JP4173750B2 - Mask blank substrate manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a mask blank substrate manufacturing method including a step of polishing a mask blank substrate for exposure of KrF, ArF, F2, and EUV while supplying a polishing liquid.
[0002]
[Prior art]
  2. Description of the Related Art Conventionally, a polishing apparatus is known that uses a substrate (particularly a glass substrate) used for a lithography photomask, magnetic disk, liquid crystal display, or the like as a workpiece to be polished, and polishes both or one side thereof (for example, Patent Documents). 1 and 2).
  This type of polishing apparatus sets a workpiece to be worked in a work holding hole of a carrier and sandwiches it between an upper surface plate and a lower surface plate to polish both or one side of the workpiece to be polished. It is. Hereinafter, a planetary gear type polishing apparatus will be described.
[0003]
  The planetary gear type polishing device is engaged with the sun gear, the internal gear concentrically arranged on the outer side, the sun gear and the internal gear, and rotates and rotates according to the rotation of the sun gear and the internal gear. Carrier, an upper surface plate and a lower surface plate capable of sandwiching a workpiece to be polished held from above and below, and a polishing liquid supply unit for supplying a polishing liquid between the upper surface plate and the lower surface plate ing.
[0004]
  During polishing, the workpiece to be polished held by the carrier is sandwiched between the upper and lower surface plates, and the polishing liquid is supplied between the polishing surface (polishing pad) of the upper and lower surface plates and the workpiece to be polished. The carrier revolves and rotates according to the rotation of the sun gear and the internal gear. At this time, the upper surface plate and the lower surface plate are also rotated as necessary.
[0005]
  In such a polishing apparatus, a donut-shaped region between the sun gear and the internal gear and sandwiched between the upper surface plate and the lower surface plate is an actual polishing region. The polishing liquid is supplied to this donut-shaped polishing region through a polishing liquid supply hole formed in the upper surface plate.
  As the polishing liquid, various kinds of particles in which fine polishing particles such as cerium oxide and silica are dispersed in a liquid such as water and an alkaline solution are selectively used according to the purpose of polishing.
[0006]
  In recent years, in semiconductor manufacturing lithography, with the miniaturization of integrated circuits, light having a short wavelength such as KrF (248 nm), ArF (193 nm), F2 (157 nm), EUV or the like is being used.
  When the light used for lithography exposure has a short wavelength, a small defect on the mask substrate affects the transfer pattern, so that the required defect level becomes severe.
[0007]
  In order to meet such a demand for a severe defect level, a polishing process using finer abrasive particles has been performed.
  In recent years, a defect inspection method for optically detecting fine defects on a substrate has also been proposed. According to such a defect inspection method, it is possible to detect even a fine defect of 1 μm or less which is difficult to detect by visual inspection.
[0008]
[Patent Document 1]
          JP 2001-30159 A (page 3, FIG. 3)
[Patent Document 2]
          JP 2002-127000 A (7th page, FIG. 1)
[0009]
[Problems to be solved by the invention]
  However, it has been found that, in such a severe defect level polishing process, even if sufficiently fine abrasive particles are selected so as to obtain a desired defect level, defects exceeding the allowable level are generated in the substrate.
  As a result of investigation by the present inventor, the above-mentioned defects are caused by the abrasive particles adhering in the polishing apparatus being agglomerated and fixed (aggregated and solidified), which peels off due to the vibration of the polishing apparatus, etc. It turned out to be mixed.
[0010]
  Such a defect cannot be detected by a conventional visual inspection, and the influence on the transfer pattern is small in lithography using light having a relatively long wavelength. For this reason, conventionally, this has not been a problem, but when using light having a short wavelength in lithography, it is necessary to deal with such defects.
[0011]
  Therefore, the present inventor has investigated the places where the agglomeration and fixation of the abrasive particles are likely to occur in the polishing apparatus. As a result, as shown in Patent Document 1, in the polishing apparatus in which the upper surface of the internal gear is made higher than the upper surface of the carrier so that the polishing liquid does not flow out of the internal gear, it is formed on the internal gear. It has been found that the abrasive particles tend to agglomerate and adhere to the upper and upper surfaces of the inner peripheral side surface of the gear portion.
[0012]
  That is, in the polishing apparatus as described above, as shown in FIG. 11, when polishing is performed while supplying the polishing liquid between the upper surface plate 120 and the lower surface plate 110, the polishing liquid is applied to the upper surface of the carrier 150. It is transmitted and reaches the internal gear 140. This polishing liquid is also influenced by centrifugal force, and may not only reach the upper part of the inner peripheral side surface of the gear part 140a in the internal gear 140 but may also reach the upper surface of the gear part 140a.
  The upper part and the upper surface of the inner peripheral side surface of the gear part 140a in the internal gear 140 are not areas where the polishing liquid reaches constantly, and the attached polishing liquid is easy to dry, so that the abrasive particles contained in the polishing liquid are aggregated and fixed. End up.
[0013]
  As described above, the abrasive particles agglomerated and fixed to the gear portion 140a of the internal gear 140 may be peeled off due to the vibration of the polishing apparatus or the like and may fall on the carrier 150. Therefore, the abrasive particles are mixed into the polishing liquid in the polishing region. There is a high possibility of scratching the workpiece.
  Scratches that occur in the workpiece to be polished due to such a reason are comparatively small, but in a polishing process with a strict defect level, it is eliminated as a defective product and the yield is reduced.
[0014]
  Therefore, in order to cope with the above problem, it is proposed to frequently clean the gear portion 140a of the internal gear 140. However, the gear portion 140a of the internal gear 140 has irregularities and is not easy to clean, and it takes a long time to clean. Therefore, there is a problem that the polishing work is interrupted for a long time, resulting in a decrease in productivity. there were.
[0015]
  The present invention has been considered in view of the above circumstances, and while preventing the polishing liquid from flowing out of the internal gear, it prevents agglomeration and fixation of abrasive particles in the internal gear, As a result, it is possible to suppress the generation of defects due to the agglomerated and fixed abrasive particles, improve the yield of the polishing process, facilitate the cleaning of the internal gear, and improve the efficiency of the polishing process. It aims at providing the manufacturing method of the board | substrate for mask blanks which can be performed.
[0016]
[Means for Solving the Problems]
  In order to achieve the above object, a mask blank substrate manufacturing method of the present invention includes a sun gear, an internal gear arranged concentrically on the outer side thereof, a workpiece to be polished, the sun gear, A carrier that meshes with the internal gear and rotates while revolving around the sun gear according to the rotation of the sun gear and / or the internal gear, and the workpiece to be polished held by the carrier up and down. A polishing liquid supply unit for supplying a polishing liquid between the upper surface plate and the lower surface plate, and an upper surface plate and a lower surface plate that can be sandwiched from the upper surface plate and the lower surface plateAnd comprisingThe internal gearOn the inner circumference sideMeshes with the carrierGear partThe ring part is formed on the outer peripheral sideFormedUsing a polishing apparatus, the polishing liquid used for polishing reaches the upper surface of the gear portion from the carrier side, andThe polishing liquid is applied to the anti-drying member provided on the upper surface of the ring portion and formed of a water-absorbing material.Let reachAnti-drying memberThe method includes a step of polishing a mask blank substrate for exposure of KrF, ArF, F2, and EUV while keeping the substrate in a wet state.
[0017]
  In this way, even if the polishing liquid is restricted from flowing out of the internal gear, the upper surface of the gear portion of the internal gear is always wet with the polishing liquid, and the agglomeration and fixation of the abrasive particles is prevented. Can be prevented.
[0018]
  As a result, the gear portion of the internal gearAnd ring partThe conventional problem that the agglomerated and fixed abrasive particles are separated and mixed into the polishing liquid in the polishing region to damage the workpiece is eliminated. As a result, it is possible to suppress the occurrence of defects due to the agglomerated and adhered abrasive particles and improve the yield of the polishing process.
[0019]
  Further, since the aggregation of the abrasive particles is prevented, the internal gear can be easily cleaned, so that the interruption of the polishing process operation due to the cleaning can be suppressed and the efficiency of the polishing process can be improved.
[0020]
  Further, the present invention is a method for manufacturing a mask blank substrate using the polishing apparatus, wherein the upper surface of the gear portion is substantially the same height as the upper surface of the carrier.
[0021]
  Further, the present invention provides the gear unit upper surface and / or the ring unit.TopIs a slope that becomes higher toward the outer peripheral side, and this slope is a method for manufacturing a mask blank substrate using the polishing apparatus formed over substantially the entire circumference of the internal gear.
[0022]
  In this way, since the polishing liquid that has reached the internal gear from the carrier side can be reliably guided to the inner peripheral side surface of the ring portion, the upper surface of the gear portion is constantly wetted over the entire circumference, Aggregation fixation can be prevented.
[0023]
  The present invention also provides:A sun gear, an internal gear arranged concentrically on the outer side, a workpiece to be polished, and meshed with the sun gear and the internal gear, and the sun gear and / or the internal gear A carrier that rotates while revolving around the sun gear according to rotation, an upper surface plate and a lower surface plate that can sandwich the workpiece to be polished held by the carrier from above and below, the upper surface plate, A polishing liquid supply section that supplies a polishing liquid between the lower surface plate, a gear section that meshes with the carrier is formed on the inner peripheral side of the internal gear, and a ring section is formed on the outer peripheral side Using the apparatus, the polishing liquid used for polishing reaches the upper surface of the gear part from the carrier side, and the polishing liquid that has passed through the upper surface of the gear part is continuously applied over substantially the entire circumference of the ring part. When you collect it in the concave part In, while overflowing the polishing liquid on the inner peripheral side of the internal gear from the concave portion KrF , ArF , F2 , EUV Polishing a mask blank substrate for exposureThis is a method for manufacturing a mask blank substrate.
[0024]
  If it does in this way, the dry prevention effect of a gear part can be heightened by storing a polishing liquid in a concave part steadily.
[0025]
  Moreover, since the polishing liquid accumulated in the concave portion spreads in the circumferential direction and reaches almost the entire circumference of the ring portion, and overflows from the concave portion to the inner peripheral side of the internal gear, the entire circumference of the gear portion is evenly distributed. Can get wet. Thereby, the agglomeration fixation of the abrasive particles due to partial drying of the gear part can also be prevented.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Overview of polishing apparatus]
  First, an outline of a polishing apparatus used in the present invention (a part in common with the prior art) will be described with reference to FIGS.
[0027]
  FIG. 1 is a sectional view of the polishing apparatus, and FIG. 2 is an internal perspective view in which a part of the polishing apparatus is omitted.
  As shown in these drawings, the polishing apparatus includes a planetary gear type polishing processing unit including a lower surface plate 10, an upper surface plate 20, a sun gear 30, an internal gear 40, a carrier 50, a polishing liquid supply unit 60, and the like. It has.
[0028]
  The lower surface plate 10 is a disk member having an annular horizontal upper surface, and a polishing pad 11 is attached to the upper surface. The lower surface of the lower surface plate 10 is fixed to a lower support member 12 that is rotatable about a vertical axis A (a vertical axis that passes through the center of the polishing portion). The lower support member 12 is linked to the lower surface plate rotation drive unit 13, and the lower surface plate 10 and the lower support member 12 are rotated by the drive.
  The lower surface plate 10 may be fixed so as not to rotate.
[0029]
  The upper surface plate 20 is a disk member having an annular horizontal lower surface, and a polishing pad 21 is attached to the lower surface facing the lower surface plate 10. The upper surface of the upper surface plate 20 is fixed to an upper support member 22 that can rotate about a vertical axis A. The upper support member 22 is linked to the upper surface plate rotation drive unit 23, and the upper surface plate 20 and the upper support member 22 are rotated by the drive.
  The upper surface plate 20 and the upper support member 22 are supported so as to be movable up and down along the vertical axis A, and are moved up and down by driving an upper surface plate lifting and lowering drive unit (not shown).
  The upper surface plate 20 may be fixed so as not to rotate.
[0030]
  The sun gear 30 is rotatably provided at the center position of the polishing unit, and is rotated about the vertical axis A in accordance with the drive of the sun gear rotation drive unit 31. However, when rotating the internal gear 40, the sun gear 30 may be fixed so as not to rotate.
  Moreover, although the sun gear 30 of the present embodiment is a spur gear in which a tooth row is integrally formed on a side surface portion, it may be a pin gear or the like.
[0031]
  The internal gear 40 is a ring-shaped gear having a tooth row on the inner peripheral side, and is arranged concentrically outside the sun gear 30. Although the internal gear 40 of the present embodiment is fixed so as not to rotate, the internal gear 40 can rotate about the vertical axis A, and rotates in accordance with the drive of an internal gear rotation drive unit (not shown). It may be.
  Also, in the internal gear 40, a pin gear or the like may be used in addition to the spur gear.
[0032]
  The carrier (planetary gear) 50 is a thin plate-like disk member having a tooth row on the outer peripheral portion, and one or a plurality of work holding holes 50a for holding the workpiece W to be polished are formed.
  Note that the carrier 50 may be of a double carrier type in which a holder for the workpiece W is loosely inserted into a hole formed in the carrier.
[0033]
  A plurality of carriers 50 are usually arranged in the polishing portion. These carriers 50 mesh with the sun gear 30 and the internal gear 40 and rotate while revolving around the sun gear 30 according to the rotation of the sun gear 30 and / or the internal gear 40.
  That is, the workpiece W held by the carrier 50 is sandwiched between the upper surface plate 20 and the lower surface plate 10, and the carrier 50 is rotated and rotated in this state, whereby the upper and lower surfaces of the workpiece W are polished. Is done.
[0034]
  In such a polished portion, the outer diameters of the upper surface plate 20 and the lower surface plate 10 are usually smaller than the inner diameter of the internal gear 40, and between the sun gear 30 and the internal gear 40 and above A donut-shaped region sandwiched between the surface plate 20 and the lower surface plate 10 is an actual polishing region.
[0035]
  The polishing liquid supply unit 60 is a plurality of polishing liquid storage units 61 for storing the polishing liquid, and a plurality of polishing liquids stored in the polishing liquid storage unit 61 are supplied to the polishing region between the upper surface plate 20 and the lower surface plate 10. The tube 62 is configured.
  The polishing liquid reservoir 61 is formed in an annular shape on a horizontal plane, and is provided at a position above the upper support member 22 via a plurality of support members 63.
[0036]
  The upper support member 22, the upper surface plate 20, and the polishing pad 21 are formed with a plurality of through holes 22a, 20a, and 21a communicating with each other, and the lower ends of the tubes 62 are connected thereto. Thereby, the polishing liquid stored in the polishing liquid storage part 61 is supplied to the polishing region between the upper surface plate 20 and the lower surface plate 10 through the tube 62 and the through holes 22a, 20a, and 21a.
  Although not shown in the figure, the polishing liquid supplied to the polishing region is recovered in the tank via a predetermined recovery path, and then again returned to the polishing liquid via a reduction path where a pump and a filter are interposed. It is sent to the storage unit 61.
[0037]
[Polishing liquid]
  As the polishing liquid, one in which fine abrasive particles are dispersed in a liquid is generally used.
  The abrasive particles are, for example, silicon carbide, aluminum oxide, cerium oxide, zirconium oxide, manganese oxide, colloidal silica, and the like, and are appropriately selected according to the material of the workpiece W and the surface roughness of the workpiece.
  These abrasive particles are dispersed in a liquid such as water, an acidic solution, or an alkaline solution to obtain a polishing liquid.
[0038]
[Work to be polished]
  The present invention is useful for planar polishing using a flat substrate as a workpiece W to be polished. Surface polishing includes double-side polishing and single-side polishing.
  Examples of such a workpiece to be polished W include a photomask blank substrate for forming a photomask used for lithography, a substrate for forming a liquid crystal display device, an information recording medium such as a magnetic disk, an optical disk, and a magneto-optical disk. For example, a substrate or a semiconductor wafer may be used. In particular, it is useful for a photomask blank substrate in which fine scratches affect device performance.
[0039]
  Examples of the shape of the workpiece W include a rectangle, a circle, a disk, and a block shape.
  Examples of the material of the workpiece W include glass, crystallized glass, silicon, compound semiconductors (such as silicon carbide and GaAs), metals (such as aluminum, titanium, and platinum), and carbon.
[0040]
[Detailed description of internal gear]
  Next, the internal gear 40 which is a characteristic part of the polishing apparatus will be described with reference to the drawings.
  The internal gear 40 is assumed to be used in a polishing apparatus that restricts the polishing liquid from flowing out of the internal gear 40.
  First, a configuration common to each embodiment of the internal gear 40 will be described with reference to FIG.
  FIG. 3 is a cross-sectional view of the internal gear according to the first embodiment.
[0041]
  As shown in FIG. 3, the internal gear 40 includes a gear portion 40 a in which a tooth row that meshes with the carrier 50 is formed, and a ring portion 40 b formed on the outer peripheral side thereof.
  The upper surface of the gear part 40a is formed to a height that can guide the polishing liquid that reaches the internal gear 40 through the upper surface of the carrier 50 to the inner peripheral side surface of the ring part 40b.
[0042]
  The internal gear 40 configured as described above regulates the flow of the polishing liquid to the outside thereof, and always keeps the upper surface and the inner peripheral side surface of the gear portion 40a formed on the inner peripheral side of the internal gear 40. Keep wet with the polishing liquid to prevent the polishing liquid from drying. As a result, the abrasive particles contained in the polishing liquid can be prevented from agglomerating and adhering to the upper surface and the inner peripheral side surface of the internal gear 40, and the occurrence of defects due to the agglomerated and abraded abrasive particles can be suppressed.
[0043]
  Hereinafter, each embodiment of the internal gear 40 will be described sequentially.
[First embodiment]
  As shown in FIG. 3, in the internal gear 40A of the first embodiment, the upper surface of the gear portion 40a and the inner peripheral side surface of the ring portion 40b are formed by continuous inclined surfaces 40c and 40d that become higher toward the outer peripheral side.
  The top end portion of the upper surface of the gear portion 40a is substantially the same as, slightly higher than, or slightly lower than the upper surface of the carrier 50. Then, slopes 40c and 40d are formed so as to gradually increase from the top end portion of the gear portion 40a toward the outer peripheral side.
[0044]
  The outer peripheral portion of the upper surface of the ring portion 40b is a flat surface 40e connected to the outer end of the inclined surface 40d.
  In other words, the inclined surfaces 40c, 40d and the flat surface 40e are connected to form the upper surface of the internal gear 40, and this is formed over the entire circumference of the internal gear 40, thereby eliminating the vertical surface from the upper surface of the internal gear 40. is doing.
[0045]
  The angles of the inclined surfaces 40c and 40d are such that the polishing liquid that reaches the internal gear 40A through the upper surface of the carrier 50 reaches the inner peripheral side surface of the ring portion 40b through the upper surface of the gear portion 40a. Set so that the entire top surface is fully wetted.
  That is, if the angle of the inclined surfaces 40c and 40d is too large, the polishing liquid does not reach the upper surface of the ring portion 40b. Conversely, if the angle of the inclined surfaces 40c and 40d is too small, the polishing solution passes the ring portion 40b and moves outward. In general, it is preferably set to about 30 ° to 60 °.
  The inclined surfaces 40c and 40d may be a convex curved surface or a concave curved surface in addition to a flat surface.
[0046]
  The inclined surfaces 40c and 40d can be easily formed by machining such as grinding. This processing is easy regardless of whether the gear portion 40a is formed or not.
  In the internal gear 40A of the present embodiment, since the upper surface of the gear portion 40a and the inner peripheral side surface of the ring portion 40b are formed by the inclined surfaces 40c and 40d, the processing of the inclined surfaces 40c and 40d is further facilitated. Further, compared to a case where the entire upper surface of the gear portion 40a is a flat surface having the same height as the upper surface of the carrier 50, not only can the strength of the gear portion 40a be increased, but also the meshing with the carrier 50 is difficult to disengage. There is also an advantage.
[0047]
[Operation of First Embodiment]
  When polishing is performed in the polishing apparatus, the polishing liquid reaches the internal gear 40 </ b> A along the upper surface of the carrier 50. In the internal gear 40A of the present embodiment, the top end portion of the upper surface of the gear portion 40a is substantially the same height as the upper surface of the carrier 50, so that the polishing liquid that has reached the internal gear 40A is on the upper surface of the gear portion 40a ( Is transmitted to the inclined surface 40c) and is guided to the upper surface of the gear portion 40a to reach the polishing liquid inflow allowable region (inclined surface 40d) of the ring portion 40b.
[0048]
  Normally, a plurality of carriers 50 are set in the polishing apparatus, and these carriers 50 sequentially pass through the inside of the internal gear 40A. Each time the carrier 50 passes, the polishing liquid reaches the internal gear 40A, and the upper surface (the inclined surface 40c) of the gear portion 40a is constantly kept wet by the polishing liquid. This prevents the agglomeration and fixation of the abrasive particles on the upper surface of the gear portion 40a.
[0049]
  Further, since the top end portion of the upper surface of the gear portion 40 a is substantially the same height as the upper surface of the carrier 50, the inner peripheral side surface of the gear portion 40 a rises vertically to a portion higher than the carrier 50 as in the conventional case. There is nothing. Therefore, the conventional problem that abrasive particles aggregate and adhere to the upper part of the inner peripheral side surface of the gear portion 40a is also solved.
[0050]
[Modification of First Embodiment]
  In addition, the upper surface outer peripheral part of the internal gear 40A (ring part 40b) does not necessarily need to be the flat surface 40e, for example, the inclined surface 40d may be formed to the upper surface outer peripheral end of the internal gear 40A.
  Further, in order to prevent the polishing liquid from flowing out to the outside of the internal gear 40A, a convex outflow restricting portion may be provided on the outer peripheral end of the upper surface of the internal gear 40A.
[0051]
  Furthermore, you may deform | transform the internal gear 40A of 1st embodiment as shown in FIG.
  For example, the internal gear 40A shown in FIG. 4A is formed from the upper surface intermediate position of the gear portion 40a without forming the inclined surface 40c from the upper end position of the gear portion 40a.
  Further, the internal gear 40A shown in FIG. 4B forms a slope 40d from the boundary position between the gear portion 40a and the ring portion 40b.
  Further, in the internal gear 40A shown in FIG. 4C, the inclined surface 40d is formed from the upper surface intermediate position of the ring portion 40b.
[0052]
[Second Embodiment]
  Next, an internal gear 40B according to a second embodiment of the present invention will be described with reference to FIG.
  FIG. 5 is a cross-sectional view of the internal gear according to the second embodiment.
  As shown in this figure, the internal gear 40B of the second embodiment has the same shape as the internal gear 40A of the first embodiment, but the drying prevention member 41 is provided on the upper surface of the ring portion 40b. Is different from the first embodiment.
[0053]
  As described above, the internal gear 40 according to the present invention guides the polishing liquid to the inner peripheral side surface of the ring portion 40b, thereby keeping the upper surface of the gear portion 40a wet. At this time, if there is a portion where the polishing liquid does not reach regularly on the upper surface of the ring portion 40b, the polishing liquid dries at this portion, and agglomeration and fixation of the polishing particles occurs.
  In the second embodiment, by providing the drying prevention member 41 in such a portion, the portion is always kept wet to prevent agglomeration and fixation of the abrasive particles due to drying.
[0054]
  The anti-drying member 41 has a water absorption property for absorbing the polishing liquid and a flexibility for installation along the shape of the upper surface of the ring portion 40b, and a material that does not generate dust is selected. It is formed. Examples of the material include a porous material such as a sponge, a water-absorbing cloth, a paper having a water-absorbing property and a dust-proofing property.
[0055]
  The anti-drying member 41 may be provided on the upper surface of the internal gear 40B except for the upper surface of the gear portion 40a. Preferably, as shown in FIG. 5, a drying prevention member 41 is provided over the entire upper surface of the ring portion 40b.
  The drying prevention member 41 may be fixed to the internal gear 40B, or may be detachable from the internal gear 40B. When the drying prevention member 41 is detachable, the drying prevention member 41 can be easily installed by a method of moistening the drying prevention member 41 with moisture or the like and directly attaching it to a necessary portion of the internal gear 40B.
[0056]
  Further, it is preferable that the drying preventing member 41 is always wet during polishing. For example. If the region where the polishing liquid reaches regularly is included in the installation region of the drying prevention member 41, the polishing liquid always reaches the drying prevention member 41, and the drying prevention member 41 is always kept in a wet state. Can do.
[0057]
[Operation of Second Embodiment]
  If the drying prevention member 41 is provided on the upper surface of the ring portion 40b in the internal gear 40B, even if the polishing liquid scatters on the portion of the upper surface of the internal gear 40B where the polishing liquid does not reach regularly, Since the dry preventing member 41 is always kept in a wet state, the scattered abrasive particles of the polishing liquid are not agglomerated and fixed by drying.
[0058]
  Further, if the drying preventing member 41 is continuously provided across the region where the polishing liquid reaches constantly and the region where the polishing liquid does not reach constantly, the drying preventing member 41 is always kept wet. be able to. Thereby, drying of the area | region in which the drying prevention member 41 was provided can be prevented reliably, and the agglomeration fixation of abrasive particles can be prevented.
[0059]
[Third embodiment]
  Next, an internal gear 40C according to a third embodiment of the present invention will be described with reference to FIG.
  FIG. 6 is a cross-sectional view of the internal gear according to the third embodiment.
  As shown in this figure, the internal gear 40C of the third embodiment is different from the above-described embodiment in that the ring portion 40b has a concave portion 40f continuous over substantially the entire circumference of the internal gear 40C.
[0060]
  The concave portion 40f rises vertically from the upper surface of the boundary portion between the gear portion 40a and the ring portion 40b, with an inner circumferential groove side surface 40g formed to be inclined downward on the outer circumferential side and a flat groove bottom surface 40h. It is formed from a groove side surface 40i on the outer peripheral side.
  The upper end of the groove side surface 40i is connected to a flat surface 40j formed on the outer periphery of the upper surface of the ring portion 40b. Since the height of the flat surface 40j is set to be higher than the upper surface of the carrier 50 meshed with the gear portion 40a, the polishing liquid that is about to flow out from the internal gear 40C is grooved on the outer peripheral side. Outflow is prevented by the side surface 40i.
[0061]
  The upper surface 40k of the gear portion 40a is formed at substantially the same height as the upper surface of the carrier 50, as in the above embodiment, and the polishing liquid that has reached the internal gear 40C through the upper surface of the carrier 50 is guided to the concave portion 40f. Accumulate here.
  The concave portion 40f can be formed by mechanical processing such as grinding. This processing can be performed either before or after the gear portion 40a is formed.
[0062]
[Operation of Third Embodiment]
  The polishing liquid that has reached the internal gear 40C through the carrier 50 during the polishing process passes through the upper surface 40k of the gear portion 40a provided at substantially the same height as the carrier 50 and flows into the concave portion 40f. The polishing liquid that has flowed into the concave portion 40f accumulates in the concave portion 40f and spreads in the circumferential direction along the concave portion 40f.
  As described above, in this embodiment, the polishing liquid that reaches the internal gear 40C from the carrier 50 passes through the upper surface 40k of the gear portion 40a and flows into the concave portion 40f. Therefore, the upper surface 40k of the gear portion 40a is made of the polishing liquid. It can always be kept wet to prevent agglomeration and fixation of abrasive particles.
[0063]
  Further, normally, a plurality of carriers 50 are set in the polishing apparatus, and these carriers 50 sequentially pass inside the internal gear 40C. Each time the carrier 50 passes, the polishing liquid reaches the internal gear 40C, accumulates in the concave portion 40f, flows in the circumferential direction along the concave portion 40f, and spreads around the entire upper surface of the internal gear 40C.
  As a result, the polishing liquid is also supplied to the portion where the carrier 50 is not meshed, and agglomeration and fixation of the abrasive particles due to partial drying are also prevented.
  Further, if the polishing liquid accumulated in the concave portion 40f overflows from the concave portion 40f to the inner peripheral side of the internal gear 40C, the polishing liquid is evenly applied to the upper surface and the inner peripheral side surface of the gear portion 40a not engaged with the carrier 50. As a result, the polishing liquid overflows and the effect of preventing partial drying is enhanced.
[0064]
[Modification of Third Embodiment]
  The shape of the concave portion 40f is not particularly limited as long as the polishing liquid can be accumulated. For example, it can be a U-shape or a V-shape formed by a plurality of planes. Moreover, you may form in a U shape etc. by a curved surface like the recessed part 40f shown by (a) of FIG. 7, (b). In this case, since the concave portion 40f has no corners, cleaning becomes easy.
  Further, the internal gear 40 </ b> C shown in FIG. 7B is configured by a pin gear in which a gear portion is formed by a pin 42. Even with such an internal gear 40C, it is possible to effectively prevent agglomeration and fixation of abrasive particles on the upper surface of the gear portion (the upper portion of the pin 42).
[0065]
  Next, an internal gear 40D according to a fourth embodiment of the present invention will be described with reference to FIG.
  FIG. 8 is a cross-sectional view of an internal gear according to the fourth embodiment.
  As shown in this figure, the internal gear 40D of the fourth embodiment has the same shape as the internal gear 40C of the third embodiment, but the anti-drying member 41 is provided above the ring portion 40b. Is different from the third embodiment.
[0066]
  The drying prevention member 41 is provided across the flat surface 40j of the ring portion 40b and the groove side surface 40i on the outer peripheral side of the concave portion 40f. The material and installation method of the drying prevention member 41 are the same as those in the first embodiment.
  The region where the anti-drying member 41 is provided is mainly a region where the polishing liquid does not reach regularly during the polishing process, but it is desirable that the region be provided continuously so as to include a portion where the polishing liquid constantly contacts. . For example, the lower end portion of the drying prevention member 41 provided on the groove side surface 40i may be extended to the inside of the concave portion 40f where the polishing liquid is accumulated. As a result, the polishing liquid always comes into contact with a part of the drying preventing member 41, and the drying preventing member 41 can be always kept wet.
  Moreover, it is preferable to provide the drying prevention member 41 in the flat surface 40j of the ring part 40b over the whole region.
[0067]
[Operation of the fourth embodiment]
  When the anti-drying member 41 is provided in a region (the flat surface 40j and the groove side surface 40i) where the polishing liquid does not reach regularly on the upper surface of the ring portion 40b of the internal gear 40D, this region is always wet by the anti-drying member 41. Therefore, even if the polishing liquid is scattered in this region, the abrasive particles of the scattered polishing liquid are not agglomerated and fixed by drying.
[0068]
  Further, if the drying preventing member 41 is continuously provided across a region where the polishing liquid reaches steadily and a region where the polishing liquid does not reach steadily (for example, inside the concave portion 40f), drying prevention is achieved. The member 41 can always be kept wet. Thereby, drying of the area | region in which the drying prevention member 41 was provided can be prevented reliably, and the agglomeration fixation of abrasive particles can be prevented.
[0069]
[Bottom shape of internal gear]
  In the description of the first to fourth embodiments, the shape of the lower surface of the internal gear 40 is not mentioned, but it is preferable that the lower surface of the internal gear 40 has the following shape.
  As shown in FIG. 3, a slope 40m that is lower toward the outer peripheral side is formed in the lower portion of the gear portion 40a. If it does in this way, the lower part of gear part 40a can be cleaned easily.
[0070]
  Preferably, the inclined surface 40m is formed while maintaining the tooth tip length substantially equal to the thickness of the carrier 50 without sacrificing the tooth tip length (height) of the gear portion 40a. If it does in this way, cleaning of the gear part 40a can be performed more easily, maintaining the intensity | strength of the gear part 40a.
  The angle of the inclined surface 40m is preferably about 30 ° to 60 ° with respect to the horizontal. Further, the inclined surface 40m may be formed only from the gear portion 40a, but may be formed from the gear portion 40a to the ring portion 40b. The inclined surface 40m may be a curved surface such as a concave curved surface or a convex curved surface.
[0071]
[Polishing method]
  Next, the polishing method of the present invention will be described.
  First, in a state where the rotation of the lower surface plate 10, the upper surface plate 20, and the sun gear 30 (internal gear 40) is stopped, the upper surface plate 20 is raised and the lower surface plate 10 and the upper surface plate 20 are separated. In this state, the workpiece W is set in the workpiece holding hole 50a of the carrier 50.
[0072]
  The upper surface plate 20 is lowered, the workpiece W held on the carrier 50 is sandwiched between the upper surface plate 20 and the lower surface plate 10, and the polishing liquid is supplied from the polishing liquid supply unit 60 to the polishing region, and the lower surface plate 10. The upper surface plate 20 and the sun gear 30 (internal gear 40) are rotated to start polishing of the workpiece W to be polished.
[0073]
  The carrier 50 holding the workpiece W is rotated while revolving around the sun gear 30 according to the rotation operation of the sun gear 30 (internal gear 40) (FIG. 2).
  The gear drive may be both the sun gear 30 and the internal gear 40 or any one of them. The upper surface plate 20 and the lower surface plate 10 are rotated as necessary.
[0074]
  In the polishing method of the present invention, by using the internal gear 40 (A to D) of the first to fourth embodiments, the polishing liquid that has reached the internal gear 40 (A to D) from the carrier 50 side is removed from the gear. While passing through the upper surface of the portion 40a and reaching the upper surface of the ring portion 40b, the polishing liquid that has reached the upper surface of the ring portion 40b is restricted from flowing out of the ring portion 40b, while Polish.
[0075]
  Thereby, even if it is a grinding | polishing apparatus of the system which controls that a grinding | polishing liquid flows out to the outward of the internal gear 40 (AD), the gear part 40a of the internal gear 40 (AD) is the upper surface. Is kept in a constant wet state with the polishing liquid, and agglomeration and fixation of the abrasive particles are prevented.
[0076]
  Further, when using the internal gears 40C and 40D in which the concave portion 40f that is continuous over almost the entire circumference of the ring portion 40b is used, the polishing liquid is accumulated in the concave portion 40f and the polishing liquid is supplied from the concave portion 40f to the internal gear. The workpiece W is polished while overflowing to the inner peripheral side of 40C and 40D.
[0077]
  In this case, it is possible to enhance the effect of preventing the gear portion 40a from drying by constantly storing the polishing liquid in the concave portion 40f.
  Moreover, the polishing liquid accumulated in the concave portion 40f spreads in the circumferential direction and reaches almost the entire circumference of the ring portion 40b, and overflows from the concave portion 40f to the inner peripheral side of the internal gears 40C and 40D. The entire circumference of 40a can be evenly wetted. Thereby, the agglomeration fixation of the abrasive particles due to the partial drying of the gear part 40a can also be prevented.
[0078]
  After processing for a predetermined time (or a predetermined polishing processing amount), the rotation of the lower surface plate 10, the upper surface plate 20, and the sun gear 30 (internal gear 40) is stopped and the supply of the polishing liquid is stopped. The upper surface plate 20 is raised.
  The polished product subjected to the polishing process is carried out from the work holding hole 50 a of the carrier 50.
[0079]
  As described above, in the polishing method of the present invention, polishing can be performed while effectively preventing the gear portion 40a of the internal gear 40 from being dried. Therefore, the abrasive particles are not agglomerated and fixed to the gear portion 40a of the internal gear 40, and the agglomerated and fixed abrasive particles are peeled off and mixed into the polishing liquid in the polishing region, thereby scratching the workpiece W. Is resolved.
  Further, in the case where the drying preventing member 41 is provided in a region where the polishing liquid does not reach the internal gear 40 steadily, for example, on the upper surface of the ring portion 40b, the agglomeration of the abrasive particles due to drying is prevented even in this region. Polishing can be performed.
[0080]
[Examples and Comparative Examples]
  The polishing apparatus of the present invention shown in FIG. 1 is used to polish the workpiece W as a synthetic quartz glass substrate for a photomask and the internal gears 40 (A to D) as those of the first to fourth embodiments. Was compared with the case where the internal gear 140 was polished with the conventional internal gear 140 having a rectangular cross section (the conventional polishing method).
[0081]
  As the polishing liquid, colloidal silica particles dispersed with water as a solvent were used. 1000 substrates were polished by each method, and defects were inspected for 1000 substrates after polishing, and agglomeration and fixation of abrasive particles in the internal gears 40 and 140 were observed.
[0082]
  The inspection of the defect was performed by the inspection method described in Japanese Patent Application Laid-Open No. 11-24001. This inspection apparatus is a method for detecting a defect by introducing laser light into a substrate, confining it in the substrate by total reflection, and detecting light scattered by the defect and leaking from the substrate.
  A defect was inspected by such an inspection method, and a case where one defect having a size of 0.1 to 0.5 μm or more occurred was regarded as having a scratch.
  A glass substrate having a size of 0.1 to 0.5 μm or more and having no defect is used as a mask blank substrate for F2 excimer laser (wavelength 157 nm), ArF excimer laser (wavelength 193 nm), KrF excimer laser (wavelength 248 nm) exposure. Correspondingly, since the incidence of scratches (defects) is greatly reduced as in the above-described embodiment, it can be seen that the polishing apparatus of the present invention can greatly improve the manufacturing yield of the mask blank substrate.
[0083]
  In addition, the internal gears 40 and 140 used had a cross section having a width of 15 cm and a height of 5 cm at the maximum, and having gear portions 40 a and 140 a formed in an area of 3 cm on the inner peripheral side.
  As the anti-drying member 41, a resin sponge material (thickness: about 5 mm) was used, and this was affixed to a predetermined location in a state wetted with water.
[0084]
[Comparative example]
  The number of scratches in this polishing process was 185 out of 1,000 in the conventional polishing method.
  Further, when the internal gear 140 after the polishing process was observed, the agglomeration and fixation of the abrasive particles were remarkable on the inner peripheral side upper portion and the upper surface of the gear portion 140a.
[0085]
[Example 1]
  In the polishing method of the present invention using the internal gear 40A (FIG. 3) of the first embodiment, the number of scratches was 68 out of 1,000, and the scratch rate was greatly reduced.
  Further, during the polishing process, the gear portion 40a of the internal gear 40A was always wet, and no agglomeration and fixation of abrasive particles were observed.
  In this polishing process, the upper tooth tip portion of the gear portion 40a is set to the same height as the upper surface of the carrier 50, and the angles of the inclined surfaces 40c and 40d are 45 °.
[0086]
[Example 2]
  In the polishing method of the present invention using the internal gear 40B (FIG. 5) of the second embodiment, the number of scratches was 5 in 1000, and the scratch rate was further greatly reduced.
  During the polishing process, the portions other than the gear portion 40a of the internal gear 40B were always wet, and the agglomeration and fixation of the abrasive particles did not occur.
  In this polishing process, the drying prevention member 41 is installed in all regions of the upper surface of the internal gear 40B except for the upper surface of the gear portion 40a.
[0087]
[Example 3]
  In the polishing method of the present invention using the internal gear 40C (FIG. 6) of the third embodiment, the number of scratches was 8 out of 1000.
  During the polishing process, the polishing liquid overflows from the concave portion 40f to the inner peripheral side, the entire gear portion 40a and the concave portion 40f of the ring portion 40b are always kept wet, and no agglomeration and fixation of abrasive particles occur. It was.
  In this polishing process, the upper surface of the internal gear 40C was set to the same height as the upper surface of the carrier 50, the depth of the recessed portion 40f was 5 mm, and the width of the bottom surface was 7 cm.
[0088]
[Example 4]
  In the polishing method of the present invention using the internal gear 40D (FIG. 8) of the fourth embodiment, the number of scratches was 3 out of 1000.
  During polishing, the upper surface on the outer peripheral side of the internal gear 40D was always kept wet, and no agglomeration and fixation of abrasive particles occurred.
  In this polishing process, the drying prevention member 41 is installed on the outer peripheral side flat surface 40j of the internal gear 40D and the outer peripheral groove side surface 40i of the concave portion 40f.
[0089]
  According to each of the above Examples 1 to 4, after processing 1000 substrates, the internal gear 40 was cleaned. As a result, as compared with the comparative example, the polishing apparatus of each example was able to perform cleaning in less than half the time. In the case where the anti-drying member 41 is provided, cleaning is easier.
[0090]
[Manufacturing method of glass substrate for mask blanks]
  Below, the manufacturing method of the glass substrate for mask blanks of this invention is demonstrated.
  FIG. 9 is a flowchart showing a method for manufacturing a glass substrate for mask blanks.
  As shown in this figure, the mask blank glass substrate manufacturing method includes a grinding step (S101), a rough polishing step (S102), an etching treatment step (S103), a precision polishing step (S104), and a defect. And an inspection step (S105).
[0091]
  The grinding process is a process of flattening the surface of the glass substrate and adjusting the shape. For example, a glass substrate is ground while supplying a polishing liquid of aluminum oxide to a cast iron surface plate in which grooves like a grid are formed.
  The rough polishing step is a step of reducing the surface roughness while maintaining or improving the flatness obtained in the grinding step.
  For example, a hard polisher (urethane pad) or a soft polisher (suede type) is used as a polishing pad, and a glass substrate is polished while supplying a polishing liquid in which cerium oxide is dispersed in water.
[0092]
  The etching process is a process that makes the cracks extending in the depth direction from the surface of the glass substrate noticeable by the etching process.
  For example, a glass substrate is impregnated with a chemical solution, and the surface of the glass substrate is removed by etching by about 0.05 μm, thereby making the cracks existing near the surface of the glass substrate noticeable. Examples of the chemical solution include an acidic solution such as hydrofluoric acid or an alkaline solution such as sodium hydroxide.
[0093]
  The precision polishing step is mainly a step of reducing the surface roughness, and is a step of polishing the glass substrate using abrasive particles smaller than the abrasive particles used in the rough polishing step.
  For example, using a soft polisher (suede type) as a polishing pad, a glass substrate is polished while supplying a polishing liquid in which colloidal silica is dispersed in water or an alkaline solvent.
[0094]
  The defect inspection process is a process for inspecting a glass substrate for defects in order to eliminate a glass substrate in which defects are not removed even if a precision polishing process is performed or a glass substrate in which a defect has occurred in the precision polishing process as a defective product. .
  For example, when a defect existing on the surface of a glass substrate is inspected using an optical inspection method, and even one defect having a size of 0.1 to 0.5 μm or more is found, it is excluded as a defective product. The
[0095]
  The above-described polishing method of the present invention can be performed in the above-described rough polishing process and precision polishing process, and is particularly useful when performed in a precision polishing process in which a final polishing process is performed.
[0096]
  As mentioned above, although embodiment of this invention was described, of course, this invention is not limited to the said embodiment.
  In the internal gear of the present invention, the upper surface of the gear part is formed at a height that can guide the polishing liquid that has reached from the carrier side to the upper surface of the ring part, and the upper surface of the ring part is on the gear part side Any shape may be used as long as it allows the polishing liquid to flow in from the ring and regulates the outflow of the polishing liquid to the outside of the ring portion.
[0097]
  For example, like the internal gear 40E shown in FIG. 10, the upper surface of the gear portion 40a and the inner peripheral side of the ring portion 40b are continuous flat surfaces, and the outflow prevention prevents the polishing liquid from flowing out to the outer peripheral side of the ring portion 40b. The part 40n may be protruded.
[0098]
  In the second and fourth embodiments, the drying of the region where the polishing liquid does not reach regularly is prevented by the drying prevention member 41. However, the drying prevention means other than the drying prevention member 41 is used to prevent the drying. Also good. For example, the same effect can be obtained by providing means for spraying a liquid such as water in the area so as to keep the area moist.
[0099]
【The invention's effect】
  As described above, according to the present invention, while the polishing liquid is configured not to flow out of the internal gear, it prevents agglomeration and fixation of abrasive particles in the internal gear, and as a result, agglomeration. The generation of defects due to the fixed abrasive particles can be suppressed, the yield of the polishing process can be improved, the internal gear can be easily cleaned, and the efficiency of the polishing process can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a polishing apparatus.
FIG. 2 is an internal perspective view in which a part of the polishing apparatus is omitted.
FIG. 3 is a sectional view of the internal gear according to the first embodiment.
FIG. 4 is a sectional view showing a modification of the internal gear according to the first embodiment.
FIG. 5 is a cross-sectional view of an internal gear according to a second embodiment.
FIG. 6 is a cross-sectional view of an internal gear according to a third embodiment.
FIG. 7 is a cross-sectional view showing a modification of the internal gear according to the third embodiment.
FIG. 8 is a cross-sectional view of an internal gear according to a fourth embodiment.
FIG. 9 is a flowchart showing a method for manufacturing a glass substrate for mask blanks.
FIG. 10 is a cross-sectional view showing another example of the internal gear.
FIG. 11 is an explanatory view showing a conventional internal gear.
[Explanation of symbols]
  W Workpiece to be polished
  10 Lower surface plate
  20 Upper surface plate
  30 sun gear
  40 (A to E) Internal gear
  40a Gear part
  40b Ring part
  40c slope
  40d slope
  40f concave part
  41 Drying prevention member
  50 career
  60 Polishing liquid supply part

Claims (4)

A sun gear, an internal gear arranged concentrically on the outer side, a workpiece to be polished, and meshed with the sun gear and the internal gear, and the sun gear and / or the internal gear A carrier that rotates while revolving around the sun gear according to the rotation, an upper surface plate and a lower surface plate that can hold the workpiece to be polished held by the carrier from above and below, the upper surface plate, and the A polishing liquid supply portion for supplying a polishing liquid between the lower surface plate, a gear portion that meshes with the carrier is formed on the inner peripheral side of the internal gear , and a ring portion is formed on the outer peripheral side Using the device,
The polishing liquid used for polishing is made to reach the upper surface of the gear part from the carrier side,
Further, the polishing liquid is provided to the drying prevention member formed of a material having water absorption provided on the upper surface of the ring portion, and while keeping the drying prevention member always wet, KrF, ArF, F2, A method for producing a mask blank substrate, comprising a step of polishing a mask blank substrate for EUV exposure.   2. The method of manufacturing a mask blank substrate according to claim 1, wherein the polishing apparatus has an upper surface of the gear portion substantially the same height as the upper surface of the carrier. The gear portion upper surface and / or the ring upper surface is higher becomes slope as the outer peripheral side, claim 1, characterized in that the inclined surface using the polishing device formed over substantially the entire circumference of the internal gear Or the manufacturing method of the board | substrate for mask blanks of 2. A sun gear, an internal gear arranged concentrically on the outer side, a workpiece to be polished, and meshed with the sun gear and the internal gear, and the sun gear and / or the internal gear A carrier that rotates while revolving around the sun gear according to the rotation, an upper surface plate and a lower surface plate that can hold the workpiece to be polished held by the carrier from above and below, the upper surface plate, and the A polishing liquid supply portion for supplying a polishing liquid between the lower surface plate, a gear portion that meshes with the carrier is formed on the inner peripheral side of the internal gear, and a ring portion is formed on the outer peripheral side Using the device,
The polishing liquid used for polishing is made to reach the upper surface of the gear part from the carrier side,
Further, the polishing liquid that has passed through the upper surface of the gear portion is accumulated in a concave portion that is formed continuously over substantially the entire circumference of the ring portion, and the polishing liquid is transferred from the concave portion to the inner peripheral side of the internal gear. While overflowing KrF , ArF , F2 , EUV A method for producing a mask blank substrate, comprising a step of polishing a mask blank substrate for exposure.

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