Plasma-assisted polishing device

Abstract

[Problem] To provide a plasma-assisted polishing device capable of reliably transmitting the rotational force of a rotary shaft to a rotary head by connecting the rotary shaft and a support shaft of the rotary head with electric insulation properties, absorbing the tolerance of each part, and accurately bringing a polishing pad and a workpiece into close contact with each other. [Solution] In a rotary head 14, a head body 88 provided with a mounting part 15 on a lower surface and a support shaft 89 are linked by a link plate 90 so as to be swingable and rotatable with respect to a head body. An end part of the support shaft is coaxially connected to an end part of the rotary shaft 13 by a connection tool 91 having electric insulation property, and at least the support shaft is detachably attached to the connection tool. A washer 92 for slidably receiving the tip of the support shaft is embedded in a surface opposite to a mounting part of the head body, and an engagement shaft 95 is penetrated in an orthogonal state at a tip part of the support shaft. A center hole 97 penetrating through a shaft part 96 of the support shaft is provided in the center of the link plate, and an engagement groove 98 for receiving both end parts of the engagement shaft by providing a clearance is provided on the link plate or the head body, and the link plate is detachably attached to the head body.

Description

Plasma-assisted polishing equipment

[0001] The present invention relates to a plasma-assisted polishing apparatus suitable for precision finishing of difficult-to-process materials.

[0002] In recent years, there has been active development of devices using wide bandgap semiconductors as power semiconductor device materials, which are capable of highly reliable operation even in high temperature environments and have low loss. Wide bandgap semiconductors are classified into the following groups in order of decreasing bandgap: SiC, GaN, and Ga. ２ O ３ , and diamond. These wide bandgap semiconductors have physical properties such as band gap, breakdown field value, thermal conductivity, and electron mobility several to several tens of times larger than those of Si, and therefore when power devices are fabricated using these materials, they offer advantages such as high breakdown voltage, reduced power consumption, and high-speed operation. However, because they are highly hard and chemically inert, they are difficult to process and it is difficult to efficiently achieve the desired flatness and surface roughness by ordinary polishing.

[0003] Currently, wide bandgap semiconductor wafers are finished by chemical mechanical polishing (CMP). However, because polishing is performed using a slurry containing alkaline chemicals and abrasive grains, the surface roughness deteriorates due to "etch pits" formed when surface defects in the material are eroded by the alkaline components, and "scratches" are formed due to the aggregation and coarsening of the abrasive grains, meaning that the material properties are not fully utilized. In addition, the polishing efficiency is low, resulting in low yields and high costs.

[0004] Plasma-assisted polishing (PAP) has been proposed as a method for machining difficult-to-machine materials such as SiC, GaN, or cemented carbide (see Patent Document 1). This PAP method involves applying radicals generated in plasma to the surface of a workpiece to form a surface-modified layer softer than the workpiece material, while the surface-modified layer is removed by dry mechanical polishing using an abrasive material to proceed with machining. The PAP method is an excellent machining method that, based on its machining principle, enables precision machining without introducing scratches or a process-affected layer into the workpiece by using an abrasive material whose Mohs hardness is intermediate between that of the workpiece material and the surface-modified layer. Patent Document 1 shows that, for SiC, OH radicals are more efficient at oxidizing than O radicals as radicals that oxidize the surface of the workpiece and form a surface-modified layer (oxide layer). To achieve this, a carrier gas and H ２ O and H ２ O ２ High frequency power is applied to an atmosphere containing one or both of the above to generate plasma, thereby generating OH radicals.

[0005] Patent Literature 2 discloses a machining method utilizing radical adsorption and transport, in which the surface of a movable tool, having corrosion resistance and adsorption capacity for chemically reactive radicals, is passed through a plasma generation region generated using a reactive gas containing at least a gas containing an element or substituent that generates the radicals and a rare gas, the radicals generated in the plasma generation region are adsorbed onto the tool surface to provide reactive species, the reactive species on the tool surface are transported to a workpiece surface positioned at a location different from the plasma generation region by moving the tool, and reaction products generated by chemical reactions between atoms on the workpiece surface that contact the tool and the reactive species are removed, thereby selectively machining only the portion of the workpiece surface that contacts the tool surface, using the tool surface as a machining reference plane. It also discloses that the radical-generating element is a halogen element such as F or Cl, and the radicals are F radicals or Cl radicals, or that the radical-generating substituent is an OH group and the radicals are OH radicals. This processing method also involves the action of radicals on the surface of the workpiece, and the workpiece and the tool acting as an abrasive move in contact with each other, so it can be called a type of PAP.

[0006] Cited Document 3 discloses a processing method for PAP, in which a polishing tool consisting of a vitrified-bonded grinding wheel in which abrasive grains are bonded with an inorganic glass-based bond material, or a resin-bonded grinding wheel in which abrasive grains are bonded with a thermosetting resin bond material, is used to apply fluorine radicals or oxygen radicals to the surface of a workpiece to fluorinate or oxidize it, thereby forming a surface-modified layer, and fluorine radicals or oxygen radicals are also applied to the polishing tool, etching the bond material of the polishing tool to expose the abrasive grains, while processing the surface of the workpiece. This causes an automatic dressing action that etches the bond material of the polishing tool to expose the abrasive grains, preventing a decrease in polishing rate due to "glazing" or "clogging," enabling precision machining with a high polishing rate maintained without dressing, and enabling the machining of difficult-to-machine materials such as SiC, GaN, and AlN.

[0007] Japanese Patent No. 5614677 Japanese Patent No. 6692010 Japanese Patent Application Publication (JP-A) 2022-133198

[0008] In conventional polishing techniques, a polishing pad is attached to a rotary table and a workpiece is attached to a rotary head for polishing. However, this technique adds a plasma-assisted surface modification to the workpiece, which presents unique challenges. First, the rotary head, located in the plasma, must not significantly disturb the plasma. To accurately bring the polishing pad and workpiece into close contact, the rotation axis of the rotary table and the rotation axis of the rotary head must be precisely aligned. In other words, the mounting parts of the rotary table and the rotary head that hold the polishing pad and workpiece must be parallel. However, if there are tolerances in each part, differences in the contact pressure between the polishing pad and workpiece will inevitably occur.

[0009] In view of the above-mentioned situation, the present invention aims to solve the problems by providing a plasma-assisted polishing apparatus that can connect the rotating shaft and the support shaft of the rotating head with electrical insulation, can absorb the tolerances of each part to accurately bring the polishing pad and workpiece into close contact, can reliably transmit the rotational force of the rotating shaft to the rotating head, and can apply a predetermined contact pressure to the polishing pad and workpiece.

[0010] In order to solve the above-mentioned problems, the present invention provides the following plasma-assisted polishing apparatus.

[0011] [Configuration 1] A plasma-assisted polishing apparatus comprising: a mechanical section that includes an attachment section that detachably holds a workpiece to be polished and a polishing pad facing each other, and that moves the workpiece and the polishing pad relatively while bringing them into contact with each other at a predetermined contact pressure; and a plasma generating section that generates plasma based on a process gas and generates neutral radicals that, when the plasma acts on the surface of the workpiece to be polished, form a surface modified layer that is softer than the workpiece; wherein the mechanical section includes at least: a first rotation unit having a rotary table with a first rotation shaft facing a first direction and a first attachment section that holds the polishing pad or the workpiece; and a second rotation unit that includes a rotary head with a second rotation shaft facing the first direction and a second attachment section that is smaller in area than the rotary table and holds the workpiece or the polishing pad, and a pressing means that displaces in the first direction and applies contact pressure between the workpiece and the polishing pad; and wherein the rotary head includes a head main body that includes the second attachment section on its underside, and a support shaft that is connected to the head main body by a linking plate so that the head can swing and rotate relative to the head main body. an end of the support shaft is coaxially connected to an end of the second rotating shaft by an electrically insulating connector, and at least the support shaft is detachable from the connector.

[0012] [Configuration 2] A plasma-assisted polishing apparatus according to Configuration 1, wherein a washer for slidably receiving the tip of the support shaft is embedded on the surface of the head body opposite the second mounting portion, an engagement shaft is perpendicularly inserted through the tip of the support shaft, the link plate has a central hole in the center that passes through the shaft portion of the support shaft, and the link plate or the head body has engagement grooves that receive both ends of the engagement shaft with clearance, and the link plate is detachably attached to the head body.

[0013] [Configuration 3] The plasma-assisted polishing apparatus according to Configuration 2, wherein the washer has a hemispherical concave spherical portion at its center with a central angle of less than 180°, and the support shaft has a convex spherical portion at its tip with a radius equal to or smaller than that of the concave spherical portion.

[0014] [Configuration 4] The plasma-assisted polishing apparatus according to Configuration 3, wherein at least the washer, out of the washer and the convex spherical portion of the support shaft, is made of an ultra-hard material.

[0015] [Configuration 5] The plasma-assisted polishing apparatus according to Configuration 1, wherein the connecting device is configured by assembling a first fastener and a second fastener, each made of metal, with an insulating block made of an electrically insulating material sandwiched therebetween, the first fastener being attached to an end of the second rotating shaft, and the second fastener being attached to an end of a support shaft of the rotating head.

[0016] [Configuration 6] The plasma-assisted polishing apparatus according to Configuration 5, wherein the first fastener has a connecting hole into which the end of the second rotating shaft is inserted, and the second fastener has a connecting hole into which the end of the support shaft is inserted, and a circular protrusion is provided on one side of the periphery of the connecting hole of the first fastener and the periphery of the connecting hole of the second fastener, which are respectively joined to both radial faces of the insulating block, and an annular recess is provided on the other side into which the circular protrusion is fitted.

[0017] [Configuration 7] A plasma-assisted polishing apparatus according to Configuration 5 or 6, wherein the first fastener and the second fastener are each provided with a plurality of threaded holes for screwing an insulating block, the insulating block is provided with countersunk holes for screwing the first fastener and the second fastener from both radial side surfaces, and further, the first fastener and the second fastener are provided with through holes at positions corresponding to the countersunk holes for inserting screws therethrough, and the first fastener and the second fastener are connected in an electrically insulated state via the insulating block.

[0018] [Configuration 8] The plasma-assisted polishing apparatus according to Configuration 6, wherein a slit is formed facing outward in each connecting hole of the first fastener and the second fastener, and a fastening screw is threaded through the slit at a radius portion sandwiching the slit, thereby tightening and connecting the end of the second rotating shaft or the end of the support shaft inserted into the connecting hole.

[0019] [Configuration 9] The plasma-assisted polishing apparatus according to Configuration 5, wherein the insulating block is made of machinable ceramics having electrical insulation, heat insulation, and rigidity.

[0020] In the plasma-assisted polishing apparatus of the present invention, the head body and the support shaft are connected by a link plate so that they can swivel and rotate, accommodating tolerances of each component and accurately bringing the polishing pad and workpiece into close contact with each other, thereby ensuring uniform contact pressure across the entire surface of the workpiece. Furthermore, the engagement shaft of the support shaft is designed to engage with an engagement groove in the head body or the link plate, thereby reliably transmitting the rotational force of the support shaft to the head body. Furthermore, the connector can connect the second rotating shaft and the rotating head support shaft with electrical insulation and thermal insulation due to the material properties of the insulating block, and can precisely connect the second rotating shaft and the support shaft coaxially. Furthermore, the second rotating shaft and the support shaft are connected to the connector by a slit and a fastening screw, providing a secure connection and preventing chattering even when the workpiece and polishing pad are in contact with each other at high contact pressure.

[0021] FIG. 1 is a longitudinal sectional front view of a plasma-assisted polishing apparatus according to the present technology. FIG. 2 is a longitudinal sectional side view of a plasma-assisted polishing apparatus according to the present technology. FIG. 3 is a cross-sectional view taken along line A-A in FIG. 1. FIG. 4 is a cross-sectional view taken along line B-B in FIG. 1. FIG. 5 is an enlarged partial cross-sectional view of a main portion. FIG. 6 is a partially exploded perspective view showing the relationship between a counter electrode plate and a rotary table. FIG. 7 is a front view of a rotary head, a rotary shaft, and a connector that detachably and insulatedly connects the rotary shaft and the rotary head. FIG. 8 is a longitudinal sectional front view of the rotary head, the rotary shaft, and the connector. FIG. 9 is an exploded perspective view of the rotary head. FIG. 10 shows a tilt mechanism in the rotary head, with (a) being a longitudinal sectional front view of the rotary head and (b) being a longitudinal sectional side view of the rotary head. FIG. 11 is a cross-sectional plan view of a fixing member on the rotary shaft side that constitutes the connector. FIG. 12 is a plan view of an insulating block that constitutes the connector. FIG. 13 is a bottom view of a fixing member on the rotary head side that constitutes the connector. FIG. 14 is an exploded perspective view of a rotary head according to another embodiment. Fig. 15 is an exploded cross-sectional view of a rotary head according to another embodiment. Fig. 16 is a cross-sectional view of an assembled rotary head according to another embodiment. Fig. 17 is an explanatory plan view showing the relationship between a rotary table and a rotary head at the home position. Fig. 18 is an explanatory plan view showing the relationship between a rotary table and a rotary head according to another embodiment, in which three rotary heads are used. Fig. 19 is an enlarged partial cross-sectional view of a main portion of another embodiment of a plasma-assisted polishing apparatus.

[0022] The present invention will be described in more detail below with reference to the embodiments shown in the accompanying drawings. Figures 1 to 6 show a plasma-assisted polishing apparatus according to the present technology, in which reference numerals 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 12

[0023] The object to be processed by the present invention is SiC, GaN, AlN, AlGaN, Ga ２ O ３ The materials are difficult to process, such as single crystal diamond (SCD), polycrystalline diamond (PCD), diamond-like carbon (DLC), sapphire, alumina, and cemented carbide, but are not particularly limited thereto.

[0024] In a plasma-assisted polishing apparatus such as the present technology, it is not easy to oscillate the plasma while generating it stably. In particular, when using a capacitively coupled plasma using parallel plate electrodes, the rotary table is used as one of the electrodes, and the counter electrode plate is placed close to the rotary table. However, if the counter electrode plate is set to have a sufficiently large area relative to the rotary table in consideration of oscillation, the plasma generation area will expand and it will be necessary to increase the input power. Increasing the input power will also increase the temperature of the workpiece, which may cause problems such as thermal deformation and material changes, which is undesirable.

[0025] The plasma-assisted polishing apparatus of the present technology comprises a chamber 1 containing a process gas containing a carrier gas and a reactive gas and accommodating a mechanical unit, a gas supply means 2 that supplies the process gas into the chamber 1, a gas exhaust means 3 that exhausts the process gas from the chamber 1, a mechanical unit 4 that has an attachment part that detachably holds a workpiece W to be polished and a polishing pad P facing each other and moves the workpiece W and the polishing pad P relative to each other while bringing them into contact with each other at a predetermined contact pressure F, and a high-frequency power supply 5 that generates neutral radicals based on the reactive gas by applying high-frequency power between opposing electrode plates while maintaining the process gas at a predetermined pressure.

[0026] More specifically, the plasma-assisted polishing apparatus is composed of a chamber 1 containing a process gas containing a carrier gas and a reactive gas, housing a mechanical unit 4, and having a plasma generating unit 9; a gas supply means 2 for supplying the process gas into the chamber; a gas exhaust means 3 for exhausting the process gas from the chamber; a mechanical unit 4 having an attachment part for detachably holding a workpiece W to be polished and a polishing pad P facing each other, and moving the workpiece W and the polishing pad P relative to each other while bringing them into contact with each other at a predetermined contact pressure; and a plasma generating unit 9 for generating neutral radicals based on the reactive gas by supplying high-frequency power from a high-frequency power supply 5 to an electrode while maintaining the process gas at a predetermined pressure. The mechanical section 4 includes a first rotation unit 6 having a rotary table 11 equipped with a first rotation axis 10 in a first direction and a first mounting portion 12 that detachably holds the polishing pad P or the workpiece W, a second rotation axis 13 in the first direction, a rotary head 14 that has a smaller area than the rotary table 11 and a second mounting portion 15 that detachably holds the workpiece W or the polishing pad P, a second rotation unit 7 that is displaced in the first direction and has a pressing means 16 that applies contact pressure between the workpiece W and the polishing pad P, and a linear drive means 8 that linearly displaces the first rotation unit 6 in a second direction that is perpendicular to the first direction. The plasma generating unit 9 is composed of the rotary table 11, which also serves as one of the electrode plates, and a counter electrode plate 17 facing the rotary table 11, the counter electrode plate 17 being composed of a fixed electrode plate 18 and movable electrode plates 19, 20, which are electrically connected to each other, the fixed electrode plate 18 being attached to a stand 21 in the chamber 1, and the movable electrode plates 19, 20 being attached to the first rotating unit 6 so that their electrode surfaces are flush with the fixed electrode plate 18. The plasma-assisted polishing apparatus of the present technology polishes the workpiece W by a combination of rotation of the workpiece W having first rotation axes 10, 13 in a first direction, rotation of the polishing pad P, and oscillation by the linear driving means 8, while applying neutral radicals generated in the plasma generating unit 9 to the polishing surface of the workpiece W.

[0027] As shown in the figure, an embodiment in which a polishing pad P is attached to the first mounting portion 12 of the rotary table 11 and a workpiece W is attached to the second mounting portion 15 of the rotary head 14 is suitable for polishing a workpiece W, such as a semiconductor wafer, to achieve planarization. In another embodiment, when the workpiece W is held on the first mounting portion 12 of the rotary table 11 and the polishing pad P is held on the second mounting portion 15 of the rotary head 14, a large-area workpiece W surface is polished with a small-area polishing pad P. This allows for localized processing of a curved workpiece W, improving the contact of the polishing pad P with the workpiece W. Furthermore, when the unit cost of the polishing pad P per unit area is high, a small polishing pad P can be used, which is economical. The method for attaching the workpiece W to the first mounting portion 12 or the second mounting portion 15 is not particularly limited. The workpiece W can be attached by direct bonding to the mounting surface, or by bonding to a holding plate, which is then attached to the mounting portion by appropriate means. To remove the workpiece W after polishing, the adhesive is dissolved in a solvent to separate the workpiece W. Another method for attaching the workpiece W is a vacuum chuck method.

[0028] In another embodiment, the second rotation unit 7 can be linearly displaced in the second direction by the linear drive means 8. Here, a rotation and swing means equipped with an arm instead of the linear drive means 8 can be considered, but since the first rotation unit 6 has the rotary table 11 and its drive system, and the second rotation unit 7 has the rotary head 14 and its drive system, the pressing means 16, and the counter electrode plate 17 with a large area, both of them become heavy in weight, and therefore a rotation and swing means using an arm is not preferable.

[0029] This technology includes a surface modification process in which, using the above-mentioned plasma-assisted polishing apparatus, high-frequency power is applied to a process gas containing a carrier gas and a reactive gas to generate plasma, thereby generating neutral radicals based on the reactive gas, and the neutral radicals are caused to act on the surface of the workpiece W to form a surface-modified layer on the surface of the workpiece W that is softer than the workpiece itself; and a polishing process in which the workpiece W and a polishing pad P are moved relative to each other while being brought into contact with each other at a predetermined contact pressure F, thereby removing the surface-modified layer of the workpiece W. When the surface modification process and the polishing process are repeated alternately, or when both processes are carried out simultaneously to polish the workpiece W and the polishing pad P, the workpiece W is polished by a combination of the rotation of the workpiece W and the rotation of the polishing pad P, each of which has an offset axis in a first direction, and the oscillation in a second direction that is perpendicular to the first direction and increases or decreases the distance between the two axes.

[0030] This embodiment will be described in more detail. The chamber 1 does not need to be a large-scale vacuum vessel because the process gas pressure is near atmospheric pressure. The process gas pressure is preferably near atmospheric pressure to sufficiently increase the neutral radical concentration that contributes to the oxidation rate (surface modification rate) of the surface modification process, and a reduced pressure is preferable in consideration of plasma stability. Therefore, in this embodiment, the process gas pressure is set to 100 Pa (0.75 Torr) to 101.325 kPa (760 Torr).

[0031] The process gas is a mixture of a carrier gas for stably maintaining plasma and a reactive gas selected according to the material to be polished. As the carrier gas, an inert gas, particularly a rare gas such as helium (He) or argon (Ar), is used. Here, He has the advantage of being able to easily generate plasma under atmospheric pressure, but it is rare and expensive. Therefore, it is desirable to use relatively inexpensive Ar, but since He has inferior plasma stability compared to He, a stabilizing gas with a smaller ionization potential than the metastable level of Ar is added to ionize it by the Penning effect, generating electrons necessary for generating and maintaining plasma. Examples of the stabilizing gas include alcohol, hydrocarbon gas, and ammonia. As the reactive gas, oxygen gas (O ２ ), hydrogen gas (H ２ ), water vapor (H ２ O), hydrogen peroxide (H ２ O ２ ), fluorine-based gas (CF ４ , C ２ F ６ , C ３ F ８ , S.F. ６ , N.F. ３ ) etc.

[0032] When the workpiece W is a substrate made of single crystal diamond (SCD), polycrystalline diamond (PCD), or diamond-like carbon (DLC), the polishing pad P is a plate having at least a surface made of quartz glass, silicon, borosilicate glass, a resin-bonded grinding wheel, or a vitrified-bonded grinding wheel. For vitrified-bonded grinding wheels, the abrasive grains are preferably diamond grains with a hardness of #1000 (average particle size 16 μm) to #20000 (average particle size 0.8 μm). Silicon is less hard than quartz glass and is expected to improve the surface roughness, especially for single crystal diamond. It is also available as a semiconductor wafer, making it inexpensive. The process gas preferably contains an element that bonds with the carbon atoms constituting the diamond and sublimes, or bonds with the atoms constituting the polishing pad and the carbon atoms constituting the diamond and extracts the surface carbon atoms through relative motion. Specifically, the process gas used is an inert gas containing oxygen, water vapor, or oxygen and water vapor.

[0033] The plasma-assisted polishing apparatus of this embodiment will be described in more detail. As shown in FIGS. 1 to 3 , the first rotating unit 6 has a bearing sleeve 23 fixed to the upper surface of a support plate 22. The bearing sleeve 23 rotatably supports the first rotating shaft 10, which passes through the bearing sleeve 23 and faces a first direction (vertical direction). The first rotating shaft 10 is also rotatably supported by the load of a rotating table 11 located above. The first rotating shaft 10 is connected to the drive shaft of a rotating motor 24 fixed below the support plate 22. The bearing sleeve 23 incorporates a thrust bearing and a radial bearing, or bearings with equivalent functions, to protect the bearing from the corrosive gas used to generate plasma. The rotating motor 24 incorporates a brushless motor and a reducer as an integral unit, and can be controlled to a rotation speed range of 16 to 800 rpm. The rotating table 11 is made of a conductive material and doubles as one electrode plate of a parallel plate structure. A polishing pad P can be detachably held on a first mounting portion 12 provided on the upper surface.

[0034] 1 to 3, the linear drive means 8 includes two parallel linear guides 25, 25 provided on the bottom surface of the chamber 1, two movable bodies 26, 26 sliding on each linear guide 25, and a linear actuator 27 disposed between the two linear guides 25, 25. The linear guides 25, 25 are mounted on support stands 30, 30 raised from a base plate 29 disposed on the upper surface of a bottom plate 28 of the chamber 1, in order to ensure space for the rotary motor 24. The linear actuator 27 is composed of a stepping motor 31 and a ball screw feed mechanism 32. The movable bodies 26, 26, ... are fixed to the four corners of the bottom surface of the support plate 22, and a movable part 33 of the ball screw feed mechanism 32 is fixed to the support plate 22, so that the first rotary unit 6 is linearly driven in the second direction (horizontal direction) by rotation of the stepping motor 31. Here, the ball screw feed mechanism 32 is also elevated by a support table 34 provided on the base plate 29. That is, a stepping motor 31 is held on the support table 34, and the ball screw feed mechanism 32 is rotatably supported by a pair of bearings 35, 35. The rotary table 11 is electrically connected to the chamber 1 via the members of the first rotary unit 6, the linear guide 25, and the moving body 26, and the chamber 1 is grounded. The linear drive means 8 in the present technology rotates the stepping motor 31 forward and backward so as to enable repeated movement with a stroke of ±75 mm, and this repeated movement corresponds to a swing mechanism.

[0035] As shown in FIGS. 1 and 2 , the second rotation unit 7 is constructed within the chamber 1 on the basis of a highly rigid base 21 that extends from the bottom plate 28. The base 21 has a fixed plate 37 at the upper end of a frame 36 formed of angle bars so as to straddle the first rotation unit 6 and the linear drive means 8. A spindle unit 40, whose axis faces the first direction, and a rotary motor 41 that drives the second rotation shaft 13 of the spindle unit 40 are attached to an elevation plate 39 that moves up and down in a first direction (vertical direction) relative to a guide plate 38 that extends up on the upper surface of the fixed plate 37 of the base 21. A metal belt 45 is wound around a pulley 42 fixed to the second rotation shaft 13 of the spindle unit 40 and a pulley 44 fixed to a drive shaft 43 of the rotary motor 41 to transmit power. Note that the metal belt 45 is made of a corrosion-resistant metal material because it is exposed to the process gas. A tensioner is usually provided to apply tension to the metal belt 45, but this is omitted in the drawings. Here, the rotary motor 41 has a structure in which a brushless motor and a reducer are integrated together, similar to the rotary motor 24 of the first rotary unit 6, and the rotation speed can be controlled within a lower range.

[0036] Linear guides 46, 46 facing in a first direction are provided on both sides of the guide plate 38 in parallel, and a pair of movable bodies 47, 47 is movably provided on each linear guide 46, with the four movable bodies 47, ... being fixed to the back surface of the lifting plate 39. The spindle unit 40 and rotary motor 41 are attached to the front surface side of the lifting plate 39. The lower end of an operating shaft 49 that passes through an upper plate 48 of the chamber 1 in an airtight state is connected to the upper end of the lifting plate 39, and is also connected to a piston 51 of an air cylinder 50 outside the chamber 1, and the main body of the air cylinder 50 is fixed to the upper plate 48 and receives a reaction force. More specifically, the operating shaft 49 has its lower end connected to an operating plate 52 provided on the upper part of the spindle unit 40 at a position coaxial with the second rotation shaft 13, its upper end airtightly penetrating a slide bearing 55 in a base plate 54 provided to close an opening 53 provided in the upper plate 48 of the chamber 1 from above, and its upper end connected to a pusher 51 of the air cylinder 50. The body of the air cylinder 50 is fixed to a reaction force receiving plate 56 fixed to the upper surface of the base plate 54. In addition, a vacuum regulator 57 for the air cylinder 50 is provided on the upper surface of the base plate 54 to adjust and monitor the air pressure supplied to the air cylinder 50. The pressing means 16 is mainly composed of the operating shaft 49, air cylinder 50, reaction force receiving plate 56, and vacuum regulator 57.

[0037] The rotary head 14 is detachably connected to the lower end of the second rotary shaft 13 of the second rotary unit 7 in an electrically insulated state. Because the total weight of the moving parts attached to the lifting plate 39, including the spindle unit 40, rotary motor 41, pulleys 42 and 44, metal belt 45, movable body 47, and rotary head 14, is heavy, a constant force spring 58 is provided to offset this weight. This constant force spring 58 has a constant return force (load) when the leaf spring 59 is extended, regardless of the stroke. As shown in FIG. 2 , the main body of the constant force spring 58 is fixed to the upper rear surface of the guide plate 38, and the lower end of the leaf spring 59 extending from the constant force spring 58 protrudes from the rear surface of the lifting plate 39 and is connected to a protrusion 60 extending through a vertical slit in the guide plate 38. In this embodiment, the return force of the constant force spring 58 is set to be greater than the total weight of the movable parts of the second rotary unit 7, so that the rotary head 14 rises and moves away from the rotary table 11 even when air is not supplied to the air cylinder 50 of the pressing means 16. The stroke of the piston 51 of the air cylinder 50 is 60 mm.

[0038] Furthermore, because the constant force spring 58 offsets the total weight of the moving parts of the second rotating unit 7, the pressing force can be fine-tuned by adjusting the pressure applied by the air cylinder 50. The contact pressure applied by the pressing means 16 can be calculated from the monitored pressure of the vacuum regulator 57, taking into account the difference between the total weight of the moving parts of the second rotating unit 7 and the return force of the constant force spring 58. However, to obtain an accurate contact pressure between the workpiece W and the polishing pad P, it is necessary to measure the pressure in the chamber 1 using a load cell and obtain a calibration curve for the monitored pressure of the vacuum regulator 57. When the pressure inside the chamber 1 is reduced, a force pulling the operating shaft 49 is applied to the total weight of the moving parts of the second rotating unit 7. Furthermore, the rigidity of the top plate 48 is also important because the contact pressure changes if the top plate 48 bends inward when the chamber 1 is depressurized. Therefore, if necessary, it may be considered to insert a reinforcing member such as a truss structure between the frame 21 and the top plate 48, or to lay a reinforcing member on the top plate 48.

[0039] As shown in FIGS. 1 and 2 , the fixed electrode plate 18 of the counter electrode plate 17 is held parallel to the upper surface of the rotary table 11 by four fixed rods 61, ..., hanging down from the fixed plate 37 of the stand 21. The lower half of the fixed rod 61 is formed as an insulating rod 62, and is insulated from the chamber 1. As shown in FIGS. 4 and 6 , the fixed electrode plate 18 has an opening 63 formed in the center through which the rotary head 14 passes. The opening 63 needs to be large enough to ensure sufficient spatial insulation between the rotary head 14 and the opening 63, which can accommodate a workpiece W with a diameter of 4 inches (102 mm). Furthermore, the opening 63 is oval in shape extending in the second direction so that the fixed position of the fixed electrode plate 18 in the second direction can be adjusted.

[0040] More specifically, the counter electrode plate 17 has an opening 63 through which the rotary head 14 passes. The counter electrode plate 17 is composed of a fixed electrode plate 18 having a pair of parallel side edges extending in the second direction, the distance between the two edges being smaller than the diameter of the turntable 11, and movable electrode plates 19 and 20 disposed adjacent to the two side edges of the fixed electrode plate 18 and displacing in the second direction together with the turntable 11. The turntable 11 and the counter electrode plate 17 constitute a capacitively coupled plasma generating means. The fixed electrode plate 18 and the movable electrode plates 19 and 20 are both made of a conductive material, but their surfaces may be covered with a thin dielectric film that is resistant to plasma. For example, the fixed electrode plate 18 and the movable electrode plates 19 and 20 may be made of aluminum and the surfaces may be anodized.

[0041] The gas supply means 2 supplies a carrier gas and a reactive gas from a carrier gas cylinder 64 and a reactive gas cylinder 65, respectively, into the chamber 1. Note that the reactive gas is H, which is a liquid at room temperature and pressure. ２ O and H ２ O ２In this case, a mechanism is required to vaporize the gas using a liquid vaporizer instead of the reaction gas cylinder 65 and mix it with the carrier gas. The flow rates of the various gases are accurately controlled via mass flow controllers (MFCs). The flow rate of the liquid is accurately controlled via a liquid mass flow controller (LMFC). The gas exhaust means 3 is composed of a vacuum pump. The pressure of the process gas in the chamber 1 is adjusted by the gas supply means 2 and the gas exhaust means 3.

[0042] This technology is a plasma-assisted polishing apparatus that includes a capacitively coupled plasma generating means that generates plasma by applying high-frequency power between electrodes with a parallel plate structure in a process gas atmosphere containing a carrier gas and a reactive gas, and a polishing means that, after or while the neutral radicals generated by the capacitively coupled plasma generating means act on the surface of the workpiece W, forming a surface-modified layer softer than the workpiece W when they act on the surface of the workpiece, brings the workpiece W and a polishing pad P into contact with each other at a predetermined contact pressure and moves them relatively using a combination of rotational and swinging motions to remove the surface-modified layer of the workpiece W, in which one of the opposing electrode plates 17 that constitute the capacitively coupled plasma generating means is composed of a fixed electrode plate 18 that is immovable with respect to the swinging motion, and movable electrode plates 19, 20 that displace with the swinging motion.

[0043] More specifically, the present technology includes a polishing means having a first rotary shaft 10 facing a first direction and a rotary table 11 that also serves as one electrode of a parallel plate structure, a rotary head 14 having a second rotary shaft 13 facing the first direction and facing the rotary table 11 and having an area smaller than that of the rotary table 11, and a swing mechanism (linear drive means 8) that linearly moves the rotary table 11 in a second direction perpendicular to the first direction, and the capacitively coupled plasma generating means has a counter electrode plate 17 arranged parallel to the rotary table 11, and the counter electrode plate 17 is The device is configured to include a fixed electrode plate 18 having an opening 63 through which the rotating head 14 passes, a pair of side edges extending in the second direction that are parallel and the distance between the two edges is smaller than the diameter of the rotating table 11, movable electrode plates 19, 20 arranged close to both side edges of the fixed electrode plate 18 and displacing in the second direction together with the rotating table 11, and a high-frequency power source 5 that supplies high-frequency power between the opposing electrode plate 17 and the rotating table 11, and either a workpiece W or a polishing pad P is attached to the rotating table 11 and the rotating head 14, respectively.

[0044] In this way, the counter electrode plate 17 constituting the capacitively coupled plasma generating means is composed of a fixed electrode plate 18 having a pair of parallel side edges extending in the second direction and a distance between the two edges that is smaller than the diameter of the turntable 11, and movable electrode plates 19, 20 that are disposed close to both side edges of the fixed electrode plate 18 and displace in the second direction together with the turntable 11. This minimizes the area of ​​the counter electrode plate 17 and makes it possible to make the plasma generation region as small as possible, thereby reducing the amount of power input, suppressing temperature rise, reducing thermal damage to the workpiece W, and improving the durability of the mechanical components, particularly the bearings of the movable components. In other words, in a plasma-assisted polishing apparatus having both rotational and oscillating motions, it is possible to stably generate and maintain plasma even during the oscillating motion, and it is possible to minimize the plasma generation region and reduce the amount of power input.

[0045] The counter electrode plate 17 will now be described in more detail. As shown in Figures 2, 4, 5, and 6, the fixed electrode plate 18 has a rectangular shape extending in the second direction. The long side dimension is set to be larger than the diameter of the turntable 11 by at least the oscillation amplitude, and the short side dimension is set to be smaller than the diameter of the turntable 11. The linear portions 67 of the arc-shaped movable electrode plates 19 and 20, which overlap the turntable 11 when viewed from the first direction, are arranged close to both long side edges 66 of the fixed electrode plate 18. This prevents the capacitance of the capacitively coupled plasma from changing during oscillation and minimizes the plasma generation space. When the first rotating unit 6 is oscillated by the linear driving means 8, the turntable 11 is displaced in the second direction relative to the stationary fixed electrode plate 18, but the movable electrode plates 19 and 20 are always positioned overlapping the turntable 11 in the first direction. Therefore, the capacitively coupled plasma can maintain a constant and stable power even during oscillation. Furthermore, compared with conventional plasma-assisted polishing devices, the area of ​​the opposing electrode plate 17 can be made smaller, so that the plasma does not spread into unnecessary space, reducing power consumption and preventing excessive heating of the workpiece W.

[0046] Furthermore, the fixed electrode plate 18 and the movable electrode plates 19, 20 are closely spaced apart, with a distance smaller than the distance at which capacitive coupling occurs at the frequency of the high-frequency power supply. Specifically, grooves 68 are provided along the lower portions of both long side edges 66, 66 of the fixed electrode plate 18 to accommodate the linear portions 67 of the movable electrode plates 19, 20. With the linear portions 67 of the movable electrode plates 19, 20 positioned within the grooves 68, the lower surfaces of the fixed electrode plate 18 and the movable electrode plates 19, 20 are flush with each other. High-frequency power is supplied from the high-frequency power supply 5 via a cable connected to the fixed electrode plate 18 in an impedance-matched state. If high-frequency power cannot be sufficiently transmitted between the fixed electrode plate 18 and the movable electrode plates 19, 20, flexible cables may be used to electrically connect the fixed electrode plate 18 and the movable electrode plate 19, and the fixed electrode plate 18 and the movable electrode plate 20.

[0047] The movable electrode plates 19, 20 are fixed in an electrically insulated state to a non-rotating portion of the first rotating unit 6. As shown in Figures 1, 2, and 5, a plurality of holding members 70 are attached to a flange 69 for fixing the bearing sleeve 23 to the support plate 22, and a synthetic resin receiving plate 71 extending radially outward from the lower peripheral surface of the rotating table 11 is horizontally supported by the holding members 70. A ring-shaped powder receiving tray 72 is attached to the upper surface of the receiving plate 71 along the outer periphery of the rotating table 11. In this embodiment, the movable electrode plates 19, 20 are each supported by support members 73, 73 extending from inside the powder receiving tray 72. The support member 73 is connected to two support posts 74, 74 by a mounting member 75 that can be adjusted in height. The movable electrode plates 19 and 20 are each held by the lower surface of an arm portion 76 of the mounting member 75. Here, the electrical insulation state of the movable electrode plates 19 and 20 is ensured by one or more of the holding member 70, receiving plate 71, powder receiving tray 72, and support tool 73.

[0048] In this embodiment, the interior of the chamber 1 is divided into upper and lower sections to protect the mechanical components of the first rotation unit 6 and the linear drive mechanism 8 from the corrosive gas used in the process gas and from radiant heat generated in the plasma generation region. A metal shielding plate 77 is fixed to the wall of the chamber 1 adjacent to and below the support plate 71. The shielding plate 77 has an oval opening 78 to allow for displacement during oscillation of the rotary table 11. The shielding plate 77 is constructed from a combination of multiple plates in consideration of ease of assembly and maintenance. Since the chamber 1 has multiple inspection doors 79, one or more support rods 80 extending from the bottom plate 28 are used to support the shielding plate 77 in areas where there is no wall or where the shielding plate 77 is constructed from multiple connected plates and is not sufficiently supported.

[0049] As shown in Figures 1, 2, and 4, the outer shape of the backing plate 71 is an oval that is slightly larger than the oval opening 78 of the shielding plate 77 and extends in the second direction. It overlaps the shielding plate 77 so as to constantly block the oval opening 78 even during swinging. The backing plate 71 and the shielding plate 77 divide the interior of the chamber 1 into upper and lower sections. A gas inlet port 81 is provided at the upper section of this section, and a gas exhaust port 82 is provided at the lower section. Reference numeral 83 in Figure 1 denotes a cooling water inlet port, which allows cooling by passing cooling water through a water channel formed inside the fixed electrode plate 18. The plasma generation region is located above the section into which the process gas is introduced, and a spectrometer 85 is located outside an observation window 84 provided in the inspection door 79 to monitor the plasma.

[0050] In this embodiment, a polishing pad P is mounted on the first mounting portion 12 of the rotary table 11, and a workpiece W is mounted on the second mounting portion 15 of the rotary head 14. To mount the polishing pad P on the first mounting portion 12 of the rotary table 11, as shown in FIG. 5 , a plurality of notches 86 are formed on the outer periphery of the polishing pad P. With the polishing pad P placed on the first mounting portion 12, fasteners 87 are fitted into the notches 86 from the side and screwed to the outer periphery of the rotary table 11. Here, wedge-shaped portions projecting outward are formed in the notches 86, and recessed receiving portions are formed in the fasteners 87 corresponding to the wedge-shaped portions. The engagement between the wedge-shaped portions and the receiving portions ensures a secure hold. On the other hand, to mount the workpiece W on the second mounting portion 15 of the rotary head 14, if the workpiece W is in the form of a thin wafer, the workpiece W is directly bonded to the second mounting portion 15. When removing the workpiece W from the rotary head 14, it can be easily removed by immersing it in a solvent to dissolve the adhesive. However, the method of attaching the polishing pad P and the workpiece W to the attachment portion is not limited to the above-described method, and any conventionally known structure can be used.

[0051] Furthermore, by providing grooves or an uneven structure on the polishing surface of the polishing pad P and forming a flow path that communicates with the space where plasma is generated at the contact point with the workpiece W, neutral radicals can be supplied to the polished surface of the workpiece W through the flow path. This increases the surface modification rate of the workpiece W and improves polishing efficiency. Furthermore, the presence of grooves or an uneven structure at the contact point between the workpiece W and the polishing pad P has the effect of collecting polishing debris in the recesses, suppressing the occurrence of scratches caused by the polishing debris, and suppressing sticking at the contact point.

[0052] Next, the structure of the rotary head 14 will be described with reference to FIGS. 7 to 10. The rotary head 14 includes a disk-shaped head body 88 having a second mounting portion 15 on its underside, a support shaft 89, and a linking plate 90 that holds the support shaft 89 to the head body 88. The head body 88 and the support shaft 89 are connected by the linking plate 90 so that they can pivot and rotate. As shown in FIG. 10, the tilt range α is ±2.5°. This tilt range α is provided to accommodate the tolerances of each component, accurately bring the polishing pad P and the workpiece W into close contact with each other, and ensure uniform contact pressure across the entire surface of the workpiece W. When the workpieces W are small, multiple workpieces W may be held on the second mounting portion 15 of the head body 88 of the rotary head 14 to increase polishing efficiency. Even in this case, the pivotable connection between the head body 88 and the support shaft 89 ensures uniform contact pressure on each workpiece W. The rotary head 14 is detachably connected to the end of the second rotary shaft 13 by a connector 91 in an electrically insulated state.

[0053] A washer 92 made of a superhard material is embedded in the center of the surface of the head body 88 opposite the second mounting portion 15, and slidably supports the tip of the support shaft 89. The pressing force of the pressing means 16 is received by the washer 92 via the support shaft 89, preventing deformation of the second mounting portion 15 of the head body 88 due to stress concentration. In this embodiment, the washer 92 is formed with a hemispherical concave spherical portion 93 at its center, with a central angle of less than 180°, and the tip of the support shaft 89 is formed with a convex spherical portion 94 having the same radius as the concave spherical portion 93. The radius of the convex spherical portion 94 may be smaller than the radius of the concave spherical portion 93. Furthermore, an engagement shaft 95 is perpendicularly inserted through the tip of the support shaft 89 at a position that does not contact the head body 88, with the convex spherical portion 94 fitted perpendicularly into the concave spherical portion 93 of the washer 92. Here, it is preferable that at least the tip of the support shaft 89, where the convex spherical portion 94 is formed, is made of a superhard material. The linking plate 90 has a center hole 97 formed in the center, through which the shaft portion 96 of the support shaft 89 passes, and engagement grooves 98, 98 formed continuously from the center hole 97, for receiving both ends of the engagement shaft 95 in a loose-fit state. Note that instead of having the engagement shaft 95 penetrate through the tip of the support shaft 89, protrusions equivalent to the engagement shaft 95 may be provided on both sides of the tip of the support shaft 89. Here, the "loose-fit state" means a state in which a clearance is provided between the engagement shaft 95 and the inner surface of the engagement groove 98, allowing the head main body 88 and the support shaft 89 to oscillate.

[0054] Then, the shaft portion 97 of the support shaft 89 is inserted into the central hole 97 of the link plate 90, and with the engaging shaft 95 received in the engaging grooves 98, 98 of the link plate 90, the convex spherical portion 94 of the support shaft 89 is fitted into the concave spherical portion 93 of the washer 92, and the link plate 90 is joined and screwed to the head main body 88. Four screws 99 are passed through four through holes 100 formed in the link plate 90 and screwed into threaded holes 101 formed on the back surface of the head main body 88. The through holes 100 of the link plate 90 are positioned so as to sandwich the engaging grooves 98, 98, so that the rotational force of the support shaft 89 is received by the engaging grooves 98, 98 that receive both ends of the engaging shaft 95, and is reliably transmitted to the head main body 88.

[0055] FIG. 10( a ) shows the tilt range of the support shaft 89 in the direction in which the engagement shaft 95 is provided. The tilt range α is ±2.5° with respect to the normal to the head body 88. In this case, the convex spherical portion 94 of the support shaft 89 slides in a fitted state within the concave spherical portion 93 of the washer 92, and the engagement shaft 95 moves left and right within the engagement groove 98 of the link plate 90 until its tip abuts against the back surface of the head body 88 and the bottom surface of the engagement groove 98. FIG. 10( b ) shows a state rotated 90° from the state shown in FIG. 10( a ). In this case, the convex spherical portion 94 of the support shaft 89 slides in a fitted state within the concave spherical portion 93 of the washer 92, and the engagement shaft 95 moves left and right within the engagement groove 98. Therefore, the dimensions of the engagement shaft 95 and engagement groove 98 must be designed taking the tilt range into consideration. However, if the engagement groove 98 is too large, there is a risk that the engagement shaft 95 will rattle within the engagement groove 98 when transmitting rotational force.

[0056] Finally, the connector 91 for connecting the support shaft 89 to the second rotating shaft 13 will be described with reference to FIGS. 7, 8, and 11 to 13. The connector 91 is configured by sandwiching an insulating block 102 made of a material with electrical insulation, heat insulation, and rigidity, and assembling a first fastener 103 on the rotating shaft side and a second fastener 104 on the head side. In this embodiment, the insulating block 102 is made of Macerite (a registered trademark of Kurosaki Harima Corporation), a machinable ceramic. As shown in FIGS. 8 and 12, the insulating block 102 has a thick, circular plate shape, and the first fastener 103 and the second fastener 104 are screwed to both radial end faces of the insulating block 102. Four deep countersunk holes 105 and 106 are drilled in the insulating block 102 from the radial end face toward the opposing face. Here, the deep countersunk hole 105 is used to receive a screw 107 for connecting the first fastener 103, and the deep countersunk hole 106 is used to receive a screw 108 for connecting the second fastener 104. As shown in FIG. 12 , the deep countersunk holes 105 and the deep countersunk holes 106 are alternately arranged in the circumferential direction. Also, as shown in FIG. 8 , the deep countersunk hole 105 is deep enough to allow the head of the screw 107 to be fully recessed and ensure a sufficient distance between it and the second fastener 104 on the opposite side. Similarly, the deep countersunk hole 106 is deep enough to allow the head of the screw 108 to be fully recessed and ensure a sufficient distance between it and the second fastener 103 on the opposite side.

[0057] As shown in Figures 8 and 11, the first fastener 103 has a connecting hole 110 in its center into which a reduced-diameter portion 109 formed in a stepped shape at the tip of the second rotating shaft 13 is inserted, and a threaded hole 111 into which a screw 107 is screwed is formed around the connecting hole 110 at a position corresponding to the deep countersunk hole 105, and a through hole 112 of the same diameter as the deep countersunk hole 106 is formed at a position corresponding to the deep countersunk hole 106. A slit 113 is formed between the connecting hole 110 and one of the through holes 112, and in the radius portions sandwiching the slit 113, a countersunk hole 114 is formed from the circumferential surface side of one of the radius portions toward the slit 113, and a threaded hole 115 is formed in the other radius portion in the same direction as the countersunk hole 114. Then, after fitting the reduced diameter portion 109 of the second rotating shaft 13 into the connecting hole 110, a fastening screw 116 is inserted through the countersunk hole 114, passed through the slit 113, and screwed into the screw hole 115, thereby tightening and connecting the reduced diameter portion 109.

[0058] As shown in Figures 8 and 13, the second fastener 104 has a flange portion 117 and a cylindrical portion 118 that are integral with each other, and a connecting hole 120 is formed in the center, penetrating the flange portion 117 and the cylindrical portion 118, into which a reduced-diameter portion 119 formed in a stepped shape at the tip of the support shaft 89 is inserted.A threaded hole 121 is formed around the connecting hole 120 at a position corresponding to the deep countersunk hole 106, into which the screw 108 is threaded, and a through hole 122 of the same diameter as the deep countersunk hole 105 is formed at a position corresponding to the deep countersunk hole 105.A slit 123 is formed in the cylindrical portion 118, extending from the connecting hole 120 toward the circumferential surface.In the radius portions sandwiching the slit 123, a countersunk hole 124 is formed from the circumferential surface side of one radius portion toward the slit 123, and a threaded hole 125 is formed in the other radius portion in the same direction as the countersunk hole 124. Furthermore, a slit 126 perpendicular to the axis is formed at the boundary between the flange portion 117 and the cylindrical portion 118, extending from the portion where the slit 123 is provided beyond the connecting hole 120, partially separating the flange portion 117 and the cylindrical portion 118 and facilitating deformation of the cylindrical portion 118 at the slit 123. In other words, the cross section of the cylindrical portion 118 perpendicular to the axis is C-shaped due to the presence of the slit 123. Then, after the reduced-diameter portion 119 of the support shaft 89 is fitted into the connecting hole 120, a fastening screw 127 is inserted through the countersunk hole 124, passes through the slit 123, and is screwed into the threaded hole 125, tightly tightening the reduced-diameter portion 108 to connect them.

[0059] Furthermore, the connecting device 91 can connect the second rotating shaft 13 and the support shaft 89 of the rotating head 14 with electrical insulation and heat insulation due to the material properties of the insulating block 102, and the reduced diameter portion 109 of the second rotating shaft 13 is fitted into the connecting hole 110 of the first fastener 103, and the presence of slits 113 allows it to be crimped with the tightening force of a fastening screw 116, resulting in a rattle-free connection, and the reduced diameter portion 119 of the support shaft 89 of the rotating head 14 is fitted into the connecting hole 120 of the second fastener 104, and the presence of slits 123 allows it to be crimped with the tightening force of a fastening screw 127, resulting in a rattle-free connection. Connecting the second rotating shaft 13 and support shaft 89 with such a crimping structure can prevent chatter from occurring when polishing while the workpiece W and polishing pad are in contact with each other with a large contact pressure.

[0060] 8 and 12, in order to coaxially couple the second rotating shaft 13 and the support shaft 89 with high precision, circular convex portions 128, 129 are formed coaxially by machining on both radial surfaces (surfaces perpendicular to the first direction) of the insulating block 102, and an annular recess 130 into which the circular convex portion 128 fits is formed around the joining side of the connecting hole 110 of the first fastener 103, and an annular recess 131 into which the circular convex portion 129 fits is formed around the joining side of the connecting hole 120 of the second fastener 104. The relationship between the circular convex portion 128 and the annular recess 130, and the relationship between the circular convex portion 129 and the annular recess 131 may be reversed. Alternatively, a circular protrusion 128 and an annular recess 131 may be formed coaxially on both radial surfaces of the insulating block 102, an annular recess 130 may be formed on the first fastener 103 to fit the circular protrusion 128, and a circular protrusion 129 may be formed on the second fastener 104 to fit the annular recess 131, and even in this case the relationship between the protrusions and recesses may be reversed.

[0061] Next, a rotating head 14A according to another embodiment will be described with reference to FIGS. 14 to 16. In the rotating head 14A of this embodiment, the support shaft 89 and engagement shaft 95 are similar to those described above, but the head main body 88 and linking plate 90 have different structures, with an engagement groove 98 provided in the head main body 88. Other similar components are denoted by the same reference numerals and will not be described again. A circular mounting recess 132 for embedding a disk-shaped washer 92 is formed in the center of the face of the head main body 88 opposite the second mounting portion 15. An engagement groove 98 is formed in the diameter direction of the mounting recess 132, and a threaded hole 101 for threading a screw 99 is also formed. The engagement groove 98 of the head main body 88 has a cross-sectional shape slightly larger than that of the engagement shaft 95. The linking plate 90 for holding the engagement shaft 95 within the engagement groove 98 is a disk with a center hole 97 for inserting the support shaft 89 and a through hole 100 for inserting the screw 99.

[0062] FIG. 17 shows the relationship between the rotary table 11 and the rotary head 14, indicating the home positions of their respective rotation centers. The first rotary shaft 10 of the rotary table 11 and the second rotary shaft 13 of the rotary head 14 are offset so that their centers do not overlap during the swinging motion. In the figure, P1 indicates the rotation center of the rotary table 11, and P2 indicates the rotation center of the rotary head 14. The rotary table 11 swings in the second direction, with a stroke of ±75 mm. At the home position, the rotation center P2 of the rotary head 14 is set at a distance D: 40 mm from the rotation center P1 of the rotary table 11 in the second direction and d: 15 mm in the direction perpendicular to the second direction. The position perpendicular to the second direction can be adjusted by moving and fixing the base plate 29, on which the first rotary unit 6 and the linear drive unit 8 are mounted, onto the bottom plate 28 of the chamber 1, as shown in FIGS. 1 and 3 . In other words, guide members 134, 134 are fixed to the bottom plate 28 along both side edges 133, 133 of the rectangular base plate 29 that are perpendicular to the second direction, and the base plate 29 is displaced along the guide members 134, 134 and fixed to the bottom plate 28 at a predetermined position using bolts 135 and long holes 136.

[0063] The operation of the plasma-assisted polishing apparatus according to the present technology will be briefly described. With process gas at a predetermined pressure in the chamber 1, a high-frequency voltage is applied from the high-frequency power supply 5 to the counter electrode plate 17, generating plasma in the space between the polishing pad P on the rotary table 11 and the counter electrode plate 17. If the high-frequency power supplied from the high-frequency power supply 5 is pulse-modulated, the average power is reduced, preventing excessive heating of the workpiece W and stabilizing plasma generation. As shown in FIGS. 1 and 17, with the polishing pad P and the workpiece W in contact with each other at a predetermined contact pressure, the rotary table 11 (polishing pad P) is rotated at a predetermined rotational speed, and the rotary head 14 (workpiece W) is also rotated at a predetermined rotational speed. Furthermore, as shown in FIGS. 1, 4, and 17, the linear drive means 8 is driven to oscillate the first rotary unit 6 in the second direction (horizontal direction) at a predetermined amplitude, thereby polishing the workpiece W. Here, even if the rotary table 11 is oscillated by the linear driving means 8, the overlapping area between the rotary table 11 and the opposing electrode plate 17 does not change, that is, the capacitance of the capacitively coupled plasma does not change, so the plasma generation conditions do not change and the plasma can be generated and maintained stably.

[0064] In the above embodiment, one rotary head 14 corresponds to the rotary table 11, but as shown in Figure 18, it is also possible to have a plurality of rotary heads 14, for example, three rotary heads 14, in contact with the rotary table 11 simultaneously for polishing. Each rotary head 14 can be rotated by an independent rotary drive means, or a single rotary drive means can be used to rotate a plurality of rotary heads 14 under the same conditions by linking them together using a planetary gear mechanism.

[0065] 1, 4, and 6, a dressing means 137 is provided on the fixed electrode plate 18 to brush off polishing debris adhering to the polishing pad P or to regenerate the polishing pad P. The dressing means 137 has a structure in which a dressing pad 139 is placed in a through hole 138 provided in the fixed electrode plate 18, and is pressed against the polishing pad P by a pressure plate 140 detachably attached to the upper surface of the fixed electrode plate 18. Polishing debris generated on the surface of the polishing pad P during polishing is brushed off by the dressing pad 139 as the turntable 11 rotates and swings, and is received by the dust receiving tray 72 provided around the turntable 11.

[0066] Furthermore, since this technology generates plasma near the polishing pad P, the polishing pad P and the workpiece W are heated, causing an increase in temperature. In this embodiment, as shown in FIGS. 1, 4, and 6, a temperature measuring means 141 is provided for non-contact measurement of the surface temperature of the polishing pad P. The temperature measuring means 141 observes thermal radiation through an observation hole 142 provided in the fixed electrode plate 18 with a radiation thermometer unit 143. Note that the radiation thermometer unit 143 may be attached to the fixed electrode plate 18 in an electrically insulated state, but in order to reduce heat conduction from the fixed electrode plate 18, it is attached to the underside of the fixed plate 37 of the pedestal 21 in a non-contact state with the fixed electrode plate 18.

[0067] Since the fixed electrode plate 18 serves as an opposing electrode plate for generating capacitively coupled plasma as described above, it is preferable not to provide holes or openings therein. However, the through-holes 138 and the observation holes 142 are formed in a size and position that does not significantly impair the plasma generation effect of the present technology. Neutral radicals generated in the plasma generating unit 9 are adsorbed to the surface of the polishing pad P and transported to the contact position with the workpiece W as the turntable 11 rotates. Therefore, considering the activation life of the neutral radicals, it is important to set the positions of the through-holes 138 and the observation holes 142, and in particular the position of the through-hole 138, which comes into contact with the dressing pad 139, more upstream in the rotation direction of the turntable 11. In other words, it is necessary to ensure that the neutral radicals adsorbed to the surface region of the turntable 11 after contacting the dressing pad 139 are supplied to the workpiece W before their activated state disappears.

[0068] In this technology, a parallel plate electrode structure is formed by the turntable 11 and counter electrode plate 17 of the first rotating unit 6 to generate capacitively coupled plasma. However, the first rotating unit 6 is configured to displace in a second direction to provide a swinging motion. To maintain stable plasma even during the swinging motion, the area of ​​the counter electrode plate 17 must be larger than that of the turntable 11, which serves as one of the electrode plates. Furthermore, the metallic first rotating unit 6 is grounded along with the chamber 1. Therefore, plasma generated by high-frequency power input into the gap between the turntable 11 and the counter electrode plate 17 inevitably spreads laterally across the gap, with some of it passing over the turntable 11 and into the underlying mechanism 4, or plasma is inevitably generated in metal parts below the turntable 11. Furthermore, parts exposed to the plasma are subject to direct corrosion by oxidizing neutral radicals and thermal degradation due to temperature increases caused by radiant heat. This problem becomes more pronounced as the input power of high-frequency power increases.

[0069] 19 , an insulating plate 144 with a larger area than the metal turntable 11, which also serves as an electrode plate for plasma generation, is placed directly below the metal turntable 11, with the peripheral edge 145 of the insulating plate 144 positioned radially outward of the outer periphery 146 of the turntable 11, thereby blocking the path of the plasma current and limiting the plasma generation region to the space above the insulating plate 144. Here, the dimension by which the peripheral edge 145 of the insulating plate 144 protrudes beyond the outer periphery 146 of the turntable 11 is set to at least several times the gap between the turntable 11 and the counter electrode plate 17. The thickness of the insulating plate 144 is not particularly specified, but is set to a thickness that ensures rigidity. If the turntable 11 and the lower structure are completely electrically insulated by the insulating plate 144, the turntable 11 will be grounded along with the lower structure.

[0070] In this way, by placing the insulating plate 144 directly below the turntable 11, even if the power of the high-frequency power input for plasma generation increases, the plasma generating section 9 is almost limited to the gap between the turntable 11 and the opposing electrode plate 17, and the input power is efficiently consumed on the upper surface of the polishing pad P, enabling highly efficient generation of neutral radicals.

[0071] DESCRIPTION OF SYMBOLS W: Workpiece, P: Polishing pad, 1: Chamber, 2: Gas supply means, 3: Gas exhaust means, 4: Mechanical section, 5: High frequency power supply, 6: First rotation unit, 7: Second rotation unit, 8: Linear drive means, 9: Plasma generation section, 10: Rotation shaft, 11: Rotary table, 12: First mounting section, 13: Rotation shaft, 14, 14A: Rotation head, 15: Second mounting section, 16: Pressing means, 17: Counter electrode plate, 18: Fixed electrode plate, 19: Movable electrode plate, 20: Movable electrode plate, 21: Stand, 22: Support plate, 23: Bearing sleeve, 24: Rotation motor, 25: Linear guide, 26: Movable body, 27: Linear actuator, 28: Bottom plate, 29: Base plate, 30: Support table, 31: Stepping motor, 32: Ball screw feed mechanism, 33 Movable part, 34 Support base, 35 Bearing, 36 Frame, 37 Fixed plate, 38 Guide plate, 39 Lifting plate, 40 Spindle unit, 41 Rotary motor, 42 Pulley, 43 Drive shaft, 44 Pulley, 45 Metal belt, 46 Linear guide, 47 Moving body, 48 Upper surface plate, 49 Operating shaft, 50 Air cylinder, 51 Piston, 52 Operating plate, 53 Opening, 54 Base plate, 55 Slide bearing, 56 Reaction force receiving plate, 57 Vacuum regulator, 58 Constant force spring, 59 Leaf spring, 60 Projection piece, 61 Fixed rod, 62 Insulating rod 63 Opening, 64 Carrier gas cylinder, 65 Reaction gas cylinder, 66 Long side edge, 67 Straight portion, 68 Groove portion, 69 Flange, 70 Holding member, 71 Receiving plate, 72 Powder receiving tray, 73 Support tool, 74 Support column, 75 Mounting member, 76 Arm portion, 77 Shielding plate, 78 Elliptical opening, 79 Inspection door, 80 Support rod, 81 Gas inlet port, 82 Gas exhaust port,83 Cooling water inlet port, 84 Observation window, 85 Spectroscopic analyzer, 86 Notch, 87 Fixture, 88 Head body, 89 Support shaft, 90 Linking plate, 91 Connector, 92 Washer, 93 Concave spherical portion, 94 Convex spherical portion, 95 Engagement shaft, 96 Shaft portion, 97 Center hole, 98 Engagement groove, 99 Screw, 100 Through hole, 101 Threaded hole, 102 Insulating block, 103 First fastener, 104 Second fastener, 105 Deep counterbore hole, 106 Deep counterbore hole, 107 Screw, 108 Screw, 109 Reduced diameter portion, 110 Connecting hole, 111 Threaded hole, 112 Through hole, 113 Slit, 114 Counterbore hole, 115 Threaded hole, 116 Fastening screw, 117 Flange portion, 118 Cylindrical portion, 119 Reduced diameter portion, 120 Connecting hole, 121 Threaded hole, 122 Through hole, 123 Slit, 124 Counterbore hole, 125 Threaded hole, 126 Slit, 127 Fastening screw, 128 Circular protrusion, 129 Circular protrusion, 130 Annular recess, 131 Annular recess, 132 Mounting recess, 133 Side edge, 134 Guide member, 135 Bolt, 136 Elongated hole, 137 Dressing means, 138 Through hole, 139 Dressing pad, 140 Pressing plate, 141 Temperature measuring means, 142 Observation hole, 143 Radiation thermometer unit, 144 Insulating plate, 145 peripheral portion, 146 outer periphery.

Claims

1. A plasma-assisted polishing device comprising: a mechanical section that has an attachment section that detachably holds a workpiece to be polished and a polishing pad facing each other, and that moves the workpiece and the polishing pad relatively while bringing them into contact with each other at a predetermined contact pressure; and a plasma generating section that generates plasma based on a process gas and generates neutral radicals that, when the plasma acts on the surface of the workpiece to be polished, form a surface modified layer that is softer than the workpiece; wherein the mechanical section comprises at least: a first rotation unit having a rotary table with a first rotation axis facing a first direction and a first attachment section that holds the polishing pad or the workpiece; a second rotation unit that has a second rotation axis facing the first direction and a rotary head with a second attachment section that is smaller in area than the rotary table and holds the workpiece or the polishing pad, and a pressing means that displaces in the first direction and applies contact pressure between the workpiece and the polishing pad; and wherein the rotary head has a head main body with the second attachment section on its underside, and a support shaft that is connected to the head main body by a linking plate so that the head can swing and rotate relative to the head main body. a plasma-assisted polishing apparatus in which an end of the support shaft is coaxially connected to an end of the second rotating shaft by an electrically insulating connector, and at least the support shaft is detachable from the connector.

2. A plasma-assisted polishing apparatus as described in claim 1, wherein a washer for slidably receiving the tip of the support shaft is embedded on the surface of the head body opposite the second mounting portion, an engagement shaft is perpendicularly inserted through the tip of the support shaft, the link plate has a central hole in the center that passes through the shaft portion of the support shaft, and the link plate or the head body has engagement grooves that receive both ends of the engagement shaft with clearance, and the link plate is detachably attached to the head body.

3. A plasma-assisted polishing apparatus as described in claim 2, wherein the washer has a concave hemispherical portion at its center with a central angle of less than 180°, and the tip of the support shaft has a convex spherical portion with a radius equal to or smaller than that of the concave spherical portion.

4. A plasma-assisted polishing apparatus according to claim 3, wherein at least the washer, out of the washer and the convex spherical portion of the support shaft, is made of an ultra-hard material.

5. A plasma-assisted polishing apparatus as claimed in claim 1, wherein the connecting device is constructed by assembling a first fastener and a second fastener, each made of metal, with an insulating block made of an electrically insulating material sandwiched therebetween, the first fastener being attached to the end of the second rotating shaft, and the second fastener being attached to the end of the support shaft of the rotating head.

6. A plasma-assisted polishing apparatus as described in claim 5, wherein the first fastener has a connecting hole into which the end of the second rotating shaft is inserted, and the second fastener has a connecting hole into which the end of the support shaft is inserted, and a circular protrusion is provided on one side of the periphery of the connecting hole of the first fastener and the periphery of the connecting hole of the second fastener, which are respectively joined to both radial faces of the insulating block, and an annular recess is provided on the other side into which the circular protrusion is fitted.

7. A plasma-assisted polishing apparatus as described in claim 5 or 6, wherein the first fastener and the second fastener are each provided with a plurality of screw holes for screwing an insulating block, the insulating block is provided with countersunk holes for screwing the first fastener and the second fastener from both radial side surfaces, and further, through holes for inserting screws into the first fastener and the second fastener are provided at positions corresponding to the countersunk holes, and the first fastener and the second fastener are connected in an electrically insulated state via the insulating block.

8. A plasma-assisted polishing apparatus as described in claim 6, wherein a slit is formed facing outward in each connecting hole of the first fastener and the second fastener, and a fastening screw is threaded beyond the slit in the radius portion sandwiching the slit, thereby tightening and connecting the end of the second rotating shaft or the end of the support shaft inserted into the connecting hole.

9. A plasma-assisted polishing apparatus according to claim 5, wherein said insulating block is made of a machinable ceramic material having electrical insulation, heat insulation and rigidity.

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