DIAMOND TOOLS Technical Field [1] The present invention relates to a diamond tool, and more particularly, to a diamond tool which prevents an object from partially wearing by bringing an entire surface of the diamond tool into contact with the object at a constant pressure and causes a quality of a surface of the object to be improved by polishing the object with a constant force when polishing the object. Background Art [2] Lately, rapid development in the field of semiconductor has also been made according to development of industry. As an example of the rapid development, in order to largely integrate semiconductors, chips have been manufactured in a wafer state through a multi-layer wiring for producing a large number of chips per unit area. In order to produce the chips uniformly, importance of a polishing process for wide planarization of a surface of a wafer has gathered strength. [3] The polishing process is generally a process for grinding or polishing a surface of a work piece, and particularly, for polishing a surface of an object with a diamond tool while ceramic abrasive and slurry solution for etching is supplied to the object. That is, a chemical mechanical polishing (hereinafter, CMP) process, in which a mechanical removal process and a chemical removal process are combined into a single process, has been improved. [4] The aforementioned CMP process is performed by moving a polishing pad and a wafer with respect to each other at a predetermined pressure with polishing liquid interposed between the polishing pad and the wafer. [5] Fig. 1 is a view showing an apparatus for use in a conventional CMP process. Figs. 2 and 3 are views showing configurations of the apparatus for use in the conventional CMP process and a conditioner of the apparatus, respectively. In the CMP process, the wafer is polished by means of a polishing apparatus 20 for a mechanical polishing function and slurry 15 of a chemical solvent for a chemical polishing function. [6] To this end, a wafer 10 mounted on a carrier head 22 is installed on a polishing pad 30. [7] In such a state, the slurry 15 is supplied onto the polishing pad 30, and the polishing pad 30 rotates. Further, the carrier head 22 rotates and revolves at the same time. Thus, the wafer 10 is pressed to the polishing pad 30 at a constant pressure in order to be polished. [8] The aforementioned wafer 10 is securely mounted to the carrier head 22 by surface tension or vacuum. A surface of the wafer 10 comes into contact with a surface of the polishing pad 30 by self weight of the carrier head 22 and the applied pressure force. [9] While the wafer 10 and the polishing pad 30 come into contact with each other as described above, the slurry 15 flows into a fine gap between the contact surfaces. Then, the mechanical and chemical polishing processes are simultaneously performed by means of abrasive particles contained in the slurry 15 and projections (not shown) formed on the surface of the polishing pad 30. [10] Here, in order to prevent damage of the wafer 10, the polishing pad 30 comprises a polyurethane pad, the surface of which are formed with a plurality of the fine projections. [11] Snce the pressure applied when the wafer 10 is polished is concentrated to the contact surfaces, the polishing pad 30 configured as described above has a relatively high surface removal rate. Thus, there is a problem in that a polishing performance de¬ teriorates because of wear of the surface projections on the polishing pad 30 or surface loading phenomena caused from polishing residues in pores between the projections. [12] The surface of the polishing pad 30 is reprocessed in order to reactivate the polishing performance of the polishing pad 30, the polishing efficiency of which de¬ teriorates. [13] A diamond tool to be used to this end is referred to as a conditioner, disk, or dresser, and generally comprises a tool including diamonds. [14] Referring to Fig. 1, for example, a conditioner 50 of the aforementioned diamond tool, in which a polishing whetstone 55 is coupled to a shank 52, is mounted to a chuck 51. The respective whetstone 55 and shank 52 are shaped in a circular disk. The circular disk shaped conditioner 50 fastened to a polishing apparatus (not shown) of the chuck 51 rotates, translates, or revolves, and at the same time, presses and polishes the polishing pad 30. The conditioner 50 may polish the wafer 10 and the surface of the polishing pad 30 at the same time. Preferably, the conditioner 50 may polish the surface of the polishing pad 30 separately from the polishing process of the wafer 10 for the uniform polishing. [15] The conditioner shaped in the circular disk is referred to as the circular disk shaped conditioner 50, which is distinguished from a bar shaped conditioner 60. [16] Referring to Figs. 2 and 3 which show perspective views of the apparatus for use in the conventional CMP process and the conditioner for use in the apparatus, re- spectively, the bar shaped conditioner 60 will be described as follows. [17] The bar shaped conditioner 60 comprises a whetstone 65 for polishing and a shank 62, which are shaped in a bar, and is fastened to a chuck mounted to a polishing apparatus (not shown). Thus, as shown in Fig. 3, the conditioner 60 conditions the surface of the polishing pad 30 while pivoting from side to side or orbiting. [18] The bar shaped conditioner 60 has a length for covering an entire surface of the polishing pad 30, so that the surface of the polishing pad 30 can be processed at once. According to dimensions or conditions of the polishing pad 30, the bar shaped conditioner 60 having a proper length is used. [19] The circular disk or bar shaped conditioners 50 and 60 should maintain planarity of the polishing pad 30, reactivate/maintain the pores of the surface of the polishing pad 30 uniformly, and not wear or polish the polishing pad 30 unnecessarily. The con¬ ditioners also should secure the functions that the surface of the polishing pad 30 is prevented from scratching due to removal of grits of the diamond tools and that the wafer 10 is prevented from being contaminated due to contaminant remained in the polishing pad 30. [20] Referring to Figs. 4 and 5 which show plan views showing conditioners as examples of diamond tools of a general polishing apparatus, in the conditioners 50 and 60, the whetstones 55 and 65, which are formed by mixing diamond particles 56 and 66 with bonds 57 and 67 and sintering the mixtures, are bonded to portions of the shanks 52 and 62 which are bodies of stainless steel. Alternatively, the diamond particles 56 and 66 may be bonded to portions of the shanks 52 and 62 by nickel elec¬ troplating or by a brazing or electrodepositing method with metal or alloy. [21] Fig. 6 is a sectional view showing grits bonded on shanks by (a) sintering, (b) elec¬ trodepositing, and (c) brazing methods. According to the sintering method as shown in Fig. 6 (a), the whetstones 55 and 65 are manufactured through press forming and sintering processes after the diamond particles 56 and 66 and the bonds 57 and 67 are previously mixed, positioned at outsides of shanks 52 and 62, and then, bonded to the outsides of the shanks 52 and 62 by brazing, laser welding, or the like. Further, according to the electrodepositing method as shown in Fig. 6 (b), the grits 56 and 66 are attached to the shanks 52 and 62 with the bonds 57 and 67 such as nickel by wet electroplating. According to the brazing method as shown in Fig. 6 (c), the grits are distributed after applying liquid paste which is a mixture of binder and metal as a bond to the shanks 52 and 62, and then, bonded to the shanks 52 and 62 at a high temperature. [22] The conditioners 50 and 60 configured as above should perform the polishing process uniformly with the entire surfaces thereof in contact with an object such as the polishing pad 30. However, as shown in Fig. 3, in a dressing process in which the bar shaped conditioner 60 of a rigid material such as a metal that would not elastically deformed in the bending direction is used, as a pressure is applied to a lower center portion of the polishing pad 30, the polishing pad 30 has nonuniform pressure dis¬ tribution in that the contact pressure is decreased according as a radius is increased while the contact pressure is high at the center of the polishing pad 30. As such, contrary to the circular disk shaped conditioner 50, since the higher pressure is applied at the center of the polishing pad 30 as compared with an outer peripheral portion, a partial wear phenomenon in which the degree of wear at the center of the polishing pad 30 is increased occurs in the bar shaped conditioner 60. [23] Therefore, in the polishing pad 30, a nonuniform wear phenomenon of the polished surface such as the partial wear phenomenon of the center portion occurs, as described above. There is a problem in that partial wear occurs at the center of the polishing pad 30. There is also a problem in that yield for general works is reduced since in the CMP process, polishing efficiency of the wafer is decreased and the necessary time for polishing is increased due to the partial wear of the polishing pad 30. [24] In order to solve the above problems, the bar shaped shank has been manufactured so as to have a predetermined curvature. However, since a wear amount of the whetstone 65 varies according to extent of use of the conditioner 60, the scheme for fundamentally solving the phenomenon that the whetstone 65 of the conditioner 60 nonuniformly wears has not been presented. Disclosure of Invention Technical Problem [25] The present invention is conceived to solve the aforementioned problems in the prior art. An object of the present invention is to provide a diamond tools of a polishing apparatus, wherein a target object can be uniformly polished by providing an elastic member for elastically urging the diamond tool to the object at uniform pressure to bring the diamond tool and the object into contact with each other throughout entire contact surfaces thereof, the surface of the object can also be uniformly and rapidly polished since the object is prevented from partially wearing out, polishing quality of the object can be improved, and yield can be increased. Technical Solution [26] According to the present invention for achieving the above objective, a diamond tool of a polishing apparatus, which comes into contact with an object and polishes a surface of the object. The diamond tool comprises a fastening member fastened to the polishing apparatus; shanks arranged on an upper side of the fastening member and comprising a plurality of pieces; whetstones bonded onto the shanks; and an elastic member installed between the fastening member and the shanks and applying pressure to the shanks elastically. [27] Here, the shanks comprising a plurality of pieces may be configured such that borders with the adjacent shanks are formed with an inclination. Also, the shanks may be integrally bonded to a connecting member. Preferably, the connecting member may be an elastic member which makes bending deformation possible. In addition, the whetstone may comprise diamond or cubic boron nitride grit. [28] Furthermore, the elastic member may comprise a spring, to which any one of plate, coil, ring, and dish shaped springs may be selectively applied according to its shape. Advantageous Effects [29] Snce the diamond tool according to the present invention is mounted with an elastic member which causes a whetstone in contact with an object to apply pressure to the object so as to bring the whetstone and the object into contact with each other elastically, the entire contact surfaces of the whetstone of the diamond tool and the object come into contact with each other at a uniform pressure. Thus, there are advantages in that it is possible to polish the object uniformly, to always polish a surface of the object uniformly and rapidly since the object is prevented from partially wearing, to improve polishing quality of the object, and to increase yield. Brief Description of the Drawings [30] Fig. 1 is a view showing an apparatus for use in a conventional CMP process; [31] Fig. 2 is a perspective view showing the apparatus for use in the conventional CMP process; [32] Fig. 3 is a perspective view showing a conditioner of the apparatus for use in the conventional CMP process; [33] Figs. 4 and 5 are plan views showing conditioners of a general polishing apparatus; [34] Fig. 6 is a sectional view showing grits bonded on shanks by sintering (a), elec- trodepositing (b), and brazing (c) methods; [35] Figs. 7 to 9 are perspective, plan and front views of a diamond tool of a polishing apparatus according to the present invention; [36] Fig. 10 is a front view of a modified example of the diamond tool of the polishing apparatus according to the present invention in which coil springs are used; and [37] Fig. 11 is a front view showing a diamond tool of a polishing apparatus according to another embodiment of the present invention. [38] <Explanation of Reference Numerals for Major Portions Shown in Drawings> [39] 110: diamond tool 111: fastening member [40] I l ia: fastening groove 112: shank [41] 114: plate shaped spring 115: whetstone [42] 116: polishing particle 117: bond [43] 118: connecting member 119: border [44] Best Mode for Carrying Out the Invention [45] Hereinafter, a conditioner as an example of a diamond tool of a polishing apparatus according to the present invention will be described with reference to the drawings. [46] Figs. 7 to 9 are perspective, plan and front views of the conditioner of the polishing apparatus according to the present invention. The conditioner of the polishing apparatus according to the present invention is used for erecting projections or removing foreign materials remained between the projections and forming the projections by polishing a surface of a polishing member. [47] To this end, a conditioner 110 of the polishing apparatus comprises whetstones 115 which come into contact with a polishing member or an object and shanks 112 to which the whetstones 115 are bonded, as shown in Figs. 7 to 9. In the whetstone 115, a plurality of polishing particles 116 and a bond 117 are bonded to each other by sintering, electrodepositing, brazing, and the like methods. In addition, the shanks 112 for use are generally formed of metal such as stainless steel or carbon steel. [48] Herein, it is previously made clear that in addition to diamond or c-BN(Cubic Boron Nitride), the polishing particle 116 generally includes alumina (Al O ) or silicon carbide (SC). [49] The respective shanks 112 described as above comprise a plurality of pieces which are separated from each other, and to each of which a whetstone 115 corresponding to each of the piece in shape is bonded. Herein, borders 119 of the whetstones 115 bonded to the pieces and the adjacent pieces of the shanks 112 may be formed in parallel, and preferably, may be formed in inclined parallel in order to polish the object continuously without boundaries on the surface of the object. [50] The shanks 112 comprising the plurality of the pieces are integrally bonded to each other by a connecting member 118. Here, the connecting member 118 is made of material comprising a plate spring as material having elasticity which makes bending deformation possible. [51] That is, the connecting member 118 supports the plurality of the shanks, while a bend occurs therein in the pressure direction when a pressure is applied. [52] Furthermore, an elastic member which applies pressure to the shank 112 elastically is fastened onto a lower side of the connecting member 118 so that the whetstone 115 comes into contact with the object elastically. The elastic member comprises a spring, and particularly, the spring consists of a plate shaped spring 114 in an embodiment of the present invention. [53] The aforementioned plate shaped spring 114 is fastened to both ends of the connecting member 118 by means of bolts B. In the meantime, a fastening member 111, in which a fastening groove I l ia fastened to a tool such as a polishing apparatus is formed, is arranged on a lower center of the plate shaped spring 114, and then fastened to the plate shaped spring 114 by means of bolts which are inserted into and pass through the fastening member 111 and nuts N. [54] In the conditioner 110 of the polishing apparatus having uniform extent of wear constructed as above, the spring may be formed in coil springs 124 as shown in Fig. 10 or springs having a variety of shapes including ring or dish shaped springs according to its shape, in addition to the plate shaped spring 114. [55] In addition, the connecting member 118 and the spring as the elastic member may be made of metal including steel and aluminum, or nonmetal having elasticity such as plastic and rubber. Further, it is possible to variously modify its shape in addition to material. As an example, although the connecting member 118 and the plate shaped spring 114 are formed in a plate of a single shape in the embodiment of the present invention, ends of the bending direction may be formed in an inwardly bent shape in order to increase a bending force or restoring force. [56] Fig. 11 is a front view showing a conditioner of a polishing apparatus according to another embodiment of the present invention. A conditioner 150 of the polishing apparatus according to this embodiment of the present invention is in the form that whetstones 155 are bonded to shanks 152 comprising a plurality of pieces. It is also possible to bond elastic members such as coil springs 154 to the respective shanks 152. [57] Embodiment 1 [58] Conditioning processes for semiconductor wafer polishing pad are performed by means of a conventional article and an article of the present invention while chemically polishing semiconductor wafers. Here, the number of the polished wafers amounts to 100. [59] A within wafer nonuniformity (WIWNU) for surfaces of the wafers is measured according to a formula using an ellipsometer after polishing. [60] MathFigure 1

WIWNU (%) = (maximum thickness - minimum thickness) / (2 x variation) x 100

[61] [62] Herein, the WIWNU of a small value means that an entire surface of the wafer is uniformly polished and that the pad for polishing the wafer is also uniformly conditioned. Measured values are shown in Table 1. [63] Table 1