Patent Abstract:
The present invention proposes a method of forming a dual contact plug, comprising steps of: forming a source/drain region and a sacrificed gate structure on a semiconductor substrate, the sacrificed gate structure including a sacrificed gate; depositing a first inter-layer dielectric layer; planarizing the first inter-layer dielectric layer to expose the sacrificed gate in the sacrificed gate structure; removing the sacrificed gate and depositing to form a metal gate; etching to form a first source/drain contact opening in the first inter-layer dielectric layer; sequentially depositing a liner and filling conductive metal in the first source/drain contact opening to form a first source/drain contact plug; depositing a second inter-layer dielectric layer on the first inter-layer dielectric layer; etching to form a second source/drain contact opening and a gate contact opening in the second inter-layer dielectric layer; and sequentially depositing a liner and filling conductive metal in the second source/drain contact opening and the gate contact opening to form a second source/drain contact plug and a gate contact plug. The present invention also proposes a semiconductor device manufactured by the above process.

Full Description:
PRIORITY APPLICATION(S) 
     This patent application claims the benefit of priority, under 35 U.S.C. §120, to PCT Patent Application Number PCT/CN2010/000836; which patent application claims the benefit of priority, under 35 U.S.C. §119, to Chinese Patent Application Serial Number 200910092514.3, filed Sep. 16, 2009, the entire contents of which are incorporated herein by reference in their entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates to semiconductor field, especially to semiconductor devices and manufacturing methods thereof, and more particularly, to a method of forming a dual contact plug for replacement gate and a semiconductor device manufactured by means of the method. 
     2. Description of Prior Art 
     With the increasingly smaller size of semiconductor device, inter-layer contacts and contact plugs (CA) must become smaller, and distances therebetween also become shorter and shorter. Fabricating increasingly smaller contacts and contact plugs by using conventional processes presents a number of problems. (1) As an etching depth on gate is different from that in source/drain regions, shorts may likely occur between a contact plug and the gate. (2) As an etching depth in the source/drain regions is large whereas a size of openings thereof is small (i.e., it has a small width/height ratio), a number of process defects such as underetch, cavities in metal-filling plugs, and so on may be caused. Thus, the selection of processes is restricted, and the parasitic resistance increases. 
     Hereunder, by referring to  FIG. 1 , the problems in the conventional processes will be described in details.  FIG. 1  is a schematic diagram of a semiconductor device manufactured according to the conventional process. As shown in  FIG. 1 , the semiconductor device manufactured according to the conventional process mainly comprises: a Si substrate  100 , an Inter-Layer Dielectric (ILD) layer  180 , silicide regions  110 , a metal gate  120 , source/drain contact plugs  140 , and a gate contact plug  130 . The metal gate  120  is formed on a high-k dielectric layer  170  which is deposited on the Si substrate  100 . A spacer  160  is formed to surround the high-k dielectric layer  170  and the metal gate  120 . The inter-layer dielectric layer  180  is deposited on the Si substrate  100 . The silicide regions  110  is formed on and embedded in the Si substrate  100 . The source/drain contact plugs  140  and the gate contact plug  130  are formed in the inter-layer dielectric layer  180 , in which the source/drain contact plugs  140  are in contact with the silicide regions  110  respectively and the gate contact plug  130  is in contact with the metal gate  120 . Each of the source/drain contact plugs  140  and the gate contact plug  130  includes a liner  125  and conductive metal filled therein. As illustrated in  FIG. 1 , the etching depth Hca_gate of the etching process for forming the gate contact plug  130  is different from the etching depth Hca_sd of the etching process for forming the source/drain contact plugs  140 ; the source/drain contact plugs  140  have a smaller width/height ratio, so in forming the source/drain contact plugs  140 , the number of process defects such as underetch, cavities in metal-filling plugs, and so on may exist therein more likely. Moreover, since the etching process for the source/drain contact plugs  140  has much stricter requirements, shorts between the source/drain contact plugs  140  and the metal gate  120  (denoted by the dashed line in  FIG. 1 ) may be resulted in with a greater possibility. 
     SUMMARY OF THE INVENTION 
     In view of the above drawbacks of the conventional processes, the present invention proposes a method of forming a dual contact plug for replacement gate such that source/drain contact plugs and gate contact plug having the same depth are formed on the source/drain regions and the gate region, so the shorts between the source/drain contact plugs and the gate are avoided, and at the same time, the processes defects are prevented. Additionally, the present invention is compatible with the replacement gate process. 
     According to the first aspect of the present invention, there is provided a method of forming a dual contact plug comprising steps of: forming a source/drain region and a sacrificed gate structure on a semiconductor substrate, the sacrificed gate structure including a sacrificed gate; depositing a first inter-layer dielectric layer; planarizing the first inter-layer dielectric layer to expose the sacrificed gate in the sacrificed gate structure; removing the sacrificed gate and depositing to form a metal gate by means of replacement gate process; etching to form a first source/drain contact opening in the first inter-layer dielectric layer by means of lithography so that the source/drain region formed on the semiconductor substrate is exposed at the bottom of the first source/drain contact opening; sequentially depositing a liner and filling conductive metal in the first source/drain contact opening to form a first source/drain contact plug; depositing a second inter-layer dielectric layer on the first inter-layer dielectric layer with the first source/drain contact plug formed therein; etching to form a second source/drain contact opening and a gate contact opening in the second inter-layer dielectric layer by means of lithography so that the first source/drain contact plug is exposed at the bottom of the second source/drain contact opening and the metal gate is exposed at the bottom of the gate contact opening; and sequentially depositing a liner and filling conductive metal in the second source/drain contact opening and the gate contact opening to form a second source/drain contact plug and a gate contact plug. 
     Preferably, the first source/drain contact plug is narrower than the second source/drain contact plug and the gate contact plug. More preferably, the width of the first source/drain contact plug is 15-100 nm, the width of the second source/drain contact plug is 20-150 nm, and the width of the gate contact plug is 20-150 nm. 
     Preferably, the conductive metal in the second source/drain contact plug and the gate contact plug has a resistivity smaller than that of the conductive metal in the first source/drain contact plug. 
     Preferably, the first inter-layer dielectric layer includes at least one selected from undoped silicon oxide (SiO 2 ), doped silicon oxide (e.g., Boro-Silicate Glass (BSG) and Boro-Phospho-Silicate Glass (BPSG)) and silicon nitride (Si 3 N 4 ), and the second inter-layer dielectric layer includes at least one selected from undoped silicon oxide (SiO 2 ), doped silicon oxide (e.g., BSG and BPSG) and silicon nitride (Si 3 N 4 ). 
     Preferably, the method further comprises a step of: forming a barrier liner entirely on the semiconductor substrate with the source/drain region and the sacrificed gate structure formed thereon, before depositing the first inter-layer dielectric layer. Herein, the barrier liner includes Si 3 N 4  and has a thickness of 10-50 nm. 
     Preferably, the method further comprises a step of: forming a barrier layer entirely on the first inter-layer dielectric layer with the first source/drain contact plug formed therein, before depositing the second inter-layer dielectric layer. Herein, the barrier layer includes Si 3 N 4  and has a thickness of 10-50 nm. 
     Preferably, the liner includes at least one selected from TiN, TaN, Ta and Ti, and the conductive metal includes at least one selected from Ti, Al, TiAl, Cu and W. 
     Preferably, the thickness of the first inter-layer dielectric layer is 15-50 nm, and the thickness of the second inter-layer dielectric layer is 25-90 nm. 
     According to a second aspect of the present invention, there is provided a semiconductor device comprising: a semiconductor substrate having a source/drain region and a gate structure formed thereon, the gate structure including a metal gate; a first inter-layer dielectric layer deposited on the semiconductor substrate and having a first source/drain contact plug formed therein, the first source/drain contact plug being in contact with the source/drain region; and a second inter-layer dielectric layer deposited on the first inter-layer dielectric layer and having a second source/drain contact plug and a gate contact plug formed therein, the second source/drain contact plug being in contact with the first source/drain contact plug, and the gate contact plug being in contact with the metal gate. 
     Preferably, the second source/drain contact plug and the gate contact plug have the same depth. 
     Preferably, each of the first source/drain contact plug, the second source/drain contact plug and the gate contact plug includes a liner and conductive metal filled therein. More preferably, the conductive metal in the second source/drain contact plug and the gate contact plug has a resistivity smaller than that of the conductive metal in the first source/drain contact plug. More preferably, the liner includes at least one selected from TiN, TaN, Ta and Ti, and the conductive metal includes at least one selected from Ti, Al, TiAl, Cu and W. 
     Preferably, the first source/drain contact plug is narrower than the second source/drain contact plug and the gate contact plug. More preferably, the width of the first source/drain contact plug is 15-100 nm, the width of the second source/drain contact plug is 20-150 nm, and the width of the gate contact plug is 20-150 nm. 
     Preferably, the first inter-layer dielectric layer includes at least one selected from undoped silicon oxide (SiO 2 ), doped silicon oxide (e.g., Boro-Silicate Glass (BSG) and Boro-Phospho-Silicate Glass (BPSG)) and silicon nitride (Si 3 N 4 ), and the second inter-layer dielectric layer includes at least one selected from undoped silicon oxide (SiO 2 ), doped silicon oxide (e.g., BSG and BPSG) and silicon nitride (Si 3 N 4 ). 
     Preferably, the semiconductor device further comprises: a barrier liner formed between the first inter-layer dielectric layer and the semiconductor substrate. Herein, the barrier liner includes Si 3 N 4  and has a thickness of 10-50 nm. 
     Preferably, the semiconductor device further comprises: a barrier layer formed between the first inter-layer dielectric layer and the second inter-layer dielectric layer. Herein, the barrier layer includes Si 3 N 4  and has a thickness of 10-50 nm. 
     Preferably, the thickness of the first inter-layer dielectric layer is 15-50 nm, and the thickness of the second inter-layer dielectric layer is 25-90 nm. 
     In accordance with the present invention, the second source/drain contact plug and the gate contact plug have the same etching depth. Thus, it is possible to effectively reduce the possibilities of shorts occurring between the contact plug and the gate. Moreover, since the etching width/height ratio of the source/drain contact plug and that of the gate contact plug are close to each other, the requirements on etching and the contact plug filling processes are relaxed. At the same time, the possibility of the occurrence of process defects is also reduced. Additionally, the present invention involves the replacement gate process which is compatible with the typical replacement gate procedures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will be clearer from the following detailed description about the non-limited embodiments of the present invention taken in conjunction with the accompanied drawings, in which: 
         FIG. 1  is a schematic diagram of a semiconductor device manufactured according to the conventional process; and 
         FIGS. 2-14  are schematic diagrams showing the respective steps of the semiconductor device manufacturing method proposed by the present invention, in which  FIG. 14  illustrates a semiconductor device manufactured according to the semiconductor device manufacturing method proposed by the present invention. 
     
    
    
     It is noted that the drawings of the present invention are not to scale but only for the purpose of illustrations. Therefore, the drawings should not be construed as any limitations or restrictions on the scope of the present invention. In the drawings, like constituting components are represented by like reference numbers. 
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Hereunder, the present invention will be described in accordance with the drawings. In the following description, while it may blur the understanding of the present invention, the conventional structure or construction will be omitted. 
     First of all, by referring to  FIG. 14 , the semiconductor device manufactured by the inventive process will be described in details.  FIG. 14  is a schematic diagram showing a semiconductor device manufactured according to the semiconductor device manufacturing method proposed by the present invention. 
     As shown in  FIG. 14 , the semiconductor device manufactured by the inventive process mainly comprises: a Si substrate  200 , a first Inter-Layer Dielectric (ILD) layer  280  (having a thickness of 15-50 nm), a second Inter-Layer Dielectric (ILD) layer  380  (having a thickness of 25-90 nm), silicide regions  210 , a metal gate  220 , a first source/drain contact plugs  240  (having a width of 15-100 nm), a second source/drain contact plugs  340  (having a width of 20-150 nm), and a gate contact plug  330  (having a width of 20-150 nm). The metal gate  220  is formed on a high-k dielectric layer  270  (having a thickness of 1-3 nm) which is deposited on the Si substrate  200 . A SiN spacer  260  (having a width of 10-40 nm) is formed to surround the high-k dielectric layer  270  and the metal gate  220 . The first inter-layer dielectric layer  280  is deposited on the Si substrate  200 . The second inter-layer dielectric layer  380  is deposited on the first inter-layer dielectric layer  280 . The silicide regions  210  is formed on and embedded in the Si substrate  200 . The first source/drain contact plugs  240  are formed in the first inter-layer dielectric layer  280  and are in contact with the silicide regions  210  respectively. The second source/drain contact plugs  340  and the gate contact plug  330  are formed in the second inter-layer dielectric layer  380 , in which the second source/drain contact plugs  340  are in contact with the first source/drain contact plugs  240  respectively and the gate contact plug  330  is in contact with the metal gate  220 . Each of the first source/drain contact plugs  240  includes a liner  225  (having a thickness of 2-15 nm) and conductive metal filled therein, and each of the second source/drain contact plugs  340  and the gate contact plug  330  includes a liner  325  (having a thickness of 2-15 nm) and conductive metal filled therein. 
     In accordance with the present invention, the second source/drain contact plugs  340  and the gate contact plug  330  have the same etching depth. Thus, it is possible to effectively reduce the possibilities of shorts occurring between the contact plugs and the gate. Moreover, since the etching width/height ratios are close to each other, the requirements on etching and the contact filling processes are relaxed. At the same time, the possibility of the occurrence of process defects is also reduced. Additionally, the present invention involves the replacement gate process which is compatible with the typical replacement gate procedures. 
     Next, by referring to  FIGS. 2-14 , the respective steps of the semiconductor device manufacturing method proposed by the present invention will be described in details. 
     Firstly, as shown in  FIG. 2 , silicide regions  210  and a sacrificed gate structure (a high-k dielectric layer  270 , a polysilicon gate  320 , a SiN spacer  260  and SiN cap layer surrounding and covering the high-k dielectric layer  270  and the polysilicon gate  320 ) are formed on a Si substrate  200 . As an example of the present invention, the high-k dielectric layer  270  has a thickness of 1-3 nm, the polysilicon gate  320  has a thickness of 20-70 nm, the SiN spacer  260  has a width of 10-40 nm in a horizontal direction of the drawing, and the SiN cap layer has a thickness of 15-40 nm. This step is also a part of the conventional process, but herein the polysilicon gate  320  is formed to be a sacrificed gate to be replaced a metal gate. 
     After the structure as shown in  FIG. 2  is formed and before the step shown in  FIG. 3  is performed, a barrier liner (e.g., consisting of Si 3 N 4 ) (not shown) can be entirely formed on the structure as shown in  FIG. 2 , wherein the barrier liner has a width of 10-50 nm. 
     Then, as shown in  FIG. 3 , a first inter-layer dielectric layer  280  is deposited on the Si substrate  200  with the silicide regions  210  and the sacrificed gate structure formed thereon. For example, undoped silicon oxide (SiO 2 ), doped silicon oxide (e.g., Boro-Silicate Glass (BSG) and Boro-Phospho-Silicate Glass (BPSG)) and silicon nitride (Si 3 N 4 ) and the like can be used as the material of the first inter-layer dielectric layer  280 . 
     Next, as shown in  FIG. 4 , the Chemical Mechanical Planarization (CMP) process is performed on the first inter-layer dielectric layer  280  to expose the SiN cap layer of the sacrificed gate structure. 
     Then, as shown in  FIG. 5 , the SiN cap layer is removed by performing another CMP process or a Reactive Ion Etching (RIE) process for SiN to expose the polysilicon gate  320  of the sacrificed gate structure. 
     Thereafter, as shown in  FIG. 6 , the entire polysilicon gate  320  is completely removed by dry etching or wet etching to form an opening. 
     Next, as shown in  FIG. 7 , depositing metal gate material into the opening to form a metal gate  220  is deposited and formed by means of the typical replacement gate process. After this step, the polysilicon gate  320  as the sacrificed gate is completely substituted by the metal gate  220 . 
     Then, as shown in  FIGS. 8 and 9 , by using lithography, a photoresist mask is formed ( FIG. 8 ), and contact openings are formed at predetermined position in the first inter-layer dielectric layer  280  by etching and photoresist removal processes so that at the bottoms of the contact openings, the silicide regions  210  on the Si substrate  200  are exposed ( FIG. 9 ). In a case where the barrier liner (not shown) is included, it is necessary to etch through the barrier liners on the silicide regions  210  at the bottoms of the contact openings so that the silicide regions  210  are exposed. 
     Thereafter, as shown in  FIG. 10 , metal plugs are deposited and formed in the contact openings so that first source/drain contact plugs  240  are formed and in contact with the respective silicide regions  210  thereunder. In this step, liners  225  (for example, TiN, TaN, Ta or Ti, and typically, having a width of approximate 2 nm-approximate 15 nm) are firstly deposited; conductive metal (for example, Ti, Al, TiAl, Cu, W) are secondly deposited; and finally, the CMP process for metal is performed. The forming process of the first source/drain contact plugs  240  is same with or similar to the conventional process. In the present invention, the first source/drain contact plugs  240  have a width (in a horizontal direction of the drawing) of 15-100 nm. 
     After the structure as shown in  FIG. 10  is formed and before the step shown in  FIG. 11  is performed, a barrier layer (e.g., consisting of Si 3 N 4 ) (not shown) can be entirely formed on the structure as shown in  FIG. 10 , wherein the barrier layer has a width of 10-50 nm. 
     Next, as shown in  FIG. 11 , a second inter-layer dielectric layer  380  is deposited on the first inter-layer dielectric layer  280  with the first source/drain contact plugs  240  and the metal gate  220  formed therein. For example, undoped silicon oxide (SiO 2 ), doped silicon oxide (e.g., Boro-Silicate Glass (BSG) and Boro-Phospho-Silicate Glass (BPSG)) and silicon nitride (Si 3 N 4 ) and the like can be used as the material of the second inter-layer dielectric layer  380 . Because of the previous CMP process ( FIG. 10 ), the second inter-layer dielectric layer  380  has a planar upper surface. 
     Then, as shown in  FIGS. 12 and 13 , by using lithography, a photoresist mask is formed ( FIG. 12 ), and contact openings are formed at predetermined position in the second inter-layer dielectric layer  380  by etching and photoresist removal processes so that at the bottoms of the contact openings, the first source/drain contact plugs  240  and the metal gate  220  in the first inter-layer dielectric layer  280  are exposed ( FIG. 13 ). In a case where the barrier layer (not shown) is included, it is necessary to etch through the barrier layers on the first source/drain contact plugs  240  and the metal gate  220  at the bottoms of the contact openings so that the first source/drain contact plugs  240  and the metal gate  220  are exposed. 
     Finally, as shown in  FIG. 14 , metal plugs are deposited and formed in the contact openings so that second source/drain contact plugs  340  and a gate contact plug  330  are formed, in which the second source/drain contact plugs  340  are in contact with the respective first source/drain contact plugs  240  thereunder, and the gate contact plug  330  is in contact with the metal gate  220 . In this step, liners  325  (for example, TiN, TaN, Ta or Ti, and typically, having a width of approximate 2 nm-approximate 15 nm) are firstly deposited; conductive metal (for example, Ti, Al, TiAl, Cu, W) are secondly deposited; and finally, the CMP process for metal is performed. The forming process of the second source/drain contact plugs  340  and the gate contact plug  330  is same with or similar to the conventional process. In the present invention, the second source/drain contact plugs  340  have a width (in a horizontal direction of the drawing) of 20-150 nm, and the gate contact plug  330  has a width (in a horizontal direction of the drawing) of 20-150 nm. 
     Additionally, in the present invention, the conductive metals can be selected so that the conductive metal in the second source/drain contact plugs  340  and the gate contact plug  330  has a resistivity smaller than that of the conductive metal in the first source/drain contact plugs  240 . For example, Cu can be selected as the conductive metal in the second source/drain contact plugs  340  and the gate contact plug  330 , and Al can be selected as the conductive metal in the first source/drain contact plugs  240 . Or, Al can be selected as the conductive metal in the second source/drain contact plugs  340  and the gate contact plug  330 , and Ti can be selected as the conductive metal in the first source/drain contact plugs  240 . 
     As such, the semiconductor device according to the present invention can be obtained. As aforementioned, the second source/drain contact plugs  340  and the gate contact plug  330  have the same etching depth. Thus, it is possible to effectively reduce the possibilities of shorts occurring between the contact plugs and the gate. Moreover, since the etching width/height ratios are close to each other, the requirements on etching and the contact filling processes are relaxed. At the same time, the possibility of the occurrence of process defects is also reduced. 
     Additionally, in the present invention, the first source/drain contact plugs  240  and the gate structure have the same height. Such a configuration makes the process of forming the first source/drain contact plugs  240  much easier. In this case, the lithography is completely performed on a planar surface. Moreover, such a configuration makes the present invention compatible with the standard replacement gate process. 
     The foregoing description gives only the preferred embodiments of the present invention and is not intended to limit the present invention in any way. Thus, any modification, substitution, improvement or like made within the spirit and principle of the present invention should be encompassed by the scope of the present invention.

Technology Classification (CPC): 7