JP2013208670A - Polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing pad capable of improving circulation ability and polishing performance of a polishing solution.SOLUTION: A polishing pad 10 includes a polishing layer 3 having a polishing surface Sp. The polishing layer 3 comprises four urethane sheets 2 apposed to one another in a circular form. The urethane sheet 2 is made of polyurethane resin by wet film forming technology, and has numerous foams 4 formed inside. Opening pores 5 comprising the foams 4 opened are formed on the polishing surface Sp. The foam 4 is formed to be vertically long in a thickness direction of the urethane sheet 2 such that a foam forming direction is inclined in a constant direction with respect to the thickness direction from the center in the thickness direction to the formation position of the opening pore 5. Inclination directions SD of the foams 4 on the adjacent urethane sheets 2 differ by 90 degrees so as to extend in an opposite direction to a rotation direction RD of the polishing pad 10 during polishing on the polishing layer 3. A polishing solution is likely to flow in/out of the foams 4 through the opening pores 5 during polishing.

Description

  The present invention relates to a polishing pad, and more particularly to a polishing pad having a polishing layer having a polishing surface for polishing an object to be polished.

  Conventionally, in an object to be polished such as bare silicon, a semiconductor device, a magnetic disk substrate or the like, grinding or polishing is performed in order to smooth the surface. In the polishing process, a polishing pad is usually used, and a polishing liquid (slurry) in which abrasive grains (polishing particles) are dispersed in an alkali solution or an acid solution is supplied. In order to improve the surface flatness, after a polishing process (primary polishing) is performed, a finishing polishing process (finish polishing) is further performed.

  For the polishing pad for finish polishing, a suede-like soft urethane sheet made of a urethane resin by a wet film forming method is usually used (see, for example, Patent Document 1). In the polishing pad using such a wet urethane sheet, the polishing process is performed while the slurry is held by the foamed structure. However, in the wet urethane sheet, the surface of the skin layer formed at the time of film formation is excellent in flatness, so that the flatness of the object to be polished can be improved. It becomes difficult to raise. Also, if the size of the aperture is small even if the skin layer is removed and the foam formed inside is opened, it is not easy to flow in and out of the slurry. There is a problem of causing damage to objects. In order to solve these problems, by making the foamed holes shallower than before and increasing the diameter of the pores, it is possible to facilitate the inflow and outflow of slurry, improve the polishing rate, and reduce the variation in polishing performance. A pad technology is disclosed (see Patent Document 2).

Japanese Patent No. 4659338 JP 2007-160474 A

  However, in the technique of Patent Document 2, although the diameter of the hole on the surface (polishing surface) of the polishing pad is increased, the slurry can easily flow in and out, and the polishing rate can be improved. Since it is large, the waviness of the object to be polished becomes large, and the surface quality deteriorates. In addition, when the hole diameter varies, the waviness of the object to be polished further increases, which causes a reduction in surface quality. Furthermore, since it becomes difficult to distribute the supplied slurry uniformly between the processing surface of the object to be polished (the surface to be polished) and the polishing surface of the polishing pad, the slurry exists unevenly on the processing surface. As a result, the object to be polished cannot be uniformly polished. Therefore, it is important to limit the aperture diameter to be small in order to reduce the waviness of the object to be polished. To improve the polishing rate, it is important to facilitate the flow of the slurry and improve the circulation. It becomes.

  An object of the present invention is to provide a polishing pad capable of improving the circulation property and polishing performance of a polishing liquid in view of the above-mentioned cases.

  In order to solve the above-described problems, the present invention provides a polishing pad having a polishing layer having a polishing surface for polishing an object to be polished, wherein the polishing layer has a large number of foams having a size over the entire thickness direction. Are formed on the polished surface, and the foam formation direction from the center of the foam in the thickness direction to the formation position of the openings is relative to the thickness direction. It is comprised by the some resin sheet inclined in the fixed direction, The said some resin sheet was juxtaposed so that the said foam formation direction might differ for every said resin sheet.

  In this case, the polishing layer can be configured by juxtaposing the resin sheets so that the foam formation direction of the resin sheets is in the direction opposite to the rotation direction during the polishing process. In addition, the polishing layer can be configured by juxtaposing the resin sheets so that the foam formation direction of the resin sheets is directed toward the center of the polishing surface. The polishing layer can be configured by juxtaposing the resin sheets so that the foam formation direction of the resin sheets is directed toward the outer edge of the polishing surface. Moreover, foaming can be made to have a smaller diameter from the thickness direction center part of a resin sheet to the formation part of a hole to the bottom part of the back surface side of a grinding | polishing surface. Foaming may be formed such that the foam formation direction from the center in the thickness direction to the bottom on the back side is along the thickness direction. At this time, the foaming is the same foaming in the cross section parallel to the back surface where the vertical line passing through the center of the hole formed in the cross section parallel to the polishing surface in the vicinity of the polishing surface intersects the cross section parallel to the back surface in the vicinity of the back surface. It is preferable to be located outside the hole formed by the above. The polishing layer can be composed of 4 to 10 resin sheets. A gap may be formed between the resin sheets constituting the polishing layer. Further, the resin sheet can be made of urethane resin.

  According to the present invention, since the foaming direction of many foams formed on the plurality of resin sheets constituting the polishing layer is inclined in a certain direction with respect to the thickness direction, the polishing pressure is reduced to the bottom of the foam during the polishing process. So that the polishing liquid that has flowed into the foam from the opening of the polishing surface easily flows out of the opening that is biased with respect to the bottom of the foam, and the direction of foam formation is different for each of the plurality of resin sheets Since they are juxtaposed, the outflowing polishing liquid is uniformly supplied between the polishing pad and the object to be polished, so that it is possible to improve the polishing performance by improving the circulation of the polishing liquid.

The polishing pad of 1st Embodiment to which this invention is applied is shown typically, (A) is a top view, (B) is bb sectional drawing of (A). It is process drawing which shows the outline of the manufacturing process of a polishing pad. The foaming formation state in the film-forming resin sheet produced by the wet film-forming method is shown schematically, (A) is a sectional view in the thickness direction of the film-forming resin sheet, and (B) is a- It is explanatory drawing which shows typically the positional relationship of the center of the hole each formed in the a cross section, bb cross section, and cc cross section. It is explanatory drawing which shows typically the grade of the inclination in the foaming formed in the urethane sheet which comprises a polishing pad. It is a top view which shows typically the cutting state when producing a urethane sheet from the film-forming resin sheet produced by the wet film-forming method. The polishing pad of 2nd Embodiment is shown typically, (A) is a top view, (B) is bb sectional drawing of (A). The polishing pad of 3rd Embodiment is shown typically, (A) is a top view, (B) is bb sectional drawing of (A). It is a top view which shows typically the state which formed the clearance gap between the urethane sheets which comprise a polishing pad. It is a top view which shows typically the polishing pad which formed and comprised two sides which pinch | interpose the vertex of a urethane sheet in the shape of a curve.

<First Embodiment>
Hereinafter, a first embodiment of a polishing pad to which the present invention is applied will be described with reference to the drawings.

(Constitution)
As shown in FIGS. 1A and 1B, the polishing pad 10 of the present embodiment includes a polishing layer 3 having a polishing surface Sp for polishing an object to be polished. The polishing layer 3 is constituted by four urethane sheets 2 as quarter-circular resin sheets juxtaposed in a circular shape. The urethane sheet 2 is made of a polyurethane resin by a wet film forming method.

  The urethane sheet 2 is formed in a state where a large number of foams 4 are dispersed substantially uniformly on the inner side (inside) of the polishing surface Sp. The foam 4 is vertically long and rounded in the thickness direction of the urethane sheet 2 and has a size over almost the entire thickness. In the urethane sheet 2, the skin layer formed with a thickness of about several μm near the surface is removed by buffing during wet film formation. For this reason, the foam 4 is opened and the aperture 5 is formed on the polished surface Sp. In the polyurethane resin between the foams 4, many small foams (not shown) smaller than the foams 4 are formed. The urethane sheet 2 has a continuous foam structure in which the foam 4 and the small foam communicate with each other in a mesh pattern, and the foam is formed in a continuous form.

  Foam 4 has a different formation state between the upper layer on the polishing surface Sp side from the central portion in the thickness direction of the urethane sheet 2 and the lower layer on the back surface (hereinafter referred to as back surface Sr) of the polishing surface Sp from the central portion in the thickness direction. ing. That is, the foam 4 is formed so that the hole diameter in the upper layer is smaller than the hole diameter in the lower layer. In other words, the foam 4 is formed such that the volume in the lower layer is larger than the volume in the upper layer. The foam 4 is formed such that the foam formation direction from the central portion in the thickness direction in the upper layer to the position where the opening 5 is formed is uniformly inclined in a constant direction with respect to the thickness direction. The foam formation direction from the center in the direction to the foam end (bottom) on the back Sr side is formed along the thickness direction. In other words, the foam formation direction of the foam 4 is along the direction inclined with respect to the thickness direction in the upper layer (arrow UD direction in FIG. 1B), and in the thickness direction (arrow BD direction) in the lower layer. Along.

  The four urethane sheets 2 constituting the polishing layer 3 are juxtaposed so that the inclination directions of the foams 4 are different. That is, as shown in FIG. 1A, in each urethane sheet 2, the direction from the center in the thickness direction toward the opening 5 (arrow SD direction, hereinafter abbreviated as the inclination direction SD) is adjacent. Are juxtaposed at 90 degrees. In other words, in the polishing layer 3, the inclination direction SD of the foam 4 in each urethane sheet 2 is the rotation direction of the polishing pad 10 during the polishing process (arrow RD direction, hereinafter abbreviated as the rotation direction RD). The four urethane sheets 2 are arranged side by side so as to face in the opposite direction.

  In addition, the polishing pad 10 is bonded to the back surface Sr side of the urethane sheet 2 via an adhesive (not shown). For the base material 7, for example, a flexible film such as a film made of polyethylene terephthalate (hereinafter abbreviated as PET) is used. As the adhesive, an acrylic, urethane, epoxy, or other adhesive can be used. In this example, an acrylic adhesive is used. One side of the base material 7 is bonded to the urethane sheet 2 via an adhesive, and the other side of the base material 7 (the side opposite to the urethane sheet 2) is a double side for mounting the polishing pad 10 on the polishing machine. One side of the tape 8 is bonded. The double-sided tape 8 has a base material (not shown), and a pressure-sensitive adhesive layer (not shown) such as an acrylic pressure-sensitive adhesive is formed on both surfaces of the base material. On the other surface side of the double-sided tape 8 bonded to the other surface side of the base material 7, the surface of the pressure-sensitive adhesive layer is covered with release paper (not shown).

(Manufacturing)
The polishing pad 10 is manufactured by bonding the urethane sheet 2 produced and cut by a wet film forming method and the double-sided tape 8. That is, as shown in FIG. 2, a preparation step for preparing a resin solution in which a polyurethane resin is dissolved, a resin solution is applied to a film-forming substrate, and the resin solution is solidified in a coagulating liquid to form a sheet-like polyurethane resin. A sheet forming process to be formed, a cleaning / drying process for cleaning and drying the sheet-like polyurethane resin, a buffing process for uniforming the thickness by buffing the skin layer side, and producing a urethane sheet 2 by cutting into a quarter circle The polishing pad 10 is manufactured through a cutting process and a bonding process in which the obtained urethane sheet 2 and the double-sided tape 8 are bonded together. Hereinafter, it demonstrates in order of a process.

  In the preparation step, the polyurethane resin is dissolved by mixing the polyurethane resin, a water-miscible organic solvent capable of dissolving the polyurethane resin, and an additive. Examples of the organic solvent include N, N-dimethylformamide (hereinafter abbreviated as DMF) and N, N-dimethylacetamide (DMAc). In this example, DMF is used. The polyurethane resin can be selected from resins such as polyester, polyether and polycarbonate. Considering the formation of the foamed structure described above, a resin solution in which a polyurethane resin is dissolved in DMF at 20% by weight has a viscosity of 3 to 10 Pa · s measured at 25 ° C. using a B-type rotational viscometer. It is desirable to select and use a resin having a range, preferably 3 to 6 Pa · s. This polyurethane resin is dissolved in DMF so as to be in the range of 10 to 30% by weight, preferably in the range of 15 to 25% by weight. Since the viscosity of the resin solution depends on the molecular structure as well as the concentration and molecular weight of the polyurethane resin to be used, it is important to select the polyurethane resin, set the concentration, etc. in consideration of these comprehensively.

  In addition, as an additive, a pigment such as carbon black, a hydrophilic additive, a hydrophobic additive, or the like is used in order to control the size and amount (number) of foam 4 and the formation of an inclined foam in the upper layer. Can do. For these additives, various commonly used materials can be used. The obtained solution is degassed under reduced pressure to obtain a resin solution.

  In the sheet forming step, the resin solution obtained in the preparation step is applied substantially uniformly in a sheet shape to the belt-shaped film forming substrate at a normal temperature by a coating device such as a knife coater. At this time, the application thickness (application amount) of the resin solution is adjusted by adjusting the gap (clearance) between the knife coater and the film forming substrate. In this example, the clearance is adjusted so that the coating thickness is in the range of 0.8 to 1.2 mm. As the film forming substrate, a resin film, a fabric, a nonwoven fabric, or the like can be used. In this example, a PET film is used.

  The resin solution applied to the film forming substrate is continuously guided into a coagulating liquid (water-based coagulating liquid) whose main component is water, which is a poor solvent for the polyurethane resin. In order to adjust the regeneration speed of the polyurethane resin, an organic solvent such as DMF or a polar solvent other than DMF may be added to the coagulation liquid. In this example, water is used. In this example, the temperature of the coagulation liquid is set to 15 to 20 ° C. In the coagulation liquid, first, a film is formed at the interface between the resin solution and the coagulation liquid, and a skin layer is formed in the polyurethane resin immediately adjacent to the film. Thereafter, regeneration of the polyurethane resin having a continuous foamed structure proceeds by a cooperative phenomenon of diffusion of DMF in the resin solution into the coagulating liquid and penetration of water into the polyurethane resin. At this time, since the PET film of the film forming substrate does not permeate the coagulation liquid, the substitution of DMF and water occurs on the skin layer side, and the foam 4 is formed on the film forming substrate side larger than the skin layer side. A resin sheet is produced.

  Here, the foam formation associated with the regeneration of the polyurethane resin will be described. Since the cohesive force of the polyurethane resin increases, the regeneration proceeds rapidly in the polyurethane resin closest to the film, and a skin layer is formed. In this example, only water is used for the coagulation liquid, and the temperature of the coagulation liquid is set to a relatively low temperature of 15 to 20 ° C. For this reason, since the resin solution rapidly solidifies at a portion in contact with water and a dense skin layer is formed on the surface, mutual diffusion between water and DMF is suppressed. On the other hand, since the concentration of the polyurethane resin is adjusted to a range of 10 to 30% by weight, the coagulation speed becomes slow. Accordingly, the amount of water penetrating into the resin solution is reduced, and the regeneration of the polyurethane resin proceeds slowly. Moreover, the viscosity of the resin solution is adjusted in the range of 3 to 10 Pa · s. For this reason, the difference in viscosity between the skin layer side that is first regenerated in the coagulation liquid and the incompletely regenerated film-forming substrate side is increased so that the foam 4 in the upper layer is inclined. Is done. Furthermore, by removing the solvent from the DMF resin solution, that is, by replacing DMF with water, the formation of foam 4 and small foam proceeds, and the foam 4 and the small foam communicate in a network.

  Further, the resin solution applied to the film forming substrate is continuously guided into the coagulation liquid. At this time, the conveyance speed of the resin solution (film formation substrate) in the coagulation liquid is set to 1 to 10 m / min. By adjusting the conveyance speed, the foam 4 is easily formed on the upper layer side so as to be inclined forward with respect to the traveling direction of the film forming substrate. In other words, the foam 4 in the upper layer is formed by the direction of foam formation up to the foam end on the skin layer side with respect to the thickness direction of the film-forming substrate, that is, the polyurethane resin regenerated on the film-forming substrate. It is formed so as to be inclined in the longitudinal direction. Further, the foam 4 is formed so as to be along the vertical direction, that is, the thickness direction when viewed from the cross section in the width direction intersecting the longitudinal direction of the polyurethane resin. In other words, the foam 4 is formed so as to be uniformly inclined in a certain direction with respect to the thickness direction in the upper layer, and is formed along the thickness direction in the lower layer. In addition, since the polyurethane resin is regenerated on the film formation substrate, the opening of the foam 4 is not formed on the back surface Sr formed in contact with the surface of the film formation substrate.

  As shown in FIGS. 3 (A) and 3 (B), the produced film-formed resin sheet 20 is formed so that the foam 4 is inclined in the upper layer. The vertical line passing through the center of the hole formed by the foam 4 in the parallel cross section is formed by the same foam 4 in the cross section parallel to the back surface Sr at the position where the vertical line in the vicinity of the back surface Sr opposite the skin layer intersects the back surface Sr. Located outside the perforated hole. That is, as shown in FIG. 3 (A), a position about 50 to 100 μm from the surface in the vicinity of the surface (position of arrow a), a position of the central portion in the thickness direction of the film forming resin sheet 20 (position of arrow b) In addition, a position about 50 to 100 μm from the back surface Sr in the vicinity of the back surface Sr (a position indicated by an arrow c). In this case, as shown in FIG. 3B, a hole Ha at the center Ma is formed by the foam 4 in the aa cross section near the surface. Similarly, a hole Hb of the center Mb is formed by the same foam 4 in the bb cross section at the center in the thickness direction of the film-forming resin sheet 20, and a hole Hc of the center Mc is formed by the same foam 4 in the cc cross section near the back surface Sr. Is formed. The center Ma of the hole Ha, the center Mb of the hole Hb, and the center Mc of the hole Hc are not aligned in the thickness direction and are located at a shifted position. That is, the vertical line L passing through the center Ma of the hole Ha intersects the cc cross section at the intersection Q. For this reason, the intersection point Q is located outside the hole Hc. Further, when the radius of the hole Hc is Rc, and the distance between the center Mc of the hole Hc and the intersection Q is Lc, the distance Lc is 2 to 5 times the radius Rc.

  Next, the degree of inclination of the foam 4 formed on the film-formed resin sheet 20, that is, the urethane sheet 2 obtained after buffing and cutting will be described. As shown in FIG. 4, in the cross section in the thickness direction along the longitudinal direction of the film-forming resin sheet 20, foaming is performed on a cross section parallel to the skin layer surface at the center in the thickness direction (see the bb cross section in FIG. 3B). 4, a hole at the center M1 is formed. A straight line in the direction (left and right direction in FIG. 4) perpendicular to the thickness direction (vertical direction in FIG. 4) passing through the center M1, and a straight line in the thickness direction of the film-forming resin sheet 20 through the vertex M2 on the skin layer side of the foam 4 If the intersection point with P is P, a right-angled triangle is formed with the line segment connecting the center M1 and the vertex M2 as the hypotenuse. In this right triangle, an elevation angle θ is formed when the vertex M2 is viewed from the center M1. In the upper layer of the film-forming resin sheet 20, the foam 4 is formed so that the elevation angle θ is in the range of 10 to 80 degrees. In this case, when the length of the line segment connecting the center M1 and the intersection point P is x and the length of the line segment connecting the vertex M2 and the intersection point P is y, tan θ = y / x is 0.18˜ The range is 5.67. Here, the elevation angle θ is obtained by taking a non-destructive photograph of an internal cross-section of the film-forming resin sheet 20 using a three-dimensional measurement X-ray CT, and positioning the center M1 and the vertex M2 with an image analyzer. Value. In a simple manner, the elevation angle θ can be calculated by taking a cross section in the thickness direction along the longitudinal direction during wet film formation with a scanning electron microscope and determining the center M1 and the vertex M2.

  As shown in FIG. 2, in the washing / drying step, the film-forming resin sheet 20 obtained in the sheet forming step is washed in a washing liquid such as water to remove DMF remaining in the polyurethane resin, and then dried. In this example, a cylinder dryer having a cylinder having a heat source is used for drying the film-formed resin sheet 20. The film-forming resin sheet 20 is dried by passing along the peripheral surface of the cylinder. The dried resin film 20 is wound up into a roll.

  In the buffing process, a buffing process is performed on the surface side of the skin layer in the film-formed resin sheet 20 after drying. In the film-forming resin sheet 20 wound up in a roll shape, thickness variation occurs during film formation. By pressing the surface of the pressure roller having a flat surface against the back surface Sr opposite to the skin layer, irregularities appear on the skin layer surface side. Unevenness appearing on the surface side of the skin layer is removed by buffing. In this example, since the continuously formed film-forming resin sheet 20 is strip-shaped, the skin layer side is continuously buffed while pressing the pressing roller against the back surface Sr. Thus, the film-forming resin sheet 20 that has been buffed to form the flat polished surface Sp is free from variations in thickness, and the opening 5 is formed in the polished surface Sp. In addition, in the single-piece | unit of the film-forming resin sheet 20, the unevenness | corrugation from which the thickness of the film-forming resin sheet 20 becomes uniform is exhibited on both surfaces, and by attaching the base material 7 or attaching it to a polishing machine as described later. The polished surface Sp becomes flat.

  In the cutting step, first, the base material 7 is bonded to the film-formed resin sheet 20 after the buffing process via an adhesive. Next, as shown in FIG. 5, the fan-shaped urethane sheet 2 having a quarter circle shape, that is, a central angle of 90 degrees is cut from the film-forming resin sheet 20 to which the base material 7 is bonded. As described above, the film-forming resin sheet 20 has the foam 4 inclined toward the front side in the traveling direction (arrow CD direction, hereinafter abbreviated as the traveling direction CD) in the sheet forming step. That is, the traveling direction CD is the inclination direction SD of the foam 4. The urethane sheet 2 is obtained by cutting so that the fan-shaped apex portion is located on one side in the width direction of the film-forming resin sheet 20 and the fan-shaped arc portion is located on the other side. It is done. In FIG. 5, the interval between the urethane sheets 2 is shown large for easy understanding, but it is preferable to reduce the interval as much as possible in order to improve the manufacturing yield.

  As shown in FIG. 2, in the bonding process, the urethane sheet 2 bonded and cut in the cutting process and the double-sided tape 8 are bonded together. That is, the base material 7 bonded to the back surface Sr of the urethane sheet 2 and the double-sided tape 8 are bonded so that the four urethane sheets 2 are juxtaposed in a circular shape. At this time, the urethane sheets 2 are juxtaposed on one double-sided tape 8 so that no gap is formed between the adjacent urethane sheets 2, and the double-sided tape 8 is cut out in accordance with the outer periphery of the circular polishing layer 3. . As described above, the inclination direction SD of the foam 4 is the same as the traveling direction CD of the film forming resin sheet 20, and cutting is performed so that the apex portion of the urethane sheet 2 is positioned on one side in the width direction of the film forming resin sheet 20. By arranging the urethane sheets 2 side by side in a circular shape, the inclination direction SD is different for each urethane sheet 2. Then, the polishing pad 10 is completed by performing an inspection such as confirming that there is no adhesion of scratches, dirt, foreign matter, and the like.

  When polishing an object to be polished using the obtained polishing pad 10, for example, the polishing pad 10 is mounted on each of two surface plates disposed opposite to each other of a double-side polishing machine. When the polishing pad 10 is mounted, the release paper is removed and the adhesive pad of the double-sided tape 8 exposed is applied. In the polishing pad 10 affixed to the two surface plates, the polishing surface Sp is substantially flat in both cases. An object to be polished is sandwiched between two surface plates, and at least one surface plate is rotated, whereby both surfaces of the object to be polished sandwiched between two polishing pads 10 are simultaneously polished. At this time, a polishing pressure is applied to the object to be polished, and a polishing liquid (slurry) containing abrasive particles is supplied.

  Next, the operation and the like of the polishing pad 10 of the present embodiment will be described. To make the description easier to understand, first, a polishing pad using a urethane sheet produced by a conventional wet film forming method will be described. In a urethane sheet constituting a conventional polishing pad, a large number of foams are formed over the entire thickness of the urethane sheet during wet film formation, but the foams are formed in the vertical direction along the thickness direction. For this reason, in the conventional urethane sheet, the cross section where the vertical line passing through the center of the hole formed by foaming in the cross section parallel to the polishing surface in the vicinity of the polishing surface intersects the cross section parallel to the back surface in the vicinity of the back surface (See also FIG. 3). In the conventional polishing pad using such a urethane sheet, the polishing process is performed while holding the slurry by the foam structure, but it is difficult to raise the polishing rate, and it is not easy for the slurry to flow into and out of the foam. Therefore, the polishing pad is easily clogged, and the object to be polished may be damaged. That is, during polishing, the object to be polished is positioned so as to block the opening of the polishing surface, so that the slurry is difficult to flow into the foam from the opening, and even if the bottom of the foam is pressed by the polishing pressure, the inflow This makes it difficult for the slurry to flow out of the opening. Shallow foaming and increasing the hole diameter can improve the inflow and outflow of the slurry and improve the polishing rate. However, the larger the hole diameter, the larger the swell of the workpiece. The quality will deteriorate. Further, if the hole diameter varies, the waviness of the object to be polished further increases. Furthermore, since it becomes difficult to distribute the supplied slurry uniformly between the object to be polished and the polishing pad, the slurry exists non-uniformly on the processed surface of the object to be polished, and the object to be polished is made uniform. It becomes impossible to polish. The present embodiment is a polishing pad 10 that can solve these problems.

  In the polishing pad 10 of the present embodiment, four urethane sheets 2 constituting the foam layer 3 are juxtaposed in a circular shape, and the formation direction of the foam 4 in each urethane sheet 2 is inclined in a certain direction with respect to the thickness direction. doing. In this polishing layer 3, the urethane sheets 2 are juxtaposed so that the inclination direction SD from the central portion in the thickness direction of the foam 4 to the opening 5 is opposite to the rotation direction RD of the polishing pad 10 during polishing. (See FIG. 1A). That is, the position of the opening 5 formed in the polishing surface Sp is deviated from the position on the bottom side of the foam 4. For this reason, at the time of polishing, the slurry easily flows into the foam 4 from the opening 5, and when polishing pressure is applied, the slurry in the foam 4 is opened at a position deviated from the position on the bottom side of the foam 4. It becomes easy to flow out of the hole 5. Thereby, since the slurry is effectively supplied between the object to be polished and the polishing pad, the circulation of the slurry can be improved, and the polishing rate can be improved.

  Further, in the present embodiment, the elevation angle θ when the vertex M2 is viewed from the center M1 in the right triangle having the hypotenuse as the line segment connecting the center M1 and the vertex M2 in the foam 4 is in the range of 10 to 80 degrees, that is, tan θ. The foam 4 is formed so as to be in the range of 0.18 to 5.67 (see FIG. 4). For this reason, when a polishing pressure is applied, local stress on the polishing surface Sp is relieved by the plurality of foams 4 formed close to each other on the lower layer side, so that stress unevenness on the object to be polished is reduced. be able to. Thereby, the pressing force on the object to be polished is equalized, so that the flatness accuracy can be improved. In consideration of improving the in-plane uniformity of the object to be polished, the foam 4 is formed so that the elevation angle θ is in the range of 30 to 60 degrees, that is, the tan θ is in the range of 0.58 to 1.73. Preferably it is formed.

  Further, in the present embodiment, the foam 4 is formed such that the volume in the lower layer is larger than the volume in the upper layer. For this reason, it becomes easy to store the slurry at the time of polishing, and if a polishing pressure is applied, a pressing force is easily applied to the foamed bottom portion on the lower layer side, and the slurry can be efficiently pushed out toward the opening 5. Thereby, the circulation property of the slurry can be improved. Moreover, since the hole diameter in the lower layer is formed large, cushioning properties can be exhibited by the polishing pressure during polishing. Further, since the foam 4 is formed so as to be inclined at the upper layer, the pressing force on the object to be polished is equalized. Therefore, since the circulation property of the slurry is improved and the pressing force against the object to be polished is equalized, it is possible to improve the flatness of the object to be polished while ensuring the flatness of the polishing surface Sp.

Second Embodiment
Next, a second embodiment to which the present invention is applied will be described. In the following embodiments, the same members as those in the first embodiment are denoted by the same reference numerals, description thereof is omitted, and only different portions will be described. In this embodiment, each urethane sheet 2 is juxtaposed so that the inclination direction SD of the foam 4 in each urethane sheet 2 is directed toward the center direction of the polishing surface Sp, and the polishing layer 3 is configured. It is as follows.

  As shown in FIGS. 6A and 6B, in the polishing pad 10 of the present embodiment, the polishing layer 3 has the inclined direction SD of the foam 4 in the four urethane sheets 2 directed toward the center of the polishing surface Sp. It is configured as follows. At the time of manufacturing such a polishing pad 10, in the cutting process, four quarter-circle urethane sheets 2 are cut from the film-forming resin sheet 20, but the film-forming resin sheet 20 in the traveling direction CD in the sheet-forming process is cut. Cut so that the apex portion is located on the front side and the arc portion is located on the rear side (see also FIG. 5).

  In the polishing pad 10 of this embodiment, the urethane sheets 2 constituting the foam layer 3 are juxtaposed so that the inclination direction SD of the foam 4 is directed toward the center direction of the polishing surface Sp (see FIG. 6A). . Normally, when the polishing pad 10 rotates during polishing, a centrifugal force acts on the slurry, so that the slurry easily flows out toward the outer periphery of the polishing pad 10. May cause a difference in flatness accuracy. In the polishing pad 10 of this embodiment, when centrifugal force is applied during polishing, the slurry easily flows into the foam 4 from the opening 5, and the slurry in the foam 4 is applied to the bottom of the foam 4 by applying polishing pressure. It becomes easy to flow out from the opening 5 at a position deviated from the position. Since the slurry in the foam 4 flows out to the center side of the polishing surface Sp, the slurry can be easily retained between the object to be polished and the polishing pad 10. Thereby, since the circulation property of the slurry is improved, it is possible to reduce the difference in the polishing amount between the outer peripheral portion and the center portion of the object to be polished, and the amount of slurry flowing out of the polishing pad 10 is reduced. Therefore, the use efficiency of the slurry can be improved.

<Third Embodiment>
Next, a third embodiment to which the present invention is applied will be described. In this embodiment, the urethane sheets 2 are juxtaposed so that the inclination direction SD of the foam 4 in each urethane sheet 2 is directed to the outer peripheral (outer edge) direction of the polishing surface Sp, and the polishing layer 3 is configured. Is as follows.

  As shown in FIGS. 7A and 7B, in the polishing pad 10 of the present embodiment, the polishing layer 3 has an inclination direction SD of the foam 4 in the four urethane sheets 2 toward the outer peripheral direction of the polishing surface Sp. It is configured as follows. At the time of manufacturing such a polishing pad 10, in the cutting process, four quarter-circle urethane sheets 2 are cut from the film-forming resin sheet 20, but the film-forming resin sheet 20 in the traveling direction CD in the sheet-forming process is cut. Cut so that the arc portion is located on the front side and the apex portion is located on the rear side (see also FIG. 5).

  In the polishing pad 10 of this embodiment, the urethane sheets 2 constituting the foam layer 3 are juxtaposed so that the inclination direction SD of the foam 4 is directed toward the outer peripheral direction of the polishing surface Sp (see FIG. 7A). . As described above, when the polishing pad 10 rotates during the polishing process, centrifugal force acts on the slurry, so that the slurry easily flows out toward the outer periphery of the polishing pad 10. In the polishing pad 10 of the present embodiment, since the inclined direction SD of the foam 4 is directed to the outer peripheral direction, the slurry can be more easily discharged by the centrifugal force acting during the polishing process. As a result, the circulation of the slurry is improved and the amount of outflow is increased, so that the aggregation and solidification of abrasive grains due to frictional heat and polishing load during the polishing process is reduced. Can be suppressed, and the occurrence of defects such as scratches on the object to be polished can be suppressed.

  In the polishing pad 10 of the above-described embodiment, an example in which the respective urethane sheets 2 are juxtaposed so as not to form a gap between the adjacent urethane sheets 2 and the polishing layer 3 is configured is shown, but the present invention is limited to this. Is not to be done. For example, as shown in FIG. 8, a gap 9 may be formed between the adjacent urethane sheets 2. In this way, since the gap 9 serves as a groove, the outflow of slurry is enhanced, and the polishing performance, particularly the polishing rate, can be improved. Whether or not the gap 9 is formed between the urethane sheets 2 can be selected according to the type of the object to be polished and the required polishing performance. For example, as a polishing pad used for finishing polishing, a gap 9 is formed between the urethane sheets 2 because the uneven shape on the polishing surface accompanying the formation of the groove may be transferred to the object to be polished and the flatness may be lowered. It is preferable that the polishing layer 3 is formed without the above.

  In addition, when the urethane sheet 2 is produced in the cutting process, an opening on the bottom side of the foam 4 is formed on the side surface of the urethane sheet 2 (surface intersecting the polishing surface Sp and the back surface Sr). There is. For this reason, when the gap 9 is formed between the adjacent urethane sheets 2, an opening is formed on the inner surface of the formed groove, making it difficult to obtain the above-described effects. Further, damage from the groove edge portion is likely to occur, and the life of the polishing pad may be reduced. In order to avoid these, for example, the cut side surface may be subjected to a thermocompression bonding process to close the opening. It is also possible to emboss after forming the polishing layer 3 without forming the gap 9 between the urethane sheets 2. In this way, it is possible to avoid the influence of the opening formed on the cut side surface, and to obtain the same effect as when the groove is formed.

  Furthermore, in the polishing pad 10 of the above embodiment, the example in which the polishing layer 3 is composed of four urethane sheets 2 has been shown. However, the present invention is not limited to this and is selected in the range of 4 to 10 sheets. can do. By constituting the polishing layer 3 with the urethane sheet 2 within this range, the slurry can be uniformly circulated and supplied to the polishing surface Sp. When the number of the urethane sheets 2 constituting the polishing layer 3 is too small, the slurry circulation supply becomes insufficient and the polishing performance may be lowered. In addition, it is difficult to effectively control the inclination direction SD of the foam 4, which is not preferable. On the other hand, when the number of urethane sheets 2 is too large, the adjacent portions of the urethane sheet 2 increase, which is insufficient in terms of the flatness of the polishing surface Sp.

  Furthermore, in the polishing pad 10 of the above-described embodiment, an example in which four urethane sheets 2 cut in a quadrant shape are juxtaposed to form a circular polishing layer 3 is shown, but the present invention is limited to this. It is not a thing. The shape of the polishing layer 3 may be a polygonal shape such as a rectangular shape in addition to the circular shape. Moreover, in the urethane sheet 2, although the example which makes two sides which pinch | interpose a vertex into a linear form was shown, it can also be made into a curvilinear form. For example, as shown in FIG. 9, urethane sheets 2 sandwiched between two arc-shaped curves with the center of the polishing layer 3 as the apex and from the apex to the outer periphery may be juxtaposed. Although there is no restriction | limiting in particular as a shape of a curve, What is necessary is just a continuous smooth curve shape. Of course, the urethane sheets 2 formed in a curved shape may be juxtaposed so that a gap is formed. If it does in this way, the clearance gap formed between the adjacent urethane sheets 2 will form a curvilinear groove | channel. Thereby, since the length of a groove | channel becomes long compared with a linear groove | channel, the circulation property of the slurry in the grinding | polishing surface Sp can be improved. In other words, the two sides of the urethane sheet 2 may be cut into a curved shape so that a curved groove for the purpose of improving the circulation of the slurry is formed.

  Furthermore, in the above-described embodiment, an example in which the base material 7 is bonded in the cutting process and the double-sided tape 8 is further bonded in the bonding process has been described. However, the present invention is urethane without bonding the base material 7 in the cutting process. The sheet 2 may be cut and the double-sided tape 8 and the urethane sheet 2 may be bonded together in the bonding process. In this case, the base material of the double-sided tape 8 also serves as the base material of the polishing pad. Moreover, although the double-sided tape 8 which has the base material of PET film and in which the adhesive layer was formed on both surfaces of the base material was illustrated, this invention is not restrict | limited to the material of a base material or an adhesive. It is also possible to use a non-support type tape composed only of an adhesive that does not have a substrate. If it does in this way, it can bond together with a desired base material irrespective of the material of the base material which constitutes double-sided tape 8. Of course, a material other than the PET film may be used as the substrate 7. Moreover, without bonding the base material 7 in the cutting process, a film made of a urethane resin may be used as the base material 7 in the bonding process, and the film and the urethane sheet 2 may be bonded via the urethane resin. . In this case, a solution in which a urethane resin is dissolved in DMF or the like may be used and interposed between the film and the urethane sheet 2. By removing the DMF by volatilization, the film and the urethane sheet 2 are integrated with each other through the urethane resin, so that peeling during polishing or the like can be suppressed. Furthermore, in the said embodiment, although the example which comprises the circular polishing pad 10 was shown by bonding with the double-sided tape 8 at a bonding process, the film-forming resin sheet 20, the double-sided tape 8, and the base material 7 were shown at the cutting process. It is also possible to attach the cut urethane sheet 2 directly to the surface plate of the polishing machine after the double-sided tape 8 is bonded together in this order.

  Further, although not specifically mentioned in the above embodiment, it is preferable to use a substrate having a thickness of about 100 to 200 μm. In this way, it is possible to suppress the occurrence of burrs or the like of the base material 7 when cutting. Moreover, when using what the adhesive layer was formed in both surfaces of the base material as the double-sided tape 8, it is preferable to use that whose thickness of a base material is about 60-200 micrometers. If it does in this way, it can control that polishing pad 10 peels from the surface plate of a polisher at the time of polish processing.

  Furthermore, although the urethane sheet 2 which comprises the polishing pad 10 showed the example made from a polyurethane resin in the said embodiment, this invention is not limited to this. As the polishing pad 10, the polishing layer 3 only needs to be composed of a plurality of resin sheets. As the resin sheet, polyester or polyethylene may be used instead of polyurethane resin. Furthermore, in this embodiment, although the urethane sheet 2 produced by the wet film-forming method was illustrated, this invention is not restrict | limited to this. The urethane sheet constituting the polishing layer 3 may be produced by a dry method, for example, as long as the foam formed inside is inclined in a certain direction with respect to the thickness direction. This can be realized, for example, as follows. That is, when the foamed polyurethane resin is cured and molded, the cast raw material mixture is reacted and cured in the mold while applying pressure from two directions, the vertical direction of the mold and the two opposite sides. Thus, an elongated ellipsoidal foam is formed in the same direction. By slicing the obtained foam block in a direction inclined within a range of 10 to 80 degrees, a polyurethane sheet in which the foam formation direction is inclined in a certain direction with respect to the thickness direction can be produced. What is necessary is just to cut | judge the obtained polyurethane sheet | seat and juxtapose so that the formation direction of foam may differ for every sheet | seat. In consideration of slurry circulation and cushioning properties, a resin sheet having a continuous foam structure formed by a wet film forming method is preferable.

  Moreover, in the said embodiment, the thickness ratio of an upper layer and a lower layer can be changed by changing the conditions in a wet film-forming method, for example, the density | concentration and temperature of a resin solution, the conveyance speed in a coagulation liquid, etc. . That is, the thickness direction central portion of the urethane sheet 2 can be changed within a range of ± 10% from the thickness direction center with respect to the entire thickness of the urethane sheet 2. In consideration of ensuring the circulation property and cushioning property of the polishing liquid and reducing the stress unevenness with respect to the object to be polished, it is preferable that the boundary between the upper layer and the lower layer is located substantially at the center in the thickness direction of the urethane sheet 2. . Moreover, in the said embodiment, although the specific examples, such as a solvent of a resin solution, a film-forming base material, and a coagulating liquid, were shown, this invention is not limited to these, You may use the material used normally. Of course.

  Furthermore, in the said embodiment, although the example which buffs the surface side of the skin layer of the film-forming resin sheet 20 was shown, this invention is not restrict | limited to this. When the thickness variation of the film-forming resin sheet 20 produced by the wet film-forming method becomes large, the buff treatment may be performed on the back surface Sr side in addition to the front surface side. In this way, the flatness of the polishing surface Sp can be further improved.

  Next, examples of the polishing pad 10 manufactured according to the above embodiment will be described. In the following examples, Example 1 is manufactured according to the first embodiment, Example 2 is manufactured according to the second embodiment, and Example 3 is manufactured according to the third embodiment. In addition, a comparative example manufactured for comparison is also shown.

Example 1
In Example 1, as a resin solution, 69 parts by mass of viscosity-adjusting DMF, 7 parts by mass of water with respect to 100 parts by mass of a DMF solution in which a polyester polyurethane resin is dissolved in DMF so as to be 30% by mass, It was prepared by mixing 1 part by mass of a polyether polyol, 2 parts by mass of an anionic surfactant, and 3 parts by mass of carbon black. It was 6.4 Pa.s as a result of measuring the viscosity at 25 degrees C of the obtained resin solution using the B-type rotational viscometer (the Toki Sangyo Co., Ltd. make, brand name "TVB-10 type"). This resin solution was applied to a PET film as a film forming substrate using a knife coater to form a coating film having a thickness of 1.0 mm. The obtained coating film together with the film forming substrate was introduced into a room temperature coagulation bath made of water as a coagulating liquid, and the resin was coagulated and regenerated while being conveyed at a conveying speed of 1.9 m / min. Produced. Next, the film-forming resin sheet 20 was taken out of the coagulation bath and immersed in a room temperature cleaning solution (desolvent bath) made of water to remove DMF as a solvent from the film-forming resin sheet 20. The film-forming resin sheet 20 was wound up while being dried, and continuously buffed on the surface on the skin layer side. A PET film (thickness: 188 μm) as the base material 7 was bonded to the film-formed resin sheet 20 after the buffing treatment with an adhesive, and then four urethane sheets 2 as shown in FIG. 1 were cut. Then, the double-sided tape 8 and the polishing pad 10 were manufactured by being juxtaposed in a circular shape so that the inclination direction SD of the foam 4 was directed in the direction opposite to the rotation direction RD of the polishing pad.

(Example 2, Example 3)
In Example 2 and Example 3, the polishing pad 10 was manufactured in the same manner as in Example 1 except that the direction of the inclined direction SD of the foam 4 was changed. In Example 2, the urethane sheet 2 is juxtaposed so that the inclination direction SD is directed toward the center of the polishing surface Sp (see also FIG. 6), and in Example 3, the urethane sheet is directed so that the inclination direction SD is directed toward the outer peripheral direction of the polishing surface Sp. 2 were juxtaposed (see also FIG. 7).

(Comparative Example 1)
A film-forming resin sheet 20 produced in the same manner as in Example 1 was cut into a circular shape and bonded to the double-sided tape 8 to produce a polishing pad. That is, in the polishing pad of Comparative Example 1, the inclination direction SD of the foam 4 is aligned in one direction.

(Polishing performance evaluation)
Using the polishing pad of each Example and Comparative Example, the aluminum substrate was polished under the following polishing conditions, and the polishing performance was evaluated by measuring three points: polishing rate, dub-off, and waviness. The amount of polishing was determined by measuring the weight reduction of the aluminum substrate before and after polishing. The polishing rate represents the amount of polishing per minute in terms of thickness, and was calculated from the measured value of the polishing amount, the polishing area and specific gravity of the aluminum substrate. Dub-off refers to the main surface (recording area) at R1 when R1 is an arbitrary point located in the radial direction from the center of the object to be polished and R2 is a point located radially outward from R1 from the center. , R2 is a numerical value indicating the maximum deviation distance between the straight line connecting the main surface and the aluminum substrate surface in the meantime. The smaller the value of the dub-off, the better the shape of the end of the aluminum substrate. Evaluation is a dub-off value (dub-off 1) obtained by measuring a range of a distance R32.5 mm to R34.0 mm from the center (1.0 mm to 2.5 mm from the end toward the center), a distance R33.0 mm from the center A dub-off value (dub-off 2) in which a range of R 34.5 mm (0.5 mm to 2.0 mm from the end toward the center) was measured was performed. The waviness is one of the measurement items for evaluating the surface accuracy (flatness), and the waviness (Wa) of the surface image per unit area observed with an optical non-contact surface roughness meter is expressed in angstroms (Å ) Expressed in units. A surface roughness measuring machine (manufactured by Zygo, model number New View 5022) was used for the measurement of dub-off and waviness.
(Polishing conditions)
Polishing machine: 9F-5P polishing machine manufactured by Speed Fam Co., Ltd. Polishing speed (rotation speed): 30 rpm
Processing pressure: 100 g / cm ²
Slurry: Alumina slurry Slurry supply amount: 100cc / min
Workpiece: Hard disk aluminum substrate (outer diameter 70mmφ, inner diameter 25mm, thickness 1.6mm, plated)
Target polishing amount: 1.5 μm / single side (the polishing time was adjusted so that the polishing amount was the same)

  In the polishing pad of Comparative Example 1 using a urethane sheet cut into a circular shape, since the inclination direction SD is aligned in one direction, the polishing rate is 0.467 μm / min, and the dove off 1 and the dub off representing the end shape are shown. 2 was 50.0 nm and 66.2 nm, respectively, and the undulation was 24.28 mm. This is presumably because the slurry flow in the polishing pad surface is unidirectional, resulting in unevenness in the slurry distribution in the polishing pad surface, resulting in poor flatness.

  On the other hand, in the polishing pad 10 of Example 1, Example 2, and Example 3 bonded together so that the inclined direction SD is different for each cut urethane sheet 2, the slurry flow can be controlled in an arbitrary direction. The polishing rates were 0.529 μm / min, 0.509 μm / min, and 0.499 μm / min, respectively, and an improvement was seen compared to Comparative Example 1. Also, the dub-off 1 was 10.4 nm, 13.2 nm, 10.6 nm, and the dub-off 2 was 35.5 nm, 36.8 nm, and 26.8 nm, respectively. Further, the swells were 9.90 mm, 10.38 mm, and 10.90 mm, respectively, and all were improved as compared with Comparative Example 1. This is presumably because the slurry distribution in the polishing pad surface became uniform.

  Since the present invention provides a polishing pad capable of improving the circulation property and polishing performance of the polishing liquid, and contributes to the manufacture and sale of the polishing pad, it has industrial applicability.

2 Urethane sheet (resin sheet)
3 Polishing layer 4 Foaming (vertical foaming)
5 Opening 10 Polishing pad Sp Polishing surface

Claims (10)

  In a polishing pad having a polishing layer having a polishing surface for polishing an object to be polished, the polishing layer is formed with a number of foams having a size over the entire thickness direction, and the foam is formed on the polishing surface. Are formed, and the foam formation direction from the central portion in the thickness direction of the foam to the formation position of the aperture is composed of a plurality of resin sheets inclined in a constant direction with respect to the thickness direction. A polishing pad, wherein the plurality of resin sheets are juxtaposed such that the foaming direction is different for each resin sheet.   2. The polishing pad according to claim 1, wherein the polishing layer is configured such that the resin sheets are juxtaposed so that the foam formation direction is in a direction opposite to a rotation direction during polishing. 3.   2. The polishing pad according to claim 1, wherein the polishing layer is configured such that the resin sheets are juxtaposed so that the foaming direction is directed toward the center of the polishing surface.   2. The polishing pad according to claim 1, wherein the polishing layer is configured such that the resin sheets are juxtaposed so that the foaming direction is directed toward the outer edge of the polishing surface.   2. The polishing pad according to claim 1, wherein the foam has a smaller diameter from a central portion in the thickness direction of the resin sheet to a position where the opening is formed to a bottom portion on the back side of the polishing surface.   The polishing pad according to claim 5, wherein the foaming is formed such that a foaming formation direction from a central part in the thickness direction to a bottom part on the back side is along the thickness direction.   In the foaming, the vertical line passing through the center of the hole formed in the cross section parallel to the polishing surface in the vicinity of the polishing surface is the same as the cross section parallel to the back surface in the vicinity of the back surface and intersects with the cross section parallel to the back surface. The polishing pad according to claim 6, wherein the polishing pad is located outside a hole formed by foaming.   The polishing pad according to claim 1, wherein the polishing layer is composed of 4 to 10 resin sheets.   The polishing pad according to claim 1, wherein a gap is formed between the resin sheets in the polishing layer.   The polishing pad according to claim 1, wherein the resin sheet is made of urethane resin.

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