Abstract:
A method of manufacturing a cutting tool is disclosed. An object of the manufacturing method of a cutting tool is to reduce contamination of an abrasive layer surface, particularly, agglomeration contamination due to slurry by improving hydrophobicity maintaining performance of an abrasive layer. A cutting tool according to the method of manufacturing comprises an abrasive layer on a base member, the abrasive layer having abrasives bonded to a surface thereof; and a coating on the surface of the abrasive layer that is a hydrophobic material film.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The presently disclosed subject matter relates to a cutting tool, and more specifically, to a hydrophobic cutting tool having high hydrophobicity maintaining performance of a surface thereof and a method for manufacturing the same. In particular, the disclosed subject matter relates to a CMP (Chemical Mechanical Polishing) conditioner, i.e., cutting tool used in a CMP pad conditioning process and suitable for reducing accumulation of slurry thereon. 
         [0003]    2. Description of Related Art 
         [0004]    A cutting tool is a tool that cuts a work piece using abrasives, i.e., cutting particles. Cutting may include grinding such as a cylinder grinding, an inner surface grinding, or a plane grinding to grind a part of a work piece. For instance, grinding may include all kinds of machining works capable of being performed using abrasives such as diamond particles. 
         [0005]    In general, a cutting tool comprises a substrate and an abrasive layer formed on a surface of the substrate, and has a structure wherein a plurality of abrasives is bonded to the surface of the abrasive layer. The bonding of the abrasives is performed by various methods including electrodeposition, sintering, and brazing. The abrasives include diamond, CBN (cubic boron nitride), alumina, and silicon carbide particles. 
         [0006]    In a machining work using a cutting tool, a phenomenon that a surface of an abrasive holding layer is contaminated occurs, and the surface is more and more contaminated as the working time increases. Generally, that phenomenon occurs particularly in machining with cutting solutions including abrasive particles. During conditioning the CMP pad with CMP conditioner, slurry particles and residues are accumulated on the surface of the CMP conditioner, thus causing a serious contamination problem on that surface. 
         [0007]    As well known, a CMP pad is used in global planarization of a semiconductor wafer, and a CMP conditioner is a type of cutting tool for improving performance and life span of the CMP pad by removing clogging of micro pores formed in a surface of the CMP pad. 
         [0008]      FIG. 1  shows optical microscope images illustrating changes in the magnitude of surface contamination as a function of CMP conditioning time at several test conditions. The images in  FIG. 1  show the changes in the surface contamination before CMP conditioning (i.e., the reference point), and 30, 60, 90, 120, and 150 minutes after the CMP conditioning, respectively. Referring to  FIG. 1 , it can be confirmed that a considerable amount of slurry contaminants appears 30 minutes after the CMP conditioning, and such contaminants increase while they are continuously agglomerated as the conditioning time increases. 
         [0009]    The surface contamination of an abrasive layer of a CMP conditioner due to slurry deteriorates the efficiency of the CMP conditioning process. The deteriorated efficiency of the CMP conditioning process causes a wafer to be scratched during polishing of the wafer using a CMP pad, and lowers the production efficiency by increasing the number of particles on the wafer after the polishing. 
       BRIEF SUMMARY 
       [0010]    One reason for contaminating a CMP conditioner is that a surface of an abrasive layer changes to hydrophilic as CMP pad conditioning time increases. More specifically, the CMP conditioner is easily contaminated as CMP pad conditioning time increases since the surface of the abrasive layer of the CMP conditioner changes to hydrophilic. A hydrophilic surface on the abrasive layer of the CMP conditioner cannot reject water containing slurry as the CMP pad conditioning process proceeds. Such a problem is not limited to the CMP conditioner alone but may occur in cutting tools of wide meaning comprising abrasives which are used in cutting including cutting, grinding or polishing. 
         [0011]    The disclosed subject matter solves the aforementioned problems by providing a cutting tool, wherein deterioration of cutting performance due to agglomeration of an abrasive layer surface and contamination of the abrasive layer surface is greatly suppressed by improving hydrophobicity maintaining performance of an abrasive layer, and a manufacturing method of the cutting tool. 
         [0012]    According to one embodiment of the disclosed subject matter, there is provided a method of manufacturing a cutting tool, which comprises the steps of forming an abrasive layer on a substrate, the abrasive layer having abrasives bonded to a surface thereof; and coating the surface of the abrasive layer with a hydrophobic material film. 
         [0013]    In a preferred embodiment, the hydrophobic material film may be a self assembled molecular monolayer in which a tail group of molecules is hydrophobic. The coating step with the hydrophobic material film is preferably performed using a deposition process. At this time, a precursor used in the deposition process has molecules of which a tail group may be hydrophobic, preferably, a CF (fluorocarbon) group or CHF (fluorohydrocarbon) group. As the precursor, FOTS (fluorooctyltrichlorosilane), DDMS (dichlorodimethylsilane), FDA (perfluorodecanoic acid), FDTS (perfluorodecyltrichlorosilane), and OTS (octadecyltrichlorosilane) may be used. In addition, the deposition process using the precursor may include a V-SAM (vapor-SAM) process, an L-SAM (liquid-SAM) process, and a bulk polymerization process using plasma. 
         [0014]    The step of forming an abrasive layer may be performed using an Ni electrodeposition process or a brazing process. The cutting tool is preferably a CMP conditioner. However, the cutting tool is not limited thereto, but may be a cutting tool having a hydrophobic material film formed on a surface of the abrasive layer. 
         [0015]    According to another embodiment, there is provided a cutting tool, which comprises a substrate; an abrasive layer formed on the substrate, the abrasive layer having abrasives bonded to a surface thereof; and a hydrophobic material film formed on the surface of the abrasive layer. 
         [0016]    Preferably, the hydrophobic material film is a self assembled molecular monolayer in which a tail group of molecules is hydrophobic. More preferably, the self assembled molecular monolayer is formed by using a CF (fluorocarbon) group or CHF (fluorohydrocarbon) group as a precursor. 
         [0017]    According to the disclosed subject matter, accumulation of contaminants generated on an abrasive layer and performance deterioration of a cutting tool due to the accumulation of the contaminants are suppressed by a hydrophobic material film formed on a surface of the abrasive layer of the cutting tool. Particularly, contaminants on a CMP conditioner, that is a cutting tool used together with slurry in conditioning a CMP pad, may be effectively suppressed. Thus, it is possible to reduce defects such as scratches or particles generated on a processing surface of the wafer in a wafer polishing process using a CMP pad that is subjected to the CMP conditioning process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  shows optical microscope images illustrating a process in which a contamination level of a conventional cutting tool varies according to cutting time of the cutting tool. 
           [0019]      FIG. 2  shows a CMP conditioner illustrated as an embodiment of a cutting tool according to the disclosed subject matter. 
           [0020]      FIGS. 3 and 4  show optical microscope images illustrating a surface of a CMP conditioner after CMP pad conditioning process for 30 minutes and 60 minutes respectively, wherein the surface is coated with a hydrophobic material film. 
           [0021]      FIG. 5  shows optical microscope images illustrating a surface of a CMP conditioner not coated with hydrophobic material film after CMP pad conditioning process for 30 minutes. 
           [0022]      FIG. 6  is an optical microscope image showing a hydrophobicity (or hydrophilicity) test result of a CMP conditioner coated with a hydrophobic material film before a cutting process. 
           [0023]      FIG. 7  is an optical microscope image showing a hydrophobicity (or hydrophilicity) test result of a CMP conditioner not coated with a hydrophobic material film before a cutting process. 
           [0024]      FIG. 8  is an optical microscope image showing a hydrophobicity test result of a CMP conditioner coated with a hydrophobic material film after a cutting process. 
           [0025]      FIG. 9  is an optical microscope image showing a hydrophobicity test result of a CMP conditioner not coated with a hydrophobic material film after a cutting process. 
           [0026]      FIGS. 10 to 13  show optical microscope images illustrating a surface of CMP conditioner coated with a hydrophobic material film after CMP pad conditioning process for 20 hours under the same condition as in an actual working environment. 
           [0027]      FIGS. 14 to 17  show optical microscope illustrating a surface of CMP conditioner not coated with a hydrophobic material film after CMP pad conditioning process for 20 hours under the same condition as in an actual working environment. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    Hereinafter, a CMP conditioner, as an example of a cutting tool according to the present invention, will be described. The following embodiments are provided only for illustrative purposes so that those skilled in the art can fully understand the spirit of the disclosed subject matter. Therefore, the disclosed subject matter is not limited to the following embodiments but may be implemented in other forms. In the drawings, the widths, lengths, thicknesses and the like of elements may be exaggerated for convenience of illustration. Like reference numerals indicate like elements throughout the specification and drawings. 
         [0029]      FIG. 2  shows a CMP conditioner illustrated as an embodiment of a cutting tool according to the disclosed subject matter. Referring to  FIG. 2 , a CMP conditioner  1  comprises a substrate  10  and an abrasive layer  20 . The substrate  10  is made of a metallic material and has a generally disc-shaped structure. The abrasive layer  20  is formed on the substrate  10  and has a plurality of abrasives  21 . In this embodiment, the abrasive layer  20  is an Ni electrodeposition layer formed by being plated with Ni to hold the abrasives  21 , and the abrasives  21  protrude from a surface of the abrasive layer  20 . 
         [0030]    As illustrated from an enlarged view of  FIG. 2 , a hydrophobic material layer  30  is formed on the surface of the abrasive layer  20 . The hydrophobic material layer  30  is a film having a hydrophobic surface of which a surface contact angle to water is large, and the hydrophobic material layer  30  serves to prevent the surface of the abrasive layer  20  from tending to be hydrophilic according to an increase in use time of the CMP conditioner  1 . 
         [0031]    The hydrophobic material layer  30  is a coating film, which may be formed by a deposition process or other processes, and covers both the electrodeposition material and abrasives  21 . At this time, since the hydrophobic material layer  30  is a thin film with a thickness smaller than a protruding height of the abrasives  21 , the performance of the CMP conditioner  1  is not deteriorated although the hydrophobic material layer  30  is formed on the abrasives  21 . 
         [0032]    Although an extremely small portion of the hydrophobic material layer  30  formed on the abrasives  21  may be eliminated if using the CMP conditioner  1  in conditioning of a CMP pad, another large portion of the surface of the abrasive layer  20 , such as a surface of an electrodeposition material holding the abrasives  21 , can be always maintained at its position unless the abrasives  21  are removed or worn out. 
         [0033]    The hydrophobic material layer  30  is preferably formed as a self assembled molecular monolayer in which a tail group of molecules is hydrophobic. Hereinafter, one embodiment of the disclosed subject matter, in which a hydrophobic self assembled molecular monolayer is formed on the surface of the abrasive layer, will be described. 
         [0034]    A technique of forming a self assembled molecular monolayer (also referred to as self assembled monolayer), which is included in a nano technology, is a technique for changing surface properties of an arbitrary material by a nano-based micro thin film. The self assembled molecular monolayer comprises a head group reacting with a surface of an arbitrary material, a body for determining a length of the arbitrary material, and a tail group for determining the surface properties of the arbitrary material. When the tail group is hydrophobic, the surface properties of the self assembled molecular monolayer become hydrophobic. 
         [0035]    A process for vaporizing a material and depositing the vaporized material on a surface of an abrasive layer  20  of a CMP conditioner  1  is used in the present embodiment, and one exemplification of the process will be described in the following Embodiment 1. 
       Embodiment 1 
     Process of Forming Hydrophobic Material Film 
       [0036]    A hydrophobic material film including a self assembled molecular monolayer is deposited on a surface of an abrasive layer of the CMP conditioner by charging a CMP conditioner, on which a hydrophobic material film was not formed, into a process chamber. At this time, trichlorosilane with formula C 8 H 4 Cl 3 F 13 Si is used as a precursor for the hydrophobic material film. The deposition conditions were, preferably: a vacuum degree of 10 to 21 torr; a process temperature of 150° C.; and a reaction time of 10 minutes. 
         [0037]    Determining whether the hydrophobic material film is formed or not is confirmed through a contamination degree varying test and a hydrophobic (or hydrophilic) test during processing of the CMP conditioner. 
       Embodiment 2 
     Contamination Degree Varying Test (Slurry Agglomeration Varying Test) 
       [0038]    A process for conditioning an actual CMP pad is performed using the CMP conditioner that was subjected to the process of Embodiment 1, and the contamination degree of the CMP conditioner is inspected at time intervals of 30 minutes during the process. 
         [0039]    The CMP conditioning process is performed using distilled water at a slurry flow rate of preferably 200 ml/min, a rotational speed of 50 rpm of the CMP pad and conditioner and an applied pressure of 8.5 psi thereof. The foregoing conditions are conditions in which the applied pressure and the slurry flow rate was increased as compared with the actual CMP conditioning process in order to confirm the change in a contamination degree of the CMP pad for a short time. For reference, a contamination degree varying test performed under the same conditions as the CMP conditions at the actual working field is also described in Embodiment 5, which is described later. 
         [0040]      FIGS. 3 and 4  are optical microscopic images in which a surface of an abrasive layer of the CMP conditioner is photographed at magnifying powers of ×100, ×200, ×500, and ×1000 after performing the CMP conditioning process using a CMP conditioner for 30 and 60 minutes, respectively. 
         [0041]    As illustrated in  FIGS. 3 and 4 , it can be confirmed that a CMP conditioner in which a hydrophobic material film is formed on the surface of the abrasive layer according to the process of Embodiment 1 was hardly contaminated by the slurry except that a contamination area of approximately 5% is found. 
       Embodiment 3 
     Contamination Degree Varying Test (Slurry Agglomeration Varying Test) 
       [0042]    A CMP pad conditioning process is performed using a CMP conditioner that is not subjected to the process described in Embodiment 1, i.e., a CMP conditioner on which a hydrophobic material film was not formed. The contamination degree of the CMP conditioner according to Embodiment 3 is inspected at time intervals of 30 minutes during the process. Test conditions, except the CMP conditioner used in the test, are identical to those of Embodiment 2. The CMP conditioning process performed, as in Example 2, using distilled water at a preferred slurry flow rate of 200 ml/min, rotational speed of 50 rpm of the CMP pad and conditioner and applied pressure of 8.5 psi thereof. 
         [0043]      FIG. 5  shows optical microscopic images in which a surface of the CMP conditioner is photographed at magnifying powers of ×100, ×200, ×500, and ×1000 after performing the CMP conditioning process for 30 minutes. As illustrated in  FIG. 5 , it can be confirmed that a surface of an abrasive layer is contaminated by slurry. It can also be confirmed that accumulation of contamination by the slurry is greater as time goes by. It can be seen from the test results that contaminants are more accumulated from the slurry on the CMP conditioner not coated with a hydrophobic material film than on the CMP conditioner coated with a hydrophobic material film, as described with respect to Embodiment 4. 
       Embodiment 4 
     Hydrophobic Test (Hydrophilic Test) 
       [0044]      FIG. 6  shows an optical microscope image showing a hydrophobicity test result of a CMP conditioner coated with a hydrophobic material film The CMP conditioner of  FIG. 6  has a contact angle of preferably 110° or more.  FIG. 7  shows an optical microscope image showing a hydrophobicity test result of a CMP conditioner not coated with a hydrophobic material film. The CMP conditioner of  FIG. 7  has a contact angle approximately of 70°.  FIGS. 6 and 7  show hydrophobicity test results of the CMP conditioners before the CMP conditioning process is performed. 
         [0045]    Comparing  FIGS. 6 and 7  with each other, it can be seen that the CMP conditioner coated with the hydrophobic material film has a better hydrophobicity than the CMP conditioner not coated with the hydrophobic material film. Since the CMP conditioner coated with the hydrophobic material film has a larger contact angle than the CMP conditioner not coated with the hydrophobic material film, it is determined that the CMP conditioner coated with the hydrophobic material film has a better hydrophobicity than the CMP conditioner not coated with the hydrophobic material film. 
         [0046]      FIG. 8  shows an optical microscope image showing a hydrophobicity test result of the CMP conditioner after performing a CMP conditioning process using a CMP conditioner coated with a hydrophobic material film. The hydrophobicity test includes placing a water drop on the surface of the CMP conditioner to determine the hydrophobicity of the CMP conditioner. It can be seen in  FIG. 8 , there is not a large difference from  FIG. 6 , i.e., the image showing a hydrophobicity test result of the CMP conditioner before the CMP conditioning process is substantially similar to the image showing the CMP conditioner after the CMP conditioning process. This shows that hydrophobicity of a surface of the hydrophobic material film is substantially maintained even after the CMP conditioning process. 
         [0047]    On the contrary, it can be seen that a water drop cannot be found on the CMP conditioner not coated with the hydrophobic material film as shown in  FIG. 9 . This shows that the hydrophobicity of the CMP conditioner is lost while a CMP conditioning process is performed using the CMP conditioner. The result is that the CMP conditioner becomes hydrophilic. As a result, a measured contact angle of the CMP conditioner was less than 5°. 
       Embodiment 5 
     Contamination Degree Varying Test (Slurry Agglomeration Varying Test) 
       [0048]    A CMP pad conditioning process is performed for 20 hours under the same conditions as the actual labor site using a CMP conditioner according to Embodiment 1. The contamination degree of the CMP conditioner is inspected while performing the process. As compared with Embodiment 2, the CMP conditioning process is performed at greatly reduced slurry flow rate and pressure applied to the CMP pad. 
         [0049]    The CMP conditioning process is performed using preferably distilled water at a slurry flow rate of 60 ml/min, a rotational speed of 65 rpm of the CMP pad and conditioner, and an applied pressure of 0.63 psi thereof. The foregoing conditions are conditions in which the applied pressure was increased as compared with the actual CMP conditioning process in order to confirm the change in a contamination degree of the CMP pad for a short time. 
         [0050]      FIGS. 10 to 13  show optical microscopic images in which a surface of the CMP conditioner is photographed at magnifying powers of ×100, ×200, ×500, and ×1000, respectively, after performing the CMP conditioning process for 20 hours according to the foregoing conditions. 
         [0051]    It can be seen from the images in  FIGS. 10 to 13 , that the CMP conditioner is hardly contaminated by slurry. Therefore, under the test conditions of the present embodiment, a CMP conditioner coated with a hydrophobic material film is hardly contaminated, thus it can be assumed that in the actual process, the CMP conditioner coated with a hydrophobic material is also hardly contaminated, and such an effect is sustained for a long time. 
       Embodiment 6 
     Contamination Degree Varying Test (Slurry Agglomeration Varying Test) 
       [0052]    A process for conditioning an actual CMP pad is performed for 20 hours using a CMP conditioner that was not subjected to the process described in Embodiment 1, i.e., a CMP conditioner on which a hydrophobic material film is not formed. Test conditions are similar to those described in Embodiment 5. 
         [0053]      FIGS. 14 to 17  show optical microscopic images in which a surface of a CMP conditioner is photographed at magnifying powers of ×100, ×200, ×500, and ×1000, respectively, after performing the CMP conditioning process for 20 hours according to the foregoing conditions using a CMP conditioner without a hydrophobic material film. As can be seen from the images shown in  FIGS. 14 to 17 , it can be confirmed that the entire area on a surface of an abrasive layer was greatly contaminated by slurry. Therefore, it can be confirmed again that accumulation of contaminants by the slurry is more increased in the CMP conditioner not coated with a hydrophobic material film as compared with the CMP conditioner coated with a hydrophobic material film. 
         [0054]    Although a coating method of a hydrophobic material film using FOTS (fluorooctyltrichlorosilane) as a precursor has been described above, DDMS (dichlorodimethylsilane), FDA (perfluorodecanoic acid), FDTS (perfluorodecyltrichlorosilane), and OTS (octadecyltrichlorosilane) may be used as the precursor. Furthermore, the deposition process using the precursor may include a V-SAM (vapor-SAM) process, an L-SAM (liquid-SAM) process, and a bulk polymerization process using plasma. 
         [0055]    The various embodiments described above can be combined to provide further embodiments. All of the U.S. patents, U.S. patent application publications, U.S. patent application, foreign patents, foreign patent application and non-patent publications referred to in this specification and/or listed in the Application Data Sheet are incorporated herein by reference, in their entirety. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, application and publications to provide yet further embodiments. 
         [0056]    These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.