JP2024088310A - Double-sided polishing machine - Google Patents

Abstract

To provide a double-sided polishing device that creates no scar on the periphery of an opening hole in polishing cloth and creates no linear trace on a surface of a base plate.SOLUTION: A double-sided polishing device 10 is characterized in that a plurality of through holes 21a, 21b are provided only in an outer area A31 of an under surface area of an upper surface plate except annular areas A21, A22, where A21, A22 are annular areas on a lower surface of the upper surface plate and are formed of annular, strip-shaped areas with respect to circular curves C21, C22 drawn with its radius being the length from the center of the upper surface plate to an intersection point, the intersection point being a point at which a circular curve with its radius defined from the center of a carrier 33 to a portion where neighboring holding holes 33h are closest to each other intersects with a straight line passing through the center of the upper surface plate and the center of the carrier, with the carrier 33 being positioned on a revolution track of the upper surface plate 21.SELECTED DRAWING: Figure 5

Description

The present invention relates to a double-sided polishing machine that simultaneously polishes the front and back surfaces of an object to be polished.

As one example of this type of polishing device, a single-wafer type polishing device has been disclosed that includes a carrier on which a wafer is mounted and which rotates in a fixed direction, a polishing platen on which an abrasive cloth for polishing the wafer is mounted, and a motor for rotating the polishing platen, and that polishes wafers one by one (see Patent Document 1). In this polishing device, the polishing cloth has an area from the center to the outer periphery that has no abrasive supply holes, when the polishing cloth has a radius of 5 inches.

A double-sided polishing machine has also been disclosed that includes upper and lower surface plates, upper and lower polishing cloths, and a carrier arranged between the upper and lower surface plates, with multiple objects to be polished being held by the carrier (see Patent Document 2). The double-sided polishing machine described in Patent Document 2 has a first through-holding hole in which the carrier holds the objects to be polished, and a second through-holding hole arranged in a ring shape around the first through-holding hole, and by shifting the center position of the first through-holding hole from the center position of the carrier, the occurrence of areas of non-uniform hardness in the polishing cloth of the surface plate is suppressed.

Japanese Patent Application Laid-Open No. 11-239961 WO2013/146135

The carrier of the double-sided polishing machine described in Patent Document 2 is provided with multiple through-holes that each hold multiple objects to be polished. The carrier is made of a thin plate member with a thickness similar to that of the wafer, and the areas between adjacent through-holes have a smaller area than other areas and tend to have lower rigidity.

The polishing device described in Patent Document 1 does not polish multiple wafers simultaneously, and therefore weak parts of the carrier are unlikely to be formed. However, the carrier of the double-sided polishing device described in Patent Document 2 is provided with multiple through-holding holes that each hold multiple objects to be polished. Therefore, the parts between adjacent through-holding holes become weak parts, and there is a risk of elastic deformation during polishing of the objects to be polished.

For example, if a through hole is provided in the platen for supplying abrasives, etc., and an opening hole is provided at the corresponding position in the polishing cloth attached to the surface of the platen, the elastically deformed weak part may interfere with the through hole in the platen, causing scratches around the opening hole in the polishing cloth. The scratches on the polishing cloth that occur around the opening hole are transferred to the surface of the object to be polished during the polishing operation, causing linear marks on the object to be polished. Such linear marks can affect the quality of the object to be polished, so it is necessary to prevent the marks from occurring.

The present invention has been made to solve the above problems, and aims to provide a double-sided polishing machine that does not cause scratches around the opening holes in the polishing cloth and does not cause linear marks on the surface of the object being polished.

(1) The double-sided polishing apparatus according to the present invention comprises a disk-shaped carrier having a plurality of holding holes for holding a plurality of objects to be polished, a platen having an upper platen and a lower platen which sandwich the carrier from above and below and rotate relative to each other, and an upper polishing cloth attached to the lower surface of the upper platen and a lower polishing cloth attached to the upper surface of the lower platen, and is a double-sided polishing apparatus which polishes the front and back surfaces of the objects to be polished by rotating and revolving the carrier between the upper polishing cloth attached to the upper platen and the lower polishing cloth attached to the lower platen, and the carrier rotates and revolves around the upper platen. When placed on a track, the intersection point is a circular curve with a radius from the center of the carrier to the point where adjacent holding holes are closest to each other, and a straight line passing through the center of the upper platen and the center of the carrier, and the annular belt-shaped area based on the circular curve drawn with a radius of the length from the center of the upper platen to the intersection point is defined as the annular area of the lower surface of the upper platen, the area of the lower surface of the upper platen other than the annular area is defined as the outer area of the lower surface of the upper platen, and multiple through holes are opened only in the outer area of the lower surface of the upper platen.

(2) The double-sided polishing apparatus according to the present invention is the double-sided polishing apparatus described in (1), characterized in that the intersection has a first intersection that intersects with the straight line radially inward of the upper platen relative to the center of the carrier, and the annular region has a first annular region based on a circular curve drawn with the length from the center of the upper platen to the first intersection as its radius.

(3) The double-sided polishing apparatus according to the present invention is the double-sided polishing apparatus described in (1), characterized in that the intersection has a second intersection that intersects with the straight line radially outside the center of the carrier, and the annular region has a second annular region based on a circular curve drawn with the length from the center of the upper platen to the second intersection as its radius.

(4) The double-sided polishing machine according to the present invention is the double-sided polishing machine described in (1), characterized in that the width of the annular region is the same as the radial width of the carrier at the weak portion where adjacent retaining holes of the carrier approach each other.

(5) The double-sided polishing machine according to the present invention is the double-sided polishing machine described in (1), characterized in that the upper polishing cloth is provided with opening holes that open at positions opposite the multiple through holes.

(6) The double-sided polishing machine according to the present invention is the double-sided polishing machine described in (1), characterized in that the width of the annular region is set to 10 mm to 25 mm radially inward and radially outward from the intersection of the upper platen.

According to the double-sided polishing apparatus of the present invention described in (1) above, a plurality of through holes are opened only in the outer region of the underside of the upper platen, and no through holes are opened within the annular region of the underside of the upper platen. This annular region of the underside of the upper platen is a region in which the movement direction of the carrier fragile part is along or opposite to the rotation direction of the upper platen when the carrier revolves while rotating on its axis, and in this annular region, the carrier fragile part of the carrier is not positioned in a position opposite the through hole of the upper platen via the upper polishing cloth. Therefore, when polishing the object to be polished, the carrier fragile part is prevented from interfering with the through hole of the upper platen in this annular region, and the upper polishing cloth around the through hole of the underside of the upper platen is prevented from being scratched.

According to the double-sided polishing apparatus of the present invention described in (2) above, there are two regions in which the carrier center line of the carrier fragile part is perpendicular to the rotation direction of the upper platen, one on the radially inner side and one on the radially inner side of the upper platen, and no through-holes are opened in the first annular region on the radially inner side. For example, when the rotation direction of the carrier and the rotation direction of the upper platen are the same, such as clockwise, in the first annular region on the radially inner side, the carrier fragile part moves in a direction opposite to the rotation direction of the upper platen, but since no through-holes are opened in the first annular region, the carrier fragile part of the carrier is not positioned in a position opposite the through-hole of the upper platen through the upper polishing cloth in the first annular region. Therefore, when polishing the object to be polished, the carrier fragile part is prevented from interfering with the through-hole of the upper platen in the first annular region, and scratches can be prevented from occurring in the upper polishing cloth around the through-hole on the lower surface of the upper platen.

According to the double-sided polishing apparatus of the present invention described in (3) above, there are two regions in which the carrier center line of the carrier fragile part is perpendicular to the rotation direction of the upper platen, one on the radial inside and one on the outer side of the upper platen, and of these, no through-holes are opened in the second annular region on the radial outside. For example, when the rotation direction of the carrier and the rotation direction of the upper platen are the same, such as clockwise, in the second annular region on the radial inside, the carrier fragile part moves in the direction along the rotation direction of the upper platen, but since no through-holes are opened in the second annular region, the carrier fragile part of the carrier is not positioned in a position facing the through-hole of the upper platen through the upper polishing cloth in the second annular region. Therefore, when polishing the object to be polished, the carrier fragile part is prevented from interfering with the through-hole of the upper platen in the second annular region, and scratches can be prevented from occurring in the upper polishing cloth around the through-hole on the lower surface of the upper platen.

According to the double-sided polishing apparatus of the present invention described in (4) above, the width of the annular region is the same as the carrier radial width of the carrier fragile portion, so that in this annular region, the carrier fragile portion of the carrier is not positioned opposite the through-hole of the upper platen via the upper polishing cloth. Therefore, when polishing the workpiece, the carrier fragile portion in this annular region is prevented from interfering with the through-hole of the upper platen, and scratches can be prevented from occurring in the upper polishing cloth around the through-hole on the underside of the upper platen.

According to the double-sided polishing apparatus of the present invention described in (5) above, the upper polishing cloth has openings at positions facing the multiple through holes. Through these openings, for example, abrasives and fluids can be directly supplied from the through holes in the upper platen to the object to be polished. As with the through holes, the carrier fragile parts of the carrier are not positioned in positions facing the openings, so that the carrier fragile parts are prevented from interfering with the openings in the upper polishing cloth, and scratches can be prevented from occurring on the upper polishing cloth around the through holes on the underside of the upper platen.

According to the double-sided polishing apparatus of the present invention described in (6) above, the width of the annular region of the upper platen is set to 10 mm to 25 mm from the intersection on the radially inward and radially outward sides of the upper platen. If the width of the annular region is 10 mm to 25 mm from the intersection on the radially inward and radially outward sides of the upper platen, it is possible to prevent the weak part of the carrier in the annular region from interfering with the through-hole of the upper platen when polishing the workpiece, and to prevent scratches from occurring around the through-hole on the underside of the upper platen.

The present invention provides a double-sided polishing machine that does not cause scratches around the openings of the through holes that open into the surface of the platen, and does not cause linear marks on the surface of the workpiece.

1A and 1B are diagrams of a hard disk substrate manufactured by a double-sided polishing apparatus according to an embodiment of the present invention, in which FIG. 1A shows a perspective view of a hard disk substrate, and FIG. 1B shows a cross-sectional view of the hard disk substrate. FIG. 1 is a configuration diagram of a double-sided polishing machine according to an embodiment of the present invention. FIG. 4 is a plan view of a carrier and a lower platen according to the embodiment of the present invention. 4A and 4B are diagrams illustrating the rotation direction of the double-sided polishing apparatus according to an embodiment of the present invention, where FIG. 4A shows the rotation direction of the upper platen, and FIG. 4B shows the rotation direction of the lower platen, sun gear, and carrier. FIG. 4 is a partially enlarged plan view of a carrier and a lower platen according to the embodiment of the present invention. FIG. 4 is a partially enlarged plan view showing a portion of a first intersection according to the embodiment of the present invention. FIG. 4 is a partially enlarged plan view showing a portion of a second intersection according to the embodiment of the present invention. FIG. 4 is a diagram showing the positions of through holes in the embodiment. FIG. 13 is a diagram showing the positions of through holes in a comparative example. 10A and 10B are diagrams showing a comparative example of a double-sided polishing apparatus, in which FIG. 10(a) shows an explanatory diagram of an enlarged view of the carrier and upper platen, FIG. 10(b) shows the rotation direction of the upper platen and the position through which the carrier weak part passes, FIG. 10(c) shows a plan view of the upper polishing cloth, and FIG. 10(d) shows a plan view of the object to be polished. 6A to 6C are diagrams showing an example of a method for defining the radial width of a carrier weak portion.

The following describes a double-sided polishing machine 10 according to an embodiment of the present invention, which uses the double-sided polishing machine, and a base plate 11 of the double-sided polishing machine 10 according to an embodiment of the present invention, which uses the base plate of the double-sided polishing machine.

First, we will explain the hard disk substrate 30 manufactured by the double-sided polishing apparatus 10 according to the embodiment. As shown in Figures 1(a) and 1(b), the hard disk substrate 30 is composed of a disk with an outer diameter D, an inner diameter d of the central through hole h, and a thickness th.

The hard disk substrate 30 has an outer diameter D of about 30 mm to 270 mm, an inner diameter d of about 10 mm to 70 mm, and a thickness th of about 0.3 mm to 2 mm. Specifically, the outer diameter D is 3.5 inches, 2.8 inches, and 2.5 inches, the inner diameter d is 20 mm and 25 mm, and the thickness th is 1.75 mm, 1.6 mm, 1.27 mm, 1.0 mm, 0.8 mm, 0.635 mm, and 0.6 mm to 0.3 mm, etc.

The substrate 30 for the hard disk is made of a plate material of aluminum or an aluminum alloy. The substrate 30 for the hard disk has a high degree of smoothness and a predetermined surface hardness, and has high rigidity and impact resistance that can suppress the generation of vibrations caused by high-speed rotation. The substrate 30 for the hard disk may also be a glass substrate made of a plate material of glass.

Next, the double-sided polishing apparatus 10 according to this embodiment will be described with reference to the drawings.
As shown in FIG. 2, the double-sided polishing apparatus 10 includes a platen 11, an air pressure unit 12, a fluid supply unit 13, an abrasive supply unit 14, a torque sensor (not shown), a rotational speed sensor, an abrasive recovery container for recovering used abrasive supplied from the abrasive supply unit 14, and a control device 100 for controlling the operation of these components.

As shown in FIG. 2, the surface plate 11 is composed of an upper surface plate unit 11A and a lower surface plate unit 11B. The double-sided polishing machine 10 has a mechanism for simultaneously polishing the front and back surfaces (hereinafter referred to as both sides) of the workpiece W held in the holding hole 33h (see FIG. 3) of the carrier 33 by sandwiching the carrier 33 between the upper surface plate unit 11A and the lower surface plate unit 11B and rotating and revolving the carrier 33 between the upper surface plate unit 11A and the lower surface plate unit 11B.

The upper surface plate unit 11A has an upper surface plate 21, an upper polishing cloth 22, an upper surface plate drive motor 23, a rotating shaft 24, an air pressure rod 25, and a universal joint 26, and is configured so that the driving force of the upper surface plate drive motor 23 is transmitted to the upper surface plate 21 via the rotating shaft 24 and the universal joint 26, causing the upper surface plate 21 to rotate. The upper surface plate unit 11A according to the embodiment corresponds to the surface plate of the double-sided polishing apparatus according to the present invention. In this embodiment, the case where the universal joint 26 is used has been described as an example, but the present invention is not limited to such a configuration, and can also be configured with other connecting members such as a spherical bearing.

The upper surface plate 21 has a disk shape with a predetermined thickness. The upper surface plate 21 is provided with a plurality of through holes 21a, 21b. The plurality of through holes 21a, 21b penetrate the upper surface plate 21 and open to the lower surface of the upper surface plate 21. The plurality of through holes 21a, 21b each open to an outer area A31 (see FIG. 5), which is a preset area on the lower surface of the upper surface plate 21. The outer area A31 on the lower surface of the upper surface plate 21 will be described later.

The multiple through holes 21a, 21b are of two types: through hole 21a through which the abrasive from the abrasive supply unit 14 is supplied, and through hole 21b through which a fluid is supplied to remove the carrier 33 and the polished object W that are stuck to the lower surface of the upper polishing cloth 22 after polishing. The through holes 21a, 21b are connected in communication with the piping 13a of the fluid supply unit 13, which will be described later, and the piping 14a of the abrasive supply unit 14.

A rotation speed sensor (not shown) is connected to the upper surface plate 21, and the rotation speed of the upper surface plate 21 is converted into an electrical signal and transmitted to the control device 100.

The upper polishing cloth 22 is attached to the lower surface, which is the plate surface, of the upper surface plate 21. The upper polishing cloth 22 is composed of an annular member that polishes the surface of the hard disk substrate 30. The upper polishing cloth 22 is provided with opening holes 22a, 22b that open at positions facing each of the through holes 21a, 21b of the upper surface plate 21. By attaching the upper polishing cloth 22 to the lower surface of the upper surface plate 21, the opening hole 22a faces and communicates with the through hole 21a, and the opening hole 22b faces and communicates with the through hole 21b.

The abrasive supplied from the through hole 21a is supplied from the opening hole 22a to the object to be polished W, and the abrasive promotes the polishing of the object to be polished W by the upper polishing cloth 22. Then, from the opening hole 22b, the fluid ejected from the through hole 21b at the timing when the gap between the upper surface plate 21 and the lower surface plate 32 is opened after polishing is sprayed directly toward the carrier 33 and the object to be polished W, and the carrier 33 and the object to be polished W that are stuck to the lower surface of the upper polishing cloth 22 are peeled downward from the upper polishing cloth 22.

The through holes 21a and 21b in this embodiment correspond to the through holes in the double-sided polishing apparatus according to the present invention. In addition, in this embodiment, an example has been described in which the upper polishing cloth 22 has an opening hole 22a, but the upper polishing cloth 22 may not have an opening hole 22a, and the polishing agent may be supplied or the fluid may be sprayed by passing through the upper polishing cloth 22.

The upper platen drive motor 23 is attached to a stationary member (not shown) and is connected to the rotating shaft 24 via a pulley 23a, such as a timing pulley, and a belt 23b, such as a timing belt. The driving force of the upper platen drive motor 23 is transmitted to the rotating shaft 24 via the pulley 23a and the belt 23b, causing the rotating shaft 24 to rotate clockwise when viewed from above, and causing the upper platen 21 to also rotate clockwise.

The rotating shaft 24 has a through hole that passes through the center along the axial direction, and a pneumatic rod 25 is inserted into the through hole. A flange 24a is formed at the bottom of the rotating shaft 24, and multiple rods 24b are provided on the flange 24a and protrude downward from the bottom surface.

The pneumatic rod 25 has a shaft portion that is inserted into the through hole of the rotating shaft 24, a flange portion formed below the shaft portion, and a connecting portion that is connected to a universal joint 26. The connecting portion of the pneumatic rod 25 is connected to the upper surface plate 21 via the universal joint 26, so that the pressure of the pneumatic unit 12 is transmitted to the upper surface plate 21. The pneumatic rod 25 is configured so that the rotation of the rotating shaft 24 is transmitted to the upper surface plate 21.

The universal joint 26 is a flexible joint that allows the angle at which the two connected members intersect to be freely changed. The connecting portion of the upper surface plate 21 and the pneumatic rod 25 is connected to the universal joint 26, and the flange portion of the pneumatic rod 25 is further connected to the rotating shaft 24. Therefore, even if the angle at which the horizontal surface of the upper surface plate 21 intersects with the axis of the rotating shaft 24 changes, the universal joint 26 allows the surface of the upper surface plate 21 to follow the top surface of the lower surface plate 32.

The lower surface plate unit 11B is composed of a table 31 serving as a base, a lower surface plate 32 rotatably attached to the table 31, a lower polishing cloth 37, a sun gear 34, a lower surface plate drive motor 35 that rotates the lower surface plate 32, and a sun gear drive motor 36 that rotates the sun gear 34.

The table 31 is a stationary member installed at a predetermined location, and rotatably supports the lower surface plate 32. The table 31 has internal teeth 31t formed on its inner circumferential surface facing the outer circumferential surface of the lower polishing cloth 37 attached to the lower surface plate 32, and is configured so that the external teeth 33t of the carrier 33, which will be described later, mesh with the internal teeth 31t of the table 31. The table 31 also rotatably supports the shaft portion 32d of the lower surface plate 32, which will be described later.

The lower surface plate 32 has a lower surface plate flange 32a whose upper surface faces the lower surface of the upper surface plate 21, and a shaft portion 32d that protrudes downward from the center of the lower surface plate flange 32a, and is rotatably supported by the table 31. A through hole is formed in the shaft portion 32d that passes through the center along the axial direction. The shaft portion 34b of the sun gear 34, which will be described later, is rotatably inserted into this through hole.

The lower polishing cloth 37 is attached to the upper surface of the lower surface plate flange 32a. Like the upper polishing cloth 22, the lower polishing cloth 37 is composed of an annular member that polishes the surface of the hard disk substrate 30.

As shown in Figures 2 and 3, the carrier 33 is made of a thin disk member on which external teeth 33t are formed, and the external teeth 33t have a diameter that allows the external teeth 33t to mesh with both the external teeth 34t of the sun gear 34 described below and the internal teeth 31t of the table 31. The carrier 33 rotates on its own axis and revolves around the sun gear 34 while meshing with the external teeth 34t of the sun gear 34 and the internal teeth 31t of the table 31.

The carrier 33 has a thin, disc-shaped main body 33a, and multiple holding holes 33h are formed to hold the objects W to be polished rotatably. In this embodiment, as an example, five holding holes 33h are formed at equal intervals in the circumferential direction around the center point of the main body 33a. In addition, there are ten carriers 33 that revolve around the sun gear 34. Therefore, 50 objects W to be polished are polished in one polishing process, and this number of objects W to be polished may be treated as one batch. In addition, a rotation speed sensor (not shown) is connected to the carrier 33, and the rotation speed of the carrier 33 is converted into an electrical signal and transmitted to the control device 100. Note that the number of objects mounted in one batch is not limited to this embodiment.

The thickness of the main body 33a of the carrier 33 is 1.0 mm or less, and by making the thickness thin, it is possible to polish a relatively thin object to be polished W. If the distance between the holding holes 33h exceeds 6.5 mm, the number of holding holes 33h formed in the carrier 33 will decrease, and there is a risk that the number of objects to be polished W that can be polished at one time will decrease.

The sun gear 34 has a gear portion 34a having external teeth 34t that mesh with the external teeth 33t of each carrier 33 when multiple carriers 33 are arranged around the sun gear 34, and a shaft portion 34b that supports the sun gear 34 rotatably relative to the table 31. The shaft portion 34b is rotated by the sun gear drive motor 36, and the sun gear 34 rotates counterclockwise when viewed from above.

The lower platen drive motor 35 is connected to the shaft 32d of the lower platen 32 via a pulley 35a, such as a timing pulley, and a belt 35b, such as a timing belt. The driving force of the lower platen drive motor 35 is transmitted to the shaft 32d, causing the shaft 32d to rotate counterclockwise when viewed from above, thereby rotating the lower platen 32 counterclockwise.

The sun gear drive motor 36 is connected to the shaft portion 34b of the sun gear 34 via a pulley 36a, such as a timing pulley, and a belt 36b, such as a timing belt. The driving force of the sun gear drive motor 36 is transmitted to the shaft portion 34b, causing the shaft portion 34b to rotate counterclockwise when viewed from above, causing the sun gear 34 to rotate counterclockwise.

In the double-sided polishing machine 10, as shown in FIG. 4(a), when the double-sided polishing machine 10 is viewed from above, the upper platen 21 rotates clockwise. Also, as shown in FIG. 4(b), the lower platen 32 rotates counterclockwise, the carrier 33 rotates clockwise while revolving counterclockwise, and the sun gear 34 rotates counterclockwise. Note that the rotation direction of the sun gear 34 may be reversed, clockwise. In this case, the rotation direction of the carrier 33 is reversed, i.e., it rotates counterclockwise and revolves clockwise.

As shown in FIG. 2, the pneumatic unit 12 is made up of a double-acting rod cylinder that reciprocates up and down, and is composed of a piston, cylinder body, and piston rod (not shown). The piston rod is connected to the pneumatic rod 25 of the upper surface plate unit 11A, and raises and lowers the upper surface plate 21 via the pneumatic rod 25 and universal joint 26. The pneumatic unit 12 can press the upper surface plate 21 toward the lower surface plate 32 with a predetermined pressing force by the pneumatic rod 25.

The fluid supply unit 13 has piping 13a, a pump (not shown), a pressure gauge, and an on-off valve, and is configured to supply fluid from the through hole 21b of the upper surface plate 21 through the opening hole 22b of the upper polishing cloth 22 to the carrier 33 and the object to be polished W, thereby peeling the carrier 33 and the object to be polished W from the upper surface plate unit 11A. Examples of the fluid include air and water. The pump is connected to the control device 100, and its operation is controlled. The pressure gauge is connected to the control device 100, and a signal of the pump pressure (MPa) is sent to the control device 100.

The abrasive supply unit 14 has piping 14a, a pump (not shown), a pressure gauge, and an on-off valve, and supplies the abrasive for polishing the workpiece W from the through hole 21a of the upper platen 21 through the opening hole 22a of the upper polishing cloth 22 to between the upper platen 21 and the lower platen 32. The pump is connected to the control device 100, and its operation is controlled. The pressure gauge is connected to the control device 100, and a signal of the pump pressure (MPa) is sent to the control device 100.

The polishing agent is not limited to this and can be variously changed, but for example, it is a liquid polishing agent containing abrasive grains made of aluminum _oxide ( _Al2O3 ) and silicon ( _SiO2 ) and a chemical component made of an etching component. The polishing agent is configured to increase the mechanical polishing effect due to the relative movement between the polishing agent and the polished body W by the surface chemical action of the abrasive grains themselves or the action of the chemical component, thereby obtaining a smooth polished surface.

The abrasive recovery container is a container for recovering used abrasive supplied from the abrasive supply unit 14.

The control device 100 has a central processing unit 101 that performs calculations and a memory 102 that stores a control program. The control device 100 is connected to the air pressure unit 12, the fluid supply unit 13, the abrasive supply unit 14, the upper platen drive motor 23, the lower platen drive motor 35, and the sun gear drive motor 36, and controls the operation of each component.

Next, the relationship between the positions of the multiple through holes 21a, 21b formed in the upper base plate 21 in the embodiment and the positions of the multiple holding holes 33h formed in the carrier 33 will be described with reference to Figures 5 and 6.

Figure 5 is a plan view of an upper surface plate according to an embodiment of the present invention, and is a partial plan view showing the lower surface of the upper surface plate and the carrier placed below it, with the upper surface plate seen through. Figures 6 and 7 are diagrams showing a state in which the movement direction of the carrier fragile part is along the direction of rotation of the upper surface plate or in a direction opposite to the direction of rotation of the upper surface plate, and are partial enlarged plan views showing the first intersection and second intersection according to an embodiment of the present invention.

As shown in Figures 5 to 7, as the width between adjacent retaining holes 33h of the carrier 33 narrows, the area between the retaining holes 33h becomes smaller, and the rigidity of that portion becomes locally low. The portion of the carrier 33 where the rigidity is lower than a predetermined value becomes the carrier weak portion 33b (the hatched area in Figures 6 and 7). The carrier weak portion 33b becomes an area of carrier radial length w11 that extends radially inward and radially outward of the carrier 33, based on a curve of radius r11 from the center P11 of the carrier 33 to the center point 33c of the portion where the two adjacent retaining holes 33h are closest to each other. The carrier weak portion 33b is located within the annular belt area A11, and moves with the rotation of the carrier 33.

The carrier 33 is placed between the lower surface plate 32 and the upper surface plate 21, and as shown in Figures 3 and 4(b), the external teeth 33t of the carrier 33 are meshed with the internal teeth 31t of the table 31 and the external teeth 34t of the sun gear 34, so that the carrier 33 is placed on an orbit that revolves around the sun gear 34 between the lower surface plate 32 and the upper surface plate 21.

As shown in FIG. 6, a circular curve C11, indicated by a dashed line with a radius r11 from the center P11 of the carrier 33 to the center point 33c of the portion where adjacent retaining holes 33h are closest to each other, intersects with a straight line L1 passing through the center P21 of the upper surface plate 21 and the center P11 of the carrier 33, radially inward of the center P11 of the carrier 33, forming a first intersection I11. The distance from the center P21 of the upper surface plate 21 to the first intersection I11 is then defined as a first radius r21, and the annular belt-like region based on the circular curve C21 drawn with the first radius r21 is defined as a first annular region A21 on the underside of the upper surface plate 21.

As shown in FIG. 7, the point where the curve C11 intersects with the straight line L1 passing through the center P21 of the upper surface plate 21 and the center P11 of the carrier 33, radially outside the center P11 of the carrier 33, is defined as a second intersection point I12. The length from the center P21 of the upper surface plate 21 to the second intersection point I12 is defined as a second radius r22, and the annular belt-like area based on the circular curve C22 drawn as the second radius r22 is defined as a second annular area A22 on the underside of the upper surface plate 21.

As shown in FIG. 5, if the area of the underside of the upper surface plate 21 other than the first annular area A21 and the second annular area A22 is defined as an outer area A31 of the underside of the upper surface plate 21, the multiple through holes 21a, 21b are provided so as to open only within the area of the outer area A31 of the underside of the upper surface plate 21. In other words, as shown in FIG. 5, the multiple through holes 21a, 21b are not provided in the first annular area A21 or the second annular area A22.

The widths w21, w22 of the first annular region A21 and the second annular region A22 are the same as the radial width w11 of the carrier 33 at the carrier fragile portion 33b. Specifically, they are formed 10 mm to 25 mm radially inward and outward from the first intersection I11 and the second intersection I12, respectively, of the upper surface plate 21.

FIG. 11 is a diagram showing an example of a method for defining the radial width of the carrier weak portion.
The radial width w11 of the carrier weak portion 33b can be determined by the ratio of the distance from the center point 33c of the carrier weak portion 33b to the arrangement position of each holding hole 33h. For example, a first imaginary circle D11 having a radius d1 from the center P11 of the carrier 33 to the point closest to the radial inside of the carrier 33 in the holding hole 33h, and a second imaginary circle D21 having a radius d2 from the center P11 of the carrier 33 to the point farthest from the radial outside of the carrier 33 in the holding hole 33h are determined. In the radial width w11 of the carrier weak portion 33b, the ratio of the width W31 from the center point 33c of the carrier weak portion 33b to the radially inner end to the distance W51 from the center point 33c of the carrier weak portion 33b to the first imaginary circle D11 along the radial direction of the carrier 33 is set to be in the range of 30% to 80%. Furthermore, the ratio of the width W31 from the center point 33c of the carrier weak portion 33b to the radial outer end thereof to the distance W41 from the center point 33c of the carrier weak portion 33b to the second virtual circle D21 along the radial direction of the carrier 33 is set to be in the range of 15% to 40% of the radial width w11 of the carrier weak portion 33b.

Next, a method for manufacturing the hard disk substrate 30 according to the embodiment will be briefly described. The hard disk substrate 30 according to the embodiment is manufactured by the double-sided polishing apparatus 10 according to the embodiment. The method for manufacturing the hard disk substrate 30 according to the embodiment includes an upper process and a lower process. The upper process includes a lathe process, a first annealing process (PLB), a grinder process, a second annealing process (PGB), a plating process, and a third annealing process (PPB), and the lower process is performed after the upper process and includes a polishing process, a surface inspection process, and a cleanliness inspection process. Each process of the upper process and the lower process is performed in order, and the hard disk substrate 30 is manufactured through each process. Each process other than the polishing process is composed of known processes, but is not limited to these, so it will be briefly described.

After the lower process, the hard disk substrate 30 that has undergone the lower process is shipped. The shipping process includes a shipping preparation process, a labeling process, a vacuum process, and a packaging process, and each step in the shipping process is carried out in order.

Each step will be described below in order. In the lathe process, a disk-shaped substrate with dimensions that will result in a hard disk substrate 30 with a specified outer diameter D (mm) and inner diameter d (mm) is formed by cutting using a lathe.

In the first annealing process (PLB), the substrate formed in the lathe process is annealed by holding it at a high temperature and then slowly cooling it. The annealing process removes the internal strain caused by the cutting process.

In the grinding process, the substrate annealed in the first annealing process (PLB) is subjected to two stages of processing, such as grinding and grinding with a rotating grindstone, to form a substrate of dimensions that will produce a hard disk substrate 30 with a specified thickness th with high precision.

Next, in the second annealing process (PGB), annealing is performed, and in the plating process, a predetermined thickness of electroless nickel-phosphorus plating (Ni-P) is applied to the substrate annealed in the second annealing process (PGB). Next, in the third annealing process (PPB), annealing is performed.

In the polishing process, the plated substrate, i.e., the object to be polished W, is mirror-polished in two stages by the platen 11 of the double-sided polishing machine 10. In the polishing process, first, one batch of 50 objects to be polished W is set on the carrier 33 shown in FIG. 3. Once the objects to be polished W have been set, the double-sided polishing machine 10 operates under the set polishing conditions, and mirror polishing of both sides of the object to be polished W begins.

When the double-sided polishing machine 10 is in operation, as shown in Figures 4(a) and 4(b), the upper platen 21 rotates clockwise, and the lower platen 32, carrier 33, and sun gear 34 rotate counterclockwise. Note that the sun gear 34 may also be configured to rotate clockwise. In this case, the rotation direction of the carrier 33 is clockwise.

When mirror polishing begins, abrasive is supplied from the abrasive supply unit 14 to the object to be polished W. Both sides of the object to be polished W are polished simultaneously between the upper polishing cloth 22 attached to the upper surface plate 21 and the lower polishing cloth 37 attached to the lower surface plate 32.

The first annular region A21 and the second annular region A22 are regions in which the moving direction V11 of the carrier fragile portion 33b is along the rotation direction V21 of the upper platen 21 (see FIG. 7) or opposite to it (see FIG. 6) when the carrier 33 revolves while rotating on its axis. In the first annular region A21 and the second annular region A22, the carrier center line connecting the center P11 of the carrier 33 and the center point 33c of the carrier fragile portion 33b intersects with the rotation direction V21 of the upper platen 21 at an angle perpendicular or nearly perpendicular. In the first annular region A21 and the second annular region A22, the tangents of the curves C21 and C22 and the tangent of the curve C11 coincide or fall within a predetermined angle range.

5, the through holes 21a and 21b of the upper surface plate 21 do not open into the first annular region A21 and the second annular region A22, but only open into the outer region A31, as described above. Therefore, the carrier fragile portion 33b of the carrier 33 does not face the through holes 21a and 21b of the upper surface plate 21 in the first annular region A21 and the second annular region A22. Therefore, even if the carrier fragile portion 33b elastically deforms when polishing the polished body W, the carrier fragile portion 33b does not interfere with the through holes 21a and 21b of the upper surface plate 21 in the first annular region A21 and the second annular region A22. Therefore, it is possible to prevent the carrier fragile portion 33b from interfering with the through holes 21a and 21b of the upper surface plate 21 and causing scratches around the opening holes 22a and 22b of the upper polishing cloth 22. In other words, it is possible to prevent scratches from occurring on the upper polishing cloth 22 around the through holes 21a and 21b of the upper surface plate 21.

In the surface inspection process, the surface condition of the object W that does not exceed the predetermined standard value in the flatness inspection process is inspected to see if it exceeds the predetermined standard value, and only those objects W whose surface condition does not exceed the predetermined standard value as a result of the inspection are sent to the next process.

In the cleanliness inspection process, only those objects W whose surface condition does not exceed a predetermined standard value in the surface inspection process are inspected for cleanliness. A sample is taken from a given lot of objects W to be polished, and the sample's cleanliness inspection results are compared with the lot judgment criteria to determine whether the lot passes or fails. Objects W that are judged to pass are moved on to the next shipping process.

The predetermined standard values for the flatness inspection and surface inspection, and the lot judgment standard for the cleanliness inspection are appropriately selected based on set specifications such as the size and thickness of the hard disk substrate, and data such as experimental values.

The double-sided polishing machine 10 according to the embodiment and the effects of the double-sided polishing machine 10 are described below.

The double-sided polishing machine 10 according to this embodiment includes a disk-shaped carrier 33 having a number of holding holes 33h for holding a number of objects W to be polished, and a platen 11 having an upper platen 21 and a lower platen 32 which sandwich the carrier 33 from above and below and rotate relative to each other. The carrier 33 is rotated and revolved between the upper platen 21 and the lower platen 32 to polish both sides of the objects W to be polished.

In the double-sided polishing apparatus 10 according to this embodiment, the multiple through holes 21a, 21b are open only to the outer region A31 of the lower surface of the upper platen 21, and are not open to the first annular region A21 and the second annular region A22. As shown in FIG. 6 and FIG. 7, the first annular region A21 and the second annular region A22 of the lower surface of the upper platen 21 are regions in which the movement direction of the carrier fragile portion 33b is along or opposite to the rotation direction of the upper platen 21 when the carrier revolves while rotating on its axis. The through holes 21a, 21b are not open to the first annular region A21 and the second annular region A22, and the carrier fragile portion 33b of the carrier 33 does not face the multiple through holes 21a, 21b of the upper platen 21 in the first annular region A21 and the second annular region A22.

Therefore, when polishing the object W to be polished, the carrier fragile portion 33b is prevented from interfering with the through holes 21a, 21b of the upper platen 21 in the first annular region A21 and the second annular region A22, and scratches can be prevented from occurring around the opening holes 22a, 22b of the upper polishing cloth 22, i.e., around the through holes 21a, 21b of the upper platen 21. As a result, the problem of scratches occurring around the opening holes formed in the polishing cloth in a conventional double-sided polishing device is resolved, and an object W to be polished that has been optimally mirror-polished can be obtained.

In the double-sided polishing machine 10 according to this embodiment, the carrier radial widths w21, w22 of the first annular region A21 and the second annular region A22 are 10 mm to 25 mm radially inward and outward from the first intersection I11 and the second intersection I12 of the upper platen 21, respectively, and are the same size as the carrier radial width at the carrier fragile portion 33b.

The widths w21, w22 of the first annular region A21 and the second annular region A22 are 10 mm to 25 mm, which is the same as the carrier radial width of the carrier weak portion 33b, so that the carrier weak portion 33b does not pass through the multiple through holes 21a, 21b. Therefore, it is possible to prevent the carrier weak portion 33b from deforming and interfering with the through holes 21a, 21b. As a result, the peripheral portion of the multiple opening holes 22a, 22b of the upper polishing cloth 22 is not damaged by the carrier weak portion 33b, and the polished object W is polished properly, and the problem of the conventional pattern is solved without the occurrence of a pattern like that which was transferred to the polished object W due to scratches that occurred in the conventional polishing cloth (see FIG. 10(d)).

In the double-sided polishing machine 10 according to this embodiment, a plurality of through holes 21a, 21b penetrate the upper surface plate 21, and opening holes 22a, 22b are provided at positions opposite the plurality of through holes 21a, 21b, penetrating the upper polishing cloth 22. As a result, abrasive can be supplied from the polishing agent supply unit 14 through the piping 14a to both sides of the object to be polished W. In addition, fluid can be supplied from the fluid supply unit 13 through the piping 13a to the upper polishing cloth 22, and the object to be polished W stuck to the upper polishing cloth 22 can be peeled off from the upper polishing cloth 22.

Figure 8 shows the position of the through holes in this embodiment, Figure 9 shows the position of the through holes in a comparative example, and Figure 10 shows a comparative example of a double-sided polishing machine. Figure 10(a) is an enlarged view of the carrier and upper platen, Figure 10(b) shows the rotation direction of the upper platen and the position where the carrier fragile part passes, Figure 10(c) shows a plan view of the polishing cloth, and Figure 10(d) shows a plan view of the object to be polished.

The positions of the multiple through holes provided on the lower surface of the upper platen 21 are different between the double-sided polishing machine of this embodiment shown in FIG. 8 and the comparative example shown in FIG. 9 and FIG. 10. In the comparative example, multiple through holes 21a, 21b are also provided in the first annular region A21 and the second annular region A22 as shown in FIG. 9 and FIG. 10(b). Therefore, as shown in FIG. 10(c), linear scratches Sc are generated around the opening holes 22a, 22b of the upper polishing cloth 22. The damage to the upper polishing cloth 22 generated in the through holes 21a, 21b may be transferred to the surface of the polished object W as shown in FIG. 10(d), and linear traces may be generated on the polished object W. Note that the linear traces shown in FIG. 10(d) cannot be visually confirmed on the polished object W, but can be confirmed with an optical surface analyzer (for example, the 6100 series of Candela (manufactured by KLA Tencor)). Such traces must not be allowed to occur, whether they are visible or not.

In contrast, in the double-sided polishing machine 10 according to this embodiment, as shown in FIG. 8, the multiple through holes 21a, 21b do not open to the first annular region A21 and the second annular region A22. Therefore, when polishing the workpiece W, the carrier fragile portion 33b is prevented from interfering with the through holes 21a, 21b of the upper platen 21 in the first annular region A21 and the second annular region A22, and scratches can be prevented from occurring around the opening holes 22a, 22b of the upper polishing cloth 22.

Although the embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and various design changes can be made without departing from the spirit of the present invention described in the claims. Furthermore, the components described in this embodiment are merely examples and can be modified as appropriate.

10: double-sided polishing machine, 11: surface plate, 11A: upper surface plate unit (surface plate), 11B: lower surface plate unit (surface plate), 21: upper surface plate (surface plate), 21a, 21b: through hole, 22: upper polishing cloth, 22a, 22b: opening hole, 30: hard disk substrate, 32: lower surface plate (surface plate), 33: carrier, 33h: holding hole, 34: sun gear, 37: lower polishing cloth, A21: first annular region, A22: second annular region, A31: outer region, I11: first intersection, I12: second intersection, W: object to be polished

Claims (7)

A double-sided polishing apparatus comprising: a disk-shaped carrier having a plurality of holding holes for holding a plurality of objects to be polished, a platen having an upper platen and a lower platen which sandwich the carrier from above and below and rotate relative to each other, and an upper polishing cloth attached to the lower surface of the upper platen and a lower polishing cloth attached to the upper surface of the lower platen, wherein the carrier is rotated and revolved between the upper polishing cloth attached to the upper platen and the lower polishing cloth attached to the lower platen to polish the front and back surfaces of the objects to be polished,
a circular curve having a radius of 100 nm from the center of the carrier to the point where adjacent retaining holes are closest to each other and a straight line passing through the center of the upper platen and the center of the carrier intersect at the intersection point, the ... upper platen to the intersection point is defined as a circular ring-shaped area on the underside of the upper platen, the area on the underside of the upper platen other than the circular ring-shaped area is defined as an outer area on the underside of the upper platen, and a plurality of through holes are opened only in the outer area of the underside of the upper platen. the intersection includes a first intersection that intersects with the straight line on a radially inner side of the upper platen relative to a center of the carrier,
2. The double-sided polishing apparatus according to claim 1, wherein the annular region has a first annular region based on a circular curve drawn with a radius equal to a length from the center of the upper platen to the first intersection point. the intersection has a second intersection that intersects with the straight line on a radially outer side of the upper platen relative to a center of the carrier,
2. The double-sided polishing apparatus according to claim 1, wherein the annular region has a second annular region based on a circular curve drawn with a radius equal to a length from the center of the upper platen to the second intersection point. The double-sided polishing machine according to claim 1, characterized in that the width of the annular region is the same as the radial width of the carrier at the weak portion where the adjacent retaining holes of the carrier approach each other. The double-sided polishing machine according to claim 1, characterized in that the upper polishing cloth has opening holes that open at positions opposite the multiple through holes. The double-sided polishing machine according to claim 1, characterized in that the width of the annular region is set to 10 mm to 25 mm radially inward and radially outward from the intersection of the upper platen. The upper polishing cloth provided in the double-sided polishing machine according to claim 1 is characterized in that an opening hole is provided at a position opposite to the multiple through holes opening in the upper surface plate.

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