Abstract:
A method for fabricating a semiconductor device is disclosed. The method includes: forming a photoresist film on a semiconductor substrate including a silicide forming region and non-silicide forming region; forming a photoresist pattern as a non-salicide pattern by patterning the photoresist film, so as to cover the non-silicide forming region and open the silicide forming region, with an overhang structure that a bottom is removed more compared to a top; forming a metal film on a top of the photoresist pattern and overall the semiconductor substrate in the silicide forming region; stripping the photoresist pattern and the metal film on the photoresist pattern; and forming a silicide metal film by annealing the metal film remaining on the semiconductor substrate. Therefore, the present invention simplifies a salicide process of a semiconductor device, making it possible to improve yields.

Description:
[0001]    The present application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2007-0123570 (filed on Nov. 30, 2007), which is hereby incorporated by reference in its entirety. 
       BACKGROUND 
       [0002]    In order to promote a thin structure, large capacity and high integration of a semiconductor device, there is currently a demand for an indispensable subsequent process for forming a multilayer wire such as a metal wire which can electrically connect each device, after forming a transistor, a bit line, a capacitor of the semiconductor device. The performance of a transistor is closely related to the speed, drive current and leakage current of the transistor, and in order to maximize the performance of the transistor, the speed and driver current of the transistor must be large and the leakage current must be small. In order to increase the speed and drive current of the transistor while reducing the leakage current of the transistor, resistance of source and drain of the transistor, resistance values of resistance of gate and contact resistance of the transistor must be small. 
         [0003]    In order to reduce resistance values of resistance of source and drain of the transistor, resistance of gate, and contact resistance of the transistor, a self-aligned silicide (salicide) process for fabricating silicide on and/or over an interface of the drain and source and an interface of the gate is used. The salicide process is an important process in recent fabrication of a semiconductor device. Generally, silicide is advantageous in low resistance, high thermal stability, and easy application to a current silicon process, such that the silicide has been actively applied to a VLSI wire process. Furthermore, a silicide film formed on and/or over a gate electrode and a junction surface of source and drain can reduce the specific resistance of the gate electrode and contact resistance of the source and drain, respectively, thereby providing an advantage capable of greatly reducing wire resistance. As a material of the silicide, rare earth metals which react with silicon is generally used, for example, tungsten silicide (WSi 2 ), titanium silicide (TiSi 2 ), cobalt silicide (CoSi 2 ) and the like. A salicide barrier film is formed on and/or over a region where salicide is not formed, using an oxide film and the like. The salicide is formed in the process sequence of forming a salicide barrier film after forming a gate, forming a photoresist pattern using a photo process, forming a salicide barrier film pattern by removing an oxide film on and/or over a region where silicide is to be formed, removing the photoresist pattern, depositing a metal film, and forming a silicide using an annealing process. However, in such a salicide process, problems arise in that the process is complicated to extend the process time and to lower yields. 
       SUMMARY 
       [0004]    Embodiments relate to a method for fabricating a semiconductor device that can simplify a salicide process. 
         [0005]    In accordance with embodiments, a method for fabricating a semiconductor device may include at least one of the following: forming a photoresist film on and/or over a semiconductor substrate including a silicide forming region and non-silicide forming region; forming a photoresist pattern as a non-salicide pattern by patterning the photoresist film, so as to cover the non-silicide forming region and expose the silicide forming region, with an overhang structure that a bottom is removed more compared to a top; forming a metal film on and/or over the photoresist pattern and the semiconductor substrate in the silicide forming region; stripping the photoresist pattern and the metal film on the photoresist pattern; and forming a silicide metal film by annealing the metal film remaining on and/or over the semiconductor substrate. 
         [0006]    In accordance with embodiments, a method for fabricating a semiconductor device may include at least one of the following: providing a semiconductor substrate having a silicide forming region and a non-silicide forming region; and then forming a photoresist film over the silicide forming region and the non-silicide forming region; and then forming a photoresist pattern by patterning the photoresist film over the non-silicide forming region and exposing the silicide forming region, wherein a bottom portion of the photoresist pattern has an overhang structure; and then forming a metal film over the photoresist pattern and the semiconductor substrate in the silicide forming region; and then removing the photoresist pattern and the metal film formed over the photoresist pattern; and then forming a silicide metal film by performing an annealing process on the metal film formed over the semiconductor substrate. 
         [0007]    In accordance with embodiments, a method for fabricating a semiconductor device may include at least one of the following: providing a semiconductor substrate having a silicide forming region and a non-silicide forming region; and then forming gate patterns in the silicide forming region and the non-silicide forming region; and then forming spacers over sidewalls of the gate pattern; and then forming a photoresist pattern over the non-silicide forming region, wherein a bottom sidewall portion of the photoresist pattern is slanted at an angle with respect to an upper sidewall portion of the photoresist pattern; and then forming a metal film over the semiconductor substrate in the silicide forming region including the gate pattern and the spacers and also in the non-silicide forming region including the uppermost surface of the photoresist pattern and the upper sidewall portion of the photoresist pattern and not the bottom sidewall portion of the photoresist pattern; and then forming a pre-silicide film on the metal film in the silicide forming region by performing a first annealing process; and then removing the photoresist pattern including the metal film formed in the non-silicide forming region; and then forming a silicide metal film by performing a second annealing process on the pre-silicide film formed over the gate pattern and the semiconductor substrate in the silicide forming region. 
         [0008]    In accordance with embodiments, a method for fabricating a semiconductor device may include at least one of the following: providing a semiconductor substrate having a silicide forming region and a non-silicide forming region; and then forming a transistor in the silicide forming region and the non-silicide forming region; and then forming a photoresist pattern over the non-silicide forming region such that a bottom sidewall portion of the photoresist pattern is slanted at an angle with respect to an upper sidewall portion of the photoresist pattern; and then forming a metal film over the semiconductor substrate in the silicide forming region including the transistor and also in the non-silicide forming region including the entire photoresist pattern except the bottom sidewall portion; and then removing the photoresist pattern including the metal film formed in the non-silicide forming region; and then forming a silicide metal film over the transistor by performing an annealing process. 
     
    
     
       DRAWINGS 
         [0009]    Example  FIGS. 1 to 7  illustrate a method for fabricating a semiconductor device in accordance with embodiments. 
       
    
    
     DESCRIPTION 
       [0010]    Example  FIG. 1  is a flowchart explaining a method for fabricating a semiconductor device and example  FIGS. 2 to 7  are cross-sectional views showing processes of a method for fabricating a semiconductor device in accordance with embodiments. 
         [0011]    Referring to example  FIGS. 1 and 2 , in S 100 , a gate dielectric film  110  is formed on and/or over a semiconductor substrate  100  including a silicide forming region B and a non-silicide forming region A and a gate electrode  120  is formed on and/or over the gate dielectric film  110 . Spacers  130  are formed on and/or over side walls of the gate electrode  120  and the gate dielectric film  110  to protect the side walls of the gate electrode  120 . Source/drain regions may also be formed in the semiconductor substrate  100  at both sides of the gate electrode  120  by ion-implanting a high-concentration n-type or p-type impurity thereto. 
         [0012]    Thereafter, as shown in example  FIGS. 3 and 4 , in S 110 , a non-salicide (NSAL) pattern is formed on and/or over the entire semiconductor substrate  100  including the gate electrode  110  and spacers  130 . As shown in example  FIG. 3 , a photoresist film  150   a  is formed over the semiconductor substrate  100  including the gate electrode  110  and spacers  130 . The photoresist film  150   a  may be formed of a positive photoresist film or a negative photoresist film. 
         [0013]    Hereinafter, embodiments will be described based on the negative photoresist film, however, the same principle may also be applied to the positive photoresist film. The positive photoresist film has the property that a cross-link in an exposed portion is broken to be removed by development, and the negative photoresist film has the property that a cross-link in an exposed portion is firmly coupled not to be removed by developer. After a soft bake process is performed on the photoresist film  150   a,  the non-silicide forming region A is selectively exposed by the photoresist film  150   a  using a mask. In other words, the mask allows light to be transmitted to the non-silicide forming region A of the photoresist film  150   a  and not to be transmitted to the silicide forming region B of the photoresist film  150   a.  At this time, the exposure is performed using exposure energy greater than exposure energy generally used in a photo process. Thereafter, the surface of the photoresist film  150   a  in the exposed non-silicide forming region A is cured by performing a mono-chloro benzene (MCB) process so as not to react with the developer. The MCB process refers to a process to dip the semiconductor substrate in the MCB solution and the process time is in a range between approximately 5 to 10 minutes. If the photoresist film  150   a  processed as above is developed, a photoresist pattern  150  from which the photoresist film  150   a  in the non-exposed silicide forming region B is removed is formed as shown in example  FIG. 4 . 
         [0014]    Finally, as shown in example  FIG. 4 , the photoresist film  150   a  is removed from the silicide forming region B of the semiconductor substrate  100 , and the photoresist pattern  150  remains in the non-silicide forming region A. The remaining photoresist pattern  150  corresponds to a non-salicide (NSAL) pattern. Also, the photoresist pattern  150  has an overhang structure such that a bottom portion thereof is removed. Meaning, a critical dimension (CD) of the upper portion of the photoresist pattern  150  is larger than a CD of the bottom portion of the photoresist pattern  150 . The overhang structure is important insofar as the photoresist film  150   a  in the non-silicide forming region A is selectively exposed using exposure energy greater than exposure energy used in a general photo process and the MCB process is performed on and/or over the surface of the exposed photoresist film  150   a.  Therefore, the upper portion of the photoresist film  150   a  in the exposed non-silicide forming region A has the firmly coupled cross-link, whereas the bottom portion thereof does not have such a cross-link. 
         [0015]    Thereafter, as shown in example  FIGS. 1 and 5 , in S 120 , a metal film  160  is deposited on and/or over the semiconductor substrate  100  in the non-silicide forming region A and the silicide forming region B including the photoresist pattern  150  having the overhang structure. The metal film  160  may include at least one of cobalt (Co), titanium (Ti) and titanium nitride (TiN), and may form the metal film  160  as a multi-layer by forming a Ti film on and/or over the Co film and then forming a TiN film on and/or over the Ti film. The Co film, Ti film and TiN film may be formed at a thickness in a range between approximately 10 to 20 nm, respectively. The Ti film and TiN film has two roles. If an oxide film SiO 2  is formed on and/or over a surface of a silicon substrate  100 , silicide is not formed. Therefore, the Ti film serves to remove the oxide film formed on and/or over the surface of the silicon substrate  100  by reacting with the oxide of the oxide film formed on and/or over the surface of the silicon substrate  100 , and assist a silicide to be properly and uniformly formed by reacting the Co film with the silicon substrate  100 . Also, the Ti film functions as a capping layer which serves to prevent the oxidation of the surface of a region where silicide is to be formed when the silicon substrate  100  is exposed to air in order to perform an annealing process after depositing the multi-layered Co/Ti/TiN film. The deposition temperature of the metal film  160  may be in a range between approximately 100 to 200° C. 
         [0016]    The metal film  160  is formed on and/or over the photoresist pattern  150  and is also formed on and/or over the semiconductor substrate  100  in the silicide forming region B, for example, the uppermost surface of the source/drain regions, the spacer  130  and the gate electrode  120 . Since the photoresist pattern  150  is formed having an overhang structure, a portion of the metal film  160  is cut on a bottom side wall of the photoresist pattern  150  as shown in example  FIG. 5 . Meaning, the metal film  160  is not formed on and/or over the lower, angled portion of the photoresist pattern  150 . In S 130 , a first annealing process may then be performed on the semiconductor substrate  100  on which the metal film  160  is formed. The first annealing temperature is in a range between approximately 400 to 500° C., and a pre-silicide film, for example, CoSi, is thereby formed due to the first annealing process. 
         [0017]    Thereafter, as shown in example  FIGS. 1 and 6 , in S 140 , the photoresist pattern  150  is stripped. Since a portion of the metal film  160  is not formed on and/or over the bottom side wall of the photoresist pattern  150 , stripper material infiltrates into the gap so that the photoresist pattern  150  may be removed. Also, the portion of the metal film  160  formed on and/or over the photoresist pattern  150  may also be detached and removed. Thereby, the metal film  160  remains only on and/or over the semiconductor substrate  100  in the silicide forming region B, spacer  130  and gate electrode  120 . 
         [0018]    Thereafter, as shown in example  FIGS. 1 and 7 , in S 150 , a second annealing process is performed on the semiconductor substrate  100 . The second annealing temperature is more than 800° C. Then, except for the metal film  160  formed on and/or over the upper surface of the spacer  130 , the metal film  160  formed on and/or over the semiconductor substrate  100  and the gate electrode  120  undergoes a silicide reaction to be formed as a silicide metal film  160   a.  For example, the CoSi formed after the first annealing becomes CoSi 2  to be formed as a silicide film  160   a.  Thereafter, an etching process may be performed to remove the metal film  150   a  formed on and/or over the upper surface of the spacer  130 , not selectively salicided, as shown in example  FIG. 7 . Thereby, the silicide metal film  160   a  may be selectively formed on and/or over the uppermost surface of the gate electrode  120  and the source/drain region in the silicide forming region B of the semiconductor substrate  100 . Thereafter, a cleaning process is performed on the semiconductor substrate  100  to complete the salicide process. 
         [0019]    In accordance with embodiments, a method for fabricating a semiconductor device simplifies a salicide process of a semiconductor device, thereby making it possible to maximize yields. For example, the method for fabricating a semiconductor device in accordance with embodiments can simply form silicide using a photoresist pattern as a salicide barrier pattern, making it possible to shorten the process time. 
         [0020]    Although embodiments have been described herein, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.