Polishing apparatus and polishing method

Abstract

To provide a polishing apparatus and a polishing method capable of improving a polishing effect by preventing sedimentation of abrasive grains in slurry and separation of abrasive grains and a solvent during polishing, and further capable of controlling the behavior of the slurry so as to allow the slurry to be distributed at an arbitrary position.SOLUTION: A polishing apparatus 10 is configured such that an upper press platen (polishing head 12) and a lower press platen 16 are disposed to face each other, a workpiece W is sandwiched between a lower surface of the upper press platen (polishing head 12) and an upper surface of the lower press platen 16, and at least one of the upper press platen (polishing head 12) and the lower press platen 16 rotates to polish the workpiece W. The polishing apparatus 10 includes a slurry supply part 22 that supplies a slurry S to the upper surface of the lower press platen 16, and an electrode 24 that is composed of an upper electrode 24a and a lower electrode 24b that face each other with the upper surface of the lower press platen 16 interposed therebetween and generates an electric field in at least a partial region of the upper surface of the lower press platen 16 by being applied with a voltage. The voltage is set to the voltage whose frequency varies.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polishing apparatus and a polishing method. [Background technology]

[0002] There are known polishing machines in which a workpiece is sandwiched between upper and lower surface plates, and at least one of the surface plates rotates and slides to polish one or both sides of the workpiece. In one example of a single-side polishing machine for polishing the lower surface of a workpiece, the upper upper surface plate is a so-called polishing head that can move up and down, and the polishing head holding the workpiece descends toward the lower lower surface plate to press the workpiece, and the polishing head and the lower surface plate each rotate, thereby polishing the workpiece. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6145596 Summary of the Invention [Problem to be solved by the invention]

[0004] In a polishing apparatus, during polishing, a slurry, which is a polishing liquid containing dispersed abrasive grains, is supplied to the polishing area (the final destination area is the polishing surface of the workpiece, but directly, it is basically the upper surface of the lower platen, regardless of whether a carrier is present to hold the workpiece). However, the supplied slurry simply flows due to the centrifugal force caused by the rotation of the upper and / or lower platen, and as polishing progresses, the abrasive grains in the slurry tend to settle, and the abrasive grains and the solvent tend to separate. For this reason, grooves are usually provided on the upper surface of the lower platen to capture and discharge excess slurry that is unevenly distributed in certain areas along with the polishing debris, but this does not provide a fundamental solution.

[0005] On the other hand, Patent Document 1 (Patent Publication No. 6145596) addresses the issue of slurry scattering (dispersion) outside the polishing area (referred to in the document as the workpiece or substrate) due to centrifugal force caused by rotation, and describes a method in which a slurry in which dielectric abrasive grains are dispersed in water is supplied to the polishing area, and electrodes are incorporated into the main body of the upper surface plate (referred to in the document as the pressure head member) and the lower surface plate (referred to as the surface plate) and a constant frequency voltage to which the water in the slurry is sensitive is applied and acted upon, thereby sucking the slurry mainly through the water and collecting it in the center (centre) of the polishing area (referred to as the workpiece or substrate). [Means for solving the problem]

[0006] In response to this, a technology is desired that does not simply concentrate the slurry in the center, but rather can flexibly control the behavior of the slurry, thereby distributing the slurry to any position, for example, on the upper surface of the lower platen to which the slurry is supplied, or on the polishing surface of the workpiece to be processed.

[0007] Furthermore, the settling of abrasive grains in the slurry and the separation of the abrasive grains from the solvent during polishing can lead to instability in the polishing performance due to uneven distribution of the abrasive grains, excessive loss of abrasive grains through the discharge grooves provided in the lower platen, and a decrease in polishing performance due to the resulting change in abrasive grain concentration, which could ultimately cause a decrease in the polishing effect (polishing rate).

[0008] The present invention has been made in consideration of the above circumstances, and aims to provide a polishing apparatus and a polishing method that can improve the polishing effect by preventing the settling of abrasive grains in the slurry and the separation of the abrasive grains from the solvent during polishing, and that can also control the behavior of the slurry to distribute it at any position.

[0009] The present invention solves the above problems by the solution means described below as one embodiment.

[0010] The polishing apparatus of the present invention is a polishing apparatus having an upper platen and a lower platen arranged opposite each other, a workpiece sandwiched between the lower surface of the upper platen and the upper surface of the lower platen, and at least one of the upper platen and the lower platen rotating to polish the workpiece, characterized in that it has a slurry supply section that supplies slurry to the upper surface of the lower platen, and is composed of an upper electrode and a lower electrode that face each other across the upper surface of the lower platen, and is provided with electrodes that generate an electric field in at least a partial region of the upper surface of the lower platen when a voltage is applied, and the voltage is set to a voltage whose frequency changes.

[0011] The present invention is based on the newly discovered finding that applying a variable-frequency voltage to a slurry can achieve a slurry agitation effect. By applying this finding to a polishing apparatus, the present invention agitates the supplied slurry (abrasive grains and / or dispersion medium), preventing abrasive grain settling and separation of the abrasive grains from the solvent. The variable-frequency voltage not only prevents the slurry from scattering due to centrifugal force, but also prevents uneven distribution of abrasive grains and suppresses the loss of abrasive grains through the discharge groove. Furthermore, the agitation effect of the variable-frequency voltage extends to the slurry in the discharge groove, agitating and dispersing the abrasive grains for reuse in polishing. This improves the polishing effect (removal rate) and enables flexible control of the slurry behavior. Therefore, by combining the slurry attraction effect of generating an electric field in the slurry supply area and the slurry agitation effect of the variable-frequency voltage, it is possible to control the behavior of the slurry S and distribute it in the desired location by arbitrarily arranging electrodes on either side of the slurry supply area.

[0012] The voltage may have a frequency that varies regularly or irregularly within a predetermined range, or may have a frequency that varies continuously or discontinuously within a predetermined range.

[0013] Furthermore, it is preferable that the upper electrode be separated from the main body of the upper platen, be arranged so as to cover at least a portion of the upper surface of the lower platen, and not overlap the main body of the upper platen in the vertical direction of the upper surface of the lower platen. In a configuration in which the upper electrode is separated from the main body of the upper platen and is arranged so as to cover at least a portion of the upper surface of the lower platen, the arrangement and configuration of the electrode (upper electrode) can be more freely set. This makes it easier to adjust the electric field region, enabling more flexible control of the behavior of the slurry. Furthermore, since the main body of the upper platen does not incorporate an electrode, high strength and flatness can be ensured without material limitations. Furthermore, in a configuration in which the upper electrode is arranged so as not to overlap the main body of the upper platen in the vertical direction of the upper surface of the lower platen, the main body of the upper platen is outside the electric field generation region, thereby reliably preventing the upper platen from being affected by the electric field. Meanwhile, the electrode (upper electrode) separated from the main body of the upper platen does not necessarily need to be configured as a rotating body. This simplifies the configuration, and by using bolt fastening instead of slip rings, the conductive wires can be connected more safely and reliably, while also preventing contamination from abrasion powder that can be generated by rotational friction.

[0014] In one embodiment, one or more of the upper electrodes or the lower electrodes can be provided along an arc centered on or near the center of rotation of the lower platen. Furthermore, multiple upper electrodes or multiple lower electrodes can be provided along concentric arcs of different diameters centered on or near the center of rotation of the lower platen. Furthermore, multiple upper electrodes or multiple lower electrodes can be provided in an annular sector shape. In yet another embodiment, one or more of the upper electrodes or multiple lower electrodes can be provided along an arc centered on or near the center of rotation of the upper platen. Furthermore, multiple upper electrodes or multiple lower electrodes can be provided along concentric arcs of different diameters centered on or near the center of rotation of the upper platen. Furthermore, multiple upper electrodes or multiple lower electrodes can be provided in an annular shape. By setting at least one of the electrodes in a desired arrangement and configuration in this way, it is possible to, for example, uniformly distribute the slurry in the circumferential and / or radial directions, or conversely, distribute it with varying strengths and weaknesses.

[0015] The polishing method according to the present invention is a polishing method for polishing a workpiece using a slurry, characterized in that a voltage of varying frequency is applied to the slurry, which is a dispersion medium having dielectric abrasive grains dispersed therein, to suck in the slurry, thereby controlling the behavior of the slurry, or to agitate the slurry.

[0016] By controlling the behavior of the slurry, the slurry can be distributed at any position. The voltage can be in a form in which the frequency changes regularly or irregularly within a predetermined range. The voltage can be in a form in which the frequency changes continuously or discontinuously within a predetermined range.

[0017] Furthermore, it is possible to estimate a frequency range including an appropriate frequency for a purpose depending on the polishing state of the workpiece, and narrow the frequency variable range to a narrower range including that frequency range. [Effects of the Invention]

[0018] According to the present invention, the slurry (abrasive grains and / or dispersion medium) is stirred using a variable frequency voltage, preventing the abrasive grains from settling in the slurry and the separation of the abrasive grains from the solvent during polishing, thereby improving the polishing effect, and also controlling the behavior of the slurry to distribute it at any position. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic view (front view) showing an example of a polishing apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic view (front view) showing another example of a polishing apparatus according to an embodiment of the present invention. [Figure 3] FIG. 3 is a schematic view (front view) showing another example of a polishing apparatus according to an embodiment of the present invention. [Figure 4] 4A, 4B, and 4C are schematic views (plan views) showing examples of polishing apparatuses according to embodiments of the present invention. [Figure 5] 5A, 5B, and 5C are schematic views (plan views) showing other examples of the polishing apparatus according to an embodiment of the present invention. [Figure 6] 6A and 6B are schematic views (plan views) showing another example of a polishing apparatus according to an embodiment of the present invention. [Figure 7] 7A and 7B are schematic diagrams (plan views) showing another example of a polishing apparatus according to an embodiment of the present invention, and Fig. 7C is an enlarged view of a portion of Fig. 7B. [Figure 8] 8A, 8B, 8C, 8D, 8E, and 8F are diagrams showing examples of changes in the frequency of the voltage applied to the electrodes in the polishing apparatus according to an embodiment of the present invention. [Figure 9] FIG. 9 is a photograph of the polishing device used in the examples. [Figure 10] FIG. 10 is a graph showing the measured waveform of the applied voltage according to the first embodiment. [Figure 11] FIG. 11 is a photograph showing the behavior and stirring state of the slurries of Example 1, Comparative Example 1, and Reference Example 1. [Figure 12]FIG. 12 is a graph showing the polishing rates of Example 1 and Comparative Example 1. [Figure 13] FIG. 13 is a set of photographs showing the behavior and stirring state of the slurries of Example 2, Comparative Example 2, and Reference Example 2. [Figure 14] FIG. 14 is a graph showing the polishing rates of Example 2 and Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0020] [Polishing equipment] The present invention applies an electric field to a slurry to control the state and behavior of the slurry during polishing with loose abrasive grains. Therefore, while the present invention is applicable to slurries containing dielectric abrasive grains that can be subjected to an electric field, the properties of other abrasive grains and slurries are not limited, and the present invention is applicable to any polishing method using dielectric abrasive grains. Therefore, the polishing apparatus of the present invention includes polishing apparatuses used for rough polishing or lapping, as well as polishing apparatuses used for finish polishing or polishing or chemical mechanical polishing (CMP). The polishing apparatus of the present invention also includes apparatuses for polishing one side (e.g., the top or bottom) of a workpiece, as well as apparatuses for polishing both sides (e.g., the top and bottom) of a workpiece. The workpiece may be a flat object to be polished (a polished object) such as a circular, square, or rectangular plate, and the material is not limited. The workpiece may be monocrystalline, polycrystalline, or amorphous, including conductors, semiconductors, and insulators. Examples of the workpiece include wafers of silicon compounds, gallium compounds, sapphire, and the like sliced ​​from an ingot.

[0021] Hereinafter, a detailed description of an embodiment of the present invention will be given with reference to the drawings, taking as an example a single-sided polishing apparatus 10 in which the underside of a workpiece W is polished as a polishing surface Wa. The upper surface plate in the single-sided polishing apparatus 10 is usually referred to as a "polishing head," and so hereinafter, the upper surface plate will be referred to as a "polishing head 12." Meanwhile, the lower surface plate in the single-sided polishing apparatus 10 is sometimes simply referred to as a "surface plate," but for ease of understanding, hereinafter, the lower surface plate will continue to be referred to as a "lower surface plate 16." Furthermore, the single-sided polishing apparatus 10 will be simply referred to as a "polishing apparatus 10."

[0022] FIG. 1 is a schematic front view showing an example of a polishing apparatus 10 according to the present embodiment. FIGS. 2 and 3 are schematic front views showing other examples of the polishing apparatus 10 according to the present embodiment. FIGS. 4A, 4B, and 4C are schematic plan views showing other examples of the polishing apparatus 10 according to the present embodiment. FIGS. 5A, 5B, 5C, 6A, 6B, 7A, 7B, and 7C are schematic plan views showing other examples of the polishing apparatus 10 according to the present embodiment. FIG. 7C is an enlarged view of a portion of FIG. 7B.

[0023] As shown in FIG. 1, the polishing apparatus 10 according to this embodiment is an example of an apparatus for polishing the lower surface, which is one side of a workpiece W. The polishing apparatus 10 includes a polishing head 12 (main body 12a) and a lower surface plate 16, each of which has a disk surface arranged facing each other above and below. The main body 12a refers to the main components of the polishing head 12 (upper surface plate), including the portion that comes into contact with the workpiece W. The polishing head 12 has a shaft 14 at its center, which is configured to be movable up and down by a vertical movement mechanism (not shown) and rotatable along a horizontal plane by a rotation mechanism (not shown). Therefore, the polishing head 12 moves up and down together with the shaft 14 and rotates along a horizontal plane around the shaft 14. The lower surface plate 16 has a shaft 18 at its center, which is configured to be rotatable along a horizontal plane by a rotation mechanism (not shown). Therefore, the lower surface plate 16 rotates along a horizontal plane around the shaft 18.

[0024] A workpiece W is placed between the polishing head 12 (main body 12a) and the lower surface plate 16, and during polishing, the workpiece W is sandwiched between the polishing head 12 and the lower surface plate 16. Specifically, as an example, the polishing head 12 is configured so that the workpiece W can be attached and detached to the underside of the polishing head 12. For example, the polishing head 12 has an elastic sheet (not shown) on its underside, and a pressure-adjustable fluid chamber (not shown) is provided inside the area covered by the sheet, so that the workpiece W is adsorbed and held by negative pressure in the fluid chamber via the sheet. Alternatively, the polishing head 12 has one or more holes (not shown) on its underside, so that the workpiece W is adsorbed and held by suction through the holes. Alternatively, water is supplied between the underside of the polishing head 12 and the workpiece W, so that the polishing head 12 adsorbs and holds the workpiece W by the surface tension of the water. In this way, during polishing, the polishing head 12, holding the workpiece W on its lower surface, descends from above and presses the workpiece W against the upper surface of the lower surface plate 16, thereby clamping the workpiece W between the polishing head 12 and the lower surface plate 16.

[0025] A polishing pad 20, which is a polishing tool, is provided on the upper surface of the lower surface plate 16, and the polishing surface Wa of the workpiece W comes into contact with the polishing pad 20 during polishing. A slurry supply unit 22 is also provided, and a slurry S is supplied to the upper surface of the lower surface plate 16 (on the polishing pad 20) during polishing. The slurry supply unit 22 may be configured integrally with the polishing head 12 or the lower surface plate 16 (not shown), or may be configured separately from the polishing head 12 and the lower surface plate 16 as shown in FIG. 1. Depending on the combination of the polishing pad 20 (e.g., hardness) and the slurry S (e.g., type and particle size of abrasive grains), polishing can be performed in a form suitable for the purpose, such as lapping or polishing.

[0026] Slurry S is a polishing liquid containing dielectric abrasive grains, such as aluminum oxide (alumina), silicon dioxide (silica), cerium oxide (ceria), diamond, titanium oxide (titania), zirconium oxide (zirconia), silicon carbide (silicon carbide), boron carbide (B4C), cubic boron nitride (CBN), and other materials, along with a corresponding dielectric dispersant, such as water or an insulating dispersant, such as silicone oil, and other optional additives. The electric field, described below, primarily acts on the abrasive grains, but may also affect the dispersant, depending on the material.

[0027] During polishing, at least one of the polishing head 12 and the lower platen 16, which hold the workpiece W, rotates to polish the workpiece W. As an example, the polishing head 12 and the lower platen 16 are each driven to rotate, thereby polishing the workpiece W. The present invention is applicable to both an apparatus for polishing one side of a workpiece W and an apparatus for polishing both sides, in which multiple upper platens and / or lower platens are provided and used for polishing simultaneously, and also to an apparatus in which multiple workpieces W are polished simultaneously. For example, an apparatus is now widely used in which multiple upper platens (e.g., two, three, four, etc.) with relatively small lower surfaces are provided in addition to one lower platen with a relatively large upper surface, and the same number of workpieces W can be polished simultaneously. An example of the application of the present invention to this type of polishing apparatus 10 will be described later with reference to FIGS. 6A and 6B.

[0028] The polishing apparatus 10 also includes an electrode 24 consisting of an upper electrode 24a and a lower electrode 24b that face each other across the upper surface of the lower platen 16. (Note that while the plan views of FIGS. 4A-7C show multiple upper electrodes 24a1 and 24a2, the front views of FIGS. 1-3 show only the upper electrode 24a for ease of identification.) The electrode 24 is connected to a power supply 26 via a conductive wire 28. When a voltage is applied from the power supply 26 to the electrode 24, an electric field is generated in at least a portion of the upper surface of the lower platen 16, in the region between the upper electrode 24a and the lower electrode 24b. During polishing, a slurry S is supplied to the upper surface of the lower platen 16, and an electric field is applied to the supplied slurry S. As a result, as described below, a predetermined voltage is applied to the slurry S to agitate the slurry S (abrasive grains and / or dispersion medium), preventing the abrasive grains from settling and the abrasive grains from separating from the solvent, thereby improving the polishing effect. Furthermore, the behavior of the slurry S can be controlled to distribute it at any desired position.

[0029] The electrode 24 is a conductive member made of a conductive material such as metal. In this embodiment, as shown in FIG. 1, the lower electrode 24b is provided as a disc-shaped conductive member on the disc surface of an insulating member 30 made of an insulating material such as resin on the lower surface plate 16. A polishing pad 20 is further provided on the upper surface of the lower electrode 24b, and the upper surface of the polishing pad 20 forms the upper surface of the lower surface plate 16. In this way, the lower electrode 24b is integrated with the lower surface plate 16 and incorporated into the lower surface plate 16, and is covered by the insulating polishing pad 20 and insulating member 30, ensuring safety. Note that a groove with a predetermined concave shape may be formed on the upper surface of the lower surface plate 16 (the upper surface of the polishing pad 20) by machining the upper surface of the polishing pad 20 to have a concave shape, or by having the polishing pad 20 follow the concave shape machined on the upper surface of a member directly below the polishing pad 20 (in this embodiment, the upper surface of the lower electrode 24b) (not shown). During polishing, these grooves function as discharge grooves that capture and discharge polishing debris and excess slurry S unevenly distributed in certain areas.

[0030] In this embodiment, as shown in FIG. 1, the upper electrode 24a is disposed separately from the main body 12a of the polishing head 12 and covers at least a portion of the upper surface of the lower surface plate 16. That is, the upper electrode 24a is disposed facing the upper surface of the lower surface plate 16 over an area corresponding to at least a portion of the upper surface of the lower surface plate 16. The upper electrode 24a is covered with an insulating member 32 made of an insulating material such as resin to ensure safety. Meanwhile, as shown in FIG. 2, in another example, the upper electrode 24a is disposed integrally with the main body 12a of the polishing head 12 and incorporated into the main body 12a. The upper electrode 24a is covered in the main body 12a with an insulating member 34 made of an insulating material such as resin to ensure safety.

[0031] In the present embodiment shown in FIG. 1, the upper electrode 24a is separated from the polishing head 12 (main body 12a), thereby simplifying the structures of both the upper electrode 24a and the polishing head 12 (main body 12a). Furthermore, in this embodiment, the polishing head 12 (main body 12a) can be constructed without any material limitations, thereby maintaining the inherent strength and flatness of the polishing head 12 (main body 12a). Here, as long as the upper electrode 24a does not interfere with the shaft 14, the upper electrode 24a may be disposed on top of the main body 12a, so that the upper electrode 24a and the polishing head 12 (main body 12a) partially overlap each other in the vertical direction (i.e., in a plan view), which is the direction perpendicular to the lower surface of the polishing head 12 or the upper surface of the lower surface plate 16 (not shown). However, as shown in FIG. 1, it is more preferable that the upper electrode 24a not overlap the polishing head 12 (main body 12a) in the vertical direction. This ensures that the polishing head 12 is completely removed from the electric field generation area, thereby preventing the polishing head 12 from being affected by the electric field.

[0032] In this way, by isolating the polishing head 12 (main body 12a) from the electric field, deterioration of some components (such as burning) due to the influence of the electric field is prevented, and the effort required to consider the withstand voltage due to the influence of the electric field is eliminated. Furthermore, the upper electrode 24a, which is separated from the polishing head 12 (main body 12a), has improved flexibility in placement and configuration, making it easier to adjust the electric field region and enabling more flexible control of the behavior of the slurry S. Furthermore, the upper electrode 24a can connect the conductive wire 28 more safely and reliably by using bolts or the like instead of slip rings or the like, and can also prevent contamination by abrasion powder that may be generated by rotational friction.

[0033] 3, in a configuration in which the upper electrode 24a is provided separately from the main body 12a of the polishing head 12, the upper electrode 24a and the main body 12a of the polishing head 12 may be connected via a third member, such as a support member 36. In this case, for example, the main body 12a of the polishing head 12 and the upper electrode 24a may be configured to be revolvable around a shaft 38 of the third member (support member 36) via the third member (support member 36).

[0034] During polishing, the electric field generated by the voltage applied to the electrode 24 acts on the dielectric abrasive grains and / or dispersion medium in the slurry S supplied from the slurry supply unit 22, creating an attraction (pulling-in) effect on these. This prevents the slurry S from scattering due to centrifugal force. Furthermore, in this embodiment, a variable-frequency voltage is applied to the electrode 24. This voltage has a frequency that varies regularly or irregularly and / or continuously or discontinuously within a predetermined range. The voltage value is adjusted depending on the dielectric abrasive grains, but examples described below have shown that a voltage in the range of 0-4 kV (with a minimum offset of 0 kV) works well. The waveform is also not limited and may be a rectangular wave, sine wave, triangular wave, sawtooth wave, pulse wave, or the like. For example, examples described below have shown that a rectangular wave works well.

[0035] The variable-frequency voltage draws in and holds the slurry S (abrasive grains and / or dispersion medium) supplied from the slurry supply unit 22 through a suction action, while also varying the strength of the suction action. This strength and suction action results in the apparent discharge and intake of the slurry S repeated at a predetermined rhythm, resulting in a stirring action of the slurry S. This prevents the abrasive grains from settling and the separation of the abrasive grains from the solvent. In other words, the variable-frequency voltage not only prevents the slurry S from scattering due to centrifugal force, but also uniformly disperses the abrasive grains in the slurry S to prevent uneven distribution and suppress the loss of abrasive grains through the discharge groove. Furthermore, the stirring action of the variable-frequency voltage extends to the slurry S that has entered the discharge groove, stirring and dispersing the abrasive grains, allowing them to be reused for polishing. This improves the polishing effect (removal rate) and enables flexible control of the behavior of the slurry S. Therefore, the suction effect of the slurry S by generating an electric field in the slurry S supply area and the stirring effect of the slurry S by the frequency-variable voltage are coordinated, and by arbitrarily arranging the electrodes 24 on either side of the slurry S supply area, it is possible to control the behavior of the slurry S and distribute it to the desired position.

[0036] Furthermore, prior to the present invention, the inventors confirmed that when an electric field is applied to the slurry S, the polishing effect (removal rate) exhibits a tendency to vary depending on the frequency of the voltage (frequency dependency). It is believed that this frequency dependency is influenced by various factors, such as the configuration and rotation speed of the lower platen 16, the properties of the polishing pad 20, the properties of the slurry S, the configuration of the electrode 24, and the size of the workpiece W. In this regard, in the past, for example, Patent Document 1, while using dielectric abrasive grains, water was used as the dispersion medium, and a constant frequency voltage to which the water is sensitive was applied to control the behavior of the water, thereby concentrating the abrasive grains in the slurry S to the center of the polishing area (workpiece). This demonstrates the difficulty of finding an appropriate frequency for controlling the behavior of the abrasive grains themselves and the difficulty of setting appropriate application conditions (electric field). In contrast, the variable frequency voltage according to this embodiment can cover all the appropriate application conditions (appropriate frequencies) related to the attraction acting on the abrasive grains (and, depending on the dispersion medium, on the dispersion medium as well) within a set frequency (within the variable frequency range), eliminating the time and effort required for searching for the appropriate frequency, which is bothersome and impractical. This, combined with the newly discovered stirring effect of the slurry S, results in an improved polishing effect (polishing rate) compared to when no electric field is applied, and also makes it possible to control the behavior of the slurry S and distribute it at the desired position by arbitrarily arranging the electrodes 24 on either side of the slurry S supply area.

[0037] As described above, the frequency-variable voltage applied in this embodiment may have a form in which the frequency within a predetermined range changes regularly or irregularly (randomly), and / or continuously or discontinuously. For example, the examples shown in FIGS. 8A, 8B, and 8C have a form in which the frequency changes regularly and continuously. The example shown in FIG. 8D has a form in which the frequency changes irregularly and continuously. The example shown in FIG. 8E has a form in which the frequency changes regularly and discontinuously. The example shown in FIG. 8F has a form in which the frequency changes irregularly and discontinuously. The form in which the frequency changes is not limited to the forms shown here, and may have a form in which the frequency changes in a curved line, for example.

[0038] To further explain the illustrated embodiment in more detail, the frequency change can be, for example, as shown in FIG. 8A , a form in which the frequency starts at 0 Hz, gradually increases, reaches a maximum of 60 Hz, and then returns to 0 Hz, whereupon the next moment the frequency reaches 0 Hz, and then gradually increases again to 60 Hz, repeating this process. Alternatively, the frequency change can be, as shown in FIG. 8B , a form in which the frequency starts at a maximum of 60 Hz, gradually decreases, reaches a maximum of 0 Hz, and then returns to 60 Hz, whereupon the frequency gradually decreases again to 0 Hz, repeating this cycle. Alternatively, the frequency change can be, as shown in FIG. 8C , a form in which the frequency starts at 0 Hz, gradually increases, reaches a maximum of 60 Hz, and then gradually decreases from 60 Hz to 0 Hz, repeating this cycle. Alternatively, the frequency change can be, as shown in FIG. 8D , a form in which the frequency increases or decreases randomly and continuously within a range from a minimum of 0 Hz to a maximum of 60 Hz. Alternatively, as shown in FIG. 8E, the frequency can be increased stepwise or hierarchically starting from 0 Hz, reaching a maximum of 60 Hz, and then returning to 0 Hz and increasing stepwise or hierarchically again to 60 Hz. Alternatively, the frequency can be increased or decreased randomly stepwise or hierarchically within a range from a minimum of 0 Hz to a maximum of 60 Hz, as shown in FIG. 8F. According to this variation, for example, if the optimum frequencies for a given purpose are 20 Hz and 50 Hz, these frequencies can be reliably covered to efficiently improve the polishing effect (polishing rate). Furthermore, by roughly estimating a frequency range that includes optimum frequencies that favorably affect the suction effect (behavior control) of the slurry S, the polishing effect of the workpiece W, and other purposes, depending on the polishing state of the workpiece W, and then narrowing the frequency variable range to a narrower range that includes this frequency range, more precise behavior control of the slurry S and further improvement of the polishing effect of the workpiece W can be expected, and the optimum frequency can also be efficiently found.

[0039] Next, regarding the configuration of the electrode 24 related to the behavior control of the slurry S, in this embodiment, as shown in FIG. 4A, multiple upper electrodes 24a (two in FIG. 4A, an outer electrode 24a1 and an inner electrode 24a2) are provided in an annular sector shape (central angle θ = 180°) along concentric arcs (concentric loci) X1 and X2 of different diameters centered on the rotation center position c of the lower base plate 16, i.e., the rotation axis (center position c of the shaft portion 18) of the lower base plate 16. The term "annular sector" as used herein refers to a ring segment shape having a predetermined width. The central angle θ of the "annular sector" is defined as 0°<θ<360°. Therefore, the upper electrodes 24a1 and 24a2 shown in FIG. 4B (0°<θ<180°) and FIG. 4C (180°<θ<360°) are both annular sector shapes. 4B and 4C, a plurality of upper electrodes 24a are provided along concentric arcs (concentric loci) X1 and X2 of different diameters centered on the rotation center position c of the lower surface plate 16, i.e., the rotation axis (center position c of the shaft portion 18) of the lower surface plate 16. The number of upper electrodes 24a-n is not limited (i.e., n is an unspecified natural number (n=1, 2, ...)). Note that in this embodiment, even if a plurality of upper electrodes 24a-1 and 24a-2 are provided as shown in FIG. 4A, the upper electrodes 24a-1 and 24a-2 are collectively covered with an insulating member 32, and the upper electrode 24a is configured as a single unit. Alternatively, the upper electrodes 24a-1 and 24a-2 may be independently covered with an insulating member 32, and the upper electrode 24a may be configured as separate units (not shown).

[0040] In this embodiment, by providing the upper electrode 24a, which is one of the electrodes 24, in an annular sector shape and / or by providing the upper electrode 24a along an arc (circular locus) (X1, X2, ...) centered on the position c of the rotation center of the lower surface plate 16, together with the slurry S agitation effect, it is possible to distribute the slurry S uniformly in the circumferential direction of the upper surface of the lower surface plate 16, which is the slurry S supply area, without uneven distribution of abrasive grains. Also, when a plurality of the upper electrodes 24a are provided, for example, two electrodes, an outer electrode 24a1 and an inner electrode 24a2, are provided as shown in Figures 4A, 4B, and 4C, by applying a voltage to the outer electrode 24a1 of the upper electrode 24a corresponding to the vicinity of the outer edge of the lower surface plate 16, it is possible to collect and distribute the slurry S uniformly without uneven distribution of abrasive grains mainly near the outer edge of the lower surface plate 16, together with the slurry S agitation effect. On the other hand, when a voltage is applied to the inner electrode 24a2 corresponding to the vicinity of the center of the lower surface plate 16, this, together with the effect of stirring the slurry S, allows the slurry S to be collected and distributed homogeneously without uneven distribution of abrasive grains mainly near the center of the lower surface plate 16. Furthermore, when a voltage is applied to the plurality of upper electrodes 24a1, 24a2, this, together with the effect of stirring the slurry S, allows the slurry S to be distributed homogeneously over the entire lower surface plate 16 without uneven distribution of abrasive grains.

[0041] Furthermore, the upper electrode 24a is not limited to the position c of the rotation center of the lower surface plate 16, and one or more upper electrodes 24a may be provided along an arc (circular locus) centered on a position d near the position c of the rotation center of the lower surface plate 16. This configuration, combined with the slurry S stirring effect, allows for a uniform distribution of the slurry S in the circumferential direction of the upper surface of the lower surface plate 16, which is the slurry S supply area, without uneven distribution of abrasive grains. Note that the "position d near the position c of the rotation center of the lower surface plate 16" can be defined as, for example, the position d within a circular range having a diameter (1.0r, 1.5r, 2.0r, or 2.5r) that is 1.0, 1.5, 2.0, or 2.5 times the maximum diameter r (the maximum length between the position c of the rotation center and the outer periphery) of the shaft portion 18, which is the member that serves as the rotation shaft of the lower surface plate 16 (see FIG. 4A). In addition, the configuration "arranged along" also includes a configuration in which part or all of the upper electrode 24a (24a1, 24a2) does not overlap with the concentric arcs (concentric loci) X1, X2 of different diameters centered on the position c of the rotation center of the lower base plate 16 or a position d nearby, but is arranged in the same or similar form (shape and / or aspect) as the concentric arcs (concentric loci) X1, X2.

[0042] As another example, the upper electrode 24a can be configured in any desired manner, as shown in FIGS. 5A, 5B, and 5C. In the examples shown in FIGS. 5A and 5B, multiple upper electrodes 24a1 and 24a2 are provided along concentric arcs (concentric loci) X1 and X2 of different diameters centered on the rotation center position c of the lower surface plate 16. In the example shown in FIG. 5A, the upper electrodes 24a1 and 24a2 are rectangular. In the example shown in FIG. 5B, the upper electrodes 24a1 and 24a2 are trapezoidal. In this way, the shapes of the upper electrodes 24a1 and 24a2 are simplified to a quadrilateral shape, such as a rectangle, square, or trapezoid, compared to the present embodiment (FIGS. 4A, 4B, and 4C), while still following the arcs (circular loci) X1 and X2 centered on the rotation center position c of the lower surface plate 16 or a position d nearby. This allows for a simpler configuration and enables control of the behavior of the slurry S in accordance with the present embodiment.

[0043] Furthermore, as shown in the example of FIG. 5C, the upper electrodes 24a1 and 24a2 may be provided in an annular (ring-shaped) shape along arcs (circular loci) X1 and X2 centered on the position c of the rotation center of the lower base plate 16 or a position d nearby.

[0044] Furthermore, even when the polishing apparatus 10 includes, for example, multiple polishing heads 12, the upper electrodes 24a can be arranged in the same manner as in FIG. 4A, etc., as shown in FIGS. 6A and 6B. That is, one or more upper electrodes 24a are arranged along an arc centered on the position c of the rotation center of the lower platen 16 or a position d nearby the position c. Specifically, in FIGS. 6A and 6B, multiple upper electrodes 24a (four in total in FIG. 6A where two polishing heads 12 are provided, and eight in total in FIG. 6B where four polishing heads 12 are provided) are arranged along concentric arcs (concentric circular loci) X1 and X2 of different diameters centered on the position c of the rotation center of the lower platen 16, all in an annular fan shape. Note that, for ease of visualization, the power supply 26 connected to the electrodes 24 is omitted in FIGS. 6A and 6B (the same applies to FIGS. 7A, 7B, and 7C, which will be referred to later). Regardless of the number of upper plates (polishing heads 12), lower plates 16, upper electrodes 24a, and lower electrodes 24b provided, the number of power supply units 26 connected to each electrode 24a, 24b is not limited, as long as they are configured to be able to apply voltage between each electrode 24a, 24b as appropriate.

[0045] In the configuration examples described so far, the upper electrode 24a is positioned relative to the lower surface plate 16. Alternatively, the upper electrode 24a may be positioned relative to the polishing head 12, similar to the lower surface plate 16, relative to the polishing head 12, using the polishing head 12 as the upper surface plate. That is, one or more upper electrodes 24a may be provided along an arc centered on the position c' of the rotation center of the polishing head 12 or a position d' in the vicinity thereof. Here, the "position d' in the vicinity of the position c' of the rotation center of the polishing head 12" can be defined, similar to the position d, as a position d' within a circle whose diameter is 1.0, 1.5, 2.0, or 2.5 times (1.0r', 1.5r', 2.0r', or 2.5r') the maximum diameter r' (the maximum length between the position c' of the rotation center and the outer periphery) of the shaft portion 14, which is the member that serves as the rotation axis of the polishing head 12 (see FIG. 7C ). Furthermore, the term "arranged along" also refers to a configuration in which a part or all of the upper electrode 24a (24a1, 24a2) does not overlap with the concentric arcs (concentric loci) X1', X2' of different radii centered on the position c' of the rotation center of the polishing head 12 or a position d' nearby, but is arranged in the same or similar form (shape and / or aspect) as the concentric arcs (concentric loci) X1', X2'. Specifically, in the examples shown in Figures 7A and 7B, the upper electrode 24a is arranged along the concentric arcs (concentric loci) X1', X2' of different radii centered on the position c' of the rotation center of the polishing head 12, forming a two-ring annular fan shape in Figure 7A and a two-ring annular shape (ring-like shape) in Figure 7B.

[0046] Furthermore, in the present embodiment shown in FIG. 1, instead of the upper electrode 24a, the lower electrode 24b may be provided along an arc (circular locus) X1, X2, X1', X2' centered on the positions c, c' of the rotation center of the lower surface plate 16 or the polishing head 12 or on positions d, d' in the vicinity thereof, although this would complicate the configuration of the lower surface plate 16. Also, the lower electrode 24b may be formed in a predetermined shape, such as an annular sector, a square, or a ring, and disposed at a predetermined position within the lower surface plate 16. Furthermore, in the example shown in FIG. 2, although the configuration of the polishing head 12 and / or the lower surface plate 16 would be complicated, the upper electrode 24a and / or the lower electrode 24b may be provided along an arc (circular locus) X1, X2, X1', X2' centered on the positions c, c' of the rotation center of the lower surface plate 16 or the polishing head 12 or on positions d, d' in the vicinity thereof. And / or, it may be formed into a predetermined shape such as a circular sector, a square, an annular shape, etc., and disposed at a predetermined position within the polishing head 12 and / or the lower platen 16 .

[0047] [Polishing method] Next, the polishing method according to this embodiment is a polishing method for polishing a workpiece W using a slurry S. The method is characterized by applying a variable-frequency voltage to the slurry S, which is a dispersion medium containing dispersed dielectric abrasive grains, thereby controlling the behavior of the slurry S or stirring the slurry S by suction. The polishing apparatus 10 according to this embodiment, which has been described above, is capable of being used. Specifically, the polishing apparatus 10 has a polishing head 12 (an upper surface plate) and a lower surface plate 16 arranged opposite each other. The workpiece W is sandwiched between the lower surface of the polishing head 12 and the upper surface of the lower surface plate 16, and at least one of the polishing head 12 and the lower surface plate 16 rotates to polish the workpiece W. Applying a variable-frequency voltage to the electrode 24 stirs the slurry S, thereby improving the polishing effect (removal rate). Furthermore, the variable-frequency voltage can control the behavior of the slurry S supplied to the upper surface of the lower surface plate 16, thereby distributing the slurry S at any desired position. On the other hand, with a fixed frequency, if the frequency is relatively close to the appropriate frequency, the slurry S can be prevented from scattering against the centrifugal force, but even in this case, the dispersion effect of the slurry S is not obtained, and the suction effect actually causes the abrasive grains to become more unevenly distributed, and as a result, the behavior of the slurry S cannot be sufficiently controlled.

[0048] Details of the polishing method according to this embodiment have been described above in connection with the polishing operation of the polishing apparatus 10 according to this embodiment. For example, the variable-frequency voltage may be configured so that the frequency within a predetermined range changes regularly or irregularly (randomly) and / or continuously or discontinuously. Furthermore, by roughly estimating a frequency range that includes an appropriate frequency that favorably functions for the suction effect (behavior control) of the slurry S, the polishing effect of the workpiece W, and other purposes, depending on the polishing state of the workpiece W, and then narrowing the variable frequency range to a narrower range that includes this frequency range, more accurate behavior control of the slurry S and further improvement in the polishing effect of the workpiece W can be expected, and further, efficient search for the appropriate frequency can be made, as has been described above. [Example]

[0049] The test apparatus according to the present embodiment was a tabletop single-sided polishing apparatus (DELTA-101, Fujikoshi Machinery Co., Ltd.) equipped with an electrode 24 similar to that shown in FIGS. 1 and 4A. A photograph of the test apparatus in plan view is shown in FIG. 9. For clarity, the symbols in FIGS. 1 and 4A are used. The lower surface plate 16 was configured by laminating a metal plate as the lower electrode 24b on an insulating member 30 made of ceramic, which is an insulating material, and further laminating a polishing pad 20 on the lower electrode 24b. Two semicircular annular sectors (an outer electrode 24a1 and an inner electrode 24a2) with a central angle θ=180° were arranged on approximately half of the upper surface of the lower surface plate 16. The distance between the upper electrode 24a and the lower electrode 24b was 5 mm.

[0050] In the behavior test of the slurry S, the polishing head 12 was not provided for easy visual observation. The behavior and state of the slurry S were observed with or without applying a voltage to the electrode 24, depending on the example. In the polishing test of the workpiece W, as shown in FIG. 9, the polishing head 12 (main body 12a) with the workpiece W attached to its underside was placed in an area on the upper surface of the lower platen 16 that did not interfere with the upper electrode 24a (however, the workpiece W is not visible in the photograph in FIG. 9). A guide roller was fitted to the polishing head 12 (main body 12a), so that during polishing, the main body 12a rotated in the same direction and at the same speed as the lower platen 16. In the polishing test of the workpiece W, the slurry S was dropped onto the polishing pad 20, and the lower platen 16 was rotated at a predetermined rotational speed with or without applying a voltage to the electrode 24, depending on the example. The workpiece W was a 2-inch silicon wafer. Each test was carried out after removing static electricity from the upper surface area of ​​the lower surface plate 16 using an ionizer. Other test conditions are as follows:

[0051] Polishing pad: Polishing pad (SURFIN, manufactured by Chiyoda Co., Ltd.) Slurry: Alumina-based slurry (SIC-70S, Baikowski Japan) Plate rotation speed (rpm): Slurry behavior test: 30 min -1 Workpiece polishing test: 30-80 min -1 Polishing pressure: 5kPa Slurry flow rate (supply amount): 10 mL / min Electrode: Only the inner electrode of the upper electrode is applied Applied voltage: Examples and Reference Examples: 0-4kV square wave with a minimum offset of 0kV Comparison example: 0 kV (no electric field) frequency: Example: Sweep between 0-60 Hz (variation shown in Figure 8A) Reference example: Fixed at 10Hz Comparison example: 0Hz

[0052] The applied voltage in the above examples and reference examples was a base voltage generated using a function generator (multifunction generator WF1974, manufactured by NF Corporation), which was boosted 500 times using an amplifier (high-voltage amplifier HEOPS-5B6-LC1, manufactured by Matsusada Precision Co., Ltd.) and applied to electrode 24. The waveform (0-1000 min) measured in the examples using a measuring instrument (digital oscilloscope DS-5624A, manufactured by Iwasaki Electric Co., Ltd.) is shown in Figure 10.

[0053] The results of the slurry behavior test are shown in Figure 11. Figure 11 shows photographs of Example 1, Reference Example 1, and Comparative Example 1 taken 10-30 seconds and 90 seconds after the slurry was supplied. In Comparative Example 1, where no electric field was applied, no slurry suction (suction) lines were observed. In Reference Example 1 and Example 1, where an electric field was applied, suction lines were observed, demonstrating the slurry suction effect due to the action of the electric field. Furthermore, one suction line appeared in Reference Example 1, which used a fixed frequency voltage, while two suction lines appeared in Example 1, which used a frequency sweep voltage (frequency variable voltage). This is thought to be due to Example 1 covering the two appropriate frequencies within the frequency variable range, resulting in varying strengths of the slurry suction. Furthermore, this variation in strength is thought to be due to the repeated apparent discharge and intake of the slurry at a predetermined rhythm, resulting in a stirring action of the slurry. As a result, after 90 seconds, in Comparative Example 1 and Reference Example 1, precipitation of abrasive grains and separation of the abrasive grains from the solvent were observed, whereas in Example 1, precipitation of abrasive grains and separation of the abrasive grains from the solvent were prevented, resulting in a uniform distribution of abrasive grains in the slurry. On the other hand, after 90 seconds, in Reference Example 1, a certain degree of slurry suction effect (concentration of abrasive grains directly below and in the vicinity of the inner upper electrode 24a1 to which voltage was applied) was observed, as in Example 1. However, unlike Example 1, the slurry was not stirred, and therefore the suction effect of the slurry caused the uneven distribution of abrasive grains to become more noticeable. In addition to this test, when voltage was applied to both the outer (24a1) and inner (24a2) sides of the upper electrode 24a under the conditions of Example 1, the behavior (pull-in speed) became faster and the stirring effect was further improved.

[0054] The results of the workpiece polishing test are shown in Fig. 12. Fig. 12 shows the relationship between the rotation speed [min -1 1 is a graph showing the relationship between the rotation speed and the processing rate (polishing rate) [μm / min]. Regardless of the presence or absence of an electric field, the polishing rate tended to increase in proportion to the rotation speed in both Example 1 and Comparative Example 1. In Example 1, in which a frequency sweep voltage (frequency variable voltage) was applied, the polishing rate increased at a rotation speed of 50 min -1 , 80 min -1 Both exceed the polishing rate of Comparative Example 1 without an electric field, reaching 80 min -1It improved by 20%.

[0055] Next, the slurry was changed to a colloidal silica-based slurry (COMPOL 80, manufactured by Fuji Incorporated) and the workpiece was changed to a 2-inch sapphire wafer, and a slurry behavior test and a workpiece polishing test were conducted using the same equipment configuration and test conditions as above.

[0056] The results of the slurry behavior test are shown in Figure 13. Figure 13 is a photograph of Example 2, Reference Example 2, and Comparative Example 2 taken 90 seconds after the slurry was supplied. As shown in Figure 13, similar to the alumina-based slurry, in Reference Example 2 and Example 2 in which an electric field was generated, abrasive grains were concentrated directly below and in the vicinity of the inner upper electrode 24a1 to which a voltage was applied, demonstrating a slurry attraction effect, compared to Comparative Example 2 in which no electric field was used.

[0057] Furthermore, colloidal silica (particle size: 72 nm) has a smaller particle size than alumina (particle size: 300 nm) and is therefore more highly dispersible in the slurry. As a result, as shown in FIG. 13, Example 2 showed a more uniform dispersion than the abrasive particles in Comparative Example 2 (no electric field) and Reference Example 2 (fixed frequency voltage), although this was not as clear as in the alumina-based slurry (FIG. 11).

[0058] The results of the workpiece polishing test are shown in Fig. 14. Fig. 14 shows the relationship between the rotation speed [min -1 14 is a graph showing the relationship between the rotation speed and the processing rate (polishing rate) [μm / min]. As shown in FIG. 14, similar to the alumina-based slurry, regardless of the presence or absence of an electric field, the polishing rate tended to increase in proportion to the rotation speed in both Example 2 and Comparative Example 2. In Example 2, in which a frequency sweep voltage (frequency variable voltage) was applied, the polishing rate increased at a rotation speed of 50 min -1 , 80 min -1 Both of these polishing rates exceeded the electroless polishing rate of Comparative Example 2. Therefore, it was clear that the polishing effect was improved even with the colloidal silica-based slurry, and that the stirring effect of the slurry was certainly achieved.

[0059] According to the above-described embodiments, regardless of the type of slurry, the variable frequency voltage not only prevents the slurry from scattering, but also agitates the slurry, preventing the abrasive grains from settling and the separation of the abrasive grains from the solvent. This prevents uneven distribution of the abrasive grains, improves the polishing effect (polishing rate), and enables flexible control of the slurry behavior. In particular, the present invention is particularly effective for alumina-based, diamond-based, and other slurries with low abrasive grain dispersibility, and is particularly suitable for lapping that mainly uses these slurries. [Explanation of symbols]

[0060] 10 Polishing equipment 12 Polishing head 12a Main body 14 Shaft 16 Lower surface plate 18 Shaft 20 polishing pads 22 Slurry supply section 24 electrodes 24a, 24a1, 24a2 Upper electrode 24b Lower electrode 26 Power supply 28 Conductive wire 30, 32, 34 Insulating members 36 Support member 38 Shaft S Slurry double work Wa polished surface

Claims

1. An upper surface plate and a lower surface plate are provided opposite each other, A polishing apparatus in which a workpiece is sandwiched between a lower surface of the upper surface plate and an upper surface of the lower surface plate, and at least one of the upper surface plate and the lower surface plate rotates to polish the workpiece, a slurry supply unit that supplies a slurry to an upper surface of the lower surface plate; an electrode is provided, the electrode being composed of an upper electrode and a lower electrode facing each other across the upper surface of the lower surface plate, and which generates an electric field in at least a partial region of the upper surface of the lower surface plate when a voltage is applied thereto; The voltage is set to a voltage that varies in frequency. A polishing device characterized by:

2. The voltage has a frequency that changes regularly or irregularly within a predetermined range.

2. The polishing apparatus according to claim 1, wherein:

3. The voltage has a frequency that changes continuously or discontinuously within a predetermined range.

2. The polishing apparatus according to claim 1, wherein:

4. The upper electrode is disposed so as to be separated from the main body of the upper surface plate and to cover at least a part of the upper surface of the lower surface plate, and is disposed so as not to overlap the main body of the upper surface plate in the vertical direction of the upper surface of the lower surface plate.

2. The polishing apparatus according to claim 1, wherein:

5. One or more of the upper electrode or the lower electrode are provided in an annular sector shape or an annular shape.

5. The polishing apparatus according to claim 1, wherein:

6. One or more of the upper electrode or the lower electrode are provided along an arc centered at the position of the rotation center of the lower surface plate or a position in the vicinity thereof.

5. The polishing apparatus according to claim 1, wherein:

7. The upper electrode or the lower electrode is provided in plurality along concentric arcs of different diameters centered at the rotation center of the lower surface plate or at a position in the vicinity thereof.

7. The polishing apparatus according to claim 6, wherein:

8. The upper electrode or the lower electrode is provided in a plurality of annular sectors.

8. The polishing apparatus according to claim 7, wherein:

9. One or more of the upper electrode or the lower electrode are provided along an arc centered at the position of the rotation center of the upper surface plate or a position in the vicinity thereof.

5. The polishing apparatus according to claim 1, wherein:

10. The upper electrode or the lower electrode is provided in plurality along concentric arcs of different diameters centered at the rotation center of the upper surface plate or at a position in the vicinity thereof.

10. The polishing apparatus according to claim 9, wherein:

11. The upper electrode or the lower electrode is provided in a plurality of rings.

11. The polishing apparatus according to claim 10,

12. In a polishing method for polishing a workpiece using a slurry, By applying a voltage whose frequency changes to the slurry in which dielectric abrasive grains are dispersed in a dispersion medium, the behavior of the slurry is controlled by sucking the slurry or stirring the slurry. A polishing method characterized by:

13. Distributing the slurry at any desired position by controlling the behavior of the slurry. The polishing method according to claim 12, characterized by:

14. The voltage has a frequency that changes regularly or irregularly within a predetermined range.

14. The polishing method according to claim 12 or 13, wherein:

15. The voltage has a frequency that changes continuously or discontinuously within a predetermined range.

14. The polishing method according to claim 12 or 13, wherein:

16. A frequency range including an appropriate frequency according to the purpose is estimated according to the polishing state of the workpiece, and the frequency variable range is narrowed to a narrower range including the estimated frequency range.

14. The polishing method according to claim 12 or 13, wherein:

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