Patent Abstract:
The present invention provides a semiconductor memory device capable of preventing bridge formations in a peripheral circuit region and improving a process margin and a method for fabricating the same. The semiconductor memory device includes: a cell region; a peripheral circuit region adjacent to the cell region; and a plurality of line patterns formed in the cell region and the peripheral circuit region, wherein a spacing distance between the line patterns is at least onefold greater than a width of the line pattern.

Full Description:
FIELD OF THE INVENTION 
   The present invention relates to a semiconductor device; and, more particularly, to a semiconductor memory device capable of improving a process margin in a peripheral circuit region and a method for fabricating the same. 
   DESCRIPTION OF RELATED ARTS 
     FIG. 1  is a top view schematically showing a conventional semiconductor memory device. 
   As shown, the semiconductor memory device  100  includes, e.g., four cell regions  101 A to  101 D and a peripheral circuit region  102 . 
   A cell efficiency of the semiconductor memory device, e.g., a dynamic random access memory (DRAM), typically ranges from about 60% to about 70%. The cell efficiency is a ratio of a cell region with respect to the total region (that is, the sum of the cell regions  101 A to  101 D and the peripheral circuit region  102 ). Generally, a design rule, i.e., a pattern density, of the peripheral circuit region  102  is decreased by about 10% to about 30% of the pattern density of the cell regions  101 A to  101 D. 
     FIG. 2  is a cross-sectional view illustrating a semiconductor memory device wherein line patterns are formed in a cell region and a peripheral circuit region. 
   As shown, a plurality of line patterns  103 A and  103 B, e.g., bit lines, are formed on a substrate SUB divided into a cell region  101  and a peripheral circuit region  102 . 
   Meanwhile, the peripheral circuit region  102  should be applied with the nearly identical design rule for the cell region in order to increase the cell efficiency. That is, the line pattern  103 B in the peripheral circuit region  102  has a ratio of a width W to a spacing distance D in about 1:1. 
   However, in the above case, a bridge  104  is formed between conductive layers  10  of the line pattern  103 B due to scummy remnants or a stringer caused by a loading phenomenon between the cell region  101  and the peripheral circuit region  102 . The scummy remnants are produced during an etch process for forming the line pattern  103 B due to an insufficient spacing distance D of the line pattern  103 B in the peripheral circuit region  102 . 
   Also, there also occurs a problem when forming a deep contact hole if the pattern density of the peripheral circuit region  102  increases. 
     FIG. 3  is a cross-sectional view schematically showing a conventional semiconductor memory device, wherein a deep contact hole is formed in a peripheral circuit region. 
   Referring to  FIG. 3 , a first insulation layer  13  is formed on a predetermined portion of a substrate SUB and line patterns  103 A and  103 B. Then, a second insulation layer  14  is formed thereon. In a cell region  101 , a capacitor  15  electrically connected to a source/drain junction region (not shown) of a substrate SUB through a plug  18  is formed. In the mean time, a photoresist pattern  16  for forming a deep contact hole  19  is formed in a peripheral circuit region  102 . 
   Next, the second insulation layer  14  is etched by using the photoresist pattern  16  as an etch mask so as to form the deep contact hole  19  exposing the conductive layer  10  of the line pattern  103 B. 
   As micronization of a semiconductor device has been accelerated, in the cell region  101 , a height of the capacitor  15  also increases in order to augment a cell capacitance within a limited narrow area. Thus, in the peripheral circuit region  102 , a height of the insulation layer  14  also increases proportionally. 
   However, the above increases of height provoke some problems; those are, an increased thickness of an etch target during the deep contact hole  19  formation, a shortage of an overlap margin in the etch process for forming the contact hole  19  and a decreased contact area to the conductive layer  10  in case that a misalignment occurs. The decreased contact area is denoted as a reference numeral  17  in  FIG. 3  and is a factor for increasing a contact resistance. 
   SUMMARY OF THE INVENTION 
   It is, therefore, an object of the present invention to provide a semiconductor memory device capable of efficiently preventing bridge formations in a peripheral circuit region and improving a process margin and a method for fabricating the same. 
   In accordance with an aspect of the present invention, there is provided a semiconductor memory device, including: a cell region; a peripheral circuit region adjacent to the cell region; and a plurality of line patterns formed in the cell region and the peripheral circuit region, wherein a spacing distance between the line patterns is at least onefold greater than a width of the line pattern. 
   In accordance with another aspect of the present invention, there is also provided a method for fabricating a semiconductor memory device including a cell region and a peripheral circuit region, including the steps of: forming a plurality of line patterns in the cell region and the peripheral circuit region, each being formed by stacking a conductive layer and an insulating hard mask; removing the insulating hard mask formed in the peripheral circuit region; forming a conductive spacer at sidewalls of each line pattern in the peripheral circuit region, wherein a spacing distance between the line patterns is at least onefold greater than a width of the line pattern; forming an insulation layer on an entire surface of the resulting structure; forming a photoresist pattern for forming a contact hole exposing the conductive layer on the insulation layer; and forming a deep contact hole exposing the conductive layer by etching the insulation layer with use of the photoresist pattern as an etch mask. 

   
     BRIEF DESCRIPTION OF THE DRAWING(S) 
     The above and other objects and features of the present invention will become apparent from the following description of the preferred embodiments given in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a top view schematically showing a conventional semiconductor memory device; 
       FIG. 2  is a cross-sectional view illustrating a conventional semiconductor memory device, wherein a plurality of line patterns are formed in a cell region and a peripheral circuit region; 
       FIG. 3  is a cross-sectional view schematically showing a conventional semiconductor memory device including a deep contact hole formed in the peripheral circuit region shown in  FIG. 2 ; and 
       FIGS. 4A to 4E  are cross-sectional views showing a process for forming a deep contact hole in accordance with a preferred embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Hereinafter, with reference to  FIGS. 4A to 4E , a semiconductor memory device including a deep contact hole and a method for fabricating the same will be described in detail. 
     FIG. 4A  is a cross-sectional view showing a plurality of line patterns. The line patterns in a cell region and a peripheral circuit region have a different ratio of a width W to a spacing distance D. Herein, the spacing distance D means a distance between the line patterns. 
   As shown, the semiconductor memory device is divided into a cell region  41  and a peripheral circuit region  42 . In each of these cell and peripheral circuit regions  41  and  42 , a plurality of line patterns  46 A and  46 B are formed in a uniformly disposed arrangement. 
   In the cell region  41 , the line pattern  46 A has a ratio of a width W to a spacing distance D in about 1:1. On the other hand, in the peripheral circuit region  42 , a ratio of the width W of the line pattern  46 B to the spacing distance D between the line patterns  46 B is in a range of about 1:1.05 to about 1:1.30. That is, the spacing distance D between the line patterns  46 B in the peripheral circuit region  42  is larger than the width of the line pattern  46 B by about 5% to about 30%. Therefore, it is possible to prevent a bridge formation between the line patterns  46 B caused by scummy remnants or a stringer. 
   Meanwhile, a ratio of the width W of the line pattern  46 B in the peripheral circuit region  42  to that of the line pattern  46 A in the cell region  41  is in a range of about 1:1 to about 1:1.3. 
   Herein, the line patterns  46 A and  46 B are conductive patterns such as bit lines and the like and include a conductive layer  43  contacted to a substrate  40 , a hard mask  44  deposited on top of the conductive layer  43  and a spacer  45  allocated at sidewalls of the conductive layer  43  and the hard mask  44 . 
   The conductive layer  43  is made of W or TiN. Each of the hard mask  44  and the spacer  45  is formed with a nitride-based layer such as a silicon nitride layer or a silicon oxide nitride layer. 
   Referring to  FIG. 4B , the above process for forming the line patterns  46 A and  46 B in the cell and peripheral circuit regions  41  and  42  will be explained in more detail. 
   On the substrate  40  providing several constitution elements of the semiconductor memory device, the conductive layer  43  and the nitride-based layer for the hard mask  44  are sequentially deposited. Then, a selective etch process is proceeded with use of a mask pattern for forming a line pattern so that a plurality of the line patterns  46 A and  46 B are formed in the cell region  41  and the peripheral circuit region  42 , respectively. 
   At this time, as described above, the ratio of the width W of the line pattern  46 A with respect to the spacing distance D between the line patterns  46 A is about 1:1 in the cell region  41 . This ratio is typically used in a semiconductor memory device. In the mean time, in the peripheral circuit region  42 , the ratio of the width W of the line pattern  46 B to the spacing distance D between the line patterns  46 B is in a range of about 1:1.05 to about 1:1.30. 
   Next, the nitride-based layer is deposited and proceeded with a blanket-etch process to thereby form the spacer  45  at sidewalls of the line patterns  46 A. 
   An oxide-based first insulation layer  47  is deposited on the above resulting structure. Herein, the first insulation layer  47  can be a single or stack layer of oxide-based layers. Examples of the oxide-based layer are a boron-phosphorus-silicate glass (BPSG) layer, a low pressure tetra-ethyl-ortho silicate (LPTEOS) layer, a plasma enhanced tetra-ethyl-ortho silicate (PETEOS) layer, a phosphorus-silicate glass (PSG) layer and a boron-silicate glass (BSG) layer. 
   After the first insulation layer  47  deposition, a peripheral circuit region  42  open mask (not shown) for masking only the cell region  41  is formed, and the first insulation layer  47  and the hard mask  44  of the peripheral circuit region  42  are removed. After the removal, a photoresist strip process is performed to remove the peripheral circuit region  42  open mask. 
   Next, a conductive layer is thinly deposited on the above entire structure. A blanket-etch process is then performed to form a conductive spacer  48  at sidewalls of the line patterns  46 B without the hard mask  44  in the peripheral circuit region  42  and at a sidewall of the first insulation layer  47  in the cell region  41  adjacent to the peripheral circuit region  42 . Herein, the conductive layer is made of such material as TiN, TaN, W or WN. 
   Dotted lines in  FIG. 4B  represent the conductive layer removed during the blanket-etch process.  FIG. 4B  is a cross-sectional view of the semiconductor memory device including the conductive spacer  48  formed at the sidewalls of the line patterns  46 B in the peripheral circuit region  42  and the sidewall of the first insulation layer  47  in the cell region  41 . Accordingly, there is provided an effect that the width W of the line patterns  46 B in the peripheral circuit region  42  is increased as much as the thickness of the conductive spacer  48 . 
   Referring to  FIG. 4C , a photoresist is coated on the above entire structure and a photolithography process is applied thereto to form a photoresist pattern  49 , which is a mask for a contact in the cell region  41 . Afterwards, the photoresist pattern  49  is used as an etch mask to form a contact hole  50  exposing the conductive layer or impurity contact region of the substrate  40  in the cell region  41 . Herein, the contact hole  50  formed in the cell region  41  is referred to as a cell contact hole. 
   Referring to  FIG. 4D , a conductive layer for forming a plug (not shown) is deposited in order to be filled into the cell contact hole  50 . Hereinafter, this conductive layer is referred as to a plug conductive layer. Afterwards, a planarization process is performed to form a plug  51  buried into the first insulation layer  47  and contacted to an exposed portion of the substrate  40 , and the photoresist pattern  49  is removed thereafter. 
   Subsequently, a capacitor  52  formation process is performed in the cell region  41 . The detailed description on the capacitor  52  formation process will be omitted. In the preferred embodiment of the present invention, the capacitor  52  is a concave type. 
   When the capacitor  52  is formed in the cell region  41 , a second insulation layer  53  having a thickness above about 10000 Å is formed in the cell region  41  and the peripheral circuit region  42 . Particularly, the second insulation layer  53  has a multi-layer structure including a high density plasma (HDP) oxide layer, a BSG layer, a BPSG layer or a PSG layer. 
   Then, a photoresist is coated on the second insulation layer  53 , and a photoresist pattern  54  for forming a contact hole is formed by performing a photolithography process using a light source of ArF or KrF in order to make a power line connection of the line patterns  46 B in the peripheral circuit region  42 . Herein, the above contact hole is a via hole. 
   The preferred embodiment of the present invention illustrates a case of using the photoresist pattern  54  having a T-shape when viewed in a plane level. However, it is still possible to use a photoresist pattern having a bar or circular shape. 
   After the photoresist pattern  54  is formed, the second insulation layer  53  is etched by using the photoresist pattern  54  as an etch mask to form a deep contact hole  55  exposing the conductive layer  43  of the line pattern  46 B. This deep contact hole  55  is shown in the  FIG. 4E . 
   Meanwhile, since the conductive spacer  48  is formed at the sidewalls of the line pattern  46 B in the peripheral circuit region  42  according to the preferred embodiment, an actual width of the line pattern  46 B is increased twice of the thickness of the conductive spacer  48 . Therefore, even if there occurs a misalignment when the photolithography process for forming the photoresist pattern  54  for the deep contact hole  55  is performed, a subsequent contact area is not decreased due to the above conductive spacer  48 . This effect is shown by the reference numeral  56  in  FIG. 4E . Also, this unaffected contact area provides a further effect of blocking an increase of contact resistance. 
   The preferred embodiment of the present invention shows that the ratio of the width W to the spacing distance D in the peripheral circuit region  42  is set to be higher than that in the cell region  41 , and thus, a pattern density of the peripheral circuit region  42  is lowered. This lowered pattern density prevents a bridge formation by remnants produced during the etching of the line patterns  46 A and  46 B. 
   Also, the conductive spacer  48  is formed at the sidewalls of each line pattern  46 B in the peripheral circuit region  42  after the hard mask is removed. Hence, the width of the line pattern  46 B in the peripheral circuit region  42  increases twice of the thickness of the conductive spacer  48 . As a result of this increased width of the line pattern  46 B, the contact area is not decreased even if a misalignment occurs when the deep contact hole is formed in the peripheral circuit region. Consequently, it is possible to block an increase of contact resistance. Ultimately, the above-described effects contribute to increase yields of semiconductor devices. 
   While the present invention has been described with respect to certain preferred embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined in the following claims.

Technology Classification (CPC): 7