Abstract:
The present invention relates to a method for fabricating a diffusion barrier layer of a semiconductor device. The method includes the steps of: forming an insulation layer a metal interconnection line; etching the insulation layer, thereby forming an opening to expose a portion of the metal interconnection line; forming a soaking layer on the insulation layer and the opening; forming a diffusion barrier layer on the soaking layer; and filling a metal layer into the opening.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a method for fabricating a semiconductor device; and more particularly, to a method for fabricating a diffusion barrier layer in a semiconductor device.  
       DESCRIPTION OF RELATED ARTS  
       [0002]     In a semiconductor device, a diffusion barrier layer serves a role in delaying diffusion to the maximum extent or preventing a chemical reaction between an interconnection line and a substrate, and between the interconnection lines. A stable diffusion barrier layer is essentially required to develop a reliable semiconductor device. However, the diffusion barrier layer cannot perfectly prevents the diffusion and thus, a capability of the diffusion barrier layer depends on how long the diffusion barrier layer can be durable under various conditions of a thermal process.  
         [0003]     There are required properties for the diffusion barrier layer. The diffusion barrier should be thermodynamically stable even under a condition that the diffusion barrier layer contacts to the interconnection line and the substrate by being formed between the interconnection line and the substrate. Also, the diffusion barrier layer should have excellent adhesion and low contact resistance. Furthermore, the diffusion barrier layer should have strong tolerance to a thermal and mechanical stress, have a similar heat expansion coefficient to the substrate, and have excellent electric conductivity.  
         [0004]     Recently, as a scale of integration of a semiconductor device increases, an aspect ratio of an opening connecting an upper interconnection line with a lower interconnection line greatly increases. A chemical vapor deposition method is used as a method for filling such contact hole having a large aspect ratio by using a metal, for instance, a tungsten (W) layer. Hereinafter, a process for forming a tungsten layer through the use of a chemical vapor deposition method is expressed as a CVD tungsten process.  
         [0005]     As for the above mentioned CVD tungsten process, the tungsten layer uses tungsten hexafluoride (WF 6 ) as a precursor. At this time, a method for precedently depositing titanium nitride (TiN) used as the diffusion barrier layer is employed to prevent the precursor and decomposed components of the precursor from penetrating into lower layers. When depositing the TiN, a physical vapor deposition (PVD) method is mainly used; however, recently as the aspect ratio increases, a chemical vapor deposition (CVD) method is more frequently used.  
         [0006]      FIGS. 1A and 1B  are diagrams briefly illustrating a method for forming a metal contact through a conventional CVD tungsten process.  
         [0007]     Referring to  FIG. 1A , an inter-metal insulation layer  12  is formed on a lower metal interconnection line  11 . Then, the inter-metal insulation layer  12  is etched, thereby forming an opening  13  exposing a portion of the lower interconnection line  11 .  
         [0008]     Next, a diffusion barrier layer  14  is deposited on the contact hole  13  and on the inter-metal insulation layer  12 . Then, a tungsten layer  15  is deposited on the diffusion barrier layer  14  until filling the contact hole  13  through the CVD tungsten process. At this time, the diffusion barrier layer  14  is formed by stacking a titanium (Ti) layer and a titanium nitride (TiN) layer, and when depositing the tungsten layer  15  through the CVD method, a source gas uses tungsten hexafluoride (WF 6 ).  
         [0009]     Referring to  FIG. 1B , a chemical mechanical polishing (CMP) process or an etch-back process is performed. From this process, the diffusion layer  14  and the tungsten layer  15  shown in  FIG. 1A  remain only inside of the contact hole  13  until a surface of the inter-metal insulation layer  12  is exposed. Herein, a reference numeral  15 A denotes a tungsten plug which is a remaining tungsten layer. The tungsten plug  15 A serves a role of a metal contact that connects the lower metal interconnection line  11  with a subsequent upper metal interconnection line.  
         [0010]     Next, another titanium nitride (TiN) layer  16  is deposited on the tungsten plug  15 A as an adhesive layer, and a tungsten layer  17  is deposited on the titanium nitride layer  16 . Then, the tungsten layer  17  and the titanium nitride layer  16  are patterned, thereby forming the upper metal interconnection line.  
         [0011]     In this conventional method, the titanium nitride (TiN) layers are used as the diffusion barrier layer and the titanium (Ti) layer is used as a wetting layer of the TiN layer.  
         [0012]     Since the aspect ratio of the contact hole rapidly increases as a scale of integration of the semiconductor device increase, there requires a lot of changes in the diffusion barrier layer. For instance, in case of a memory device with a size equal to or less than 100 nm, a method directly depositing a thin titanium nitride (TiN) layer through a CVD method without depositing a titanium (Ti) layer is proposed to reduce the contact resistance.  
         [0013]     However, in case of only depositing the TiN layer, the adhesion of the TiN layer with the inter-metal insulation layer deposited below the TiN layer is worsened. Also, since the TiN layer grows with an island type, it is difficult to form a continuous thin layer. Thus, there is a disadvantage that TiN should be deposited with a thickness more than a predetermined thickness to form the continuous thin layer. In addition, an increase in the contact resistance is not avoidable because a resistivity increases as a thickness of the TiN layer increases. That is, the TiN layer deposited through the CVD method has higher resistivity than the tungsten layer, i.e., a main burying metal, thereby inducing an increase in the contact resistance. Also, the contact resistance increases in greater extents because if a thickness of the TiN layer gets thicker to secure the intended role of the TiN layer, i.e., the role as a diffusion barrier layer, a substance having a high resistivity is deposited thickly.  
         [0014]     The increase in the contact resistance as mentioned above may cause a problem that the contact resistance increases in greater extents as the aspect ratio of the contact hole increases.  
         [0015]     Accordingly, it is necessary to deposit the diffusion barrier layer as thinly as possible as not degrading the diffusion barrier capability. Furthermore, it is an essential condition to improve the adhesion between the diffusion barrier layer and the lower layer.  
       SUMMARY OF THE INVENTION  
       [0016]     It is, therefore, an object of the present invention to provide a method for fabricating a semiconductor device having a diffusion barrier layer capable of securing a diffusion barrier capability as having excellent adhesion with lower layers.  
         [0017]     In accordance with one aspect of the present invention, there is provided a method for fabricating a semiconductor device, including the steps of: forming an insulation layer a metal interconnection line; etching the insulation layer, thereby forming an opening to expose a portion of the metal interconnection line; forming a soaking layer on the insulation layer and the opening; forming a diffusion barrier layer on the soaking layer; and filling a metal layer into the opening.  
         [0018]     In accordance with another aspect of the present invention, there is provided a method for fabricating a semiconductor device, including the steps of: forming an insulation layer on a semiconductor layer containing silicon; etching the insulation layer, thereby forming an opening to expose a portion of the semiconductor layer; forming a silicide layer on the exposed portion of the semiconductor layer; forming a soaking layer on the silicide layer and the opening; forming a diffusion barrier layer on the soaking layer; and filling the opening with a metal layer. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     The above and other objects and features of the present invention will become better understood with respect to the following description of the preferred embodiments given in conjunction with the accompanying drawings, in which:  
         [0020]      FIGS. 1A  to  1 B are cross-sectional views briefly illustrating a method for forming a metal contact based on tungsten through employing a conventional chemical vapor deposition method;  
         [0021]      FIGS. 2A  to  2 D are cross-sectional views illustrating a method for forming a diffusion barrier layer made of titanium nitride (TiN) in accordance with the present invention;  
         [0022]      FIGS. 3A  to  3 D are cross-sectional views illustrating a method for fabricating a contact formed on an interconnection line in accordance with the present invention;  
         [0023]      FIGS. 4A  to  4 E are cross-sectional views illustrating a method for fabricating a contact formed on silicon in accordance with the present invention; and  
         [0024]      FIGS. 5A  to  5 E are cross-sectional views illustrating a method for fabricating a contact formed on silicon in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]     Hereinafter, detailed descriptions on preferred embodiments of the present invention will be provided with reference to the accompanying drawings.  
         [0026]     Preferred embodiments of the present invention propose a method for fabricating a thin titanium nitride (TiN) diffusion barrier layer capable of securing a diffusion barrier capability as having excellent adhesion with lower layers by introducing a soaking technology with use of boron (B).  
         [0027]      FIGS. 2A  to  2 D are cross-sectional views illustrating a method for forming a diffusion barrier layer made of titanium nitride (TiN) in accordance with the present invention.  
         [0028]     Referring to  FIG. 2A , as for a chemical vapor deposition (CVD) method for forming a TiN layer through a molecular reaction between titanium tetrachloride (TiCl 4 ) and ammonia (NH 3 ), diborane (B 2 H 6 )  22  as a soaking material is precedently introduced into a substrate  21  heated at a temperature ranging from approximately 100° C. to approximately 800° C. to induce a reaction. At this time, a pressure of a chamber is maintained in a range from approximately 0.1 mtorr to approximately 100 torr.  
         [0029]     Referring to  FIG. 2B , when the B 2 H 6    22  is introduced into the chamber, a number of soaking layers  23  are formed on a surface of the substrate  21 . Herein, the soaking material serves a role in increasing the adhesion and helps the diffusion barrier layer to be grown in a layer-by-layer type by pre-treating the substrate  21  before depositing the diffusion barrier layer. A layer formed on the surface of the substrate after a surface pre-treatment process is called a soaking layer.  
         [0030]     Referring to  FIG. 2C , after forming the soaking layers  23 , e.g., the boron layers, gases including TiCl 4    24  and NH 3    25  are introduced into the substrate  21 .  
         [0031]     Referring to  FIG. 2D , if injecting the gases including TiCl 4    24  and NH 3    25 , TiN nuclei are uniformly generated on the surface of the substrate  21  in a rapid speed because the borons adsorbed on the surface of the substrate  21  are rapidly reacted with TiCl 4    24 . Thus, a thin TiN layer  26  is continuously formed with a size ranging from approximately 1 nm to approximately 10 nm. At this time, reactive byproducts of chlorine (Cl) and hydrogen (H) are evaporated. Herein, a reference numeral  27  denotes these byproducts.  
         [0032]     According to  FIGS. 2A  to  2 D, the adhesion of the TiN layer  26  with the lower layers, i.e., the soaking layers  23 , is greatly improved due to an uniform generation of the TiN nuclei and an wetting property of B.  
         [0033]     Although the B 2 H 6    22  is exemplified as a main component to form the soaking layers  23  in  FIGS. 2A  to  2 D, silane (SiH 4 ) can also be used as a main component to form the soaking layers. It is also possible to form the soaking layers  23  by performing a pre-treatment process with use of a plasma. The pre-treatment process is implemented by directly forming a plasma within a reactor including the soaking material with supplying a radio frequency (RF) or a direct current (DC) power above a substrate heated at a temperature ranging from approximately 0° C. to approximately 800° C. Also, the pre-treatment process is implemented by activating the soaking material with use of a remote plasma made of an inert gas such as argon (Ar); and pre-treating the surface of a substrate by using the activated soaking material.  
         [0034]      FIGS. 3A  to  3 D are cross-sectional views illustrating a a method for forming an opening formed on the interconnection line in accordance with a first embodiment of the present invention, wherein a method for forming a diffusion barrier layer shown in  FIGS. 2A  to  2 D is applied to the opening formation method.  
         [0035]     Referring to  FIG. 3A , an inter-layer insulation layer or an inter-metal insulation layer  32  is formed on a lower metal interconnection line  31 . Although the inter-metal insulation layer  32  is used for an explanation in the first embodiment, the present invention can apply to an inter-layer insulation layer. Afterwards, the inter-metal insulation layer  32  is etched to form an opening  33  exposing a portion of the lower metal interconnection line  31 . The lower metal interconnection line  31  can be formed by using a material selected from a group consisting of tungsten (W), aluminum (Al), copper (Cu), titanium (Ti), titanium nitride (TiN), tantalum nitride (TaN), tantalum (Ta) and tungsten nitride (WN), and an upper metal interconnection line which will be formed later can be formed by using one of Al and Cu besides the W layer.  
         [0036]     Referring to  FIG. 3B , as B 2 H 6    34  serving as a soaking material is introduced into a CVD chamber maintained at a temperature ranging from approximately 400° C. to approximately 700° C., a glue layer  35  for absorbing the injected B 2 H 6    34  is formed in the contact hole  33  and on the inter-metal insulation layer  32 . Herein, the glue layer  35  is formed by adsorbing borons from the B 2 H 6    34  until it grows from a sub-monolayer to several monolayers.  
         [0037]     Referring to  FIG. 3C , as predetermined gases  36  including TiCl 4    24  and NH 3    36  are introduced into the CVD chamber, TiN nuclei are uniformly generated on the glue layer  35  in a rapid speed because the glue layer  35  is rapidly reacted with the TiCl 4  of the predetermined gases  36 . Thus, a thin TiN layer  37  is continuously formed with a size ranging from approximately 1 nm to approximately 10 nm. At this time, reactive byproducts of chlorine (Cl) and hydrogen (H) are evaporated.  
         [0038]     Referring to  FIG. 3D , a tungsten layer  38  is deposited on the thin TiN layer  37  through a CVD method until being filled into the contact hole  33 . Herein, when depositing the tungsten layer  38  through the CVD method, tungsten hexafluoride (WF 6 ) is used as a source gas.  
         [0039]     In accordance with the above embodiment, a process for introducing the soaking material can be performed in a separate chamber from the CVD chamber for forming the TiN layer. However, if the injection process of the soaking material is performed in-situ at the identical chamber to the CVD chamber, an improvement on a throughput and cost-effectiveness can be achieved.  
         [0040]     In accordance with the above embodiment, the thin TiN layer  37  is formed on the glue layer  35  as a diffusion barrier layer. The thin TiN layer  37  is thin and uniform and, has excellent adhesion since the thin TiN layer  37  is formed on the glue layer  35 .  
         [0041]      FIGS. 4A  to  4 E are cross-sectional views illustrating a method for forming an opening on a silicon substrate in accordance with a second embodiment of the present invention, wherein a method for forming a diffusion barrier layer shown in  FIGS. 2A  to  2 D is applied to the opening formation method.  
         [0042]     Referring to  FIG. 4A , an inter-layer insulation layer  42  is formed on a semiconductor layer  41  containing silicon. Afterwards, the inter-layer insulation layer  42  is etched, thereby forming an opening  43  exposing a portion of the semiconductor layer  41 .  
         [0043]     Referring to  FIG. 4B , a chemical vapor deposition (CVD) method is employed to form a Ti layer  44 . For the CVD method, TiCl 4  and H 2  gases are used. At this time, the Ti layer  44  is deposited on a portion of the semiconductor layer  41  exposed by the contact hole  43 , inner walls of the contact hole  43  and the inter-layer insulation layer  42 .  
         [0044]     Meanwhile, since the deposition of the Ti layer is performed at a high temperature ranging from approximately 400° C. to approximately 700° C., silicon from the semiconductor layer  41  and Ti from the Ti layer  44  react with each other during depositing the Ti layer  44 , thereby forming a titanium silicide (TiSi 2 ) layer  45  on the portion of the semiconductor layer  41  exposed by the opening.  
         [0045]     As mentioned above, it is possible to form the TiSi 2  layer  45  as simultaneously as to deposit the Ti layer  44  because an additional thermal process Is not required owing to the fact that the CVD method for forming the Ti layer  44  is performed in a high temperature.  
         [0046]     Referring to  FIG. 4C , the semiconductor layer  44  on which the Ti layer  44  is deposited is transferred to the CVD chamber maintained at a temperature ranging from approximately 400° C. to approximately 700° C. Afterwards, B 2 H 6    46  is introduced into the CVD chamber as a soaking material and then, a B 2 H 6  based glue layer  47  is formed on the Ti layer  44 . Herein, the B 2 H 6  based glue layer  47  is formed with B originated from the B 2 H 6    46  and grows from a sub-monolayer to several monolayers.  
         [0047]     Referring to  FIG. 4D , as predetermined gases  48  including TiCl 4  and NH 3  are injected, TiN nuclei are uniformly generated on the B 2 H 6  based glue layer  47  in a rapid speed because the B 2 H 6  based glue layer  47  is rapidly reacted with the TiCl 4  of the predetermined gases  48 . Thus, a thin TiN layer  49  is continuously formed with a size ranging from approximately 1 nm to approximately 10 nm. At this time, reactive byproducts of Cl and H 2  are evaporated.  
         [0048]     Referring to  FIG. 4E , a tungsten layer  50  is deposited on the thin TiN layer  49  until being filled into the contact hole  43 . At this time, during depositing the tungsten layer  50  through a CVD method, WF 6  is used as a source gas.  
         [0049]     As explained in  FIGS. 4A  to  4 E, in case of forming the opening on the semiconductor layer containing silicon, the TiSi 2  layer is formed at a bottom portion of the opening for the purpose of reducing a contact resistance and then, the thin TiN layer acting as a diffusion barrier layer is formed. Herein, the B 2 H 6  based glue layer provides an advantage of preventing Cl included in the TiCl 4  gas from inducing damage to the TiSi 2  layer during depositing the thin TiN layer  49  with use of the TiCl 4  and NH 3  gases.  
         [0050]     In addition to the titanium silicide (Si 2 ) layer, one of tantalum silicide (TaSi 2 ), tungsten silicide (WSi 2 ), cobalt silicide (CoSi 2 ), and nickel silicide (NiSi 2 ) can be employed as the silicide material formed on the predetermined portion of the opening. Thus, it is further possible to use one of tantalum (Ta), tungsten (W), cobalt (Co), and nickel (Ni) in addition to the Ti layer formation.  
         [0051]      FIGS. 5A  to  5 E are cross-sectional views illustrating a method for forming an opening formed on silicon, wherein a method for forming a diffusion barrier layer shown in  FIGS. 2A  to  2 D is applied to the opening formation method.  
         [0052]     Referring to  FIG. 5A , an inter-layer insulation layer  52  is formed on a semiconductor layer  51  containing silicon and then, an opening  53  exposing a portion of the semiconductor layer  51  is formed by etching the inter-layer insulation layer  52 .  
         [0053]     Referring to  FIG. 5B , a TiSi 2  layer  54  is formed directly on a portion of the semiconductor layer  51  exposed by the opening  53  by performing a salicide process.  
         [0054]     Herein, the salicide process proceeds by employing several sequential steps. Although not illustrated, a Ti layer is first formed by performing a physical vapor deposition (PVD) method. Then, a predetermined thermal process is adopted to induce a reaction between the semiconductor layer  51  including silicon and the Ti layer, thereby forming the TiSi 2  layer  54  on the portion of the semiconductor layer  51  exposed by the opening  53 . Afterwards, non-reacted titanium molecules are removed.  
         [0055]     Referring to  FIG. 5C , the semiconductor layer  51  with the TiSi 2  layer  54  is loaded to a CVD chamber maintained at a temperature ranging from approximately 400° C. to approximately 700° C. Afterwards, as B 2 H 6    55  serving as a soaking material is injected into the CVD chamber, a B 2 H 6  based glue layer  56  is formed on the inter-layer insulation layer  52 , and the TiSi 2  layer  54 . Herein, the B 2 H 6  based glue layer  56  is formed as borons contained in the soaking material, i.e., the B 2 H 6    55  are adsorbed on the B 2 H 6  based glue layer  56  and grows from a sub-monolayer to several monolayers.  
         [0056]     Referring to  FIG. 5D , as predetermined gases  57  including TiCl 4  and NH 3  are introduced into the CVD chamber, TiN nuclei are uniformly generated in a rapid speed because the B 2 H 6  based glue layer  56  is rapidly reacted with the TiCl 4  gas of the predetermined gases  57 . Thus, a thin TiN layer  58  is continuously formed with a size ranging from approximately 1 nm to approximately 10 nm. At this time, reactive byproducts of Cl and H 2  are evaporated.  
         [0057]     Referring to  FIG. 5E , a tungsten layer  59  is deposited on the thin TiN layer  58  until being filled into the contact hole  53 . At this time, during depositing the tungsten layer  59  through the CVD method, WF 6  is used as a source gas.  
         [0058]     As described through  FIG. 5A  to  FIG. 5E , in case of forming the opening on the semiconductor layer containing silicon, the TiSi 2  layer is formed at a bottom portion of the opening for reducing the contact resistance and then, the thin TiN layer acting as a diffusion barrier layer is formed. Herein, the B 2 H 6  based glue layer provides an advantage of preventing Cl included in the TiCl 4  gas from inducing damage to the TiSi 2  layer during depositing the thin TiN layer with use of TiCl 4  and NH 3 .  
         [0059]     In addition to the TiSi 2  layer, it is possible to employ one of TaSi 2 , WSi 2 , CoSi 2 , and NiSi 2 .  
         [0060]     In addition, tantalum nitride (TaN), tungsten nitride (WN), titanium tungsten (TiW) and an amorphous metal that are used as the diffusion barrier layer can be uniformly formed in a thin thickness while being capable of functioning the diffusion barrier layer as simultaneously as having excellent adhesion obtained by introducing the soaking technology.  
         [0061]     The present invention provides effects of reducing a metal contact resistance of a highly integrated semiconductor device and improving adhesion of the TiN layer used as the diffusion barrier layer against the tungsten layer with lower layers disposed beneath the TiN layer.  
         [0062]     Furthermore, since the thin TiN layer is highly densified, a property of the diffusion barrier layer is enhanced and, since the diffusion barrier layer is formed through the CVD method under the presence of the glue layer containing the soaking material, the lower layers can be protected from contaminations, e.g., halogen elements, which can be generated from precursors used in the CVD method.  
         [0063]     The present application contains subject matter related to the Korean patent application No. KR 2004-0031921, filed in the Korean Patent Office on May 6, 2004, the entire contents of which being incorporated herein by reference.  
         [0064]     While the present invention has been described with respect to certain preferred embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.