JP7787585B2 - Polishing head, polishing device, and polishing method - Google Patents

Description

The present invention relates to a polishing head, a polishing device, and a polishing method.

A known polishing device is a polishing head that is movable up and down and rotatable, and holds and rotates a workpiece while pressing it against a polishing pad for polishing. Another known polishing device polishes the workpiece by pressing the workpiece held on the underside of the polishing head, which is located above a surface plate, against a polishing pad attached to the upper surface of the surface plate, while rotating the surface plate and polishing head to slide relative to each other. This polishing device is a single-sided polishing device that polishes one side of the workpiece.

As described in Patent Document 1 (Japanese Patent No. 5629594), there are typically two polishing methods for polishing using a single-sided polishing machine (see Figure 5 of Patent Document 1). One is back-side reference polishing, in which the back side of the workpiece (the upper surface, which is the surface not to be polished) is fixed to a relatively hard, flat surface and polished. In this case, the front side of the workpiece (the lower surface, which is the polishing surface) is polished according to the shape of the back side, i.e., the shape of the above-mentioned flat surface of the polishing head. On the other hand, the other is front-side reference polishing, in which the back side of the workpiece is fixed to a relatively soft, elastic surface and polished. In this case, the front side of the workpiece is polished according to the shape of the front side.

Patent No. 5629594

Workpiece polishing is carried out using either front surface polishing or back surface polishing depending on the purpose.

However, because conventional polishing heads for performing front-side reference polishing and back-side reference polishing have different basic configurations, it was necessary to change polishing heads or install multiple polishing devices depending on the polishing method. This resulted in problems such as downtime due to polishing head replacement, increased equipment costs due to the use of multiple polishing heads or polishing devices, and larger, more complex equipment.

Furthermore, in conventional polishing heads (polishing devices), when fixing the backside of a workpiece to a relatively soft, elastic surface, the soft material was formed porous as suction holes, through which air was sucked in to fix the workpiece by suction. As a result, there was a risk of suction marks being left on the workpiece when it was fixed or picked up. Furthermore, when picking up the workpiece, water, slurry, and other foreign matter could be sucked into the polishing head along with the air through the suction holes, causing problems with the polishing head.

The present invention was made in consideration of the above circumstances, and aims to provide a polishing head, polishing device, and polishing method that can perform both front-side and back-side reference polishing with a single polishing head, reduce downtime, cut equipment costs, and simplify and downsize the equipment, while also preventing suction marks on the workpiece and the intrusion of foreign matter into the polishing head.

The present invention solves the above problem by the solution described below as one embodiment.

The polishing head according to the present invention is a polishing head that is fixed to a head shaft that is movable up and down and rotatable, and that holds and rotates a workpiece while pressing it against a polishing pad for polishing, and that includes: a backing material having an adsorption surface that faces the upper surface of the workpiece and a press surface on the opposite side of the adsorption surface; a workpiece pressure plate that is movable up and down and is provided in the center of the press surface so as to be able to approach and separate from the press surface; a first fluid chamber provided between the workpiece pressure plate and the backing material; and a first pressure adjustment mechanism that adjusts the pressure in the first fluid chamber, and a control unit controls the pressure in the first fluid chamber to perform surface-based polishing by pressing the workpiece from above in a state where the lower surface of the workpiece pressure plate and the press surface of the backing material are separated and the upper surface of the workpiece and the adsorption surface of the backing material are in contact with each other; and and back surface reference polishing, in which the workpiece is pressed from above while the lower surface of the workpiece pressure plate is in contact with the press surface of the backing material and while the upper surface of the workpiece is in contact with the suction surface of the backing material; and the control unit further comprises a retainer provided on the outer periphery of the suction surface and a retainer pressure unit provided on the outer periphery of the press surface and capable of moving up and down, wherein the control unit applies forces in opposite directions relative to the retainer pressure unit and the workpiece pressure plate, so that in the front surface reference polishing, polishing is performed with the lower end surface of the workpiece pressure plate positioned relatively higher than the lower end surface of the retainer pressure unit, and in the back surface reference polishing, polishing is performed with the lower end surface of the workpiece pressure plate and the lower end surface of the retainer pressure unit horizontally aligned, or with the lower end surface of the workpiece pressure plate positioned relatively lower than the lower end surface of the retainer pressure unit .

This allows both front surface and back surface reference polishing to be performed with a single polishing head. Furthermore, because the workpiece pressure plate can be separated from the backing material to form a gap, the backing material can be used as a suction cup to secure and pick up the workpiece. This eliminates the need to provide suction holes in the backing material, preventing suction marks on the workpiece and the entry of foreign matter into the polishing head.

Furthermore, the polishing head according to the present invention preferably includes a pressing section that abuts the workpiece pressure plate and the retainer pressure section to fix them relative to each other, and that functions as a stopper that restricts movement of the workpiece pressure plate and the retainer pressure section in a predetermined direction during polishing of the workpiece, thereby creating a relative positional relationship.

As another example of the positional relationship, a gap can be formed between the retainer and the polishing pad when the workpiece is pressed against the polishing pad with the workpiece pressure plate and the retainer pressure portion abutting against each other via the pressing portion during backside reference polishing. This prevents contact between the retainer and the polishing pad during backside reference polishing, thereby preventing wear on the retainer.

Furthermore, the workpiece pressure plate is preferably composed of two layers, an upper plate and a lower plate, and further includes a second fluid chamber between the upper plate and the lower plate, and a second pressure adjustment mechanism for adjusting the pressure within the second fluid chamber. The lower plate preferably has a flow path connecting the first fluid chamber and the second fluid chamber. This allows air bubbles between the workpiece pressure plate and the backing material to be removed through the flow path and the second fluid chamber by creating a vacuum when the workpiece pressure plate and the backing material are brought into contact and integrated during backside reference polishing, thereby further improving adhesion between them. The flow path can be formed, for example, by using a porous material for the lower plate.

Alternatively, the workpiece pressure plate preferably has a communication passage that connects the first fluid chamber with the first passage in which the first pressure adjustment mechanism is provided. In this way, when the workpiece pressure plate and backing material are brought into contact and integrated during backside reference polishing, a vacuum is created inside the first fluid chamber, which removes air bubbles between the workpiece pressure plate and backing material from the communication passage through the first passage, thereby further improving adhesion between them. As one example, the communication passage can be formed as a groove on the underside of the workpiece pressure plate.

Alternatively, the workpiece pressure plate preferably has a passageway that connects the first fluid chamber with a fifth passageway in which a fifth pressure adjustment mechanism is provided, and the fifth pressure adjustment mechanism is preferably configured to be able to evacuate at least the passageway via the fifth passageway. In this way, when the workpiece pressure plate and backing material are brought into contact and integrated during backside reference polishing, the passageway is evacuated via the fifth passageway by the fifth pressure adjustment mechanism, thereby removing air bubbles between the workpiece pressure plate and backing material from the passageway through the fifth passageway, thereby further improving adhesion between them.

The polishing head according to the present invention may further include a head base portion fixed to the head shaft, and the workpiece pressure plate may be fixed to the head base portion and move up and down by driving the head shaft. The control unit may be configured to control the application of a downward force to the workpiece pressure plate by applying a driving force that lowers the workpiece pressure plate via the head shaft during the backside reference polishing. Alternatively, the polishing head according to the present invention may further include a head base portion fixed to the head shaft, and the workpiece pressure plate may be suspended or slidably attached to the head base portion, and move up and down by adjusting the pressure in a third fluid chamber provided between the head base portion and the workpiece pressure plate with a third pressure adjustment mechanism. The control unit may be configured to control the application of a downward force to the workpiece pressure plate by pressurizing the third fluid chamber during the backside reference polishing.

The polishing device according to the present invention is also characterized by being equipped with the polishing head according to the present invention.

The polishing method of the present invention involves pressing a workpiece held by a polishing head against a polishing pad for polishing, the polishing head comprising: a backing material having an adsorption surface facing the top surface of the workpiece and a press surface opposite the adsorption surface; and a workpiece pressure plate mounted in the center of the press surface so as to be able to approach and separate from the press surface and movable up and down. The method switches between front-side reference polishing, in which the workpiece is pressed from above by raising the workpiece pressure plate to form an enclosed space between it and the backing material and pressurizing the enclosed space, thereby separating the lower surface of the workpiece pressure plate from the press surface of the backing material and bringing the upper surface of the workpiece into contact with the adsorption surface of the backing material; and back-side reference polishing, in which the enclosed space is evacuated or opened to the atmosphere and a downward force is applied to the workpiece pressure plate, bringing the lower surface of the workpiece pressure plate into contact with the press surface of the backing material and bringing the upper surface of the workpiece into contact with the adsorption surface of the backing material, thereby bringing the upper surface of the workpiece into contact with the adsorption surface of the backing material.

Furthermore, by using a polishing head further equipped with a retainer provided on the outer periphery of the suction surface and a retainer pressure unit provided on the outer periphery of the press surface and movable up and down, during front-side reference polishing, the retainer pressure unit can be lowered to press the polishing pad around the workpiece with the retainer, and during back-side reference polishing, a gap can be formed between the lower end surface of the retainer and the polishing pad.

According to the present invention, both front surface reference polishing and back surface reference polishing can be performed with a single polishing head. This reduces downtime, cuts equipment costs, and simplifies and downsizes the equipment. Furthermore, because the workpiece pressure plate can be separated from the backing material to form a gap, the backing material can be used as a suction cup to secure and pick up the workpiece. This eliminates the need to provide suction holes in the backing material, preventing suction marks on the workpiece and the entry of foreign matter into the polishing head.

1 is a schematic view (front view) showing an example of a polishing head according to an embodiment of the present invention. 1 is a schematic view (front cross-sectional view) showing an example of a polishing head according to an embodiment of the present invention, illustrating an example of a state during surface-reference polishing. FIG. 2 is a schematic view (front cross-sectional view) showing an example of a polishing head according to an embodiment of the present invention, illustrating an example of a state during back surface reference polishing. FIG. 4 is a schematic view (front cross-sectional view) showing another example of the polishing head shown in FIG. 3 . FIG. 4 is a schematic view (front cross-sectional view) showing another example of the polishing head shown in FIG. 3 . FIG. 4 is a schematic view (front cross-sectional view) showing another example of the polishing head shown in FIG. 3 . FIG. 3 is a schematic view (front cross-sectional view) showing another example of the polishing head shown in FIG. 2 . FIG. 3 is a schematic view (front cross-sectional view) showing another example of the polishing head shown in FIG. 2 . FIG. 3 is a schematic view (front cross-sectional view) showing another example of the polishing head shown in FIG. 2 . 4 is an explanatory diagram illustrating an example of a surface finishing process for the polishing head shown in FIG. 3. FIG. 11A and 11B are explanatory views illustrating an example of a polishing method according to the present embodiment, in which FIG. 11A is an explanatory view illustrating front surface-referenced polishing, and FIG. 11B and FIG. 11C are explanatory views illustrating back surface-referenced polishing.

(Polishing head)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram (front view) showing an example of a polishing head 12 according to this embodiment. FIGS. 2 and 3 are schematic diagrams (front cross-sectional views) showing examples of the polishing head 12 according to this embodiment. Of these, FIG. 2 shows an example of a state during front-side reference polishing, and FIG. 3 shows an example of a state during back-side reference polishing, but the configurations are identical. Therefore, for the explanation of the configuration, reference will be made to FIGS. 1 and 3, and also to FIG. 2 as appropriate. Also, FIGS. 4 to 9 are schematic diagrams (front cross-sectional views) showing other examples of the polishing head 12 according to this embodiment, and these drawings will also be referenced as appropriate. Of these, FIGS. 4 to 6 show other examples of the polishing head 12 shown in FIG. 3, and FIGS. 7 to 9 show other examples of the polishing head 12 shown in FIG. 2. Because the polishing head 12 is a component of the polishing apparatus 10, FIGS. 1 to 9 are also schematic views of the polishing apparatus 10 according to this embodiment, showing peripheral components such as the platen 14 and polishing pad 16.

As shown in Figures 1 and 3, the polishing head 12 of this embodiment moves up and down and rotates a workpiece W held horizontally on its underside with its polishing surface Wa facing downward. In the polishing apparatus 10, the workpiece W is pressed from above against a polishing pad 16 attached to the upper surface of a surface plate 14 that rotates in a horizontal plane, polishing the polishing surface Wa of the workpiece W. The workpiece W is a flat (particularly disc-shaped) object to be polished, made of, for example, a semiconductor material or glass material. The polishing surface Wa of the workpiece W is the front surface Wa, which corresponds to the lower surface Wa, and the non-polished surface Wb of the workpiece W is the back surface Wb, which corresponds to the upper surface Wb.

The polishing head 12 has a head base portion 20 at its top. The head base portion 20 has a disk-shaped head base top portion 20a, a cylindrical head upper sidewall portion 20b that protrudes downward from the outer end of the head base top portion 20a, and a shaft portion 20c that protrudes downward from the center of the underside of the head base top portion 20a. As a result, the head base portion 20 protects the upper portion of the polishing head 12 by covering it with a lid. The center of the top surface of the head base portion 20 (the top surface of the head base top portion 20a) is fixed to a head shaft 18 that can move up and down and rotate. The head shaft 18 moves up and down due to a vertical movement drive mechanism (not shown) of the drive unit. Therefore, the head base portion 20 moves up and down together with the head shaft 18. The head shaft 18 rotates about its axis due to a rotation drive mechanism (not shown) of the drive unit. Therefore, the head base portion 20 rotates about the head shaft 18. In this way, the polishing head 12 is movable up and down and rotated by driving the head shaft 18. The up and down movement drive mechanism and rotation drive mechanism of the drive unit can both be constructed using known mechanisms. Specific examples will be described later.

1 and 3, the polishing head 12 has a retainer pressure member 22 at its lower portion (below the head base portion 20). The retainer pressure member 22 includes a retainer pressure top plate portion 22a located inside the polishing head 12 and below the head base top plate portion 20a, a head lower side wall portion 22b protruding downward from the outer end of the retainer pressure top plate portion 22a, and an expanded portion 22c extending a predetermined width inward on the underside of the head lower side wall portion 22b. As a result, the retainer pressure member 22 protects the lower outer periphery of the polishing head 12 by having the head lower side wall portion 22b cover it. A retainer 24 is provided on the underside of the retainer pressure member 22 (below the expanded portion 22c) to press the polishing pad 16 around the workpiece W, sandwiching a backing material 48 (described later) between them.

As shown in FIG. 3, the retainer pressure member 22 (retainer pressure top plate 22a) is suspended on its inner periphery from the outer periphery of the shaft 20c of the head base 20 via a suspension member 26a. It is suspended on its outer periphery from the inner periphery of the head upper side wall 20b of the head base 20 via a suspension member 26b. These suspension members 26a and 26b may be integrally configured as shown in FIG. 4.

In this manner, the retainer pressure applying portion 22 is suspended from the head base portion 20 via the suspension members 26a and 26b. In this embodiment, the suspension members 26a and 26b are both formed from diaphragms made of a rubber material, and the retainer pressure applying portion 22 is configured to move up and down relative to the head base portion 20 via changes in the shape of the suspension members 26a and 26b. Furthermore, when the head base portion 20 rotates, the rotational force is transmitted via the suspension members 26a and 26b, causing the retainer pressure applying portion 22 to rotate. The configuration and material of the suspension members 26a and 26b are not limited as long as they can suspend the retainer pressure applying portion 22 so that it can move up and down as described above. In other words, they are not limited to diaphragms, and can be, for example, bellows. Furthermore, they are not limited to rubber materials, and can be resin materials, metal materials, etc.

Here, a fourth fluid chamber 28 is provided between the underside of the head base portion 20 (the underside of the head base top plate portion 20a) and the upper surface of the retainer pressure portion 22 (the upper surface of the retainer pressure top plate portion 22a) (and the hanging members 26a, 26b). Fluid can be supplied to and discharged from the fourth fluid chamber 28 via a fourth flow path 30, in which a fourth pressure adjustment mechanism 32 is provided. This allows the fourth fluid chamber 28, formed as an enclosed space, to be pressurized positively to lower the retainer pressure portion 22 (retainer 24), or to be pressurized negatively to raise the retainer pressure portion 22 (retainer 24). In this embodiment, the fluid is air, and the air pressure in the fourth fluid chamber 28 is adjusted. However, this configuration is not limited to this, and the fluid may be water, oil, or the like. The fourth flow path 30, which consists of a supply path and a discharge path, may be provided as the same pipeline or as separate pipelines. In other words, the number of pipelines constituting the fourth flow path 30 and other configurations are not limited. The fourth pressure adjustment mechanism 32 is exemplified by a fluid compressor or a solenoid valve, and is driven and controlled by the control unit 72. The control unit 72, which is provided in a predetermined location within the polishing apparatus 10, is composed of a CPU and memory, and performs predetermined operations based on a preset operating program and/or setting signals input from an operation unit (not shown). Multiple fourth pressure adjustment mechanisms 32 may be provided.

In this way, adjusting the pressure within the fourth fluid chamber 28 moves the retainer pressure section 22 up and down, allowing the vertical position of the retainer 24 to be adjusted. Therefore, when polishing the workpiece W (when polishing with a front surface as the reference), the retainer 24 can be lowered to press against the polishing pad 16 around the workpiece W, preventing over-polishing of the edge of the workpiece W and otherwise affecting the polished shape of the workpiece W, thereby providing a so-called retainer effect, and the pressing force can be adjusted as desired. On the other hand, when polishing the workpiece W (when polishing with a back surface as the reference), the retainer 24 can also be lowered to press against the polishing pad 16 around the workpiece W, preventing over-polishing of the edge of the workpiece W and otherwise affecting the polished shape of the workpiece W, thereby providing a so-called retainer effect. Furthermore, creating a gap between the retainer 24 and the polishing pad 16 can also prevent wear on the retainer 24.

As another example, as shown in FIG. 5, the retainer pressure unit 22 (retainer pressure top plate 22a) may be provided in slidable contact with the shaft 20c and head upper side wall 20b of the head base unit 20 via sealing members 34a and 34b, such as O-rings, respectively, instead of the hanging members 26a and 26b. "Close contact" here refers to the pressure in the fourth fluid chamber 28 being adjusted by the fourth pressure adjustment mechanism 32, such that the retainer pressure unit 22 is in close contact with the head base unit 20 to the extent that it can slide up and down relative to the head base unit 20. This allows the sealing members 34a and 34b to exert the same effect as the hanging members 26a and 26b and can replace the hanging members 26a and 26b. Additionally, hanging members 26a, 26b may be provided on one side of the inner and outer periphery of the retainer pressure top plate 22a, and sealing members 34a, 34b may be provided on the other side (not shown). Furthermore, in addition to the sealing members 34a, 34b, a rotational force transmission mechanism (e.g., a rotational force transmission pin) that assists in transmitting the rotational force of the head base portion 20 may also be provided.

Next, as shown in FIG. 3, the polishing head 12 includes a workpiece pressure plate 36 below the head base portion 20 (shank portion 20c) and on the inner periphery of the retainer pressure portion 22 (head lower sidewall portion 22b). The workpiece pressure plate 36 is composed of two layers: an upper plate 38 and a lower plate 40. The workpiece pressure plate 36 corresponds to a rigid member that secures the workpiece W during backside reference polishing. Therefore, for example, both the upper plate 38 and the lower plate 40 are made of ceramic or the like. However, one or both may be made of other materials with a certain degree of flexibility. In this embodiment, as shown in FIG. 3, the upper plate 38 has an upper edge portion 38a that protrudes upward from the outer end thereof, and the upper plate 38 has an overall rimmed, circular tray-like shape. The head base portion 20 also has a lower plate portion 20d that extends a predetermined width outward from the lower surface of the shaft portion 20c. Using this configuration, the workpiece pressure plate 36 (upper edge 38a) is suspended on the inner periphery from the lower platen 20d of the head base 20 via suspension members 26c, but this configuration is not limited to this. Also, on the outer periphery, it is suspended on the head lower side wall 22b of the retainer pressure part 22 via suspension members 26d. These suspension members 26c and 26d may also be configured as a single unit, as shown in Figure 4.

In this manner, the work pressure plate 36 is suspended from the head base portion 20 (and the retainer pressure portion 22) via the suspension members 26c and 26d. In this embodiment, the suspension members 26c and 26d are both formed from diaphragms made of a rubber material, and the work pressure plate 36 is configured to move up and down relative to the head base portion 20 (and the retainer pressure portion 22) via changes in the shape of the suspension members 26c and 26d. Furthermore, when the head base portion 20 rotates, the rotational force is transmitted via the suspension member 26c, causing the work pressure plate 36 to rotate. The configuration and material of the suspension members 26c and 26d are not limited as long as they can suspend the work pressure plate 36 so that it can move up and down as described above. In other words, they are not limited to diaphragms, and may be, for example, bellows. Furthermore, they are not limited to rubber materials, and may be resin materials, metal materials, or other materials.

Here, a third fluid chamber 42 is provided between the lower surface of the head base portion 20 (the lower surface of the lower plate portion 20d) and the upper surface of the workpiece pressure plate 36 (the upper surface of the upper plate 38) (and the hanging member 26c). Fluid can be supplied to and discharged from the third fluid chamber 42 via a third flow path 44, in which a third pressure adjustment mechanism 46 is provided. This allows the third fluid chamber 42, formed as an enclosed space, to be pressurized positively to lower the workpiece pressure plate 36, or to be pressurized negatively to raise the workpiece pressure plate 36. In this embodiment, the fluid is air, and the air pressure within the third fluid chamber 42 is adjusted. However, this configuration is not limited; for example, the fluid may be water, oil, or the like. The third flow path 44, consisting of a supply path and a discharge path, may be provided as the same conduit or as separate conduits. In other words, the number and other configurations of the conduits constituting the third flow path 44 are not limited. In this embodiment, as shown in FIG. 3, for example, the interior of the shaft portion 20c is hollow. This hollow portion 45 may conceptually be understood as part of the third fluid chamber 42 or part of the third flow path 44. The third pressure adjustment mechanism 46 is exemplified by a fluid compression device or a solenoid valve, and is driven and controlled by the control unit 72. Multiple third pressure adjustment mechanisms 46 may be provided.

As another example, as shown in FIG. 5, the workpiece pressure plate 36 (upper edge 38a) may be provided in slidable contact with the lower platen 20d of the head base portion 20 and the head lower sidewall 22b of the retainer pressure portion 22 via seal members 34c and 34d similar to the seal members 34a and 34b described above, instead of the hanger members 26c and 26d. Alternatively, a hanger member (26c or 26d) may be provided on one side of the inner or outer periphery of the upper edge 38a, and a seal member (34c or 34d) may be provided on the other side (not shown). In addition to the seal members 34c and 34d, a rotational force transmission mechanism (e.g., a rotational force transmission pin) that assists in transmitting the rotational force of the head base portion 20 may also be provided.

As an alternative to the configuration shown in FIG. 3, in which the work pressure plate 36 moves up and down by adjusting the pressure in the third fluid chamber 42, as shown in FIG. 6, the work pressure plate 36 may be fixed to the head base portion 20 (in FIG. 6, the lower platen portion 20d is used as an example), so that it moves up and down and rotates together with the up and down movement and rotation of the head base portion 20 driven by the head shaft 18. In this example, as shown in FIG. 6, the third fluid chamber 42 as a pressure adjustment space does not necessarily have to be provided. Alternatively, the head base portion 20 and the work pressure plate 36 (particularly the upper plate 38) may be configured as a single unit (not shown).

The polishing head 12 also has a backing material 48 below the workpiece pressure plate 36. The backing material 48 is fixed by sandwiching its peripheral edge between the lower surface of the retainer pressure section 22 (the lower surface of the widened section 22c) and the upper surface of the retainer 24. The backing material 48 corresponds to a soft member that secures the workpiece W during surface-reference polishing, and also corresponds to a buffer member that comes into contact with and protects the workpiece W during polishing and transport. For this reason, it is made, for example, of a sheet made of a flexible resin material, rubber material, or the like.

The backing material 48 has an adsorption surface 48a that faces the upper surface Wb of the workpiece W, and a press surface 48b, which is the surface opposite the adsorption surface 48a and faces the workpiece pressure plate 36. Describing the configuration of the polishing head 12 from the perspective of the backing material 48, a retainer 24 is provided on the outer periphery of the adsorption surface 48a, a retainer pressure unit 22 that can move up and down is provided on the outer periphery of the press surface 48b, and a workpiece pressure plate 36 that can move up and down is provided in the center of the press surface 48b so that it can be brought into contact with and separated from the press surface 48b (see Figures 11A, 11B, and 11C).

Although not visible in FIG. 3, referring to FIG. 2, a first fluid chamber 50 is provided between the lower surface of the workpiece pressure plate 36 (the lower surface of the lower plate 40) and the upper surface of the backing material 48 (the press surface 48b). Fluid can be supplied to and discharged from the first fluid chamber 50 via a first flow path 52 in which a first pressure adjustment mechanism 54 is provided. In this embodiment, the fluid is air, and the air pressure in the first fluid chamber 50 is adjusted. However, this configuration is not limited to this; for example, the fluid may be water, oil, or the like. The first flow path 52, which consists of a supply path and a discharge path, may be provided as the same conduit or as separate conduits. In other words, the number of conduits constituting the first flow path 52 and other configurations are not limited. The first pressure adjustment mechanism 54 may be, for example, a fluid compressor or a solenoid valve, and is driven and controlled by the control unit 72. Multiple first pressure adjustment mechanisms 54 may be provided.

As mentioned above, the shape of the first flow path 52 is not limited. However, in this embodiment, as shown in FIG. 3, the first flow path 52 extends from the first fluid chamber 50, which is sandwiched between the lower surface of the lower plate 40 and the upper surface of the backing material 48, through a gap region 51 formed between the side surface (outer periphery) of the lower plate 40 and the side surface (inner periphery) of the retainer pressure portion 22 (widened portion 22c). The width of this gap region 51 can be adjusted by adjusting the radial width (diameter) of the lower plate 40 and/or the radial width of the retainer pressure portion 22 (widened portion 22c). The region of the backing material 48 corresponding to this gap region 51 is a clearance region that does not correspond to either the retainer pressure portion 22 (retainer 24) or the workpiece pressure plate 36 (lower plate 40). Therefore, this region is not directly pressed by the retainer pressure member 22 and the workpiece pressure member 36 (lower plate 40). However, by communicating with the first fluid chamber 50, this region is subjected to pressure adjustment by the first pressure adjustment mechanism 54 together with the first fluid chamber 50. However, the first flow path 52 may of course communicate with the first fluid chamber 50 without passing through the gap region 51, or the gap region 51 itself may not be provided (both not shown). A configuration in which the gap region 51 itself is not provided may be one in which the side surface (outer periphery) of the lower plate 40 and the side surface (inner periphery) of the retainer pressure member 22 (widened portion 22c) are slidably and closely attached via sealing members similar to the aforementioned sealing members 34a and 34b (not shown).

With the above configuration, when polishing the workpiece W, the control unit 72, as shown in FIG. 2, creates a vacuum inside the third fluid chamber 42, raises the workpiece pressure plate 36, and forms a first fluid chamber 50 between the workpiece pressure plate 36 and the backing material 48, and then pressurizes the first fluid chamber 50. This allows polishing pressure to be applied to the workpiece W with the back surface Wb of the workpiece W fixed to the soft backing material 48, thereby performing surface-reference polishing.

Meanwhile, as shown in FIG. 3, the control unit 72 pressurizes the third fluid chamber 42 to lower the workpiece pressure plate 36, bringing the workpiece pressure plate 36 into contact with the backing material 48, and creates a vacuum or opens the first fluid chamber 50 to the atmosphere to bring the workpiece pressure plate 36 and the backing material 48 into close contact. The control unit 72 then further pressurizes the third fluid chamber 42. Alternatively, in the configuration of the embodiment shown in FIG. 6, the control unit 72 drives the head shaft 18 to lower the workpiece pressure plate 36, bringing the workpiece pressure plate 36 into contact with the backing material 48, and creates a vacuum or opens the first fluid chamber 50 to the atmosphere to bring the workpiece pressure plate 36 and the backing material 48 into close contact. The control unit 72 then applies a driving force via the head shaft 18 to further lower the workpiece pressure plate 36. This allows polishing pressure to be applied to the workpiece W while the back surface Wb of the workpiece W is substantially fixed to the hard workpiece pressure plate 36, thereby enabling back surface reference polishing.

As shown in FIG. 3, a pressing portion 23 is provided that abuts the workpiece pressure plate 36 against the retainer pressure portion 22 and fixes it relative to the workpiece pressure plate 36 when the workpiece pressure plate 36 is lowered. In this embodiment, the pressing portion 23 is formed as an inclined surface 23a that slopes relative to the horizontal and vertical directions at a predetermined portion of the retainer pressure portion 22 (the upper surface of the widened portion 22c) and a corresponding predetermined portion of the workpiece pressure plate 36 (the outer end of the lower surface of the upper plate 38). However, this configuration is not limited to this. As another example, the pressing portion 23 may be formed as a spherical or arcuate surface centered on the rotation axis of the workpiece pressure plate 36 and the retainer pressure portion 22. This provides a centering effect, making the entire polishing head 12 more stable. The pressing portion 23 may also be formed on a horizontal surface. Additionally, in this embodiment, the portion of the retainer pressure member 22 that corresponds to the pressing portion 23 is formed as a separate member from the main body of the retainer pressure member 22, but the upper surface of the widened portion 22c may be machined into a predetermined shape and formed as part of the main body of the retainer pressure member 22.

The pressing portion 23 functions as a stopper that restricts movement of the workpiece pressure plate 36 and the retainer pressure portion 22 in a predetermined direction during polishing of the workpiece W, thereby creating a relative positional relationship between the workpiece pressure plate 36, the retainer pressure portion 22, and ultimately the components in their vicinity. As an example, in this embodiment, when the workpiece W is polished (during backside reference polishing), the lower surface of the upper plate 38 (upper edge portion 38a) of the workpiece pressure plate 36 abuts against the upper surface of the widened portion 22c of the retainer pressure portion 22 via the pressing portion 23 formed on the inclined surface 23a. This causes the lower surface of the workpiece pressure plate 36 (lower surface of the lower plate 40) to come into contact with the upper surface (press surface 48b) of the backing material 48, eliminating the gap between them and apparently eliminating the first fluid chamber 50. In this state, vertical and horizontal movement of the workpiece pressure plate 36 and the retainer pressure portion 22 is restricted, and the lower end surface IIIB of the retainer 24 is positioned above the lower end surface IIIA of the workpiece W fixed to the backing material 48, creating a predetermined gap between the retainer 24 and the polishing pad 16. Specifically, as shown in FIG. 3, the lower end surface IIIE of the retainer pressure portion 22 and the lower end surface IIIC of the workpiece pressure plate 36 (the lower end surface IIID of the lower plate 40) are aligned horizontally, so that the lower end surface IIIB of the retainer 24, which is thinner than the workpiece W, is positioned above the lower end surface IIIA of the workpiece W. This prevents contact between the retainer 24 and the polishing pad 16 and prevents wear on the retainer 24.

Meanwhile, the relative positional relationship between the retainer 24 and the workpiece W can be freely set by appropriately adjusting the shape (particularly the thickness) of the retainer 24, the widened portion 22c, the pressing portion 23, and/or the upper plate 38 (upper edge 38a) of the workpiece pressure plate 36. Therefore, as another example, when the lower surface of the upper plate 38 (upper edge 38a) of the workpiece pressure plate 36 abuts against the upper surface of the widened portion 22c of the retainer pressure portion 22 via the pressing portion 23 during polishing of the workpiece W (backside reference polishing), the lower end surface IIIB of the retainer 24 can be set to be horizontally aligned with the lower end surface IIIA of the workpiece W or positioned lower than the lower end surface IIIA of the workpiece W. In this way, the pressing portion 23 accurately determines the height position of the retainer 24, particularly its relative positional relationship with the workpiece W, contributing to accurately polishing the workpiece W to the set shape.

The pressing portion 23 also functions as a stopper that positions the work pressure plate 36 and the retainer pressure portion 22 relative to each other during the preliminary surface finishing processing of the work pressure plate 36 and the retainer pressure portion 22 to create the above-mentioned positional relationship. In this embodiment, as shown in Figure 10, the work pressure plate 36 and the retainer pressure portion 22 are ground while being abutted and fixed relative to each other via the pressing portion 23, thereby enabling surface finishing so that the lower end surface XE of the retainer pressure portion 22 and the lower end surface XC of the work pressure plate 36 (lower end surface XD of the lower plate 40) are aligned horizontally. Although the details of the structure will be described later, in a configuration in which the second fluid chamber 56 is sealed as shown in FIG. 8, rather than a configuration in which the second fluid chamber 56 between the upper plate 38 and the lower plate 40 is connected by the first communication flow path 62 as shown in FIG. 10, the lower end surface XD of the lower plate 40 may be formed into a shape different from a horizontal plane by performing a surface finishing process by pressurizing the second fluid chamber 56 or by creating a vacuum or opening it to the atmosphere.

As another example, the pressing portion 23 may be configured as shown in FIG. 7, with a positioning pin 23b erected on a horizontal plane and a fitting hole 23c into which the positioning pin 23b fits, at a predetermined portion of the retainer pressure portion 22 (the upper surface of the widened portion 22c) and a corresponding predetermined portion of the workpiece pressure plate 36 (the outer edge of the lower surface of the upper plate 38). (Note, however, that FIG. 7 illustrates another example of the polishing head 12 shown in FIG. 2.) In this example, as shown in FIG. 7, the positioning pin 23b is fixed to the retainer pressure portion 22 and the fitting hole 23c is provided on the workpiece pressure plate 36. However, conversely, the positioning pin 23b may be fixed to the workpiece pressure plate 36 and the fitting hole 23c may be provided on the retainer pressure portion 22. As in the present embodiment, this example also restricts movement of the workpiece pressure plate 36 and the retainer pressure portion 22 in a predetermined direction (particularly the horizontal direction), thereby creating a predetermined gap between the retainer 24 and the polishing pad 16. Furthermore, this embodiment effectively prevents circumferential (horizontal) misalignment between the retainer pressure member 22 and the workpiece pressure plate 36, especially during surface finishing. This allows the lower end surface XE of the retainer pressure member 22 to be aligned with the lower end surface XC of the workpiece pressure plate 36 (the lower end surface XD of the lower plate 40) with greater precision. The size, shape, number, and other aspects of the positioning pins 23b are not limited. Furthermore, by forming the pressing member 23 with an undulating or uneven surface, etc., and configuring the workpiece pressure plate 36 and the retainer pressure member 22 to fit together, it is possible to effectively prevent circumferential (horizontal) misalignment between the retainer pressure member 22 and the workpiece pressure plate 36, especially during surface finishing, and achieve the same effect as this embodiment (positioning pins 23b).

As shown in FIG. 3 , a second fluid chamber 56 is provided between the lower surface of the upper plate 38 and the upper surface of the lower plate 40 of the two-layer workpiece pressure plate 36. In this embodiment, the lower plate 40, like the upper plate 38, has an upper edge 40a that protrudes upward from its outer edge, forming a rimmed, circular tray-like shape overall, thereby forming a space that defines the second fluid chamber 56. However, this is not a limitation. For example, the space may be formed by forming the lower surface of the upper plate 38 or the upper surface of the lower plate 40 into a concave lens shape. Fluid can be supplied to and discharged from the second fluid chamber 56 via a second flow path 58 in which a second pressure adjustment mechanism 60 is provided. In this embodiment, the fluid is air, and the air pressure in the second fluid chamber 56 is adjusted. However, this configuration is not a limitation; for example, the fluid may be water, oil, or the like. The second flow path 58, which consists of a supply path and a discharge path, may be provided as the same conduit or as separate conduits. In other words, there are no limitations on the number of conduits that make up the second flow path 58 or on other configurations. The second pressure adjustment mechanism 60 is exemplified by a fluid compression device or a solenoid valve, and is driven and controlled by the control unit 72. Multiple second pressure adjustment mechanisms 60 may be provided.

As shown in FIG. 3, the lower plate 40 according to this embodiment is porous, and the first fluid chamber 50 and the second fluid chamber 56 are connected by multiple fine flow paths 62 (first flow paths 62). This allows the workpiece pressure plate 36 and the backing material 48 to be brought into contact and integrated during polishing of the workpiece W (backside reference polishing). By creating a vacuum within the second fluid chamber 56, air bubbles between the workpiece pressure plate 36 and the backing material 48 can be removed through the first flow paths 62 and the second fluid chamber 56, further enhancing their adhesion. The first flow paths 62 may be formed by the lower plate 40 being made of a porous material, or may be designed into a non-porous material. The size, shape, number, and other aspects of the first flow paths 62 are not limited. The first flow passage 62 formed by the lower plate 40 being made of a porous material may also communicate with the first flow passage 52 via the gap region 51, but the first flow passage 62 that is designed into a non-porous material may also be configured to communicate with the first flow passage 52, or not.

As another example, as shown in FIG. 8, instead of the first flow passage 62, a flow passage 64 (second flow passage 64) connecting the first fluid chamber 50 and the first flow passage 52 may be provided in the workpiece pressure plate 36 (lower plate 40) (however, FIG. 8 illustrates another example of the polishing head 12 shown in FIG. 2). This also allows air bubbles between the workpiece pressure plate 36 and the backing material 48 to be removed from the second flow passage 64 through the first flow passage 52 by creating a vacuum within the first fluid chamber 50, thereby further improving adhesion between them. For example, in FIG. 8, the second flow passage 64 may be a groove 64a passing through the underside of the lower plate 40, or a hole 64b passing from the underside of the lower plate 40 to the interior of the lower plate 40. However, unlike the first flow passage 62, the second flow passage 64 does not connect the first fluid chamber 50 and the second fluid chamber 56. The size, shape, number, and other aspects of the second flow passages 64 are not limited. Of course, both the first flow path 62 and the second flow path 64 may be provided.

As another example, as shown in FIG. 9, instead of the first communication flow path 62 and the second communication flow path 64, the workpiece pressure plate 36 (lower plate 40) may be provided with a communication flow path 66 (third communication flow path 66) that connects the first fluid chamber 50 to a fifth flow path 68 in which a fifth pressure adjustment mechanism 70 is provided (however, FIG. 9 shows another example of the polishing head 12 shown in FIG. 2). In this case, by using the fifth pressure adjustment mechanism 70 to evacuate the third communication flow path 66 via the fifth flow path 68, air bubbles between the workpiece pressure plate 36 and the backing material 48 can be removed from the third communication flow path 66 through the fifth flow path 68, further improving adhesion between them.

In this example, the fifth pressure adjustment mechanism 70 is configured to be able to evacuate fluid from at least the third flow path 66 via the fifth flow path 68 to create a vacuum. However, it may also be configured to supply fluid to the third flow path 66 to pressurize it. In that case, it is also possible to open it to the atmosphere. For example, the fifth flow path 68, which consists of a supply path and a discharge path, may have the supply path and the discharge path formed as the same conduit, or they may be formed as separate conduits. In other words, the number and other configuration of the conduits forming the fifth flow path 68 are not limited. The fifth pressure adjustment mechanism 70 is exemplified by a fluid compressor or a solenoid valve, and is driven and controlled by the control unit 72. Multiple fifth pressure adjustment mechanisms 70 may be provided. Furthermore, the fluid is not limited; for example, the fluid may be water, oil, etc.; however, if the same fluid as the fluid flowing through the first flow path 52 is selected and applied to this embodiment, it is air.

In this example, since the third flow path 66 does not communicate with the first flow path 52, the first pressure adjustment mechanism 54 creates a vacuum or opens the first fluid chamber 50 to the atmosphere, bringing the workpiece pressure plate 36 (lower plate 40) and the backing material 48 into tight contact. The fifth pressure adjustment mechanism 70 then further brings them into tight contact, virtually eliminating the area of the first fluid chamber 50 corresponding to the lower plate 40 and virtually separating that area from the gap region 51. Similarly, even when the first flow path 62 is configured not to communicate with the first flow path 52, the second pressure adjustment mechanism 60 further brings the workpiece pressure plate 36 (lower plate 40) and the backing material 48 into tight contact, virtually eliminating the area of the first fluid chamber 50 corresponding to the lower plate 40 and virtually separating that area from the gap region 51. This allows the first pressure adjustment mechanism 54 to adjust the pressure in the gap region 51 independently of the first fluid chamber 50. Therefore, from the above state, the first pressure adjustment mechanism 54 can further pressurize, evacuate, or open the gap region 51 to the atmosphere through the first flow path 52, thereby adjusting the pressing force applied to the region corresponding to the gap region 51, primarily from the edge (outer periphery) of the workpiece W to the periphery of the workpiece W. The region corresponding to the gap region 51 can be arbitrarily set by adjusting the radial width (diameter) of the lower plate 40, the gap width of the gap region 51, and/or the radial width of the retainer pressure portion 22 (widened portion 22c). For example, the region corresponding to the gap region 51 can include a region closer to the center of the workpiece W, or conversely, it can expand from the periphery of the workpiece W to the surrounding region. In this way, by utilizing the configuration related to the third flow path 66 or the first flow path 62 that does not communicate with the first flow path 52, the pressing force applied to the region corresponding to the gap region 51, such as the edge of the workpiece W to the periphery of the workpiece W, can be adjusted to have a desired effect on the polished shape of the workpiece W.

In addition, by adjusting the thickness of the upper plate 38 and/or lower plate 40, forming them using a material with a certain degree of flexibility, or forming the upper plate 38 and/or lower plate 40 (particularly their undersides) into a special shape such as a concave or convex lens, it becomes possible to change the shape of the upper plate 38 and/or lower plate 40 by warping them upward and/or downward by adjusting the pressure in the third fluid chamber 42 and the second fluid chamber 56. Details will be described later.

Next, the drive unit (not shown) of the polishing head 12 will be described. As mentioned above, the drive unit consists of a vertical movement drive mechanism (not shown) and a rotation drive mechanism (not shown) that are driven and controlled by the control unit 72, and moves the polishing head 12 up and down and rotates by moving the head shaft 18 up and down and rotating it. Both the vertical movement drive mechanism and the rotation drive mechanism of the drive unit can be constructed using known mechanisms.

Specifically, the drive sources for these vertical movement drive mechanisms and rotation drive mechanisms can be motors such as servo motors, and the linear motion device and rotation device can be spline mechanisms such as ball screw spline mechanisms or rotary ball spline mechanisms. Alternatively, a linear motor, which combines the drive source and linear motion device, can be used, or a linear motor actuator, which also combines the guide mechanism for the linear motion device, can be used. In this case, a spindle can be used as the rotation device, or a linear motor actuator with a built-in rotation device can be used (neither is shown).

In addition, a current detector that detects the load on the motor, an encoder that detects the rotation speed and rotation angle, and a length measuring sensor that detects the vertical distance between the head base portion 20, retainer pressure portion 22, retainer 24, etc. and the vertical distance between these and the polishing pad 16 are appropriately provided to determine the height position of the polishing head 12. By adjusting the height position of the polishing head 12 according to these detected values, high-precision control is possible (all not shown).

(polishing equipment)
Next, as shown in Figure 3, the polishing apparatus 10 of this embodiment is a one-sided polishing apparatus that presses the workpiece W held on the underside of the polishing head 12 of this embodiment, which is provided above the base plate 14, against a polishing pad 16 attached to the upper surface of the base plate 14, and rotates the base plate 14 and the polishing head 12 to slide relative to each other, thereby polishing the underside Wa of the workpiece W.

The surface plate 14 is formed in a disk shape in a plan view, with a polishing pad 16 affixed to its upper surface (see Figure 3). The surface plate 14 is provided with a rotation drive mechanism (not shown) and is configured to be rotatable about an axis in a horizontal plane. It also has a slurry supply unit (not shown) that supplies polishing slurry onto the polishing pad 16. Therefore, when polishing the workpiece W, slurry is supplied to the workpiece W, and the polishing head 12 and surface plate 14 are rotated relative to each other, causing the workpiece W and the polishing pad 16 to slide relative to each other, thereby polishing the underside Wa of the workpiece W. The polishing pad 16 may be formed, for example, from a polyurethane sheet, a nonwoven fabric sheet impregnated with polyurethane, or the like, but is not limited to these.

(polishing method)
Next, the polishing method according to this embodiment will be described using an example in which the polishing head 12 according to this embodiment (the polishing head 12 shown in FIGS. 2 and 3) is used.

First, during surface-reference polishing, as shown in FIG. 2, the control unit 72 creates a vacuum within the third fluid chamber 42, lifting the workpiece pressure plate 36 upward and forming a first fluid chamber 50 between the workpiece pressure plate 36 and the backing material 48. This first fluid chamber 50 acts as an enclosed space for pressurizing the workpiece W, and the control unit 72 then pressurizes the first fluid chamber 50. This allows the workpiece W to be pressed from above and polishing pressure to be applied to the workpiece W, with the lower surface of the workpiece pressure plate 36 separated from the press surface 48b of the backing material 48 and the upper surface of the workpiece W in contact with the suction surface 48a of the backing material 48. As a result, the back surface Wb of the workpiece W is fixed to the soft backing material 48, allowing surface-reference polishing to be performed. The control unit 72 then pressurizes the fourth fluid chamber 28, lowering the retainer 24 and causing the retainer 24 to press against the polishing pad 16 around the workpiece W. This provides a guide ring effect that prevents the workpiece W from sliding sideways (protruding radially), and a retainer effect that compensates for deflection of the polishing pad 16 to prevent over-polishing of the edge, or changes the tension of the backing material 48 to have a desired effect on the polished shape of the workpiece W. In this embodiment, the workpiece W is fixed via the backing material 48, so the guide ring effect is essential regardless of the type of polishing method.

Furthermore, as shown in FIG. 2, in a configuration in which the first fluid chamber 50 and the second fluid chamber 56 are connected to each other, the control unit 72 pressurizes the second fluid chamber 56 to the same pressure as the first fluid chamber 50. On the other hand, in a configuration in which the first fluid chamber 50 and the second fluid chamber 56 are not connected to each other, as shown in FIG. 8, the second fluid chamber 56 is sealed or open to the atmosphere, for example. In this way, deformation of the lower plate 40 is prevented.

Through the above control, during front surface reference polishing according to this embodiment, the control unit 72 raises the workpiece pressure plate 36 and lowers the retainer pressure unit 22, applying forces in relatively opposite directions to both components, thereby creating a characteristic positional relationship as shown in FIG. 11A, in which the lower end surface XIA of the workpiece pressure plate 36 is positioned relatively higher than the lower end surface XIB of the retainer pressure unit 22. The vertical movement drive mechanism for the workpiece pressure plate 36 may, of course, be driven by the head shaft 18 (vertical movement drive mechanism of the drive unit) shown in FIG. 6 (however, FIG. 6 shows an example of the state during back surface reference polishing).

When each fluid chamber 28, 42, 50, 56 is in the above state, the first fluid chamber 50 can be evacuated to allow the workpiece W to be picked up (lifted by suction). To unload (peel) the workpiece W, air can be reintroduced into the first fluid chamber 50. In other words, according to this embodiment, the backing material 48 acts as a suction cup to fix (hold) and pick up the workpiece W, and is not formed to be porous as in conventional configurations. Therefore, suction marks on the workpiece W and the entry of foreign matter into the polishing head 12 can be prevented during pickup and unloading.

Next, during backside reference polishing, as shown in FIG. 3, the control unit 72 pressurizes the third fluid chamber 42 to lower the workpiece pressure plate 36 and bring it into contact with the backing material 48. In this state, the first fluid chamber 50 appears to disappear, but the control unit 72 creates a vacuum or opens the first fluid chamber 50 to the atmosphere to bring the workpiece pressure plate 36 and the backing material 48 into close contact, and then applies a downward force to the workpiece pressure plate 36. Specifically, in the present embodiment shown in FIG. 3, the third fluid chamber 42 is further pressurized to apply a downward force to the workpiece pressure plate 36. In the configuration of the example shown in FIG. 6, the head shaft 18 is driven to lower the workpiece pressure plate 36, bringing the workpiece pressure plate 36 into contact with the backing material 48 as described above, and then the first fluid chamber 50 is evacuated or opened to the atmosphere to bring the workpiece pressure plate 36 and the backing material 48 into close contact. Next, a driving force is applied via the head shaft 18 to further lower the workpiece pressure plate 36, applying a downward force to the workpiece pressure plate 36. This allows the workpiece W to be pressed from above with the lower surface of the workpiece pressure plate 36 in contact with the press surface 48b of the backing material 48 and the upper surface of the workpiece W in contact with the suction surface 48a of the backing material 48, applying polishing pressure to the workpiece W. As a result, the back surface Wb of the workpiece W is essentially fixed to the hard workpiece pressure plate 36, allowing back surface reference polishing to be performed.

In this embodiment, as described above, when the workpiece pressure plate 36 is lowered, the workpiece pressure plate 36 comes into contact with the retainer pressure portion 22, and the workpiece pressure plate 36 also comes into contact with the backing material 48. When performing backside reference polishing in this state, as shown in FIG. 3, the lower end surface IIIB of the retainer 24 is positioned above the lower end surface IIIA of the workpiece W fixed to the backing material 48, creating a predetermined gap between the retainer 24 and the polishing pad 16. Backside reference polishing is performed according to the shape of the hard material created on the upper surface Wb, which is the backside Wb of the workpiece W. Therefore, the requirement for a retainer effect to prevent over-polishing of the edge of the workpiece W due to deflection of the polishing pad 16 is relatively low. However, wear of the retainer 24 due to contact with the polishing pad 16 can be a problem. In contrast, this embodiment avoids contact between the retainer 24 and the polishing pad 16, thereby preventing wear of the retainer 24. Furthermore, the gap between the retainer 24 and the polishing pad 16 can be set to a small gap that is sufficient to prevent wear on the retainer 24, so a guide ring effect is also naturally obtained. On the other hand, if emphasis is placed on the influence of the retainer effect on the polished shape of the workpiece W, a configuration can be used in which polishing is performed while the retainer 24 is in contact (pressed) with the polishing pad 16 without creating a gap between the retainer 24 and the polishing pad 16, thereby polishing to the desired polished shape.

In this embodiment, the control unit 72 maintains the contact state between the workpiece pressure plate 36 and the retainer pressure unit 22 by adjusting the pressure within the fourth fluid chamber 28 to a level sufficient to support the retainer pressure unit 22 (its own weight). Specifically, the workpiece pressure plate 36 contacts the retainer pressure unit 22 from above, applying a predetermined pressure. Therefore, the control unit 72 normally reduces the pressure within the fourth fluid chamber 28 to an appropriate level so as not to interfere with the pressing force of the workpiece pressure plate 36 and maintain the contact state between the workpiece pressure plate 36 and the retainer pressure unit 22. This allows a predetermined gap to be created between the retainer 24 and the polishing pad 16, as described above.

In a configuration in which the lower plate 40 has a first communication flow path 62 and the first fluid chamber 50 and the second fluid chamber 56 are connected to each other, the control unit 72 creates a vacuum within the second fluid chamber 56. This allows air bubbles between the workpiece pressure plate 36 and the backing material 48 to be removed from the first communication flow path 62 through the second fluid chamber 56, further improving adhesion between them. At this time, in a configuration in which the first communication flow path 62 also connects to the first flow path 52, the first fluid chamber 50 is also created a vacuum. In a configuration in which the lower plate 40 has a second communication flow path 64 and the first fluid chamber 50 and the second fluid chamber 56 are not connected to each other, the control unit 72 creates a vacuum within the first fluid chamber 50. This allows air bubbles between the workpiece pressure plate 36 and the backing material 48 to be removed from the second communication flow path 64 through the first flow path 52, further improving adhesion between them. At this time, the second fluid chamber 56 may be either a vacuum or open to the atmosphere. Furthermore, in a configuration in which the lower plate 40 has a third communication passage 66 that connects the first fluid chamber 50 to a fifth passage 68, which includes a fifth pressure adjustment mechanism 70, the control unit 72 causes the fifth pressure adjustment mechanism 70 to evacuate the third communication passage 66. This removes air bubbles between the workpiece pressure plate 36 and the backing material 48 through the third communication passage 66 and the fifth passage 68, further enhancing adhesion between them. At this time, the second fluid chamber 56 may be either vacuum or open to the atmosphere. By eliminating air pockets between the workpiece pressure plate 36 and the backing material 48, the two can be sufficiently and smoothly adhered together. As a result, the back surface Wb of the workpiece W can be more precisely aligned to the shape of the hard workpiece pressure plate 36 (lower plate 40), enabling accurate back surface reference polishing.

In a configuration having a first communication flow path 62 or a third communication flow path 66 that does not communicate with the first flow path 52, the workpiece pressure plate 36 and the backing material 48 are maintained in sufficient close contact, and the first pressure adjustment mechanism 54 pressurizes, evacuates, or opens the gap region 51 to the atmosphere through the first flow path 52, thereby adjusting the pressing force applied to the region from the edge of the workpiece W to the periphery of the workpiece W, which corresponds to the gap region 51, and thereby achieving the desired effect on the polished shape of the workpiece W.

Through the above control, during back surface reference polishing according to this embodiment, the control unit 72 applies forces in directions that lower the workpiece pressure plate 36 and raise the retainer pressure unit 22, thereby applying forces in relatively opposite directions to both components. As a result, as shown in FIG. 11B, the lower end surface XIA of the workpiece pressure plate 36 and the lower end surface XIB of the retainer pressure unit 22 are horizontally aligned, or as shown in FIG. 11C, a characteristic positional relationship is created in which the lower end surface XIA of the workpiece pressure plate 36 is positioned relatively lower than the lower end surface XIB of the retainer pressure unit 22. The up and down movement of the workpiece pressure plate 36 may, of course, be achieved by driving the head shaft 18 shown in FIG. 6 (the up and down movement drive mechanism of the drive unit).

As mentioned above, by adjusting the thickness of the upper plate 38 and/or the lower plate 40, by forming them using a material with a certain degree of flexibility, or by forming the upper plate 38 and/or the lower plate 40 (particularly their undersides) into a special shape such as a concave or convex lens, it is possible to change the shape of the upper plate 38 and/or the lower plate 40 by warping them upward and/or downward by adjusting the pressure in the third fluid chamber 42 and the second fluid chamber 56.

As a result, during back-side reference polishing, for example, the second fluid chamber 56 can be evacuated to form the lower plate 40 into the desired shape, and then polishing can be performed by having it follow the back surface Wb of the workpiece W. Alternatively, for example, the third fluid chamber 42 can be evacuated to form the upper plate 38 into the desired shape, and the second fluid chamber can be evacuated to adsorb the lower plate 40 to the deformed upper plate 38, causing the shape of the lower plate 40 to follow the shape of the upper plate 38, and ultimately polishing by having it follow the back surface Wb of the workpiece W. When the third fluid chamber 42 is used to change the shape of the workpiece pressure plate 36 (upper plate 38), the up and down movement of the workpiece pressure plate 36 can be configured to be performed by driving the head shaft 18 (up and down movement drive mechanism of the drive unit) shown in FIG. 6.

In this way, by combining changes to the shape of the central portion of the workpiece W by making changes to the configuration of the upper plate 38 and/or lower plate 40, etc., with changes to the shape of the outer periphery of the workpiece W by utilizing the first flow path 62 or third flow path 66, which do not communicate with the aforementioned first flow path 52, and the gap region 51, it is possible to vary the polishing shape of the workpiece W in an extremely diverse manner, thereby enabling it to be polished accurately to the desired shape.

According to the present invention, both front surface reference polishing and back surface reference polishing can be performed with a single polishing head. This reduces downtime, cuts equipment costs, and simplifies and downsizes the equipment. Furthermore, because the workpiece pressure plate can be separated from the backing material to form a gap, the backing material can be used as a suction cup to secure and pick up the workpiece. This eliminates the need to provide suction holes in the backing material, preventing suction marks on the workpiece and the entry of foreign matter into the polishing head.

10 Polishing apparatus 12 Polishing head 14 Surface plate 16 Polishing pad 18 Head shaft 20 Head base portion 22 Retainer pressure portion 23 Pressing portion 23a Inclined surface 24 Retainer 28 Fourth fluid chamber 30 Fourth flow path 32 Fourth pressure adjustment mechanism 36 Workpiece pressure plate 38 Upper plate 40 Lower plate 42 Third fluid chamber 44 Third flow path 46 Third pressure adjustment mechanism 48 Backing material 48a Adsorption surface 48b Press surface 50 First fluid chamber 51 Gap region 52 First flow path 54 First pressure adjustment mechanism 56 Second fluid chamber 58 Second flow path 60 Second pressure adjustment mechanism 62 First communication flow path 64 Second communication flow path 66 Third communication flow path 68 Fifth flow path 70 Fifth pressure adjustment mechanism 72 Control portion W Workpiece Wa Polishing surface, front surface, bottom surface Wb Non-polishing surface, back surface, top surface

Claims (12)

A polishing head is fixed to a head shaft that can move up and down and rotate, and is provided so as to be movable up and down and rotatable, and holds a workpiece and presses it against a polishing pad while rotating it, thereby polishing the workpiece,
a backing material having an adsorption surface facing the upper surface of the workpiece and a press surface opposite the adsorption surface;
a workpiece pressure plate provided at the center of the press surface so as to be able to come into contact with and separate from the press surface and which is movable up and down;
a first fluid chamber provided between the workpiece pressure plate and the backing material;
a first pressure adjustment mechanism that adjusts the pressure in the first fluid chamber,
The control unit
surface-reference polishing in which the workpiece is pressed from above in a state in which the lower surface of the workpiece pressure plate and the pressing surface of the backing material are separated from each other and the upper surface of the workpiece and the suction surface of the backing material are brought into contact with each other by controlling the pressure inside the first fluid chamber;
a back surface reference polishing in which the workpiece is pressed from above in a state where the lower surface of the workpiece pressure plate is in contact with the pressing surface of the backing material and the upper surface of the workpiece is in contact with the suction surface of the backing material by controlling the application of a downward force to the workpiece pressure plate while evacuating the inside of the first fluid chamber or opening it to the atmosphere ,
a retainer provided on an outer periphery of the suction surface;
a retainer pressure section provided on the outer periphery of the press surface and movable up and down;
The control unit applies forces in the up-down opposite directions to the retainer pressure unit and the workpiece pressure plate,
In the surface reference polishing, polishing is performed in a state where the lower end surface of the workpiece pressure plate is positioned relatively higher than the lower end surface of the retainer pressure portion,
In the back surface reference polishing, polishing is performed in a state where the lower end surface of the workpiece pressure plate and the lower end surface of the retainer pressure part are aligned horizontally, or in a state where the lower end surface of the workpiece pressure plate is positioned relatively lower than the lower end surface of the retainer pressure part.
A polishing head characterized by: a pressing portion that abuts the workpiece pressing plate and the retainer pressing portion to fix them relatively,
2. The polishing head according to claim 1, further comprising a pressing portion that functions as a stopper that restricts movement of the work pressure plate and the retainer pressure portion in a predetermined direction to create a relative positional relationship when polishing the workpiece . The polishing head of claim 2, characterized in that, during the back surface reference polishing, when the workpiece is pressed against the polishing pad with the workpiece pressure plate and the retainer pressure portion in contact via the pressing portion , a gap is formed between the retainer and the polishing pad. The workpiece pressure plate is composed of two layers, an upper plate and a lower plate,
a second fluid chamber between the upper plate and the lower plate;
a second pressure adjustment mechanism that adjusts the pressure in the second fluid chamber,
2. The polishing head according to claim 1 , wherein the lower plate has a communication passage that connects the first fluid chamber and the second fluid chamber. 5. The polishing head according to claim 4 , wherein the flow passage is formed by forming the lower plate from a porous material. 2. The polishing head according to claim 1 , wherein the workpiece pressure plate has a communication passage that connects the first fluid chamber with a first passage in which the first pressure adjustment mechanism is provided. 7. A polishing head according to claim 6 , wherein the flow passage is a groove formed in the lower surface of the workpiece pressure plate. the workpiece pressing plate has a communication passage that communicates the first fluid chamber with a fifth passage in which a fifth pressure adjustment mechanism is provided,
2. The polishing head according to claim 1 , wherein the fifth pressure adjustment mechanism is configured to be able to evacuate at least the communication passage via the fifth passage. a head base portion fixed to the head shaft,
The workpiece pressure plate is fixed to the head base portion and moves up and down by driving the head shaft,
The control unit applies a driving force to lower the workpiece pressure plate via the head shaft during the back surface reference polishing, thereby performing control to apply a downward force to the workpiece pressure plate; or
the work pressure plate is suspended from or slidably attached to the head base portion, and the pressure in a third fluid chamber provided between the head base portion and the work pressure plate is adjusted by a third pressure adjustment mechanism, thereby moving up and down,
2. The polishing head according to claim 1 , wherein the control unit controls the application of a downward force to the workpiece pressure plate by pressurizing the third fluid chamber during the back surface reference polishing. A polishing apparatus comprising the polishing head according to claim 1 . a backing material having an adsorption surface facing the upper surface of the workpiece and a press surface opposite to the adsorption surface;
a workpiece pressure plate provided at the center of the press surface so as to be movable toward and away from the press surface and movable up and down; and a polishing method for polishing the workpiece by pressing the workpiece against a polishing pad, the method comprising:
a surface reference polishing step in which the workpiece is pressed from above in a state in which the lower surface of the workpiece pressure plate is separated from the pressing surface of the backing material by raising the workpiece pressure plate to form an enclosed space between the workpiece pressure plate and the backing material and pressurizing the enclosed space, and in which the upper surface of the workpiece is brought into contact with the suction surface of the backing material;
a back surface reference polishing in which the workpiece is pressed from above while the lower surface of the workpiece pressure plate is in contact with the press surface of the backing material and the upper surface of the workpiece is in contact with the suction surface of the backing material by applying a downward force to the workpiece pressure plate while evacuating the sealed space or opening it to the atmosphere. a retainer provided on an outer periphery of the suction surface;
By using the polishing head further comprising a retainer pressure unit provided on the outer periphery of the press surface and movable up and down,
In the surface-reference polishing, the retainer pressure unit is lowered to press the polishing pad around the workpiece with the retainer,
12. The polishing method according to claim 11 , wherein a gap is formed between the lower end surface of the retainer and the polishing pad during the back surface reference polishing.