Patent Publication Number: US-7915113-B2

Title: Semiconductor device and method for manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Korean patent application number 10-2007-0104702, filed on Oct. 17, 2007 which is incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a method for manufacturing a semiconductor device including a vertical cell transistor structure, and more specifically, to a method for manufacturing a semiconductor device including forming a self-aligned storage node contact without a mask process. 
     Due to increase of integration of semiconductor devices, a planar area occupied by electron elements included in a semiconductor device has been shrunken. In the case of planar transistors, a channel width of the transistor is reduced to increase the integration of the semiconductor device. Since the channel width is proportional to a drain current, if the channel width is reduced, current transmission capacity of the transistor is degraded. As a result, the planar transistor does not both improve the transistor characteristics and increase of the integration in the transistor. 
     In order to overcome the limits of the planar transistor, a vertical transistor has been suggested. The vertical transistor includes a vertical gate formed at a side surface of a polysilicon pillar, a source formed in the bottom of the pillar and a drain formed in the top of the pillar. 
     A channel length of the vertical transistor is not limited by a current exposer and exposing method. The vertical transistor has a shorter channel length than that of the planar transistor because the channel length can be adjusted by regulation of the height of the pillar. Also, the vertical gate is formed at the side surface of the pillar so that the vertical transistor may have a broader channel width than that of the planar transistor. As a result, the vertical transistor has a faster switching ability and a greater power driving ability. 
     However, when a vertical cell transistor is used in a cell region, bit line contacts such as a bit line contact for connecting a bit line having an active area to a core region, a word line contact of the vertical cell transistor, a gate contact of the transistor formed in a peripheral circuit region and a junction region contact of the transistor formed in the peripheral circuit region have various depths, so that the bit line contacts are not formed by one contact process simultaneously. 
     The bit line contacts for connecting a bit line located in the bottom of the cell region as an active area type to a core region can be formed by several exposure and etching processes. As a result, the process for manufacturing a semiconductor device using the vertical cell transistor is complicated to degrade yield and increase manufacturing cost. 
     SUMMARY OF THE INVENTION 
     Various embodiments of the present invention are directed at providing a method for manufacturing a semiconductor device that comprises forming a self-aligned storage node contact without a mask process. 
     According to an embodiment of the present invention, a method for manufacturing a semiconductor device may include forming a vertical cell transistor structure over a semiconductor substrate of a cell region; forming an insulating film over the vertical cell transistor structure; planarizing the insulating film to expose a hard mask film disposed at a top portion of the vertical cell transistor structure; and forming a storage node contact by removing the hard mask film. Planarizing-the-insulating-film may be performed by a chemical mechanical polishing process. Removing-the-hard-mask-film may be performed by a dry or wet etching process. The method may further includes forming a storage node contact plug that fills the storage node contact. 
     According to an embodiment of the present invention, a method for manufacturing a semiconductor device may include preparing a semiconductor substrate including a cell region, a core/peripheral circuit region; forming a recess in the semiconductor substrate of the core/peripheral circuit region; forming a vertical cell transistor structure over the semiconductor substrate of the cell region and a gate over the recessed semiconductor substrate of the core/peripheral circuit region; forming an insulating film over the vertical cell transistor structure and the gate; planarizing the insulating film to expose a hard mask film disposed at a top portion of the vertical cell transistor structure; and forming a storage node contact by removing the hard mask film. 
     Recessing-the-semiconductor-substrate may be performed by a dry or wet etching process. The recess may be etched so that a top surface of the gate is formed to be lower than a top surface of the vertical cell transistor structure. The recess may have a depth ranging from 100 to 5000 Å. The method may further include forming a device isolating film in the recessed core/peripheral circuit region. Planarizing-the-insulating-film may be performed by a chemical mechanical polishing process. Removing-the-hard-mask-film may be performed by a dry or wet etching process. The method may further include forming a storage node contact plug that fills the storage node contact. 
     According to an embodiment of the present invention, a semiconductor device may include a vertical cell transistor structure formed in a cell region; a gate formed to be lower than a top portion of the vertical cell transistor structure in a core region and a peripheral circuit region; and an insulating film including a storage node contact that exposes a storage node junction region of the vertical cell transistor structure. The storage node junction region and the storage node contact may be self-aligned. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1   a  and  1   b  are cross-sectional diagrams illustrating a method for forming a storage node contact in a general vertical cell transistor structure. 
         FIGS. 2   a  to  2   d  are cross-sectional diagrams illustrating a method for forming a storage node contact in a vertical cell transistor structure according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENT 
       FIGS. 1   a  and  1   b  are cross-sectional diagrams illustrating a method for forming a storage node contact in a general vertical cell transistor structure. Referring to  FIGS. 1   a  and  1   b , a semiconductor device includes a cell region C and a core/peripheral region P. A vertical cell transistor structure is formed in the cell region C, and a planar gate electrode G is formed in the peripheral circuit region P. 
     The vertical cell transistor structure formed in the cell region C includes a bit line  12  having a junction region in a semiconductor substrate  10 , a bit line isolating layer  13  having an oxide film, a surrounding gate electrode  14 , a metal gate electrode  15  and a storage node junction region  16 . 
     After a transistor including a pillar pattern of the cell region C, the bit line  12 , the bit line isolating layer  13 , the surrounding gate electrode  14  and the metal gate electrode  15  is formed, the gate electrode G of the core/peripheral circuit region P is formed. An insulating material  24  is deposited, and an etching process is performed with a storage node contact mask to form a storage node contact  22  in the cell region C. 
     In a process for forming a DRAM having the vertical cell transistor structure, a storage node contact is required to be overlapped with a pillar pattern having a narrow bottom portion. When the contact is formed to be small in order to increase an overlap margin, it is difficult to perform a patterning process and an overlay control. 
       FIGS. 2   a  to  2   d  are cross-sectional diagrams illustrating a method for forming a storage node contact in a vertical cell transistor structure according to an embodiment of the present invention. As shown in  FIG. 2   a , a semiconductor substrate  110  includes a cell region C and a core/peripheral circuit region P. A dry or wet etching process is performed on the core/peripheral circuit region P of the semiconductor substrate  110  to form a recess. 
     A depth of the recess is etched to have a thickness ranging from 100 Å to 5000 Å, so that a top surface of a gate height to be formed in the core/peripheral circuit region P may be lower than a top surface of a vertical cell transistor structure to be formed in the cell region C. 
     Referring to  FIG. 2   b , a device isolating film  120  is formed in the recessed semiconductor substrate  110 . 
     Referring to  FIG. 2   c , a vertical cell transistor structure is formed in the cell region C, and a gate G is formed in the core/peripheral circuit region P. 
     The vertical cell transistor structure includes a bit line  112  formed as a junction region in the semiconductor substrate  110 , a bit line isolating layer  113  having an oxide film, a surrounding gate electrode  114 , a metal gate electrode  115  and a storage node junction region  116  and a hard mask film  118  formed on the storage node junction region  116 . 
     An insulating film  124  is deposited over the resulting structure including the vertical cell transistor structure and the gate G. The insulating film  124  is planarized to expose the hard mask film  118  of the vertical cell transistor structure. The planarizing process is performed by a chemical mechanical polishing process without a mask to obtain a self-aligned storage node contact. 
     Referring to  FIG. 2   d , a dry or wet etching process is performed to selectively remove the hard mask film  118  of the vertical cell transistor structure to form a self-aligned storage node contact  122 . 
     As described above, according to an embodiment of the present invention, a method for manufacturing a semiconductor device includes forming a self-aligned storage node contact in a vertical cell transistor structure without an additional mask process to facilitate and simplify the process. 
     The above embodiments of the present invention are illustrative and not limitative. Various alternatives and equivalents are possible. The invention is not limited by the lithography steps described herein. Nor is the invention limited to any specific type of semiconductor device. For example, the present invention may be implemented in a dynamic random access memory (DRAM) device or non volatile memory device. Other additions, subtractions, or modifications are obvious in view of the present disclosure and are intended to fall within the scope of the appended claims.