Abstract:
A first photoresist layer is patterned with a first pattern that includes an opening in a region between areas of two adjacent via holes to be formed. The opening in the first photoresist is transferred into a template layer to form a line trench therein. The lateral dimension of the trench is reduced by depositing a contiguous spacer layer that does not fill the trench completely. An etch-resistant material layer is conformally deposited and fills the trench, and is subsequently recessed to form an etch-resistant material portion filling the trench. A second photoresist layer is applied and patterned with a second pattern, which includes an opening that includes areas of two via holes and an area therebetween. A composite pattern of an intersection of the second pattern and the complement of the pattern of the etch-resistant material portion is transferred through the template layer.

Description:
BACKGROUND 
       [0001]    The present disclosure relates to semiconductor processing methods, and particularly to methods for low damage etch process for low dielectric constant materials, and structures for effecting the same. 
         [0002]    In a dense contact via hole array, the pitch of the contact via holes is limited by lithographic resolution. The smaller the distance between a pair of contact via holes is, the greater the probability that a physical pattern is bridged, either at a lithographic step or after a pattern transfer etch. While multi-mask patterning schemes that employ multiple lithographic masks can alleviate bridging of contact via holes as printed in each developed photoresist layer, an adjacent pair of contact via holes is prone to bridging upon transfer of multiple lithographic patterns in the photoresist layers into an underlying layer. Thus, via hole bridging poses a severe limitation in scaling of dimensions in a dense contact via hole array. 
       SUMMARY 
       [0003]    A pair of laterally spaced contact via holes is formed employing two lithographic masks and a self-aligned etch-resistant material portion. A first photoresist layer is patterned with a first pattern that includes an opening in a region between areas of two adjacent via holes to be formed. The opening in the first photoresist is transferred into a template layer to form a line trench therein. The lateral dimension of the trench is reduced by depositing a contiguous spacer layer that does not fill the trench completely. An etch-resistant material layer is conformally deposited and fills the trench, and is subsequently recessed to form an etch-resistant material portion filling the trench. A second photoresist layer is applied and patterned with a second pattern, which includes an opening that includes areas of two via holes and an area therebetween. A composite pattern of an intersection of the second pattern and the complement of the pattern of the etch-resistant material portion is transferred through the template layer and through an underlying layer in a subsequent pattern transfer etch. 
         [0004]    According to an aspect of the present disclosure, a method of forming a patterned structure is provided, which includes: forming a line trench having a first pattern in an upper portion of a template layer; forming a contiguous spacer layer within the line trench and over a top surface of the template layer; forming an etch-resistant material portion within the line trench and on sidewalls of the contiguous spacer layer; forming a patterned layer over the etch-resistant material portion and the template layer, the patterned layer having a second pattern including an opening therein; and transferring a composite pattern of an intersection of the second pattern and a complement of a pattern of the etch-resistant material portion into the template layer. 
         [0005]    According to another aspect of the present disclosure, a structure is provided, which includes: a stack of a template layer and a contiguous spacer layer; an etch-resistant material portion overlying a recessed portion of the stack; and a pair of via structures embedded within the stack and laterally spaced by the etch-resistant material portion and the recessed portion of the stack. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0006]      FIG. 1A  is a top-down view of a first exemplary structure after application of a first photoresist layer according to a first embodiment of the present disclosure. 
           [0007]      FIG. 1B  is a vertical cross-sectional view of the first exemplary structure of  FIG. 1A . 
           [0008]      FIG. 2A  is a top-down view of the first exemplary structure after patterning the first photoresist layer with a first pattern according to the first embodiment of the present disclosure. 
           [0009]      FIG. 2B  is a vertical cross-sectional view of the first exemplary structure of  FIG. 2A . 
           [0010]      FIG. 3A  is a top-down view of the first exemplary structure after transfer of the pattern in the first photoresist layer into a template layer according to the first embodiment of the present disclosure. 
           [0011]      FIG. 3B  is a vertical cross-sectional view of the first exemplary structure of  FIG. 3A . 
           [0012]      FIG. 4A  is a top-down view of the first exemplary structure after formation of a contiguous spacer layer according to the first embodiment of the present disclosure. 
           [0013]      FIG. 4B  is a vertical cross-sectional view of the first exemplary structure of  FIG. 4A . 
           [0014]      FIG. 5A  is a top-down view of the first exemplary structure after formation of an etch-resistant material layer according to the first embodiment of the present disclosure. 
           [0015]      FIG. 5B  is a vertical cross-sectional view of the first exemplary structure of  FIG. 5A . 
           [0016]      FIG. 6A  is a top-down view of the first exemplary structure after recessing of the etch-resistant material layer to form an etch-resistant material portion according to the first embodiment of the present disclosure. 
           [0017]      FIG. 6B  is a vertical cross-sectional view of the first exemplary structure of  FIG. 6A . 
           [0018]      FIG. 7A  is a top-down view of the first exemplary structure after application of a second photoresist layer according to the first embodiment of the present disclosure. 
           [0019]      FIG. 7B  is a vertical cross-sectional view of the first exemplary structure of  FIG. 7A . 
           [0020]      FIG. 8A  is a top-down view of the first exemplary structure after patterning the second photoresist layer, a second anti-reflective coating layer, and a second organic planarization layer with a second pattern according to the first embodiment of the present disclosure. 
           [0021]      FIG. 8B  is a vertical cross-sectional view of the first exemplary structure of  FIG. 8A . 
           [0022]      FIG. 9A  is a top-down view of the first exemplary structure after transfer of a composite pattern of the intersection of the second pattern and the complement of the pattern of the etch-resistant material portion according to the first embodiment of the present disclosure. 
           [0023]      FIG. 9B  is a vertical cross-sectional view of the first exemplary structure of  FIG. 9A . 
           [0024]      FIG. 10A  is a top-down view of the first exemplary structure after removal of the second photoresist layer, the second ARC layer, and the second organic planarization layer according to the first embodiment of the present disclosure. 
           [0025]      FIG. 10B  is a vertical cross-sectional view of the first exemplary structure of  FIG. 10A . 
           [0026]      FIG. 11A  is a top-down view of the first exemplary structure after formation of a pair of via structures according to the first embodiment of the present disclosure. 
           [0027]      FIG. 11B  is a vertical cross-sectional view of the first exemplary structure of  FIG. 11A . 
           [0028]      FIG. 12A  is a top-down view of a variation of the first exemplary structure according to the first embodiment of the present disclosure. 
           [0029]      FIG. 12B  is a vertical cross-sectional view of the variation of the first exemplary structure of  FIG. 12A . 
           [0030]      FIG. 13A  is a top-down view of a second exemplary structure according to a second embodiment of the present disclosure. 
           [0031]      FIG. 13B  is a vertical cross-sectional view of the second exemplary structure of  FIG. 13A . 
           [0032]      FIG. 14A  is a top-down view of a third exemplary structure after transfer of the pattern in the first photoresist layer into a template layer according to a third embodiment of the present disclosure. 
           [0033]      FIG. 14B  is a vertical cross-sectional view of the third exemplary structure of  FIG. 14A . 
           [0034]      FIG. 15A  is a top-down view of the third exemplary structure after formation of a contiguous spacer layer according to the third embodiment of the present disclosure. 
           [0035]      FIG. 15B  is a vertical cross-sectional view of the third exemplary structure of  FIG. 15A . 
           [0036]      FIG. 16A  is a top-down view of the third exemplary structure after formation of an etch-resistant material layer according to the third embodiment of the present disclosure. 
           [0037]      FIG. 16B  is a vertical cross-sectional view of the third exemplary structure of  FIG. 16A . 
           [0038]      FIG. 17A  is a top-down view of the third exemplary structure after recessing of the etch-resistant material layer to form an etch-resistant material portion according to the third embodiment of the present disclosure. 
           [0039]      FIG. 17B  is a vertical cross-sectional view of the third exemplary structure of  FIG. 17A . 
           [0040]      FIG. 18A  is a top-down view of the third exemplary structure after application of a third photoresist layer according to the third embodiment of the present disclosure. 
           [0041]      FIG. 18B  is a vertical cross-sectional view of the third exemplary structure of  FIG. 18A . 
           [0042]      FIG. 19A  is a top-down view of the third exemplary structure after patterning the third photoresist layer, a third anti-reflective coating layer, and a third organic planarization layer with a third pattern according to the third embodiment of the present disclosure. 
           [0043]      FIG. 19B  is a vertical cross-sectional view of the third exemplary structure of  FIG. 19A . 
           [0044]      FIG. 20A  is a top-down view of the third exemplary structure after transfer of a composite pattern of the intersection of the third pattern and the complement of the pattern of the etch-resistant material portion according to the third embodiment of the present disclosure. 
           [0045]      FIG. 20B  is a vertical cross-sectional view of the third exemplary structure of  FIG. 20A . 
           [0046]      FIG. 21A  is a top-down view of the third exemplary structure after removal of the third photoresist layer, the third ARC layer, and the third organic planarization layer according to the third embodiment of the present disclosure. 
           [0047]      FIG. 21B  is a vertical cross-sectional view of the third exemplary structure of  FIG. 21A . 
           [0048]      FIG. 22A  is a top-down view of the third exemplary structure after formation of a pair of via structures according to the third embodiment of the present disclosure. 
           [0049]      FIG. 22B  is a vertical cross-sectional view of the third exemplary structure of  FIG. 22A . 
           [0050]      FIG. 23A  is a top-down view of a variation of the third exemplary structure according to the third embodiment of the present disclosure. 
           [0051]      FIG. 23B  is a vertical cross-sectional view of the variation of the third exemplary structure of  FIG. 23A . 
           [0052]      FIG. 24A  is a top-down view of a fourth exemplary structure according to a second embodiment of the present disclosure. 
           [0053]      FIG. 24B  is a vertical cross-sectional view of the fourth exemplary structure of  FIG. 24A . 
       
    
    
     DETAILED DESCRIPTION 
       [0054]    As stated above, the present disclosure relates to methods for forming trenches having different widths and the same depth, which are now described in detail with accompanying figures. Throughout the drawings, the same reference numerals or letters are used to designate like or equivalent elements. The drawings are not necessarily drawn to scale. 
         [0055]    Referring to  FIGS. 1A and 1B , a first exemplary structure according to a first embodiment of the present disclosure includes a stack of a substrate layer  10 , at least one underlying material layer, a template layer  40 , and at least one photosensitive-material-including layer. The at least one underlying material layer can include, for example, a dielectric material layer  30 , an optional cap material layer  32 , and an optional hard mask layer  34 . The at least one photosensitive-material-including layer can include, for example, a stack of a first organic planarization layer  42 , a first antireflective coating (ARC) layer  44 , and a first photoresist layer  47 . 
         [0056]    The dielectric material layer  30  includes a dielectric material that can be employed for forming metal interconnect structures therein. For example, the dielectric material layer  30  can include undoped silicon oxide, doped silicon oxide, silicon nitride, silicon oxynitride, non-porous organosilicate glass (OSG), and porous OSG, or a combination thereof. The dielectric material layer  30  can be formed, for example, by chemical vapor deposition (CVD) or spin-coating. The dielectric material layer  30  can have a thickness from 30 nm to 1,000 nm, although lesser and greater thicknesses can also be employed. 
         [0057]    The optional cap material layer  32  can include a dielectric material such as silicon oxide, silicon nitride, silicon oxynitride, a non-porous organosilicate glass, a nitrogen-doped non-porous organosilicate glass, or a combination thereof. In one embodiment, the optional cap material layer  32  can be employed to provide a greater mechanical strength than the material of the dielectric material layer  30  during a subsequent planarization process such as chemical mechanical planarization. Alternately or additionally, the optional cap material layer  32  can be employed to protect the dielectric material layer  30  and structures to be embedded therein from impurities that may diffuse down from upper levels, and can function as a diffusion barrier layer that prevents vertical diffusion of metallic impurities, moisture, or other gaseous impurities. The optional cap material layer  32  can be formed, for example, by chemical vapor deposition (CVD) or atomic layer deposition (ALD). The thickness of the optional cap material layer  32  can be from 2 nm to 30 nm, although lesser and greater thicknesses can also be employed. 
         [0058]    The optional hard mask layer  34  can include a dielectric material or a conductive metallic material. For example, the optional hard mask layer  34  can include a dielectric material such as silicon oxide, silicon nitride, silicon oxynitride, a non-porous organosilicate glass, a nitrogen-doped non-porous organosilicate glass, or a combination thereof, or can include a conductive metallic material such as TiN, TaN, WN, TiC, TaC, WC, or a combination thereof. In one embodiment, the optional hard mask layer  34  can be employed as a disposable or non-disposable stopping layer during a subsequent planarization process. If the optional hard mask layer  34  is a non-disposable dielectric material, the optional hard mask layer  34  can be employed to protect the dielectric material layer  30  and structures to be embedded therein from impurities that may diffuse down from upper levels, and can function as a diffusion barrier layer that prevents vertical diffusion of metallic impurities, moisture, or other gaseous impurities. The optional hard mask layer  32  can include, for example, silicon nitride, silicon oxynitride, a nitrogen-doped organosilicate glass, or a combination thereof. The optional hard mask layer  34  can be formed, for example, by chemical vapor deposition (CVD) or atomic layer deposition (ALD). The thickness of the optional hard mask layer  34  can be from 2 nm to 30 nm, although lesser and greater thicknesses can also be employed. 
         [0059]    The template layer  40  can include a dielectric material, a semiconductor material, and/or a conductive material. In embodiments in which a portion of the template layer  40  remains after formation of a pair of conductive via structures, the template layer  40  includes a dielectric material such as silicon oxide, silicon nitride, silicon oxynitride, porous or non-porous organosilicate glass, or a combination thereof. 
         [0060]    In embodiment in which the entirety of the template layer  40  is subsequently removed during formation of a pair of conductive via structures, for example, by planarization, the template layer  40  can include a dielectric material, a semiconductor material, and/or a conductive material. For example, the template layer  40  can include a dielectric material such as silicon oxide, silicon nitride, silicon oxynitride, porous or non-porous organosilicate glass, or a combination thereof, and/or a semiconductor material such as silicon, germanium, or a compound semiconductor material, and/or a conductive material such as TiN, TaN, WN, TiC, TaC, WC, Al, W, or a combination thereof. 
         [0061]    The template layer  40  can be formed, for example, by chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), spin coating, or a combination thereof. The thickness of the template layer  40  can be from 20 nm to 500 nm, although lesser and greater thicknesses can also be employed. In one embodiment, the template layer  40  can include silicon oxide formed by chemical vapor deposition. 
         [0062]    Each of the layers in the stack of the first organic planarization layer (OPL)  42 , the first antireflective coating (ARC) layer  44 , and the first photoresist layer  47  can be formed by spin coating. The first OPL  42  includes a self-planarizing organic planarization material, which can be a polymer layer with sufficiently low viscosity so that the top surface of the first OPL  42  is a planar horizontal surface. The self-planarizing organic planarization material can be any material employed for an organic planarization layer in trilayer lithography methods known in the art. The thickness of the first OPL  42  can be from 10 nm to 200 nm, although lesser and greater thicknesses can also be employed. 
         [0063]    The first ARC layer  44  is an optional layer, and can be formed, for example, by spin coating. The first ARC layer  44  can include any anti-reflective material known in the art, and can include silicon and/or an organic material. The thickness of the first ARC layer  44  can be from 10 nm to 150 nm, although lesser and greater thicknesses can also be employed. 
         [0064]    The first photoresist layer  47  is applied directly on the first ARC layer  44  or directly on the first OPL  42 , for example, by spin coating. The thickness of the first photoresist layer  47  can be from 200 nm to 600 nm, although lesser and greater thicknesses can also be employed. The first photoresist layer  47  can be a layer of a photoresist sensitive to deep-ultraviolet (DUV) radiation, extreme ultraviolet (EUV), or mid-ultraviolet (MUV) radiation as known in the art, or can be an e-beam resist that is sensitive to radiation of energetic electrons. 
         [0065]    While the present disclosure is described employing the stack of the first OPL  42 , the first ARC layer  44 , and the first photoresist layer  47 , the stack of the first OPL  42 , the first ARC layer  44 , and the first photoresist layer  47  can be replaced with one or more layers that include a photosensitive material as known in the art. 
         [0066]    Referring to  FIGS. 2A and 2B , the first photoresist layer  47  is patterned with a first lithographic pattern by lithographic exposure and development. The first lithographic pattern includes a line portion having a first width w 1  and referred to as a “primary line portion” herein. The first lithographic pattern can further include two additional line portions that are attached to the two ends of the primary line portion and having a lengthwise direction that is perpendicular to the lengthwise direction of the primary line portion. The two additional line portions and the primary line portions can be merged to form a single contiguous opening in the photoresist layer having an overall shaped of an “H.” Thus, the first lithographic pattern including the primary line portion and two adjoined additional line portions is herein referred to as an “H-shaped pattern.” 
         [0067]    Referring to  FIGS. 3A and 3B , the first lithographic pattern in the first photoresist layer  47  is transferred through the first ARC layer  44  and the first OPL  42  by a pattern transfer etch, which can be an anisotropic etch. In one embodiment, the pattern transfer etch can be a reactive ion etch that removes the materials of the first ARC layer  44  and the first OPL  42  employing the first photoresist layer  47  as an etch mask. 
         [0068]    After the top surface of the template layer  40  is physically exposed within an H-shaped opening in the stack of the first OPL  42 , the first ARC layer  44 , and the first photoresist layer  47 , another anisotropic etch process is performed to form a contiguous line trench  51  having an H-shape in an upper portion of the template layer  40 . The anisotropic etch process can include any chemistry that can etch the material of the template layer  40  employing the first photoresist layer  47  as an etch mask. A primary portion of the contiguous line trench  51  underlying the primary line portion of the H-shaped pattern in the first photoresist layer  47  can have a width that is substantially the same as the first width w 1 . The bottom surface of the contiguous line trench  51  may, or may not, extend to the topmost surface of the at least one underlying material layer ( 30 ,  32 ,  34 ). 
         [0069]    Referring to  FIGS. 4A and 4B , the stack of the first photoresist layer  47 , the first ARC layer  44 , and the first OPL  42  are removed, for example, by ashing. A contiguous spacer layer  50  is formed within the contiguous line trench  51  and over the top surface of the template layer  40 . The contiguous spacer layer  50  is formed as a single contiguous layer without any hole therein. In an embodiment in which at least a portion of the template layer  40  remains after subsequent formation of a pair of conductive via structures, the contiguous spacer layer  50  includes a dielectric material such as doped silicon oxide, undoped silicon oxide, silicon nitride, silicon oxynitride, organosilicate glass (OSG), or a combination thereof. 
         [0070]    In an embodiment in which the entirety of the template layer  40  is subsequently removed after formation of a pair of conductive via structures, the contiguous spacer layer  50  can include a dielectric material, a semiconductor material, or a conductive material. 
         [0071]    The material of the contiguous spacer layer  50  can be the same as, or different from, the material of the template layer  40 . The contiguous spacer layer  50  can be formed by a conformal deposition process or by a non-conformal deposition process provided that the sidewall step coverage is non-zero. In one embodiment, the contiguous spacer layer  50  can be formed by a conformal deposition process such as low pressure chemical vapor deposition (LPCVD), and the thickness of the contiguous spacer layer  50  can be the same at all horizontal portions of the contiguous spacer layer  50 . Specifically, the contiguous spacer layer  50  can have the same thickness in the recessed portion of the template layer  40  as in a non-recessed portion of the template layer  50 , i.e., above the topmost surface of the template layer  40  and above the recessed surface of the template layer  40  at the bottom of the contiguous line trench  51 . 
         [0072]    The lateral thickness of vertical portions of the contiguous spacer layer  50  within the recessed portions of the template layer  40  is less than one half of the first thickness w 1  so that the contiguous line trench  51  is not plugged by the contiguous spacer layer  50 . 
         [0073]    In one embodiment, the remaining portion of the contiguous line trench  51  includes a trench portion having a width, which is herein referred to as a second width w 2 , that is less than the first width by twice the width of vertical portions of the contiguous spacer layer  50 . In one embodiment, the second width w 2  can be less than a lithographically printable dimension for deep ultraviolet lithography, i.e., a sublithographic dimension for deep ultraviolet lithography, and the first width w 1  can be a lithographic dimension for deep ultraviolet lithography. 
         [0074]    Referring to  FIGS. 5A and 5B , an etch-resistant material layer  60 L is deposited by a conformal deposition method to fill the contiguous line trench  51 . The material of the etch-resistant material layer  60 L is different from the material of the contiguous spacer layer  50  and from the material of the template layer  40 . Specifically, the material of the etch-resistant material layer  60 L is more etch-resistant to a first etch chemistry to be subsequently employed to etch the contiguous spacer layer  50 , and is more etch-resistant to a second etch chemistry to be subsequently employed to etch the template layer  40 . 
         [0075]    In an embodiment in which at least a portion of the template layer  40  remains after subsequent formation of a pair of conductive via structures, the etch-resistant material layer  60 L includes a dielectric material. For example, the dielectric material of the etch-resistant material layer  60 L can be a dielectric metal oxide having a dielectric constant greater than  8 . 0  and is known as a “high-k gate dielectric material” in the art. The dielectric metal oxide can be formed, for example, by chemical vapor deposition (CVD) or atomic layer deposition (ALD). Alternately, the contiguous spacer layer  50  and the template layer  40  can include organosilicate glass materials, and the etch-resistant material layer  60 L can include silicon oxide, silicon nitride, silicon oxynitride, or a nitrogen-doped organosilicate glass. Yet alternately, the contiguous spacer layer  50  and the template layer  40  can include an organosilicate glass material and/or silicon oxide, and the etch-resistant material layer  60 L can include silicon nitride or silicon oxynitride. 
         [0076]    In an embodiment in which the entirety of the template layer  40  is subsequently removed after formation of a pair of conductive via structures, the etch-resistant material layer  60 L can include a dielectric material or a conductive material. The dielectric material that can be employed for the template layer  40  includes a dielectric metal oxide, silicon oxide, silicon nitride, silicon oxynitride, or a nitrogen-doped organosilicate glass, or a combination thereof. The conductive material that can be employed for the template layer  40  includes a conductive metal nitride such as TiN, TaN, and WN, a conductive metal carbide such as TiC, TaC, WC, an elemental metal such as Al, Cu, W, and combinations and stacks thereof. The conductive material for the template layer  40  can be deposited, for example, by chemical vapor deposition (CVD) or atomic layer deposition (ALD). 
         [0077]    The thickness of the etch-resistant material layer  60 L, as measured above the topmost surface of the contiguous spacer layer  50 , is greater than ½ of the second width w 2 . The sum of the thickness of the contiguous spacer layer  50  and the thickness of the etch-resistant material layer  60 L is greater than ½ of the first width w 1 . 
         [0078]    Referring to  FIG. 6A , the etch-resistant material layer  60 L is vertically recessed employing the contiguous spacer layer  50  as an etch stop layer or as an end-point detection layer. Thus, the etch-resistant material layer  60 L is removed from above the topmost surface of the contiguous spacer layer  50 , while a remaining portion of the etch-resistant material layer  60 L is present below the topmost surface of the contiguous spacer layer  50 . The remaining portion of the etch-resistant material layer  60 L has the second width w 2 , and is herein referred to as an etch-resistant material portion  60 . The etch-resistant material portion  60  is formed within the line trench and on sidewalls of the contiguous spacer layer  50 . In one embodiment, the etch-resistant material portion  60  can have a sub-lithographic lateral dimension for deep ultraviolet lithography. The etch-resistant material portion  60  can have an H-shaped horizontal cross-sectional shape between the plane of the topmost surface of the contiguous spacer layer  50  and the top surface of the recessed portion of the contiguous spacer layer  50 . 
         [0079]    Referring to  FIGS. 7A and 7B , a stack of a second organic planarization layer (OPL)  72 , a second antireflective coating (ARC) layer  74 , and a second photoresist layer  77  is formed, for example, by spin coating. The second OPL  72  can include the same type of material as the first OPL  72 , and can have the same thickness range as the first OPL  42 . The second ARC layer  74  can have the same type of material as the first ARC layer  44 , and can have the same thickness range as the first ARC layer  44 . The second photoresist layer  77  can have the same type of material as the first photoresist layer  47 , and can have the same thickness range as the first photoresist layer  47 . 
         [0080]    While the present disclosure is described employing the stack of the second OPL  72 , the second ARC layer  74 , and the second photoresist layer  77 , the stack of the second OPL  72 , the second ARC layer  74 , and the second photoresist layer  77  can be replaced with one or more layers that include a photosensitive material as known in the art. 
         [0081]    Referring to  FIGS. 8A and 8B , the stack of the second photoresist layer  77 , the second ARC layer  74 , and the second OPL  72  is patterned with a second pattern. Specifically, the second photoresist layer  77  is patterned with the pattern, and the second pattern is transferred through the second ARC layer  74  and the second OPL  72  by a pattern transfer etch. 
         [0082]    The second pattern includes an opening therein, and the opening in the second pattern straddles over a portion of the etch-resistant material portion  60 . In one embodiment, the etch-resistant material portion  60  can be an H-shaped etch-resistant material portion including a primary etch-resistant line portion having the second width w 2  and a pair of adjoining etch-resistant line portions that are adjoined to two ends of the primary etch-resistant line portion. In one embodiment, the opening in the second pattern can straddle over the primary etch-resistant line portion. Additionally, sidewalls of the stack of the second photoresist layer  77 , the second ARC layer  74 , and the second OPL  72  can overlie each of the pair of adjoining etch-resistant line portions. 
         [0083]    In one embodiment, the opening in the second pattern can have a substantially rectangular shape, wherein a portion of the etch-resistant material portion straddles over an area of a center portion of the rectangular shape. A pair of parallel sides of the rectangle can overlie the pair of adjoining etch-resistant line portions, and another pair of parallel sides of the rectangle can be laterally spaced by a region including the entirety of the primary etch-resistant line portion. 
         [0084]    Referring to  FIGS. 9A and 9B , a composite pattern derived from the second pattern is transferred through the stack of the contiguous spacer layer  50 , the template layer  40 , and optionally through the at least one underlying material layer ( 34 ,  32 ,  30 ) by an anisotropic etch that employs the combination of the second photoresist layer  77  and the etch-resistant material portion  60  as an etch mask. Because the etch-resistant material portion  60  prevents etching of materials located directly underneath during the anisotropic etch, the composite pattern formed by the anisotropic etch below the topmost surface of the contiguous spacer layer  50  is a pattern of the intersection of the second pattern and the complement of the pattern of the etch-resistant material portion  60 . 
         [0085]    The composite pattern includes a pair of via holes  79  laterally spaced by the etch-resistant material portion  60 . In one embodiment, the pair of via holes  79  extends through the entirety of the template layer  40 . The bottom surface of the pair of via holes  79  can protrude under the top surface of the substrate layer  10 , can be coplanar with the top surface of the substrate layer  10 , can be located between the bottommost surface and the topmost surface of the at least one underlying material layer ( 34 ,  32 ,  30 ), or can be coplanar with the bottommost surface of the template layer  40 . 
         [0086]    Referring to  FIGS. 10A and 10B , the stack of the second photoresist layer  77 , the second ARC layer  74 , and the second OPL  72  are removed, for example, by ashing. 
         [0087]    Referring to  FIGS. 11A and 11B , a conductive material is deposited in the pair of via holes  79  and over the topmost surface of the contiguous spacer layer  50 , for example, by physical vapor deposition (PVD), chemical vapor deposition (CVD), electroplating, electroless plating, or a combination thereof. The conductive material can be, for example, Cu, TiN, TaN, WN, Ti, Ta, W, Al, or an alloy or a combination thereof. 
         [0088]    Excess conductive material deposited above the topmost surface of the contiguous spacer layer  50  and above the etch-resistant material portion  60  is removed, for example, by chemical mechanical planarization (CMP) or a recess etch. Remaining portions of the conductive material within the pair of via holes  79  constitutes a pair of via structures  80 . 
         [0089]    The structure in  FIGS. 11A and 11B  includes a stack of the template layer  40  and the contiguous spacer layer  50 ; the etch-resistant material portion  60  overlying a recessed portion of the stack; and the pair of via structures  80 , embedded within the stack and laterally spaced by the etch-resistant material portion  60  and the recessed portion of the stack ( 40 ,  50 ). The entirety of the contiguous spacer layer  50  is contiguous, and the contiguous spacer layer  50  has the same thickness in the recessed portion of the stack ( 40 ,  50 ) as in the non-recessed portion of the stack ( 40 ,  50 ). 
         [0090]    In one embodiment, the top surface of the contiguous spacer layer  50 , the top surface of the etch-resistant material portion  60 , and the top surfaces of the pair of via structures  80  can be substantially coplanar among one another. The etch-resistant material portion  60  can have an H-shaped pattern. The etch-resistant material portion  60  has a rectangular portion, i.e., the primary etch-resistant line portion having the second width w 2 , that laterally contacts the pair of via structures  80 . The lateral extent of the pair of via structures  80  along the lengthwise direction of the primary etch-resistant material portion is bounded by a pair of parallel line portions within the H-shaped pattern, i.e., by the pair of adjoining etch-resistant line portions. The etch-resistant material portion  60  can have a sub-lithographic lateral dimension for deep ultraviolet lithography such as the second width w 2 . Additionally, the width of each of the pair of adjoining etch-resistant line portions can be a sub-lithographic lateral dimension for deep ultraviolet lithography. 
         [0091]    In one embodiment, the etch-resistant material portion  60  can include a dielectric material, and the pair of via structures  80  can be electrically isolated from each other by the materials between the plane of the topmost surface of the pair of via structures  80  and the plane of the bottommost surface of the pair of via structures  80 . 
         [0092]    Various modifications to the structure of  FIGS. 11A and 11B  can be derived by eliminating any or all of the at least one underlying material layer ( 34 ,  32 ,  30 ) and/or by altering the height of the bottom surfaces of the pair of via structures  80 . Further, additional modifications to the structure of  FIGS. 11A and 11B  can be derived by further removing additional material from the topmost surface of the structure of  FIGS. 11A and 11B , for example, by chemical mechanical planarization. For example, a chemical mechanical planarization process can proceed until a portion of the contiguous spacer layer  50  is removed without removing any of the template material layer  40 , or can proceed until some of the template material layer  40  is removed without fully removing the etch-resistant material portion  60 , or can proceed until the etch-resistant material portion  60  is fully removed with or without further removal of portions of the contiguous spacer layer  50  and the template layer  40  between the bottommost surface of the etch-resistant material portion  60  and the topmost surface of the at least one underlying material layer ( 34 ,  32 ,  30 ). 
         [0093]    Referring to  FIGS. 12A and 12B , a variation of the first exemplary structure can be derived from the first exemplary structure of  FIGS. 11A and 11B  by employing a semiconductor-on-insulator (SOI) substrate  8 ′ including a handle substrate  10 ′, a buried insulator layer  12 , and a top semiconductor layer  30  instead of a semiconductor layer  10 . 
         [0094]    Referring to  FIGS. 13A and 13B , a second exemplary structure can be derived from the first exemplary structure of  FIGS. 11A and 11B  by employing a conductive material, such as TiN, TaN, WN, TIC, TaC, WC, Ta, Ti, W, Cu, Al, or an alloy or a combination thereof, for the etch-resistant material portion  60 , and subsequently removing the etch-resistant material portion  60 . The removal of the etch-resistant material portion  60  can be effected by further planarizing the structure of  FIGS. 11A and 11B  so that the planarization stops at a height between the height of the bottommost surface of the etch-resistant material portion  60  and the height of the bottommost surface of the pair of via structures  80 . For example, the optional hard mask layer  34  can be employed as the stopping layer for the planarization process. 
         [0095]    Referring to  FIGS. 14A and 14B , a third exemplary structure according to a third embodiment of the present disclosure can be derived from the first exemplary structure of  FIGS. 1A and 1B  by performing the processing steps of  FIGS. 2A ,  2 B,  3 A, and  3 B with the modification of the first pattern. Specifically, the first pattern is modified to include a substantially rectangular opening having the first width w 1 . Thus, the H-shaped opening of the first embodiment is modified to include a rectangular opening without the adjoining line shapes. 
         [0096]    Referring to  FIGS. 15A and 15B , the processing steps of  FIGS. 4A and 4B  are performed as in the first embodiment. A rectangular line trench is formed in the template layer  40  such that the lengthwise direction of the rectangular line trench is the same as the lengthwise direction of the rectangular opening in the first photoresist layer  47 . 
         [0097]    Referring to  FIGS. 16A and 16B , the processing steps of  FIGS. 5A and 5B  are performed as in the first embodiment. 
         [0098]    Referring to  FIGS. 17A and 17B , the processing steps of  FIGS. 6A and 6B  are performed as in the first embodiment. 
         [0099]    Referring to  FIGS. 18A and 18B , the processing steps of  FIGS. 7A and 7B  are performed as in the first embodiment. 
         [0100]    Referring to  FIGS. 19A and 19B , the processing steps of  FIGS. 8A and 8B  are performed as in the first embodiment. The etch-resistant material portion  60  of the third embodiment consists of a rectangular line portion and does not include any adjoining line portions that are present in the H-shaped etch-resistant material portion  60  of the first embodiment. In one embodiment, the second opening can have a rectangular shape. A pair of sides of the rectangle is laterally spaced by a region including a center portion of the etch-resistant material portion  60 . End portions of the etch-resistant material portion  60  are located outside the area of the rectangle, and are thus covered by the second photoresist  77 . 
         [0101]    Referring to  FIGS. 20A and 20B , the processing steps of  FIGS. 9A and 9B  are performed as in the first embodiment. Because the etch-resistant material portion  60  of the third embodiment is not H-shaped, the lateral extent of the pair of via holes  79  of the third embodiment is not bounded in the lengthwise direction of the etch-resistant material portion  60  by any portion of the etch-resistant material portion  60 . The spacing between the pair of the via holes  79  is the same as the width of the etch-resistant material portion  60 , i.e., the second width w 2 . 
         [0102]    Referring to  FIGS. 21A and 21B , the processing steps of  FIGS. 10A and 10B  are performed as in the first embodiment. 
         [0103]    Referring to  FIGS. 22A and 22B , the processing steps of  FIGS. 11A and 11B  are performed as in the first embodiment. The etch-resistant material portion  60  has a rectangular shape, and the pair of via structures  80  is separated along a widthwise direction of the rectangular shape. The etch-resistant material portion can have a sub-lithographic lateral dimension for deep ultraviolet lithography such as the second width w 2 . 
         [0104]    Referring to  FIGS. 23A and 23B , a variation of the third exemplary structure can be derived from the third exemplary structure employing the same methods as in the variation of the first exemplary structure illustrated in  FIGS. 12A and 12B . 
         [0105]    Referring to  FIGS. 24A and 24B , a fourth exemplary structure according to a second embodiment of the present disclosure can be derived from the third exemplary structure employing the same methods as the second embodiment. The fourth exemplary structure can have the same features as the second exemplary structure of  FIGS. 13A and 13B . 
         [0106]    While the disclosure has been described in terms of specific embodiments, it is evident in view of the foregoing description that numerous alternatives, modifications and variations will be apparent to those skilled in the art. Each of the various embodiments of the present disclosure can be implemented alone, or in combination with any other embodiments of the present disclosure unless expressly disclosed otherwise or otherwise impossible as would be known to one of ordinary skill in the art. Accordingly, the disclosure is intended to encompass all such alternatives, modifications and variations which fall within the scope and spirit of the disclosure and the following claims.