Abstract:
Chamferless via structures and methods of manufacture are provided. The method includes: forming at least one self-aligned via within at least dielectric material; plugging the at least one self-aligned via with material; forming a protective sacrificial mask over the material which plugs the at least one self-aligned via, after a recessing process; forming at least one trench within the dielectric material, with the protective sacrificial mask protecting the material during the trench formation; removing the protective sacrificial mask and the material within the at least one self-aligned via to form a wiring via; and filling the wiring via and the at least one trench with conductive material.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to semiconductor structures and, more particularly, to chamferless via structures and methods of manufacture. 
       BACKGROUND 
       [0002]    Integrated circuit(s) typically include a plurality of semiconductor devices and interconnect wiring. Networks of metal interconnect wiring typically connect the semiconductor devices from a semiconductor portion of a semiconductor substrate. Multiple levels of metal interconnect wiring above the semiconductor portion of the semiconductor substrate are connected together to form a back-end-of-the line (BEOL) interconnect structure. 
         [0003]    Several developments have contributed to increased performance of contemporary ICs. One such development is technology scaling which results in higher integration of structures, e.g., transistors, wiring, etc. However, technology scaling has posed several challenges including, e.g., process variation, stricter design rules, etc. For example, in trench first via last metal hardmask integration schemes, excessive non-self-aligned via (Non-SAV) chamfering can result during trench formation. This integration scheme results in chamfering which is very difficult to control, and can result in poor yields, jagged surfaces and shorting issues. 
       SUMMARY 
       [0004]    In an aspect of the invention, a method comprises: forming at least one self-aligned via within at least dielectric material; plugging the at least one self-aligned via with material; forming a protective sacrificial mask over the material which plugs the at least one self-aligned via, after a recessing process; forming at least one trench within the dielectric material, with the protective sacrificial mask protecting the material during the trench formation; removing the protective sacrificial mask and the material within the at least one self-aligned via to form a wiring via; and filling the wiring via and the at least one trench with conductive material. 
         [0005]    In an aspect of the invention, a method comprises: forming at least one self-aligned via within an optical planar layer and ultra low-k dielectric material; plugging the at least one self-aligned via with material selective to the ultra low-k dielectric material; recessing the material; removing the optical planar layer and underlying etch stop material to expose the ultra low-k dielectric material, wherein the removing step further recesses the material to below spacers formed above the ultra low-k dielectric material; forming a protective sacrificial mask over the material which plugs the at least one self-aligned via; forming at least one trench within the dielectric material, with the protective sacrificial mask protecting the material during the forming of the at least one trench; removing the protective sacrificial mask and the material within the at least one self-aligned via to form a wiring via; and filling the wiring via and the at least one trench with conductive material. 
         [0006]    In an aspect of the invention, a structure comprises a conductive line and via formed in a low-k dielectric material wherein the via is chamferless and the low-k dielectric material is continuous with no etch stop layer at a line/via junction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    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. 
           [0008]    Prior to discussing the particulars of each of the figures, it is to be noted that each set of figures include a cross sectional view of a structure along a self-aligned via (SAV) direction, e.g.,  FIGS. 1A, 2A, 3A, 4A, 5A, 6A, 7A, 8A, 9A and 10A , and a set of figures including a cross sectional view of a structure along a non-self-aligned via (non-SAV) direction, e.g.,  FIGS. 1B, 2B, 3B, 4B, 5B, 6B, 7B, 8B, 9B and 10B . 
           [0009]      FIG. 1A  shows a cross sectional view of a beginning structure and respective fabrication processes along a self-aligned via (SAV) direction; whereas,  FIG. 1B  shows a cross sectional view of the structure of  FIG. 1A  along a non-SAV direction, in accordance with aspects of the invention. 
           [0010]      FIGS. 2A and 2B  show structures with openings and respective fabrication processes in accordance with aspects of the invention. 
           [0011]      FIGS. 3A and 3B  show structures with via fill material within the openings and respective fabrication processes in accordance with aspects of the invention. 
           [0012]      FIGS. 4A and 4B  show the via fill material recessed within the openings and respective fabrication processes in accordance with aspects of the invention. 
           [0013]      FIGS. 5A and 5B  show additional structures within the fabrication processes, and respective fabrication processes in accordance with aspects of the invention. 
           [0014]      FIGS. 6A and 6B  show additional structures within the fabrication processes, and respective fabrication processes in accordance with aspects of the invention. 
           [0015]      FIGS. 7A and 7B  shows a protective sacrificial mask on exposed portions of the via fill material amongst other structures, and respective fabrication processes in accordance with aspects of the invention. 
           [0016]      FIGS. 8A and 8B  show a plurality of trenches within dielectric material, and respective fabrication processes in accordance with aspects of the invention. 
           [0017]      FIGS. 9A and 9B  show chamferless wiring vias, and respective fabrication processes in accordance with aspects of the invention. 
           [0018]      FIGS. 10A and 10B  show metal fill material within the chamferless wiring vias (wiring lines), and respective fabrication processes in accordance with aspects of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    The invention relates to semiconductor structures and, more particularly, to chamferless via structures and methods of manufacture. In embodiments, the present invention implements a protective sacrificial mask, e.g., Ruthinium, in order to protect a via structure during back end of the line (BEOL) processing. In embodiments, the Ruthinium or other protective sacrificial mask material described herein will protect gap fill material and underlying materials, e.g., Titanium Nitride (TiN) hardmask, during trench interlevel dielectric (ILD) reactive ion etching (RIE) processes. The protection provided by the protective sacrificial mask will reduce via CD (critical dimension) increase and improve non-SAV (self-aligned via) angle and chamfer roughness caused by ILD damage caused during the trench ILD RIE process. In this way, the processes of the present invention can be used to form a chamferless via structure. 
         [0020]    In embodiments, the fabrication processes include making a chamferless via structure of a dual damascene line/via formed in an ultra-low k dielectric material. In more specific embodiments, the fabrication processes include, amongst other steps, using a gap fill material (e.g., SiARC) in a via opening etched in a low-k dielectric material, while trench openings are subsequently formed in the low-k dielectric material. In embodiments, the gap fill material can be protected with selectively formed Ruthenium, which is used as a mask during trench opening formation processes. Advantageously, the processes described herein will result in final wiring structures comprising a dual damascene line and via formed in a low-k dielectric wherein the via is chamferless and the low-k dielectric material is continuous (e.g., there is no intermediate etch stop layer at the dual damascene line/via junction). 
         [0021]    The chamferless via structures of the present invention can be manufactured in a number of ways using a number of different tools. In general, though, the methodologies and tools are used to form structures with dimensions in the micrometer and nanometer scale. The methodologies, i.e., technologies, employed to manufacture the chamferless via structures of the present invention have been adopted from integrated circuit (IC) technology. For example, the structures of the present invention are built on wafers and are realized in films of material patterned by photolithographic processes on the top of a wafer. In particular, the fabrication of the chamferless via structures of the present invention uses three basic building blocks: (i) deposition of thin films of material on a substrate, (ii) applying a patterned mask on top of the films by photolithographic imaging, and (iii) etching the films selectively to the mask. 
         [0022]    Now referring to the figures, as shown in  FIGS. 1A and 1B , the structure  10  includes a metal layer  12 , e.g., copper or tungsten, amongst other metal or metal alloys. A block material  14  such as an NBLOK is formed on the metal layer  12 . In embodiments, the block material  14  can be about 20 nm in depth, although other dimensions are contemplated by the present invention. A dielectric material  16  is formed on the block material  14 . In embodiments, the dielectric material  16  is an ultra low-k dielectric material known to those of ordinary skill in the art. The dielectric material  16  can be formed to a thickness of about 100 nm; although other dimensions are also contemplated by the present invention. 
         [0023]    Still referring to  FIGS. 1A and 1B , a thin film of etch stop layer or hardmask material  18 , e.g., alloy material, is deposited on the dielectric material  16 . In embodiments, the thin film of etch stop layer or hardmask material  18  can be SiNH deposited to a thickness of about 10 nm; although other dimensions are also contemplated by the present invention. Another hardmask  20 , e.g., TiN, is deposited on the thin film of etch stop layer or hardmask material  18 , followed by the formation of spacers  22 , e.g., nitride material. The hardmask  20  and spacers  22  can be formed using conventional deposition processes, e.g., CVD, followed by lithography and etching, e.g., RIE, processes known to those of ordinary skill in the art such that further description is not required for an understanding of the invention. The lithography and etching process will result in a self-aligned via structure as described herein. 
         [0024]    Still referring to  FIGS. 1A and 1B , an optical planarization layer (OPL)  24  can be deposited over the structure, e.g., hardmask  20  and spacers  22  and exposed portions of the thin film of etch stop layer or hardmask  18 . In embodiments, the OPL  24  can be spun on and baked, or can be deposited by CVD. OPL can be baked at lower temperatures, such as 150-200° C. to avoid damaging any other materials. A hardmask  26  is deposited on the OPL  24 . In embodiments, the hardmask  26  is a low temperature oxide deposited to a thickness of about 30 nm; although other dimensions are also contemplated by the present invention. 
         [0025]    The hardmask patterned to form openings  28 . In embodiments, the openings  28  are formed by conventional lithography and etching processes. For example, a resist is formed over the hardmask  26 , which is exposed to energy (light) to form a pattern (openings). A reactive ion etching (RIE) process is then performed through the openings of the resist to form the openings  28  in the hardmask  26 . The resist is then removed using conventional stripants or oxygen ashing processes. 
         [0026]    As shown in  FIGS. 2A and 2B , openings  30  (e.g., self-aligned via structures  30 ), are formed in the materials to the underlying metal layer  12 . As shown in  FIG. 2A , the self-aligned via structures  30  extend between the spacers  22  and the hardmask  20 , and expose the underlying metal layer  12 . The self-aligned via structures  30  can be formed through several selective etch chemistries, selective for each of the materials. The different chemistries will be selective to different materials as should be known to those of ordinary skill in the art such that further description is not required for an understanding of the invention. 
         [0027]    In embodiments, the different etching steps can be provided within the same etch chamber, as an example. For example, a first etch chemistry is used to remove portions of the OPL  24 . A second etch chemistry is then used to remove the etch stop layer  18 , with subsequent etch chemistries used to remove the dielectric layer  16  and hardmask layer  14 , respectively. In this way, the underlying metal layer  12  can be exposed. 
         [0028]    In embodiments, the self-aligned via structures  30  can undergo a wet etching process to remove any residual RIE residue to improve fill adhesion. In embodiments, the self-aligned via structures  30  can have an aspect ratio of, e.g., about 15:1. For example, in embodiments, the dimensions of the self-aligned via structures  30  in the SAN/direction can be about 20 nm, whereas, the dimensions of the self-aligned via structures  30  in the non-SAY direction can be about 30 nm. 
         [0029]    in  FIGS. 3A and 3B , a via fill material  32  is deposited within the self-aligned via structures  30 . During this deposition process, residual via fill material  32  may form on the surface of the OPL  24 . In embodiments, the via fill material  32  can be SiARC (e.g., antireflective coating of Si). In alternate embodiments, the via fill material  32  can be an OPL. In still additional alternate embodiments, the via fill material  32  can be a spin on material, e.g., spin on glass. In still additional alternate embodiments, the via fill material  32  can be an oxide such as an ultra porous material, e.g., ultra low-k dielectric material such as SiCOH. 
         [0030]    In embodiments, the via fill material  32  should have a viscosity that allows complete fill of the self-aligned via structures  30 . In alternate embodiments, the via fill material  32  may not completely fill the self-aligned via structures  30 . For example, air gaps can be provided below the etch stop layer  18 , e.g., at the dielectric layer  16 . In embodiments, the via fill material  32  does not need to be planarized or conform to photolithography specifications. 
         [0031]    In  FIGS. 4A and 4B , the via fill material  32  is etched slightly to form recesses  34  within the OPL  24 . In embodiments, the recesses  34  can be tuned to specific dimensions based on etch rates and chemistries. Following the recess of the via fill material  32 , the OPL material and additional portions of the via fill material  32  are removed as shown in  FIGS. 5A and 5B . These materials can be removed by selective etching chemistries as described herein. 
         [0032]    In  FIGS. 6A and 6B , any exposed etch stop layer material  18  can be removed using a selective etch chemistry. This selective etch chemistry can also remove portions of the via fill material  32  to below the spacers  22 . In embodiments, the removal of the etch stop layer material  18  will allow the formation of a trench structure in subsequent fabrication processes. 
         [0033]    In  FIGS. 7A and 7B , a protective sacrificial mask  34  is formed on the exposed portions of the via fill material  32 . The protective sacrificial mask  34  can also be formed on exposed portions of the etch stop layer  18  and hardmask  20 . In embodiments, the protective sacrificial mask  34  is a selective deposition material, which does not deposit or adhere to oxide, e.g., dielectric material  16 . In this way, the dielectric material  16  remains exposed for future trench formation processing. 
         [0034]    By way of example and as discovered by the inventors, the protective sacrificial mask  34  can be Ruthinium. Advantageously, Ruthinium does not adhere to oxide, e.g., dielectric material  16 , but will adhere to organics and metals. Also, Ruthinium has been found to be resistant to etch chemistries used for trench formation processes. In embodiments, the protective sacrificial mask  34  can be formed by an atomic layer deposition (ALD) process, controllable to 1 nm. 
         [0035]    As shown in  FIGS. 8A and 8B , the exposed dielectric material  16  undergoes etching processes to form a trench  36 . In embodiments, the protective sacrificial mask  34  will protect the underlying materials and, more specifically, the self-aligned via structures  30 . In this way, the self-aligned via structures  30  will not become damaged during processing of the trenches  36 . The trenches  36  can have a depth of about 60 nm to about 80 nm; although other dimensions are also contemplated by the present invention. 
         [0036]    As shown in  FIGS. 9A and 9B , the protective sacrificial mask  34 , the etch stop layer  18  and hardmask  20  can be removed, followed by removal of the via fill material  32 . In embodiments, the via fill material  32  will protect the underlying metal layer  12  during the removal of the protective sacrificial mask  34 , etch stop layer  18  and hardmask  20 , allowing for aggressive removal of the etch stop layer  18  and hardmask  20 . In embodiments, the protective sacrificial mask  34 , etch stop layer  18  and hardmask  20  can be removed using a wet etch process. Moreover, in embodiments, the via fill material  32  can be removed by a dry or wet etch removal process. In embodiments, the via fill material  32  can also be removed with the removal of the etch stop layer  18  and/or hardmask  20 . In any scenario, the removal of the via fill material  32  will form a wiring via  38  with vertical sidewalls, e.g., chamferless sidewalls. By way of example, the sidewall angle would be greater than 85°, and preferably has a constant angle in the dielectric material  16 . In this way, the wiring via  38  would be chamferless. 
         [0037]    As shown in  FIGS. 10A and 10B , metal fill material  38  is formed within the wiring via  38  and the trench  36 . The metal fill material  38  can be a copper material formed by an electroplating process as is well known to those of skill in the art. In embodiments, prior to the metal fill process, any residual RIE material can be cleaned from the wiring via  38  and the trenches  36  using a wet etch process, followed by deposition of a barrier and seed layer. The barrier layer can prevent metal diffusion into the ultra-low-k dielectric and it can promote seed layer adhesion. After the deposition of a barrier and seed layer, the electroplating process can commence to form metal lines, e.g., metal fill material  38 Any residual metal fill material  38  on a surface of the structure can be removed by a conventional planarization process, e.g., chemical mechanical polishing (CMP). 
         [0038]    The method(s) as described above is used in the fabrication of integrated circuit chips. 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, ranging from toys and other low-end applications to advanced computer products having a display, a keyboard or other input device, and a central processor. 
         [0039]    The descriptions of the various embodiments of the present invention have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.