FIG. 3A  leaves a gap  131  within the recess  101 .  FIG. 3B  shows another configuration of a protective material  132  formed over the material  120  containing ruthenium. In  FIG. 3B , a protective material  132  is shown filling in the gap in the recess  101  over the ruthenium containing material  120 . 
         [0018]    The protective material  130 ,  132  provides chemical and mechanical protection of the material  120  containing ruthenium. The protective material chosen is substantially non-reactive with the material  120  containing ruthenium, and is easily removed at a later stage of processing using methods such as etching, washing, buffing, etc. 
         [0019]    One example of a suitable protective material includes silicon nitride (Si 3 N 4 ). Another example of a suitable protective material includes resist carbon. Other materials with selective reactivity or selective removability with respect to ruthenium can be used in various embodiments. 
         [0020]      FIG. 4  illustrates removal of an upper portion of the material  120  containing ruthenium and the example protective material  132  (as well as a portion of the isolation region  110 ). The example protective material  132  is used for illustration, however processing operations in the following description can also be used with embodiments of protective material  130  from  FIG. 3A . 
         [0021]    In one example, the removal includes a planarization operation of the top surface  114  of the substrate  100 . In one example, the planarization includes a chemical-mechanical polishing (CMP) operation. The slurry in a CMP operation can be selected to be particularly aggressive when removing ruthenium, due to ruthenium&#39;s relatively inert properties to chemical removal, and due to ruthenium&#39;s mechanical hardness and strength. In the examples shown, the protective material  132  is a sacrificial material that protects a bottom  121  and sides  122  of the material  120  containing ruthenium during the harsh CMP process. Because the protective material  132  is sacrificial, damage to the protective material  132  during a CMP operation does not matter, provided the bottom  121  and sides  122  of the material  120  containing ruthenium remain protected. The CMP process on top surface  114  can shorten trenches with minimal oxide recess, thus potentially resulting in an easier aspect ratio to fill. 
         [0022]    After removal of the upper portions of the material  120  and the protective material  132 , the remainder of the protective material  132  is removed, as illustrated in  FIG. 5 . In one example, an etch operation is used to remove the remaining protective material  132 . Examples of chemical solutions that remove the protective material  132  without removing the material  120  containing ruthenium include 85% H 3 PO 4 :15% H 2 O; H 3 PO 4  and H 2 O 2  solutions; H 2 O+H 2 O 2 +HCl solutions, or other suitable solutions that strip the protective material  132  without significant removal of the material  120  containing ruthenium. Other processes such as ultrasonic cleaning and/or washing, etc. may also be used. As described above, the remaining material  120  is in good shape, and the bottom  121  and sides  122  of the material  120  have been protected. 
         [0023]      FIG. 6  shows a deposition of a conductor  140  into the recess  101 , such as by PVD or electroplating. The material  120  containing ruthenium provides desirable properties such as wetting and/or adhesion ability. In one example the conductor is drawn into the recess  101 , after heating to a flowable state, due to the chemical affinity between ruthenium and the conductor material chosen. In one example, the conductor  140  comprises, consists, or consists essentially of copper. In one example, the conductor  140  comprises, consists, or consists essentially of a copper alloy. Other examples of conductors may include aluminum, polysilicon, or other suitable conductive materials. 
         [0024]      FIG. 7  shows another removal step, where an upper portion of the conductor  140  has been removed from the top surface  114  of the substrate  100 . In one example the removal operation in  FIG. 7  includes a CMP operation. The conductor  140  may be further processed, such as being subjected to a clean. 
         [0025]    Because the relatively non-reactive and mechanically strong material  120  containing ruthenium has already been removed from the top surface  114 , the subsequent removal of the upper portion of the conductor  140  is relatively straight forward. Differences in removal rate and reactivity between the conductor  140  and the material  120  containing ruthenium are mitigated by removing the respective materials in different operations. Integrity of the material  120  containing ruthenium is preserved during the removal process by the use of the sacrificial protective material. 
         [0026]    An embodiment of an information handling system such as a computer is included in  FIG. 8  to show an embodiment of a high-level device application.  FIG. 8  is a block diagram of an information handling system  800  incorporating a substrate such as a chip or chip assembly  804  that includes an interconnect such as a contact or interconnection line formed according to an embodiment of the invention. For example, the memory device  807  or other chips may include ruthenium containing structures formed according to embodiments of the invention described above. The information handling system  800  shown in  FIG. 8  is merely one example of a system in which the present invention can be used. Other examples include, but are not limited to, personal data assistants (PDAs), cellular telephones, MP3 players, aircraft, satellites, military vehicles, etc. 
         [0027]    In this example, information handling system  800  comprises a data processing system that includes a system bus  802  to couple the various components of the system. System bus  802  provides communications links among the various components of the information handling system  800  and may be implemented as a single bus, as a combination of busses, or in any other suitable manner. 
         [0028]    Chip assembly  804  is coupled to the system bus  802 . Chip assembly  804  may include any circuit or operably compatible combination of circuits. In one embodiment, chip assembly  804  includes a processor  806  that can be of any type. As used herein, “processor” means any type of computational circuit such as, but not limited to, a microprocessor, a microcontroller, a graphics processor, a digital signal processor (DSP), or any other type of processor or processing circuit or cores thereof. Multiple processors such as “multi-core” devices are also within the scope of the invention. 
         [0029]    In one embodiment, a memory device  807 , is included in the chip assembly  804 . Those skilled in the art will recognize that a wide variety of memory device configurations may be used in the chip assembly  804 . Acceptable types of memory chips include, but are not limited to, Dynamic Random Access Memory (DRAMs) such as SDRAMs, SLDRAMs, RDRAMs and other DRAMs. Memory chip  807  can also include non-volatile memory such as NAND memory or NOR memory. 
         [0030]    In one embodiment, additional logic chips  808  other than processor chips are included in the chip assembly  804 . An example of a logic chip  808  other than a processor includes an analog to digital converter. Other circuits on logic chips  808  such as custom circuits, an application-specific integrated circuit (ASIC), etc. are also included in one embodiment of the invention. 
         [0031]    Information handling system  800  may also include an external memory  811 , which can include one or more memory elements, such as one or more hard drives  812 , and/or one or more drives that handle removable media  813  such as floppy diskettes, compact disks (CDs), digital video disks (DVDs), and the like. 
         [0032]    Information handling system  800  may also include a display device  809  such as a monitor, additional peripheral components  810 , such as speakers, etc. and a keyboard and/or controller  814 , which can include a mouse, or any other device that permits a system user to input data into and receive data from the information handling system  800 . 
         [0033]    While a number of embodiments of the invention are described, the above lists are not intended to be exhaustive. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement that is calculated to achieve the same purpose may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of embodiments of the present invention. It is to be understood that the above description is intended to be illustrative and not restrictive. Combinations of the above embodiments, and other embodiments, will be apparent to those of skill in the art upon studying the above description.