Patent Document

CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims priority to and the benefit of Korean Patent Application 10-2004-0053021, filed in the Korean Intellectual Property Office on Jul. 8, 2004, the entire contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   (a) Field of the Invention 
   The present invention relates to a method for manufacturing a semiconductor device. More particularly, the present invention relates to a method for fabricating a metal line in a semiconductor device. 
   (b) Description of the Related Art 
   As a semiconductor device becomes more integrated and smaller sized, a gap between lower and upper metal lines is becoming narrower. When the gap between the lower and upper metal lines becomes narrower, a delay of a time constant may increase and thereby an operation speed of the device may decrease. Therefore, for a narrower gap between the lower and upper metal lines, a semiconductor device should be fabricated more precisely. 
     FIG. 1A  to  FIG. 1C  are sectional views illustrating a conventional process of forming a multiple layer metal line in a semiconductor device. 
   As shown in  FIG. 1A , a lower metal line  12  is formed on a semiconductor substrate  11  having structures of various circuit elements for a semiconductor device thereon and/or therein (e.g., one or more transistors, capacitors, resistors, diodes, etc.), and then a first etch stop layer  13  is formed on the substrate  11  having the lower metal line  12 . Subsequently, a first insulating layer  14   a , a second etch stop layer  14   b , and a second insulating layer  14   c  are consecutively formed on the first etch stop layer  13  such that an interlayer insulating layer  14  is formed for insulation between metal lines. Then, the first interlayer insulating layer  14  is etched utilizing a dual damascene etching process so as to form a dual damascene pattern  15 . 
   In more detail, the dual damascene pattern  15  is formed as follows. After the first insulating layer  14   a  and the second etch stop layer  14   b  are formed on the first etch stop layer  13 , the second etch stop layer  14   b  is partially etched and then the second insulating layer  14   c  is formed on the second etch stop layer  14   b . Subsequently, a trench  15   a  is formed by partially etching the second insulating layer  14   c , and then a via contact hole  15   b  partially exposing the lower metal line  12  is formed by partially etching the first insulating layer  14   a . Thus, the dual damascene pattern  15  is formed to have the trench  15   a  and the via contact hole  15   b.    
   As shown in  FIG. 1B , a diffusion barrier  16  is formed to cover the semiconductor substrate  11  having the dual damascene pattern  15 , and then a copper layer  17  is deposited on the diffusion barrier  16 . 
   When the metal layer  17  is deposited, a top surface of the metal layer  17  undulates due to undulation in an outline of the dual damascene pattern  15  formed on the interlayer insulating layer  14 . 
   For that reason, as a primary planarization process, the top surface of the metal layer  17  is planarized by selectively polishing by a chemical mechanical polishing (CMP) process. That is, the metal layer  17  is polished until the diffusion barrier  16  becomes exposed, and thus the surface of the metal layer  17  becomes more flat. 
   Subsequently, as shown in  FIG. 1C , as a secondary planarization process, another CMP process is performed on the metal layer  17  and the diffusion barrier  16  taking the interlayer insulating layer  14  as an end point, and thereby a metal line is formed in the dual damascene pattern  15 . Consequently, an upper metal line  18  is formed in the dual damascene pattern  15  to be connected with the lower metal line  12  through the via contact hole  15   b.    
   However, according to such a conventional method for forming a metal line in a semiconductor device, the metal line may problematically suffer from a dishing phenomenon that is apt to occur in the trench  15   a  during the secondary planarization process performed for forming the metal line  18  in the dual damascene pattern  15 . Such a dishing phenomenon deteriorates an electrical conductivity of the metal line, and it makes a subsequent process become more difficult. 
   The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person or ordinary skill in the art. 
   SUMMARY OF THE INVENTION 
   The present invention has been made in an effort to provide a method for fabricating a metal line in a semiconductor device having advantages of enhancement of performance and yield of the semiconductor device by enhancing planarity of metal line due to forming an anti-oxidation layer on a metal layer for reducing a removal rate of the metal layer. 
   The above-mentioned dishing phenomenon may be prevented by forming a dummy pattern (for example, a thick dummy metal layer) at a region of the dishing after filling the dual damascene pattern  15  with a metal material of, e.g., copper. However, forming such a dummy pattern may increase the time for the planarization process and cost therefor. 
   An exemplary method for fabricating a metal line in a semiconductor device according to an embodiment of the present invention includes: forming an etch stop layer on a substrate; forming an interlayer insulating layer on the etch stop layer, the interlayer insulating layer comprising a plurality of dual damascene patterns, each respectively having a trench and at least one via contact hole; forming a barrier metal layer and a line metal layer on the interlayer insulating layer including in the dual damascene patterns; forming an anti-oxidation layer above the line metal layer; and forming a metal line in the dual damascene pattern by polishing (e.g., performing a CMP process on) an entire surface of the anti-oxidation layer. 
   In various embodiments, a TiN/Ti layer or a TaN/Ta layer may be used as the barrier metal layer; the anti-oxidation layer may be formed before or after a cleaning process, and after an edge bead removal (EBR) process is performed during the step of forming the line metal layer; forming the line metal layer and the anti-oxidation layer may comprise depositing and then annealing; and/or the anti-oxidation layer may be deposited by a spin coating method, a CVD method, a spray method, or a dip method. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  to  FIG. 1C  are sectional views illustrating a conventional process of forming a multiple layer metal line in a semiconductor device. 
       FIG. 2A  to  FIG. 2C  are sectional views illustrating a process of forming a multiple layer metal line in a semiconductor device according to an exemplary embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
   An embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
     FIG. 2A  to  FIG. 2C  are sectional views illustrating a process of forming a multiple layer metal line in a semiconductor device according to an exemplary embodiment of the present invention. 
   As shown in  FIG. 2A , a lower metal line  102  is formed on a semiconductor substrate  101  having various circuit element structures for a semiconductor thereon and/or therein, generally by conventional photolithographic processing. Thus, the lower metal line  102  generally comprises aluminum or a conventional Al—Cu alloy, which may have one or more barrier layers thereunder (e.g., a stacked Ti/TiN bilayer) and/or one or more capping layers thereover (e.g., a stacked Ti/TiN or Ti/TiW bilayer). Then, a first etch stop layer  103  (e.g., comprising silicon nitride) is formed on the substrate  101  having the lower metal line  102 . Subsequently, a first insulating layer  104   a  (generally comprising silicon dioxide), a second etch stop layer  104   b  (e.g., silicon nitride), and a second insulating layer  104   c  (generally comprising silicon dioxide) are consecutively formed on the first etch stop layer  103  such that an interlayer insulating layer  104  is formed for insulation between metal lines. The silicon dioxide for first insulating layer  104   a  may be doped in part with fluorine (e.g., to form an undoped silicate glass [USG]/fluorosilicate glass [FSG] or USG/FSG/USG stack), or with boron and/or phosphorous (e.g., a borophosphosilicate glass). The material for the second insulating layer  104   c  is generally selected from those materials for the first insulating layer  104   a , but it may be the same as or different from the material(s) for the first insulating layer  104   a . Then, the first interlayer insulating layer  104  is etched utilizing a dual damascene etching process so as to form a dual damascene pattern  105 . 
   In more detail, the dual damascene pattern  105  may be formed as follows. After the first insulating layer  104   a  and the second etch stop layer  104   b  are formed on the first etch stop layer  103 , the second etch stop layer  104   b  is partially etched and then the second insulating layer  104   c  is formed on the second etch stop layer  104   b . Subsequently, a trench  105   a  is formed by selectively etching the second insulating layer  104   c  (e.g., using a first patterned photoresist as a mask), and then a via contact hole  105   b  partially exposing the lower metal line  102  is formed by selectively etching the first insulating layer  104   a  (e.g., using a second patterned photoresist as a mask). Thus, the dual damascene pattern  105  generally has a trench  105   a  and a via contact hole  105   b.    
   As shown in  FIG. 1B , a barrier metal layer  106  is formed to cover the semiconductor substrate  101  having the dual damascene pattern  105 , and then a metal layer  107  comprising copper is deposited (generally by electroplating) on the barrier metal layer  106 . Then, an anti-oxidation layer  108  is formed to cover the metal layer  107 . 
   When the copper metal layer  107  is deposited without an overlying anti-oxidation layer, a top surface of the metal layer  107  may dip or undulate (that is, dishing area  109  may occur thereon) due to undulation in an outline of the dual damascene pattern  105  formed on the interlayer insulating layer  104 , a phenomenon generally known as “dishing” that results from chemical-mechanical polishing of copper or other metal. The anti-oxidation layer  108  generally reduces or prevents deterioration of a characteristic of a semiconductor device by the dishing area  109 . The anti-oxidation layer  108  may be formed before or after a cleaning process (e.g., before or after cleaning the substrate having the metal layer  107  thereon), after performing edge bead removal (EBR) during or after forming of the metal layer  107  (e.g., after removing an edge bead from the metal layer  107 ), or before an annealing process after depositing the copper for forming the metal layer  107  (e.g., after depositing and before annealing the metal layer  107 ). 
   The anti-oxidation layer  108  may be formed on the metal layer  107  by various methods, such as spin coating, a chemical vapor deposition (CVD) method, spraying (e.g., spraying a solution of antioxidizing material onto the metal layer  107 ), dipping (e.g., dipping the wafer or substrate having the metal layer  107  thereon into a solution of antioxidizing material), and an exposure method (e.g., exposing the metal layer  107  to a vapor or gas containing one or more antioxidizing materials). In the dip method, the anti-oxidation layer  108  covers the metal layer  107  by dipping the semiconductor substrate  101  with the metal layer thereon  107  into an anti-oxidizing material. In the exposure method, the semiconductor substrate  101  having an exposed metal layer  107  thereon is exposed to a chemical material for preventing oxidization. 
   In general, the anti-oxidation layer may comprise various materials (for example, various kinds of polymeric films, such as thermoplastic resins, conventional resist polymers, etc.; dielectric films, gold coatings, chromate films, etc.). Among these materials, a chromate film that may be formed by an electrolytic chromate treatment of the wafer or substrate having the metal layer  107  thereon may be preferred. However, the same effect may be achieved to a similar degree by any of the exemplary materials listed above. 
   Since the anti-oxidation layer  108  is formed on the metal layer  107  as such, the metal layer  107  may be protected from an oxidizing agent used during planarization during a later-described planarization or polishing process (i.e., a CMP process). 
   Subsequently, as shown in  FIG. 2C , a polishing (CMP) process is performed to a degree that a surface of the second insulating layer  104   c  may be exposed. By such a process, the surfaces of the metal layer  107  and the anti-oxidation layer  108  become planarized, and thereby the upper metal line  110  is formed. In fact, the anti-oxidation layer  108  may be completely removed by the polishing process, and in general, the surfaces of the metal layer  107  and the second insulating layer  104   c  may become coplanar. 
   In more detail, during the CMP process, the dishing area  109  is more planarized by a chemical polishing or etching mechanism than by a mechanical polishing mechanism (i.e., it is planarized by removing the copper of the metal layer  107  after changing it into an ionic state by an oxidizing agent, such as an acid). The barrier metal layer  106 , the metal layer  107 , and the anti-oxidation layer  108  formed above the uppermost surface of the second insulating layer  104   c  may be removed by a mechanical polishing mechanism more than by a chemical polishing mechanism. Here, when the metal layer  107  in the dishing area  109  is removed by the oxidizing agent, the anti-oxidation layer  108  lowers an oxidation rate of the metal layer  107 . Therefore, the metal layer  107  may be removed to a lesser degree at the dishing area  109  than an area above the uppermost surface of the second insulating layer  104   c . Therefore, the dishing phenomenon becomes lessened, and the upper metal line  110  may be more planarized or more flat. 
   As described above, according to an exemplary method for fabricating a metal line in a semiconductor device, performance and yield of the semiconductor device may be improved by enhancing planarity of metal line due to forming an anti-oxidation layer on a metal layer. The anti-oxidation layer is believed to reduce a removal rate of the metal layer in locations where dishing may occur. In addition, since an anti-oxidation layer is formed above a metal layer, the metal layer may be deposited at a minimal thickness in order to minimize the amount of the metal layer to be removed by a planarization or CMP process. Therefore, the time and cost for the CMP process may be reduced, and waste water containing a heavy metal may also be reduced. 
   While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Technology Category: 5