JP2010228085A - Polishing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a polishing liquid from entering an inner part of a device to deteriorate rotating accuracy in the polishing device which allows a polishing tool to come into contact with a surface to be polished by pressure, rotates the polishing tool and supplies the slurry type polishing liquid including micro particles to polish the surface. <P>SOLUTION: The slurry type polishing liquid 11 including the micro particles is introduced from a hollow part 1a formed at a rotating shaft of the polishing tool 1 and supplied to a pressure contact part 23 of an object 22 to be polished to polish the object. To gaps 8a and 8b of a bearing for rotatably supporting the polishing tool 1, the same liquids 16 as a solvent of the polishing liquid 11 are supplied to prevent the micro particles of the polishing liquid 11 from entering the gaps 8a and 8b of the bearing. A polishing liquid introducing port 3 communicates with the gap 8a and the supply pressure of the liquid 16 is higher than the supply pressure of the polishing liquid 11. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polishing apparatus for polishing an optical element or the like that requires high shape accuracy.

  In recent years, a high-precision polishing apparatus used for polishing an optical element or the like mounted on an exposure apparatus using X-rays or a further short wavelength as a light source requires a polishing removal amount accuracy of several nanometers.

  Since the conventional polishing apparatus introduces a slurry-like polishing liquid containing fine particles, a mechanical seal or oil is applied to the seal portion for the purpose of preventing the polishing liquid from entering the apparatus such as a bearing that holds the rotating shaft of the polishing tool. A configuration in which a seal is arranged is known. Here, the mechanical seal has a configuration in which a sliding ring attached to the rotating shaft and a fixed ring of the bearing housing come into contact with each other on the sliding surface to stop leakage. The oil seal is made of a sealing material having a U-shaped cross section, and is fixed to the bearing housing and has a spring that presses the sealing surface of the sealing material against the outer peripheral surface of the rotating shaft, and is in contact with the sliding surface. Configured to stop leaks.

  Patent Document 1 discloses a configuration in which the material of the contact portion on the sliding surface is made of silicon carbide or the like and is formed in a pointed shape that is in line contact and pressed against each other to stop leakage. Patent Document 2 discloses a configuration in which a contact portion of each mechanical seal with each sealing ring is lubricated with lubricating water.

  Patent Document 3 further includes an outer cylinder that is provided on the outer surface of the fluid supply port, and a rotating body that is inserted into the outer cylinder, is held by a bearing and is driven to rotate, and communicates with the end surface of the rotating body from the fluid supply port. A configuration for forming a flow path is disclosed. The polishing liquid is guided to the rotating body through the mechanically sealed space.

  Furthermore, a polishing apparatus as shown in FIG. 2 has also been proposed. A polishing tool 101 having a tubular shaft portion is held by bearings 102a and 102b installed in a bearing holder 105, and is connected to a rotary motor 107 so as to be rotatable. The mechanical seals 120a and 120b are disposed in the end face direction of the bearings 102a and 102b that hold the polishing tool 101.

  The polishing liquid introduction ring 110 has a hole in the inside, is disposed with a gap in the outer peripheral portion of the polishing tool 101, and has a liquid reservoir 108 at the inner peripheral portion of the hole. The pump 112 sends the polishing liquid 111 from the polishing liquid tank 113 to the liquid reservoir 108. The rotation motor 107, the bearing holder 105, and the polishing liquid introduction ring 110 are supported by a gantry.

  During the polishing process by the rotation of the polishing tool 101, the polishing liquid 111 discharged from the liquid reservoir 108 flows out from the gap between the polishing liquid introduction ring 110 and the polishing tool 101. At the same time, a part flows into the pipe through the introduction hole 121 formed on the side surface of the polishing tool 101 and is discharged to the pressure contact portion 123 between the polishing tool 101 and the workpiece 122. The polishing liquid 111 that has become unnecessary and has accumulated in the container 124 is collected again in the polishing liquid tank 113.

  Generally, the polishing liquid is used by mixing ceramic fine particles with a solvent. The concentration of the polishing liquid largely depends on the removal amount of the polishing process, and the darker one has a larger polishing removal amount, and the thinner one has a smaller one. Conventionally, the concentration is adjusted in advance in the polishing liquid tank.

Japanese Patent No. 2941786 JP 2001-4083 A Japanese Patent Registration No.03318303

  However, when a mechanical seal is used, fine particles in the polishing liquid enter between the sliding surfaces of the mechanical seal, so that the sliding ring wears out, and the seal is destroyed at an early stage. There was a risk of intrusion.

  Oil seals also have the disadvantage that fine particles enter the sliding surface between the seal surface and the outer peripheral surface of the rotating shaft, and the seal surface wears out, causing the seal to break down early and causing leakage of the polishing liquid and intrusion into the device. It was.

  Even when the sliding part is made of silicon carbide or the like and formed into a pointed shape that makes line contact, or when it is lubricated with lubricating water, especially when rotating at high speed, fine particles enter the sliding surface and seal it. The surface could wear and the seal could be destroyed.

  Since the apparatus shown in FIG. 2 has a structure in which the polishing liquid leaks during the polishing process, the amount of leakage is non-uniform, and accurate control of the pressure of the polishing liquid at the pressure contact portion between the polishing tool and the workpiece is possible. difficult. In the polishing process, the pressure at the pressure contact portion between the polishing tool and the workpiece is proportional to the polishing removal amount, and the fluctuation in the pressure of the polishing liquid becomes the pressure fluctuation at the pressure contact portion, resulting in a fluctuation in the polishing removal amount. . In addition, fine particles enter the sliding surface between the sealing surface of the mechanical seal and the rotating shaft due to the immersion of the polishing liquid into the apparatus or the scattering of the polishing liquid, and the seal surface is worn and the seal is destroyed. As a result, the polishing liquid enters the inside of the apparatus and destroys the bearing, which may deteriorate the rotational accuracy. In the polishing process, the rotation accuracy affects the polishing removal amount, and a decrease in the rotation accuracy results in fluctuation of the polishing removal amount.

  Further, since the concentration is adjusted and used in the polishing liquid tank in advance, there is an unsolved problem that even if the concentration of the polishing liquid changes during processing, it cannot be dealt with. In the polishing process, the concentration of the polishing liquid is proportional to the polishing removal amount, and the fluctuation of the polishing liquid concentration becomes the fluctuation of the polishing removal amount.

  The present invention provides a polishing apparatus that prevents the polishing liquid from leaking or entering the inside of the apparatus due to the breakage of the seal, and that can easily control the pressure and concentration of the polishing liquid at the pressure contact portion between the polishing tool and the workpiece. It is intended.

  In order to achieve the above object, a polishing apparatus of the present invention comprises a polishing tool that is pressed against a workpiece and rotated, a rotating shaft that is integral with the polishing tool, and a hollow portion of the rotating shaft. A polishing liquid supply means for supplying a polishing liquid containing the polishing liquid to a pressure contact portion between the polishing tool and the workpiece, a bearing for rotating and supporting the rotating shaft, and a gap between the bearing and the rotating shaft in the polishing liquid A liquid supply means for supplying the same liquid as the solvent of the above, and a communication portion for communicating the gap and the hollow portion of the rotating shaft, and the polishing liquid supply means passes through the communication portion and is used for the polishing. The liquid is introduced into the hollow portion of the rotating shaft.

  The liquid supplied to the gap of the bearing prevents the slurry-like polishing liquid containing fine particles from coming into contact with the bearing portion of the bearing. Thereby, destruction of the seal by the polishing liquid can be avoided, the life of the seal can be extended, and the rotation accuracy of the polishing tool can be maintained to obtain high polishing removal amount accuracy.

  Further, it is possible to prevent pressure change due to leakage of the polishing liquid, and to control the pressure of the polishing liquid at the pressure contact portion between the polishing tool and the workpiece. As a result, higher polishing removal amount accuracy can be obtained.

  Also, by mixing the sealing liquid into the polishing liquid, it is possible to correct the increase in the polishing liquid concentration due to evaporation during processing, and maintain high polishing removal amount accuracy even during long-time processing. Can do.

1 is a schematic cross-sectional view showing a polishing apparatus according to one embodiment. It is a schematic cross section which shows the conventional grinding | polishing apparatus.

  DESCRIPTION OF EMBODIMENTS Embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 shows a polishing apparatus according to an embodiment, and a rotating shaft integral with a polishing tool 1 has a hollow portion 1a. The bearing for rotating and supporting the rotating shaft of the polishing tool 1 is an M housing in which bearings 2a and 2b, a polishing liquid introduction hole 3 constituting a polishing liquid supply means, and liquid introduction holes 4a and 4b constituting a liquid supply means are formed. 5. The polishing tool 1 is rotationally driven by a rotary motor 7 through a coupling 6. The M housing 5 is disposed with a gap 8 a between the rotating shaft of the polishing tool 1. The gap 8a is 3 to 25 μm. An S housing 10 is disposed at the lower end of the M housing 5 via an O-ring 9. Similar to the M housing 5, the S housing 10 is arranged with a gap 8 b between the rotating shaft of the polishing tool 1 and includes a liquid introduction hole 4 c. The gap 8b is 3 to 15 μm.

  The tip diameter of the polishing tool 1 is φ30 mm.

  The polishing liquid 11 is obtained by mixing fine particles of cerium oxide with pure water as a solvent.

  The polishing liquid 11 is sent from the polishing liquid tank 13 to the polishing liquid introduction hole 3 formed in the M housing 5 by the polishing liquid pump 12. A polishing liquid pressure gauge 14 is installed in the flow path to measure the supply pressure of the polishing liquid 11.

  The liquid 16 is pure water which is the same liquid as the solvent of the polishing liquid 11, and the liquid introduction holes 4 a, 4 b, 4 c formed in the M housing 5 and the S housing 10 from the liquid tank 18 by the polishing liquid pump 17. Sent to. A liquid pressure gauge 19 is installed in the flow path to measure the supply pressure of the liquid 16.

  The liquid 16 sent to the liquid introduction holes 4a, 4b, and 4c is filled in the clearances 8a and 8b between the rotating shaft of the polishing tool 1 and the M housing 5 and the S housing 10, and sealed by the O-ring 20 and the O-ring 9. Is done.

  The polishing liquid introduction hole 3 communicates with the gap 8a of the M housing 5, and the polishing liquid 11 is introduced into the hollow part 1a through four connecting holes 21 which are communication parts formed on the side surface of the rotating shaft of the polishing tool 1. Then, it is supplied to the pressure contact portion 23 between the polishing tool 1 and the workpiece 22.

The polishing liquid 11 that has become unnecessary and has flowed into the container 24 is collected in the polishing liquid drain tank 25.
The differential pressure control device 26 takes in the pressure measurement values from the polishing liquid pressure gauge 14 and the liquid pressure gauge 19, calculates the pressure difference, and sets the polishing liquid pump control apparatus 27 and the liquid pump so that the pressure difference described later is obtained. Commands are issued to both control devices 28. Furthermore, it controls both starting and stopping of both the polishing liquid pump control device 27 and the liquid pump control device 28.

  The X stage 29 and the Y stage 30 installed on the gantry place the container 24 and move the workpiece 22 in the horizontal direction.

  The polishing tool 1, the M housing 5, the coupling 6, the rotary motor 7, the S housing 10, and the like are supported by the Z slide 31, and apply a pressure as described later to the pressure contact portion 23 by adjusting the load of the weight 32. .

  Next, a polishing process using the polishing apparatus of this embodiment will be described.

  The workpiece 22 is a synthetic quartz glass having a diameter of 160 mm and is subjected to a surface polishing process.

  First, the liquid pump 17 is activated by the differential pressure control device 26, and the liquid 16 is filled in the gaps 8a and 8b between the rotating shaft of the polishing tool 1 and the respective housings through the liquid introduction holes 4a, 4b, and 4c. The supply pressure of the liquid 16 at that time was 2500 Pa.

  Then, the polishing liquid pump 12 was started by the differential pressure control device 26. Here, the supply pressure of the polishing liquid 11 was set to 1400 Pa, which is lower than the liquid 16 supplied to the gaps 8a and 8b. The differential pressure control device 26 takes in pressure measurement values from the liquid pressure gauge 19 and the polishing liquid pressure gauge 14 and issues commands to both the liquid pump control apparatus 28 and the polishing liquid pump control apparatus 27 so that the pressure difference becomes 1100 Pa sequentially. Control. Next, the polishing tool 1 was rotated at 3000 rpm by the rotary motor 7. The load applied to the pressure contact portion 23 was adjusted to 5N by adjusting the weight 32 including the polishing tool 1, the M housing 5, the coupling 6, the rotary motor 7, and the like.

  Then, the workpiece 22 was moved by the X stage 29 and the Y stage 30 and polished for 7 hours.

  The polishing liquid 11 that has passed through the polishing liquid introduction hole 3 does not enter the gaps 8a and 8b with high liquid pressure, but directly flows into the hollow portion 1a of the polishing tool 1 through the connecting hole 21 and is discharged from the pressure contact portion 23. . Only pure water is in contact with the O-ring 20 and the O-ring 9 that are sealing members, and there are no fine particles on the sliding surface between the inner periphery of the O-ring and the rotating shaft of the polishing tool 1, and there are fine particles on the sliding surface. It was not worn and destroyed.

  That is, the polishing liquid 11 containing fine particles does not come into contact with the sealing surfaces of the gaps 8a and 8b, so that the polishing liquid 11 does not leak due to the breakage of the seal, and the replacement of the seal member is unnecessary, thereby improving the productivity. did.

  In this embodiment, the distance from the bearing 2b to the tip of the polishing tool 1 is set to several tens of millimeters in order to further improve the rotation accuracy. For this reason, a large amount of the discharged polishing liquid 11 was scattered upward, but the polishing liquid did not enter the bearings 2a and 2b inside the apparatus, and the rotational accuracy of the polishing tool 1 was maintained.

  Further, the pressure change due to leakage disappeared, and the pressure of the polishing liquid 11 at the pressure contact portion 23 was equal to the value of the polishing liquid pressure gauge 14 and was accurately controlled.

  At this time, since the gap 8 a is higher than the liquid pressure in the connecting hole 21, the liquid 16 sequentially flows into the connecting hole 21 through the gap 8 a and mixes with the polishing liquid 11. The amount of inflow was 30 cc to 65 cc per hour, which coincided with the evaporation amount of the solvent of the polishing liquid 11 from the polishing liquid tank 13 and could be controlled to a constant polishing liquid concentration successively.

  In 7 hours of processing, a removal accuracy of 1.3 nanometers is always obtained, and the surface roughness of the polished surface of the workpiece 22 after processing is 2.8 nanometers RMS, which is used in an exposure apparatus. We were able to perform high-precision machining at the level.

DESCRIPTION OF SYMBOLS 1 Polishing tool 2a, 2b Bearing 3 Polishing liquid introduction hole 4a, 4b, 4c Liquid introduction hole 5 M housing 6 Coupling 7 Rotating motor 8a, 8b Gap 9, 20 O-ring 10 S housing 11 Polishing liquid 12 Polishing liquid pump 13 Polishing Liquid tank 14 Polishing liquid pressure gauge 16 Liquid 17 Liquid pump 18 Liquid tank 19 Liquid pressure gauge 21 Connecting hole 22 Workpiece 23 Pressure contact part 24 Container 25 Polishing liquid drain tank 26 Differential pressure control device 27 Polishing liquid pump control device 28 Liquid pump Control device 29 X stage 30 Y stage 31 Z slide 32 Weight

Claims (2)

A polishing tool that rotates in pressure contact with the workpiece;
A rotating shaft integral with the polishing tool;
A polishing liquid supply means for supplying a polishing liquid containing fine particles to the press contact portion between the polishing tool and the workpiece through the hollow portion of the rotating shaft;
A bearing that rotatably supports the rotating shaft;
Liquid supply means for supplying the same liquid as the solvent of the polishing liquid into the gap between the bearing and the rotary shaft;
A communication portion for communicating the gap and the hollow portion of the rotary shaft;
The polishing apparatus, wherein the polishing liquid supply means introduces the polishing liquid into the hollow portion of the rotating shaft through the communication portion.   The polishing apparatus according to claim 1, wherein a supply pressure of the liquid by the liquid supply unit is higher than a supply pressure of the polishing liquid by the polishing liquid supply unit.

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