JP2010082746A - Method for manufacturing polishing-treated object, substrate and photomask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a polishing-treated object capable of improving processing accuracy and a substrate manufactured by the method. <P>SOLUTION: The method is used for manufacturing the polishing-treated object by polishing a polishing portion 51 of an object 50 using magnetic fluid 30 including polishing particles. The method includes a step of polishing the polishing portion 51 by relatively moving a circumferential surface 111 of a wheel 11 that generates magnetism and the object 50 while the polishing portion 51 is in contact with the magnetic fluid 30 disposed on the circumferential surface 111 of the wheel 11. The polishing portion 51 is polished at least two times. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a polished product, and more particularly to a technique for manufacturing a substrate used for a photomask.

  In recent years, the progress of performance and functions of portable communication terminals, optical recording / reproducing devices, digital displays, etc. has been remarkable, and in the semiconductor field leading nanoelectronics, for example, a photomask substrate used for a lithography apparatus using EUV light, There is an increasing demand for ultra-high density processing technology for optical components such as mirror substrates. As a result, there is a need for a technology that can achieve the accuracy of ultra-precise and ultra-fine optical components with high reproducibility from submicron to nano level.

  First, regarding materials, ultra-low expansion materials such as Clear Serum (Ohara), Zerodur (Shot), Zerodur-M (Shot), ULE (Corning) are known. These materials are useful because of their extremely low thermal expansion and high dimensional uniformity even with changes in temperature environment.

On the other hand, with respect to the technology for manufacturing optical components with high accuracy from these materials, a magnetic fluid polishing method has been developed in which a magnetic fluid containing abrasive particles is used to polish an material to manufacture an optical component (Magnetro-Rheological Finishing). (For example, refer to Patent Document 1).
Japanese National Patent Publication No. 11-511395

  However, with the conventional method as shown in Patent Document 1, it is difficult to process into a design shape with high reproducibility at a level of accuracy required in the above field, although a certain level of accuracy is obtained. Met. Further, the conventional method disclosed in Patent Document 1 requires a long time for processing as the processing accuracy is increased, and thus is not suitable for industrial use that requires a large amount of production in a short time. is there.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method of manufacturing a polished product that can improve processing accuracy and reduce processing time, and a substrate manufactured by this manufacturing method. To do.

  The present inventor has found that the processing accuracy can be improved and the processing time can be shortened by polishing the portion to be polished by the magnetic fluid polishing method twice or more, and the present invention is completed. It came. Specifically, the present invention provides the following.

(1) A method for producing a polished product, wherein a magnetic fluid containing abrasive particles is used to polish a polished portion of an object to produce a polished product,
A step of polishing the polished portion by moving the circumferential surface and the object relative to each other in a state in which the polished portion is in contact with the magnetic fluid placed on the circumferential surface of the wheel that generates magnetic force. Have
A method for producing a polished product, wherein the polished portion is polished twice or more.

  (2) At least the initial polishing of the portion to be polished is performed in a state where the portion to be polished is pushed to a depth of 5% or more of the maximum height of the magnetic fluid placed on the circumferential surface ( 1) The manufacturing method of the grinding | polishing processed material of description.

  (3) At least the initial polishing of the portion to be polished is performed in a state where the portion to be polished is pushed to a depth of 65% or less of the maximum height of the magnetic fluid placed on the circumferential surface ( The manufacturing method of the grinding | polishing processed material of 1) or (2) description.

(4) The magnetic fluid according to any one of (1) to (3), wherein the magnetic fluid has a viscosity coefficient of 30.0 × 10 ⁻³ Pa · s to 63.0 × 10 ⁻³ Pa · s. Production method.

  (5) The method according to any one of (1) to (4), wherein the abrasive particles have an average particle diameter of 0.5 μm or more and 30 μm or less.

  (6) The method according to any one of (1) to (5), wherein the abrasive particles are one or more selected from the group consisting of cerium oxide and diamond.

  (7) Until the ratio of the PV value of the shape error with respect to the design shape after polishing of the portion to be polished to the PV value of the shape error with respect to the design shape before polishing of the portion to be polished is 1/5 or less, The method for producing a polished product according to any one of (1) to (6), wherein the polishing of the portion to be polished is repeated.

  (8) The polishing process according to any one of (1) to (7), wherein the polishing of the portion to be polished is repeatedly performed until the PV value of the shape error with respect to the design shape after polishing of the portion to be polished is 100 nm PV or less. Manufacturing method.

  (9) The method for producing a polished product according to any one of (1) to (8), further including a step of previously adjusting a PV value of a shape error with respect to a design shape of the portion to be polished to 700 nm PV or less.

  (10) The shape of the portion to be polished is measured each time the portion to be polished is polished, and control for adjusting the speed of relative movement of the circumferential surface and the object is performed based on the measurement result ( The method for producing a polished product according to any one of 1) to 9).

  (11) A substrate manufactured by the manufacturing method according to any one of (1) to (10), using a glass plate as the object.

  (12) A photomask substrate comprising the substrate according to (11).

  (13) A photomask using the photomask substrate according to (12).

  According to the present invention, since the portion to be polished is polished twice or more by the magnetic fluid polishing method, the error between the shape of the polished product and the design shape is greatly reduced, and the processing accuracy can be improved. In addition, by appropriately setting each polishing condition (especially the shape of the magnetic fluid that contacts the part to be polished), equivalent processing accuracy can be obtained with higher reproducibility than single polishing, and processing time Can be significantly shortened.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  In the method for manufacturing a polished product according to the present invention, a polished fluid is manufactured by polishing a portion to be polished of a target using a magnetic fluid containing abrasive particles. Details of the manufacturing process will be described with respect to an embodiment using an example of a polishing apparatus. Note that some of the components shown in each figure may be exaggerated for convenience of explanation, and in this case, the ratio of the sizes of the components in each figure is a size that is actually assumed. It is out of the ratio.

  FIG. 1 is a partial perspective view of a polishing apparatus 10 that can be used in the manufacturing method according to the present invention, and FIG. 2 is a side view of the polishing apparatus 10 of FIG. The polishing apparatus 10 includes a wheel 11, and the wheel 11 has a circumferential surface 111 as a surface on which the rotation shaft 113 is not provided.

  The fluid supply nozzle 13 and the fluid recovery unit 15 are disposed so as to be in close contact with the circumferential surface 111. The fluid supply nozzle 13 supplies the magnetic fluid 30 transferred from the fluid source through the supply pipe 14 to the circumferential surface 111, and the fluid recovery unit 15 supplies the magnetic fluid 30 recovered from the circumferential surface 111 to the recovery pipe 16. Back to the fluid source. In this way, the magnetic fluid is circulated.

  Here, as shown in FIG. 3, in the circumferential surface 111, in the vicinity of the magnetized portion 112 between the fluid supply nozzle 13 and the fluid recovery portion 15 (inward in the present embodiment), the magnetic force applying portion 20 is Under the influence of the generated magnetic field, the magnetic fluid 30 is fixed to the circumferential surface 111 and rotates together with the circumferential surface 111.

  A portion 51 to be polished of the object 50 is opposed to the magnetized portion 112 with a gap CL therebetween. Here, when the position adjusting unit 17 expands and contracts, the distance of the gap CL between the polished portion 51 and the magnetized portion 112 is adjusted. Accordingly, when the wheel 11 is rotated in a state where the polished portion 51 is in contact with the magnetic fluid 30, the polished portion 51 and the magnetic fluid 30 move relative to each other, so that the polished portion 51 is caused by the magnetic particles contained in the magnetic fluid 30. It will be polished locally.

  Since the position adjusting unit 17 can move the portion 51 to be polished in the horizontal direction and can change the posture (angle) of the portion 51 to be polished, the entire portion 51 to be polished can be polished into an arbitrary shape. The movement trajectory of the portion 51 to be polished in the horizontal direction by the position adjusting unit 17 may be appropriately set according to the shape of the portion 51 to be polished, and is not particularly limited, but the shape of the portion 51 to be polished is substantially a circle. In this case, a spiral trajectory (FIG. 4 (a)) that goes from the outside to the center and outward again is preferable, and in the case of a rectangular shape, a parallel reciprocating trajectory (FIG. 4 (b)) is preferable. .

  In this embodiment, the relative movement of the portion 51 to be polished and the circumferential surface 111 is achieved by the rotation of the wheel 11. However, the present invention is not limited to this, and the portion 51 to be polished is circular orbital along the circumferential surface 111. It may be moved. However, in this case, since the fluid supply nozzle 13 and the fluid recovery unit 15 need to be moved in accordance with the movement of the polished portion 51 in order to supply and recover the magnetic fluid 30, from the viewpoint of simplifying the apparatus. This embodiment is preferred.

  The manufacturing method of the present invention moves the circumferential surface 111 and the object 50 relative to each other in a state where the polished portion 51 is in contact with the magnetic fluid 30 placed on the circumferential surface 111 of the wheel 11 that generates magnetic force. It has the process of grind | polishing the to-be-polished part 51, and grind | polishes the to-be-polished part 51 twice or more, It is characterized by the above-mentioned. Thereby, the difference | error of the shape of the grinding | polishing processed material obtained and a design shape is reduced significantly, and processing precision can be improved.

  Conventionally, it has been considered that it is necessary to reduce the shape of the magnetic fluid in contact with the portion to be polished when trying to ensure high processing accuracy by single polishing. When the shape of the magnetic fluid that contacts the portion to be polished is reduced, the amount of processing per unit time is reduced, so that the time spent for polishing the entire portion to be polished must be increased. Here, since the polishing apparatus using the magnetic fluid polishing method is very expensive, it is required to maximize the number of products to be polished with respect to the operation time of the apparatus. In addition, if the shape of the magnetic fluid in contact with the portion to be polished is made small, the reproducibility of the processing accuracy is poor and the desired processing accuracy may not be obtained. However, in the method of the present invention, by performing polishing twice or more, if each polishing condition is appropriately set (for example, the shape of the magnetic fluid 30 in contact with the portion to be polished 51 is increased), high reproducibility is achieved. Thus, the desired processing accuracy can be achieved, and the occupation time of the polishing apparatus can be significantly shortened while maintaining the processing accuracy. Thereby, manufacturing efficiency can be improved while reducing manufacturing costs.

  FIG. 5 is a schematic diagram showing a change in a portion 51 to be polished of the object 50. First, the part 51 to be polished is polished by the magnetic fluid 30 in the first polishing (FIG. 5A). Then, the shape of the part 51 to be polished changes, and a part 51 'to be polished having a surface closer to the design shape than the part 51 to be polished is formed (FIG. 5B). Further, the portion 51 ′ to be polished is polished by the magnetic fluid 30 in the second polishing. As a result, the convex portion of the portion 51 ′ to be polished is scraped off by the magnetic fluid 30, so that a polished product 60 having a surface 61 closer to the design shape than the portion 51 ′ to be polished is manufactured (FIG. 5C). .

  Here, polishing of the portion 51 to be polished is performed by pressing the portion 51 to be polished into the magnetic fluid 30, and the magnetic fluid 30 in contact with the portion 51 to be polished scrapes off the convex portion of the portion 51 to be polished. For this reason, in general, if the depth to push the portion 51 to be polished into the magnetic fluid 30 is insufficient, the processing area becomes small, so that the time spent for polishing the portion 51 to be polished into a desired shape is long. Easy to convert. Therefore, at least the initial polishing of the portion 51 to be polished is performed in a state in which the portion 51 to be polished is pushed into the depth D of 5% or more of the maximum height HM of the magnetic fluid 30 placed on the circumferential surface 111. More preferably, it is 20% or more, and most preferably 50.0% or more.

  6 is an essential part enlarged view of FIG. 3 which is a sectional view taken along line III-III of the polishing apparatus of FIG. 2, and FIG. 7 is an enlarged sectional view of line VII-VII of the polishing apparatus of FIG. As shown in FIG. 7, the maximum height HM indicates the maximum value of the distance in the normal direction of the circumferential surface 111 from the circumferential surface 111 to the surface of the magnetic fluid 30. Further, as shown in FIG. 6, the depth D at which the portion 51 to be polished is pushed in is the distance Hm from the maximum height HM to the portion 51 to be polished from the point 114 defining the maximum height HM. The value obtained by subtracting.

  On the other hand, in the polishing, since the magnetic fluid 30 locally processes the portion 51 to be polished, the entire surface of the portion 51 to be polished is traced (scanned), and in principle, some arch-shaped processing marks remain, which reduces the processing accuracy. Cause. Here, as the depth at which the portion 51 to be polished is pushed into the magnetic fluid 30 increases, the size of the portion 51 to be polished that is locally removed increases, so that the processing marks are likely to remain large. Accordingly, at least the initial polishing of the portion 51 to be polished may be performed in a state where the portion to be polished 51 is pushed to a depth of 65% or less of the maximum height of the magnetic fluid 30 placed on the circumferential surface 111. More preferably, it is 60% or less, and most preferably 55% or less.

  The indentation conditions described above may be adopted at least in the first polishing, and are preferably adopted in the second and subsequent polishing, but may not be adopted. In addition, when the above-described indentation conditions are adopted after the second time, the indentation conditions in each polishing may be common or different from each other.

  Although FIG. 5 shows a mode in which polishing of a portion to be polished is performed twice, the present invention is not limited to this and may be performed three or more times. Specifically, in polishing of a portion to be polished, the ratio of the PV value of the shape error with respect to the design shape after polishing of the portion to be polished to the PV value of the shape error with respect to the design shape before polishing of the portion to be polished is 1/5. It is preferable to repeat until it becomes below, More preferably, it is 1 / 5.3 or less, Most preferably, it is 1 / 5.5 or less. Thereby, sufficient processing accuracy can be secured. The lower limit of the ratio is preferably closer to zero, but may be appropriately set in consideration of the balance with the prolongation of the manufacturing process due to the accompanying increase in the number of polishing times.

  In this specification, the PV value refers to the sum of the distance LM of the highest point and the distance Lm of the lowest point, by measuring the distance in the normal direction from each point of the reference plane BP to the measurement target surface. (See FIG. 5 (a)). Here, the reference plane BP is a plane in which the sum of squares of the distances in the normal direction from the respective points of the measurement target surface is minimized. The PV value is not particularly limited, but can be measured by using a He-Ne laser ring light source / point light source switching type high-precision laser interference type shape measuring device “VeriFire-AT” (manufactured by ZYGO).

  For the same reason, it is preferable that the polishing of the portion to be polished is repeatedly performed until the PV value of the shape error with respect to the design shape after polishing of the portion to be polished is 100 nm PV or less, more preferably 90 nm PV or less, most preferably 80 nm PV or less. Thereby, sufficient processing accuracy can be secured. The lower limit of the PV value is preferably closer to zero, but may be appropriately set in consideration of the balance with the prolongation of the manufacturing process due to the accompanying increase in the number of polishing times.

(Preliminary process)
Next, the preliminary process will be described by taking a method of manufacturing a flat substrate as an example. The preliminary step is a processing step for bringing the object close to the design shape before processing by the magnetic fluid polishing method. However, when manufacturing a substrate having a curved surface, the method is not limited to the method described below, and a process for approaching the design shape may be performed according to a known method before the process by the magnetic fluid polishing method.

  The manufacturing method according to the present invention preferably further includes a step of adjusting the PV value of the shape error with respect to the design shape of the portion to be polished to 700 nm PV or less in advance so that the time spent for polishing the portion to be polished can be shortened. More preferably, it is 690 nmPV or less, Most preferably, it is 680 nmPV or less. Examples of the preliminary process include a processing process, a lapping process, and a grinding process.

  In the processing step, cutting, rotary grinding, or polishing is performed using a cutter, a band saw, an inner peripheral blade, or a grindstone made of diamond or cemented carbide, etc., and processed into a shape close to the final shape.

  In the lapping step, the shape of the object is further approximated to a desired shape, and the entire warp or the like is corrected to flatten the surface. In this step, a double-sided processing machine or a single-sided processing machine is used, and the particle size and the like are adjusted with fixed abrasive grains. However, depending on the case, you may carry out in steps like primary grinding and secondary grinding. As the fixed abrasive grains, those obtained by solidifying particles made of silicon carbide, alumina or the like, or those obtained by solidifying diamond by metal bond, resin bond, vitrified bond, or electrodeposition into pellets are used. Further, chamfering and chamfering may be performed using an NC processing machine or the like before or after the grinding process.

  The grinding process is performed using a single-side processing machine while changing conditions such as the grain size of the fixed abrasive grains. Depending on the case, it is a process for making the shape further desired after performing grinding in stages such as primary grinding and secondary grinding. Only one of the lapping step and the grinding step may be performed, and the order may be changed.

  In the manufacturing method of the present invention, the shape of the portion to be polished is measured every time the portion to be polished is polished, and control for adjusting the relative movement speed of the circumferential surface 111 and the object 50 is performed based on the measurement result. Preferably it is done. For example, it is preferable to measure the shape of the polished portion 51 ′ and perform control based on the measurement result before polishing the polished portion 51 ′ shown in FIG. As a result, it is possible to efficiently manufacture a polished product having a shape approximate to the design shape. For example, among the parts to be polished, high processing speed is achieved by reducing the relative movement speed at locations where the shape error with the design shape is large and increasing the relative movement speed at locations where the shape error with the design shape is small. Polishing time can be shortened while maintaining accuracy.

  In addition, the above control is preferably performed while taking into consideration a desired polishing rate. That is, the polishing rate when a sample made of the same material as the object 50 is polished by the magnetic fluid polishing method under various conditions is measured, and the conditions for obtaining a desired polishing rate may be obtained in advance. It is obvious that the polishing for measuring the polishing rate is not included in the polishing of the portion to be polished.

  Specifically, the polishing apparatus 10 according to the present embodiment includes an NC control device that controls operations of the position adjusting unit 17, the support unit 19, and the wheel 11. Therefore, by inputting a desired set value to this NC control device, the shape of the portion 51 to be polished of the object 50 by a high-precision laser interference type shape measuring instrument (for example, “VeriFire-AT” (manufactured by Zygo)) or the like. The operation control based on the measurement results may be performed. Note that the operation control procedure itself is a well-known technique as described in Patent Document 1, and therefore the description thereof is omitted.

  The shape of the part to be polished is preferably measured before each polishing, and the speed adjustment control is preferably performed in each polishing. However, the present invention is not limited to this. In addition, although the said process is not specifically limited, It is necessary to perform in fundamental grinding | polishing fundamentally.

(Magnetic fluid)
A magnetic fluid is a fluid in which a non-colloidal magnetic substance is dispersed in a carrier, and changes rheological properties (viscosity, elasticity, and plasticity) when placed under a magnetic field. A specific composition may be appropriately set according to a known technique.

Here, as the maximum height of the magnetic fluid 30 on the circumferential surface 111 is larger, the absolute value of a predetermined ratio of the maximum height, which is the depth pushed into the portion 51 to be polished, also increases, resulting in the portion to be polished. The time spent for polishing 51 to a desired shape can be shortened. For this reason, the magnetic fluid preferably has a viscosity coefficient of 30.0 × 10 ⁻³ Pa · s or more, more preferably, so that the maximum height of the magnetic fluid 30 on the circumferential surface 111 can be sufficiently secured. 40.0 × 10 ⁻³ Pa · s or more, most preferably 35.0 × 10 ⁻³ Pa · s or more. The viscosity coefficient mentioned here refers to the viscosity coefficient when the magnetic fluid is placed in a magnetic field (atmosphere that does not actively generate a magnetic field). When the viscosity coefficient is in the above range, the maximum height of the magnetic fluid placed on the circumferential surface of the wheel is usually 1.0 mm to 2.0 mm.

On the other hand, when the viscosity coefficient of the magnetic fluid is excessive, problems such as insufficient recovery of the magnetic fluid by the fluid recovery unit 15 and clogging of the supply pipe 14 and the recovery pipe 16 are likely to occur. For this reason, the magnetic fluid preferably has a viscosity coefficient of 63.0 × 10 ⁻³ Pa · s or less, more preferably 58.0 × 10 ⁻³ Pa · s or less, and most preferably 53.0 × 10 6. ^-3 Pa · s or less.

  The magnetic fluid used in the present invention includes abrasive particles. The abrasive particles preferably have an average particle diameter of 30 μm or less, more preferably 20 μm or less, and most preferably 15 μm or less, in that the surface roughness of the surface 61 of the polishing product 60 to be obtained is easily reduced to a desired value or less. is there.

  On the other hand, if the average particle size of the abrasive particles is too small, the polishing efficiency tends to deteriorate. Therefore, the average particle size of the abrasive particles is preferably 0.5 μm or more, more preferably 3.0 μm or more, and most preferably 5.0 μm or more.

  The abrasive particles may be made of one or more kinds of known materials such as silica, cerium oxide, and diamond, but are preferably made of one or more kinds selected from the group consisting of cerium oxide and diamond from the viewpoint of improving polishing efficiency. . Specifically, diamond paste (D-20, D-10, etc. manufactured by QED Technologies), cerium oxide (C-20, C-10, etc. manufactured by QED Technologies) can be used. In particular, the abrasive particles are more preferably made of diamond from the viewpoint that the error from the design shape and the surface roughness can be easily reduced to a desired value or less.

(Object)
The object is not particularly limited as long as it has a portion to be polished that needs to be polished, and can be selected from materials of any material and shape depending on the desired application. The material may be, for example, metal, glass (including glass ceramics) and the like, and is preferably glass, and glass ceramics is more preferable because scratches due to polishing are less likely to occur. The glass ceramic preferably contains β-quartz (β-SiO ₂ ) and / or β-quartz solid solution (β-SiO ₂ solid solution pair) from the viewpoint of easily obtaining low expansion characteristics. Further, the surface is not limited to the convex surface as shown in FIG. 2, but may be a flat surface as shown in FIG. 8, a concave surface as shown in FIG.

  Especially, the board | substrate manufactured by using a glass plate as a target object has a desired surface characteristic and a low expansion characteristic, and is useful. As the glass plate, an amorphous glass such as Clear Serum (Ohara), Zerodur (Shot), Zerodur-M (Shot), ULE (Corning), or a flat plate made of an extremely low expansion material such as crystallized glass is preferable. .

  A photomask substrate made of such a substrate and a photomask using this photomask substrate are useful in lithography using EUV (ultra-ultraviolet) as exposure light, and are used for ultra-precision / ultra-fine optical components such as semiconductors. Can be used in manufacturing.

Using an ultra-low expansion glass ceramic “Clear Serum-Z” (made by OHARA) having a diameter of 100 mm × thickness of 25 mm as an object, and using an MRF ™ polishing machine “Q22-Y” (made by QED Technologies). And polished. The desired design shape is a plane. The polishing conditions are as shown in Table 1. The magnetic fluid used has a viscosity coefficient of 46.5 × 10 ⁻³ Pa · s, the abrasive particles are made of diamond, have an average particle diameter of 10 μm, and include magnetic particles including abrasive particles on the circumferential surface of the wheel. The maximum height of the fluid was 1.8 mm. Also, before and after each polishing, the surface shape of the object is measured using a high-precision laser interference type shape measuring instrument “VeriFire-AT” (manufactured by Zygo), and an NC controller is used in each polishing based on the measurement result. Control was performed. Table 1 also shows the time spent for polishing.

※押し込み率とは、磁性流体の最大高さに対する、被研磨部位が押し込まれた深さの割合を指す。

* The indentation rate refers to the ratio of the depth at which the part to be polished is indented to the maximum height of the magnetic fluid.

  As shown in Table 1, in Comparative Examples 1 to 6 in which the polishing was performed only once, the PV of the polished material was large and the processing accuracy was low, although a great amount of time was spent for polishing. . On the other hand, in Examples 1-5, although the polishing was performed twice or more, the total time spent for polishing was significantly shorter than that of Comparative Examples 1-6, and PV was also small, and high processing accuracy was obtained. Thus, it was confirmed that by performing polishing of the portion to be polished by the magnetic fluid polishing method twice or more, the processing accuracy can be improved and, as a result, the manufacturing efficiency of the polished product can also be improved.

  The present invention is not limited to the above-described embodiment, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.

It is a fragmentary perspective view of the polish device which can be used with the manufacturing method concerning the present invention. FIG. 2 is a side view of the polishing apparatus of FIG. 1. It is the III-III sectional view taken on the line of the polisher of FIG. It is a principal part enlarged view of FIG. It is a schematic diagram which shows the change of the to-be-polished part of the target object in the manufacturing method which concerns on this invention. It is a principal part enlarged view of FIG. FIG. 7 is an enlarged sectional view taken along line VII-VII of the polishing apparatus in FIG. 2. It is a figure which shows the variation of the shape of the target object which can be used with the manufacturing method which concerns on this invention. It is a figure which shows the variation of the shape of the target object which can be used with the manufacturing method which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Polishing apparatus 11 Wheel 111 Circumferential surface 112 Magnetized part 113 Rotating shaft 13 Fluid supply nozzle 14 Supply pipe 15 Fluid recovery part 16 Recovery pipe 17 Position adjustment part 20 Magnetic force addition part 30 Magnetic fluid 50 Object 51 Polishing part 60 Polishing process 61 surface

Claims (13)

Using a magnetic fluid containing abrasive particles, a polishing process product manufacturing method for polishing a polished portion of an object to manufacture a polishing process product,
A step of polishing the polished portion by moving the circumferential surface and the object relative to each other while the polished portion is in contact with the magnetic fluid placed on the circumferential surface of the wheel that generates magnetic force. Have
A method for producing a polished product, wherein the polished portion is polished twice or more.   The at least first polishing of the portion to be polished is performed in a state where the portion to be polished is pushed to a depth of 5% or more of the maximum height of the magnetic fluid placed on the circumferential surface. Manufacturing method for the above-mentioned polished product.   The at least initial polishing of the portion to be polished is performed in a state where the portion to be polished is pushed to a depth of 65% or less of the maximum height of the magnetic fluid placed on the circumferential surface. 2. A method for producing a polished product according to 2. The said magnetic fluid is a manufacturing method of the polishing processed material in any one of Claim 1 to 3 which has a viscosity coefficient of 30.0 * 10 < ^-3 > Pa * s or more and 63.0 * 10 < ^-3 > Pa * s or less.   5. The method for producing a polished product according to claim 1, wherein the abrasive particles have an average particle diameter of 0.5 μm or more and 30 μm or less.   The method for producing a polished product according to any one of claims 1 to 5, wherein the abrasive particles comprise one or more selected from the group consisting of cerium oxide and diamond.   Until the ratio of the PV value of the shape error with respect to the design shape after polishing of the portion to be polished to the PV value of the shape error with respect to the design shape before polishing of the portion to be polished becomes 1/5 or less, The method for producing a polished product according to any one of claims 1 to 6, wherein the polishing of the part is repeated.   The method for producing a polished product according to any one of claims 1 to 7, wherein the polishing of the portion to be polished is repeated until the PV value of the shape error with respect to the design shape after polishing of the portion to be polished is 100 nm PV or less.   The method for producing a polished product according to any one of claims 1 to 8, further comprising a step of previously adjusting a PV value of a shape error with respect to a design shape of the portion to be polished to 700 nm PV or less.   The shape of the to-be-polished part is measured every time the to-be-polished part is polished, and control for adjusting the relative movement speed of the circumferential surface and the object is performed based on the measurement result. 9. The method for producing a polished product according to any one of 9 above.   The board | substrate manufactured with the manufacturing method in any one of Claim 1 to 10 using a glass plate as said target object.   A photomask substrate comprising the substrate according to claim 11.   A photomask using the photomask substrate according to claim 12.

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