Abstract:
A semiconductor integrated circuit with tilted via connection and related method are provided, the circuit including a via layer having at least one tilted via, and a wireway layer having at least one elongated wireway disposed above the via layer, wherein the wireway connects to and partially overlaps the tilted via; and the method including forming a via layer, patterning a via trench in the via layer, forming a wireway layer, patterning an elongated wireway in the wireway layer, etching the patterned wireway and the patterned via, and filling the etched wireway and the etched via with a conductive material, wherein the filled wireway partially overlaps the filled via.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present disclosure generally relates to via connections in semiconductor integrated circuits. More particularly, the present disclosure relates to artificially tilted via connections. 
         [0002]    In conventional semiconductor integrated circuits, the spacing between two metal lines is typically small, and determined mainly in correspondence with the underlying via connections and design rule. Due to variations in the manufacturing process, such small spacings generally reduce yield or process margins by causing short circuits and/or reliability failures in a portion of the products. 
         [0003]    In addition, the spacing between metal lines is further decreased as design rules are decreased. Thus, the lithography and Reactive Ion Etching (RIE) process margins are degraded. This further increases the possibility of shorts between neighboring lines, which generally leads to reliability failures, such as Time Dependent Dielectric Breakdown (TDDB). 
       SUMMARY OF THE INVENTION 
       [0004]    These and other issues are addressed by integrated circuits and methods for forming artificially tilted via connections. Exemplary embodiments are provided. 
         [0005]    An exemplary semiconductor integrated circuit includes a via layer having at least one tilted via; and a wireway layer having at least one elongated wireway disposed above the via layer; wherein the wireway connects to and partially overlaps the tilted via. 
         [0006]    An exemplary method for forming a tilted via connection in a semiconductor integrated circuit includes forming a via layer; patterning a via trench in the via layer; forming a wireway layer; patterning an elongated wireway in the wireway layer; etching the patterned wireway and the patterned via; and filling the etched wireway and the etched via with a conductive material, wherein the filled wireway partially overlaps the filled via. 
         [0007]    Another exemplary method is wherein a portion of the via extends from at least an end of the elongated wireway. Yet another exemplary method is wherein a portion of the via extends from at least a side of the elongated wireway. Still another exemplary method is wherein the filled wireway completely overlaps a top end of the filled via. Another exemplary method is wherein the filled wireway does not overlap a bottom end of the filled via. Yet another exemplary method is wherein the conductive material comprises metal. Still another exemplary method is wherein the conductive material comprises copper (Cu). Another exemplary method is wherein the artificially tilted via connection is realized within a copper dual-damascene process. 
         [0008]    A further exemplary method further includes applying a Chemical Vapor Deposition (CVD) process to close the via trench before patterning the wireway trench. A further exemplary method is wherein the CVD process comprises at least one of SiO2, SiH4, TEOS, OMCTS2.7, p-SiCOH (with k=2.4, 2.2 and lower k) to meet electrical performance criteria. Yet a further exemplary method is wherein the CVD process comprises application of CVD skills and process conditions to control the via Critical Dimensions (CD) in-situ. Still a further exemplary method is wherein the CVD process comprises application of CVD skills and process conditions to control the via Critical Dimensions (CD) ex-situ. 
         [0009]    Another exemplary method has patterning comprising at least one of lithography or Reactive Ion Etching (RIE). Yet another exemplary method has lithography comprising at least one rule to draw the photo mask or to generate an Optical Proximity Correction (OPC). Still another exemplary method has etching comprising at least one of Reactive Ion Etching (RIE) or wet etching. 
         [0010]    Another exemplary method has forming comprising at least one of a barrier metal or seed copper deposition process. Yet another exemplary method has the at least one barrier metal or seed copper deposition process comprising at least one of Pre-Metal Deposition (PMD), Chemical Vapor Deposition (CVD), or Atomic Layer Deposition (ALD). Still another exemplary method has filling comprising copper plating to satisfy gap-filling performance criteria. Another exemplary method has forming comprising deposition of an Inter Layer Dielectric (ILD) layer substantially the same height as the trench to be formed therein. 
         [0011]    The present disclosure will be further understood from the following description of exemplary embodiments, which is to be read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The present disclosure provides integrated circuits and methods for artificially tilted via connections in accordance with the following exemplary figures, in which: 
           [0013]      FIG. 1  shows a schematic side view of a semiconductor integrated circuit having substantially upright via connections; 
           [0014]      FIG. 2  shows a schematic top view of a semiconductor integrated circuit having substantially upright via connections; 
           [0015]      FIG. 3  shows a schematic side view of a semiconductor integrated circuit having artificially tilted via connections in accordance with an exemplary embodiment of the present disclosure; 
           [0016]      FIG. 4  shows a schematic top view of a semiconductor integrated circuit having artificially tilted via connections in accordance with an exemplary embodiment of the present disclosure; 
           [0017]      FIG. 5  shows a schematic side view of a semiconductor integrated circuit after an Inter Layer Dielectric (ILD) deposition step in accordance with an exemplary embodiment of the present disclosure; 
           [0018]      FIG. 6  shows a schematic side view of a semiconductor integrated circuit after a patterning step in accordance with an exemplary embodiment of the present disclosure; 
           [0019]      FIG. 7  shows a schematic side view of a semiconductor integrated circuit after an optional deposition step in accordance with an exemplary embodiment of the present disclosure; 
           [0020]      FIG. 8  shows a schematic side view of a semiconductor integrated circuit after a closing deposition step in accordance with an exemplary embodiment of the present disclosure; 
           [0021]      FIG. 9  shows a schematic side view of a semiconductor integrated circuit after a bulk deposition step in accordance with an exemplary embodiment of the present disclosure; 
           [0022]      FIG. 10  shows a schematic side view of a semiconductor integrated circuit after a trench patterning step in accordance with an exemplary embodiment of the present disclosure; 
           [0023]      FIG. 11  shows a schematic side view of a semiconductor integrated circuit after a trench etching step in accordance with an exemplary embodiment of the present disclosure; 
           [0024]      FIG. 12  shows a schematic side view of a semiconductor integrated circuit after a metal filling step in accordance with an exemplary embodiment of the present disclosure; 
           [0025]      FIG. 13  shows a schematic top view of a semiconductor integrated circuit after a metal filling step in accordance with an exemplary embodiment of the present disclosure; and 
           [0026]      FIG. 14  shows a schematic flow diagram for a method of forming a tilted via connection in a semiconductor integrated circuit in accordance with an exemplary embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0027]    A method for forming semiconductor integrated circuits with artificially tilted via connections is provided. Exemplary embodiments realize artificially tilted metal to via connections in a copper dual-damascene processes. 
         [0028]    Exemplary methods to form a tilted via connection may include Chemical Vapor Deposition (CVD) processes to close contacts that are formed in an Inter Layer Dielectric (ILD) layer, where the ILD layer is the height of the intended via; barrier metal and seed copper deposition processes using technologies such as Pre-Metal Deposition (PMD), Chemical Vapor Deposition (CVD), Atomic Layer Deposition (ALD), and the like; and copper plating technology such as processes to meet gap-filling performance criteria. 
         [0029]    Optionally, the CVD deposition process may include processes such as SiO2 (SiH4, TEOS), OMCTS2.7, p-SiCOH (k=2.4, 2.2 and lower k), and the like, to satisfy electrical performance targets. The CVD deposition process may include the CVD criteria and process conditions to control the via Critical Dimensions (CD) in-situ or ex-situ. Processes for lithography and Reactive Ion Etching (RIE) may be applied for patterning the trenches. 
         [0030]    Lithography techniques may include rules to draw the photo mask, to generate Optical Proximity Correction (OPC), and the like. Etching techniques may include RIE and wet processes. 
         [0031]    As shown in  FIG. 1 , a semiconductor integrated circuit with substantially upright via connections is indicated generally by the reference numeral  100 . The semiconductor integrated circuit  100  includes a first layer  110  having logic structures  112  and  114 ; a second layer  120  having vias  122  and  124  connected to the logic structure  112 ; a third layer  130  having a metal line  132  connected to the via  122 , and a metal line  134  connected to the via  124 ; and a fourth layer  140  having an electrode  142  connected to the metal line  134 . Here, the third layer  130  has a gap  150  between the metal lines  132  and  134 . 
         [0032]    Turning to  FIG. 2 , metal lines and via connections of the semiconductor integrated circuit  100  of  FIG. 1  are indicated generally by the reference numeral  200 . The first metal line  132  completely covers and is connected to the first via  122 ; the second metal line  134  completely covers and is connected to the second via  124 ; a third metal line  232  completely covers and is connected to a third via  222 ; and a fourth metal line  234  completely covers and is connected to a fourth via  224 . Thus, a gap  150  between the metal lines  132  and  134  is smaller than a gap between the vias  122  and  124 . Similarly, a gap  250  between the metal lines  232  and  234  is smaller than a gap between the vias  222  and  224 ; and a gap  252  between the metal lines  232  and  134  is smaller than a gap between the vias  222  and  124 . 
         [0033]    Turning now to  FIG. 3 , a semiconductor integrated circuit with artificially tilted via connections is indicated generally by the reference numeral  300 . The semiconductor integrated circuit  300  includes a first layer  310  having logic structures  312  and  314 ; a second layer  320  having vias  322  and  325  connected to the logic structure  312 ; and a third layer  330  having a metal line  332  connected to the via  322 , and a metal line  335  connected to the via  325 . 
         [0034]    In comparison with the circuit  100  of  FIG. 1 , a gap between the vias  322  and  325  of the circuit  300  of  FIG. 3  is greater than the gap between the vias  122  and  124 . Moreover, a gap between the metal lines  332  and  335  may be greater than the gap between the vias  322  and  325 , and is greater than the gap between the metal lines  132  and  134 . 
         [0035]    Turning to  FIG. 4 , metal lines and via connections of the semiconductor integrated circuit  300  of  FIG. 3  are indicated generally by the reference numeral  400 . The first metal line  332  completely covers and is connected to the first via  322 ; the second metal line  335  partially covers and is connected to the second via  325 ; a third metal line  433  partially covers and is connected to a third via  423 ; and a fourth metal line  435  partially covers and is connected to a fourth via  425 . 
         [0036]    While the second and third metal lines  335  and  433  have their vias  325  and  423  tilted in the elongated length direction of the respective metal lines, the fourth metal line  435  has its via  425  tilted in both the length and width directions. Thus, a gap between the metal lines  332  and  335  is greater than a gap between the vias  322  and  325 . Similarly, a gap between the metal lines  433  and  435  is greater than a gap between the vias  423  and  425 . Moreover, a gap between the metal lines  335  and  433  or  435  is greater than a gap between the vias  325  and  423 . 
         [0037]    Referring to the embodiments of  FIGS. 3 and 4  using artificially-tilted metal via connections, for example, the metal line spacing may be widened without changing the via spacing relative to the examples of  FIGS. 1 and 2 . This increased metal line spacing may result in an improvement of the Time Dependent Dielectric Breakdown (TDDB) performance. 
         [0038]    Turning to  FIG. 5 , a semiconductor integrated circuit after an Inter Layer Dielectric (ILD) deposition step is indicated generally by the reference numeral  500 . The semiconductor integrated circuit  500  includes a first layer  510  having logic structures  512  and  514 ; a first stop layer  516 ; and a second or ILD layer  520 . Here, the ILD layer  520  is preferably deposited to substantially match the intended via height. 
         [0039]    Turning now to  FIG. 6 , a semiconductor integrated circuit after a patterning step is indicated generally by the reference numeral  600 . The semiconductor integrated circuit  600  includes a first layer  610  having logic structures  612  and  614 ; a first stop layer  616 ; and a second layer  620  having first and second via patterns  622  and  624 . 
         [0040]    The patterning of the via contacts may use conventional lithography and Reactive Ion Etching (RIE) processes until touching the stop layer  616 . In addition, the embodiment  600  can preferably achieve more process windows in lithography and Reactive Ion Etching (RIE) in terms of Critical Dimensions (CD), striation and the like by making shallow via patterns. 
         [0041]    Turning now to  FIG. 7 , a semiconductor integrated circuit after an optional deposition step is indicated generally by the reference numeral  700 . The semiconductor integrated circuit  700  includes a first layer  710  having logic structures  712  and  714 ; a first stop layer  716 ; a second layer  720  with via patterns; and an optional thin layer  726 . Advantageously, this optional deposition of an initial thin layer with conformal step coverage permits a decrease in the Critical Dimensions (CD) of the resulting vias. 
         [0042]    As shown in  FIG. 8 , a semiconductor integrated circuit after a closing deposition step is indicated generally by the reference numeral  800 . The semiconductor integrated circuit  800  includes a first layer  810  having logic structures  812  and  814 ; a first stop layer  816 ; a second layer  820  with via patterns  822  and  824 ; an optional thin layer  826 ; and a closing layer  828 . 
         [0043]    Here, the closing deposition step includes depositing a graded layer of Inter Layer Dielectric (ILD) film, and closing the via holes using process conditions with non-conformal step coverage in-situ with either the initial film or the following bulk film. 
         [0044]    Turning now to  FIG. 9 , a semiconductor integrated circuit after a bulk deposition step is indicated generally by the reference numeral  900 . The semiconductor integrated circuit  900  includes a first layer  910  having logic structures  912  and  914 ; a first stop layer  916 ; a second layer  920  with via patterns  922  and  924 ; an optional thin layer  926 ; a closing layer  928 ; and a bulk layer  930 . The deposition of the bulk Inter Layer Dielectric (ILD) film is preferably of sufficient thickness to form the metal trench patterns. 
         [0045]    As shown in  FIG. 10 , a semiconductor integrated circuit after a trench patterning step is indicated generally by the reference numeral  1000 . The semiconductor integrated circuit  1000  includes a first layer  1010  having logic structures  1012  and  1014 ; a first stop layer  1016 ; a second layer  1020  with via patterns  1022  and  1024 ; an optional thin layer  1026 ; a closing layer  1028 ; a bulk layer  1030 ; another stop layer  1036 ; and a trench patterning layer  1040  having a first trench pattern  1042  and a second trench pattern  1044 . Patterning of the trench may be accomplished using conventional or tuned lithography and Reactive Ion Etching (RIE) processes, as well as wet etch processes. 
         [0046]    Turning to  FIG. 11 , a semiconductor integrated circuit after a trench etching step is indicated generally by the reference numeral  1100 . The semiconductor integrated circuit  1100  includes a first layer  1110  having logic structures  1112  and  1114 ; a first stop layer  1116 ; a second layer  1120  with etched via trenches  1122  and  1125 ; an optional thin layer  1126 ; a closing layer  1128 ; a bulk layer  1130  with etched wireway trenches  1132  and  1135  connected to the etched via trenches  1122  and  1125 , respectively; and another stop layer  1136 . Preferably, the bottom of each via is opened under the shadow of Inter Layer Dielectric (ILD). 
         [0047]    Turning now to  FIG. 12 , a semiconductor integrated circuit after a metal filling step is indicated generally by the reference numeral  1200 . The semiconductor integrated circuit  1200  includes a first layer  1210  having logic structures  1212  and  1214 ; a first stop layer  1216 ; a second layer  1220  with metal-filled vias  1222  and  1225 ; an optional thin layer  1226 ; a closing layer  1228 ; a bulk layer  1230  with metal-filled wireways  1232  and  1235  connected to the metal-filled vias  1222  and  1225 , respectively; and another stop layer  1236 . 
         [0048]    The metal filling may be accomplished using copper (Cu), for example, by either conventional or advanced barrier metal and seed copper deposition and plating process. Preferably, Atomic Layer Deposition (ALD) is applied to produce conformal thin films and/or to obtain robust barrier performance. 
         [0049]    As shown in  FIG. 13 , metal lines and via connections of the semiconductor integrated circuit  1200  of  FIG. 12  are indicated generally by the reference numeral  1300 . The first metal line  1232  completely covers and is connected to the first via  1222 ; the second metal line  1235  partially covers and is connected to the second via  1225 ; a third metal line  1333  partially covers and is connected to a third via  1323 ; and a fourth metal line  1335  partially covers and is connected to a fourth via  1325 . 
         [0050]    While the second and third metal lines  1235  and  1333  have their vias  1225  and  1323  tilted in the elongated length direction of the respective metal lines, the fourth metal line  1335  has its via  1325  tilted in both the length and width directions. Thus, a gap between the metal lines  1232  and  1235  is greater than a gap between the vias  1222  and  1225 . Similarly, a gap between the metal lines  1333  and  1335  is greater than a gap between the vias  1323  and  1325 . Moreover, a gap between the metal lines  1235  and  1333  or  1335  is greater than a gap between the vias  1225  and  1323 . 
         [0051]    Thus, the metal lines may be moved to gain more spacing relative to the prior art. Increased spacing of the metal lines results in an improvement of Time Dependent Dielectric Breakdown (TDDB), for example. 
         [0052]    Turning to  FIG. 14 , a method for forming a tilted via connection in a semiconductor integrated circuit is indicated generally by the reference numeral  1400 . The method  1400  includes a start block  1410  that passes control to a function block  1412 . The function block  1412  forms a via layer and passes control to a function block  1414 . The function block  1414  patterns a via trench in the via layer, and passes control to a function block  1416 . The function block  1416 , in turn, forms a wireway layer and passes control to a function block  1418 . The function block  1418  patterns an elongated wireway in the wireway layer and passes control to a function block  1420 . 
         [0053]    The function block  1420 , in turn, etches the patterned wireway and the patterned via and passes control to a function block  1422 . The function block  1422  fills the etched wireway and the etched via with a conductive material, wherein the filled wireway partially overlaps the filled via, and passes control to an end block  1424 . 
         [0054]    In addition, alternate embodiments are contemplated. For example, the artificially tilted vias need not be made of copper (Cu), but may be formed of other metals and/or alternate conductive and/or semi-conductive materials. 
         [0055]    Although illustrative embodiments have been described herein with reference to the accompanying drawings, it is to be understood that the present disclosure is not limited to those precise embodiments, and that various other changes and modifications may be effected therein by those of ordinary skill in the pertinent art without departing from the scope or spirit of the present disclosure. All such changes and modifications are intended to be included within the scope of the present disclosure as set forth in the appended claims.