Abstract:
A method for manufacturing a semiconductor device is provided. In particular, a method for removing unwanted material layers from an edge and lower bevel region of a wafer is provided. The method includes performing a first etch of an edge region of a wafer having material layers formed thereon, coating the wafer with a photoresist layer, and patterning the photoresist layer to expose at least the edge and an upper bevel region of the wafer for etching the material layers remaining after performing the first etch.

Description:
RELATED APPLICATION(S) 
   This application claims the benefit under 35 USC §119(e) of Korean Patent Application No. 10-2005-0132296 filed Dec. 28, 2005, which is incorporated herein by reference in its entirety. 
   FIELD OF THE INVENTION 
   The present invention relates to a method for manufacturing a semiconductor device. 
   BACKGROUND OF THE INVENTION 
   The manufacturing process of a semiconductor integrated circuit typically includes a series of processes for depositing conductive layers and insulating layers on the entire surface of a semiconductor wafer and patterning the material layers forming each layer to realize the semiconductor integrated circuit as designed. 
   In general, a semiconductor integrated circuit includes a plurality of units of semiconductor chips formed by carrying out the same processes in the same steps with respect to the plurality of semiconductor chips on the semiconductor wafer. Thus, after forming an uppermost material layer on each semiconductor chip unit, the semiconductor wafer is diced into the semiconductor chips and end parts thereof are discarded as unnecessary portions. 
   Because the manufacturing process for the semiconductor device is typically carried out relative to the entire surface of a semiconductor wafer, the material layers tend to form on the edge of the semiconductor wafer. However, the edge of the semiconductor wafer is an imperfect region in terms of crystallization, energy distribution, and mechanical strength, so the edge of the semiconductor wafer causes various defects in the process of forming the semiconductor integrated circuit. 
   That is, as semiconductor integrated circuits have become highly integrated, material layers accumulated on the edge and the bevel region of the wafer may cause various types of defects, such as expansion due to a thermal budget derived from, for example, deposition of a subsequent material layer, a lifting of a material layer, an incomplete removal of a material layer caused by a difference of selectivity between layers relative to a chemical used in dry etching or wet etching, and polymer residue. Such defects may generate particles, which penetrate into a semiconductor chip region in the process of manufacturing the semiconductor integrated circuit, thereby causing defects of the semiconductor integrated circuit. 
   Therefore, the material layers formed on an edge of the wafer have to be periodically removed therefrom during the manufacturing process for the semiconductor integrated circuit. 
     FIGS. 1 and 2  show a conventional method for processing a wafer edge. 
   Referring to  FIG. 1 , a tungsten silicide layer or a tungsten layer  61 , a silicon nitride layer  62  and a silicon oxide layer  63  are formed on an edge of a wafer  60  in a process of manufacturing a semiconductor integrated circuit. 
   In order to remove such unnecessary material layers formed on the edge of the wafer  60 , in a conventional process, a photoresist layer  64  is coated on the entire surface of the wafer  60  including a semiconductor chip region (not shown) and then a pattern of the photoresist layer  64  having a regular width is formed from the edge of the wafer  60  through a photo process. 
   Referring to  FIG. 2 , the silicon oxide layer  63  exposed at the edge and a rear side of the wafer  60  is removed by a wet chemical etch using the photoresist layer  64  as a mask. Then, the photoresist layer  64  is removed by ashing and stripping processes. 
   After that, the exposed silicon nitride layer  62  is removed by using an appropriate chemical while employing the silicon oxide layer  63  as a mask. Subsequently, the exposed tungsten silicide layer or tungsten layer  61  is removed. 
   However, the conventional method does not completely remove the silicon oxide layer  63  from the edge and a lower region of the wafer  60 . Instead, the residue of the silicon oxide layer  63  may remain on the edge and the lower region of the wafer  60 . 
   Therefore, it is necessary to ensure that the silicon oxide layer or other material layers remaining on the edge and the lower region of the wafer are removed. 
   BRIEF SUMMARY 
   Accordingly, an object of the present invention to provide a method for completely removing material layers formed on an edge and a bevel region of a wafer. 
   In accordance with one aspect of the present invention, there is provided a method for manufacturing a semiconductor device, the method comprising the steps of: performing a first etch of material layers formed on a wafer with respect to an edge region and a lower bevel region of the wafer; coating a photoresist layer on the material layers on the wafer; and patterning the photoresist layer to expose at least the edge region and the lower bevel region of the wafer, wherein at least a portion of the material layers formed on the edge region and the lower bevel region of the wafer is removed before forming the photoresist layer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1 and 2  are sectional views showing a conventional method for processing a wafer edge; 
       FIG. 3  is a view for schematically illustrating a method for manufacturing a semiconductor device according to an embodiment of the present invention; and 
       FIGS. 4 to 6  are sectional views illustrating a method for manufacturing a semiconductor device according to an embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Hereinafter, a manufacturing process for a semiconductor device in accordance with embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
     FIG. 3  is a view for schematically illustrating a method for manufacturing a semiconductor device according to an embodiment of the present invention. 
   Referring to  FIG. 3 , a wafer  210  can be placed between a lower plate  220  and an upper plate  230 . In one embodiment, an oxide layer formed on an edge region and a lower region of the wafer  210  can be removed by feeding a reaction gas into a chamber where the wafer  210  is interposed between the plates  220  and  230 . 
   Material layers, such as an oxide layer, a metallic layer, etc., can be formed on the wafer  210  during previous processes. For the process for removing the material layers from an edge and lower region of the wafer using plates  220  and  230 , the lower plate  220  and the upper plate  230  can be part of a plasma processing apparatus. 
   When a wafer  210  is placed between the lower plate  220  and the upper plate  230 , the plates  220  and  230  can make close contact with a portion of the wafer  210  to prevent penetration of the reaction gas at the contacted portion of the wafer. Therefore, the plates  220  and  230  can prevent a portion of the wafer  210  from reacting with the plasma. 
   Therefore, a portion of the oxide layer exposed to the reaction gas can be removed from the edge region and lower region of the wafer  210 . Thus, according to embodiments of the present invention, an etching process can be selectively carried out with respect to a bevel region of the wafer  210 . 
   In a further embodiment, the above described processes can be repeatedly carried out for a wafer including a metallic material such as an aluminum material formed on the edge region and the lower region of the wafer  210  in addition to the oxide layer. 
   According to one embodiment of the subject invention, the metallic material and the oxide layer formed on the edge region and the lower region of the wafer  210  can be simultaneously removed. 
   In a specific embodiment, dry etching process may be carried out in the plasma processing apparatus under the conditions of 1 to 2 Torr, 400 to 900 Watt, 50 to 150 SCCM SF 6 , 50 to 200 SCCM CF 4 , and 5 to 30 SCCM O 2 . 
   By removing impurities existing on the edge and the lower region (the bevel region) of the wafer  210 , it may be possible to prevent characteristics of the semiconductor device from being affected by particles in subsequent processes. 
     FIGS. 4 to 6  are sectional views illustrating a method for manufacturing a semiconductor device according to an embodiment of the present invention. 
   In  FIGS. 4 to 6 , a cross section of the wafer  210  is shown. In particular,  FIG. 4  shows an edge region  4   a  and a lower bevel region  4   b  of the wafer  210 . 
   Referring to  FIG. 4 , in one method of manufacturing a semiconductor device, a metallic layer  211 , a nitride layer  212  and an oxide layer  213  can be sequentially deposited on a wafer  210 . 
   During the process steps for depositing the metallic layer  211 , the nitride layer  212  and the oxide layer  213 , these material layers  211 ,  212 , and  213  can also form on the edge region  4   a  of the wafer. In addition, the oxide layer  213  can also form on the lower region of the wafer including the lower bevel region  4   b.    
   To remove unwanted portions of the material layers, such as material layers  211 ,  212 , and  213 , the wafer  210  can be interposed between an upper plate  230  and a lower plate  220  before a step of forming a photoresist pattern for exposing the end region of the wafer. The upper plate  230  and the lower plate  220  can be installed as a part of a plasma processing apparatus. 
   In a specific embodiment, the wafer  210  can make close contact with the upper plate  230  and the lower plate  220  while exposing the edge region  4   a  and the lower bevel region  4   b  of the wafer  210 . 
   Thereafter, SF 6 , CF 4  and O 2  gases can be injected into the plasma processing apparatus. These injected gases can make contact with the exposed edge region  4   a  and the lower bevel region  4   b  of the wafer  210  to perform an etch of the exposed regions. 
   In one embodiment, the dry etching may be carried out in the plasma processing apparatus under the conditions of 1 to 2 Torr, 400 to 900 Watt, 50 to 150 SCCM SF 6 , 50 to 200 SCCM CF 4 , and 5 to 30 SCCM O 2 . 
   According to embodiments, the injected gases do not reach a predetermined portion of the wafer  210  that makes close contact with the upper plate  230  and the lower plate  220 , but the injected gases do make contact with the exposed edge region  4   a  and the lower bevel region  4   b  of the wafer  210 . 
   Referring to  FIG. 5 , by the dry etching in the plasma processing apparatus, the oxide layer  213  formed on the edge region  4   a  and the lower bevel region  4   b  of the wafer  210  can be removed. 
   Then, a photoresist layer  214  can be formed and patterned on the wafer  210  such that an end region including the edge region  4   a  of the wafer  210  is exposed. 
   Referring to  FIG. 6 , the oxide layer  213 , the nitride layer  212  and the metallic layer  211  can be etched using the photoresist layer  214  as an etch mask. 
   The etching process using the photoresist layer  214  as the mask may include a wet etching process. In addition, because the oxide layer  213  can be removed from the edge region  4   a  and the lower bevel region  4   b  of the wafer  210  in a first etch step, the material layers including the oxide layer will not be left remaining on the edge region  4   a  and the lower bevel region  4   b  of the wafer  210 . 
   In a specific embodiment, the wet etching process may be carried out under the conditions of 55° C., HF 49% to 55%, and 500 to 1000 RPM. 
   It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application.