Abstract:
Techniques for forming a contact to a buried diffusion layer in a semiconductor memory device are disclosed. The techniques may be realized as a semiconductor memory device. The semiconductor memory device may comprise a substrate comprising an upper layer, an array of dummy pillars formed on the upper layer of the substrate and arranged in rows and columns, and an array of active pillars formed on the upper layer of the substrate and arranged in rows and columns. Each of the dummy pillars may extend upward from the upper layer and have a bottom contact that is electrically connected with the upper layer of the substrate. Each of the active pillars may extend upward from the upper layer and have an active first region, an active second region, and an active third region. Each of the active pillars may also be electrically connected with the upper layer of the substrate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This patent application is a continuation of U.S. patent application Ser. No. 12/717,776, filed Mar. 4, 2010, which claims priority to U.S. Provisional Patent Application No. 61/157,504, filed Mar. 4, 2009, each of which is hereby incorporated by reference herein in its entirety. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    The present disclosure relates generally to semiconductor memory devices and, more particularly, to techniques for forming a contact to a buried diffusion layer in a semiconductor memory device. 
       BACKGROUND OF THE DISCLOSURE 
       [0003]    The semiconductor industry has experienced technological advances that have permitted increases in density and/or complexity of semiconductor memory devices. Also, the technological advances have allowed decreases in power consumption and package sizes of various types of semiconductor memory devices. There is a continuing trend to employ and/or fabricate advanced semiconductor memory devices using techniques, materials, and devices that improve performance, reduce leakage current, and enhance overall scaling. Semiconductor-on-insulator (SOI) and bulk substrates are examples of materials that may be used to fabricate such semiconductor memory devices. Such semiconductor memory devices may include, for example, partially depleted (PD) devices, fully depleted (FD) devices, multiple gate devices (for example, double or triple gate), and Fin-FET devices. 
         [0004]    A semiconductor memory device may include a memory cell having a memory transistor with an electrically floating body region wherein electrical charges may be stored. The electrical charges stored in the electrically floating body region may represent a logic high (e.g., binary “1” data state) or a logic low (e.g., binary “0” data state). Also, a semiconductor memory device may be fabricated on semiconductor-on-insulator (SOI) substrates or bulk substrates (e.g., enabling body isolation). For example, a semiconductor memory device may be fabricated as a three-dimensional (3-D) device (e.g., multiple gate devices, Fin-FETs, recessed gates and pillars). 
         [0005]    In one conventional technique, an array of minimum feature size memory cells may print uniformly in accordance with certain lithographic specifications while the periodicity of a lithographic pattern remains consistent. When the periodicity of the lithographic pattern is interrupted (e.g., at an edge of the array), however, the minimum feature size memory cells may not print uniformly. 
         [0006]    In another conventional technique, a storage array of minimum feature size memory cells may use dummy pillar structures to ensure proper printing of active pillar structures near an array edge when the periodicity of a lithographic pattern is interrupted to form a bottom contact to buried diffusion. These dummy pillar structures may be similar to active pillar structures in physical appearance, but may not contribute to any storage function of the array. Likewise, if, for example, the bottom contact to buried diffusion is nested within an array of pillar structures, dummy pillar structures may be formed on both sides of the nested bottom contact to buried diffusion to provide for proper printing of adjacent active pillar structures. 
         [0007]    Often, the conventional use of dummy pillar structures may significantly increase area overhead of the array since, for example, two (2) rows of dummy pillar structures may be formed between a row of bottom contacts to buried diffusion and an array of active pillar structures. In certain instances, the area overhead attributed to the use of dummy pillar structures may double when the bottom contacts to buried diffusion are nested within an array of pillar structures. In such instances, for example, two (2) rows of dummy pillar structures may be formed on both sides of the nested bottom contacts. Also, the conventional use of dummy pillar structures may significantly increase the processing cost and complexity of forming array edges that include separate pillar bottom contacts to buried diffusion. 
         [0008]    In view of the foregoing, it may be understood that there may be significant problems and shortcomings associated with the conventional use of conventional dummy pillar structures. 
       SUMMARY OF THE DISCLOSURE 
       [0009]    Techniques for forming a contact to a buried diffusion layer in a semiconductor memory device are disclosed. In one particular exemplary embodiment, the techniques may be realized as a semiconductor memory device. The semiconductor memory device may comprise a substrate comprising an upper layer. The semiconductor memory device may also comprise an array of dummy pillars formed on the upper layer of the substrate and arranged in rows and columns. Each of the dummy pillars may extend upward from the upper layer and have a bottom contact that is electrically connected with the upper layer of the substrate. The semiconductor memory device may also comprise an array of active pillars formed on the upper layer of the substrate and arranged in rows and columns. Each of the active pillars may extend upward from the upper layer and have an active first region, an active second region, and an active third region. Each of the active pillars may also be electrically connected with the upper layer of the substrate. 
         [0010]    In accordance with other aspects of this particular exemplary embodiment, the rows of the dummy pillars may extend along a word line direction and the columns of the dummy pillars may extend along a bit line direction. 
         [0011]    In accordance with further aspects of this particular exemplary embodiment, each of the dummy pillars may have a dummy first region, a dummy second region, and a dummy third region. 
         [0012]    In accordance with additional aspects of this particular exemplary embodiment, the dummy first region may comprise a dummy upper region doped with a type of impurity, the dummy second region may comprise a dummy middle region doped with the type of impurity, and the dummy third region may comprise a dummy lower region doped with the type of impurity. 
         [0013]    In accordance with other aspects of this particular exemplary embodiment, each dummy middle region may be capacitively coupled to at least one dummy word line. 
         [0014]    In accordance with further aspects of this particular exemplary embodiment, the rows of the active pillars may extend along a word line direction and the columns of the active pillars may extend along a bit line direction. 
         [0015]    In accordance with additional aspects of this particular exemplary embodiment, the active first region may comprise an active upper region doped with a first type of impurity, the active second region may comprise an active middle region doped with a second type of impurity, and the active third region may comprise an active lower region doped with the first type of impurity. 
         [0016]    In accordance with other aspects of this particular exemplary embodiment, the active middle region of each active pillar may be electrically floating and disposed between the active upper region and the active lower region. 
         [0017]    In accordance with further aspects of this particular exemplary embodiment, a gate region may be formed on at least one side of the active middle region of each active pillar. 
         [0018]    In accordance with additional aspects of this particular exemplary embodiment, the active middle region of each active pillar may be capacitively coupled to an active word line. 
         [0019]    In accordance with other aspects of this particular exemplary embodiment, the active upper region of each active pillar may be coupled to at least one active bit line. 
         [0020]    In accordance with further aspects of this particular exemplary embodiment, the array of dummy pillars may extend along an outer edge of an array of memory cells formed on the substrate. 
         [0021]    In accordance with additional aspects of this particular exemplary embodiment, the array of dummy pillars may be adjacent to the array of active pillars. 
         [0022]    In another particular exemplary embodiment, the techniques may be realized as another semiconductor memory device. The semiconductor memory device may comprise a substrate comprising an upper layer. The semiconductor memory device may also comprise a column of dummy pillars formed on the upper layer of the substrate. Each of the dummy pillars may extend upward from the upper layer and have a bottom contact that is electrically connected with the upper layer of the substrate. The semiconductor memory device may also comprise a first array of active pillars formed on the upper layer of the substrate and arranged in rows and columns. The semiconductor memory device may also comprise a second array of active pillars formed on the upper layer of the substrate and arranged in rows and columns. Each of the active pillars may extend upward from the upper layer and have an active first region, an active second region, and an active third region. Each of the active pillars may also be electrically connected with the upper layer of the substrate. 
         [0023]    In accordance with other aspects of this particular exemplary embodiment, the column of dummy pillars may extend along a bit line direction. 
         [0024]    In accordance with further aspects of this particular exemplary embodiment, each of the dummy pillars may have a dummy first region, a dummy second region, and a dummy third region. 
         [0025]    In accordance with additional aspects of this particular exemplary embodiment, the dummy first region may comprise a dummy upper region doped with a type of impurity, the dummy second region may comprise a dummy middle region doped with the type of impurity, and the dummy third region may comprise a dummy lower region doped with the type of impurity. 
         [0026]    In accordance with other aspects of this particular exemplary embodiment, the rows of the active pillars may extend along a word line direction and the columns of the active pillars may extend along a bit line direction. 
         [0027]    In accordance with further aspects of this particular exemplary embodiment, the active first region may comprise an active upper region doped with a first type of impurity, the active second region may comprise an active middle region doped with a second type of impurity, and the active third region may comprise an active lower region doped with the first type of impurity. 
         [0028]    In accordance with additional aspects of this particular exemplary embodiment, the active middle region of each active pillar may be electrically floating and disposed between the active upper region and the active lower region. 
         [0029]    In accordance with other aspects of this particular exemplary embodiment, a gate region may be formed on at least one side of the active middle region of each active pillar. 
         [0030]    In accordance with further aspects of this particular exemplary embodiment, the active middle region of each active pillar may be capacitively coupled to an active word line. 
         [0031]    In accordance with additional aspects of this particular exemplary embodiment, the active upper region of each active pillar may be coupled to at least one active bit line. 
         [0032]    In accordance with other aspects of this particular exemplary embodiment, the column of dummy pillars may be nested between the first array of active pillars and the second array of active pillars. 
         [0033]    The present disclosure will now be described in more detail with reference to exemplary embodiments thereof as shown in the accompanying drawings. While the present disclosure is described below with reference to exemplary embodiments, it should be understood that the present disclosure is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional implementations, modifications, and embodiments, as well as other fields of use, which are within the scope of the present disclosure as described herein, and with respect to which the present disclosure may be of significant utility. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]    In order to facilitate a fuller understanding of the present disclosure, reference is now made to the accompanying drawings, in which like elements are referenced with like numerals. These drawings should not be construed as limiting the present disclosure, but are intended to be exemplary only. 
           [0035]      FIG. 1  shows a cross-sectional view of a pillar array of a semiconductor memory device with bottom contacts to diffusion formed on dummy pillars in accordance with an embodiment of the present disclosure. 
           [0036]      FIG. 2  shows a cross-sectional view of a pillar array of a semiconductor memory device with bottom contacts to diffusion formed on dummy pillars and a pillar substrate contact in accordance with an embodiment of the present disclosure. 
           [0037]      FIG. 3  shows a two-dimensional top view of a pillar array of a semiconductor memory device with bottom contacts to diffusion formed on dummy pillars in accordance with an embodiment of the present disclosure. 
           [0038]      FIG. 4  shows a cross-sectional view of a pillar array of a semiconductor memory device with nested bottom contacts to diffusion formed on dummy pillars in accordance with an embodiment of the present disclosure. 
           [0039]      FIG. 5  shows a two-dimensional top view of a pillar array of a semiconductor memory device with nested bottom contacts to diffusion formed on dummy pillars in accordance with an embodiment of the present disclosure. 
           [0040]      FIG. 6  shows processing steps for forming nested bottom contacts to diffusion on dummy pillars in accordance with an embodiment of the present disclosure. 
           [0041]      FIG. 7A  shows processing steps for forming nested bottom contacts to diffusion on dummy pillars in accordance with an alternative embodiment of the present disclosure. 
           [0042]      FIG. 7B  shows additional processing steps for forming nested bottom contacts to diffusion on dummy pillars in accordance with an alternative embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0043]    A conventional array of minimum feature size (F) pillar structures may include an active array area that is adjacent to a dummy array area to ensure proper printing of a lithographic pattern when bottom contacts to diffusion are formed. The active array area may include an array of active pillar structures. Each active pillar structure may form a memory cell in a memory device that is configured to store electrical charge. An active pillar structure may store the electrical charge within an electrically floating body region. For example, the active pillar structure may store an electric charge that represents a logic high (e.g., binary “1” data state) or an electric charge that represents a logic low (e.g., binary “0” data state). The dummy array area may include at least two (2) rows of dummy pillar structures that separate the array of active pillar structures from the array edge. On the array-edge-side of the dummy array area, separate pillar bottom contacts to diffusion may be formed. 
         [0044]    By way of a non-limiting example, a minimum feature size (F) of 32 nanometers (nm) may be used for 32 nm lithography. Assuming each pillar in a conventional pillar array has a plug contact height of 1 F, an upper region (e.g., drain region, source region) height of 1 F, a body region height of 2 F, and a lower region (e.g., source region, drain region) height of 1 F, forming a separate 5 F tall contact to the bottom diffusion may significantly increase processing costs and the complexity of the conventional pillar array at the array edge. Furthermore, the area overhead of the conventional pillar array may be significantly increased when the separate contacts to the bottom diffusion are nested within the pillar array. In such instances, the area overhead attributed to the formation of the separate contacts to the bottom diffusion may double since at least two (2) rows of dummy pillars may be formed on both sides of the nested contacts to the bottom diffusion. 
         [0045]    Referring to  FIG. 1 , there is shown a cross-sectional view of a pillar array  100  of a semiconductor memory device with bottom contacts to diffusion formed on dummy pillars in accordance with an embodiment of the present disclosure. As illustrated in  FIG. 1 , the pillar array  100  may include any, or a combination, of a substrate  114 , a diffusion layer  112 , an active array area  104 , one or more active pillars  108 A,  108 B, a dummy array area  102 , and one or more dummy pillars  106 A,  106 B. 
         [0046]    The substrate  114  and the diffusion layer  112  of the substrate  114  may each be formed from a semiconductor material that is doped with a P type impurity concentration, an N type impurity concentration, or any other type of impurity concentration. In one embodiment, the semiconductor material of substrate  114  and the semiconductor material of diffusion layer  112  may be doped with impurity concentrations that are of opposite types. For example, as shown in  FIG. 1 , the semiconductor material of substrate  114  may be doped with a P type impurity concentration and the semiconductor material of diffusion layer  112  may be doped with an N+ type impurity concentration. 
         [0047]    The diffusion layer  112  may include an active array area  104  on which an array of one or more active pillars  108 A,  108 B are formed. Active pillars  108 A,  108 B may be vertical transistors that include upper regions  128 ,  124 , middle regions  140 ,  138 , and lower regions  130 ,  126 , respectively. Each of the upper regions  128 ,  124 , middle regions  140 ,  138 , and lower regions  130 ,  126  may be formed of a semiconductor material that is doped with a P type impurity concentration, an N type impurity concentration, or any other type of impurity concentration. In one embodiment, the semiconductor material of upper regions  128 ,  124  and the semiconductor material of lower regions  130 ,  126  may be doped with impurity concentrations that are the same type. In another embodiment, the semiconductor material of middle regions  140 ,  138  may be doped with an impurity concentration that is of the opposite type of the impurity concentration of the semiconductor material of the upper regions  128 ,  124  and the lower regions  130 ,  126 . For example, as shown in  FIG. 1 , the semiconductor material of upper regions  128 ,  124  and the lower regions  130 ,  126  may be doped with an N+ type impurity concentration, and the semiconductor material of middle regions  140 ,  138  may be doped with a P+ type impurity concentration. 
         [0048]    The upper regions  128 ,  124  may be source regions, drain regions, or any other type of region. The lower regions  130 ,  126  may be drain regions, source regions, or any other type of region. The middle regions  140 ,  138  may be body regions that are electrically floating. 
         [0049]    The middle regions  140 ,  138  of active pillars  108 A,  108 B may be coupled (e.g., capacitively coupled) to a gate structure formed from a poly-silicon material, metal material, metal silicide material, and/or any other material that may be used to form a gate of an active pillar. A gate structure may be a single gate structure, a dual gate structure, a triple gate structure, a quadruple gate structure, etc. For example, the middle regions  140 ,  138  of active pillars  108 A,  108 B may be coupled to dual gate structures. Each gate of each active pillar may be coupled to gates of one or more additional active pillars positioned in a row to form a word line. In one example, one gate of active pillar  108 A may be coupled to gates of one or more additional active pillars (not shown) positioned in a row to form word line  120 A, and another gate of active pillar  108 A may be coupled to other gates of the one or more additional active pillars to form word line  120 B. In another example, one gate of active pillar  108 B may be coupled to gates of one or more additional active pillars (not shown) positioned in a row to form word line  122 A, and another gate of active pillar  108 B may be coupled to other gates of the one or more additional active pillars to form word line  122 B. Accordingly, the rows of the active pillars (including active pillars  108 A,  108 B) may extend in a word line direction that is parallel to diffusion layer  112 . 
         [0050]    Each upper region of each active pillar may be coupled to a plug contact (e.g., a poly-silicon plug contact) that is coupled to a bit line. For example, the upper region  128  of active pillar  108 A may be coupled to plug contact  132  that is coupled to a bit line. Furthermore, the upper region  124  of active pillar  108 B may be coupled to plug contact  116  that is coupled to the bit line. The columns of the active pillars may extend in a bit line direction that is parallel to diffusion layer  112 . 
         [0051]    Active pillars  108 A,  108 B may operate as memory cells that store electrical charge in middle regions  140 ,  138  (e.g., body regions) that are electrically floating. For example, the middle regions  140 ,  138  of active pillars  108 A,  108 B may store electrical charge that represents a logic high (e.g., binary “1” data state) or a logic low (e.g., binary “0” data state). 
         [0052]    The diffusion layer  112  may include a dummy array area  102  on which an array of one or more dummy pillars  106 A,  106 B are formed. The dummy array area  102  may extend along an array edge of the pillar array  100 . Dummy pillars  106 A,  106 B may be similar to active pillars  108 A,  108 B in physical appearance, but may not contribute to any storage function of the pillar array  100  except to provide contacts (e.g., electrical connections) to the diffusion layer  112 . 
         [0053]    Dummy pillars  106 A,  106 B may include upper regions  142 ,  144 , middle regions  150 ,  152 , and lower regions  146 ,  148 , respectively. Each of the upper regions  142 ,  144 , middle regions  150 ,  152 , and lower regions  146 ,  148  may be formed of a semiconductor material that is doped with a P type impurity concentration, an N type impurity concentration, or any other type of impurity concentration. In one embodiment, the semiconductor material of upper regions  142 ,  144 , middle regions  150 ,  152 , and lower regions  146 ,  148  may be doped with impurity concentrations that are the same type. For example, as shown in  FIG. 1 , the semiconductor material of the upper regions  142 ,  144 , middle regions  150 ,  152 , and lower regions  146 ,  148  may be doped with an N+ type impurity concentration. 
         [0054]    The middle regions  150 ,  152  of dummy pillars  106 A,  106 B may be coupled (e.g., capacitively coupled) to a dummy gate structure formed from a poly-silicon material, metal material, metal silicide material, and/or any other material that may be used to form a dummy gate of a dummy pillar. A dummy gate structure may be a single dummy gate structure, a dual dummy gate structure, a triple dummy gate structure, a quadruple dummy gate structure, etc. For example, the middle regions  150 ,  152  of dummy pillars  106 A,  106 B may be coupled to dual dummy gate structures. Each dummy gate of each dummy pillar may be coupled to dummy gates of one or more additional dummy pillars positioned in a row to form a dummy word line. In one example, one dummy gate of dummy pillar  106 A may be coupled to dummy gates of one or more additional dummy pillars (not shown) positioned in a row to form dummy word line  110 A, and another dummy gate of dummy pillar  106 A may be coupled to other dummy gates of the one or more additional dummy pillars to form dummy word line  110 B. In another example, one dummy gate of dummy pillar  106 B may be coupled to dummy gates of one or more additional dummy pillars (not shown) positioned in a row to form dummy word line  118 A, and another dummy gate of dummy pillar  106 B may be coupled to other dummy gates of the one or more additional dummy pillars to form dummy word line  118 B. Accordingly, the rows of the dummy pillars (including dummy pillars  106 A,  106 B) may extend in a word line direction that is parallel to diffusion layer  112 . 
         [0055]    Each upper region of each dummy pillar may be coupled to a plug contact (e.g., a poly-silicon plug contact) that is coupled to metal coupling that, in turn, is coupled to a metal strapping. Thus, each dummy pillar provides an electrical connection between a metal strapping and the diffusion layer  112 . For example, the upper region  142  of dummy pillar  106 A may be coupled to plug contact  136  that is coupled to a metal coupling that, in turn, is coupled to a metal strapping. Thus, dummy pillar  106 A provides an electrical connection between the metal strapping and the diffusion layer  112 . Furthermore, the upper region  144  of dummy pillar  106 B may be coupled to plug contact  134  that is coupled a metal coupling that, in turn, is coupled to a metal strapping. Thus, dummy pillar  106 B provides an electrical connection between the metal strapping and the diffusion layer  112 . The columns of the dummy pillars may extend in a bit line direction that is parallel to diffusion layer  112 . 
         [0056]    Accordingly, dummy pillars  106 A,  106 B may be used as bottom contacts to the diffusion layer  112  to reduce the area overhead of the pillar array  100  attributed to the formation of separate contacts to the diffusion layer  112 . Details of exemplary processing steps for forming contacts to a bottom diffusion layer on dummy pillars are provided below with reference to  FIGS. 6-7B . 
         [0057]    Referring to  FIG. 2 , there is shown a cross-sectional view of a pillar array  200  of a semiconductor memory device with bottom contacts to diffusion formed on dummy pillars and a pillar substrate contact in accordance with an embodiment of the present disclosure. As illustrated in  FIG. 2 , the pillar array  200  may include any, or a combination, of a substrate  114 , a diffusion layer  112 , an active array area  104  with one or more active pillars, a dummy array area  102  with one or more dummy pillars, and a pillar substrate contact  202 . Pillar array  200  may be similar to pillar array  100  described above with reference to  FIG. 1 . 
         [0058]    Pillar substrate contact  202  may be formed on substrate  114  and of a semiconductor material and/or a metal material. For example, the pillar body  204  of pillar substrate contact  202  may be formed from a semiconductor material that is doped with a P type impurity concentration, N type impurity concentration, or any other type of impurity concentration. In one embodiment, the semiconductor material of the pillar body  204  and the semiconductor material of the active pillars, dummy pillars, and diffusion layer  112 , may be doped with impurity concentrations that are of the opposite type. In another embodiment, the semiconductor material of the pillar body  204  and the semiconductor material of substrate  114  may be doped with impurity concentrations that are of the same type. For example, the semiconductor material of pillar body  204  may be doped with a P+ type impurity concentration. The contact material of pillar substrate contact  202  may be formed from a metal material (e.g., tungsten), metal-silicide material, metal-like material, or any other material that may be used to provide an electrical connection between the pillar substrate contact  202  and the substrate  114 . 
         [0059]    The pillar substrate contact  202  may be positioned adjacent to one or more dummy pillars of the dummy array area  102 . As previously described with reference to  FIG. 1 , the one or more dummy pillars may provide bottom contacts to diffusion layer  112  at the array edge of pillar array  200 . Further, one or more active pillars of the active array area  104  may be positioned adjacent to the dummy array area  102 . The one or more active pillars may operate as memory cells of the pillar array  200 . 
         [0060]    Referring to  FIG. 3 , there is shown a two-dimensional top view of a pillar array  312  of a semiconductor memory device with bottom contacts to diffusion formed on dummy pillars in accordance with an embodiment of the present disclosure. As illustrated in  FIG. 3 , the pillar array  312  may include any, or a combination, of an active array area  104 , one or more active pillars  302 A,  302 B,  302 C,  302 D,  302 E,  302 F, a dummy array area  102 , and one or more dummy pillars  300 A,  300 B,  300 C,  300 D,  300 E,  300 F. Pillar array  312  may be two-dimensional top view of pillar array  100  described above with reference to  FIG. 1 . 
         [0061]    As previously described with reference to  FIG. 1 , active array area  104  may include active pillars  302 A,  302 B,  302 C,  302 D,  302 E,  302 F. One gate of active pillars  302 A,  302 B,  302 C may be coupled together in row  316 A to form word line  308 A. Another gate of active pillars  302 A,  302 B,  302 C may be coupled together in row  316 A to form word line  308 B. Likewise, one gate of active pillars  302 D,  302 E,  302 F may be coupled together in row  316 B to form word line  310 A. Another gate of active pillars  302 D,  302 E,  302 F may be coupled together in row  316 B to form word line  310 B. Accordingly, the rows  316 A,  316 B of active pillars may extend in a word line direction. 
         [0062]    In one embodiment, the upper regions of active pillars  302 A,  302 D may be coupled to Bit Line 0 to form a column of active pillars. In another embodiment, the upper regions of active pillars  302 B,  302 E may be coupled to Bit Line 1 to form another column of active pillars. In yet another embodiment, the upper regions of active pillars  302 C,  302 F may be coupled to Bit Line 2 to form another column of active pillars. Accordingly, the columns of active pillars may extend in a bit line direction. 
         [0063]    As previously described with reference to  FIG. 1 , dummy array area  102  may include dummy pillars  300 A,  300 B,  300 C,  300 D,  300 E,  300 F. One dummy gate of dummy pillars  300 A,  300 B,  300 C may be coupled together in row  314 A to form dummy word line  304 A. Another dummy gate of dummy pillars  300 A,  300 B,  300 C may be coupled together in row  314 A to form dummy word line  304 B. Likewise, one dummy gate of dummy pillars  300 D,  300 E,  300 F may be coupled together in row  314 B to form dummy word line  306 A. Another dummy gate of dummy pillars  300 D,  300 E,  300 F may be coupled together in row  314 B to form dummy word line  306 B. Accordingly, the rows  314 A,  314 B of dummy pillars may extend in a dummy word line direction that is parallel to a word line direction. 
         [0064]    In one embodiment, the upper regions of dummy pillars  300 A,  300 D may be coupled to Bottom Contact 0 to form a column of dummy pillars. In another embodiment, the upper regions of dummy pillars  300 B,  300 E may be coupled to Bottom Contact 1 to form another column of dummy pillars. In yet another embodiment, the upper regions of dummy pillars  300 C,  300 F may be coupled to Bottom Contact 2 to form another column of dummy pillars. Accordingly, the columns of dummy pillars may extend in a bit line direction. 
         [0065]    As illustrated in  FIGS. 1 and 3 , area overhead at the array edge of pillar array  100  and pillar array  312  may be significantly reduced by eliminating the formation of separate standard (e.g., tungsten) bottom contacts to a diffusion layer. Instead, dummy pillars (e.g., dummy pillars  300 A,  300 B,  300 C,  300 D,  300 E,  300 F) may be used as bottom contacts to a diffusion layer. 
         [0066]    Referring to  FIG. 4 , there is shown a cross-sectional view of a pillar array of a semiconductor memory device with nested bottom contacts to diffusion formed on dummy pillars in accordance with an embodiment of the present disclosure. As illustrated in  FIG. 4 , a pillar array  400  may include any, or a combination, of a substrate  408 , a diffusion layer  406 , an active array area  412 , an active array area  414 , one or more active pillars  402 A,  402 B,  402 C,  402 D, a dummy array area  410 , and one or more dummy pillars  404 . It should be noted that substrate  408  may be similar to substrate  114  of  FIG. 1 , diffusion layer  406  may be similar to diffusion layer  112  of  FIG. 1 , active pillars  402 A,  402 B,  402 C,  402 D may be similar to active pillars  108 A,  108 B of  FIG. 1 , and dummy pillar  404  may be similar to dummy pillars  106 A,  106 B of  FIG. 1 . 
         [0067]    Active array area  412  may include active pillars  402 A,  402 B. Each upper region of each active pillar may be coupled to a plug contact (e.g., a poly-silicon plug contact) that is coupled to a bit line. The upper region of active pillar  402 A may be coupled to a bit line that is coupled to one or more additional active pillars (not shown) positioned in a column. Likewise, the upper region of active pillar  402 B may be coupled to a bit line that is coupled to one or more additional active pillars (not shown) positioned in another column. Accordingly, the columns of pillar array  400  containing active pillars  402 A,  402 B may extend in a bit line direction that is perpendicular to diffusion layer  406 . 
         [0068]    Active array area  414  may include active pillars  402 C,  402 D. Each upper region of each active pillar may be coupled to a plug contact (e.g., a poly-silicon plug contact) that is coupled to a bit line. The upper region of active pillar  402 C may be coupled to a bit line that is coupled to one or more additional active pillars (not shown) positioned in a column. Likewise, the upper region of active pillar  402 D may be coupled to a bit line that is coupled to one or more additional active pillars (not shown) positioned in another column. Accordingly, the columns of pillar array  400  containing active pillars  402 C,  402 D may extend in a bit line direction that is perpendicular to diffusion layer  406 . 
         [0069]    Dummy array area  410  may include dummy pillar  404  and one or more additional dummy pillars (not shown) positioned in a column. Each upper region of each dummy pillar may be coupled to a plug contact (e.g., a poly-silicon plug contact) that is coupled to metal strapping. Thus, each dummy pillar provides an electrical connection between a metal strapping and a diffusion layer. The upper region of dummy pillar  404  may be coupled to a plug contact that is coupled to a metal strapping. Thus, the dummy pillar  404  provides an electrical connection between the metal strapping and the diffusion layer  406 . The column of the dummy pillars may extend in a bit line direction that is perpendicular to diffusion layer  406 . 
         [0070]    One gate (or dummy gate) of active pillars  402 A,  402 B,  402 C,  402 D, and dummy pillar  404  may be coupled together in a row to form a word line. Accordingly, the rows of the pillar array  400  may extend in a word line direction that is parallel to diffusion layer  406 . 
         [0071]    The dummy array area  410  may be nested between active array area  412  and active array area  414 . Since the periodicity of a lithographic pattern is not broken to form separate nested bottom contacts to a buried diffusion layer, multiple columns of dummy pillars may be eliminated. Accordingly, the area overhead of pillar array  400  may be significantly reduced by forming bottom contacts to the diffusion layer on and/or within a nested column of dummy pillars that includes dummy pillar  404 . 
         [0072]    Referring to  FIG. 5 , there is shown a two-dimensional top view of a pillar array of a semiconductor memory device with nested bottom contacts to diffusion formed on dummy pillars in accordance with an embodiment of the present disclosure. As illustrated in  FIG. 5 , a pillar array  500  may include any, or a combination, of an active array area  414 , an active array area  412 , one or more active pillars  504 A,  504 B,  504 C,  504 D,  504 E,  504 F,  504 G,  504 H,  504 I,  504 J, a dummy array area  410 , and one or more dummy pillars  502 A,  502 B,  502 C,  502 D,  502 E. Pillar array  500  may be two-dimensional top view of a portion of pillar array  400  described above with reference to  FIG. 4 . 
         [0073]    As previously described with reference to  FIG. 4 , active array area  414  may include active pillars  504 A,  504 B,  504 C,  504 D,  504 E. Active array area  412  may include active pillars  504 F,  504 G,  504 H,  504 I,  504 J. Dummy array area  410  may include dummy pillars  502 A,  502 B,  502 C,  502 D,  502 E. One gate (or dummy gate) of active pillar  504 A, dummy pillar  502 A, and active pillar  504 F may be coupled together in row  516  to form word line  306 A. Another gate (or another dummy gate) of active pillar  504 A, dummy pillar  502 A, and active pillar  504 F may be coupled together in row  516  to form word line  306 B. One gate (or dummy gate) of active pillar  504 B, dummy pillar  502 B, and active pillar  504 G may be coupled together in row  518  to form word line  308 A. Another gate (or another dummy gate) of active pillar  504 B, dummy pillar  502 B, and active pillar  504 G may be coupled together in row  518  to form word line  308 B. One gate (or dummy gate) of active pillar  504 C, dummy pillar  502 C, and active pillar  504 H may be coupled together in row  520  to form word line  310 A. Another gate (or another dummy gate) of active pillar  504 C, dummy pillar  502 C, and active pillar  504 H may be coupled together in row  520  to form word line  310 B. One gate (or dummy gate) of active pillar  504 D, dummy pillar  502 D, and active pillar  504 I may be coupled together in row  522  to form word line  312 A. Another gate (or another dummy gate) of active pillar  504 D, dummy pillar  502 D, and active pillar  504 I may be coupled together in row  522  to form word line  312 B. Finally, one gate (or dummy gate) of active pillar  504 E, dummy pillar  502 E, and active pillar  504 J may be coupled together in row  524  to form word line  314 A. Another gate (or another dummy gate) of active pillar  504 E, dummy pillar  502 E, and active pillar  504 J may be coupled together in row  524  to form word line  314 B. Accordingly, the rows  516 ,  518 ,  520 ,  522 ,  524  of pillar array  500  may extend in a word line direction. 
         [0074]    In one embodiment, the upper regions of active pillars  504 A,  504 B,  504 C,  504 D,  504 E may be coupled to Bit Line M to form a column of active pillars. In another embodiment, the upper regions of active pillars  504 F,  504 G,  504 H,  504 I,  504 J may be coupled to Bit Line N to form another column of active pillars. In yet another embodiment, the dummy pillars  502 A,  502 B,  502 C,  502 D,  502 E may be positioned in a nested column (between the columns of active pillars). Accordingly, the columns of pillar array  500  may extend in a bit line direction. 
         [0075]    The upper region of each dummy pillar may be coupled to a metal coupling. For example, the upper region of dummy pillar  502 A may be coupled to Metal Coupling A that extends in a word line direction. In another example, the upper region of dummy pillar  502 B may be coupled to Metal Coupling B that extends in a word line direction. In another example, the upper region of dummy pillar  502 C may be coupled to Metal Coupling C that extends in a word line direction. In another example, the upper region of dummy pillar  502 D may be coupled to Metal Coupling D that extends in a word line direction. In yet another example, the upper region of dummy pillar  502 E may be coupled to Metal Coupling E that extends in a word line direction. Accordingly, Metal Couplings A, B, C, D, E may extend in a direction that is parallel to a word line direction and perpendicular to a bit line direction. It should be noted that Metal Couplings A, B, C, D, E may not be coupled to any active pillars. 
         [0076]    As illustrated in  FIGS. 4 and 5 , the periodicity of a lithographic pattern may not be broken to form separate nested bottom contacts to a buried diffusion layer. Accordingly, multiple columns of dummy pillars may be eliminated and the area overhead of pillar array  400  and pillar array  500  may be significantly reduced by forming bottom contacts to the diffusion layer on and/or within a nested column of dummy pillars  502 A,  502 B,  502 C,  502 D,  502 E. 
         [0077]    Referring to  FIG. 6 , there is shown processing steps for forming nested bottom contacts to diffusion on dummy pillars in accordance with an embodiment of the present disclosure. As illustrated in  FIG. 6 , the process may include any, or a combination, of steps  602 ,  604 ,  606 ,  608 ,  610 . Step  602  may include implanting (e.g., ion implanting) a diffusion layer (e.g., diffusion layer  112 , diffusion layer  406 ) on a substrate. Step  604  may include covering the active array areas with a hard mask to ensure that the active array areas are not exposed. Step  606  may include exposing the dummy array area to open the dummy array area for a contact body implant (e.g., a bottom contact) and a body ion implant. Step  608  may include removing the hard masks and implanting (e.g., ion implanting) a top diffusion. Step  610  may include masking and etching the active pillars and a nested bottom contact dummy pillar. 
         [0078]    Referring to  FIG. 7A , there is shown processing steps for forming nested bottom contacts to diffusion on dummy pillars in accordance with an alternative embodiment of the present disclosure. As illustrated in  FIG. 7A , the process may include any, or a combination, of steps  702 ,  704 . Step  702  may include having pillars with contacts (e.g., poly-silicon). Step  704  may include covering the active array areas with a hard mask to ensure that the active array areas are not etched. 
         [0079]    Referring to  FIG. 7B , there is shown additional processing steps for forming nested bottom contacts to diffusion on dummy pillars in accordance with an alternative embodiment of the present disclosure. As illustrated in  FIG. 7B , the process may include any, or a combination, of steps  706 ,  708 . Step  706  may include etching the poly-silicon from an active pillar. Step  708  may include removing the hard mask and filling in the contacts with a poly-silicon material, metal material (e.g., tungsten), metal silicide material, or any other material that may be used as a contact. After step  708 , the nested bottom contact dummy pillar may provide an electrical connection to the diffusion layer. 
         [0080]    The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Further, although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in view of the full breadth and spirit of the present disclosure as described herein.