Abstract:
A redundant diffusion barrier structure and method of fabricated is provided for interconnect and wiring applications. The structure can also be a design structure. The structure includes a first liner lining at least one of a trench and a via and a second liner deposited over the first liner. The second liner comprises RuX. X is at least one of Boron and Phosphorous. The structure comprises a metal deposited on the second liner in the at least one trench and via to form a metal interconnect or wiring.

Description:
FIELD OF THE INVENTION 
     The present invention relates to integrated circuits (ICs), a design structure and a method of manufacturing the IC and, more particularly, to a redundant diffusion barrier structure for interconnect and wiring applications, a design structure and a method of manufacturing the IC. 
     BACKGROUND 
     The fabrication of integrated circuits, e.g., microelectronic devices, includes the building of multilevel wiring interconnect regions within the devices. To fabricate such structures, one or more interconnections are formed between first and second level wiring lines. To form these interconnects, openings are formed in the dielectric layer using conventional lithograhic and etching processes. The openings are filled with a metal to form the interconnect. This metal is typically Cu or AlCu. To continue with the build, the above process continues with the deposition of additional interlevel dielectric (ILD) layers to accommodate further processing of the integrated circuit. 
     The dielectric layers usually consists of a layer of oxide such, for example, as silicon oxides. However, it has been found that Cu metal introduces many integration challenges in combination with the dielectric layers. For example, copper is known to be a fast diffuser through dielectrics, especially in silicon dioxide. This leads to integration difficulty for copper damascene structures. That is, the copper will out diffuse into the dielectric potentially destroying the device. Thus, if copper diffuses from the interconnect wiring into the underlying active electrical devices, then these devices can fail to operate. 
     In an attempt to solve this problem, a dielectric diffusion barrier is placed in the via or trench prior to the deposition of the copper conductor. The standard industry approach for copper interconnects is to use barrier metals such as titanium nitride (TiN), tantalum (Ta), tantalum nitride (TaN) and/or tungsten nitride (WN) to prevent copper diffusion from the wires. However, it has been found that even a thick layer of such materials or combinations of these materials cannot completely top the out diffusion of copper. This poses a challenging task to designers as technology scales. 
     Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove. 
     SUMMARY 
     In an aspect of the invention, a structure comprises a first liner lining at least one of a trench and a via and a second liner deposited over the first liner. The second liner comprises RuX. X is at least one of Boron and Phosphorous. The structure comprises a metal deposited on the second liner in the at least one trench and via to form a metal interconnect or wiring. 
     In another aspect of the invention, a method of fabricating an interconnect or wiring structure comprises depositing a first liner on walls of a trench and via and depositing a second liner on the first liner. The second liner comprises RuX, where X is at least one of Boron and Phosphorous. The method further comprises depositing a metal interconnect or wiring on the second liner. 
     In a further aspect of the invention, a method of forming a wiring or interconnect structure, comprises: forming at least a trench in a dielectric material; lining the trench with one of TiN, TaN, WN, RuTa(N) and RuN; depositing a redundant liner on the lining, the redundant liner comprising RuX, where X is at least one of Boron and Phosphorous; and depositing Cu or AlCu over the redundant liner to form a metal interconnect or wiring, wherein the redundant liner prevents out diffusing of copper into the dielectric. 
     In yet a still further aspect of the invention, a design structure is embodied in a machine-readable medium for designing, manufacturing, or testing an integrated circuit. The design structure includes a first liner lining at least one of a trench and a via; a second liner deposited over the first liner, the second liner comprising RuX, where X is at least one of Boron and Phosphorous; and a metal deposited on the second liner in the at least one trench and via to form a metal interconnect or wiring. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The present invention is described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention. 
         FIGS. 1-7  show fabrication processes and respective structures for manufacturing a structure in accordance with the present invention; 
         FIGS. 8   a - 8   d  shows different lining variants according to aspects of the invention; 
         FIG. 9  shows a final structure and respective fabrication processes for manufacturing a structure in accordance with the present invention; and 
         FIG. 10  is a flow diagram of a design process used in semiconductor design, manufacture, and/or test. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates to integrated circuits (ICs), a design structure and a method of manufacturing the IC and, more particularly, to a redundant diffusion barrier structure for interconnect and wiring applications, a design structure and a method of manufacturing the IC. In implementation, the present invention provides a redundant diffusion barrier layer to ensure that copper does not out diffuse from metal wiring and interconnect structures. For example, in embodiments, a second (redundant) liner is lined in a trench or via, which is subsequently processed to be a wiring or interconnect structure. This redundant liner acts as a diffusion barrier layer against copper out diffusing into the structure. The second liner may be, for example, Ru(P), Ru(B) or Ru(P, B). This redundant liner provides improved device reliability. 
       FIG. 1  shows a beginning structure in accordance with the invention. The beginning structure includes a dielectric layer  10 . The dielectric layer  10  may be, for example, SiO 2 , SiCOH, SiLK or other known dielectric materials. The dielectric layer  10  may be either porous or dense, and may be applied by a spin on process or chemical vapor deposition (CVD) process. 
     A trench  12  is processed in the dielectric layer  10 . As should be understood by those of skill in the art, more than one trench can be formed in the dielectric layer  10 ; however, for ease of discussion only a single trench is discussed herein. The trench  12  may be formed using any conventional lithography and etching process. For example, a mask (not shown) may be applied over the dielectric layer  10  and exposed to light to form openings. A reactive ion etching (RIE) may then be performed to form the trench(es)  12 . 
       FIG. 2  shows a beginning fabrication process for metallization and chemical mechanical polishing (CMP) processes. More specifically, in  FIG. 2  a liner  14  is deposited in the trench  12 . The liner  14  may be a barrier layer of TiN, TaN, WN, RuTa(N) or RuN, for example. The deposition process may be a conventional deposition process such as, for example, CVD, physical vapor deposition (PVD) or atomic layer deposition (ALD). In embodiments, the liner  12  can have a thickness of about 10 Å to 200 Å; although other dimensions are contemplated by the invention. As discussed below, a redundant liner (also depicted as reference numeral  14 ) can be deposited in the trench to act as a redundant barrier. 
     In  FIG. 3 , a wiring structure  16  such as, for example, Cu or Cu(Al), is deposited over the liner  14 . The structure is then planarized using, for example, CMP processes. 
     In  FIG. 4 , a cap  18  is deposited on the structure of  FIG. 3 . The cap  18  can be, for example, an NBLok, SiC, Si 4 NH 3  or SiO 2 . The cap  18  can be deposited using any conventional deposition processes, as discussed herein, and known to those of ordinary skill in the art. 
     In  FIG. 5 , a dielectric layer  20  is deposited on the cap  18 . The dielectric layer  20  may be, for example, SiO 2 , SiCOH, SiLK or other known dielectric materials. The dielectric layer  20  may be either porous or dense, and may be applied by a spin on process or chemical vapor deposition (CVD) process. 
     Still referring to  FIG. 5 , a via  22   a  and trenches  22   b  are formed in the dielectric layer  20  using conventional damascene patterning processes. Those of skill in the art will realize that more than one via and two trenches or any combination thereof may be formed in the structure depending on the specific design parameters. However, for the purposes of discussion only, a single via  22   a  and two trenches  22   b  are discussed herein, without providing a limitation to the present invention. 
     As should be understood by those of skill in the art, the trenches and via may be formed using any conventional lithography and etching process. Illustratively, a mask (not shown) may be applied over the dielectric layer  20  and exposed to light to form openings of a first size for the via  22   a . A reactive ion etching (RIE) may then be performed to form the via  22   a  of the first size. The via  22   a  extends to the underlying metal wiring layer  16 . This process can be repeated to form the trenches  22   b  of a second, larger size, with such processes being well known in the art that further explanation is not required herein for an understanding of the invention. 
     As shown in  6 , a liner  24  is deposited on the walls of the via  22  and trenches  22   b . The liner  24  is a first barrier layer and can be composed of, for example, Ta(N), Ti(N) and W(N). The liner  24  can range in thickness from about 10 Å to 100 Å; although other dimensions are contemplated by the invention. The liner  24  can be deposited using any conventional deposition method, known to those of skill in the art. 
     In  FIG. 7 , a redundant liner  26  is deposited on the liner  24 , using conventional deposition processes known to those of skill in the art. The redundant liner  26  can be Ru(P), Ru(B) or Ru(P, B), where the component of (P), (B) or (P) (B) contacts and adjoins the liner  24 . The liner  26  can range in thickness from about 10 Å to 100 Å; although other dimensions are contemplated by the invention. 
     It should be understood by those of skill in the art that the use of Ru alone is not a good diffusion barrier. As such, the copper surface of the interconnect or wiring structure may out diffuse into the dielectric layer  20 . However, it has been found that using Ru(P), Ru(B) or Ru(P, B) is a superior diffusion barrier which does not allow the interconnect or wiring material (e.g., copper) to out diffuse into the dielectric. In embodiments, the Ru (P, B) can be a uniform film or have decreasing P, B concentrations. In the latter case, the interface between the liner  24  and liner  26  has the highest B, P concentration, and the surface of the liner  26  can be pure Ru. 
       FIGS. 8   a - 8   d  show different variants of Ru(P), Ru(B) or Ru(P, B) as contemplated by the invention. For example, as shown in  FIG. 8   a , in aspects of the invention, the liner  26  comprises a top layer of Ru and a bottom layer (i.e., the surface that contacts the liner  24 ) of Ru(P), Ru(B) or Ru(P, B). In embodiments, the Ru layer and the layer of Ru(P), Ru(B) or Ru(P, B) are each about 20 Å or less and can range from about 10 Å to 20 Å. In further embodiments, the percent concentration of (P), (B) or (P)(B) ranges from about 1% to 30%. 
       FIG. 8   b  shows a further aspect of the invention, where the liner  26  is a layer of Ru(P), Ru(B) or Ru(P, B), with the (P), (B) or (P)(B) component gradually decreasing in percentage concentration as it is deposited on the liner  24 . For example, in implementation, the (P), (B) or (P)(B) can be introduced during the deposition process by initially having a high gas flow of (P), (B) or (P)(B) such that the bottom portion (e.g., the portion that is closest to the liner  24 ) of the liner  26  is, for example, 30% of (P), (B) or (P)(B) and then decreasing the gas flow of (P), (B), or (P)(B) such that the upper portion is, for example, about 0% of (P), (B) or (P)(B), with a gradual decrease therebetween. The concentration of (P), (B) or (P)(B) can be increased or decreased by adjusting the gas flow. 
       FIG. 8   c  shows a further aspect of the invention, where the liner  26  is a single layer of Ru(P), Ru(B) or Ru(P, B), with the (P), (B) or (P)(B) component having a substantially constant percentage concentration throughout the entire liner  26 . For example, in implementation, the percentage concentration of (P), (B) or (P)(B) can range from about 1% to 30%, in relation to the entire structure. 
       FIG. 8   d  shows a further aspect of the invention, where the liner  26  is a layered structure. For example, in one aspect, the layers may alternate from closest to the liner  24  between (i) Ru(P) and Ru, (ii) Ru(B) and Ru, and (iii) Ru(P, B) and Ru. In embodiments, the percentage concentration of (P), (B) or (P)(B) can range from about 0% to 30%, in relation to the entire layered structure. The thickness of the liner  26  can be about 30 Å to 50 Å, with each layer ranging from about less than 10 Å and preferably about 1 Å to 2 Å. 
       FIG. 9  shows a final structure and respective processing steps in accordance with an aspect of the invention. As shown in  FIG. 9 , a metal  28  is deposited in the vias and trenches, over the liner  26 . The metal  28  can be, for example, Cu or AlCu. The metal  28  can be deposited in a conventional manner as described herein, and can then be planarized using, for example, CMP processes. As should now be understood, the liner  26  of the present invention will prevent out diffusion of copper into the dielectric thereby ensuring device reliability. 
     DESIGN STRUCTURE 
       FIG. 10  shows a block diagram of an exemplary design flow  900  used for example, in semiconductor IC logic design, simulation, test, layout, and manufacture. Design flow  900  includes processes and mechanisms for processing design structures to generate logically or otherwise functionally equivalent representations of the embodiments of the invention shown in  FIGS. 7 and 9 . The design structures processed and/or generated by design flow  900  may be encoded on machine-readable transmission or storage media to include data and/or instructions that when executed or otherwise processed on a data processing system generate a logically, structurally, or otherwise functionally equivalent representation of hardware components, circuits, devices, or systems. 
       FIG. 10  illustrates multiple such design structures including an input design structure  920  that is preferably processed by a design process  910 . Design structure  920  may be a logical simulation design structure generated and processed by design process  910  to produce a logically equivalent functional representation of a hardware device. Design structure  920  may also or alternatively comprise data and/or program instructions that when processed by design process  910 , generate a functional representation of the physical structure of a hardware device. Whether representing functional and/or structural design features, design structure  920  may be generated using electronic computer-aided design (ECAD) such as implemented by a core developer/designer. When encoded on a machine-readable data transmission or storage medium, design structure  920  may be accessed and processed by one or more hardware and/or software modules within design process  910  to simulate or otherwise functionally represent an electronic component, circuit, electronic or logic module, apparatus, device, or system such as those shown in  FIGS. 7 and 9 . As such, design structure  920  may comprise files or other data structures including human and/or machine-readable source code, compiled structures, and computer-executable code structures that when processed by a design or simulation data processing system, functionally simulate or otherwise represent circuits or other levels of hardware logic design. Such data structures may include hardware-description language (HDL) design entities or other data structures conforming to and/or compatible with lower-level HDL design languages such as Verilog and VHDL, and/or higher level design languages such as C or C++. 
     Design process  910  preferably employs and incorporates hardware and/or software modules for synthesizing, translating, or otherwise processing a design/simulation functional equivalent of the components, circuits, devices, or logic structures shown in  FIGS. 7 and 9  to generate a netlist  980  which may contain design structures such as design structure  920 . Netlist  980  may comprise, for example, compiled or otherwise processed data structures representing a list of wires, discrete components, logic gates, control circuits, I/O devices, models, etc. that describes the connections to other elements and circuits in an integrated circuit design. Netlist  980  may be synthesized using an iterative process in which netlist  980  is resynthesized one or more times depending on design specifications and parameters for the device. As with other design structure types described herein, netlist  980  may be recorded on a machine-readable data storage medium. The medium may be a non-volatile storage medium such as a magnetic or optical disk drive, a compact flash, or other flash memory. Additionally, or in the alternative, the medium may be a system or cache memory, buffer space, or electrically or optically conductive devices and materials on which data packets may be transmitted and intermediately stored via the Internet, or other networking suitable means. 
     Design process  910  may include hardware and software modules for processing a variety of input data structure types including netlist  980 . Such data structure types may reside, for example, within library elements  930  and include a set of commonly used elements, circuits, and devices, including models, layouts, and symbolic representations, for a given manufacturing technology (e.g., different technology nodes, 32 nm, 45 nm, 90 nm, etc.). The data structure types may further include design specifications  940 , characterization data  950 , verification data  960 , design rules  970 , and test data files  985  which may include input test patterns, output test results, and other testing information. Design process  910  may further include modules for performing standard circuit design processes such as timing analysis, verification, design rule checking, place and route operations, etc. 
     Design process  910  employs and incorporates well-known logic and physical design tools such as HDL compilers and simulation model build tools to process design structure  920  together with some or all of the depicted supporting data structures to generate a second design structure  990 . Similar to design structure  920 , design structure  990  preferably comprises one or more files, data structures, or other computer-encoded data or instructions that reside on transmission or data storage media and that when processed by an ECAD system generate a logically or otherwise functionally equivalent form of one or more of the embodiments of the invention shown in  FIGS. 7 and 9 . In one embodiment, design structure  990  may comprise a compiled, executable HDL simulation model that functionally simulates the devices shown in  FIGS. 7 and 9 . 
     Design structure  990  may also employ a data format used for the exchange of layout data of integrated circuits and/or symbolic data format (e.g. information stored in a GDSII (GDS2), GL1, OASIS, map files, or any other suitable format for storing such design data structures). Design structure  990  may comprise information such as, for example, symbolic data, map files, test data files, design content files, manufacturing data, layout parameters, wires, levels of metal, vias, shapes, data for routing through the manufacturing line, and any other data processed by semiconductor manufacturing tools to fabricate embodiments of the invention as shown in  FIGS. 7 and 9 . Design structure  990  may then proceed to a stage  995  where, for example, design structure  990 : proceeds to tape-out, is released to manufacturing, is released to a mask house, is sent to another design house, is sent back to the customer, etc. 
     The resulting integrated circuit chips can be distributed by the fabricator in raw wafer form (that is, as a single wafer that has multiple unpackaged chips), as a bare die, or in a packaged form. In the latter case the chip is mounted in a single chip package (such as a plastic carrier, with leads that are affixed to a motherboard or other higher level carrier) or in a multichip package (such as a ceramic carrier that has either or both surface interconnections or buried interconnections). In any case the chip is then integrated with other chips, discrete circuit elements, and/or other signal processing devices as part of either (a) an intermediate product, such as a motherboard, or (b) an end product. The end product can be any product that includes integrated circuit chips. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     The corresponding structures, materials, acts, and equivalents of all means or step plus function elements, if any, in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form 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 invention. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.