Abstract:
A mask according to embodiments includes a substrate and a phase delay material layer formed over the substrate. At least one mask pattern including a hole pattern may be formed on the phase delay material layer, the hole pattern allowing light to pass through the mask pattern. Assist patterns compensate for constructive interference of the light occurring between the mask patterns. Embodiments may prevent sidelobes from occurring by inserting an assist pattern into a mask, so that defects in semiconductor devices can be prevented.

Description:
[0001]    The present application claims priority under 35 U.S.C. 119 to Korean Patent Application No. 10-2007-0072639 (filed on Jul. 20, 2007), which is hereby incorporated by reference in its entirety. 
       BACKGROUND 
       [0002]    Photolithography processes are essential for manufacturing semiconductor devices. In a photolithography process, after coating a relatively uniform photoresist layer over a wafer, the wafer is subject to an exposure process using a photomask having a predetermined layout. Then the exposed photoresist layer is developed to form a pattern having a predetermined shape. 
         [0003]    In semiconductor photolithography technologies used for manufacturing semiconductor devices, a mask may be precisely designed such that the amount of light passing through the mask can be precisely adjusted. As semiconductor devices have become more highly integrated, design rules for smaller scale devices have been introduced. At smaller scales, sidelobes may occur between adjacent patterns due to constructive interference of light. 
         [0004]      FIG. 1A  is a plan view illustrating a part of a related mask,  FIG. 1B  is a view illustrating an aerial image of light passing through the mask of  FIG. 1A , and  FIG. 1C  is a view illustrating patterns formed using the mask of  FIG. 1A . As shown in  FIG. 1A , the related mask  10  has mask patterns  11 , such as hole patterns or blocking patterns, corresponding to photoresist patterns to be formed. When mask  10  includes hole patterns  11 , as shown in  FIG. 1B , sidelobe  23  may occur in the aerial image of light, which passes through mask patterns  11 , due to constructive interference of light. As shown in  FIG. 1C , an undesired sidelobe pattern  33  may be generated between the photoresist patterns  31  to be formed over a substrate  30  through the mask  10 . Thus, when the photoresist patterns  31  are etched using the mask  10 , an undesirable result may be generated by the sidelobe pattern  33  on the substrate  30 . 
       SUMMARY 
       [0005]    Embodiments relate to a mask capable of preventing sidelobes from being formed in a photoresist pattern used for forming a semiconductor device, and a manufacturing method thereof. A mask according to embodiments includes a substrate and a phase delay material layer formed over the substrate. At least one mask pattern including a hole pattern may be formed on the phase delay material layer, the hole pattern allowing light to pass through the mask pattern. Assist patterns compensate for constructive interference of the light occurring between the mask patterns. 
         [0006]    A method for manufacturing a mask according to embodiments includes preparing a base substrate and forming a phase delay material layer over the base substrate. The method includes forming at least one mask pattern including a first hole pattern, which allows light to pass through the hole pattern, by patterning the phase delay material layer. The method includes forming at least one assist pattern including a second hole pattern located between the mask patterns, thereby compensating for constructive interference of the light between portions of the first hole pattern. 
         [0007]    A phase shift mask having a light phase delay part and light transmitting parts according to embodiments includes at least one hole pattern formed on a light phase delay part between the light transmitting parts in a phase shift mask, the hole pattern causing destructive interference of a portion of the light passing through the light transmitting parts. 
         [0008]    Embodiments can prevent undesirable sidelobes, which may be formed in a dense photoresist pattern, from occurring, so that desirable patterns may be formed. Embodiments may prevent sidelobes from occurring by inserting an assist pattern into a mask, so that defects in semiconductor devices can be prevented. 
     
    
     
       DRAWINGS 
         [0009]      FIG. 1A  is a plan view illustrating a part of a related mask. 
           [0010]      FIG. 1B  is a view illustrating an aerial image of light passing through the mask of  FIG. 1A . 
           [0011]      FIG. 1C  is a view illustrating patterns formed using the mask of  FIG. 1A . 
           [0012]      FIG. 2  is a sectional view illustrating a mask according to embodiments. 
           [0013]      FIG. 3A  is a sectional view illustrating a pattern formed using the mask of  FIG. 2  according to embodiments. 
           [0014]      FIG. 3B  is a sectional view illustrating a pattern formed using the mask of  FIG. 2  according to embodiments. 
           [0015]      FIG. 4A  is a plan view illustrating a part of a mask according to embodiments. 
           [0016]      FIG. 4B  is a view illustrating an aerial image of light passing through the mask of  FIG. 4A . 
           [0017]      FIG. 4C  is a view illustrating a pattern formed using the mask of  FIG. 4A . 
           [0018]      FIG. 5A  is a plan view illustrating a mask according to embodiments. 
           [0019]      FIG. 5B  is a plan view illustrating a comparison mask compared with a mask according to embodiments. 
           [0020]      FIG. 6  is a graph illustrating intensity of light, which passes through the mask of  FIGS. 5A and 5B , as a function of positions “a-b” of the mask. 
       
    
    
     DESCRIPTION 
       [0021]    Hereinafter, a mask and a manufacturing method thereof according to embodiments will be described with reference to the accompanying drawings.  FIG. 2  is a sectional view illustrating a mask according to embodiments.  FIG. 3A  is a sectional view illustrating a pattern formed using the mask of  FIG. 2  according to embodiments. and  FIG. 3B  is a sectional view illustrating a pattern formed using the mask of  FIG. 2  according to embodiments. As shown in  FIG. 2 , the mask  100  according to embodiments includes a base substrate  110 , mask patterns  111  and assist patterns  121 . The mask patterns  111  and the assist patterns  121  may be formed on a base substrate  110 . The mask  100  may include a PSM (Phase Shift Mask). The mask pattern  111  may include a hole pattern or a blocking pattern. 
         [0022]    Referring to  FIG. 2 , the mask pattern  111  includes a hole pattern to serve as a light transmitting part. A peripheral area of the mask pattern  111  may serve as a light phase delay part. The light phase delay part may include a phase delay material layer. The phase delay material layer may be a compound, for example, compounds containing transition metals. The transition metal may include one selected from the group consisting of Cr, Mo, Hf, W, Pt, Co, Ni, Ta and Ti. Further, the compound including the transition metal may include Si. 
         [0023]    The assist pattern  121  prevents one or more sidelobes which may occur due to constructive interference generated between the mask patterns  111 . The assist pattern  121  may cause destructive interference, which compensates for the constructive interference, by allowing light to pass through a place where the sidelobe occurs. When the mask pattern  111  includes a hole pattern, the assist pattern  121  may be formed with a hole pattern. Further, when the mask pattern  111  includes a blocking pattern, the assist pattern  121  may be formed with a blocking pattern. The assist pattern  121  may have a size corresponding to 20% to 60% of that of the mask pattern  111 . Further, an interval between the assist patterns  121  may correspond to 50% to 200% of the size of the assist pattern  121 . 
         [0024]    An arrangement interval of the mask patterns  111  may be larger than a width of the mask pattern  111  by one to ten times. The assist pattern  121  may have a circular or polygonal shape. Further, by way of example, the assist pattern  121  may also have a triangular, rectangular or pentagonal shape. The assist pattern  121  may include slits. In other words, the assist pattern  121  may have various shapes which may effectively remove the sidelobe(s). 
         [0025]    As shown in  FIGS. 3A and 3B , when the photolithography process is performed using the mask  100 , good photoresist patterns  131  can be formed over the substrate  130 .  FIG. 3A  is a sectional view illustrating a mask when positive photoresist is used and  FIG. 3B  is a sectional view illustrating the mask when negative photoresist is used. Since destructive interference occurs in the mask due to the assist pattern  121  formed between the mask patterns  111 , a sidelobe pattern is not generated between the photoresist patterns  131  formed by the mask patterns  111 . 
         [0026]      FIG. 4A  is a plan view illustrating a part of the mask according to embodiments.  FIG. 4B  is a view illustrating an aerial image of light passing through the mask of  FIG. 4A .  FIG. 4C  is a view illustrating a pattern formed using the mask of  FIG. 4A . As shown in  FIG. 4A , the mask  100  according to embodiments includes mask patterns  111 , such as hole patterns or blocking patterns, corresponding to the photoresist pattern  131  to be formed. Further, the mask  100  includes the assist pattern  121  between the mask patterns  111 . Light diffraction may occur when the light passes through the assist pattern  121 , so that destructive interference of light may occur. 
         [0027]    As shown in  FIG. 4B , in view of the aerial image of light passing through the mask patterns  111  and the assist patterns  121 , the light passes through the mask patterns  111 , but the light forms a minimal image  123  corresponding to the assist patterns  121  due to the destructive interference of light. Thus, as shown in  FIG. 4C , an undesirable sidelobe pattern, except for patterns formed by the mask patterns  111 , is not formed between the photoresist patterns  131  formed over the substrate  130  through the mask  100 . 
         [0028]      FIG. 5A  is a plan view illustrating the mask according to embodiments.  FIG. 5B  is a plan view illustrating a comparison mask compared with the mask according to embodiments.  FIG. 6  is a graph illustrating the intensity of light, which passes through the mask of  FIGS. 5A and 5B , as a function of positions along the line shown between points “a” and “b” on the masks. As shown in  FIG. 5A , the mask  100  according to embodiments includes mask patterns  111  formed with hole patterns and the assist patterns  121 . As shown in  FIG. 5B , the comparison mask  200  includes comparison mask patterns  211  identical to the mask patterns  111  of the mask  100  according to embodiments, and does not include assist patterns. 
         [0029]    The graphs with curves indicated by P and Q in  FIG. 6  can be obtained by measuring the intensity of light passing through the mask  100  and the comparison mask  200 , respectively. As shown on curve P of the mask  100 , the maximum intensity of light is obtained at the position corresponding to the mask patterns  111 , and intensity of light is lowered at the position P′ corresponding to the assist patterns  121  due to the destructive interference of the light. As shown on curve Q of the comparison mask  200 , the maximum intensity of light is obtained at the position corresponding to the comparison mask patterns  211 , and a relatively lower local maximum intensity of light is obtained by the constructive interference of the light at the position Q′ corresponding to the mask between the comparison mask patterns  211 . 
         [0030]    In view of photoresist corresponding to the comparison mask  200 , light does not physically pass through the mask between the comparison mask patterns  211 . From an optical point of view, a sufficient amount of light is irradiated onto the photoresist, so that an undesirable sidelobe pattern may be formed over the substrate. However, in view of photoresist corresponding to the mask  100  according to embodiments, light physically passes through the assist patterns  121 . From an optical point of view, destructive interference occurs when the light passes through the assist patterns  121 , so that the sidelobe pattern is not formed on the photoresist. Consequently, only desired patterns may be formed over the substrate. 
         [0031]    It will be obvious and apparent to those skilled in the art that various modifications and variations can be made in the embodiments disclosed. Thus, it is intended that the disclosed embodiments cover the obvious and apparent modifications and variations, provided that they are within the scope of the appended claims and their equivalents.