Abstract:
A semiconductor device and a method for manufacturing the same that forms a self-aligned contact hole between two gate lines. A substrate is provided that has a first gate line formed thereon. An insulator is formed on the first gate line and substrate. Then a portion of the insulator and a portion of the first gate line is selectively removed to split the first gate line into a second gate line and a third gate line and to concurrently expose the substrate. Thus, producing a self-aligned contact hole between the second and third gate lines.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a semiconductor device and, more particularly, to a semiconductor device having a self-aligned contact hole and a method for manufacturing the same.  
           [0003]    2. Discussion of the Related Art  
           [0004]    A general process of forming a self-aligned contact hole, which can be easily and precisely made, does not require fitting a mask using a location-fitting margin. Accordingly, high integration can be achieved without utilizing a highly skilled process or highly precise equipment to perform the process.  
           [0005]    There are two conventional methods for forming a self-aligned contact hole. In one method, selective etch rates are used. In another method, which is a semi self-alignment method, a contact hole is formed and then an oxide sidewall is formed.  
           [0006]    A conventional method for manufacturing a semiconductor device will be explained with reference to the accompanying drawings.  
           [0007]    [0007]FIGS. 1 a  to  1   c  are cross-sectional views showing a method for manufacturing a semiconductor device according to one conventional method and FIGS. 2 a  to  2   c  are cross-sectional views showing a method for manufacturing a semiconductor device according to another conventional method. FIG. 3 is a cross-sectional view showing a structure of a semiconductor device manufactured according to a conventional method, which illustrates problems arising from manufacturing the semiconductor device according to a conventional method.  
           [0008]    Referring initially to FIG. 1 a , an active region and a field region are defined on a substrate  1  and then a field oxide layer is formed on the field region. Next, an oxide layer, a polysilicon layer, and a nitride layer are successively formed on the entire surface of the substrate  1 . Subsequently, a photoresist layer is coated on the resultant surface and then selectively patterned. With the patterned photoresist layer serving as a mask, the nitride layer, the polysilicon layer, and the oxide layer are successively etched to form a first and second gate structure  3   a  and  3   b , respectively. The first and second gate structures  3   a  and  3   b  comprise a gate oxide layer  2 , a gate electrode  3 , and a gate cap insulating layer  4 . Thereafter, the remaining patterned photoresist layer is removed.  
           [0009]    With the first and second gate structures  3   a  and  3   b  serving as a mask, lightly doped impurity ions are implanted into the exposed surface of the substrate  1  thereby forming lightly doped source and drain regions  5 . Next, a nitride layer is deposited over the substrate  1  and anisotropically etched to form sidewall spacers  6  on the sides of the first and second gate structures  3   a  and  3   b , respectively. With the first and second gate structures  3   a  and  3   b  and the sidewall spacers  6  serving as a mask, heavily doped impurity ions are implanted into the exposed surface of the substrate  1  thereby forming a heavily doped source/drain region  7 .  
           [0010]    Referring to FIG. 1 b , there is formed an interlayer insulating layer  8  over the substrate  1 . Then a photoresist layer is formed on the interlayer insulating layer  8  and exposed and developed to form the patterned photoresist layer  9 .  
           [0011]    Referring to FIG. 1 c , with the patterned photoresist layer  9  serving as a mask, the interlayer insulating layer  8  is anisotropically etched using a high selective etch rate of the oxide and nitride layers until the surface of the substrate  1  is exposed, thus forming a contact hole. The high selective etch rate is described as the nitride or oxide layer being easily etched and the polysilicon layer not being easily etched or vice-versa. Next, on the entire surface of the substrate  1 , there is formed a conductive material such as polysilicon, aluminum, or tungsten that are patterned to form a bit line  10 .  
           [0012]    Another conventional method for manufacturing a semiconductor device will be explained with reference to FIGS. 2 a - 2   c.    
           [0013]    Referring initially to FIG. 2 a , there are defined an active region and a field region in the substrate  11 . A field oxide layer is formed on the field region. Then, a first oxide layer, a polysilicon layer, and a second oxide layer are successively formed on the entire surface of the substrate  11 . Subsequently, a photoresist layer is coated on the resultant surface and then exposed and developed to form a patterned photoresist layer. With the patterned photoresist layer serving as a mask, the first oxide layer, the polysilicon layer, and the second oxide layer are successively etched to form a first and second gate structure  13   a  and  13   b , respectively. The first and second gate structures  3   a  and  3   b  comprise a gate oxide layer  12 , a gate electrode  13 , and a gate cap insulating layer  14  on a predetermined portion of the substrate  11 . Thereafter, the remaining patterned photoresist layer is removed.  
           [0014]    With the first and second gate structures  13   a  and  13   b  serving as a mask, lightly doped impurity ions are implanted into the exposed surface of the substrate  11  thereby forming lightly doped source and drain regions  15 . Next, an oxide layer is formed on the resultant surface and then anisotropically etched to form sidewall spacers  16  on sides of the first and second gate structures  13   a  and  13   b.  With the sidewall spacers  16  and first and second gate structures  13   a  and  13   b  serving as a mask, heavily doped impurity ions are implanted into the substrate  11  thereby forming a heavily doped source/drain region  17 .  
           [0015]    Referring to FIG. 2 b , on the resultant surface, there is deposited an interlayer insulating layer  18  using a chemical vapor deposition (CVD) method. Next, a photoresist layer is coated on the resultant surface and then exposed and developed to form a patterned photoresist layer  19 .  
           [0016]    Referring to FIG. 2 c , with the patterned photoresist layer  19  serving as a mask, the interlayer insulating layer  18  is anisotropically etched in between the first and second gate structures  13   a  and  13   b  to expose the surface of the source/drain region  17  thereby forming a contact hole. Then, an oxide layer is formed on the resultant surface and then anisotropically etched to form oxide sidewall spacers  20  on sides of the interlayer insulating layer  8 . Subsequently, a conductive material such as polysilicon, aluminum, or tungsten is formed on the entire surface and then patterned to form a bit line  21 . In this case, the oxide sidewall spacers  20  serve to insulate the gate electrode  13  from the bit line  21 .  
           [0017]    Problems arising from semiconductor devices manufactured according to the conventional methods will be explained with reference to FIG. 3.  
           [0018]    As shown in FIG. 3, when an alignment tolerance is beyond the limit of a photolithography process, formation of a contact hole is misaligned on a gate electrode  13 . Consequently, a short between the gate electrode  13  and the bit line  21  is generated even after the oxide sidewall spacers  20  are formed.  
           [0019]    Conventional methods for manufacturing a semiconductor device have the following problems.  
           [0020]    First, it is difficult to carry out an etch process over materials such as a nitride and an oxide having a high selective etch rate. If a selective etch rate is high, a polymer may be generated that blocks a contact hole and stops the etch process. Moreover, it is difficult to simplify the overall process.  
           [0021]    Second, for a high density device, alignment tolerance easily goes beyond the limit of a photolithography process that causes misalignment when forming a contact hole. Because of misalignment, a short between a gate electrode and a bit line is generated that destroys the operability of a unit device.  
         SUMMARY OF THE INVENTION  
         [0022]    Therefore, the present invention is directed to a semiconductor device and a method for manufacturing the same that substantially obviate one or more of problems due to limitations and disadvantages of the related art.  
           [0023]    An object of the present invention is to provide a semiconductor device having a self-aligned contact hole and a method for manufacturing the same.  
           [0024]    Another object of the present invention is to provide a semiconductor device having unsymmetrical source and drain regions and a method for manufacturing the same.  
           [0025]    To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, there is provided a semiconductor device having a self-aligned contact hole, the device comprising: a substrate; a first conductor structure and a second conductor structure formed on the substrate; an insulator structure formed on the first and second conductor structure and on the substrate except over the substrate in a region between the first and second conductor structures; and sidewall spacers formed on a side of the first and second conductor structures and on a side of the insulator structure, the sidewall spacers defining the self-aligned contact hole in the region between the first and second conductor structures.  
           [0026]    In another aspect of the invention, there is provided a method for self-aligning a contact hole between two conductor structures in a semiconductor device, the method comprising the steps of: providing a substrate; forming a first conductor structure on the substrate; forming an insulator structure on the first conductor structure and substrate; and selectively removing a portion of the insulator structure and a portion of the first conductor structure to split the first conductor structure into a second conductor structure and a third conductor structure and to concurrently expose the substrate thereby producing a self-aligned contact hole between the second and third conductor structures.  
           [0027]    In another aspect of the present invention, there is provided an unsymmetrical semiconductor device using a self-aligned contact hole, the device comprising: a substrate having impurity regions formed therein; a first conductor structure and a second conductor structure formed on the substrate; an insulator structure formed on the first and second conductor structures and on the substrate except over the substrate in a region between the first and second conductor structures; first sidewall spacers formed on a side of the first and second conductor structures and on a side of the insulator structure, the first sidewall spacers defining the self-aligned contact hole in the region between the first and second conductor structures; and second sidewall spacers formed on sides of the first and second conductor structures opposite of the self-aligned contact hole.  
           [0028]    In still another aspect of the present invention, there is provided a method for forming an unsymmetrical semiconductor device using a precisely aligned contact hole, the method comprising the steps of: providing a substrate; forming a first conductor structure on the substrate; forming a first impurity region in the semiconductor substrate at sides of the first conductor structure; forming an insulator structure on the first conductor structure and substrate; selectively removing a portion of the insulator structure and a portion of the first conductor structure to split the first conductor structure into a second and third conductor structure and to concurrently expose the substrate thereby producing a self-aligned contact hole between the second and third conductor structures; and forming a second impurity region in the self-aligned contact hole.  
           [0029]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0030]    The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein  
         [0031]    [0031]FIGS. 1 a  to  1   c  are cross-sectional views showing a conventional method for manufacturing a semiconductor device;  
         [0032]    [0032]FIGS. 2 a  to  2   c  are cross-sectional views showing another conventional method for manufacturing a semiconductor device;  
         [0033]    [0033]FIG. 3 is a cross-sectional view of a semiconductor device manufactured according to a conventional method.  
         [0034]    [0034]FIG. 4 is a plan view of a semiconductor device according to the present invention;  
         [0035]    [0035]FIG. 5 is a cross-sectional view across the line V-V in FIG. 4 according to the present invention; and  
         [0036]    [0036]FIGS. 6 a  to  6   d  are cross-sectional views showing a method for manufacturing a semiconductor device according to a preferred embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0037]    Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in FIGS. 4, 5, and  6   a - 6   b.    
         [0038]    Referring to FIGS. 4 and 5, the structure of the semiconductor device according to the present invention will first be described. In FIG. 4, the plan view of the semiconductor device according to the present invention illustrates a first source/drain region  35  and a second source/drain region  39 . A gate line, which had a width of X, is divided into a first gate line  43   a  and a second gate line  43   b  having a width of X′ and X″, respectively. The area  42  having an “X” drawn therethrough represents a contact plug area wherein a contact plug is in contact with a second source/drain region  39 . The contact plug is also in contact with the bit line  41 .  
         [0039]    In FIG. 5, the cross-sectional view of the semiconductor device taken along the line V-V of FIG. 4 illustrates a field region and an active region defined on a substrate  30  and a field oxide layer  31  formed on the field region. A gate line  43  (see FIG. 6 a ) having a width of X is formed over the active region of the substrate  30 . The gate line  43 , preferably, comprises a gate oxide layer  32  formed on the substrate  30 , a conductive line  33 , which is also a gate electrode, formed on the gate oxide layer  32 , and a gate cap insulator layer formed on the conductive line  33 . The gate line  43  is divided into two gate lines which are the first and second gate lines  33   a  and  33   b  having widths of X′ and X″, respectively, as shown in FIG. 5. The first gate line  43   a  comprises a gate oxide layer  32  formed on the substrate  30 , a conductive line  33   a  formed on the gate oxide layer  32 , and a gate cap insulator layer  34  formed on the conductive line  33   a.  The second gate line  43   b  has the same structure of the first gate line  43   a  having a conductive line  33   b  instead of a conductive line  33   a.    
         [0040]    A contact hole is formed between the first and second gate lines  43   a  and  43   b  and an interlayer insulating layer  37  is formed on the first and second gate lines  43   a  and  43   b  and on the substrate  30 .  
         [0041]    Source and drain regions  35  are formed in the substrate  30  at outer sides of the first and second gate lines  43   a  and  43   b.  A second source/drain region  39  is formed in the substrate  30  between the first and second gate lines  43   a  and  43   b.  While gate insulating sidewalls  36  are formed on the outer sides of the gate lines  43   a  and  43   b , oxide sidewall spacers  40  are formed on the inner sides of the gate lines  43   a  and  43   b  and the interlayer insulating layer  37 . A contact plug  41   a  is formed in contact with the second source/drain region  39 . Structures on the field oxide layer  31  serve as “dummy” structures which do not serve any functional purpose. The semiconductor devices according to the invention can have transistors in field regions as well as active regions, and are described in terms of structures in the field regions that correspond to the structures in the active regions. In particular, on the field oxide layers  31 , structures corresponding to the gate electrodes  33   a  and  33   b , the gate cap insulators  34 , the sidewall spacers  36  and  40  and the plug  41   a  are formed. But because they are formed on the field oxide layers  31 , they represent inoperative transistors. Forming these inoperative transistors in the field regions is not necessary to practice the invention. But it has been determined that forming the structures in the field regions as well as in the active regions has advantages, from an ease-of-manufacturing point of view. Thus, it is preferable but not necessary to form the inoperative transistors in the field regions at the same time that the corresponding transistors are formed in the active regions.  
         [0042]    A method for manufacturing a semiconductor device having the aforementioned structure of FIG. 5 according to the present invention will be explained with reference to FIGS. 6 a - 6   d.    
         [0043]    Referring initially to FIG. 6 a , a field region and an active region are defined in a substrate  30  and then a field oxide layer is formed on the field region. Next, a first thin oxide layer is formed on the entire surface of the substrate  30  using a thermal oxidation process, and then a polysilicon layer and a second oxide layer are successively formed on the first thin oxide layer. In this case, a nitride layer can be deposited in place of the second oxide layer.  
         [0044]    Subsequently, the first oxide layer, the polysilicon layer, and the second oxide layer are anisotropically etched to form a gate line  43  that comprises a gate oxide layer  32 , a conductive line  33 , and a gate cap insulating layer  34 , which has a width of X.  
         [0045]    Referring to FIG. 6 b,  with the gate line  43  serving as a mask, lightly doped impurity ions of either an N type or P types are implanted into the substrate  30  thereby forming first source and drain regions  35 . Next, either of an oxide layer or a nitride layer is formed and then anisotropically etched to form gate insulating sidewalls  36  on the sides of the gate line  43 .  
         [0046]    Referring to FIG. 6 c , an interlayer insulating layer  37  of an oxide is formed on the entire surface of the substrate  30  using a chemical vapor deposition (CVD) method, and then a photoresist layer is coated on the entire surface and patterned using a contact hole mask to form a patterned photoresist layer  38 .  
         [0047]    Subsequently, with the patterned photoresist layer  38  serving as a mask, the interlayer insulating layer  37  and the gate line  33  are etched such that the gate line  33  is divided into two gate lines. The two gate lines form a first gate line  43   a  having a width of X′ and a second gate line  43   b  having a width of X″ (See FIG. 4).  
         [0048]    Referring to FIG. 6 d , the remaining patterned photoresist layer  38  is removed. Impurity ions are implanted into the exposed surface of the substrate  30  between the first and second gate lines  43   a  and  43   b , thus forming a second source/drain region  39 . In this case, the second source/drain region  39  has the same impurity ions as the first source/drain regions  35 . However, the concentration of the first and second source/drain regions  35  and  39  are different. The ions of a different concentration are implanted and a thermal diffusion is carried out, forming an unsymmetrical device, (i.e., source and drain regions having different ion concentrations).  
         [0049]    An oxide layer is then subsequently formed and anisotropically etched to form oxide sidewall spacers  40  on inner sides of the first and second gate lines  43   a  and  43   b  and on a side surface of the interlayer insulating layer  37 . Subsequently, a conductive material is formed on the entire surface and then patterned to form a contact plug  41   a  and a bit line  41  whereby the bit line  41  connects with the contact plug  41   a . Thus, the above process completes the semiconductor device of the present invention. Also, the conductive material for the bit line plug  41   a  and the bit line  41  are preferably a polysilicon, aluminum, or tungsten type material.  
         [0050]    A method for manufacturing a semiconductor device of the present invention has the following advantages.  
         [0051]    First, since oxide sidewall spacers  40  are formed (after dividing a gate line into two gate lines) on an inner side surface between the two gate lines, a contact plug, which is in contact with a bit line, is not formed over the gate lines avoiding a short between the gate lines and a bit line. As a result, a device having of good reliability can be manufactured.  
         [0052]    Second, a mask to divide the gate line can be replaced with a conventional mask to define a contact hole. Thus, the manufacturing process becomes simplified, e.g., because the mask inventory can be reduced by one mask.  
         [0053]    Third, by splitting a single gate line structure in the present invention, a contact hole is concurrently formed along with the two gate lines, which permits a single masking step to replace the separate masking steps needed to form the two gate lines and for the contact hole.  
         [0054]    Fourth, first source drain regions at both sides of the gate lines and a second source/drain in between the divided gate lines are formed, respectively, by ion implantation of different concentrations, thereby forming an unsymmetrical device.  
         [0055]    Fifth, a more precise contact hole is formed by dividing a single gate line into two gate lines that avoid aligning a contact hole between the two gate lines.  
         [0056]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.