Abstract:
In a method of forming a dense contact-hole pattern in a semiconductor device, the method uses a self-align double patterning technique including forming a square or triangular lattice dot pattern on double layers of mask materials, forming first holes in the upper mask material and second holes wider than the first holes in the lower mask material by double patterning, additionally forming an insulating layer to a thickness such that the first holes are closed such that voids are left in the second holes, and transferring the shape of the voids to a base layer. The hole pattern formed thereby has a high precision, with a density thereof being double or triple that of a pattern formed by a lithography technique.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates, in general, to a method of manufacturing a semiconductor device and, more particularly, to a method of forming a densely-packed contact-hole pattern in a semiconductor device. 
         [0003]    2. Description of the Related Art 
         [0004]    In response to the miniaturization of semiconductor devices, it becomes more difficult to form microscopic patterns by lithography techniques. For this, there are self-align double pattern techniques, in which the line pitch can be halved by forming spacers on a sidewall, which has a pattern achievable by a lithography technique, followed by processing using the spacer as a mask (JP 2008-27978 A, and JP 2008-91925 A). In addition, there is a self-align double patterning technique devised by applying the above techniques to a dense contact-hole pattern. In the fourth example of JP 2008-91925 A, there is disclosed a method forming a column of rectangular contact-holes, which has a half pitch of a column of initial rectangular patterns (first hard mask patterns). 
         [0005]    However, in such techniques, the size of the gap formed between the spacers varies depending on the size of the initial pattern. Therefore, there is a problem in that it is difficult to set the gap size to be uniform. In addition, in the case of intending to form more densely-packed holes, that is, to form a capacitor in a dense pattern, such as 6F2 type, in a semiconductor memory device such as Dynamic Random Access Memory (DRAM), the shapes of the resultant holes are classified into two types, including a shape to which the initial pattern shape is reflected and a shape to which the spacer gap shape is reflected. 
       SUMMARY 
       [0006]    The present invention provides a technique of forming densely-packed contact-hole patterns in a semiconductor device, and more particularly, a method of manufacturing a semiconductor device, in which a high-precision hole pattern is formed by a self-align double patterning technique, at a density (number) that is double or triple that of a pattern achievable by lithography techniques. 
         [0007]    In an embodiment of the present invention, the method of manufacturing a semiconductor device includes the processes of: 
         [0008]    sequentially forming mask material layers A and B on a base layer; 
         [0009]    forming a plurality of dotted photoresist patterns in a square or triangular lattice layout on the mask material layer B; 
         [0010]    forming a first insulating film, which is intended to form sidewall spacers, on the whole surfaces, with a recess left at least in the vicinity of a central portion of each square or triangular lattice of the dotted photoresist patterns; 
         [0011]    etching back the first insulating film by dry etching to expose the photoresist, removing the photoresist that is exposed and forming the sidewall spacers by further etching back, wherein the sidewall spacers have a photoresist-removed portion that exposes the mask material layer B and a first hole pattern corresponding to the recess; 
         [0012]    etching the mask material layer B using the sidewall spacers as a mask to form second holes corresponding to the first hole pattern in the mask material layer B; 
         [0013]    etching the mask material layer A using the remained mask material layer B as a mask to form third holes in the mask material layer A by, wherein the third holes have a diameter greater than that of the second holes of the mask material layer B; 
         [0014]    forming a second insulating layer on the mask material layer B to a thickness such that openings of the second holes are closed to form voids in the third holes of the mask material layer A; 
         [0015]    forming a mask pattern exposing the base film in fourth holes corresponding to the voids in the third holes by dry etching; and forming holes corresponding to the fourth holes by etching the base layer using the mask pattern as a mask. 
         [0016]    According to embodiments of the invention, it is possible to form a uniform hole pattern having a diameter smaller than that of the initial dotted photoresist pattern, with the number (density) of the holes being double or triple that of the dotted photoresist pattern in a predetermined area. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The above features and advantages of the present invention will be more apparent from the following description of certain preferred embodiments taken in conjunction with the accompanying drawings, in which: 
           [0018]      FIGS. 1A to 8B  are views showing a process of manufacturing a semiconductor device according to an embodiment of the invention, in which  FIGS. 1A ,  2 A,  3 A,  4 A,  5 A,  6 A,  7 A, and  8 A are plan views, and  FIGS. 1B ,  2 B,  3 B,  4 B,  5 B,  6 B,  7 B, and  8 B are cross-sectional views. 
           [0019]      FIGS. 9A and 9B  are views showing a method of manufacturing a semiconductor device according to an embodiment of the invention, in which  FIG. 9A  is a plan view showing a state in which a dotted photoresist pattern is arranged in a square lattice layout, and  FIG. 9B  is a plan view showing a state in which a hole pattern is formed in the square lattice layout shown in  FIG. 9A  according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    The invention will be now described herein with reference to illustrative embodiments. Those skilled in the art will recognize that many alternative embodiments can be accomplished using the teachings of the present invention and that the invention is not limited to the embodiments illustrated for explanatory purpose. 
         [0021]    A fabrication method according to an embodiment of the invention is described with reference to  FIGS. 1A to 8B .  FIGS. 1A ,  2 A,  3 A,  4 A,  5 A,  6 A,  7 A, and  8 A, which are plan views, and  FIGS. 1B ,  2 B,  3 B,  4 B,  5 B,  6 B,  7 B, and  8 B, which are cross-sectional views taken along line A-B in  FIGS. 1A ,  2 A,  3 A,  4 A,  5 A,  6 A,  7 A, and  8 A, respectively. 
         [0022]    Referring to  FIGS. 1A and 1B , amorphous carbon film  1  and silicon oxynitride film  2  are formed on a semiconductor substrate (not shown) as base layers in which holes are intended to be formed. Afterwards, organic antireflection film  3 , which will serve as a mask material layer A, and silicon-containing organic film  4 , which will serve as a mask material layer B are formed, and photoresist  5  is formed on silicon-containing organic film  4  by a spin coating process. Photoresist  5  is patterned through exposure and development by a photolithography technique, so that dotted patterns  6  are formed in AREA  1 , in which holes are intended to be formed, and dummy patterns are formed in AREA  2 , in which the holes are not intended to be formed. For example, the dummy patterns include dummy line pattern  7  and dummy rectangular pattern  8 . In this example, the diameter of the dotted pattern is set to be 40 nm that is a resolution limit F value of the photolithography technique, the width of the dummy line pattern is set to be 100 nm, and the dummy rectangular pattern is set to be a square pattern with a side thereof being 500 nm. Dotted patterns  6  are arranged to be a triangular lattice layout (pitch C: 100 nm), as shown in the figures. Meanwhile, in the plan views of  FIGS. 1A ,  2 A,  3 A,  4 A,  5 A,  6 A,  7 A, and  8 A, the scales in AREA  1  and AREA  2  are not equal. The dummy pattern is not limited to the line pattern and the rectangular pattern as described above. It is preferred that the size of the dummy pattern be the same as or greater than the pitch of the dotted patterns, and that the dummy pattern be formed in a position that is distanced from the dotted patterns at an interval greater than the pitch of the dotted patterns. 
         [0023]    Referring to  FIGS. 2A and 2B , silicon dioxide film  9  is formed as a first layer, which will form sidewall spacers, by Atomic Layer Deposition-Chemical Vapor Deposition (ALD-CVD), to a thickness such that the dotted patterns forming the triangular lattice layout in the pitch direction is correctly filled. Here, silicon dioxide film  9  is formed in 30 nm thickness. Consequently, in AREA  1 , silicon dioxide film  9  is connected in the direction of each edge of the triangular lattices, whereas substantially triangular recesses  9 B are formed in the vicinity of the central portion of each triangular lattice. Recesses  9 A are also formed between the dotted pattern and the dummy line pattern and between the dummy line pattern and the dummy rectangular pattern. 
         [0024]    Referring to  FIGS. 3A and 3B , silicon dioxide film  9  is etched back to expose the photoresist  5  and then the exposed photoresist  5  is removed by a dry etching technique using oxygen gas. Sidewall spacers  10  are formed by additionally etching back silicon dioxide film  9  until silicon-containing organic film  4  is exposed. In sidewall spacers  10 , openings  10 C are formed by the removal of photoresist  5 , and openings  10 A and  10 B corresponding to recesses  9 A and  9 B are formed. In AREA  1 , openings  10 C, which are formed by removing the dotted photoresist, and openings  10 B corresponding to recesses  9 B (which are collectively referred to as a “first hole pattern”) are formed. 
         [0025]    Referring to  FIGS. 4A and 4B , silicon-containing organic film  4  and organic antireflection film  3  are sequentially dry etched using sidewall spacers  10  as a mask. Here, by the use of a mixed gas of CF 4 , CHF 3 , CH 2 F 2 , Ar, and O 2  as an etching gas of silicon-containing organic film  4 , silicon-containing organic film  4  is anisotropically and isotropically etched, etching sidewall spacers  10 , thereby forming second holes  4 B and  4 C in the first hole pattern area (openings  10 B and  10 C). By the anisotropic and isotropic etching of silicon-containing organic film  4 , second holes  4 B under the substantially triangular openings  10 B become slightly similar to a circular shape. In addition, organic antireflection film  3  is isotropically etched using a mixed gas of O 2 , CO, N 2 , and H 2  as an etching gas, such that it is side-etched to about 10 nm from the pattern formed in silicon-containing organic film  4 . Third holes  3 B and  3 C, which have a substantially circular planar shape, are formed in organic antireflection film  3  under second holes  4 B and  4 C. The diameters of third holes  3 B and  3 C are enlarged about 20 nm from those of second holes  4 B and  4 C, respectively. 
         [0026]    Referring to  FIGS. 5A and 5B , second holes  4 B and  4 C are closed by growing a silicon dioxide film  11 , which serves as the second layer, to be 30 nm thickness using ALD-CVD. Here, since the diameters of third holes  3 B and  3 C, which are formed in organic antireflection film  3 , are greater than those of second holes  4 B and  4 C, which are formed in silicon-containing organic film  4 , respectively, voids  11 B having a diameter of about 20 nm are formed. Here, voids  11 A are also formed in AREA  2 . Consequently, a layout having recesses  11 D, which are not completely closed, is formed. 
         [0027]    Referring to  FIGS. 6A and 6B , organic antireflection film  12  is formed by a spin coating technique, such that organic antireflection film  12  fills voids  11 A in AREA  2  by detouring through recesses  11 D without filling voids  11 B in AREA  1 . 
         [0028]    Referring to  FIGS. 7A and 7B , fourth hole pattern  13  corresponding to voids  11 B is formed by etching back organic antireflection film  12  and silicon oxide film  11  by a dry etching technique. 
         [0029]    Referring to  FIGS. 8A and 8B , holes  14  having a diameter smaller than the lithography limit, with the density thereof being triple that of the first pattern, can be formed by processing silicon oxynitride film  2  using silicon oxide film  11  and organic antireflection films  3  and  12  as a mask and processing amorphous carbon film  1  using silicon oxynitride film  2  as a mask. 
         [0030]      FIG. 9A  is a plan view showing a state in which dotted photoresist patterns are arranged in a square lattice layout, and  FIG. 9B  is a plan view showing a state in which hole patterns are formed in the square lattice layout shown in  FIG. 9A  according to the present invention. By the arrangement of the dotted pattern in the square lattice layout, holes can be formed, with a uniform diameter that is smaller than the lithography limit, and at a density that is double that of the initial arrangement. 
         [0031]    The above-described example illustrated a configuration in which the voids in AREA  2  are buried with the organic antireflection film by forming the organic antireflection film by a spin coating technique in the process of  FIGS. 6A and 6B . However, in the present invention, the holes may be formed in AREA  1  as described above by directly performing an etching back process in AREA  2  after the process of  FIGS. 5A and 5B , such that the fourth hole pattern corresponding to the voids are exposed, and covering AREA  2  with a photoresist. However, in this case, the photolithography process for patterning the photoresist increases. Therefore, it is preferred that the voids in AREA  2  be disposed in advance using an organic antireflection film as in the foregoing example. 
         [0032]    Applications of the present invention may include a semiconductor device, such as DRAM, which is used in an data storage device. In an example, the application of the present invention to contact holes in a cell array of a DRAM semiconductor device makes it possible to stably form DRAM having a dense patterned capacitor, such as 6F2 type.