Patent Application
20250073844
This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2023-142800, filed on Sep. 4, 2023, and the entire contents of which are incorporated herein by reference.
The present invention relates to a polishing head, a polishing apparatus, and a polishing method.
There has been known a polishing head, provided to be vertically movable and rotatable in a polishing apparatus, with which a workpiece is held, and is polished by being rotated and pressed against a polishing pad. Furthermore, there has been known a polishing apparatus that polishes a workpiece by pressing a workpiece held on a lower surface of the polishing head provided above a surface plate against the polishing pad attached to an upper surface of the surface plate, and rotating and relatively sliding the surface plate and the polishing head. The polishing apparatus is a single-side polishing apparatus that polishes a single surface of the workpiece.
As described in PTL 1 (Japanese Patent No. 5629594), there are two common polishing methods for polishing using the single-side polishing apparatus (see FIG. 5 in PTL 1). One is back surface reference polishing in which the back surface (an upper surface, which is a non-polished surface) of a workpiece is polished while being fixed to a relatively hard and flat surface. In this case, the front surface (a lower surface, which is a polished surface) of the workpiece is polished in accordance with the shape of the back surface, that is, the shape of the flat surface of the polishing head. The other one is front surface reference polishing in which the back surface of the workpiece is polished while being fixed to a relatively soft elastic surface. In this case, the front surface of the workpiece is polished in accordance with the shape of the front surface.
The workpiece is polished, with the front surface reference polishing and the back surface reference polishing selectively performed in accordance with the purpose.
However, the front surface reference polishing and the back surface reference polishing are performed with conventional polishing heads with different basic configurations. This has led to needs for replacing the polishing head or providing a plurality of polishing apparatuses in accordance with the polishing methods. Thus, there have been problems in that the replacement of the polishing head involves a downtime, and that the use of a plurality of polishing heads or polishing apparatuses leads to an increase in cost, size, and complexity of the facility.
The conventional polishing head (polishing apparatus) is configured in such a manner that when the back surface of the workpiece is fixed to a relatively soft elastic surface, a soft and porous member is formed to provide suction holes through which the air is sucked for fixing the workpiece by the suction. Thus, the fixing and picking up of the workpiece may involve a risk of formation of suction marks on the workpiece. Furthermore, the picking up involves a risk of causing trouble in the polishing head due to foreign matters such as water or slurry sucked into the polishing head together with the air through the suction holes.
The present invention has made in view of the above circumstances, and an object of the present invention is to provide a polishing head, a polishing apparatus, and a polishing method with which front surface reference polishing and back surface reference polishing can both be performed using a single polishing head, the downtime can be reduced, the facility cost can be reduced, the facility can be downsized and simplified, and formation of suction marks on a workpiece and mixture of foreign matters into the polishing head are prevented.
The present invention achieves the above-described object, by means of the following solutions described as an embodiment.
A polishing head according to the present invention is a polishing head that is fixed to a head shaft that is capable of vertically moving and rotating to be vertically movable and rotatable, and polishes a workpiece by holding the workpiece and rotating and pressing the workpiece against a polishing pad, the polishing head including: a backing material including a suction surface facing an upper surface of the workpiece and a pressing surface opposite to the suction surface; a workpiece pressurization plate that is provided at a center portion of the pressing surface to be contactable with and separable from the pressing surface, and is vertically movable; a first fluid chamber provided between the workpiece pressurization plate and the backing material; and a first pressure adjustment mechanism that adjusts a pressure in the first fluid chamber, wherein a control unit performs control to switch between front surface reference polishing in which control is performed to pressurize inside of the first fluid chamber to press the workpiece from above in a state where a lower surface of the workpiece pressurization plate and the pressing surface of the backing material are separated from each other and in a state where the upper surface of the workpiece and the suction surface of the backing material are in contact with each other, and back surface reference polishing in which control is performed to vacuumize or open the inside of the first fluid chamber to atmosphere and to apply downward force to the workpiece pressurization plate to press the workpiece from above in a state where the lower surface of the workpiece pressurization plate and the pressing surface of the backing material are in contact with each other and in a state where the upper surface of the workpiece and the suction surface of the backing material are in contact with each other.
With this configuration, the front surface reference polishing and the back surface reference polishing can both be performed using a single polishing head. A gap can be formed with the workpiece pressurization plate and the backing material separated from each other, whereby the workpiece can be fixed and picked up using the backing material as a suction panel. Thus, the backing material needs not to be provided with suction holes, whereby the formation of suction marks on the workpiece as well as mixture of foreign matters into the polishing head can be prevented.
The polishing head according to the present invention may further include a retainer provided to an outer circumference portion of the suction surface and a retainer pressurization unit that is provided to an outer circumference portion of the pressing surface and is vertically movable, wherein the control unit may apply forces in relatively opposite vertical directions to the retainer pressurization unit and the workpiece pressurization plate, to perform the front surface reference polishing in a state where a lower end surface of the workpiece pressurization plate is located relatively higher than a lower end surface of the retainer pressurization unit, and to perform the back surface reference polishing in a state where the lower end surface of the workpiece pressurization plate and the lower end surface of the retainer pressurization unit are flush in a horizontal direction, or in a state where the lower end surface of the workpiece pressurization plate is located relatively lower than the lower end surface of the retainer pressurization unit.
Preferably, the polishing head according to the present invention includes a pressing part that brings the workpiece pressurization plate and the retainer pressurization unit into contact with each other for relative fixing, and functions, when the workpiece is polished, as a stopper that restricts movement of the workpiece pressurization plate and the retainer pressurization unit in a predetermined direction to achieve relative positional relationship.
As an example of the positional relationship, a gap may be formed between the retainer and the polishing pad, when the workpiece is pressed against the polishing pad in a state where the workpiece pressurization plate and the retainer pressurization unit are in contact with each other with the pressing part provided in between at the time of the back surface reference polishing. With this configuration, contact between the retainer and the polishing pad is prevented at the time of the back surface reference polishing, so that the retainer can be prevented from wearing.
Preferably, the workpiece pressurization plate is formed by two layers including an upper plate and a lower plate, the polishing head further includes: a second fluid chamber that is provided between the upper plate and the lower plate; and a second pressure adjustment mechanism that adjusts a pressure in the second fluid chamber, and the lower plate includes a flow channel communicating the first fluid chamber and the second fluid chamber. With this configuration, when, at the time of the back surface reference polishing, the workpiece pressurization plate and the backing material are brought into contact with each other to be integrated, the inside of the second fluid chamber is vacuumized, whereby bubbles between the workpiece pressurization plate and the backing material are removed from the flow channel through the second fluid chamber, so that the workpiece pressurization plate and the backing material can be brought into closer contact with each other. As an example, the flow channel can be formed with the lower plate formed by a porous material.
Alternatively, the workpiece pressurization plate preferably includes a flow channel communicating the first fluid chamber and a first flow path provided with the first pressure adjustment mechanism. With this configuration, when, at the time of the back surface reference polishing, the workpiece pressurization plate and the backing material are brought into contact with each other to be integrated, the inside of the first fluid chamber is vacuumized, whereby bubbles between the workpiece pressurization plate and the backing material are removed from the flow channel through the first flow path, so that the workpiece pressurization plate and the backing material can be brought into closer contact with each other. As an example, the flow channel can be formed as a groove in the lower surface of the workpiece pressurization plate.
Alternatively, the workpiece pressurization plate preferably includes a flow channel communicating the first fluid chamber and a fifth flow path provided with a fifth pressure adjustment mechanism, and the fifth pressure adjustment mechanism is preferably configured to be capable vacuumizing at least the flow channel through the fifth flow path. With this configuration, when, at the time of the back surface reference polishing, the workpiece pressurization plate and the backing material are brought into contact with each other to be integrated, the flow channel is vacuumized by the fifth pressure adjustment mechanism through the fifth flow path, whereby bubbles between the workpiece pressurization plate and the backing material are removed from the flow channel through the fifth flow path, so that the workpiece pressurization plate and the backing material can be brought into closer contact with each other.
The polishing head according to the present invention may further include a head base portion fixed to the head shaft, the workpiece pressurization plate may be fixed to the head base portion and configured to be vertically moved by driving of the head shaft, and the control unit may be configured to, at the time of the back surface reference polishing, perform control to apply driving force for lowering the workpiece pressurization plate via the head shaft, to apply downward force to the workpiece pressurization plate. Alternatively, the polishing head according to the present invention may further include a head base portion fixed to the head shaft, the workpiece pressurization plate may be suspended from or in slidably close contact with the head base portion, and configured to vertically move with a pressure in a third fluid chamber provided between the head base portion and the workpiece pressurization plate adjusted by a third pressure adjustment mechanism, and the control unit may be configured to perform control, at the time of the back surface reference polishing, to pressurize inside of the third fluid chamber, to apply downward force to the workpiece pressurization plate.
A polishing apparatus according to the present invention includes the polishing head according to the present invention.
A polishing method according to the present invention is a polishing method of polishing a workpiece held and pressed against a polishing pad by a polishing head including: a backing material that has a suction surface facing an upper surface of the workpiece and a pressing surface opposite to the suction surface; and a workpiece pressurization plate that is provided at a center portion of the pressing surface to be contactable with and separable from the pressing surface and is vertically movable, the method including switching between front surface reference polishing in which the workpiece pressurization plate is raised to form a closed space between the workpiece pressurization plate and the backing material, and the closed space is pressurized to press the workpiece from above in a state where a lower surface of the workpiece pressurization plate and the pressing surface of the backing material are separated from each other and in a state where the upper surface of the workpiece and the suction surface of the backing material are in contact with each other, and back surface reference polishing in which the closed space is vacuumized or opened to atmosphere and downward force is applied to the workpiece pressurization plate, to press the workpiece from above in a state where the lower surface of the workpiece pressurization plate and the pressing surface of the backing material are in contact with each other and in a state where the upper surface of the workpiece and the suction surface of the backing material are in contact with each other.
Furthermore, by using the polishing head further including: a retainer provided to an outer circumference portion of the suction surface; and a retainer pressurization unit that is provided to an outer circumference portion of the pressing surface and is vertically movable, in the front surface reference polishing, the retainer pressurization unit may be lowered to press the polishing pad in a periphery of the workpiece by the retainer, and in the back surface reference polishing, a gap may be formed between a lower end surface of the retainer and the polishing pad.
According to the present invention, the front surface reference polishing and the back surface reference polishing can both be performed using a single polishing head. Thus, the downtime can be reduced, the facility cost can be reduced, and the facility can be downsized and simplified. Furthermore, since the gap can be formed by separating the workpiece pressurization plate from the backing material, the workpiece can be fixed and picked up using the backing material as a suction panel. Thus, the backing material needs not to be provided with suction holes. As a result, formation of suction marks on the workpiece can be prevented, and mixture of foreign matters into the polishing head can be prevented.
An embodiment of the present invention will be described in detail below with reference to the drawings.
As illustrated in
The polishing head 12 includes a head base portion 20 in its upper portion. The head base portion 20 includes a disk-shaped head base top plate 20a, a tubular head upper portion side wall portion 20b protruding downward from an outer end portion of the head base top plate 20a, and a shaft portion 20c protruding downward from a center portion of the lower surface of the head base top plate 20a. Thus, the head base portion 20 protects the upper portion of the polishing head 12 like a lid covering the same. The center portion of the upper surface of the head base portion 20 (upper surface of the head base top plate 20a) is fixed to a head shaft 18 that is vertically movable and rotatable. The head shaft 18 is vertically moved by a vertical movement driving mechanism (not illustrated) of a driving unit. Thus, the head base portion 20 vertically moves together with the head shaft 18. The head shaft 18 is rotated about an axis by a rotational driving mechanism (not illustrated) of the driving unit. Thus, the head base portion 20 rotates about the head shaft 18. In this manner, the polishing head 12 is provided to be vertically movable and rotatable by the driving of the head shaft 18. The vertical movement driving mechanism and the rotational driving mechanism of the driving unit can each be configured by a known mechanism. Specific examples will be described below.
The polishing head 12 includes a retainer pressurization unit 22 in a lower portion thereof (below the head base portion 20), as illustrated in
As illustrated in
As described above, the retainer pressurization unit 22 is suspended by the head base portion 20 via the suspension members 26a, 26b. The suspension members 26a, 26b according to the present embodiment are each formed by a diaphragm made of a rubber material. The retainer pressurization unit 22 is configured to vertically move with respect to the head base portion 20, through a change in shape of the suspension members 26a, 26b. A configuration is employed in which rotation occurs with rotational force, produced by rotation of the head base portion 20, transmitted through the suspension members 26a, 26b. The configuration and the material of the suspension members 26a, 26b are not limited, as long as the retainer pressurization unit 22 can be suspended to be vertically movable as described above. Thus, the diaphragm is not limiting, and bellows or the like may be employed, for example. The rubber material is not limiting, and a resin material, a metal material, or the like may be employed.
A fourth fluid chamber 28 is provided between the lower surface of the head base portion 20 (lower surface of the head base top plate 20a) and the upper surface of the retainer pressurization unit 22 (upper surface of the retainer pressurization top plate 22a) (and the suspension members 26a, 26b). A fluid can be supplied into and discharged from the inside of the fourth fluid chamber 28 through a fourth flow path 30 provided with a fourth pressure adjustment mechanism 32. With this configuration, the retainer pressurization unit 22 (retainer 24) can be lowered with a positive pressure achieved in the fourth fluid chamber 28 formed as a closed space, and the retainer pressurization unit 22 (retainer 24) can be raised with a negative pressure achieved in the fourth fluid chamber 28. In the present embodiment, a configuration is employed in which the fluid is air, and the pneumatic pressure in the fourth fluid chamber 28 is adjusted. However, this configuration is not limiting, and the fluid may be water, oil, or the like, for example. In the fourth flow path 30 including a supply path and a discharge path, the supply path and the discharge path may be provided as a single pipe line, or as separate pipe lines. That is, the number and other modes of the pipe line(s) forming the fourth flow path 30 are not limited. The fourth pressure adjustment mechanism 32, examples of which include a fluid compressing apparatus, a solenoid valve, and the like, is drivingly controlled by a control unit 72. The control unit 72 provided at a predetermined location in the polishing apparatus 10 includes a CPU and a memory, and performs a predetermined operation based on an operation program set in advance and/or a setting signal input from an operation unit (not illustrated). A plurality of the fourth pressure adjustment mechanisms 32 may be provided.
With the pressure in the fourth fluid chamber 28 adjusted as described above, the retainer pressurization unit 22 vertically moves, whereby a vertical position of the retainer 24 can be adjusted. Thus, at the time of the polishing of the workpiece W (at the time of front surface reference polishing), the over polishing of an edge portion of the workpiece W can be prevented by lowering the retainer 24 and pressing the polishing pad 16 in the periphery of the workpiece W by the retainer 24, and in addition, what is known as a retainer effect that affects the polished shape of the workpiece W can be achieved, and the pressing force can be adjusted as desired. Also at the time of the polishing of the workpiece W (at the time of back surface reference polishing), the over polishing of an edge portion of the workpiece W can be prevented by lowering the retainer 24 and pressing the polishing pad 16 in the periphery of the workpiece W by the retainer 24, and in addition, what is known as a retainer effect that affects the polished shape of the workpiece W can be achieved. Furthermore, a gap can be produced between the retainer 24 and the polishing pad 16 to prevent the retainer 24 from wearing.
As another example, as illustrated in
The polishing head 12 includes a workpiece pressurization plate 36 below the head base portion 20 (shaft portion 20c) and on the inner circumference side of the retainer pressurization unit 22 (head lower portion side wall portion 22b) as illustrated in
As described above, the workpiece pressurization plate 36 is suspended by the head base portion 20 (and the retainer pressurization unit 22) via the suspension members 26c, 26d. The suspension members 26c, 26d according to the present embodiment are each made of a diaphragm made of a rubber material. The workpiece pressurization plate 36 is configured to vertically move with respect to the head base portion 20 (and the retainer pressurization unit 22), through a change in shape of the suspension members 26c, 26d. A configuration is employed in which rotation occurs with rotational force, produced by rotation of the head base portion 20, transmitted through the suspension member 26c. The configuration and the material of the suspension members 26c, 26d are not limited, as long as the workpiece pressurization plate 36 can be suspended to be vertically movable as described above. That is, the diaphragm is not limiting, and bellows or the like may be employed, for example. The rubber material is not limiting, and a resin material, a metal material, or the like may be employed.
A third fluid chamber 42 is provided between the lower surface of the head base portion 20 (lower surface of the lower panel portion 20d) and the upper surface of the workpiece pressurization plate 36 (upper surface of the upper plate 38) (and the suspension member 26c). A fluid can be supplied into and discharged from the inside of the third fluid chamber 42 through a third flow path 44 provided with a third pressure adjustment mechanism 46. With this configuration, the workpiece pressurization plate 36 can be lowered with a positive pressure achieved in the third fluid chamber 42 formed as a closed space, and the workpiece pressurization plate 36 can be raised with a negative pressure achieved in the third fluid chamber 42. In the present embodiment, a configuration is employed in which the fluid is air, and the pneumatic pressure in the third fluid chamber 42 is adjusted. However, this configuration is not limiting, and the fluid may be water, oil, or the like, for example. In the third flow path 44 including a supply path and a discharge path, the supply path and the discharge path may be provided as a single pipe line, or as separate pipe lines. That is, the number and other modes of the pipe line(s) forming the third flow path 44 are not limited. In the present embodiment, as illustrated in
As another example, as illustrated in
As an example different from the above-described configuration in which the workpiece pressurization plate 36 vertically moves through adjustment of the pressure in the third fluid chamber 42 as illustrated in
The polishing head 12 includes the backing material 48 below the workpiece pressurization plate 36. The backing material 48 has a circumference edge portion sandwiched between the lower surface of the retainer pressurization unit 22 (lower surface of the increased width portion 22c) and the upper surface of the retainer 24 to be fixed. The backing material 48 corresponds to a soft member that fixes the workpiece W at the time of front surface reference polishing, and also corresponds to a buffer member that comes into contact with and protects the workpiece W during polishing and transportation of the workpiece W. Thus, the material is formed as a sheet body made of a flexible resin material, a rubber material, and the like, for example.
The backing material 48 includes a suction surface 48a that faces the upper surface Wb of the workpiece W and a pressing surface 48b that is opposite to the suction surface 48a and faces the workpiece pressurization plate 36. In a case that the configuration of the polishing head 12 is described based on the backing material 48, the retainer 24 is provided to the outer circumference portion of the suction surface 48a and the vertically movable retainer pressurization unit 22 is provided to the outer circumference portion of the pressing surface 48b, and the vertically movable workpiece pressurization plate 36 is provided to the center portion of the pressing surface 48b to be contactable with and separable from the pressing surface 48b (see
While not visible in
While the mode of the first flow path 52 is not limited as described above, in the present embodiment, as illustrated in
With the configuration described above, at the time of the polishing of the workpiece W, the control unit 72 vacuumizes the inside of the third fluid chamber 42 to raise the workpiece pressurization plate 36 and forms the first fluid chamber 50 between the workpiece pressurization plate 36 and the backing material 48 as illustrated in
On the other hand, as illustrated in
As illustrated in
The pressing part 23 functions as a stopper that restricts the movement of the workpiece pressurization plate 36 and the retainer pressurization unit 22 in a predetermined direction at the time of the polishing of the workpiece W, and achieves a relative positional relationship between the workpiece pressurization plate 36 and the retainer pressurization unit 22, as well as configurations in the vicinity thereof. As an example, in the present embodiment, when the lower surface of the upper plate 38 (upper edge portion 38a) of the workpiece pressurization plate 36 and the upper surface of the increased width portion 22c of the retainer pressurization unit 22 come into contact with each other via the pressing part 23 formed on the inclined surface 23a at the time of the polishing of the workpiece W (at the time of back surface reference polishing), the lower surface of the workpiece pressurization plate 36 (lower surface of the lower plate 40) comes into contact with the upper surface (pressing surface 48b) of the backing material 48. Thus, a gap therebetween disappears, and the first fluid chamber 50 apparently disappears. In this state, the movement of the workpiece pressurization plate 36 and the retainer pressurization unit 22 in the vertical direction and the horizontal direction is restricted, and a lower end surface IIIB of the retainer 24 is set to be located above a lower end surface IIIA of the workpiece W fixed to the backing material 48, to produce a predetermined gap between the retainer 24 and the polishing pad 16. Specifically, as illustrated in
On the other hand, by appropriately adjusting the shape (thickness in particular) of the retainer 24, the increased width portion 22c, the pressing part 23, the upper plate 38 (upper edge portion 38a) of the workpiece pressurization plate 36, and/or the like, the relative positional relationship between the retainer 24 and the workpiece W can be freely set. Thus, as another example, at the time of the polishing of the workpiece W (at the time of back surface reference polishing), when the lower surface of the upper plate 38 (upper edge portion 38a) of the workpiece pressurization plate 36 and the upper surface of the increased width portion 22c of the retainer pressurization unit 22 come into contact with each other via the pressing part 23, the lower end surface IIIB of the retainer 24 may be set to match the lower end surface IIIA of the workpiece W in the horizontal direction, or to be located below the lower end surface IIIA of the workpiece W. Thus, the pressing part 23 can accurately achieve the height position of the retainer 24, in particular, the relative positional relationship between the retainer 24 and the workpiece W, to contribute to accurate polishing of the workpiece W into a set shape.
At the time of preliminary surface processing for the workpiece pressurization plate 36 and the retainer pressurization unit 22 to achieve the positional relationship described above, the pressing part 23 also functions as a stopper for relative positioning of the workpiece pressurization plate 36 and the retainer pressurization unit 22. In the present embodiment, as illustrated in
As another example, as illustrated in
Furthermore, as illustrated in
The lower plate 40 according to the present embodiment is formed in a porous form as illustrated in
On the other hand, as another example, as illustrated in
As a further example, as illustrated in
While this example only needs to be configured such that the fluid can be discharged from at least the third flow channel 66 through the fifth flow path 68 by the fifth pressure adjustment mechanism 70 to achieve the vacuum, pressurization may be enabled through supplying of the fluid into the third flow channel 66. In this case, opening to the atmosphere is enabled as a matter of course. In the fifth flow path 68 including a supply path and a discharge path, the supply path and the discharge path may be provided as a single pipe line, or as separate pipe lines. That is, the number and other modes of the pipe line(s) forming the fifth flow path 68 are not limited. The fifth pressure adjustment mechanism 70, examples of which include a fluid compressing apparatus, a solenoid valve, and the like, is drivingly controlled by the control unit 72. A plurality of the fifth pressure adjustment mechanisms 70 may be provided. Furthermore, the fluid is not limited and may be water, oil, or the like, for example, but is air when the fluid that is the same as that flowing in the first flow path 52 is selected and applied to the present embodiment.
In the present example, the third flow channel 66 does not communicate with the first flow path 52. Thus, the inside of the first fluid chamber 50 is vacuumized or is opened to the atmosphere by the first pressure adjustment mechanism 54 to bring the workpiece pressurization plate 36 (lower plate 40) and the backing material 48 into close contact with each other. Then, the workpiece pressurization plate and the backing material are brought into closer contact with each other by the fifth pressure adjustment mechanism 70. Thus, the region of the first fluid chamber 50 corresponding to the lower plate 40 can be substantially eliminated, and this region and the gap region 51 can be substantially separated from each other. The same applies to a case where the first flow channel 62 is not configured to communicate with the first flow path 52. Specifically, by bringing the workpiece pressurization plate 36 (lower plate 40) and the backing material 48 into closer contact with each other by the second pressure adjustment mechanism 60, the region of the first fluid chamber 50 corresponding to the lower plate 40 can be substantially eliminated, and this region and the gap region 51 can be substantially separated from each other. With this configuration, the first pressure adjustment mechanism 54 can separately adjust the pressure in the gap region 51, independently from the first fluid chamber 50. Thus, from the state described above, by pressuring, vacuumizing, or opening to the atmosphere, the inside of the gap region 51 through the first flow path 52 using the first pressure adjustment mechanism 54, the pressing force mainly applied to the region corresponding to the gap region 51 from the edge portion (outer circumference portion) of the workpiece W to the periphery of the workpiece W can be adjusted. The region corresponding to the gap region 51 can be arbitrarily set through adjustment of the radial direction width (diameter) of the lower plate 40, the gap width of the gap region 51, and/or the radial direction width of the retainer pressurization unit 22 (increased width portion 22c). For example, a region closer to the center of the workpiece W can be included, or conversely, the region can be expanded to a periphery of the periphery of the workpiece W. With the configuration related to the third flow channel 66 or the first flow channel 62 not communicating with the first flow path 52 thus utilized to adjust the pressing force applied to the region from the edge portion of the workpiece W to the periphery of the workpiece W corresponding to the gap region 51 and the like, the polished shape of the workpiece W can be affected as desired.
Furthermore, with the upper plate 38 and/or the lower plate 40 having an adjusted thickness or made of a material with a certain flexibility, or with the upper plate 38 and/or the lower plate 40 (the lower surfaces of these in particular) formed into a special shape such as a concave lens shape or a convex lens shape, for example, the shape of the upper plate 38 and/or the lower plate 40 can be changed to be deflected upward and/or downward, through adjustment of the pressure in the third fluid chamber 42 and in the second fluid chamber 56. The details will be described below.
Next, the driving unit (not illustrated) of the polishing head 12 will be described. As described above, the driving unit includes the vertical movement driving mechanism (not illustrated) and the rotational driving mechanism (not illustrated) drivingly controlled by the control unit 72, and vertically moves and rotates the polishing head 12 by the operation of vertically moving and rotating the head shaft 18. The vertical movement driving mechanism and the rotational driving mechanism of the driving unit can each be configured by a known mechanism.
Specifically, as a driving source for these vertical movement driving mechanism and rotational driving mechanism, a motor such as a servomotor and the like may be used, and as a linear motion device and a rotation device, a spline mechanism such as a ball screw spline mechanism or a rotary ball spline mechanism and the like may be used. Alternatively, a linear motor or the like including a driving source and a linear motion device integrated may be used, and a linear motor actuator or the like in which a guide mechanism for the linear motion device is further integrated may be used. In this case, a spindle or the like may be used as the rotation device, or a linear motor actuator or the like incorporating the rotation device may be used (none of which is illustrated).
A current detector that detects a load on a motor, an encoder that detects the rotation speed and the rotation angle, a length measurement sensor that detects the vertical gap of the head base portion 20, the retainer pressurization unit 22, the retainer 24, and the like or the vertical gap between these and the polishing pad 16 as the height position of the polishing head 12, and the like may be provided as appropriate, and by adjusting the height position of the polishing head 12 based on the detection values from these, highly precise control is enabled (none of which is illustrated).
As illustrated in
The surface plate 14 is formed to have a disk shape in plan view, and has the upper surface on which the polishing pad 16 is attached (see
Next, a polishing method according to the present embodiment will be described with an example where the polishing head 12 according to the present embodiment (the polishing head 12 illustrated in
First of all, at the time of front surface reference polishing, as illustrated in
As illustrated in
Through the control described above, at the time of the front surface reference polishing according to the present embodiment, the control unit 72 raises the workpiece pressurization plate 36 and lowers the retainer pressurization unit 22, and applies the forces in relatively opposite vertical directions to both configurations. Thus, as illustrated in
With the first fluid chamber 50 vacuumized while the fluid chambers 28, 42, 50, 56 are in the states described above, the workpiece W can be picked up (sucked and lifted). On the other hand, to unload (peel off) the workpiece W, air may be introduced into the first fluid chamber 50 again. In other words, according to the present embodiment, the workpiece W can be fixed (held) and picked up using the backing material 48 as a suction panel, and thus is not formed in a porous form as in the conventional configuration. Thus, at the time of picking up and unloading, the workpiece W can be prevented from having suction marks, and foreign matters can be prevented from mixing into the polishing head 12.
Next, at the time of back surface reference polishing, as illustrated in
At this time, according to the present embodiment, as described above, when the workpiece pressurization plate 36 is lowered, the workpiece pressurization plate 36 and the retainer pressurization unit 22 are brought into contact with each other, and the workpiece pressurization plate 36 and the backing material 48 are brought into contact with each other. In this state, when the back surface reference polishing is performed, as illustrated in
In the present embodiment, the control unit 72 adjusts the pressure in the fourth fluid chamber 28 to be at a level sufficient for supporting the retainer pressurization unit 22 (own weight), whereby a state where the workpiece pressurization plate 36 and the retainer pressurization unit 22 are in contact with each other is maintained. Specifically, predetermined pressure is applied to the retainer pressurization unit 22 with the workpiece pressurization plate 36 being in contact therewith from the above. Thus, generally, the control unit 72 appropriately reduces the pressure in the fourth fluid chamber 28, to maintain the state in which the workpiece pressurization plate 36 and the retainer pressurization unit 22 are in contact with each other, without compromising the pressing force from the workpiece pressurization plate 36. Thus, a predetermined gap can be formed between the retainer 24 and the polishing pad 16 as described above.
In a configuration in which the lower plate 40 is provided with the first flow channel 62 and the first fluid chamber 50 and the second fluid chamber 56 communicate, the control unit 72 vacuumizes the inside of the second fluid chamber 56. With this configuration, bubbles between the workpiece pressurization plate 36 and the backing material 48 can be removed from the first flow channel 62 through the second fluid chamber 56, so that the workpiece pressurization plate and the backing material can be brought into closer contact with each other. At this time, in a configuration in which the first flow channel 62 also communicates with the first flow path 52, the inside of the first fluid chamber 50 is also vacuumized. In a configuration in which the lower plate 40 is provided with the second flow channel 64 and the first fluid chamber 50 and the second fluid chamber 56 do not communicate, the control unit 72 vacuumizes the inside of the first fluid chamber 50. With this configuration, bubbles between the workpiece pressurization plate 36 and the backing material 48 can be removed from the second flow channel 64 through the first flow path 52, so that the workpiece pressurization plate and the backing material can be brought into closer contact with each other. At this time, the inside of the second fluid chamber 56 may be vacuumized or opened to the atmosphere. In a configuration in which the lower plate 40 is provided with the third flow channel 66 and the first fluid chamber 50 and the fifth flow path 68 provided with the fifth pressure adjustment mechanism 70 communicate through the third flow channel 66, the control unit 72 vacuumizes the third flow channel 66 using the fifth pressure adjustment mechanism 70. With this configuration, bubbles between the workpiece pressurization plate 36 and the backing material 48 can be removed from the third flow channel 66 through the fifth flow path 68, so that the workpiece pressurization plate and the backing material can be brought into closer contact with each other. At this time, the inside of the second fluid chamber 56 may be vacuumized or opened to the atmosphere. Thus, the air accumulation between the workpiece pressurization plate 36 and the backing material 48 is removed, whereby the both can be sufficiently brought into close contact with each other with no unevenness. As a result, the back surface reference polishing can be accurately performed with the back surface Wb of the workpiece W more precisely conforming to the shape of the hard workpiece pressurization plate 36 (lower plate 40).
In a configuration including the first flow channel 62 or the third flow channel 66 not communicating with the first flow path 52, the inside of the gap region 51 is pressurized, vacuumized, or opened to the atmosphere through the first flow path 52 using the first pressure adjustment mechanism 54, while maintaining the state where the workpiece pressurization plate 36 and the backing material 48 are sufficiently in close contact with each other. Thus, the pressing force applied to the region corresponding to the gap region 51 such as that from the edge portion of the workpiece W to the periphery of the workpiece W is adjusted, whereby the polished shape of the workpiece W can be affected as desired.
Through the control described above, at the time of the back surface reference polishing according to the present embodiment, the control unit 72 applies force to lower the workpiece pressurization plate 36 and raise the retainer pressurization unit 22, and applies the forces in relatively opposite vertical directions to both configurations. Thus, a characteristic positional relationship is achieved as illustrated in
Furthermore, as described above, with the upper plate 38 and/or the lower plate 40 having an adjusted thickness or made of a material with a certain flexibility, or with the upper plate 38 and/or the lower plate 40 (the lower surfaces of these in particular) formed into a special shape such as a concave lens shape or a convex lens shape, for example, the shape of the upper plate 38 and/or the lower plate 40 can be changed to be deflected upward and/or downward, through adjustment of the pressure in the third fluid chamber 42 and in the second fluid chamber 56.
With this configuration, at the time of the back surface reference polishing, for example, the polishing can be performed in conformity to the back surface Wb of the workpiece W, with the inside of the second fluid chamber 56 vacuumized and the lower plate 40 formed into a desired shape. For example, with the inside of the third fluid chamber 42 vacuumized and the upper plate 38 formed into a desired shape, the lower plate 40 may be sucked on the upper plate 38 with its shape changed through the vacuumizing of the inside of the second fluid chamber, and the polishing can be performed with the shape of the lower plate 40 conforming to the shape of the upper plate 38, and to the back surface Wb of the workpiece W. When the third fluid chamber 42 is used for changing the shape of the workpiece pressurization plate 36 (upper plate 38), the workpiece pressurization plate 36 may be configured to be vertically moved by the driving of the head shaft 18 (the vertical movement driving mechanism of the driving unit) as illustrated in
With the shape change on the center portion side of the workpiece W through changing of the configuration such as the shape of the upper plate 38 and/or the lower plate 40 thus combined with the shape change on the outer circumference portion side of the workpiece W utilizing the first flow channel 62 or the third flow channel 66 not communicating with the first flow path 52 as described above and the gap region 51, the polished shape of the workpiece W can be changed in a wide variety of ways, whereby more precise polishing into a desired shape can be achieved.
According to the present invention, the front surface reference polishing and the back surface reference polishing can both be performed using a single polishing head. Thus, the downtime can be reduced, the facility cost can be reduced, and the facility can be downsized and simplified. Furthermore, since the gap can be formed by separating the workpiece pressurization plate from the backing material, the workpiece can be fixed and picked up using the backing material as a suction panel. Thus, the backing material needs not to be provided with suction holes. As a result, formation of suction marks on the workpiece can be prevented, and mixture of foreign matters into the polishing head can be prevented.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-142800 | Sep 2023 | JP | national |
