Abstract:
The present invention discloses methods for manufacturing a metal line of a semiconductor device that can prevent undesirable etching of an edge of an interlayer insulating film. In accordance with the method, a lower metal line exposed by a via contact hole is covered by a photoresist film pattern which is formed via an exposure and development process using an upper metal line mask. An etching process is performed using the photoresist film pattern as a mask to form the upper metal line region that is then filled to form an upper metal line after removing the photoresist film pattern.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a method for manufacturing a metal line of a semiconductor device, and in particular to an improved method for manufacturing metal line of semiconductor device wherein undesirable etching of an edge of an interlayer insulating film which causes electrical shorts between metal lines can be prevented. 
   2. Description of the Background Art 
   A semiconductor device includes a plurality of vertically stacked electrical wiring layers and connection layers connecting vertically stacked electrical wiring layers. 
   In case of logic devices, gates and metal layers correspond to the electrical wiring layers, and contact hole layers connecting gates and metal layers and via contact hole layers connecting upper and lower wiring layers correspond to the connection layers. 
   In accordance with a conventional method for manufacturing metal line of semiconductor device, a metal line is formed on a planarized surface and an interlayer insulating film planarizing the entire surface is then formed. However, this method is disadvantageous in that the patterning of metal lines having microscopic widths is very difficult. 
   A new method, namely a damascene method wherein a interlayer insulating film having a groove for metal line is formed on a planarized surface and the groove is filled with metal have been proposed to overcome the disadvantages of the conventional method, which is described hereinbelow. 
     FIGS. 1   a  through  1   e  are cross-sectional diagrams illustrating a conventional damascene method for manufacturing metal line of semiconductor device. 
   Referring to  FIG. 1   a,  a lower structure such as a device isolation film (not shown) defining an active region, a word line (not shown), a bit line (not shown) and a capacitor (not shown) are formed on a semiconductor substrate (not shown). A lower insulating layer (not shown) is deposited to planarize the entire surface. 
   Thereafter, a lower metal line  11  connected to the lower structure is deposited on the lower insulating layer using copper. A first insulating film  13  exposing a top surface of the lower metal line  11  is then formed on the entire surface. 
   Next, a stacked structure of a first etch barrier film  15 , a second interlayer insulating film  17 , a second etch barrier film  19 , a third interlayer insulating film  21  and a hard mask layer  23  is formed on the entire surface. The stacked structure is then etched via a photolithography process using metal line contact mask (not shown), i.e. via contact mask (not shown) to expose the first etch barrier film  15 . 
   Now referring to  FIG. 1   b,  an organic anti-reflection film  27  is deposited on the entire surface. Thereafter, a photoresist pattern  29  is formed on the organic anti-reflection film  27 . The photoresist pattern  29  is formed via exposure and development process using metal line mask. 
   Referring to  FIG. 1   b,  the organic anti-reflection film  27 , the hard mask layer  23  and the third interlayer insulating film  21  are etched using the photoresist pattern  29  as a mask to expose the second etch barrier film  19 . The organic anti-reflection film  27  remains between the second interlayer insulating film and the first etch barrier film  15 . 
   Now referring to  FIG. 1   d,  the photoresist pattern  29  and the organic anti-reflection film  27  are sequentially removed to expose the first etch barrier film  15  on the lower metal line  11 . 
   Referring to  FIG. 1   e,  the exposed portion of the first etch barrier film  15  is removed via an etch-back process to form an upper metal line region  31  for contacting the lower metal line  11 . The etch-back process is performed without using a mask, wherein the edges of the second etch barrier film  19 , the second interlayer insulating film  17 , and the hard mask layer  23  are etched to have a shape denoted as ‘A’ in  FIG. 1   e.    
   The edges having the shape denoted as ‘A’ in  FIG. 1   e  has an effect of reducing the distance between the upper metal lines to cause shorts between the upper metal lines. The short between the upper metal lines degrades the electrical characteristic of metal lines. 
     FIG. 2  is a SEM photograph showing copper lines manufactured in accordance with the conventional method. As can be seen from  FIG. 2 , the critical dimension between the copper lines is reduced. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an object of the present invention to provide a method for manufacturing metal line of semiconductor device wherein a lower metal line exposed through a via contact hole is covered by a photoresist pattern so that the edge of an interlayer insulating film at the top corner of the via contact hole is not etched during a formation process of upper metal line region to prevent the reduction of distance between metal lines which causes short between the metal lines. 
   In order to achieve the above-described object of the invention, there is provided a method for manufacturing metal lines of semiconductor device, the method comprising the steps of: forming a first interlayer insulating film exposing a top portion of a lower metal line on a semiconductor substrate; forming a stacked structure of a first etch barrier film, a second interlayer insulating film, a second etch barrier film, a third interlayer insulating film and an anti-reflection film; etching the stacked structure to form a via contact hole exposing a portion of the first interlayer insulating film on the lower metal line; removing the exposed portion of the first interlayer insulating film to expose the lower metal line; forming a photoresist film on the entire surface; subjecting the photoresist film to an exposure and development process using an upper metal line mask to form a photoresist film pattern for defining an upper metal line region, wherein the photoresist film pattern further fills a portion of the via contact hole; etching the anti-reflection film and the third interlayer insulating film using the photoresist film pattern as a mask to form the upper metal line region; removing the photoresist film pattern; and forming an upper metal line contacting the lower metal line by filling the upper metal line region. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become better understood with reference to the accompanying drawings that are given only by way of illustration and thus are not limitative of the present invention, wherein: 
       FIGS. 1   a  through  1   e  are cross-sectional diagrams illustrating a conventional damascene method for manufacturing metal lines of semiconductor device. 
       FIG. 2  is a SEM photograph showing metal lines manufactured in accordance with the conventional method. 
       FIGS. 3   a  through  3   e  are cross-sectional diagrams illustrating a method for manufacturing metal lines of semiconductor device in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A method for manufacturing metal line of semiconductor device in accordance with a preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings. 
     FIGS. 3   a  through  3   e  are cross-sectional diagrams illustrating a method for manufacturing metal lines of semiconductor device in accordance with the present invention. 
   Referring to  FIG. 3   a,  a lower structure such as a device isolation film (not shown) defining an active region, a word line (not shown), a bit line (not shown) and a capacitor (not shown) are formed on a semiconductor substrate (not shown). A lower insulating layer (not shown) is then deposited to planarize the entire surface. 
   Thereafter, a lower metal line  41  connected to the lower structure is deposited on the lower insulating layer preferably using copper. A first insulating film  43  exposing a top surface of the lower metal line  41  is then formed to planarize the entire surface. 
   Next, a first etch barrier film  45  is formed on the entire surface. The first etch barrier film  45  serves as a capping layer for copper and preferably comprises an insulating film, for example SiN film, SiC film or SiCN film. 
   Still referring to  FIG. 3   a,  a second interlayer insulating film  47  is formed on the first etch barrier film  45 . In one embodiment, the second interlayer insulating film  47  preferably comprises a film selected from the group consisting of an oxide film, an organic low-k film, an organic porous low-k film and combinations thereof. In another embodiment, the second interlayer insulating film  47  preferably comprises a silica-base low-k film or a silica-base porous low-k film. 
   Thereafter, a second etch barrier film  49  and a third interlayer insulating film  51  are sequentially deposited on the second interlayer insulating film  47 . The third interlayer insulating film  51  preferably consists of the same material as the first etch barrier film  45 . 
   Next, an anti-reflection film  53  is formed on the third interlayer insulating film  51 . Preferably, the anti-reflection film  53  comprises SiON inorganic anti-reflection film. The thickness of the anti-reflection film  53  is determined by considering the thickness of the anti-reflection film  53  etched during the etching process of the first and the second etch barrier films. For example, when an anti-reflection film  53  having a thickness of 600 Å is required and thickness of about 400 Å is etched during the etching process, initial thickness of the anti-reflection film  53  should be about 1000 Å. 
   The anti-reflection film  53 , the third interlayer insulating film  51 , the second etch barrier film  49  and the second interlayer insulating film  47  are etched via a photolithography process using metal line contact mask (not shown), i.e. via contact mask (not shown) to form a via contact hole  55  exposing the first etch barrier film  45 . 
   Referring to  FIG. 3   b , the exposed portion of the first etch barrier film  45  at the bottom of the via contact hole  55  is removed via an etching process. Portions of the anti-reflection film  53 , i.e. a top and edge portions of the anti-reflection film  53  are etched in the etching process of the first etch barrier film  45 . As a result, the thickness of the anti-reflection film  53  is reduced and the edge portion of the anti-reflection film  53  at the top corner of the via contact hole  55  is etched to have a shape denoted as ‘B’ in  FIG. 3   b.    
   Now referring to  FIG. 3   c,  a photoresist film (not shown) is formed on the entire surface and the photoresist film is exposed and developed using a metal line mask (not shown) to form a photoresist film pattern  59 . A portion of the photoresist film remains at the bottom of the via contact hole  55  so that the photoresist film pattern  59  covers the lower metal line  41 . 
   When the photoresist film pattern  59  at the bottom of the via contact hole  55  does not sufficiently fill the bottom of the via contact hole  55 , i.e. when the thickness of the photoresist film pattern  59  at the bottom of the via contact hole  55  is not sufficient, the lower metal line  41  may be damaged or contaminated in the subsequent etching process. In order to prevent the damage or contamination of the lower metal line, the photoresist film pattern  59  at the bottom of the via contact hole  55  should have a sufficient thickness. 
   Referring to  FIG. 3   d,  the anti-reflection film  53  and the third interlayer insulating film  51  are etched using the photoresist film pattern  59  as a mask to form upper metal line region  61 . It is preferable that the anti-reflection film  53  and the third interlayer insulating film  51  are plasma-etched using a mixture gas of CF 4 /O 2 /Ar. 
   Referring to  FIG. 3   e , the portion of the photoresist film pattern  59  in the via contact hole  55  is removed preferably by performing an in-situ plasma-etching process using a mixture gas of CF 4 /O 2 /Ar. The remaining portion of the photoresist film pattern  59  is then removed. Edge portions of the anti-reflection film  53  and the second etch barrier film  49  in the upper metal line region  61 , which are denoted as ‘C’ in  FIG. 3   e , are not etched. 
   Thereafter, the upper metal line region  61  is filled to form an upper metal line (not shown). 
   As discussed earlier, in accordance with the present invention, the lower metal line exposed through the via contact hole is covered by the photoresist pattern so that the edge of an interlayer insulating film at the top corner of the via contact hole is not etched during a formation process of upper metal line region. This prevents short between the metal lines caused by the reduction of distance therebetween, thereby improving the electrical characteristics of semiconductor device. 
   As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiment is not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalences of such metes and bounds are therefore intended to be embraced by the appended claims.