Patent Document

CROSS REFERENCES TO RELATED APPLICATIONS 
   The present application is a continuation of U.S. application Ser. No. 10/154,237, filed on May 23, 2002, now U.S. Pat. No. 6,716,747, which claims priority from Japanese Application No. 2001-153326, filed on May 23, 2001, both of which are hereby incorporated by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a manufacturing method for a semiconductor apparatus, and in detail, the present invention particularly relates to such a manufacturing method for a semiconductor apparatus, wherein a micro wiring pattern is formed. 
   2. Description of the Related Art 
   In recent years, the miniaturization of a wiring pattern has been quickly advanced in order to improve the degree of integration and the property of an LSI. The techniques for miniaturizing a gate length in order to improve the property of a transistor and for opening a contact hole smaller than that of a conventional contact hole in order to improve the degree of integration have been strongly requested. It is well known that a limit resolution (R) in an optical lithography process to determine the minimum size of the LSI is represented by the following equation (1):
 
 R=k×λ/NA   (1)
 
   In this case, λ is a wave-length of a light source, NA is the numerical aperture in a projection lens, and k is a constant having a value of about 0.5. 
   That is, in order to attain the lithography process having a resolution higher than that of the conventional one, it is desirable to select a light source having a shorter wave length. Because of this reason, a photolithography machine, which uses a krypton fluorine (KrF) excimer laser having a wave-length of 248 nm as a light source, is used in a field of manufacturing an high technology device. However, NA of a current exposing apparatus is 0.68 at its maximum. Thus, even the latest KrF excimer laser photolithography machine has only a resolution of about 0.18 μm. However, the resolution derived from the equation (1) is applied to a banded pattern typically referred to as a line and space. Then, the resolution of the contact hole pattern has a limit of about 0.22 μm. 
   On the other hand, a technique for opening a micro contact hole having a diameter of 0.15 μm is requested in a device of 0.13 μm generation. This is the size that can not be easily attained even by using an argon fluorine (ArF) excimer laser photolithography machine, which is expected as a next generation photolithography machine using a light source having a wave length of 193 nm. 
   As one method of solving this problem, a technique for carrying out an etching process so as to give a taper to a side wall of a hole  112  formed on a film  111  to be processed by using a resist mask  121  is known and thereby finishing it to a desired hole diameter at a bottom  112   b  of the hole  112 , as shown in FIG.  3 . 
   However, as shown in  FIG. 4 , in the above-mentioned conventional method, even if a desired hole diameter (a hole diameter on design) Db is obtained at the bottom  112   b  of the hole  112 , a diameter Dt at an upper end (aperture)  112   t  of the hole  112  becomes greater than the desired size (a size on the design). This results in a problem that a sufficient matching margin can not be obtained at a later lithography process. For example, this has a problem that a distance d from a wiring  13 I placed adjacently to the hole  112  is made narrower. 
   The present invention is a manufacturing method for a semiconductor apparatus proposed in order to solve the above-mentioned problems. 
   SUMMARY OF THE INVENTION 
   The manufacturing method of a semiconductor apparatus of the present invention includes the steps of: forming a mask material film made of organic insulation film on a film to be processed; forming a tapered opening pattern or aperture pattern, in which a bottom is narrower than an open side on the mask material film; and etching the film to be processed using the mask material film as a mask. 
   In accordance with the manufacturing method of the semiconductor apparatus, after the mask material film is formed on the film to be processed, the tapered aperture pattern that is narrower at the bottom side than at the aperture side is formed on the film to be processed, and thereby it is possible to able to form the bottom of the aperture pattern at the desired micro dimension exceeding the limit of the lithography technology. The film to be processed is then etched by applying thus-processed mask material film as a mask, thereby, the film to be processed can be vertically etched to the micro dimension exceeding the limit of the lithography technology. 
   As mentioned above, according to the manufacturing method of the semiconductor apparatus of the present invention, after the mask material film is formed on the film to be processed, the tapered aperture pattern in which the bottom is narrower than the aperture side is formed on this mask material film. Thus, the bottom of the aperture pattern can be formed at the desirable micro dimension exceeding the limit of the lithography technique. The thus-processed mask material film is used as the mask, and the film to be processed is etched. Hence, the film to be processed can be vertically etched to the micro dimension exceeding the limit of the lithography technique. Therefore, since the film to be processed can be processed under the excellently controlling performance with regard to the size, the matching margin is never decreased differently from the conventional direct taper etching method. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1A  to  1 E are sectional views of manufacturing steps showing an embodiment according to a manufacturing method for a semiconductor apparatus according to the present invention; 
       FIG. 2  is a sectional view of a schematic configuration for describing a case in which a film to be processed has a step; 
       FIG. 3  is a sectional view of a schematic configuration for describing a conventional technique; and 
       FIG. 4  is a sectional view of a schematic configuration for describing a problem. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   One embodiment of a manufacturing method for a semiconductor apparatus according to the present invention will be described below with reference to a sectional view of manufacturing steps of  FIGS. 1A  to  1 E. 
   As shown in  FIG. 1A , a film  12  to be processed made of, for example, silicon oxide film is formed on a substrate  11 . Next, a first mask material film (mask material film)  13  made of an organic insulation film is formed on the film  12  to be processed. A dielectric film having low dielectric constant is used as this organic insulation film. The material referred to as the low dielectric film is the material having a lower dielectric constant than that of SiO 2 , and is originally developed in order to reduce an inter-wiring capacitance of an LSI. For example, FLARE made by Honeywell Co., Ltd., SILK made by Dow Chemical Ltd. and the like are known as such material. Those organic system materials have a high heatproof temperature of 350° C. Thus, they can be positively used even as a hard mask material in a process for manufacturing a semiconductor. Hence, they can be used to form a micro hole pattern. 
   Moreover, a second mask material film  14 , which serves as an etching mask to this first mask material film  13  and is made of, for example, an oxide film, is formed on the first mask material film  13 . Moreover, a resist film  15  is formed on the second mask material film  14 . The mask material film  14  is made of, for example, a silicon oxide film. With regard to this silicon oxide film, if it is the silicon oxide film serving as the etching mask to the first mask material film  13 , a silicon oxide film formed by a chemical vapor deposition, a silicon oxide film of a coating type such as SOG film and the like can be used, and accordingly the film forming method is not specified. As mentioned above, the low dielectric film has the high heatproof property although it is the organic film. Thus, it can be sufficiently endured in the process for forming the mask material film  14  made of the oxide film by using the chemical vapor deposition. 
   Then, as shown in  FIG. 1B , the usual lithography process is carried out under this condition, and an aperture pattern  16  is formed on the resist film  15 . As mentioned above, the formable pattern size at this time is limited by the limit resolution of the lithography technique. If the defect of the lithography process causes a line width and a positional deviation to depart from a range of a specification, it is possible to apply a reproducing process through a usual resist ashing. Even if a resist reproducing process is carried out, the second mask material film  14  is formed on the low dielectric film. Thus, the low dielectric film is protected by this second mask material film  14 . Hence, the low dielectric film is never ashed in carrying out the reproducing process. 
   When the lithography process is completed without any trouble, the resist film  15  on which the aperture pattern  16  is formed is used as the mask, and the second mask material film  14  is etched to thereby form an aperture pattern  17 . 
   Next, as shown in  FIG. 1C , the resist film  15  is used as the etching mask, and the first mask material film  13  made of the low dielectric film is etched. This etching is done such that in an open pattern  18  formed on the first mask material film  13 , a bottom side is narrower than an aperture side, and its side-wall becomes taper-shaped. Actually, the taper etching can be carried out by setting a temperature of the substrate to a low temperature (for example, −50° C. to 0° C.). 
   Usually, the deposition reaction and the etching reaction are mixed in an etching chamber. The deposition reaction is easily carried out by lowering the temperature of the substrate. Thus, it is possible to process the taper shape. Ammonia (NH 3 ), mixed gas of hydrogen (H x ) and nitrogen (N 2 ), oxygen (O 2 ) and the like are used as the etching gas for the low dielectric film. In addition, a method of etching the organic insulation film to the taper shape in an excellently controlling manner is disclosed in Japanese Patent Publication No.H7-27886. According to this method, an aperture having a desirable taper angle can be formed, for example, by changing a content of phloro-carbon gas in the etching gas. 
   In the above-mentioned etching process, when the first mask material film  13  is etched, the resist film  15  is also etched and removed. Then, when the resist film  15  is perfectly removed, the second mask material film  14  serves as the etching mask, and the etching is further advanced. 
   Next, as shown in  FIG. 1D , the first mask material film  13  is used as the etching mask, and the usual etching for the vertical processing is carried out. Consequently, an aperture pattern  19 , which is further miniaturized over the size formed by the lithography process, is formed on the film  12  to be processed. In the etching at this time, the second mask material film  14  [refer to FIG.  1 C] formed on the upper layer is desired to be formed in advance at a film thickness to be etched simultaneously with the film  12  to be processed. 
   After that, as shown in  FIG. 1E , the first mask material film  13  made of the low dielectric film that is already unnecessary [refer to FIG.  1 D] is removed by carrying out the ashing process similar to the resist removal. As a result, the aperture pattern  19  less than the resolution limit of the lithography technique can be formed on the film  12  to be processed. 
   As compared with the method of reducing the hole diameter (or the slit width) at the bottom by performing the taper etching on the film itself to be processed that is typically used, the method of the present invention can carry out the vertical processing of the film  12  to be processed. Thus, for example, when the aperture pattern  19  is the hole pattern, its control of the hole diameter thereof becomes easy. The problem of the lack of the matching margin as described in the problem is never induced. Also, as shown in  FIG. 2 , when the film  12  to be processed has a step S, the first mask material film  13  can function as a flattened layer. Thus, this method has the merit that the lithography step is advantageous. 
   When the above-mentioned manufacturing method is used to form the contact hole pattern, as the example, the lithography process is carried out to thereby form the aperture pattern  16  composed of the contact hole pattern having the diameter of 0.22 μm on the resist film  15 . Then, for the first mask material film  13  made of the low dielectric film, the taper etching is used to finally obtain the aperture pattern  18  having the bottom diameter of 0.15 μm. When this first mask material film  13  is used as the etching mask and the film  12  to be processed is vertically etched, the aperture pattern  19  having a diameter of 0.15 μm is obtained. 
   A KrF excimer laser exposing apparatus (an exposure wave length=248 nm) in which NA=0.68 and σ=0.75 is used as the optical condition to expose the resist film  15 . As the resist film, for example, R11JE made by JSR Corporation is used, and its film thickness is defined as 0.4 μm. Also, a parallel flat plate type of a plasma etching apparatus is used to etch the film  12  to be processed, and ammonium (NH 3 ) is used for the etching gas, and the temperature of the substrate is set to 0° C. 
   As mentioned above, the case in which the optical lithography is carried out to thereby form the micro contact hole pattern is exemplified. However, the present invention can be also applied to an electron beam lithography, an ion beam lithography and an X-ray lithography. Moreover, it can be applied not only to the contact hole but also the formation of the micro slit pattern.

Technology Category: 4