Abstract:
The present invention relates to a conditioner for a chemical-mechanical planarization (CMP) pad, which is used in a CMP process that is part of a semiconductor element manufacturing process, and more particularly, to a conditioner for a soft pad, and a method of manufacturing the same, wherein the conditioner can be used under CMP conditions using a slurry having a small amount of polishing particles, and/or a porous pad having comparatively low hardness and very high porosity.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS AND CLAIM OF PRIORITY 
       [0001]    This patent application is a National Phase application under 35 U.S.C. §371 of International Application No. PCT/KR2012/001673, filed Mar. 7, 2012, which claims priority to Korean Patent Application No. 10-2011-0019803 filed Mar. 7, 2011, entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to a conditioner for a chemical-mechanical planarization (CMP) pad, which is used in a CMP process that is part of a semiconductor element manufacturing process. 
         [0004]    2. Description of the Related Art 
         [0005]    CMP techniques for use in semiconductor devices are used to planarize a thin film, such as an insulating film or a metal film formed on a semiconductor wafer. 
         [0006]    Typically, the kind of slurry used in a CMP process varies depending on the planarization of oxides, tungsten, or copper, and the slurry may contain polishing particles so as to mechanically planarize the wafer. In order to achieve chemo-mechanical polishing, an acidic solution may be added. In particular, the polishing particles are responsible for promoting mechanical wear on diamond particles of the conditioner. The polishing particles may primarily include silica or ceria, and the amount of the polishing particles may vary greatly depending on the kind of slurry and the conditions of use thereof. 
         [0007]    The polishing particles are contained in an amount of about 1˜10 wt % in the slurry, and are acidic or neutral depending on the kind of slurry. When such a slurry is used, a load applied to the conditioner is a force of about 5˜14 pounds. Even when diamond particles are used, the serviceable life of the conditioner is approximately 5˜30 hr due to wear of the acute ends of the diamond particles used as cutting tips. 
         [0008]    Optionally, there is provided a copper CMP process, that is performed at the final step of a CMP process, for the polishing of a wafer. The copper CMP process is a process that is conducted under conditions in which the properties of a pad are very soft and a very low load of 3 pounds or less is applied. 
         [0009]    A pad for use in the copper CMP process is commonly exemplified by a Fujibo pad, and a slurry for the Fujibo pad is a planarization slurry having 1% or less of polishing particles, and thus has a very low process load in terms of the conditioner. Thus, the CMP process is performed only when low wear resistance of the cutting tips of the conditioner is required. 
         [0010]    For this reason, however, even when an electrodeposited conditioner, among other conventional CMP pad conditioners, is designed to have a smaller number of diamond particles, the edges of the diamond particles and the acute edges of the cutting tips may easily tear the soft pad or may deform the pores of the surface of the pad. Thus, the pad can no longer be used and undesirably shortens the serviceable life of the pad. Furthermore, this makes it impossible to uniformly maintain the state of the pad during its usage, affecting the uniform control of the material removal rate of a wafer. 
         [0011]    With the goal of solving the aforementioned problems, a CMP pad conditioner has been developed, which is configured such that the surface of a substrate thereof is projected in a predetermined form to provide a plurality of protrusions which are coated with a diamond thin-film using chemical vapor deposition (CVD). In this regard, Korean Patent No. 10-0387954 discloses a CMP pad conditioner, wherein a plurality of truncated pyramids with polygonal bases are formed upward upwards at uniform heights on the surface of the substrate thereof and coated with a diamond layer using CVD. 
         [0012]    However, some limitations are imposed on manufacturing the conditioners in such a manner, in that the cutting tips are processed on the substrate thereof and then coated with a diamond layer using CVD, as disclosed in the above patent. More specifically, an expensive apparatus is required to produce the diamonds, and the size of the chamber should be enlarged to increase productivity, which is regarded as technically difficult and expensive. In the manufacturing cost of the diamond thin-film conditioner, the diamond coating cost is very high and the coating time is 20˜40 hr, resulting in undesirably slow processing speeds. 
         [0013]    Thus, there is a need for a novel conditioner, which may solve the problems associated with the electrodeposited conditioner and the diamond coated conditioner disclosed in the above patent, and may also be applied to a process, including a copper CMP process, under conditions using a very soft pad and a very low load of 3 pounds or less, or using a slurry having polishing particles in amounts as low as 1% or less. 
       SUMMARY 
       [0014]    Culminating in the present invention, intensive and thorough research, carried out by the present inventors aiming to solve the problems encountered in the related art, led to development of a conditioner for a soft pad, which may solve the problems associated with an electrodeposited conditioner and a diamond coated conditioner disclosed in the above patent, and may also be applied to a copper CMP process, etc. 
         [0015]    Accordingly, an aspect of the present invention is to provide a conditioner for a soft pad and a method of manufacturing the same, wherein the conditioner may have a controlled structure depending on a predetermined pattern, so as to stably maintain the material removal rate of a wafer, and is configured such that the manufacturing cost may be drastically reduced. 
         [0016]    Another aspect of the present invention is to provide a conditioner for a soft pad and a method of manufacturing the same, wherein there is no need for a diamond coating process, and thus the material for a substrate useful in manufacturing the conditioner is not limited so long as it satisfies wear resistance. 
         [0017]    Still another aspect of the present invention is to provide a conditioner for a soft pad and a method of manufacturing the same, wherein cutting tips of the conditioner have no diamond layer, thus obviating a CVD diamond coating process, thereby shortening the manufacturing process and reducing the manufacturing cost, resulting in improved productivity. 
         [0018]    Yet another aspect of the present invention is to provide a conditioner for a soft pad and a method of manufacturing the same, wherein there is no need for a diamond coating process, and thus an additional process for controlling the size of the conditioner, after coating it with diamond, may be omitted, unlike conventional diamond coated CMP pad conditioners, thus reducing defect rates. 
         [0019]    The aspects of the present invention are not limited to the foregoing, and other embodiments, which are not mentioned herein, will be clearly understood to those skilled in the art from the following description. 
         [0020]    In order to accomplish the above aspects, the present invention provides a conditioner for a soft pad, comprising a substrate having at least one flat surface; and a plurality of cutting tips formed to protrude upward on parts, or on all surfaces, of the substrate and spaced apart from each other. 
         [0021]    In an embodiment, the substrate and the cutting tips are made of the same material, including any one selected from among a carbide material, a ceramic material, including SiC or Si 3 N 4 , and a composite ceramic material, including one or both of SiO 2  and Al 2 O 3 . 
         [0022]    In an embodiment, the cutting tips are configured such that upper ends thereof are provided in the form of a plane, a line, or a point. 
         [0023]    In an embodiment, when the upper ends of the cutting tips are provided in the form of a plane parallel to the surface of the substrate, the overall shape thereof can be any one or more selected from among a cylindrical shape, a polyprismoidal shape, a truncated conical shape, and a truncated pyramidal shape. 
         [0024]    In an embodiment, the cutting tips are configured to be the same as in one or more selected from among the overall shape, the protrusion height, and the separation interval. 
         [0025]    In an embodiment, the conditioner for a soft pad is applied to a CMP process, including a copper CMP process, under one or both conditions of using a load of 3 pounds or less, and using a slurry having 1% or less polishing particles. 
         [0026]    In addition, the present invention provides a method of manufacturing the conditioner for a soft pad as in any one of claims  1  to  6 , comprising preparing a substrate having a thickness greater than a protrusion height of cutting tips; and forming a plurality of protrusions at a predetermined interval on one surface of the substrate depending on a predetermined pattern, thus forming cutting tips. 
         [0027]    In an embodiment, the protrusions formed in forming the cutting tips are configured such that the upper ends thereof are provided in the form of a plane, a line, or a point. 
         [0028]    In an embodiment, forming the cutting tips is performed using both an etching process and any one of the micromachining processes selected from cutting wheel processing, end milling, milling cutter processing, drilling, tapping, and laser processing, or using either the etching process or any one of the micromachining processes. 
         [0029]    In an embodiment, the etching process includes subjecting the surface of the substrate, on which the protrusions will be formed, to photolithography, then extending part or all of the protrusion height of the protrusions at a predetermined interval by etching, wherein when part of the protrusion height is protruded, forming the rest of the height of the protrusions, which are partially protruded, using any one micromachining process as above, is further performed. 
         [0030]    In an embodiment, when the part of the protrusion height is extended, the protrusion height of the protrusions extended by the etching is 1˜50% of the total protrusion height. 
         [0031]    In an embodiment, the method further comprises subjecting one surface of the substrate, before formation of the cutting tips, to precision grinding and lapping. 
         [0032]    One or more embodiments of the present invention has the following superior effects. 
         [0033]    In a conditioner for a soft pad and a method of manufacturing the same, according to the present invention, the conditioner has a controlled structure depending on a predetermined pattern so as to stably maintain the material removal rate of a wafer, and furthermore, the manufacturing cost can be drastically reduced. 
         [0034]    Also, in a conditioner for a soft pad and a method of manufacturing the same, according to the present invention, there is no need for a diamond coating process, and thus the material for a substrate useful in manufacturing the conditioner is not limited so long as it satisfies wear resistance. 
         [0035]    Also, in a conditioner for a soft pad and a method of manufacturing the same, according to the present invention, cutting tips of the conditioner have no diamond layer, thus obviating the need of a CVD diamond coating process, thereby shortening the manufacturing process and reducing the manufacturing cost, resulting in improved productivity. 
         [0036]    Also, in a conditioner for a soft pad and a method of manufacturing the same, according to another embodiment of the present invention, there is no need for a diamond coating process, and thus an additional process for controlling the size of the conditioner after coating it with diamond can be omitted, unlike conventional diamond coated CMP pad conditioners, thus reducing defect rates. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0037]      FIG. 1  illustrates a graph of the measurement results for pad wear rates (PWR) in a copper CMP process using a conditioner for a soft pad according to an example of the present invention, a known CVD diamond coated conditioner (comparative example), and an electrodeposited conditioner; and 
           [0038]      FIG. 2  illustrates the surface of a conditioned Fujibo pad after a copper CMP process using a conditioner for a soft pad according to an example of the present invention, a known CVD diamond coated conditioner (comparative example), and an electrodeposited conditioner. 
       
    
    
     DETAILED DESCRIPTION 
       [0039]    Although the terms used in the description of the present invention are selected from generally known and used terms, some of the terms mentioned in the description of the present invention have been selected by the applicant, the detailed meanings of which should be understood not simply by the actual terms used, but by the meaning of each term as desired in the detailed description of the invention and/or in consideration of the meanings used. 
         [0040]    As used herein, the term “cutting tip” means a single protrusion formed on the surface of a substrate as a cutting unit, and may be used with the same meaning as a “protrusion” in some cases. 
         [0041]    Also, as used herein, the term “soft pad” means a pad for use in a CMP process under the conditions of using a load of 3 pounds or less and/or using a slurry having 1% or less polishing particles. 
         [0042]    Hereinafter, a detailed description will be given for the technical configuration of the present invention with reference to embodiments illustrated in the appended drawings. 
         [0043]    However, the present invention is not limited to such embodiments, and may be modified. Throughout the description, the same reference numerals used to describe the present invention designate the same elements. 
         [0044]    The first technical feature of the present invention is a conditioner for a soft pad, which has a controlled structure depending on a predetermined pattern, so as to stably maintain the material removal rate of a wafer. The conditioner for a soft pad is also configured such that the manufacturing cost may be drastically reduced due to the material for a substrate useful in manufacturing a conditioner are not limited, so long as they satisfy wear resistance, without the need for a diamond coating process. 
         [0045]    Therefore, the conditioner for a soft pad according to the present invention includes a substrate having at least one flat surface and a plurality of cutting tips formed to protrude upward on part, or all, of the surface thereof, and spaced apart from each other. 
         [0046]    The substrate and the plurality of cutting tips, which constitute the conditioner for a soft pad, may be integrally formed so as to derive from the same material, and the material is not limited so long as it satisfies wear resistance, and may be any one selected from a carbide material, a ceramic material, including SiC or Si 3 N 4 , and a composite ceramic material, including one or both of SiO 2  and Al 2 O 3 . 
         [0047]    The cutting tips may be configured such that the upper ends thereof are provided in the form of a plane, a line, or a point so long as they are formed to protrude upward on the surface of the substrate depending on the predetermined pattern. In the case where the upper ends of the cutting tips are provided in the form of a plane parallel to the surface of the substrate, the overall shape thereof may include any one or more selected from a cylindrical shape, a polyprismoidal shape, a truncated conical shape, and a truncated pyramidal shape. 
         [0048]    Also, the cutting tips may be configured such that they may be individually different from each other in overall shape, protrusion height, and separation interval, or may be classified into several groups that are different from each other in overall shape, protrusion height, and separation interval, depending on the controlling conditions/intentions of a worker. However, in the case where the cutting tips are configured to be the same in one or more selected from the overall shape, protrusion height, and separation interval, it may be so long as they are in terms of stably maintaining the material removal rate of the wafer. 
         [0049]    As apparent from the following test examples, in the case where the conditioner for a soft pad according to the present invention is applied to a CMP process, including a copper CMP process, requiring precise uniformity under conditions of using a load of 3 pounds or less and/or using a slurry having 1% or less polishing particles, the conditioner of the present invention may exhibit performance equal to or greater than that of a conventional CMP pad conditioner coated with a diamond layer. 
         [0050]    The second technical feature of the present invention is a method of manufacturing the conditioner for a soft pad, wherein the cutting tips of the conditioner have no diamond layer, thus obviating a CVD diamond coating process, thereby shortening the manufacturing process and reducing the manufacturing cost. Also, an additional process necessary to control the size of the conditioner after coating it with diamond may be omitted, unlike conventional diamond coated CMP pad conditioners, allowing reductions in defect rates and considerable improvements in productivity. 
         [0051]    Thus, the method of manufacturing the conditioner for a soft pad according to the present invention includes preparing a substrate having a thickness greater than the protrusion height of the cutting tips; and forming a plurality of protrusions at a predetermined interval on one surface of the substrate depending on a predetermined pattern, thus forming the cutting tips. 
         [0052]    The plurality of protrusions formed at the step of producing the cutting tips may be configured such that the upper ends thereof may be provided in the form of a plane, a line, or a point. Thus, the protrusion height, overall shape, and separation interval of and between the protrusions are not limited so long as they are controlled depending on the predetermined pattern. 
         [0053]    Furthermore, the step of producing the cutting tips may be performed using both an etching process and any one micromachining process selected from cutting wheel processing, end milling, milling cutter processing, drilling, tapping, and laser processing, or may be conducted by either of the etching process or the micromachining process. 
         [0054]    The etching process includes subjecting the surface of the substrate, on which the protrusions will be formed, to photolithography, and extending part or all of the protrusion height of the protrusions at a predetermined interval by etching. As such, known dry etching and wet etching processes may be utilized. 
         [0055]    In the case where part of the protrusion height is extended by etching, forming the rest of the height of the protrusions, which are partially extended, may be further carried out using any one micromachining process as above. When the step of producing the cutting tips is performed using both the etching process and the micromachining process in this way, the etching process may be conducted first, followed by the micromachining process. 
         [0056]    Conversely, in the case where part of the protrusion height of the cutting tips is extended by etching at the step of producing the cutting tips, the protrusion height of the protrusions extended by etching may be 1˜50% of the total protrusion height of the cutting tips. 
         [0057]    In some cases, in order to more precisely control the overall shape, protrusion height, etc. of the cutting tips, a step of subjecting one surface of the substrate to precision grinding and lapping may be further performed before the step of producing the cutting tips. 
       EXAMPLES 
     Example 1 
       [0058]    In order to ensure surface flatness, a Si 3 N 4  substrate having a flatness tolerance of 3 mm±0.002 mm or less was prepared via lapping. To produce cutting tips, depending on a predetermined pattern, micromachining was performed using a polisher, and protrusions were processed such that the width and length were 50 μm, and the height was 50 μm, and the number of protrusions was 10,000, thereby completing the conditioner for a soft pad. 
       Comparative Example 1 
       [0059]    To form a diamond coating on a substrate having protrusions formed using the same process as in Example 1, the substrate having protrusions was pretreated using an ultrasonic device so that diamond powder having a size of 1˜2 μm was fed in to facilitate diamond nucleation in order to enhance adhesion between the diamond nuclei and the thin film. The diamond thin film was grown for 10 hr using a thermal filament process (i.e., a CVD process), thereby manufacturing a CVD diamond coated conditioner (CVD Disk). 
       Test Example 1 
       [0060]    Using the conditioner for a soft pad of the Example 1, the CVD diamond coated conditioner of the Comparative Example 1, and a commercially available electrodeposited conditioner, a copper CMP process was performed for 31 hr using a Fujibo pad and a planarization slurry having 1% or less polishing particles. The resulting pad wear rate (PWR) per conditioner was measured. The results are illustrated in  FIG. 1 . 
         [0061]    As illustrated in  FIG. 1 , the electrodeposited conditioner decreased the PWR to 50% after 15 hr, but the CVD diamond coated conditioner and the conditioner for a soft pad, according to the present invention, maintained the PWR even after 30 hr. 
       Test Example 2 
       [0062]    The surface of the Fujibo pad conditioned using each conditioner above after performing Test Example 1 was observed via incremental and sequential magnification, and was compared to the initial CMP process. The surface images are illustrated in  FIG. 2 . 
         [0063]    As illustrated in  FIG. 2 , when using the electrodeposited conditioner, the surface of the soft Fujibo pad was bitten, and the PWR was drastically lowered. The surface of the pad using the CVD diamond coated conditioner was considerably similar to that of the pad using the conditioner for a soft pad according to the present invention. 
       Test Example 3 
       [0064]    One hundred (100) diamond particles and one hundred (100) cutting tips were chosen as samples at a certain portion of each conditioner, and the exposed heights of the samples, before and after Test Example 1, were measured. The results are shown in Table 1 below. 
         [0000]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Exposed Heights, Before and After 
               
             
          
           
               
                   
                   
                   
                 CVD 
               
               
                   
                 Electrodeposited 
                 Conditioner 
                 diamond coated 
               
               
                 Height 
                 conditioner 
                 for soft pad 
                 conditioner 
               
               
                   
               
               
                 Before 
                 57.1 μm (31.4-97.2) 
                 50.7 μm (49.9-51.6) 
                 50.7 μm (49.7-51.3) 
               
               
                 Use 
               
               
                 (Max- 
               
               
                 Min) 
               
               
                 After 
                 55.8 μm (31.1-94.5) 
                 50.2 μm (49.6-51.1) 
                 50.1 μm (49.3-51.0) 
               
               
                 Use 
               
               
                 (Max- 
               
               
                 Min) 
               
               
                 Wear 
                  2.3 μm 
                  0.5 μm 
                  0.6 μm 
               
               
                 rate 
               
               
                   
               
             
          
         
       
     
         [0065]    As is apparent from Table 1, there were no significant changes in the exposed heights in all the conditioners. However, the electrodeposited conditioner had significant changes in the Max-Min values (˜3-fold), whereas the CVD diamond coated conditioner and the conditioner for a soft pad, according to the present invention, had no significant changes in Max-Min values. This is thought to be because the pad was severely rubbed by the smaller number of working diamond particles of the electrodeposited conditioner. 
         [0066]    As apparent from the results of Test Examples 1-3, wherein the conditioner for a soft pad according to the present invention is used in the copper CMP process, a performance equal to or greater than that of the CVD diamond coated conditioner can be exhibited. 
         [0067]    Therefore, in the case where the conditioner for a soft pad according to the present invention is applied to a CMP process, including a copper CMP process, under conditions of using a load of 3 pounds or less and/or using a slurry having 1% or less polishing particles, the performance thereof can be seen to be equal to or greater than that of a conventional diamond coated CMP pad conditioner. 
       Reference Test Example 
       [0068]    The conditioner for a soft pad of the Example 1 and the CVD diamond coated conditioner of the Comparative Example 1 were subjected to W2000 CMP using IC 1010 for 5 hr under a load of 10 lbf, and the heights of the cutting tips of the conditioners were measured before and after the above process. The results are shown in Table 2 below. 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Before and After Heights of the Cutting Tips 
               
             
          
           
               
                   
                 Conditioner for 
                 CVD Diamond 
               
               
                   
                 Soft Pad 
                 Coated Conditioner 
               
               
                   
                   
               
             
          
           
               
                 Average Height of Cutting Tips 
                 50.7 
                   
                 50.7 
                   
               
               
                 Before Use 
               
               
                 Average Height of Cutting Tips 
                 41.9 
                   
                 49.7 
               
               
                 After Use 
               
               
                 Wear Speed of Cutting Tips 
                 1.76 
                 μm/hr 
                 0.2 
                 μm/hr 
               
               
                   
               
             
          
         
       
     
         [0069]    As apparent from Table 2, the conditioner for a soft pad, according to the present invention, having no diamond coating is difficult to apply to a process using a slurry having polishing particles in amounts as high as about 6%, and high loads as in the W2000 CMP process because of the high wear speeds of the cutting tips thereof. 
         [0070]    Although the embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions, and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.