Abstract:
Forming salicide in a semiconductor device includes the steps of: forming a first and a second gate oxide film and in a non-salicide region and a salicide region, the first gate oxide film being thicker than the second gate oxide film; forming a conductive layer and a nitride based hard mask layer, and then selectively removing the conductive layer, the hard mask layer, the first gate oxide film, and the second gate oxide film, thereby forming gate electrodes and simultaneously exposing an active region of the salicide region; forming a spacer oxide film on an upper surface, except for the hard mask layer, of a second resultant structure; selectively removing the spacer oxide film, thereby forming a spacer and simultaneously exposing the active region of the salicide region; removing the hard mask layer; and forming a salicide film on the upper surfaces of the gate electrodes and on the surface of the active region in the salicide region. Therefore, a non-salicide region and a salicide region can be formed selectively and simultaneously in a one-chip semiconductor device, so that the number of steps for a salicide forming process can be reduced.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a method for forming salicide in a semiconductor device, and more particularly to a method for forming salicide in a semiconductor device, which can selectively and simultaneously form salicide region (or Co-salicide region) and a non-salicide region (or non-Co-salicide in a one-chip semiconductor device.  
         [0003]     2. Description of the Prior Art  
         [0004]     The conventional method for forming salicide in a semiconductor device will be described as follows with reference to  FIGS. 1A through 1E .  
         [0005]      FIGS. 1A through 1E  are cross-sectional views showing a conventional process of forming salicide in a semiconductor device.  
         [0006]     According to a conventional salicide forming method of a semiconductor device, as shown in  FIG. 1A , a gate oxide film  13  and a gate electrode  15  are sequentially formed on a silicon substrate  11  including a non-salicide region and a salicide region. Then, an LDD spacer  17  is formed on one side of the gate oxide film  13  and the gate electrode  15 .  
         [0007]     Next, as shown in  FIG. 1B , an oxide film  19  is deposited on the upper surface of the resultant structure obtained through the above process, and then a photosensitive material layer  21  or a bottom anti-reflective coating (BARC) is formed in the non-salicide region A of the substrate. The oxide film  19  serves later as a barrier oxide film which prevents the generation of salicide in the non-salicide region during a salicide generating process.  
         [0008]     Subsequently, as shown in  FIG. 1C , an etch-back process is performed to the photosensitive material layer  21 , and the photosensitive material layer  21  is removed. When the etch-back process of the photosensitive material layer  21  is performed, activated plasma, such as CHF 3 /CF 4 /O 2 /Ar, and the likes, is used. In addition, N 2  gas, CxFy gas, such as C 4 F 8 , C 2 F 6 , and C 5 F 8 , and the likes can be used. Also, while the etch-back process of the photosensitive material layer  21  is performed, an etching process progresses to the oxide film  19  located on the gate electrode  15  so that there is no residual oxide film on the gate electrode  15 .  
         [0009]     Next, as shown in  FIG. 1D , a photosensitive pattern  23  is formed on the non-salicide region A. Then, after the oxide film  19  located in the salicide region B of the substrate is selectively removed using the photosensitive pattern  23  as a mask, the photosensitive pattern  23  is removed. At this time, etching of a portion of the oxide film  19  is performed using activated plasma of CHF 3 /CF 4 /O 2 /Ar, etc. In addition, N 2  gas and CxFy gas, such as C 4 F 8 , C 2 F 6 , and C 5 F 8 , and the likes can be used.  
         [0010]     Subsequently, as shown in  FIG. 1E , salicide (or Co-salicide)  25  is formed on the exposed portion of the gate electrode  15  in the non-salicide region A, and on the exposed portions of the silicon substrate  11  and the gate electrode  15  in the salicide region B. At this time, in the non-salicide part, salicide (or Co-salicide) is not generated due to a residual oxide barrier.  
         [0011]     In accordance with the conventional method described above, -after an LDD structure is formed, an oxide film formed in the salicide region is removed by using a photosensitive pattern as a barrier. Subsequently, after the photosensitive pattern is removed, a salicide layer is formed, so that steps of the salicide forming process are increased.  
       SUMMARY OF THE INVENTION  
       [0012]     Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide a method for forming salicide in a semiconductor device, which can selectively and simultaneously form a salicide region (or Co-salicide region) and a non-salicide region (or non-Co-salicide region) in a one-chip semiconductor device, thereby enabling steps of the salicide forming process to be reduced.  
         [0013]     In order to accomplish this object, there is provided a method for forming salicide in a semiconductor device, the method comprising the steps of: (1) forming a first gate oxide film and a second gate oxide film in a non-salicide region and a salicide region of a silicon substrate, respectively, the first gate oxide film being thicker than the second gate oxide film; (2) forming a conductive layer and a nitride based hard mask layer on an upper surface of a first resultant structure obtained through step (1), and then selectively removing the conductive layer, the hard mask layer, the first gate oxide film, and the second gate oxide film, thereby forming gate electrodes respectively in the non-salicide region and the salicide region and simultaneously exposing an active region of the salicide region; (3) forming a spacer oxide film on an upper surface, except for the hard mask layer, of a second resultant structure obtained through steps (1) to (2); (4) selectively removing the spacer oxide film, thereby forming a spacer on one side of each of the gate electrodes and simultaneously exposing the active region of the salicide region; (5) removing the hard mask layer remaining on upper surfaces of the gate electrodes in the non-salicide region and the salicide region; and (6) forming a salicide film on the upper surfaces of the gate electrodes in the non-salicide region and the salicide region and on the surface of the active region in the salicide region.  
         [0014]     In accordance with another aspect of the present invention, there is provided a method for forming salicide in a semiconductor device, the method comprising the steps of: (1) forming a first gate oxide film and a second gate oxide film in a non-salicide region and a salicide region of a silicon substrate, respectively, the first gate oxide film being thicker than the second gate oxide film; (2) forming a conductive layer on an upper surface of a first resultant structure obtained through step (1), and then selectively removing the conductive layer, the first gate oxide film, and the second gate oxide film, thereby forming gate electrodes respectively in the non-salicide region and the salicide region and simultaneously exposing an active region of the salicide region; (3) forming an ONO thin film and a nitride film on an upper surface of a second resultant structure which has been obtained through steps (1) to (2) and includes the gate electrodes; (4) selectively removing the ONO thin film and the nitride film located in the salicide region; (5) removing the nitride film remaining in the salicide region and forming a spacer on one side of each of the gate electrodes; and (6) forming a salicide film on the upper surfaces of the gate electrodes in the non-salicide region and the salicide region and on the surface of the active region in the salicide region. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:  
         [0016]      FIGS. 1A through 1E  are cross-sectional views showing a conventional process of forming salicide in a semiconductor device;  
         [0017]      FIGS. 2A through 2G  are cross-sectional views showing a process of forming salicide in a semiconductor device according to one embodiment of the present invention; and  
         [0018]      FIGS. 3A through 3F  are cross-sectional views showing a process of forming salicide in, a semiconductor device according to another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings. In the following description and drawings, the same reference numerals are used to designate the same or similar components, and so repetition of the description on the same or similar components will be omitted.  
         [0020]      FIGS. 3A through 3F  are cross-sectional views showing a process of forming salicide in a semiconductor device according to one embodiment of the present invention.  
         [0021]     According to a method for forming salicide in a semiconductor device of the present invention, as shown in  FIG. 3A , first, a dual gate oxide film including a thick gate oxide film  53   a  and a thin gate oxide film  53   b  is formed on the surface of a silicon substrate  51 . The surface of the silicon substrate  51  is divided into a non-salicide region A and a salicide region B. At this time, the thick gate oxide film  53   a  is formed on the non-salicide region A and the thin gate oxide film  53   b  is formed on the salicide region B.  
         [0022]     Next, a polysilicon layer  55  for gate formation and a nitride based hard mask layer  57  are deposited on the dual gate oxide film, and then a first photosensitive pattern  59  for patterning the polysilicon layer  35  is formed thereon. The first photosensitive pattern  59  is formed on each of the non-salicide region A and the salicide region B.  
         [0023]     Subsequently, as shown in  FIG. 3B , the polysilicon layer  55  and the hard mask layer  57  are selectively removed using the first photosensitive pattern  59  as a mask, so as to form gate electrodes  55   a,    55   b.  When the nitride based hard mask layer  57  is primarily etched, activated plasma, such as CHF 3 /CF 4 /O 2 /Ar, or C 4 F 8 /O 2 /Ar, is used. In addition, N 2  gas, CxFy gas, such as C 4 F 8 , C 2 F 6 , and C 5 F 8 , and the likes can be used. Here, flow rates of etching gases are as follows; CHF 3 : 1˜200 sccm, CF 4 : 1˜200 sccm, O 2 : 0˜20 sccm, and Ar: 1˜1000 sccm. Besides these, C 4 F 8  of 1˜50 sccm and N 2  of 0˜500 scorn may be used as etching gases.  
         [0024]     Secondarily, when the polysilicon layer  55  is etched to form the gate electrodes  55   a,    55   b,  activated plasma, such as Cl 2 /HBr/He—O 2 /Ar and the likes, is used.  
         [0025]     When the etching processes to form the gate electrodes  55   a,    55   b  are performed as described above, a gate electrode pattern  57   b  is formed on the thin gate oxide film  55   b  of the salicide region B, and the thin gate oxide film  53   b  of an active region is etched to expose the surface of the silicon substrate  51 . In contrast, a part of the thick gate oxide film  53   a  in the non-salicide region A remains even after the gate electrode pattern has been formed. This is because the etching selectivity of the polysilicon layer to the oxide film is about 200˜300 to 1.  
         [0026]     Next, the first photosensitive pattern  59  is removed, and then an oxidation process is performed on the surface of a resultant structure obtained through the above process to form an oxide film  61  thereon. Herein, the oxide film  61  is formed to protect a thick gate oxide film  53   a  remaining in an active region of the non-salicide region A, when the etching of an LDD oxide film (e.g., shown in  FIG. 3C , element  63 ) is performed in a following process as this will be described below. The oxide film  61  is not formed on the nitride based hard mask layer  57   a  or  57   b  located respectively on the gate electrodes  55   a,    55   b.  The oxide film  61  is not formed on the nitride layer  57   a  or  57   b,  but is formed on the sidewalls of the gate electrodes  55   a,    55   b  and the exposed area of the silicon substrate  31  in the salicide region B as this is fully shown in  FIG. 3B .  
         [0027]     Subsequently, as shown in  FIG. 3C , an LDD oxide film  63  is deposited on the resultant structure obtained through the above process.  
         [0028]     Next, as shown in  FIG. 3D , blanking etching of the LDD oxide film  63  is performed to form a spacer  63   a  on each side of each of the gate electrodes  55   a,    55   b.  When the LDD oxide film  63  is etched, activated plasma, such as CHF 3 /CF 4 /O 2 /Ar, or C 4 F 8 /O 2 /—Ar, is used. In addition, N 2 , O 2 , and CxFy such as C 4 F 8 , C 2 F 6 , C 5 F 8 , and the likes can be used. That is, an etching of the LDD oxide film  43  can be performed using activated plasma of CHF 3 /CF 4 /O 2 /Ar. In addition, N 2  gas and CxFy gas such as C 4 F 8 , C 2 F 6 , C 5 F 8  can be used. Here, each flow rate of the etching gases is as follows; CHF 3 : 1˜200 sccm, CF 4 : 1˜200 sccm, O 2 : 0˜20 sccm, and Ar: 1˜1000 sccm. Besides these, C 4 F 8  of 1˜50 sccm and N 2  of 0˜500 sccm may be used as etching gases.  
         [0029]     When an etching step is performed as described above, the surface of an active region in the salicide region B of the silicon substrate is exposed. In contrast, on the surface of an active region in the non-salicide region A of the silicon substrate, a remaining oxide film continuously remains.  
         [0030]     Subsequently, as shown in  FIG. 3E , a hard mask layer pattern  57   a  or  57   b  remaining on the upper surfaces of either one of the gate electrodes  55   a,    55   b  is etched by a down flow method using an O2/CF4 gas. When etching is performed by such a down flow method, the etching selectivity of the nitride film to the oxide film becomes about 12:1. Therefore, since oxide film is nearly not removed, the oxide film located on the active region of the non-salicide region A remains, and -the upper surfaces of the gate electrodes and the silicon substrate, on which a nitride film has existed, are exposed.  
         [0031]     Next, as shown in  FIG. 3F , salicide films  65  are formed on the exposed upper surfaces of the gate electrodes  55   a,    55   b  and also formed on the exposed surfaces of the active region of the salicide region B as shown with the same reference numeral  65  in  FIG. 3F .  
         [0032]     Meanwhile, a method for forming salicide in a semiconductor device according to another embodiment of the present invention will be described as follows with reference to  FIGS. 2A-2G .  
         [0033]      FIGS. 2A-2G  are, cross-sectional views showing a process of forming salicide in a semiconductor device according to another embodiment of the present invention.  
         [0034]     According to a method for forming form salicide in a semiconductor device of the present invention, as shown in  FIG. 2A , first, a dual gate oxide film including a thick gate oxide film  33   a  and a thin gate oxide film  33   b  is formed on the surface of a silicon substrate  31 . Herein, the surface of the silicon substrate  31  is divided into a non-salicide region A and a salicide region B. At this time, the thick gate oxide film  33   a  is formed on the non-salicide region A and the thin gate oxide film  33   b  is formed on the salicide region B.  
         [0035]     Next, a polysilicon layer  35  for gate formation is deposited on the dual gate oxide film, and then a first photosensitive pattern  37  for patterning the polysilicon layer  35  is formed thereon. The first photosensitive pattern  37  is formed in each of the non-salicide region A and the salicide region B.  
         [0036]     Subsequently, as shown in  FIG. 2B , the polysilicon layer  35  is selectively removed using the first photosensitive pattern  37  (as shown in  FIG. 2A ) as a mask, so as to form gate electrodes  35   a,    35   b.    
         [0037]     Next, after the first photosensitive pattern  37  is removed, an ONO thin film  39  and a nitride film  41  are stacked on the upper surface of a resultant structure, which has been obtained through the above process and includes the gate electrodes  35   a,    35   b.  Thereafter, a second photosensitive pattern  43  is formed only on the non-salicide region A.  
         [0038]     Subsequently, as shown in  FIG. 2C , the nitride film  41  and the ONO thin film  39 , which are located in the salicide region B, are removed by using the second photosensitive pattern  43  as a mask. When the nitride film  41  and the ONO thin film  39  are etched, activated plasma, such as CHF 3 /CF 4 /O 2 /Ar or so forth, is used. In addition, N 2  gas and CxFy gas such as C 4 F 8 , C 2 F 6 , C 5 F 8 , and the likes can be used. Here, each flow rate of the etching gases is as follows; CHF 3 : 1˜200 sccm, CF 4 : 1˜200 sccm, O 2 : 0˜20 sccm, and Ar: 1˜1000 sccm. Besides these, C 4 F 8  of 1˜50 sccm and N 2  of 0˜500 sccm may be used as etching gases.  
         [0039]     Next, the second photosensitive pattern  43  is removed by means of either O 2  plasma or an O 2  down flow method.  
         [0040]     Subsequently, as shown in  FIG. 2D , a blanket etching is performed by a down flow method, so as to selectively remove the remaining nitride film  41  and ONO thin film  39 . At this time, the etching of the nitride film is performed by a down flow method using O 2 /CF 4  gas. When etching is performed by a down flow method as described above, the etching selectivity of the nitride film to the oxide film becomes about 12:1. Therefore, since oxide film is nearly not removed, ‘ON’ portion of the ONO thin film  39  is removed, and only ‘O (Oxide)’ portion thereof remains.  
         [0041]     Next, as shown in  FIG. 2E , an oxide film  45  for forming an LDD structure is deposited on the upper surface of a resultant structure obtained through the above process.  
         [0042]     Subsequently, as shown in  FIG. 2F , the oxide film  45  is dry-etched to form a spacer  45   a  on one side of each of the gate electrodes  35   a  and  35   b.  The oxide film  45  is etched by utilizing activated plasma, such as CHF 3 /CF 4 /O 2 /Ar, or C 4 F 8 /O 2 /Ar, or so forth. In addition, N 2 , O 2 , and CxFy such as C 4 FB, C 2 F 6 , C 5 F 8 , and the likes can be used. That is, etching of the oxide film  45  can be performed using activated plasma of CHF 3 /CF 4 /O 2 /Ar. Herein, N 2  gas and CxFy gas, such as C 4 F 8 , C 2 F 6 , C 5 F 8 , can be used. Here, each flow rate of the etching gases is as follows; CHF 3 : 1˜200 sccm, CF 4 : 1˜200 sccm, O 2 : 0˜20 sccm, and Ar: 1˜1000 sccm. Besides these, C 4 F 8  of 1˜50 sccm and N 2  of 0˜500 sccm may be used as etching gases.  
         [0043]     When such an etching process is performed, the oxide layer continuously remains in the active region of the non-salicide region A, without leaving the oxide layer on both surface of the active region of the salicide region B and upper surfaces of the gate electrodes.  
         [0044]     Next, as shown in  FIG. 2G , salicide films  47  are formed on the exposed upper surfaces of the gate electrodes  35   a  and  35   b  and the exposed surfaces of the active region of the salicide region B.  
         [0045]     According to the method for forming salicide in the semiconductor device of the present invention, it is not required to perform an etch back process for the photosensitive film (or BARC), so contamination caused by particles can be reduced during the salicide forming process.  
         [0046]     Also, according to the method of the present invention, different from the conventional method, the LDD spacer can be separately formed in the non-salicide region (or Co-salicide region) and the salicide region.  
         [0047]     Also, salicide can be selectively formed in the non-salicide region and the salicide region.  
         [0048]     Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.