Abstract:
Provided is a method of forming micro-patterns using a multi-photolithography process, including: providing an etch target layer where micro-patterns are to be formed; forming a mask layer on the etch target layer; forming a first mask pattern including engraved portions and embossed portions by etching a predetermined region of the mask layer; forming a final mask pattern in the first mask pattern by etching a predetermined region of the residual embossed portions of the mask layer; and forming micro-patterns by etching the etch target layer using the final mask pattern as an etch mask.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION  
       [0001]     This application claims priority to Korean Patent Application No. 10-2005-0095503, filed on Oct. 11, 2005, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a method of forming micro-patterns, and more particularly, to a method of forming micro-patterns using a multiple photolithography process.  
         [0004]     2. Description of the Related Art  
         [0005]     A patterning process used for manufacturing a semiconductor device is a process of patterning a predetermined material layer formed on a wafer, and generally includes applying a photosensitive film, exposing the film, and developing the film, in that order. Relatively small patterns can be referred to as micro-patterns.  
         [0006]     When forming micro-patterns the most significant factor during the patterning process is resolution, which depends on a light source and a lens apparatus used in a photolithography process.  
         [0007]     The increased integration required for semiconductor devices having micro-patterns and the reduction in design rules used to achieve the integration result in a need for an increase in the resolution of the photolithography process. Accordingly, the realization of a high resolution, beyond the limited resolution of a light source and a lens apparatus employed in a conventional optical lithography process, is required. Thus research focusing on a numerical aperture (NA) and a resolution enhancement technique (RET) has been performed.  
         [0008]     Due to such endeavors, a resolution of 60 nm has been attained for manufacturing devices using a dry ArF lithography process. However, there are several drawbacks in the photolithography process. That is, as defects between micro-patterns increase, such as, shorts, bridges, and pattern collapse, the yield of the devices decreases. Further, as the thicknesses of photoresists (Tpr) used for patterning continuously decrease, the photoresist cannot perform as a mask for subsequent etching processes. In addition, when the high numerical aperture is employed, there are problems in that the angle of incidence of light increases and the reflection ratio also increases.  
         [0009]     In addition, as semiconductor devices become more highly integrated, light transmitted through a photo mask having adjacent micro-patterns is diffracted and interferes when an exposure process is performed, such that a uniform critical dimension (CD) for the patterns cannot be obtained.  
         [0010]     To overcome the problems resulting from the small thicknesses of photoresists (Tpr) and the increase in the reflection ratio, structures having a multi-mask and an anti-reflection layer between a photoresist layer and an etch target layer have been suggested.  
         [0011]     The anti-reflection layer is used in a semiconductor lithography process as a very thin light-absorbing photosensitive material layer to stabilize essential micro-circuits for manufacturing gigabit (Gb) level ultra highly integrated semiconductors and should be matched with high resolution photoresist materials used in conventional processes to obtain good mutual interface contacting characteristics and light characteristics. Such anti-reflection layers are classified into top anti-reflective coating (TARC) layers when coated on the top surface of a photoresist layer and bottom anti-reflective coating (BARC) layers when coated on the bottom surface of a photoresist layer. BARC layers are used more in highly integrated semiconductor processes.  
         [0012]     In addition, to minimize light interference due to light diffraction in micro-patterns during an exposing process, a multi-lithography method using a plurality of photo masks is employed to form micro-patterns.  
         [0013]      FIGS. 1 through 12  are cross-sectional views illustrating a conventional method of forming micro-patterns in a semiconductor device. Referring to  FIG. 1 , a multi-layered mask layer  80 , a first anti-reflection layer  50 , and a first photoresist layer  60  are formed on an etch target layer  10 . The multi-layered mask layer  80  is formed on the etch target layer  10 , and includes a nitride layer  20 , an amorphous carbon layer  30 , and a silicon oxynitride layer  40 . The thin first anti-reflection layer  50  and the first photoresist layer  60  are formed on the multi-layered mask layer  80 . Accordingly, a five layer structure is formed on the etch target layer  10 .  
         [0014]     Referring to  FIG. 2 , a first photoresist pattern  61  is formed by exposing and developing the first photoresist layer  60  using a first photo mask  70 . Here, a first light blocking pattern  70   a  made of chrome, etc., is formed on a bottom surface of the first photo mask  70 .  
         [0015]     Referring to  FIG. 3 , a first anti-reflection pattern  51  is formed by etching the first anti-reflection layer  50  using the first photoresist pattern  61  as an etch mask.  
         [0016]     Referring to  FIG. 4 , a first silicon oxynitride pattern  41  is formed by partially etching the silicon oxynitride layer  40  using the first photoresist pattern  61  and the first anti-reflection pattern  51  as an etch mask.  
         [0017]     Referring to  FIG. 5 , the first photoresist pattern  61  and the first anti-reflection pattern  51  disposed on the first silicon oxynitride pattern  41  are removed.  
         [0018]     Referring to  FIG. 6 , a second photoresist layer  62  is formed on the first silicon oxynitride pattern  41 .  
         [0019]     Referring to  FIG. 7 , a second photoresist pattern  63  is formed by exposing and developing the second photoresist layer  62  using a second photo mask  71  having a second light blocking pattern  71   a.  The second photoresist pattern  63  is formed in the engraved portions of the first silicon oxynitride pattern  41 .  
         [0020]     Referring to  FIG. 8 , a final silicon oxynitride pattern  42  is formed by etching first silicon oxynitride pattern  41  using the second photoresist pattern  63  as an etch mask.  
         [0021]     Referring to  FIG. 9 , the second photoresist pattern  63  is removed and an amorphous carbon pattern  31  is formed by etching the amorphous carbon layer  30  using the final silicon oxynitride pattern  42  as an etch mask.  
         [0022]     Referring to  FIG. 10 , the final silicon oxynitride pattern  42  is removed and a nitride pattern  21  is formed by etching the nitride layer  20  using the amorphous carbon pattern  31  as an etch mask.  
         [0023]     Referring to  FIG. 11 , the amorphous carbon pattern  31  is removed and an etch target pattern  11  is formed by etching the etch target layer  10  using the nitride pattern  21  as an etch mask.  
         [0024]     Referring to  FIG. 12 , the nitride pattern  21  is removed.  
         [0025]     As described above, in the conventional process of forming micro-patterns in a highly integrated semiconductor device, a lower anti-reflection layer should be formed before forming the photoresist pattern in order to block light reflected when an exposure process is performed. However, in the conventional process of forming the second photoresist pattern  62 , it is difficult to uniformly form a lower anti-reflection layer because of the influence of the first silicon oxynitride pattern  41  previously formed.  
         [0026]     As illustrated in  FIG. 7 , since a positive patterning technique is used for forming the first silicon oxynitride pattern  41  in which the widths of embossed portions are less than those of engraved portions. If a spin-coating process is performed to form an anti-reflection layer (not shown) on the first silicon oxynitride pattern  41 , the anti-reflection layer might not be formed flatly. Rather, the anti-reflection layer could be formed concavely on engraved portions disposed between embossed portions in the first silicon oxynitride pattern  41 . When a photoresist pattern is formed using a photolithography process after forming a photoresist layer on the anti-reflection layer, which is not flat, the photoresist pattern may collapse, bridges may be generated in the photoresist pattern, and/or the sidewall profile of the photoresist pattern may be unfavorable. Consequently, if the subsequent processes are performed using this photoresist pattern as an etch mask, a desired micro-pattern cannot be obtained. Therefore, providing a second anti-reflection layer on the first silicon oxynitride layer  41  pattern, given the positive patterning technique of the first silicon oxynitride layer  41  pattern, could lead to defects in the micro-patterns of the semiconductor device.  
       SUMMARY OF THE INVENTION  
       [0027]     The present disclosure provides a method of forming micro-patterns using a multi-photolithography process which is unaffected by previously formed patterns.  
         [0028]     The present disclosure also provides a method of forming micro-patterns in which a flat anti-reflection layer can be formed without influence from patterns previously formed, and thus allowing the flat anti-reflection layer to be used favorably as a photoresist pattern.  
         [0029]     According to an aspect of the present disclosure, there is provided a method of forming micro-patterns including: providing an etch target layer where micro-patterns are to be formed; forming a mask layer on the etch target layer; forming a first mask pattern including engraved portions and embossed portions by etching at least one region of the mask layer; forming a final mask pattern by etching at least one region of the embossed portions of the mask layer; and forming micro-patterns by etching the etch target layer using the final mask pattern as an etch mask.  
         [0030]     The first mask pattern can be a line and space pattern in which embossed portions and engraved portions are alternately formed, and the widths of the embossed portions can be greater than the widths of the engraved portions.  
         [0031]     The mask layer can be a multi-layered mask layer.  
         [0032]     The multi-layered mask layer can include a silicon nitride layer, an amorphous carbon layer, and a silicon oxynitride layer stacked sequentially.  
         [0033]     The multi-layered mask layer can include a silicon nitride layer, an amorphous carbon layer, an oxide layer, and a silicon oxynitride layer stacked sequentially.  
         [0034]     The forming of the first mask pattern can include: forming a first photoresist pattern on the multi-layered mask layer; and forming the engraved portions of the first mask pattern by etching at least a portion of the multi-layered mask layer using the first photoresist pattern as an etch mask. The multi-layered mask can include an uppermost portion, and forming the engraved portions in the first mask pattern can include etching at least a portion of the uppermost layer of the multi-layered mask layer.  
         [0035]     The method can further include, after the forming of the first mask pattern: forming an anti-reflection layer on the first mask pattern using, for example, spin-coating; and forming a second photoresist pattern which exposes portions of the anti-reflection layer on the embossed portions of the mask layer.  
         [0036]     According to another aspect of the present invention, there is provided a method of forming micro-patterns including: providing an etch target layer where micro-patterns are to be formed; forming a hard mask layer on the etch target layer; forming a intermediate layer on the hard mask layer; forming a first intermediate pattern including engraved portions and embossed portions by etching at least one region of the intermediate layer; forming a final intermediate pattern in the first intermediate pattern by etching at least one region of the embossed portions of the intermediate layer; forming hard mask pattern by etching the hard mask layer using the final intermediate pattern as an etch mask; and forming micro-patterns by etching the etch target layer using the hard mask pattern as an etch mask.  
         [0037]     The hard mask layer can be a silicon nitride layer. The intermediate layer can be a mono-layered or multi-layered intermediate layer, for example, an amorphous carbon layer and a silicon oxynitride layer stacked sequentially. In the multi-layered intermediate layer, the silicon oxynitride layer can be partially etched to a predetermined depth to expose the oxide layer during the forming of the first intermediate pattern.  
         [0038]     The forming of the first intermediate pattern can include: forming a first photoresist pattern on the multi-layered intermediate layer; and forming the engraved portions of the first intermediate pattern by etching at least a portion of the multi-layered intermediate layer using the first photoresist pattern as an etch mask. The multi-layered intermediate layer can include an uppermost layer, and forming the engraved portions in the first intermediate pattern can include etching the uppermost layer of the multi-layered intermediate layer.  
         [0039]     The method can further include, after the forming of the first mask pattern: forming an anti-reflection layer on the first intermediate pattern; and forming a second photoresist pattern which exposes portions of the anti-reflection layer on the embossed portions of the hard mask layer.  
         [0040]     According to still another aspect of the present invention, there is provided a method of forming micro-patterns including: preparing an etch target layer where micro-patterns are to be formed; forming a hard mask layer on the etch target layer; sequentially forming a first intermediate layer and a second intermediate layer on the hard mask layer; forming a first photoresist pattern on the second intermediate layer; forming a second intermediate pattern being a line and space pattern with the widths of embossed portions being greater than the widths of engraved portions by etching a predetermined region of the second intermediate layer; forming an anti-reflection layer on the entire surface of the second intermediate pattern; forming a second photoresist pattern which exposes portions of the embossed portions of the second intermediate layer, on the anti-reflection layer; forming a final second intermediate pattern in the second intermediate pattern by etching the embossed portions of the second intermediate layer using the second photoresist pattern as an etch mask; forming a first intermediate pattern by etching the first intermediate layer using the final second intermediate pattern as an etch mask; forming a hard mask pattern by etching the hard mask layer using the first intermediate pattern as an etch mask; and forming micro-patterns by etching the etch target layer using the hard mask pattern as an etch mask.  
         [0041]     The method can further include forming an anti-etching intermediate layer between the first intermediate layer and the second intermediate layer. In the forming of the second intermediate pattern, the second intermediate layer can be partially etched to a predetermined depth or etched completely to expose the anti-etching intermediate layer.  
         [0042]     According to various aspects of the present invention, a multi-layered mask layer can be employed as a mask layer for an etch target layer to be patterned and a multi-exposure process using an ArF eximer laser having a wavelength of 193 nm as a light source can also be employed. Thus, micro-patterns with a critical dimension of less than 60 nm can be formed in a semiconductor device. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0043]     Various aspects of this disclosure will become more apparent in view of the attached drawing figures, which are provided by way of example, not by way of limitation.  
         [0044]      FIGS. 1 through 12  are cross-sectional views illustrating a conventional prior art method of forming micro-patterns;  
         [0045]      FIGS. 13 through 27  are cross-sectional views illustrating a method of forming micro-patterns according to an embodiment of the present disclosure; and  
         [0046]      FIGS. 28 through 42  are cross-sectional views illustrating a method of forming micro-patterns according to another embodiment of the present disclosure. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0047]     Hereinafter, embodiments in accordance with various aspects of the present disclosure will be described more fully with reference to the accompanying drawings, in which exemplary embodiments are shown. It will also be understood that when a layer is referred to as being “on” another layer or a substrate, it can be directly on the other layer or the substrate, or intervening layers can also be present. In any given layer or a substrate, there can be at least two surface levels formed in portions thereof, i.e., a higher level and a lower level. The higher level can be referred to as an “embossed” portion of the layer or substrate and the lower level can be referred to as an “engraved” portion of the layer or substrate. As an example, the engraved portion can be formed by etching and the embossed portions can be unetched. As used herein a “pattern” is a layer having at least one engraved portion, and can also be referred to as a “layer pattern.” In the drawings, like reference numerals denote like elements, and the sizes and thicknesses of layers and regions are exaggerated for clarity. Thickness in the embodiments below are intended to be representative, and not limiting.  
         [0048]      FIGS. 13 through 27  are cross-sectional views illustrating an exemplary embodiment of a method of forming micro-patterns in a target layer of a semiconductor device according to an embodiment of the present disclosure.  
         [0049]     Referring to  FIG. 13 , a multi-layered mask layer  800 , a first anti-reflection layer  500 , and a first photoresist layer  600  are formed on an etch target layer  100 . The multi-layered mask layer  800  is formed on the etch target layer  100 , which can be, for example, a semiconductor material layer, an insulation layer, a conduction layer, etc. The multi-layered mask layer  800  includes a silicon nitride layer  200 , as a hard mask layer with a thickness of approximately 2000 Å. On the silicon nitride layer  200 , the multi-layered mask layer  800  includes an amorphous carbon layer  300 , as the first intermediate layer, with a thickness of approximately 1500 Å and a silicon oxynitride layer  400 , as a second intermediate layer, with a thickness of approximately 1100 Å. The thin first anti-reflection layer  500  and the first photoresist layer  600  have thicknesses of approximately 380 Å and 1600 Å to 1800 Å, respectively. Accordingly, a five layer structure is formed on the etch target layer  100 , which is similar to  FIG. 1 . Micro-patterns are embodied in an etch target pattern  110  to be formed on the etch target layer  100 . The final etch target pattern  110   a  includes embossed portions and engraved portions arranged with a predetermined distance therebetween, as ultimately shown in  FIG. 27 .  
         [0050]     Referring to  FIG. 14 , a first photoresist pattern  610  is formed in the structure of  FIG. 13  by exposing and developing the first photoresist layer  600  using a first photo mask  710 . A first light blocking pattern  71 Oa is formed on a bottom side of the first photo mask  710  in order to perform a first photolithography process. The first light blocking pattern  710   a  is formed with a proper spacing and shape corresponding to the etch target pattern  110  (see  FIG. 27 ) to be formed. In the current embodiment, the etch target pattern  110  is a line and space pattern in which embossed portions and engraved portions having respective predetermined widths are alternately formed. In these embodiments, the widths of the engraved portions in the first photoresist pattern  610  are less than those of embossed portions in the first photoresist pattern  610 . The first photo mask  710  and a second photo mask  720  (see  FIG. 19 ) are separately formed to collectively define the etch target pattern  110  by a multi-photolithography process. These photo masks are shaped to correspond to the engraved portions of the etch target pattern  110 . That is, for example, the first photo mask  710  includes regularly divided portions for exposing substantially parallel, odd engraved portions in the etch target pattern  110 , and a second photo mask  720  used in a subsequent process includes regularly divided portions for exposing substantially parallel, even engraved portions in the etch target pattern  110 . Here, the odd portions and the even portions are arbitrarily chosen from either side in the etch target  110 .  
         [0051]     Referring to  FIG. 15 , a first anti-reflection pattern  510  is formed by etching the first anti-reflection layer  500  using the first photoresist pattern  610  as an etch mask. The etching process can be anisotropic dry etching, for example, dry etching using plasma, reactive ion etching, and so on. Such dry etching processes are known in the art, so not described in detail herein.  
         [0052]     Referring to  FIG. 16 , a first silicon oxynitride pattern  410  is formed by partially etching the silicon oxynitride layer  400  using the first photoresist pattern  610  and the first anti-reflection pattern  510  as an etch mask. When the layer under the silicon oxynitride layer  400  is the amorphous carbon layer  300 , the first silicon oxynitride pattern  410  is partially etched to a predetermined depth so as not to expose the amorphous carbon layer  300 . Since the amorphous carbon layer  300  has similar etch selectivity to the photoresist pattern  610  and the first anti-reflection pattern  510 , the amorphous carbon layer  300  could be damaged if exposed when removing the photoresist pattern  610  and the first anti-reflection pattern  510  after forming the first silicon oxynitride pattern  410 .  
         [0053]     Referring to  FIG. 17 , the first photoresist pattern  610  and the first anti-reflection pattern  510  disposed on the first silicon oxynitride pattern  410  are removed, for example, using a conventional ashing and stripping process. In doing so, the first silicon oxynitride pattern  410  is exposed.  
         [0054]     Referring to  FIG. 18 , a second anti-reflection layer  520  and a second photoresist layer  620  are sequentially formed on the first silicon oxynitride pattern  410 . The second anti-reflection layer  520  can be formed on the first silicon oxynitride pattern  410  using a spin-coating method, for example. Since the embossed portions of the first silicon oxynitride pattern  410  are wider than the engraved portions, the second anti-reflection layer  520  can be formed uniformly and flatly on the embossed portions. Thus, a second photoresist pattern  630  (see  FIG. 20 ) can be favorably formed on the flat second anti-reflection layer  520 , as described later with respect to  FIG. 20 .  
         [0055]     Referring to  FIG. 19 , a second photoresist pattern  630  is formed by exposing and developing the second photoresist layer  620  using the second photo mask  720 , which has a second light blocking pattern  720   a.  The second photoresist pattern  630  is formed by the second photo mask  720  having a second light blocking pattern  720   a  corresponding to engraved portions to be formed in the embossed portions not exposed by the first photoresist pattern  610 .  
         [0056]     Referring to  FIG. 20 , a second anti-reflection pattern  530  is formed by etching the second anti-reflection layer  520  using the second photoresist pattern  630  as an etch mask. The etching can be an anisotropic dry etching, for example, dry etching using plasma, reactive ion etching, and so on. Such dry etching processes are known in the art, as mentioned above.  
         [0057]     Referring to  FIG. 21 , a second, here a final, silicon oxynitride pattern  420  is formed in the silicon oxynitride layer  400  by etching the first silicon oxynitride pattern  410  (see  FIG. 17 ) using the second photoresist pattern  630  and the second anti-reflection pattern  530  as an etch mask. The embossed portions of the first silicon oxynitride pattern  410  are exposed by the second photoresist pattern  630  and etched to define other engraved portions of the silicon oxynitride layer  400 , in addition to the engraved portions formed by the first photoresist pattern  610 . As a result, the final silicon oxynitride pattern  420  has the same image as the etch target pattern  110  to be formed in  FIG. 27 .  
         [0058]     Referring to  FIG. 22 , the second photoresist pattern  630  and the second anti-reflection pattern  530  disposed on the final silicon oxynitride pattern  420  are removed, for example, using a conventional ashing and stripping process. In doing so, the final silicon oxynitride pattern  420  is exposed.  
         [0059]     Referring to  FIG. 23 , the final silicon oxynitride pattern  420  is etched to expose the amorphous carbon layer  300  thereunder.  
         [0060]     Referring to  FIG. 24 , an amorphous carbon pattern  310  is formed by etching the amorphous carbon layer  300  using the final silicon oxynitride pattern  420  as an etch mask. The final silicon oxynitride pattern  420  used as a hard mask for forming the amorphous carbon pattern  310  can partially remain on the amorphous carbon pattern  310  when the forming of the amorphous carbon pattern  310  is finished.  
         [0061]     Referring to  FIG. 25 , a nitride pattern  210  is formed by etching the nitride layer  200  using the amorphous carbon pattern  310  as an etch mask. At this time, the final silicon oxynitride pattern  420  can be used with the amorphous carbon pattern  310  to etch the nitride layer  200 , or can be removed before forming the nitride pattern  210 . The amorphous carbon pattern  310  used as a hard mask for forming the nitride pattern  210  can partially remain on the nitride pattern  210  when the forming of the nitride pattern  210  is finished.  
         [0062]     Referring to  FIG. 26 , the etch target pattern  110  is formed by etching the etch target layer  100  using the nitride pattern  210  as an etch mask. At this time, the amorphous carbon pattern  310  can be used with the nitride pattern  210  to etch the etch target layer  100 , or can be removed before forming the etch target pattern  110 . The nitride pattern  210  used as a hard mask for forming the etch target pattern  110  can partially remain on the etch target pattern  110  when the forming of the etch target pattern  110  is finished.  
         [0063]     Referring to  FIG. 27 , the nitride pattern  210  disposed on the etch target pattern  110  is removed.  
         [0064]     In the method of forming micro-patterns according to the current embodiment, the silicon oxynitride layer  400  is disposed on the amorphous carbon layer  300 , and the first silicon oxynitride pattern  410  is partially etched so as not to expose the amorphous carbon layer  300 . It is desirable to also form the final silicon oxinitride pattern within the embossed portions of the first silicon oxynitride pattern  410 , without damaging the amorphous carbon layer  300 . Since the amorphous carbon layer  300  has similar etch selectivity to the photoresist pattern  610  and the first anti-reflection pattern  510 , the amorphous carbon layer  300  could be damaged if exposed when removing the photoresist pattern  610  and the first anti-reflection pattern  510  after forming the first silicon oxynitride pattern  410 .  
         [0065]     However, since the first silicon oxynitride pattern  410  is formed such that the engraved portions are wider than then embossed portions, a second anti-reflection layer  520  can be formed prior to forming the second photo resist layer  620 . As a result, the amorphous carbon layer  300  is protected when forming the final silicon oxynitride pattern  420 , after forming the first silicon oxynitride pattern  410 , and the risk of defects occurring is mitigated.  
         [0066]     According to another exemplary embodiment of the present invention, a multi-mask layer includes an oxide layer, an amorphous carbon layer, a phenyl triethoxysilanes (PTEOS) layer, and a silicon oxynitride layer. The PTEOS lay can serve as an anti-etching layer, as described below.  
         [0067]      FIGS. 28 through 42  are cross-sectional views illustrating a method of forming micro-patterns according to another embodiment of the present invention. Descriptions of operations identical, or substantially similar, to those in the previous embodiment will be omitted.  
         [0068]     Referring to  FIG. 28 , a multi-layered mask layer  900 , a first anti-reflection layer  500   a,  and a first photoresist layer  600   a  are formed on an etch target layer  100   a.  The multi-layered mask layer  900  is formed on the etch target layer  100   a,  and can include, for example, a nitride layer or oxide layer  200   a  with a thickness of approximately 2000 Å, an amorphous carbon layer  300   a  with a thickness of approximately 1800 Å, a PTEOS layer  200   b  with a thickness of approximately 700 Å, and a silicon oxynitride layer  400   a  with a thickness of approximately 600 Å. The thin first anti-reflection layer  500   a  and the first photoresist layer  600   a  have thicknesses of approximately 380 Å and 1600 Å to 1800 Å, respectively. Accordingly, a six layer structure is formed on the etch target layer  100   a.  Using the method described below, micro-patterns are ultimately embodied in an etch target pattern  110   a  formed in the etch target layer  100   a.  The etch target pattern  110  includes embossed portions and engraved portions arranged with a predetermined distance therebetween, as ultimately shown in  FIG. 42 .  
         [0069]     As with the method of  FIGS. 13-27 , the first photo mask  710  and the second photo mask  720  (see  FIG. 34 ) are separately formed to define the etch target pattern  110   a  by a multi-photolithography process. The first and the second photo masks  710  and  720  have shapes used to ultimately form the engraved portions of the etch target pattern  110   a.  That is, for example, the first photo mask  710  includes regularly divided portions for exposing substantially parallel, odd engraved portions in the etch target layer real pattern  110   a,  and the second photo mask  720  used in a subsequent process includes regularly divided portions for exposing substantially parallel, even engraved portions in the etch target pattern  110   a.  Here, the odd portions and the even portions are arbitrarily chosen from either side in the etch target layer real pattern  110   a.    
         [0070]     Referring to  FIG. 29 , a first photoresist pattern  610   a  is formed in the structure of  FIG. 28  by exposing and developing the first photoresist layer  600   a  using the first photo mask  710 . Photo mask  710  includes the first light blocking pattern  710   a,  as in  FIG. 14 , formed on the bottom side of the first photo mask  710  used in the first photolithography process.  
         [0071]     Referring to  FIG. 30 , a first anti-reflection pattern  510   a  is formed by etching the first anti-reflection layer  500   a  using the first photoresist pattern  610   a  as an etch mask. The etching process can be an anisotropic dry etching, for example, dry etching using plasma, reactive ion etching, etc., as mentioned above.  
         [0072]     Referring to  FIG. 31 , a first silicon oxynitride pattern  410   a  is formed by partially etching the silicon oxynitride layer  400   a  using the first photoresist pattern  610   a  and the first anti-reflection pattern  510   a  as an etch mask. When the layer under the silicon oxynitride layer  400   a  is an oxide layer, such as the PTEOS layer  200   b,  the first silicon oxynitride pattern  410   a  is over-etched using the PTEOS layer  200   b  as an etch stopping layer. Since the etch selectivity between the PTEOS layer  200   b  and each of the first photoresist pattern  610   a  and the first anti-reflection pattern  510   a  is very high, the PTEOS layer  200   b  is not damaged if exposed when the first photoresist pattern  610   a  and the first anti-reflection pattern  510   a  are removed after forming the first silicon oxy-nitride pattern  410   a.    
         [0073]     Referring to  FIG. 32 , the first photoresist pattern  610   a  and the first anti-reflection pattern  510   a  disposed on the first silicon oxynitride pattern  410   a  are removed using a conventional ashing and stripping process, for example.  
         [0074]     Referring to  FIG. 33 , a second anti-reflection layer  520   a  and a second photoresist layer  620   a  are formed on the first silicon oxynitride pattern  410   a.  Since the second anti-reflection layer  520   a  is substantially flatly formed on the embossed portions of the first silicon oxynitride pattern  410   a,  the second photoresist layer  620   a  can be favorably formed (e.g., substantially flatly formed).  
         [0075]     Referring to  FIG. 34 , a second photoresist pattern  630   a  is formed by exposing and developing the second photoresist layer  620   a  using the second photo mask  720 , as in  FIG. 19 . The second photoresist pattern  630   a  is formed to expose engraved portions of the etch target pattern  110   a,  in addition to the engraved portions formed by the first photoresist pattern  610   a.    
         [0076]     Referring to  FIG. 35 , a second anti-reflection pattern  530   a  is formed by etching the second anti-reflection layer  520   a  using the second photoresist pattern  630   a  as an etch mask. The etching can be an anisotropic dry etching, for example, dry etching using plasma, reactive ion etching, etc., as mentioned above.  
         [0077]     Referring to  FIG. 36 , a second, and in this embodiment final, silicon oxynitride pattern  420   a  is formed in the silicon oxynitride layer  400   a  by etching the first silicon oxynitride pattern  410   a  (see  FIG. 32 ) using the second photoresist pattern  630   a  and the second anti-reflection pattern  530   a  as an etch mask. The embossed portions of the first silicon oxynitride pattern  410   a  are exposed by the second photoresist pattern  630   a  and etched to define other engraved portions of the silicon oxynitride layer  400   a,  in addition to the engraved portions formed by the first photoresist pattern  610   a.  As a result, the final silicon oxynitride pattern  420   a  has the same image as the etch target pattern  110 a in be formed in  FIG. 42 .  
         [0078]     In addition, the final silicon oxynitride pattern  420   a  is etched using the PTEOS layer  200   b  disposed under the final silicon oxynitride pattern  420   a  as an etch stopping layer. As described with reference to  FIG. 31 , since the etch selectivity between the PTEOS layer  200   b  and each of the second photoresist pattern  630   a  and the second anti-reflection pattern  530   a  is very high, the PTEOS layer  200   b  is not damaged if exposed when the second photoresist pattern  630   a  and the second anti-reflection pattern  530   a  are removed after forming the final silicon oxynitride pattern  420   a.    
         [0079]     As described above, since over-etching can be performed when forming the final silicon oxynitride pattern  420   a,  due to the sufficient etch selectivities between the layers, the pattern shape can be ensured and the occurrence of bridges in the pattern and the consequent decrease in the process margin can be prevented.  
         [0080]     Referring to  FIG. 37 , the second photoresist pattern  630   a  and the second anti-reflection pattern  530   a  disposed on the final silicon oxynitride pattern  420   a  are removed, for example, using a conventional ashing and stripping process. In doing so, the final silicon oxynitride pattern  420   a  is exposed.  
         [0081]     Referring to  FIG. 38 , a PTEOS pattern  210   b  is formed by etching the PTEOS layer  200   b  using the final silicon oxynitride pattern  420   a  as an etch mask. The final silicon oxynitride pattern  420   a,  used as a hard mask for forming the PTEOS pattern  210   b,  can partially remain on the PTEOS pattern  210   b  when formation of the PTEOS pattern  210   b  is finished.  
         [0082]     Referring to  FIG. 39 , an amorphous carbon pattern  310   a  is formed by etching the amorphous carbon layer  300   a  using PTEOS pattern  210   b  as an etch mask. The final silicon oxynitride pattern  420   a  can be used with the PTEOS pattern  210   b  to etch the amorphous carbon layer  300   a,  or can be removed before forming the amorphous carbon pattern  310   a.  The PTEOS pattern  210   b,  used as a hard mask for forming the amorphous carbon pattern  310   a,  can partially remain on the amorphous carbon pattern  310   a  when formation of the amorphous carbon pattern  310   a  is finished.  
         [0083]     Referring to  FIG. 40 , an oxide pattern  210   a  is formed by etching the oxide layer  200   a  using the amorphous carbon pattern  310   a  as an etch mask. The PTEOS pattern  210   b  can be used with the amorphous carbon pattern  310   a  to etch the oxide layer  200   a,  or can be removed before forming the oxide pattern  210   a.  The amorphous carbon pattern  310   a,  used as a hard mask for forming the oxide pattern  210   a,  can partially remain on the oxide pattern  210   a  when formation of the oxide pattern  210   a  is finished.  
         [0084]     Referring to  FIG. 41 , an etch target pattern  110   a  can be formed by etching the etch target layer  100   a  using the oxide pattern  210   a  as an etch mask. At this time, the amorphous carbon pattern  310   a  can be used with the oxide pattern  210   a  to etch the etch target layer  100   a,  or can be removed before forming the etch target pattern  110   a.  The oxide pattern  210   a,  used as a hard mask for forming the etch target pattern  110   a,  can partially remain on the etch target pattern  110   a  when formation of the etch target pattern  110   a  is finished.  
         [0085]     Referring to  FIG. 42 , the oxide pattern  210   a  disposed on the etch target pattern  110   a  is removed.  
         [0086]     According to the present disclosure, an anti-reflection layer can be formed flatly on a silicon oxynitride pattern having engraved portions and embossed portions, and a photoresist pattern can subsequently be substantially flatly formed on the silicon oxyntride pattern. As a result, the risk of defects in micro-patterns ultimately formed in the target layer are mitigated.  
         [0087]     In the embodiments above, photoresist patterns can be formed using any known or hereafter developed light sources. As an example, an ArF eximer laser having a wavelength of 193 nm can be used as an exposure light source to form the first photoresist pattern and the second photoresist pattern discussed above. Thus, micro-patterns with a critical dimension of less than 60 nm can be formed in a semiconductor device, as an example. Dimensions greater than 60 nm can also be attained, if desirable.  
         [0088]     While aspects of the present invention have been particularly shown and described with reference to the above exemplary embodiments, it will be understood by those of ordinary skill in the art that various changes in form and details can be made therein without departing from the spirit and scope of the present disclosure and invention. It is intended, therefore, by the following claims to claim that which is literally described and all equivalents thereto, including all modifications and variations that fall within the scope of each claim.