Abstract:
A method for cleaning a polishing tool capable of reliably removing deposited solidified abrasive and impurities and thereby capable of suppressing scratching of a polished object and reducing residual particles on the polished face of the polished object, comprising the steps of arranging with respect to the polishing tool a cleaning member provided with facing surfaces for forming clearances with cleaned surfaces of the polishing tool feeding a cleaning solution to clearances formed between the facing surfaces and the cleaned surfaces to form cleaning solution films, and cleaning the cleaned surfaces by rotating the polishing tool, the cleaning solution being fed to clearances between the cleaned surfaces and the facing surfaces through feed ports formed in the cleaning member and opened in the facing surfaces, and a polishing method and polishing apparatus using the same.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to method of cleaning a polishing tool used for flattening a variety of films, such as inter-layer insulation films, metal films, and polysilicon films, formed on, for example, a semiconductor wafer by chemical mechanical polishing and a polishing method and polishing apparatus using such a polishing tool. 
     2. Description of the Related Art 
     Along with the higher integration and use of multi-layer interconnections of semiconductor devices, the flattening of a variety of films, such as inter-layer insulation film, metal film, and polysilicon film, has become important in the process of production of a semiconductor device. As a technique for the flattening, a variety of means have been proposed, but in recent years, the chemical mechanical polishing (CMP) process is attracting attention, and a polishing apparatus for flattening by utilizing this has been developed. 
     An example of a polishing apparatus using the conventional CMP process is shown in FIG. 1. A polishing apparatus  301  shown in FIG. 1 has a main shaft spindle  303  for rotating a polishing tool  302  and a rotating table  304  for holding a wafer W. The table  304  is rotatably mounted on a slider  306  provided moveably in an X-axial direction along a rail  305  and rotated by a rotation driving means constituted by, for example, a motor, a pulley, and a belt. The main shaft spindle  303  is held moveably in a Z-axial direction and positioned at a target position in the Z-axial direction by a not illustrated drive mechanism. 
     In the polishing apparatus  301  having the above constitution, first, the wafer W is rotated at a predetermined speed, and a slurry is continuously fed as an abrasive from a slurry feeder (not illustrated) onto the wafer W. The slurry is obtained by mixing a very fine polishing abrasive, for example, silicon oxide, with a liquid such as an aqueous solution of potassium hydroxide. Next, the polishing tool  302  is rotated at a predetermined speed to position the wafer W and the polishing tool  302  in the X-axial and Z-axial directions so that the polishing tool  302  is located at a position where it contacts an outer circumferential portion of the wafer W. In this state, a surface of the wafer W and a polishing surface of the polishing tool  302  are in substantially a parallel state. 
     The polishing tool  302  is positioned in the Z-axial direction so as to obtain a predetermined depth of cut with respect to the wafer W. By this, a predetermined polishing pressure is generated between the polishing tool  302  and the wafer W. By movement of the wafer W in the X-axial direction with a predetermined speed pattern and by movement of the contact position between the polishing surface of the polishing tool  302  and the wafer W in this state, the entire surface of the wafer W is polished and the wafer W is flattened. 
     In the polishing apparatus  301 , at the time of discharge of the slurry onto the wafer W and the polishing of the wafer W, the slurry sometimes deposits on the polishing tool  302  and the periphery of its attachment portion and then adheres and solidifies. When the solidified slurry or the like drops from the polishing tool  302  during the polishing and enters into the space between a polished surface of the wafer W and the polishing surface of the polishing tool  302 , it acts as a giant abrasive. When polishing pressure is added to the polished surface of the wafer W through the polishing tool  302  and a polishing operation is carried out in this state, it will scratch the polished surface of the wafer W or cause particles to deposit on it. If more than a prescribed number of scratches or residual particles are generated on the polished surface of the wafer W after the polishing, the wafer W ends up becoming a defect. 
     Further, the polishing tool  302  of the polishing apparatus having the above constitution is formed by an independent foam member, for example, polyurethane foam. The polishing surface of the polishing tool  302  made of such a material is susceptible to a so-called clogged state where the reaction product generated at the time of polishing and the flaked off substance forming the polishing tool  302  enter into the foam member. When in the clogged state, stable polishing cannot be carried out, so it is necessary to dress the tool to remove the surface layer of the polishing surface of the polishing tool  302  in the clogged state to condition the polishing surface of the polishing tool  302 . The tool is dressed by shaving the polishing surface of the polishing tool  302  by a dresser with, for example, a diamond abrasive fixed thereto. When dressing the tool, part of the substance constituting the polishing tool  302  flaked from the polishing tool  302  and part of the substance constituting the dresser flaked from the dresser sometimes deposit on the polishing tool  302 . The deposited substances sometimes become a cause of scratching the wafer surface. 
     In order to prevent the scratching of the wafer surface mentioned above, conventionally, for example, pure water was discharged onto the polished surface of the wafer W before the polishing, the polishing tool  302  was moved downward in the Z-axial direction while rotating the same and brought into contact with the pure water layer resident on the wafer W, and the slurry and impurities deposited on the polishing tool  302  were thereby removed to a certain extent. 
     Further, for example, as shown in FIG. 2, a cleaning use spray nozzle  307  having discharge ports at several positions is disposed in the vicinity of the position just under the polishing tool  302  on the slider  306  moveable in the X-axial direction. The spray nozzle  307  is moved downward up to that vicinity of the polishing tool  302  while rotating immediately before the polishing operation or while standing by for the operation. By cleaning the surface of the polishing tool  302  by discharging pure water from the spray nozzle  307  at a point of time when the polishing tool  302  reaches a predetermined height, the slurry and the impurities deposited on the polishing tool  302  have been removed to a certain extent. 
     However, there are also cases where they deposit on the outer circumferential surface of the polishing tool  302  or the periphery of the attachment portion of the polishing tool  302  and adhere and solidify. It was difficult to sufficiently remove these solidified impurities by the methods mentioned above or the solidified slurry and impurities deposited on the polishing tool  302  were insufficiently removed in some cases. 
     Further, there is also a method of disposing a cleaning use brush directly contacting the polishing tool  302  to clean the polishing tool  302 , but there is the disadvantage that the solidified slurry and impurities remained inside or outside the cleaning use brush. These solidified slurry and impurities sometimes again are deposited on the polishing tool  302  at the time of the next cleaning and on. Further, if the cleaning use brush is brought into direct contact with the surface of the polishing tool  302 , it changes the shape of the polishing surface of the polishing tool  302  or the cleaning use brush gradually deteriorates. Further, it is advantageous for improving the polishing efficiency if an adequate amount of slurry is provided at the surface of the polishing tool  302 , but there is also the disadvantage that if the cleaning use brush is brought into direct contact with the surface of the polishing tool  302  to clean the same, even the useful slurry provided at the polishing tool  302  was scraped off. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a method for cleaning a polishing tool capable of reliably removing deposited solidified abrasive and impurities. 
     Another object of the present invention is to provide a polishing method capable of suppressing scratching of a polished object and capable of reducing residual particles on the polished surface of the polished object. 
     Still another object of the present invention is to provide a polishing apparatus capable of suppressing scratching of a polished object and capable of reducing residual particles on the polished surface of the polished object. 
     According to one aspect of the present invention, there is provided a cleaning method of a polishing tool for cleaning a rotatably held polishing tool, comprising: arranging with respect to the polishing tool a cleaning member having a facing surface forming a clearance with a cleaned surface of said polishing tool, feeding a cleaning solution to the clearance to form a cleaning solution film, and rotating the polishing tool to clean the cleaned surface. 
     According to a second aspect of the present invention, there is provided a cleaning method of a polishing tool for cleaning a rotatably held polishing tool, comprising: positioning a correction tool for correcting the polishing surface at a position enabling contact with the polishing surface of the polishing tool, positioning a cleaning member having a facing surface for forming a clearance with at least part of the polishing surface of the polishing tool, feeding a cleaning solution to the clearance to form a cleaning solution film, and rotating the polishing tool to correct the polishing surface while cleaning the cleaned surface. 
     According to a third aspect of the present invention, there is provided a polishing method for flattening a polished object by making the polishing surface of the rotating polishing tool face the polished surface of the rotating polished object and relatively moving the polished object and the polishing tool along a predetermined plane, comprising: positioning the polishing tool at a predetermined position with respect to a cleaning member provided with a facing surface for forming a clearance with the cleaning face of the polishing tool, feeding a cleaning solution to the clearance formed between the facing surface and the cleaned surface to form a cleaning solution film, rotating the polishing tool to clean the cleaned surface and polishing the polished object by using the cleaned polishing tool. 
     According to a fourth aspect of the present invention, there is provided a polishing apparatus comprising: a polishing means for flattening a polished object by a rotating polishing tool and a polishing tool cleaning means for cleaning the surface of the polishing tool, wherein the polishing tool cleaning means has a cleaning member having a facing surface for forming a clearance for forming a film of a cleaning solution with the cleaned surface of the rotating polishing tool and a cleaning solution feeding means for feeding the cleaning solution to the clearance. In the present invention, when the cleaning solution is fed to the clearance formed between the cleaned surface of the polishing tool and the facing surface of the cleaning use member, a film of the cleaning solution is formed between the cleaned surface and the facing surface. When the polishing tool is rotated in this state, the cleaned surface of the polishing tool and the facing surface of the cleaning use member relatively move, a shearing force acts upon the film of the cleaning solution due to the resistance between the cleaned surface of the polishing tool and the facing surface of the cleaning use member, and the shearing force acting upon this film of cleaning solution removes the solidified abrasive and impurities deposited on the cleaned surface of the polishing tool with a high efficiency. Further, by making the facing surface of the cleaning use member partially face the cleaned surface of the polishing tool, the solidified abrasive and impurities removed from the cleaned surface of the polishing tool and contained in the cleaning solution are discharged to the outside together with the cleaning solution from the clearance formed between the cleaned surface of the polishing tool and the facing surface of the cleaning use member and will not deposit again to the cleaned surface of the polishing tool. Further, in the present invention, by simultaneously correcting the polishing surface of the polishing tool by the correction tool together with the cleaning of the polishing tool, the cleaning solution deposited on the polishing surface of the polishing tool also cleans the correction tool. Further, in the present invention, by feeding the cleaning solution to the clearance formed between the cleaned surface of the polishing tool and the facing surface of the cleaning use member through the feed ports formed in the facing surface of the cleaning use member, a sufficient amount of the cleaning solution is stably fed to the clearance formed between the cleaned surface of the polishing tool and the facing surface of the cleaning use member and the film of the cleaning solution is stably formed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and features of the present invention will become clearer from the following description of the preferred embodiments given with reference to the attached drawings, wherein: 
     FIG. 1 is a view of an example of the configuration of a polishing apparatus; 
     FIG. 2 is a view of an example of a method for cleaning a polishing tool of the related art; 
     FIG. 3 is a view of the configuration of a polishing apparatus according to an embodiment of the present invention; 
     FIG. 4 is a view of the relationship between a wafer and a polishing tool at the time of polishing; 
     FIG. 5 is a view of a polishing tool cleaning portion  31  of FIG. 3 seen from above (Z-axial direction); 
     FIG. 6 is a view of the polishing tool cleaning portion  31  seen from a direction indicated by an arrow B in FIG. 5; 
     FIG. 7 is a side view of the polishing tool cleaning portion  31  seen from a polishing tool correction device  51  side; 
     FIG. 8 is a view of the states of the polishing tool at the time of cleaning and correction; 
     FIG. 9 is an enlarged sectional view of a portion in a circle K of FIG. 8; 
     FIG. 10 is a top view of a cleaning member according to a modification of the present invention; 
     FIG. 11 is a side view of the cleaning member shown in FIG. 10; and 
     FIG. 12 is a view of one side of the cleaning member shown in FIG.  10 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Below, an embodiment of the present invention will be explained in detail by referring to the drawings. FIG. 3 is a view of the configuration of the polishing apparatus according to an embodiment of the present invention. 
     A polishing apparatus  1  shown in FIG. 3 has a polishing head  4  held at a gate type column  2  vertically arranged on a reference surface (not illustrated), a polishing tool  8  rotatably held at the polishing head  4 , an X-axis table  55  provided beneath the polishing tool  8  in the Z-axial direction, a rotating table  61  for holding the wafer W provided on the X-axis table  55 , a polishing tool cleaning portion  31  provided on the X-axis table  55 , and a polishing tool correction device  51  provided on the X-axis table  55 . 
     The column  2  contains a Z-axis movement mechanism (not illustrated) for moving the polishing head  4  for holding the polishing tool  8  in the Z-axial direction, that is, the direction wherein the polishing tool  8  faces the wafer W, and it can move and position the polishing head  4  at any position in the Z-axial direction. Note that the Z-axis movement mechanism (not illustrated) is the moving means for relatively moving the polishing tool  8  in the direction facing the wafer W being polished. 
     The polishing head  4  contains a holding device for rotatably holding the main shaft  6  and a main shaft motor for rotating the main shaft  6 . The polishing tool  8  is fixed and fastened at the bottom end of the main shaft  6 . By this, the polishing head  4  rotates the polishing tool  8  at an intended speed. Further, the polishing head  4  is provided with a slurry feed nozzle  9  serving as the abrasive feeding means for feeding the slurry serving as the abrasive onto the wafer W serving as the polished object. This slurry feed nozzle  9  can feed the slurry fed from the slurry feeder (not illustrated) onto the polished face of the wafer W. 
     The slurry fed from the slurry feed nozzle  9  is not particularly limited, but for an oxide film, use can be made of, for example, one obtained by suspending a silica-based fumed silica and high purity ceria in an aqueous solution containing potassium hydroxide as the base or, for an interconnection metal, use can be made of one obtained by mixing a solvent having oxidizing power into a polishing solution containing alumina as the polishing abrasive. Further, the slurry feed nozzle  9  can also feed pure water onto the wafer W. 
     The polishing tool  8  is made of, for example, a cylindrical body and is provided with a ring-like polishing surface on one end. As the polishing tool  8 , use is made of, for example, one formed by an independent foam member made of a resin such as polyurethane foam. The rotating table  61  rotatably holds the wafer W and rotates the wafer W at the intended speed by the included driving means. The rotation axis of the rotating table  61  and the rotation axis of the polishing head  4  are substantially parallel, while the polished face of the wafer W and the polishing surface of the polishing tool  8  are parallel. The rotating table  61  is provided on the X-axis table  55 . This X-axis table  55  moves the polished face of the wafer W in the X-axial direction. Namely, the X-axis table  55  is the moving means for relatively moving the wafer W along a horizontal face with respect to the polishing tool  8 . 
     The wafer W is fixed and fastened at the rotating table  61  by a chucking means such as vacuum chucking. A variety of films, such as an inter-layer insulation film, metal film, or polysilicon film, are formed on a substrate made of, for example, silicon. These variety of films are flattened by the polishing apparatus of the present embodiment. Note that, the polishing means of the present invention is constituted by the polishing head  4 , Z-axis movement mechanism, polishing tool  8 , rotating table  61 , X-axis table  55 , and so on. 
     The polishing tool cleaning portion  31  is provided on the X-axis table  55  and cleans the surface of the polishing tool  8  by the cleaning solution fed from a cleaning solution feeder  41 . This polishing tool cleaning portion  31  is able to move to a predetermined position beneath the polishing tool  8  by the movement of the X-axis table  55 . Further, the polishing tool  8  is positioned at a predetermined position in the Z-axial direction by the Z-axis movement mechanism (not illustrated) contained in the column  2  with respect to the polishing tool cleaning portion  31  positioned at a predetermined position beneath the polishing tool  8 . 
     The polishing tool correction device  51  is provided adjoining the polishing tool cleaning portion  31  on the X-axis table  55 . This polishing tool correction device  51  is provided at its top end with a correction tool  52  for correcting the polishing surface of the polishing tool  8  and corrects the polishing surface of the polishing tool  8  by bringing the polishing surface of the rotating polishing tool  8  into contact with the correction face of the correction tool  52 . The correction face of the correction tool  52  is arranged along, for example, the horizontal face. By bringing the polishing surface of the rotating polishing tool  8  into contact with this, the polishing surface of the polishing tool  8  is corrected. As the correction tool  52 , use can be made of, for example, one forming a polishing surface by roughness on one face of a disk made of ceramic or one obtained by electrically fixing a diamond abrasive to one face of a disk made of stainless steel. 
     The correction of the polishing surface of the polishing tool  8  includes, for example, truing for shaping the polishing surface of the polishing tool  8  to its true shape and dimensions and dressing for correcting the polishing surface of the polishing tool  8  to a surface state having good cutting. The truing is mainly carried out at the time of replacement of the polishing tool  8  or in a case where the polishing tool  8  is not used for a long period of time. A relatively large amount of removal of, for example, about 0.1 mm to 0.3 mm becomes necessary for completely removing the initial shaping error or assembly error of the polishing tool  8  on the machine. The dressing is carried out, for example, for every wafer W or for every 10 wafers, for every 25 wafers, or for every 100 wafers. The layer causing clogging or abrasion of the polishing surface of the polishing tool  8  is removed with an amount of removal of about 2 to 10 μm. 
     Next, an explanation will be given of a basic polishing operation of the polishing apparatus. FIG. 4 is a view of an example of the relationship between the wafer W and the polishing tool  8  at the time of polishing by the polishing apparatus  1 . First, a rear surface of the wafer W is fixed to the top surface of the rotating table  61 , the rotating table  61  is made to rotate, and, as shown in FIG. 4, a slurry SL is discharged onto the wafer W at a constant rate. Note that the slurry SL is constantly supplemented in exactly the required amount at the time of polishing as well. 
     The polishing tool  8  held at the polishing head  4  is then moved downward in the Z-axial direction, whereby, as shown in FIG. 4, a state where a polishing start point P 1  of an outer circumferential portion of the wafer W and the outer circumferential portion of the polishing tool  8  are overlapped is exhibited. From this state, the wafer W and the polishing surface of the polishing tool  8  are brought into contact with each other while rotating in a substantially parallel state to start the polishing while applying a polishing pressure F shown in FIG. 3 to a direction vertical to the polished face of the wafer W. A rotation direction R 2  of the wafer W and a rotation direction R 1  of the polishing tool  8  are reverse to each other. The wafer W is moved from the polishing start point P 1  in a direction indicated by an arrow C wherein an overlap of the wafer W and the polishing tool  8  relatively increases with a predetermined speed pattern. By this, the polishing of the polished face of the wafer W is advanced toward a direction indicated by an arrow D. When the outer circumferential portion of the polishing tool  8  moves up to a polishing end point P 2  of the wafer W, the polishing of the polished face of the wafer W is terminated. 
     Next, an explanation will be made of the concrete configuration of the polishing tool cleaning portion  31 . FIG. 5 is a view of the polishing tool cleaning portion  31  of FIG. 3 seen from above (Z-axial direction); FIG. 6 is a view of the polishing tool cleaning portion  31  seen from a direction indicated by an arrow E in FIG. 5; and FIG. 7 is a side view of the polishing tool cleaning portion  31  seen from a dressing device  51  side. 
     As shown in FIG. 5 to FIG. 7, the polishing tool cleaning portion  31  has a plurality of (two) cleaning members  32 . These cleaning members  32  are arranged at symmetric positions with respect to the X-axis. Further, the cleaning member  32  is provided with a facing surface  34  facing a polishing surface  8   a  of the polishing tool  8  and a facing surface  33  facing an outer circumferential surface  8   b  of the polishing tool  8 . Note that, it is the state where the polishing tool  8  is positioned at a predetermined position with respect to the polishing tool cleaning portion  31 , that is, the X-axis table  55  is positioned at a predetermined position in the X-axial direction and the polishing tool  8  is positioned at a predetermined position in the Z-axial direction as indicated by a dotted line in FIG. 6 that the facing surfaces  34  and  33  of the cleaning member  32  face the polishing surface  8   a  and the outer circumferential surface  8   b  of the polishing tool  8 . 
     The facing surfaces  34  and  33  of the cleaning member  32  are formed so as to partially cover the polishing surface  8   a  and the outer circumferential surface  8   b  of the polishing tool  8 . Predetermined clearances are formed between the facing surfaces  34  and  33  of the cleaning member  32  and the polishing surface  8   a  and the outer circumferential surface  8   b  of the polishing tool  8 . The clearances between the facing surfaces  34  and  33  of the cleaning member  32  and the polishing surface  8   a  and the outer circumferential surface  8   b  of the polishing tool  8  are relatively fine clearances of, for example, about 2 mm or less. 
     The facing surface  34  of the cleaning member  32  is a flat surface substantially parallel to the polishing surface  8   a  of the polishing tool  8 , while the facing surface  33  is a curved surface curved along the outer circumferential surface  8   b  of the polishing tool  8 . Further, preferably the facing surfaces  33  and  34  are formed as rough surfaces by, for example, etching. 
     Note that the outer circumferential surface  8   b  of the polishing tool  8  has an arc shape, so the facing surface  33  is also an arc or a shape approximate to an arc. Further, the facing surface  34  and the facing surface  33  of the cleaning member  32  have a vertical position relationship and continue from each other. Further, the facing surface  34  of the cleaning member  32  has a width substantially equal to the width of the polishing surface  8   a  of the polishing tool  8  in a radial direction, and the facing surface  33  has a height substantially equal to the height of the polishing tool  8  in the direction of the rotation axis. 
     The cleaning member  32  is formed with a plurality of cleaning solution feed ports  36 . These cleaning solution feed ports  36  are opened in the facing surface  34  and the facing surface  33 . The cleaning solution feed ports  36  are connected to the cleaning solution feeder  41 . The cleaning solution fed from the cleaning solution feeder  41  is discharged from the facing surface  34  and the facing surface  33  through the cleaning solution feed ports  36 . The number of the cleaning solution feed ports  36  is not particularly limited, but preferably a certain number of cleaning solution feed ports are arranged in a dispersed manner in the facing surface  34  and the facing surface  33  from a viewpoint of forming a stable film of cleaning solution between the facing surface  34  and the facing surface  33  and the polishing surface  8   a  and the outer circumferential surface  8   b  of the polishing tool  8 . Note that the cleaning solution feeder  41  feeds, for example, pure water as the cleaning solution. 
     On the other hand, in an area on the X-axis table  55  where the two cleaning members  32  are not arranged, the correction device  51  is arranged. The correction tool  52  of the correction device  51  is arranged at a position where its correction face can contact the polishing surface  8   a  of the polishing tool  8  in a state where the polishing tool  8  is positioned at a predetermined position with respect to the polishing tool cleaning portion  31 . 
     Next, an explanation will be given of an example of the cleaning operation of the polishing tool in the polishing tool cleaning portion described above. After polishing the wafer W, the polishing tool  8  is, for example, in a state containing slurry SL or having solidified slurry SL and the impurities removed by polishing the wafer W, etc. deposited on it. In that state, the polishing tool  8  is rotated at a high speed. It is then raised in the Z-axial direction from the surface of the wafer W, then the X-axis table  55  is moved and the polishing tool cleaning portion  31  is positioned at a predetermined position beneath the polishing tool  8 . Then, the polishing tool  8  is moved downward in the Z-axial direction, and, for example, as shown in FIG. 8, positioned at a position where a predetermined clearance δ 2  is formed between the facing surface  34  of the cleaning member  32  of the polishing tool cleaning portion  31  and the polishing surface  8   a  of the polishing tool  8 . In this state, a predetermined clearance δ 1  is also formed between the outer circumferential surface  8   b  of the rotating polishing tool  8  and the facing surface  33  of the cleaning member  32 . 
     In this state, pure water is fed from the cleaning solution feed ports  36  of the facing surfaces  34  and  33  of the cleaning member  32  to the clearances δ 1  and δ 2 . Here, FIG. 9 is an enlarged sectional view of the portion inside the circle K of FIG.  8 . As shown in FIG. 9, pure water PW is fed through the cleaning solution feed ports  36  to the clearances δ 1  and δ 2  formed between the polishing surface  8   a  and the outer circumferential surface  8   b  of the polishing tool  8  and the facing surfaces  34  and  33  of the cleaning member  32 . At this time, since the surface tension of the pure water PW is relatively large and the clearances δ 1  and δ 2  are relatively small, pure water films WF are formed between the polishing surface  8   a  and the outer circumferential surface  8   b  of the polishing tool  8  and the facing surfaces  34  and  33  of the cleaning member  32 . These pure water films WF are formed not over the entire surfaces, but partially on the polishing surface  8   a  and the outer circumferential surface  8   b  of the polishing tool  8 . 
     Note that, in the present embodiment, the configuration was employed of feeding the pure water PW in the state of rotating the polishing tool  8 , but it is also possible even if the polishing tool is not rotating at the time of discharge of the pure water PW. Further, the configuration was employed of positioning the polishing tool  8  in the polishing tool cleaning portion  31  in the state where the pure water PW is discharged from the cleaning solution feed ports  36  of the facing surfaces  34  and  33  of the cleaning member  32 . 
     Upon formation of pure water films WF between the polishing surface  8   a  and the outer circumferential surface  8   b  of the polishing tool  8  and the facing surfaces  34  and  33  of the cleaning member  32 , a shearing force acts due to the resistance between the polishing surface  8   a  and the outer circumferential surface  8   b  of the polishing tool  8  and the facing surfaces  34  and  33  of the cleaning member  32 . This shearing force acting upon the pure water films WF is increased in comparison with a case of a smooth surface since the facing surfaces  34  and  33  of the cleaning member  32  are formed as rough faces. 
     Due to the action of the pure water films WF with this shearing force, the solidified slurry SL and impurities deposited on the polishing surface  8   a  and the outer circumferential surface  8   b  of the polishing tool  8  are flaked off and contained in the pure water films WF. Due to this action, the solidified slurry SL and impurities deposited on the polishing surface  8   a  and the outer circumferential surface  8   b  of the polishing tool  8  are removed with a high efficiency. 
     In the present embodiment, the facing surfaces  34  and  33  of the cleaning member  32  are not provided on the entire surfaces, but partially on the polishing surface  8   a  and the outer circumferential surface  8   b  of the polishing tool  8 . Therefore, the pure water PW containing the solidified slurry SL and impurities which had stuck to the polishing surface  8   a  and the outer circumferential surface  8   b  of the polishing tool  8  flows down from a position where the facing surfaces  34  and  33  of the cleaning member  32  end, that is, an end of the cleaning member  32 , that is, the ends of the facing surfaces  34  and  33  of the cleaning member  32  on a forward side of the rotation direction of the polishing tool  8  or the end portion on an inner circumferential side of the facing surface  34 . For this reason, the solidified slurry SL and impurities in the pure water films WF will not again deposit on the polishing surface  8   a  and the outer circumferential surface  8   b  of the polishing tool  8 . 
     On the other hand, the correction face of the correction tool  52  of the polishing tool correction device  51  contacts the polishing surface  8   a  of the polishing tool  8  and conditions the polishing surface  8   a  of the polishing tool  8 . At this time, due to the correction of the polishing surface  8   a  of the polishing tool  8  by the correction tool  52 , impurities comprised of the substance forming the polishing tool  8  and the substance forming the correction tool  52  are generated, but these impurities are flushed away by the pure water PW following the rotating polishing tool  8  and will not again deposit on the polishing surface  8   a  and the outer circumferential surface  8   b  of the polishing tool  8 . The polishing tool  8  is cleaned as described above, the polishing surface  8   a  is corrected, and then the tool is used for the polishing of the wafer W. 
     By polishing the wafer W by the polishing tool  8  cleaned and corrected in the polishing surface  8   a  as described above, scratches in the polished face of the wafer W can be suppressed and the number of residual particles decreased, so the product yield is improved. As a result, the grain size, concentration, etc. of the polishing abrasive contained in the slurry SL can be precisely controlled, and therefore the polishing quality is greatly improved. 
     Further, according to the present embodiment, the polishing surface  8   a  of the polishing tool  8  is corrected, so good polishing can be stably carried out. Further, according to the present embodiment, the correction tool  52  for correcting the polishing tool  8  can be simultaneously cleaned, and therefore scratches in the polished face of the wafer W can be suppressed, the number of residual particles decreased, and the product yield improved. 
     As described above, according to the present embodiment, by forming the pure water films WF between the surface of the polishing tool  8  and the facing surfaces and causing a shearing force to act upon the pure water films WF by the rotation of the polishing tool  8 , the substances deposited on the surface of the polishing tool  8  can be efficiently cleaned off by the action of the pure water films WF with the shearing force. 
     Further, according to the present embodiment, the facing surfaces of the cleaning member  32  are arranged at part of the surface of the surface of the polishing tool  8  to be cleaned, the polishing tool  8  is rotated to clean the entire surface of the cleaned surface, and the pure water PW serving as the cleaning solution containing the deposited substance flaked off from the surface of the polishing tool  8  therein is discharged from the clearances between the polishing tool  8  and the cleaning member  32 . At the same time, fresh pure water PW is continuously fed to the clearances between the polishing tool  8  and the cleaning member  32 . Therefore, the impurities will not deposit on the polishing tool  8  again, so the degree of cleanness of the surface of the polishing tool  8  is high. 
     Further, according to the present embodiment, the facing surfaces of the cleaning member  32  are arranged at part of the surface of the surface of the polishing tool  8  to be cleaned and the entire surface of the cleaned surface is cleaned by rotating the polishing tool  8 . The clearances between the surface of the polishing tool  8  and the facing surfaces of the cleaning member  32  are relatively fine, and therefore efficient cleaning becomes possible by feeding a small amount of pure water PW. 
     It is advantageous from the viewpoint of polishing efficiency when, for example the polishing tool  8  formed from the independent foam member contains slurry SL contains polishing and an adequate amount of slurry is contained at the surface layer portion of the polishing tool  8 , but in the present embodiment, the cleaning is not carried out by bringing a brush or the like in direct contact with the surface of the polishing tool  8 . Only the surface of the polishing tool  8  is cleaned by the pure water PW, and therefore the slurry SL impregnated inside the polishing tool  8  is not also removed, but is held inside the polishing tool  8 . Further, the brush or the like is not brought into direct contact with the surface of the polishing tool  8 , so deformation and deterioration of the surface of the polishing tool  8  can be suppressed. 
     In the present embodiment, the polishing tool  8  is cleaned by pure water after polishing by the polishing tool  8 , and therefore adhesion and solidification of slurry and other impurities deposited on the polishing tool  8  can be prevented. For this reason, the polishing tool  8  is free from deposits of adhered and solidified impurities and a sufficient cleaning effect is obtained even if the impurities are not directly physically scraped off by a means such as a brush. 
     Note that, in the present embodiment, the facing surface of the cleaning member  32  is not arranged with respect to the inner circumferential surface of the polishing tool  8 , but also the inner circumferential surface of the polishing tool  8  can also be cleaned by arranging the curved facing surface in the same way as the outer circumferential surface with respect to the inner circumferential surface of the polishing tool  8 . 
     In the present embodiment, an explanation was made of the case where the polishing surface  8   a  was also corrected together with the cleaning of the polishing tool  8 , but it is also possible if the polishing surface  8   a  is not corrected, only the polishing tool  8  is cleaned, and then the wafer W is polished. 
     In the present embodiment, the configuration was employed of providing a plurality of cleaning solution feed ports  36  in both of the facing surfaces  34  and  33  of the cleaning member  32 , but a configuration may also be employed of providing them in either one of the facing surfaces  34  and  33 . When the plurality of cleaning solution feed ports  36  is provided in only one of the facing surfaces  34  and  33 , the facing surfaces  34  and  33  continue from each other, the clearances between the polishing surface  8   a  and the outer circumferential surface  8   b  of the polishing tool  8  and the facing surfaces  34  and  33  are fine, and therefore it is possible to form the pure water films in both of the clearances between the polishing surface  8   a  and the outer circumferential surface  8   b  of the polishing tool  8  and the facing surfaces  34  and  33 . 
     In the present embodiment, the configuration was employed of discharging the pure water PW fed to the clearances between the surface of the polishing tool  8  and the facing surfaces  34  and  33  of the cleaning member  32  from the end portions of the cleaning members  32  by arranging a plurality of cleaning members  32  along a circumferential direction of the polishing tool  8  with spaces, that is, discontinuously arranging them; but the present invention is not limited to this configuration. 
     In the present embodiment, the configuration was employed of feeding the cleaning solution from the cleaning solution feed ports  36  formed in the cleaning members  32  and opened in the facing surfaces  34  and  33  to the clearances between the surface of the polishing tool  8  and the facing surfaces  34  and  33 , but it is also possible to employ a configuration providing, for example, a nozzle for feeding the cleaning solution separately from the cleaning member  32  and feeding the cleaning solution from the outside of the cleaning member  32  toward the clearances between the facing surfaces  34  and  33  and the surface of the polishing tool  8 . 
     It is also possible to employ a constitution of feeding the cleaning solution from the cleaning solution feed ports  36  formed in the cleaning member  32  and opened in the facing surfaces  34  and  33  to the clearance between the surface of the polishing tool  8  and the facing surfaces  34  and  33  and, at the same time, providing a nozzle for feeding the cleaning solution separately from the cleaning members  32  and feeding the cleaning solution from the outside of the cleaning members  32  toward the clearances between the facing surfaces  34  and  33  and the surface of the polishing tool  8 . 
     As the function of discharging the pure water PW fed to the clearances between the surface of the polishing tool  8  and the facing surfaces  34  and  33  of the cleaning member  32 , it is also possible to employ the configuration as shown in, for example, FIG. 10 to FIG.  12 . FIG. 10 is a top view of another example of the cleaning member, FIG. 11 is a side view of the cleaning member shown in FIG. 10, and FIG. 12 is a side view of one cleaning member between two cleaning members shown in FIG.  10 . 
     Between the two cleaning members  82  and  86  shown in FIG. 10 to FIG. 12, the cleaning member  82  is provided with only a facing surface  82   a  facing the polishing surface  8   a  of the polishing tool  8  and not provided with a facing surface facing the outer circumferential surface  8   b  of the polishing tool  8 . Further, as shown in FIG. 10, the cleaning member  82  is provided with a plurality of cleaning solution feed ports  83  opened in the facing surface  82   a . The cleaning solution, for example, pure water, is discharged from the cleaning solution feed ports  83 . The cleaning member  86  is provided with a facing surface  86   a  facing the polishing surface  8   a  of the polishing tool  8  and a facing surface  86   b  facing the outer circumferential surface  8   b  of the polishing tool  8 . Further, the cleaning member  86  is provided with a plurality of cleaning solution feed ports  87  opened in the facing surface  86   a  and the facing surface  86   b . The cleaning solution, for example, pure water, is discharged from the cleaning solution feed ports  87 . Further, a recess portion  88  is formed in a wall portion forming the facing surface  86   b  of the cleaning member  86 , except the portion for forming the cleaning solution feed  23  ports  87 . The cleaning member  82  is not provided with the facing surface facing the outer circumferential surface  8   b  of the polishing tool  8 , so it cannot clean the outer circumferential surface  8   b  of the polishing tool  8 , but the discharge of the cleaning solution fed to the clearance between the polishing surface  8   a  and the facing surface  82   a  becomes easy. The cleaning member  86  can clean both the polishing surface  8   a  and the outer circumferential surface  8   b  of the polishing tool  8 , and the cleaning solution fed to the clearance between the outer circumferential surface  8   b  of the polishing tool  8  and the facing surface  86   a  is discharged to the outside also from the recess portion  88 , and therefore it becomes easy to discharge the cleaning solution fed to the clearance between the outer circumferential surface  8   b  of the polishing tool  8  and the facing surface  86   b  of the cleaning member  86  to the outside. 
     As described above, according to the present invention, the scratching of the polished face of the polished object and the number of residual particles are reduced and thus the product yield can be improved. Further, according to the present invention, together with the cleaning of the polishing tool, the correction tool can be simultaneously cleaned. Therefore the scratching of the polished face of the polished object and the number of residual particles are reduced, so the product yield can be improved. Further, the correction tool can be cleaned as a byproduct of the cleaning of the polishing tool, so the cost merit is also high. 
     While the invention has been described with reference to a specific embodiment chosen for the purpose of illustration, it should be apparent that numerous modifications could be made thereto by those skilled in the art without departing from the basic concept and scope of the invention.