Abstract:
Provided is a semiconductor device fabrication apparatus comprising:
       a filter which contains a polar crystal, and filters pure water or a liquid containing pure water as a solvent; and   a working section which has a pressing mechanism configured to apply a pressure to said filter, and supplies the filtered pure water or the filtered liquid containing pure water as a solvent to a surface of an object to be polished or cleaned, thereby performing a polishing process or cleaning process.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is based upon and claims benefit of priority under 35 USC §119 from the Japanese Patent Application No. 2003-371079, filed on Oct. 30, 2003, the entire contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   The present invention relates to a semiconductor device fabrication method and apparatus. 
   In the field of recent semiconductor device fabrication, the development of micropatterned, high-density, multilayered interconnections is rapidly advancing as the LSI performance improves. Accordingly, the technique is rapidly improving in each fabrication process. 
   For example, in a CMP (Chemical Mechanical Polishing) process used in the formation of metal damascene interconnections, high cleaning is necessary in cleaning during or after polishing. This is so because even a slight amount of impurity has a large influence on the yield as micropatterning progresses. 
   As described above, it is important to increase the level of cleanliness in each process, and advance to the subsequent process without leaving any impurity or residue produced in the preceding process behind. 
   The cleaning process, however, is complicated because too much importance is attached to the performance and effect of, e.g., a slurry and liquid chemical. 
   Accordingly, the sizes of attached apparatuses increase, and there is no inexpensive, effective cleaning member which can be easily attached. 
   For example, patent reference 1 describes the overall arrangement of a CMP apparatus. This apparatus is characterized by cleaning a substrate by supplying ionic water. However, a practical arrangement of this ionic water supply apparatus is as disclosed in FIG. 2 of patent reference 2. That is, the increase in size of the apparatus is unavoidable.
     Patent reference 1: Japanese Patent Laid-Open No. 2000-294524   Patent reference 2: Japanese Patent Laid-Open No. 2001-358111   

   As described above, no conventional apparatus can achieve high cleanliness with a compact, simple arrangement. 
   SUMMARY OF THE INVENTION 
   According to one aspect of the present invention, there is provided a semiconductor device fabrication apparatus comprising: 
   a filter which contains a polar crystal, and filters pure water or a liquid containing pure water as a solvent; and 
   a working section which has a pressing mechanism configured to apply a pressure to said filter, and supplies the filtered pure water or the filtered liquid containing pure water as a solvent to a surface of an object to be polished or cleaned, thereby performing a polishing process or cleaning process. 
   According to another aspect of the present invention, there is provided a semiconductor device fabrication method comprising: 
   supplying pure water or a liquid containing pure water as a solvent to a filter containing a polar crystal while applying a pressure to the filter, thereby filtering the pure water or the liquid containing pure water as a solvent; and 
   supplying the filtered pure water or the filtered liquid containing pure water as a solvent to a surface of an object to be polished or cleaned, thereby performing a polishing process or cleaning process. 
   According to still another aspect of the present invention, there is provided a semiconductor device fabrication method comprising: 
   placing an object to be polished or cleaned in a manner that a surface to be polished or cleaned is in contact with a pad placed on a surface of a turntable; and 
   rotating the turntable, and supplying pure water or a liquid containing pure water as a solvent to a central region of the pad, thereby polishing or cleaning the object to be polished or cleaned, 
   wherein the pad has a filter which contains a polar crystal, and filters the pure water or the liquid containing pure water as a solvent supplied to the central region, and 
   the pure water or the liquid containing pure water as a solvent filtered by the filter is supplied to the surface of the object to be polished or cleaned. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view showing the arrangement of a semiconductor fabrication apparatus according to the first embodiment of the present invention; 
       FIGS. 2A and 2B  are sectional views showing the longitudinal cross sections of a semiconductor substrate when a cleaning process is performed on a TiN film and AlCu film after CMP by using the semiconductor fabrication apparatus according to the first embodiment; 
       FIG. 3  is a perspective view showing the arrangement of a semiconductor fabrication apparatus according to the second embodiment of the present invention; 
       FIG. 4  is a longitudinal cross sectional view showing the arrangements of polishing cloth and a turntable used in the semiconductor fabrication apparatus shown in  FIG. 3 ; 
       FIG. 5  is a perspective view showing the arrangement of a semiconductor fabrication apparatus according to the third and fourth embodiments of the present invention; 
       FIG. 6  is a longitudinal cross sectional view showing the arrangement of a roll used in the semiconductor fabrication apparatus shown in  FIG. 5 ; and 
       FIGS. 7A and 7B  are sectional views showing the longitudinal cross sections of a semiconductor substrate when a cleaning process is performed on a Ta film and Cu film after CMP by using the semiconductor fabrication apparatuses according to the third and fourth embodiments. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Embodiments of the present invention will be described below with reference to the accompanying drawings. 
   (1) First Embodiment 
   A semiconductor device fabrication apparatus and method according to the first embodiment of the present invention will be explained below. 
     FIG. 1  shows the arrangement of a fabrication apparatus capable of polishing or cleaning according to the first embodiment. 
   A pad  71  is placed on a turntable  70  which rotates in the direction of an arrow  76 . 
   A filter  74  is adhered on the surface of a central portion of the pad  71 . It is also possible to form a hole in the central portion of the pad  71 , and embed the filter  74  in this hole. 
   The pad  71  can be formed of a porous material having open cells. More specifically, the pad  71  can be formed of, e.g., a polymer-based material such as polyurethane or polypropylene. 
   The filter  74  is a sponge-like filter coated with a paste obtained by mixing a solvent, binder, or the like in grains (to be referred to as tourmaline grains hereinafter) of tourmaline as an example of a polar crystal. 
   A semiconductor wafer  72 , for example, is placed on a region of the pad  71  except for the filter  74 . 
   A top ring head  81  as a holding member for holding the semiconductor wafer  72  such that the semiconductor wafer  72  is in contact opposite to the pad  71  holds the semiconductor wafer  72 . The top ring head  81  presses the semiconductor wafer  72  against the pad  71 , and rotates in the same direction as the turntable  70  as indicated by an arrow  83 . Also, a dressing head  82  for dressing the pad  71  is placed in a position where the dressing head  82  opposes the top ring head  81  on the other side of the filter  74  of the pad  71 . The dressing head  82  rotates in the same direction as the top ring head  83  as indicated by an arrow  84 . 
   On the surface of the filter  74 , pure water or a liquid containing pure water as a solvent, e.g., a slurry or cleaning solution, is supplied. 
   Referring to  FIG. 1 , three liquid supply pipes  73   a  to  73   c  are arranged and, as indicated by arrows  75   a  to  75   c , supply the desired one of the pure water, slurry, and cleaning solution. However, it is also possible to freely set the number of liquid supply pipes if necessary. 
   When the pure water or the liquid containing pure water as a solvent passes through the filter  74 , the contained water comes in contact with the tourmaline grains to cause electrolysis, and this decomposes the water into hydrogen ions and hydroxide ions. 
   The hydrogen ions combine with electrons attracted to the tourmaline grains, and are released as hydrogen gas. This makes the water weakly alkaline. 
   The hydroxide ions react with undecomposed water to produce hydroxyl ions. This induces the surface active effect, and increases the cleaning effect. 
   A case in which the first embodiment is applied when CMP is performed on, e.g., an AlCu (0.5 at %) film and then a cleaning process is performed will be described below. 
   As shown in  FIG. 2A , a 300-nm thick insulating film  201  is deposited on a semiconductor substrate  200  by PCVD (Plasma Chemical Vapor Deposition) using a TEOS gas, and so patterned as to have a 150-nm deep trench pattern A 1  as a recess. 
   In addition, a 10-nm thick TiN film  202  is deposited on the entire surface, and a 180-nm thick AlCu (0.5 at %) film  203  is also deposited on the entire surface. 
   After that, as shown in  FIG. 2B , unnecessary portions of the TiN film  202  and AlCu film  203  are removed by CMP, and a cleaning process is successively performed. 
   The first embodiment was applied to the CMP process and the cleaning process after that. 
   The polishing conditions and the processing conditions of cleaning were as follows. 
   (Polishing Conditions) 
   Polishing load: 300 gf/cm 2 , carrier (top ring head) rotational speed: 102 rpm, turntable rotational speed: 100 rpm, slurry flow rate: 200 cc/min, 
   Slurry: colloidal silica dispersion (grain size=25 nm, dispersion concentration=3 wt %, pH=7) 
   Polishing time: 80 sec. 
   (Processing Conditions) 
   Polishing load: 300 gf/cm 2 , carrier (top ring head) rotational speed: 102 rpm, turntable rotational speed: 100 rpm, pure water flow rate: 500 cc/min, 
   Processing time: 30 sec. 
   In Example 1 of the first embodiment, pure water for cleaning was filtered by the filter  74 . In Example 2 of the first embodiment, both a slurry and pure water for cleaning were filtered by the filter  74 . In Comparative Example 1 using the conventional technique, CMP was performed without filtering a slurry and pure water by the filter  74 . After the processing, the numbers of particles and the numbers of defects (including the numbers of corrosions and the numbers of scratches) on the Al interconnections of these examples and comparative example were compared. 
   In Comparative Example 1, the number of particles was 760/cm 2 , and the number of defects was 57/cm 2 . In Example 1, the number of particles was 18/cm 2 , and the number of defects was 7/cm 2 . In Example 2, the number of particles was 15/cm 2 , and the number of defects was 5/cm 2 . These results reveal that the first embodiment greatly reduces the number of particles and the number of defects. 
   The polar crystal used in the filter  74  was black tourmaline having an average grain size of 0.5 μm and a dispersion concentration of 50 wt %. This black tourmaline was dispersed in a resin having filtering properties. 
   To increase the cleaning effect, the average grain size and dispersion concentration of the polar crystal are important factors. 
   For example, assuming that a product in which the number of scratches and the number of defects on the surface of the Al film were 20/cm 2  or less and 10/cm 2  or less, respectively, was a good product, the average grain size of the polar crystal and a non-defective product (O) and defective product (x) had the following relationship. 
   
     
       
             
             
             
           
             
             
             
           
         
             
                 
                 
             
             
                 
               Number of scratches 
               Number of defects 
             
             
                 
                 
             
           
           
             
                 
             
           
        
         
             
               No polar crystal 
               x 
               x 
             
             
               0.05 μm 
               ∘ 
               ∘ 
             
             
                0.1 μm 
               ∘ 
               ∘ 
             
             
                0.5 μm 
               ∘ 
               ∘ 
             
             
                1.0 μm 
               ∘ 
               ∘ 
             
             
                5.0 μm 
               ∘ 
               ∘ 
             
             
                 10 μm 
               ∘ 
               ∘ 
             
             
                 50 μm 
               ∘ 
               x 
             
             
                100 μm 
               x 
               x 
             
             
                 
             
           
        
       
     
   
   Note that the dispersion concentration was 50 wt %. 
   The above results indicate that the average grain size of the polar crystal by which good products are obtained is 50 μm or less, preferably, 0.05 to 10 μm. 
   Note that no regions of less than 0.05 μm were observed because pulverization of grains of the polar crystal is generally difficult. However, since a smaller average grain size is presumably more desirable, the effect of the first embodiment can be expected. 
   On the other hand, when the average grain size of the polar crystal was 0.5 μm, the dispersion concentration of the grains of the polar crystal and a good product and bad product had the following relationship. 
   
     
       
             
             
             
           
             
             
             
           
         
             
                 
                 
             
             
                 
               Number of scratches 
               Number of defects 
             
             
                 
                 
             
           
           
             
                 
             
           
        
         
             
               No polar crystal 
               x 
               x 
             
             
                1 wt % 
               ∘ 
               x 
             
             
                5 wt % 
               ∘ 
               ∘ 
             
             
               10 wt % 
               ∘ 
               ∘ 
             
             
               25 wt % 
               ∘ 
               ∘ 
             
             
               50 wt % 
               ∘ 
               ∘ 
             
             
               75 wt % 
               ∘ 
               ∘ 
             
             
               90 wt % 
               ∘ 
               ∘ 
             
             
               99 wt % 
               ∘ 
               ∘ 
             
             
                 
             
           
        
       
     
   
   From the above results, the dispersion concentration of the polar crystal by which good products are obtained is 1 wt % or more, preferably, 5 to 99 wt %. 
   (2) Second Embodiment 
   The second embodiment of the present invention will be described below with reference to the accompanying drawings. 
     FIG. 3  shows an outline of the overall arrangement of a polishing apparatus. 
   Polishing cloth (a pad)  103  is placed on a turntable  101  which rotates in the direction of an arrow  102 , and a semiconductor wafer, for example, is set as an object  104  to be polished. 
   As will be described later, a slurry is supplied inside the turntable  101  and discharged to its surface, and the discharged slurry is supplied to the surface to be polished of the object  104  through the polishing cloth  103 . 
   A top ring head  121  as a holding member or as a pressing mechanism which presses the polishing cloth  103  holds the object  104 , and rotates the object  104  while pressing it against the polishing cloth  103 . Also, a dressing head  123  for dressing the polishing cloth  103  opposes the top ring head  121  on the other side of the center of the turntable  101 , and rotates in the same direction as the top ring head  121  as indicated by an arrow  124 . 
     FIG. 4  shows the sectional structures of the polishing cloth  103  and turntable  101 . 
   The turntable  101  has a piping mechanism  10  having a pipe  11  in which a slurry flows in the direction of an arrow  21 , and pipes  12  in which a slurry flows in the direction of arrows  22 . 
   The polishing cloth  103  is adhered on the surface of the turntable  101  by, e.g., a double-coated adhesive tape (not shown). A filter  13  containing tourmaline grains is formed on that surface of the polishing cloth  103 , which is in contact with the turntable  101 . 
   A slurry supplied through the pipes  11  and  12  is filtered through the filter  13 , penetrates into the polishing cloth  103 , and oozes out onto a surface  15  of the polishing cloth  103 . As described above, the object  104  to be polished is pressed against the surface  15 , and rotated in contact with the surface  15 . 
   The polishing cloth  103  can be formed of, e.g., a porous material having open cells. For example, the polishing cloth  103  can be formed of a polymer-based material such as polyurethane or polypropylene. 
   The filter is a sponge-like filter which is formed by using a material such as polyurethane and coated with a paste obtained by mixing a solvent, binder, or the like in tourmaline grains. 
   When a slurry passes through the filter  13  as described above, water contained in the slurry comes in contact with the tourmaline grains to cause electrolysis. Hydrogen ions produced by decomposition combine with electrons attracted to the tourmaline grains, and are released as hydrogen gas. This makes the water weakly alkaline. Also, hydroxide ions react with undecomposed water to produce hydroxyl ions. This increases the cleaning effect. 
   The arrangement of a substrate to be polished and the polishing conditions were the same as in the first embodiment. 
   On the same polishing table, cleaning was performed under the following processing conditions. 
   (Processing Conditions) 
   Polishing load: 300 gf/cm 2 , carrier (top ring head) rotational speed: 102 rpm, turntable rotational speed: 100 rpm, pure water flow rate: 500 cc/min, 
   Processing time: 30 sec. 
   After the polishing, the numbers of particles and the numbers of defects on the Al interconnections were compared. Consequently, while the number of particles was 18/cm 2  and the number of defects was 7/cm 2  in Example 1 of the first embodiment, the number of particles was 10/cm 2  and the number of defects was 4/cm 2  in Example 3 of the second embodiment. This indicates that the second embodiment can further reduce the number of particles and the number of defects from those of the first embodiment. 
   As described above, the second embodiment uses the piezoelectric effect of the polar crystal by which the polar crystal generates a voltage when a pressure is applied to it, thereby electrically promoting activation and further increasing the cleaning effect. 
   (3) Third Embodiment 
   A cleaning apparatus and method will be described below as a semiconductor fabrication apparatus and method, respectively, according to the third embodiment of the present invention. 
   The third embodiment uses a pressure as in the second embodiment, but uses no polishing table. 
   As shown in  FIG. 5 , a semiconductor wafer  41  is supported by a plurality of rollers  55 . When the rollers  55  rotate in the direction of an arrow  56 , the semiconductor wafer  41  rotates in the direction of an arrow  51 . Rolls  42  and  43  are arranged on the two surfaces of the semiconductor wafer  41 , and rotate in opposite directions indicated by arrows  52  and  53 , respectively. 
   As will be described later, each of the rolls  42  and  43  contains a filter, and also functions as a pressing mechanism which applies a pressure to this filter.  FIG. 6  shows the sectional structure of each of the rolls  42  and  43 . 
   A sponge-like, ring-shaped elastic member  61  is formed on the outer circumferential surface of the roll  42  ( 43 ). The elastic member  61  presses the surface of the semiconductor wafer  41  in direct contact with it. A ring-like filter  62  is formed on the inner surface of the elastic member  61 . 
   Similar to the filter  13  of the second embodiment, the filter  62  is a sponge-like filter which is made of, e.g., polyurethane and coated with a paste obtained by mixing a solvent, binder, or the like in tourmaline grains. 
   A piping mechanism  63  is placed inside the roll  42  ( 43 ). Accordingly, a hollow portion  65  is present in a central portion of the roll  42  ( 43 ), and passages  64  are radially formed from the hollow portion  65 . 
   Pure water or cleaning water is supplied into the hollow portion  65 , and passes through the filter  62  through the passages  64 . This pure water or cleaning water passing through the filter  62  diffuses and is held inside the sponge-like elastic member  61 . When the elastic member  61  is rotated as it is pressed against the semiconductor wafer  41 , the pure water or cleaning water is supplied onto the surface of the semiconductor wafer  41  and cleans it. 
   Practical examples of the third embodiment will be explained below. 
   As shown in  FIG. 7A , a 300-nm thick insulating film  301  made of black diamond (manufactured by AMAT) is deposited by PCVD on a semiconductor substrate  300  as a substrate to be polished, and so patterned as to have a 150-nm deep trench pattern A 2 . 
   After that, a 6-nm thick Ta film  302  is deposited on the entire surface, and a 180-nm thick Cu film  303  is also deposited on the entire surface. 
   As shown in  FIG. 7B , unnecessary portions of the Ta film  302  and Cu film  303  are removed by CMP. 
   The substrate  300  is then moved from the polishing table to an apparatus for performing roll cleaning, and a cleaning process is performed. The third embodiment is applied to this cleaning process after CMP. 
   The practical polishing conditions are as follows. 
   (Polishing Conditions) 
   Polishing load: 300 gf/cm 2 , carrier (top ring head) rotational speed: 102 rpm, turntable rotational speed: 100 rpm, slurry flow rate: 200 cc/min, 
   Slurry: CMS7401+CMS7452 (manufactured by JSR) 
   Polishing cloth: IC1000 (manufactured by Rodel) 
   Polishing time: 60 sec. 
   The practical processing conditions of cleaning are as follows. 
   (Processing Conditions) 
   Polishing load: 300 gf/cm 2 , roll rotational speed: 150 rpm, semiconductor substrate rotational speed: 30 rpm, pure water flow rate: 1,000 cc/min, 
   Processing time: 30 sec. 
   Note that five types of tourmaline grains presented below were dispersed in the filter  62 . 
   EXAMPLE 4 
   Black tourmaline (average grains size: 0.5 μm, dispersion concentration: 50 wt %) 
   EXAMPLE 5 
   Black tourmaline (average grains size: 0.5 μm, dispersion concentration: 35 wt %)+red tourmaline (average grains size: 0.5 μm, dispersion concentration: 15 wt %) 
   EXAMPLE 6 
   Black tourmaline (average grains size: 0.5 μm, dispersion concentration: 25 wt %)+red tourmaline (average grains size: 0.5 μm, dispersion concentration: 25 wt %) 
   EXAMPLE 7 
   Black tourmaline (average grains size: 0.5 μm, dispersion concentration: 15 wt %)+red tourmaline (average grains size: 0.5 μm, dispersion concentration: 35 wt %) 
   EXAMPLE 8 
   Red tourmaline (average grains size: 0.5 μm, dispersion concentration: 50 wt %) 
   In Examples 4 to 8 according to the third embodiment, pure water was filtered by the filter  62 . In Comparative Example 2 according to the conventional technique, pure water was not filtered by the filter  62 . In each of these examples and comparative example, the yield on an interconnection having a width of 0.1 μm and a length of 1 m was checked. 
   In Comparative Example 2, the yield was 85% . By contrast, in each of Examples 4 to 8, the yield was 97% or more, i.e., the yield increased by 12% or more. 
   Also, the same effect could be obtained even when a mixture of tourmaline grains was used. Furthermore, the same effect was obtained even when the substrate to be polished or the substrate to be cleaned was hydrophobic. 
   (4) Fourth Embodiment 
   The fourth embodiment of the present invention will be described below. 
   The fourth embodiment differs from the third embodiment using pure water in that a liquid chemical containing pure water as a solvent is used. The rest of the arrangement is the same as the third embodiment, so a detailed explanation thereof will be omitted. 
   The practical processing conditions of cleaning are as follows. 
   In Example 9 of the fourth embodiment, unlike in Examples 4 to 8 of the third embodiment, the processing conditions of cleaning after polishing included the use of a solution mixture of pure water and an aqueous citric acid solution. 
   (Processing Conditions) 
   Load: 300 gf/cm 2 , roll rotational speed: 150 rpm, semiconductor substrate rotational speed: 30 rpm, pure water flow rate: 500 cc/min, 
   0.6 wt % aqueous citric acid solution flow rate: 500 cc/min., 
   Processing time: 30 sec. 
   The yield of interconnections in Example 9 of the fourth embodiment increased to 99% or more from 97% or more of Examples 4 to 8 of the third embodiment. 
   In the first to fourth embodiments as described above, pure water or a liquid containing pure water as a solvent is filtered by a filter containing a polar crystal, and supplied to the surface of an object to be polished or cleaned. Since this makes a large-scale apparatus such as an ionic water supply apparatus unnecessary, it is possible to decrease the size of the apparatus, reduce the cost, and improve the cleanliness. 
   Each of the above embodiments is merely an example, and hence does not limit the present invention. Therefore, these embodiments can be variously modified within the technical scope of the present invention. 
   In each embodiment, tourmaline is used as a polar crystal. More specifically, it is possible to use at least one type of black tourmaline, red tourmaline, schorl tourmaline, lithium tourmaline, dravite tourmaline, rubelite tourmaline, pink tourmaline, indicolite, paraiba tourmaline, and watermelon, or a mixture of these tourmalines. Regardless of the type of tourmaline used in each embodiment, the average grain size and dispersion concentration of the polar crystal are preferably 50 μm or less and 1 wt % or more, respectively, and more preferably, 0.05 to 10 μm and 5 to 99 wt %, respectively. 
   Also, as pure water or a liquid containing pure water as a solvent, it is possible to appropriately use a slurry or cleaning water such as a liquid chemical.